EP4669310A1 - OXIDIZED POLY(3-HEXYLTHIOPHEN) NANOPARTICLES FOR THE TREATMENT OF DEGENERATIVE RETINAL DISEASES - Google Patents

Abstract

The present invention relates to a polymeric nanoparticle having a core@shell structure comprising poly(3-hexylthiophene) in the core and poly(3-hexylthio-phene)-S,S-dioxide in the shell with critical oxidation fraction for use in ameliorating and/or treating degenerative retinal diseases.

Description

.-I .

“Oxidized poly(3-hexylthiophene) nanoparticles for treating degenerative retinal diseases”

DESCRIPTION

Field of the invention

The present invention relates to oxidized core@shell polythiophene based nanoparticles and their use in the treatment of degenerative retinal diseases. Specifically, the organic core@shell nanoparticles are made of poly(3-hexylthiophene) (P3HT) in the core and oxidized poly(3-hexylthiophene) (PTDO) in the shell.

Background of the invention

Degenerative retinal diseases are progressive neurologic disorders caused by genetic mutations and/or environmental or pathologic damage to the retina. Retinal degeneration is a legal cause of incurable low vision and blindness worldwide. Most retinal degenerative diseases are caused by irreversible destruction of retinal neural cells or adjacent supporting tissue. A number of diseases of the retina involve the progressive degeneration and eventual death of the photoreceptors leading inexorably to blindness. Degenerative retinal diseases have a major impact on daily life. From performing basic functions of everyday life to personal independence, the loss of vision affects a wide range of everyday tasks such as reading, shopping, personal care, watching TV, driving a car, etc.

The photoreceptor cells are the light-sensing cells of the retina which upon a sensation of light initiate a cascade of electrical impulses that are sent through the retina and the optic nerve to the brain to create an image. A common aspect of all retinal degenerative diseases is the damage of photoreceptor cells of the retina, which first lose their light sensitivity and eventually get lost. The most common retinal degenerative diseases are age-related macular degeneration (AMD), retinitis pigmentosa, diabetic retinopathy, glaucoma, retinal detachment or macular hole. Symptoms of all these diseases are usually blurred or distorted vision, loss of night and side vision, and progressive loss of vision. Retinitis pigmentosa is a collective name for a set of genetic disorders that cause the death of rods and secondarily of cones. Both cell types are the photosensitive cells of the photoreceptors of the retina. The atrophic form of AMD affects about

I .4-20% of the population aged between 70 and 90 years worldwide. There have been attempts to treat these diseases with drugs, but so far most promising are approaches of gene supplementation, optogenetic or stem cell therapies. There have also been attempts to rescue vision by electrically stimulating the preserved inner retinal circuits with epiretinal, subretinal or suprachoroidal prosthetic implants (Scholl, H. P. et al. Emerging therapies for inherited retinal degeneration, Sci. Transl. Med. 8, 368rv6 (2016); Benfenati, F. & Lanzani, G. New technologies for developing second generation retinal prostheses. Lab Anim. 47, 71-75 (2018); Bloch, E., Luo, Y. & da Cruz, L. Advances in retinal prosthesis systems, Ther. Adv. Ophthalmol. 11 , 1-19 (2019); Dagnelie, G. et al. Performance of real- world functional vision tasks by blind subjects improves after implantation with the Argus® II retinal prosthesis system. Clin. Exp. Ophthalmol. 45, 152-159 (2017); Stingl, K. et al. Artificial vision with wirelessly powered subretinal electronic implant alpha-IMS. Proc. Biol. Sci. 280, 20130077 (2013); Lorach, H. et al. Photovoltaic restoration of sight with high visual acuity, Nat. Med. 21 , 476-482 (2015)). Organic semiconductors have been introduced as interfaces for neuronal stimulation in retinal prosthesis (Manfredi, G., Colombo, E., Barsotti, J., Benfenati, F. & Lanzani, G., Photochemistry of organic retinal prostheses. Anna. Rev. Phys. Chem. 70, 99-121 (2019); Rivnay, J., Wang, H., Fenno, L., Deis- seroth, K. & Malliaras, G. G., Next-generation probes, particles, and proteins for neural interfacing. Sci., Adv. 3, e1601649 (2017); Tian, B. et al. Roadmap on semiconductor-cell biointerfaces. Phys. Biol. 15, 031002 (2018); Maya-Vetencourt,

J. F. etal. A fully organic retinal prosthesis restores vision in a rat model of degenerative blindness. Nat. Mater. 16, 681-689 (2017)).

So far, there are no corresponding commercially available products.

In Maya-Vetencourt et al., Subretinally injected semiconducting polymer nanoparticles (NPs) rescue vision in a rat model of retinal dystrophy, Nature Nanotechnology (2020), https://doi.org/10.1038/s41655-020-0696-3, it has been shown that conjugated polythiophene based NPs, i.e., P3HT-NPs, mediate light- evoked stimulation of retinal neurons and persistently rescue visional functions when subretinally injected in a rat model of retinitis pigmentosa. P3HT-NPs spread out over the entire subretinal space and promote light-dependent activation of spared inner retinal neurons, recovering subcortical, cortical and behavioural visual responses in the absence of trophic effects or retinal inflammation. However, due to the limited visual acuity of the animal model, no conclusive recommendations are given except that working as non-genetic light actuators for neuronal activation, P3HT-NPs have a high potential for biomedical applications in degenerative retinal diseases and, possibly, in central nervous system diseases.

Hence, there is a need for providing means for ameliorating or treating degenerative retinal diseases that are easy to apply and well tolerated by the patient. One area of improvement regards the stimulation efficiency of the NPs upon light absorption. According to the present understanding, the interface coupling mechanism consists in the photo-induced electrical polarization and subsequent capacitive coupling of the NPs in tight “gigaseal” contact with the neuronal membrane. The action is driven by the electrical charging of the interface. This invention aims at improving this process and thus enhancing the photo-stimulation efficiency but introducing an acceptor layer in the outer shell of the NPs that acts as a negative charge sink. A second object regards the stability of the nanoparticle suspension, which can be improved by the core-shell structure supporting a higher zeta-po- tential (-40±2.6 mV compared to -32±1 .8 mV for the non-oxidized ones).

Summary of the invention

The present invention is based on the finding that organic thiophene-based core@shell nanoparticles made of poly(3-hexylthiophene) (P3HT) in the core and oxidized poly(3-hexylthiophene) (PTDO) chains in the shell are effective in photostimulation of inner retinal neurons and constitute a promising tool for biomedical applications in the context of neuronal stimulation and neuroprosthesis and, in particular, in the treatment of degenerative retinal diseases.

The invention relates to a polymeric nanoparticle having a core@shell structure comprising poly(3-hexylthiophene) in the core and oxidized poly(3-hexylthio- phene) (PTDO) (also referred to in the following as in the shell for use as a medicament and, in particular, for use in ameliorating and/or treating neurodegener- ative retinal diseases.

The present invention also relates to a pharmaceutical formulation comprising the polymeric nanoparticles having a core@shell structure comprising poly(3-hex- ylthiophene) in the core and oxidized poly(3-hexylthiophene) (PTDO), which is preferably a formulation for the subretinal injection.

The present invention further relates to a process for the preparation of polymeric nanoparticle having a core@shell structure comprising poly(3-hexylthiophene) in the core and oxidized poly(3-hexylthiophene) (PTDO) the comprising the postfunctionalization of a preformed colloidal suspension of poly(3-hexylthiophene) nanoparticles by the use of Rozen’s reagent.

The present invention further relates to a method for the treatment or improvement of degenerative retinal diseases comprising the step of administrating to a patient in need thereof of a pharmaceutically effective quantity of polymeric nanoparticles having a core@shell structure comprising polythiophene in the core and oxidized polythiophene in the shell.

Detailed description of the invention

Conjugated polymers have long been an attractive class of functional materials thanks to their interesting tunable optoelectronic and mechanical properties including their flexibility. So far, they have found applications in organic photovol- taics, chemical sensing, and biology. poly(3-hexylthiophene) (here below referred to as P3HT) is one of the most popular members of the said class and is becoming a recognized benchmark in the organic optoelectronic framework. The carbon-based structure of P3HT, differently from inorganic materials, is an asset for bio-applications as it allows creating soft structures capable of interfacing seamlessly with living matter (G. Lanzani, Nat. Mater. 2014, 13, 775). Indeed, P3HT thin films were successfully used to trigger photo-responsive signals in primary neuronal networks, astrocytes and other cell types (D. Ghezzi, M. R. An- tognazza, M. Dal Maschio, E. Lanzarini, F. Benfenati, G. Lanzani, Nat. Commun. 2011 , 2, 166; V. Benfenati, N. Martino, M. R. Antognazza, A. Pistone, S. Toffanin, S. Ferroni, G. Lanzani, M. Muccini, Adv. Healthc. Mater. 2014, 3, 392; a) J. Hopkins, L. Travaglini, A. Lauto, T. Cramer, B. Fraboni, J. Seidel, D. Mawad, Adv. Mater. Technol. 2019, 4, 1800744; b) M. Zangoli, F. Di Maria, E. Zucchetti, C. Bossio, M.R. Antognazza, G. Lanzani, R. Mazzaro, F. Corticelli, M. Baroncini, G. Barbarella, Nanoscale 2017, 9, 9202; c) I. E. Palama, F. Di Maria, M. Zangoli, S. D'Amone, G. Manfredi, J. Barsotti, G. Lanzani, L. Ortolani, E. Salatelli, G. Gigli, G. Barbarella, RSC Adv. 2019, 9, 23036). As outlined above, pristine poly(3-hex- ylthiophene) nanoparticles (P3HT NPs) have recently been tested as low-invasive phototransducers, showing their basic ability to restore vision in blind rats suffering from photoreceptor degeneration.

Recently, the present inventors reported that the use of Rozen’s reagent, a powerful oxygen transfer agent [S. Rozen, Acc. Chem. Res. 1998, 21, 307] enables the post-functionalization of colloidal suspensions of P3HT-NPs by transforming thiophene units into thiophene-S,S-dioxide (TDO) ones, thus leading to the formation of a shell of n-type polymeric chains (namely, PTDO) on the P3HT-NPs surface [F. Di Maria, A. Zanelli, A. Liscio, A. Kovtun, E. Salatelli, R. Mazzaro, V. Morandi, G. Bergamini, A. Shaffer, S. Rozen, ACS Nano 2017, 1 1 , 1991 -1999]. This chemical methodology allows the synthesis of all-organic core@shell nanostructures (P3HT@PTDO), in which acceptor (PTDO present on the shell) and donor (P3HT present in the core) materials are in intimate contact and spatially localized in a single nanoarchitecture. These NPs are useful in photovoltaic devices. They have not been proposed for biological applications, let alone for the treatment of degenerative retinal diseases. According to the present invention, the electronic and excitation processes taking place in various P3HT@PTDO NPs have been investigated. Specifically, the electron and energy transfer characteristics, with a particular emphasis on the kinetics of the electronic processes, have been investigated. P3HT@PTDO NPs have been prepared by treating water-suspended P3HT NPs with increasing amounts of Rozen’s reagent, according to the above document Di Maria et al., yielding NPs with various oxidation degrees. Scanning electron microscopy (SEM) and dynamic light scattering (DLS), provided information on the morphology and size of the generated NPs. These P3HT@PTDO NPs were subretinally administered in light-insensitive degenerate retina explants from Royal College of Surgeons rats, an experimental model of Retinitis pigmentosa, and it was found that these NPs can effectively photo-stimulate inner retinal neurons. Their phototransduction efficiency proved to be better than that elicited by non-oxidized P3HT-NPs, possibly because of the stronger and longer-lived charge separation induced by the nanoscale core@shell architecture.

A particularly favorable phototransduction efficacy was found with polymeric NPs having a ratio of P3HT and P3HT-S,S-dioxide from 1 :10 to 10:1.

Hence, the present invention regards the finding of a critical oxidizing fraction above which the NPs display improved photostimulation of inner retinal neurons.

According to the present invention, a “core@shell nanoparticle” refers to a nanoparticle comprising an inner core structure and an outer shell, wherein the core structure and the outer shell are made of different components.

The object is a polymeric nanoparticle having a core@shell structure comprising P3HT in the core and P3HT-S,S-dioxide on the shell for use as a medicament for ameliorating and/or treating degenerative retinal diseases. In a specific and preferred embodiment the ratio of P3HT and P3HT-S,S-dioxide is from 10:1 to 1 :10, preferably from 7:1 and 4:1. In a preferred embodiment, each of the polymeric nanoparticles of the invention has a diameter from about 50 nm to about 500 nm.

Basically, the polymeric NPs for the use of the invention can be prepared by any method that is suitable in the art and by use of any oxygenation agent such as for example HOF-CHaCN, H2O2, sodium persulfate, m-chloroperoxybenzoic acid, peracetic acid etc.

Preferably, the polymeric NPs for the use of the invention are prepared by postfunctionalization of a pre-formed colloidal suspension of P3HT-NPs by the use of Rozen’s reagent. Rozen’s reagent is a solution of hypofluorous acid in water/ acetonitrile and allows an oxygen transfer under very mild reaction conditions. The preparation of the NPs is essential as disclosed in the above document by Di Maria et al. The process allows the production of different types of oxidized thiophene based core@shell NPs, with different ratios of pristine vs oxidized thiophene moieties. Firstly, the polymerization of opportunely functionalized thio- phenic building blocks (R=alkyl, aryl side chain) allows to selectively engineer the chemical-physical properties of the polymer employed for the preparation of polythiophene bases NPs (PT-NPs) (e.g., energy gap, absorption spectral range, fluorescence etc.). Secondly, the chemoselective and controlled oxidation of the shell of PT-NPs (/.e., the oxygenation of the thiophene sulfur atom) by the addition of variable amounts of an oxygen donor agent, allows to regulate the amount of TDO units in the shell thus enabling a fine-tuning of the charge separation in PT@PTDO NPs.

The NPs for the use according to the present invention are round and have a core@shell structure. By its name, core@shell particles are a class of particles which contain a core and a shell. The core and the shell can be different materials or the same materials with different structures. In the NPs for the use according to the invention, the core comprises P3HT and the shell comprises oxidized poly(3-hexylthiophene), i.e. P3HT-S,S-dioxide. Furthermore, being this procedure able to selectively oxygenate the sulfur atom of thiophene ring, any thiophene based polymer able to form NPs can be post-functionalized into a core@shell nanostructrure.

The polymeric NPs for the use of the invention will be administered subretinally to establish contacts with and photoactivate second-order retinal neurons (bipolar cells and horizontal cells).

The polymeric NPs for the use of the invention can be formulated as a composition for subretinal injection. Corresponding injection solutions are known in the art or are available on the market. The injection of the polymeric NPs may be carried out by a suitable injection device known to a person skilled in the art and available on the market.

The NPs for the use of the present invention can be used for the wide variety of retinal dystrophies in which photoreceptors degenerate, irrespective of the stage of the disease.

The invention discloses a method for the treatment or improvement of degenerative retinal diseases comprising the step of administrating to a patient in need thereof a pharmaceutically effective quantity of polymeric nanoparticles having a core@shell structure comprising polythiophene in the core and oxidized polythiophene in the shell.

In particular, said polythiophene polymer is represented by poly(3-hexylthio- phene).

In particular, said oxidized polythiophene is represented by poly(3-hexylthio- phene)-S,S-dioxide.

In the method of the invention, the ratio of poly(3-hexylthiophene) and poly(3- hexylthiophene)-S,S-dioxide is from about 1 :10 to 10:1 , preferably from about 7:1 and 4:1. In the method of the invention, each of said polymeric nanoparticle has a diameter from about 50 nm to about 500 nm.

The method of the invention is directed to degenerative retinal disease selected from the group comprising the age-related macular degeneration and retinitis pigmentosa.

For the method of the invention, the polymeric nanoparticles are prepared by a process comprising the post-functionalization of a preformed colloidal suspension of poly(3-hexylthiophene) nanoparticles by the use of Rozen’s reagent.

Explanation of the figures

The following figures explain the subject-matter of the present invention.

Figure 1 : a) Topographic images of the P3HT@PTDOx NPs deposited on Si substrates, taken by AFM operated in tapping mode, “x” expresses the equivalent of oxidant used to create the NPs oxidized shell. 1 ) x = 0 Z range 270 nm, 2) x = 0.50 Z range 325 nm, 3) x =1 .00 Z range 250 nm, 4) x =1 .50 Z range 285 nm, 5) Fully oxidized NPs Z range 170 nm. Corresponding surface potential images were taken by the KPFM: T) x = 0 Z range 70 mV, 2’) x = 0.50 Z range 99 mV, 3’) x =1 .00 Z range 60 mV, 4’) x =1 .50 Z range 60 mV, 5’) Fully oxidized NPs Z range 60 mV. Scale bars, 1 pm for all images, b) SEM image of a single NPs of the oxidized sample with x = 0.5. Scale bar, 200 nm. c) Schematic of the kinetic model showing the different NP morphology contributions. d,e) Work functions values of P3HT and PTDO NPs.

Figure 2: a) Steady-state normalized photoluminescence for all the NPs shell oxidations. x expresses the equivalent of oxidant used to create the NPs oxidized shell. Inset: steady-state normalized absorption, b) Schematic of energetic level distribution and relative kinetic, c) Normalized TRPL kinetics for all the shell oxidations, integrated from 560 to 780 nm. The arrow shows the quenching trend towards high oxidation, d) Normalized TRPL kinetics of x=0 (lines) and x=1.5 (lines + circles) shell oxidations integrated from 560 to 620 nm (red), 620 to 680 nm (blue), and 680 to 780 nm (yellow). Decay associated spectra (DAS) obtained from TRPL global analysis for the extremal oxidation values (x = 0 and x = 1.5) for the e) amorphous (AmP) and the f) aggregated (AgP) phases.

Figure 3: Picosecond-resolved transient absorption map for the external shell oxidation for a) non-oxidized NPs, x = 0 and b) max shell oxidation NPs, x = 1.5. Inset: log-scale visualization. Transient absorption spectra at different times for c) x = 0 and d) x = 1 .5 samples. Decay-associated spectra (DAS) obtained from global analysis for samples e) x = 0 and f) x = 1 .5). Time evolution of the transient absorption signal at three wavelengths for g) x = 0 and h) x = 1 .5 samples.

Figure 4: Nanosecond transient absorption spectra at different times for a) x = 0 and b) x = 1 .5 samples. Decay-associated spectra (DAS) obtained from global analysis for samples c) x = 0 and d) x = 1 .5). Time evolution of the transient absorption signal at three different wavelengths for e) x = 0 and f) x = 1 .5 samples.

Figure 5: Electrophysiological extracellular recordings from blind retinas explants obtained from 1 -year-old Royal College of Surgeons (RCS) rats, a widely accepted model of Retinitis pigmentosa bearing loss-of-function mutation in the Mertk gene, responsible for human forms of the disease). Retinal explants are subretinally injected with oxidized NPs mimicking the in vivo administration, a) Schematic representation of the experimental setup showing the explanted tissue layered on a MEA illuminated by light (top), and a representative trace showing the light-mediated firing modulation (bottom), b) The firing modulation efficacy shows a higher percentage of neurons with a statistically significant light-induced firing modulation in retinas treated with oxidized P3HT-NPs compared with Ctrl untreated tissues, c) The dose-response of the firing rate versus light stimulus intensity normalized to the baseline firing in the dark depicts a significant effect of oxidized P3HT-NPs starting at 7 mW/mm² (500 ms pulses @ 0.25 Hz, Ctrl n = 188, 194, 228 and P3HT@PTDOi.s n = 124, 125, 144 neurons from 4 animals for 1 , 7 and 18 mW/mm² respectively), d) Comparison between the firing modulation of blind retinas treated with P3HT-NPs compared with oxidized P3HT-NPs reveals a stronger effect of the latter at different light power densities. The comparison considers only neurons with a statistically significant modulation of the firing activity upon illumination for both groups (P3HT n = 35, 55, 1 12 and P3HT@PTDOi.s n = 14, 21 , 53 neurons from at least 4 animals for 1 , 7 and 18 mW/mm² respectively). Statistical analysis has been performed using the Agostino-Pearson’s normality test and the Mann-Whitney (/-test (** p<0.01 , *** p<0.001 ).

Examples

The following examples explain the subject matter of the present invention.

Material and methods

Sample preparation: Oxidized core@shell NPs are prepared by post-functionali- zation of pre-formed polythiophene based NPs (PT-NPs), such poly-3-hexylthio- phene NPs (P3HT-NPs) or its derivatives, with an oxygen transfer reagent, such as HOF-CHaCN, H2O2, sodium persulfate, m-chloroperoxybenzoic acid, peracetic acid etc, capable of oxidizing the thiophene aromatic sulfur atoms.

Sample preparation: P3HT@PTD0x NPs, where x indicates the concentration of the acid used to oxidize the NPs surface and create the shell were prepared according to the above reference Di Maria et al. by directly oxidizing the water suspensions of P3HT NPs with increasing amounts of HOF’CHsCN (Rozen’s reagent, with x equals to 0.25, 0.5, 1 , 1.25 and 1.5 equivalents for thiophene). The suspensions were stirred at room temperature for 15 minutes and then dialyzed against water. Pristine PTDO NPs, employed as a comparison with P3HT and core@shell NPs, were prepared by first oxidizing the P3HT in CH2CI2 with 1 eq of HOF’CHsCN, and then nanoprecipitating the resulting polymer from THF in water.

Absorbance: UV-Vis absorption spectra were acquired by means of a Perkin Elmer Lambda 1050 spectrophotometer used in transmission configuration. The spectrophotometer is equipped with a Deuterium and a Tungsten Lamp. Spectra were acquired in the wavelength range 350-800 nm with a step size of 2 nm. Each absorbance spectrum was corrected removing the water and cuvette contribution.

Steady-State Fluorescence: Fluorescence spectra were acquired by means of a HORIBA iHR320 spectrofluorometer, using a 450 W intense broadband continuous wave xenon lamp for sample excitation. All spectra were acquired in emission mode in the wavelength range 600-825 nm, with an excitation wavelength of 561 nm. The slit aperture was 3 nm for the emission and 5 nm for the excitation beam. The internal grating used had a groove density of 1200 gr/mm and a Blaze wavelength of 500 nm.

Dynamic Light Scattering (DLS) and Scanning Electron Microscopy (SEM): NPs Z-average and Polydispertion Index (PDI), were measured using DLS by means of a Zetasizer Nano ZS by Malvern Panatycal. SEM images were taken by means of a Tescan MIRA3 High-RES SEM. Both Secondary Electron and Back Scattered Electrons images were acquired using an electron beam at a voltage of 5/10 kV, with a magnification of about 350000 x and currents in the pA range. SEM samples were prepared drop-casting about 100 pl of NPs water dispersion (WD) on silicon p-doped substrates previously treated by oxygen plasma cleaning to promote surface wettability and fixed with carbon tape to improve conductivity.

Atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM): AFM and KPFM measurements were performed with a commercial microscope Multimode 8 (Bruker) operated in air, employing Pt/lr-coated cantilever doped-silicon tips (SCM-PIT-V2, Bruker), with mechanical constant k = 3 N/m and oscillating frequency fo ~ 75 kHz. AFM and KPFM images are acquired by the two-passage technique: firstly, a topographic line scan is performed in the tapping mode, and then that same line is rescanned at a lift height = 30 nm, using the amplitude modulation (AM) mode. KPFM provides a map of the surface potential (SP), i.e, the difference between the sample and tip work functions, through the relation: SP = WFsampie - WFtip. The NPs films were realized by drop casting from a solution onto doped Silicon surfaces immediately after ultrasonic cleaning in acetone/iso- propanol and plasma cleaning. For AFM/KPFM measurements we analyzed the thinner part of the film, where no aggregates or clusters were visible at the optical microscopes.

Macroscopic Kelvin Probe: The work function values were investigated for both pristine P3HT NPs and PTDO NPs films (made of only pristine P3HT and PTDO NPs, respectively) were determined by means of macroscopic Kelvin probe measurements, performed under ambient conditions using a 2 mm diameter gold tip amplifier (Ambient Kelvin Probe Package from KP Technology Ltd.). The technique enables the measurement of the surface potential on a sampled surface area of about 3 mm². Calibration of the probe was performed with a reference freshly cleaved HOPG (WF = 4.65 eV). The thick films for WF measurement were obtained by drop casting from NPs solutions on similar Si substrates used for AFM and KPFM. In this case, we placed the KP probe on top of the thicker regions.

Time-resolved photoluminescence measurements: Time-resolved photoluminescence measurements were performed using a tunable femtosecond Tksapphire laser source (Chameleon Ultra II, Coherent, U.S.A.) operating at 80 MHz repetition rate and width of -150 fs. The wavelength of the laser source is tuned to 1040 nm, and the beam is focused onto a 1 mm thick beta barium borate (BBO) nonlinear crystal for the generation of second-harmonic pulses at 520 nm, which is used for the excitation of the samples. The emission signals were collected using a 550 nm long pass filter and analyzed by a spectrograph (Princeton Instruments Acton SP2300) coupled to a streak camera (Hamamatsu C5680, Japan) equipped with a synchroscan voltage sweep module. In these measurements, the fluorescence intensity was obtained as a function of both wavelength and time with spectral and temporal resolutions of ~1 nm and ~3 ps, respectively. Temporal broadening of the pump pulses due to dispersive elements was observed to be well below the response time of the detection system. Transient absorption experimental setup: The femtosecond transient absorption (TA) setup is fed by Tksapphire laser system (Libra, Coherent) that provides 100- fs pulses with a central wavelength of 800 nm at 2 kHz repetition rate. The pump pulses can be generated either by frequency doubling the fundamental to create 400 nm pulses, or by using a home-made optical parametric amplifier (OPA) and are modulated using a mechanical chopper. The probe consists of a white-light continuum (WLC), generated by tightly focusing the 800 nm beam on a 2 mm thick Sapphire plate. The measurements are performed in transmission using a SP2150 Acton, Princeton Instruments spectrometer equipped with a CCD detector (Stresing Buro). Magic angle relative polarization between pump and probe beams (54.7°) was used in all TA experiments, and the pump fluence was kept below the bimolecular recombination threshold. The nanosecond TA setup employs the same probe and detection as the femtosecond setup, but the 700 ps pump pulses are generated a Nd-YAG laser (Picolo - InnoLas). For the experiments reported here the second and third harmonics were used, at wavelengths of 532 nm and 355 nm. The Picolo is triggered externally using a reference from the Tksapphire amplified laser system, producing a train of pulses at 1 kHz. We performed TA using a ns pump laser and a digital electronic delay generator coupled to the fs TA setup. Since the electronic delay generation is much faster than the mechanical one, much higher signal to noise levels can be achieved for similar data acquisition times, allowing us to measure the weak signals on long timescales (here, from ns to ps).

MultiElectrode Array (MEA) recordings on retina explants. Degenerated retinas together with the choroid were dissected from the enucleated eyes of 12 to 14 months-old dystrophic RCS rats. Each retina was divided into four pieces that were perfused with carbo-oxygenated Ames medium. Retinas were subjected to the subretinal injection of NPs and positioned RGC-side down onto 60-electrode MEA chip using the MEA1060-inv-BC system (Multi Channel Systems). Light- evoked extracellular activity was obtained with a fiber-coupled Lumencor LED system (Spectra X) peaking at 530 nm fed to an inverted Nikon Eclipse Ti microscope. The illumination spot covered an area of about 1 mm² with a power density ranging from 1 to 18 mW/mm². Light intensity was measured using a power meter ThorLabs PM100D and converted into power density given the area of the illumination spot. MC-Rack recordings and Spectra X stimulations were synchronized by the Stimulus Generator STG4008 (MCS GmbH). Illumination pulses of 500 ms were administered at 0.25 Hz to obtain 25 sweeps. Data were acquired at 20 kHz and filtered between 100 Hz and 3 kHz. Spike detection and sorting were performed using MC Rack software (Multi Channel Systems). To distinguish action potentials from background noise (~15 pV, peak-to-peak), we arbitrarily chose a threshold of detection equal to 4.5 times the SD of the signal (automatically calculated by the acquisition system for each electrode). Light-evoked firing activity was assessed by selecting those RGCs displaying a modulation of firing that was time-locked to the light stimulus with respect to the baseline (spontaneous activity).

Example 1 : Characterization of core@shell P3HT NPs

We investigated the size distribution and stability of the different NPs suspensions by means of DLS and zeta potential measurements. We found that the increase in the degree of oxidation results in an approximately constant diameter and progressive increase of zeta potential (Table 1 ), which is indicative of a rise in the electrostatic repulsion between particles (see a) M. Zangoli, F. Di Maria, View 2021 , 2, 20200086; b) Electrostatic Repulsion and Colloid Stability. T. Tadros in Encyclopedia of Colloid and Interface Science (EDS T. Tadros). Springer, Berlin, Heidelberg 2013).

Table 1. Size and zeta potential of the different P3HT@PTDO NPs.

NPs Size (nm) C-pot (mV)

P3HT 177 ± 26 -32.1 ± 1.8

P3HT@PTDOo.25 177 ± 27 -36.0 ± 2.5

P3HT@PTDOO.5 182 ± 28 -36.9 ± 2.6

P3HT@PTDOi 174 ± 26 -37.8 ± 2.6

P3HT@PTDOi.25 178 ± 22 -38.4 ± 1.8 P3HT@PTDOI.5 171 ± 29 -40.4 ± 2.6

Electrochemical cyclic voltammetry confirmed that P3HT@PTDOi.s NPs present the largest amount of TDO units, indeed the ratio between the oxidation and reduction currents becomes roughly 4:1 , unlike those oxidized with 1 equivalent of HOF which is close to 7:1

We investigated morphological and surface properties of core@shell NPs by KPFM. This technique allows measuring the work function and surface potential distribution of nanomaterials, thus revealing different electrical properties between the core and the shell in fully organic NPs (see A. Liscio, V. Palermo, P. Samori, Acc. Chem. Res. 2010, 43, 541 ). Figure 1a shows the NP topography (panels 1 -5) and the corresponding surface potential maps (panel 1 ’-5’) obtained by atomic force microscopy (AFM) and KPFM, respectively at increasing degrees of oxidation. The NP morphology was not significantly affected by the oxidation degree, as quasi-spherical particles with diameters of a few hundred nanometers are present in all samples (see F. Di Maria, et al., cited above), as shown by the representative SEM image of Figure 1 b. On the contrary, the surface potential images present significant differences arising from the different oxidation degrees of the nanomaterial. Both pristine P3HT (Figure 1a (T)) and P3HT@PTDOx (x = 0.25, 1 , Figure 1a (2’, 3’)) NPs display similar surface potential values which are lower than the surrounding substrate, as evidenced by their darker color. Differently, in P3HT@PTDOI.5 NPS (Figure 1a (4’)) we observed a central core bordered by a brighter contour, indicating a higher surface potential. As a consequence, the surface work function is reduced compared to the NPs core. In other words, the NP surface Fermi level is closer to the vacuum, as typically observed in n-type semiconducting materials. (Figure 1a (4’)) (see a) M. Zangoli, M. Gaz- zano, F. Monti, L. Maini, D. Gentili, A. Liscio, A. Zanelli, E. Salatelli, G. Gigli, M. Baroncini, F. Di Maria, ACS Appt. Mater. Interfaces 2019, 11, 16864; b) F. Di Maria, M. Zangoli, M. Gazzano, E. Fabiano, D. Gentili, A. Zanelli, A. Fermi, G. Bergamini, D. Bonifazi, A. Perinot, M. Caironi, R. Mazzaro, V. Morandi, G. Gigli, A. Liscio, G. Barbarella, Adv. Fund Mater. 2018, 28, 1801946). It is worth noticing that contours are enhanced along the fast-scan direction of the microscope due to a correlation with the NP topography. However, the shell remains clearly and systematically observable around all sides of the NPs, regardless of the experimental scanning parameters adopted. These proofs make us confident that the lowering work function of the shell is intrinsic to the P3HT@PTDOI.5 NPS. In addition, to closely compare the surface potential features of P3HT@PTDO NPs with those of homogenously oxidized NPs (PDTO NPs), we also investigated NPs prepared from PDTO polymer. Analogously to P3HT NPs, pristine PTDO NPs do not show a core@shell structure and are characterized by a broader size distribution (Figure 1a (5,5’)). PTDO NPs display a higher surface potential, appearing brighter than the substrate, as observed for the shell present in P3HT@PTDOi.s NPs.

These results confirm that P3HT NPs treated with Rozen’s reagent are characterized by a core@shell structure. As suggested by optical and electrochemical measurements, this geometry is common to all P3HT@PTDOx particles, but it can be directly visualized via KPFM only in NPs samples with a high degree of oxidation, where the number of TDO units in the outer layer becomes large enough to originate a detectable signal. Although these measurements do not allow to infer quantitative information about the actual sizes of core and shell, these KPFM measurements are the first direct evidence of an entirely organic core@shell nanostructure. In Figure 1c we report a schematic of the morphological and kinetic model we adopted for the core@shell system: HOMO-LUMO energy levels are derived from the electrochemical analysis, work function (WF) values for the pristine and oxidized parts by means of macroscopic Kelvin Probe on the film of the corresponding NPs. Oxidized units present lower WF values (- 4.5 ± 0.1 eV for PTDO NPs vs -5.0 ± 0.1 eV for P3HT NPs), consistent with an increase of the electron character of the material after oxidation. 2: CW PL and absorbance

We report steady-state PL spectra in Figure 2a, corrected by the absorbance maxima (see inset) of each sample to account for differences in original concentrations. The spectra revealed a clear trend that we associate with the quenching of emission due to the increasing oxidation level of the NP surface. The ratio between the intensity of the peaks at around 660 and 700 nm is decreasing as the oxidation level increases, until reaching almost the same contribution for the highest oxidation levels, corresponding to the P3HT@PTDOi.25 and P3HT@PTDOI.5 samples. We also observed a slight red shift of the spectra with higher oxidation levels. We note that the absorbance spectra (inset of Figure 2a) present very similar absorbance profiles for all the oxidation levels, showing only minor differences on the shoulder at long wavelengths. This is consistent with the expectation that absorption takes place mostly in the NP core, in agreement with our previous work (see F. Di Maria, et al., cited above).

To investigate the photophysics of the NPs, we performed TRPL measurements and global analysis for all the oxidation levels (see SI for the complete data set). It is known that P3HT NPs, similarly to P3HT films (see J. Clark, J. F. Chang, F. C. Spano, R. H. Friend, C. Silva, Appl. Phys. Lett., 2009, 94, 3) can include amorphous (AmP) and aggregate (AgP) phases, with the electronic transitions of the latter being red-shifted with respect to the former, as shown in Figure 2b. The TRPL experiments employed photoexcitation at 520 nm, which is absorbed by both the AmP and the AgP as a consequence of the spectral overlap of both phases at short wavelengths (see I. Bargigia, E. Zucchetti, A. R. S. Kandada, M. Moreira, C. Bossio, W. P. D. Wong, P. B. Miranda, P. Decuzzi, C. Soci, C. D'Andrea, G. Lanzani, ChemBioChem 2019, 20, 532). In both phases, the excited state deactivation involves radiative and non-radiative paths. However, while the energy in the AgP can only decay to the ground state or relax onto the oxidized shell (k_c), the AmP excited state can also relax to the AgP, which has lower energy. Figure 2c shows the TRPL kinetics integrated over the entire spectral range. The PL lifetime is reduced as the oxidative level increases, suggesting the appearance of a new decay channel associated with the oxidized shell. This could originate from either charge transfer or energy transfer towards non-emitting states in the shell. Figure 2d shows the TRPL kinetics for the non-oxidized (x = 0, lines) and the most oxidized (x = 1 .5, lines + circles) samples, integrated over three spectral regions, 560 - 620 nm (blue), expected to be mostly covering the AmP; 620 - 680 nm (yellow), with contribution from both AmP and AgP and the low energy tail 680 - 780 nm (red) sampling AgP. For each sample, moving toward the red, PL decay slows down. This suggests the presence of radiative centers with a smaller energy gap and longer lifetime, likely populated by spectral migration (see I. Bargigia, E. Zucchetti, A. R. S. Kandada, M. Moreira, C. Bossio, W. P. D. Wong, P. B. Miranda, P. Decuzzi, C. Soci, C. D'Andrea, G. Lanzani, ChemBioChem 2019, 20, 532 and a) G. C. Faria, D. J. Coutinho, H. von Seggern, R. M. Faria, Org. Electron. 2017, 57, 298; b) G. Volonakis, L. Tsetseris, S. Logothetidis, Phys. Chem. Chem. Phys. 2014, 16, 25557). Furthermore, we note that particularly in the 620-680 and 680-780 nm ranges, the oxidized sample shows much faster relaxation kinetics than its non-oxidized counterpart, as if the radiative centers were the most affected by the oxidative shell.

Using global analysis, the TRPL data that cover a time window up to 120 ps, can be adequately fit with fast (T < 10 ps) and slow (T >50 ps) components for all samples. The corresponding decay-associated spectra (DAS) of x = 0 and x = 1 .5 NPs are shown in Figure 2e for the fast component and in Figure 2f for the slow one. The fast DAS components shown in Figure 2e are similar between each other and blue-shifted compared to the slow DAS components shown in Figure 2f, a trend that was reproduced across all samples (see SI). Hence, we can assign the fast component (Figure 2e) to AmP deactivation and the second one to AgP relaxation (Figure 2f).

Table 2. Lifetime obtained from global analysis of TRPL data, for the AmP (TI) and AgP (12).

Interestingly, Table 2 shows that there is a clear “accelerating” trend in the decay kinetics assigned to the AgP upon increasing degrees of oxidation. The faster PL decay highlights the presence of additional deactivation paths or acceleration of the existing decay rate, yet the origin of the phenomenon cannot be further characterized. For instance, both energy transfer and charge transfer towards the shell would lead to a faster decay of PL.

To further investigate the quenching mechanism, we performed transient absorption (TA) spectroscopy in two different time ranges: from fs to ns and from ns to ps.

Example 4: Transient absorption (fs-ns)

We report the TA map (in differential transmission units: AT/T) for non-oxidized (x = 0) and maximum oxidation (x = 1 .50) NPs, in Figure 3a and 3b, respectively. Photoexcitation was performed using 100 fs pulses at 400 nm, with fluence kept below 1 pJ/cm² to avoid bimolecular recombination (see J. Piris, T. E. Dykstra, A. A. Bakulin, P. H. M. van Loosdrecht, W. Knulst, M. T. Trinh, J. M. Sehins, L. D. A. Siebbeles, J. Phys. Chem. C 2009, 113, 14500). TA spectra show positive bands due to stimulated emission (SE) and ground-state bleaching (GSB), and weak negative bands due to photoinduced absorption (PIA). Figure 3c shows a series of representative TA spectra (horizontal cuts of Figure 3a) for the nonoxidized P3HT NPs. The spectral lineshape shows a vibronic progression, with the separation between the peaks at 620, 570 and 525 nm matching the 1450 cm^-1 frequency of the strongest Raman mode of P3HT (C=C) (see L. Brambilla, C. C. Ferron, M. Tommasini, K. Hong, J. T. Lopez Navarrete,V. Hernandez, G. Zerbi, J. Raman Spectrosc. 2018, 49, 569). At early times, a distinct SE signal below the absorption onset (700-750 nm) is also present.

Figure 3e shows the DAS of the four exponential components required to fit the data. The 3 ps component (red) consists of a well-defined vibronic progression in the GSB region, with the lowest GSB peak found at approximately 610 nm, possibly including SE at the optical gap (0-0 transition) in the AmP, while at a longer wavelength SE peak roughly at 690 nm, possibly due to SE in the AgP. Taking into account the spectral match with the early time DAS of the TRPL data in Figure 2e, we assign this initial fast component to an energy transfer from the AmP to the AgP. Note that charge transfer would not lead to fast decay of the whole GSB band. The difference in timescale with respect to the TRPL global fit is likely due to the temporal resolution of the TRPL experiments (close to the 3 ps lifetime), making its extraction less reliable than in TA with 100 fs time resolution.

Recovery of GSB proceeds according to non-exponential kinetics, here reproduced by three time-components (30 ps, 213 ps and >1 ns) that is typical of disordered systems. The dynamic is possibly due to both structural phases in the particles. The relative intensity of the spectral features changes slightly with time, according to the faster decay of SE. The decay is not simply associated with a single species, as photoexcitation leads to the generation of singlet state, triplet states and polaron-pairs all contributing to GSB (see a) O. G. Reid, R. D. Pensack, Y. Song, G. D. Scholes, G. Rumbles, Chem. Mater. 2014, 26, 561 ; b) N. Gasparini, F. V. A. Camargo, S. Fruhwald, T. Nagahara, A. Classen, S. Roland, A. Wadsworth, V. G. Gregoriou, C. L Chochos, D. Neher, M. Salvador,

D. Baran, I. McCulloch, A. Gorling, L. Luer, G. Cerullo, C. J Brabec, Nat. Commun. 2021 , 12, 1 ).

Data regarding the maximally oxidized sample are shown in Figures 3b,d,f,h. In this case, besides the possible energy transfer from the AmP to the AgP, charge or energy transfer to interfacial states in the oxidized shell may take place. Qualitatively, the spectra in Figures 3c and 3d are similar, yet the oxidized sample has a faster decay. The fastest component in Figure 3f (0.9 ps, red) can once again be assigned to energy transfer between AmP and AgP, in analogy with the dynamics in the non-oxidized sample. Interestingly, we note that this 0.9 ps DAS (red curve, Figure 3f) does not show amplitude in the SE region, suggesting that the SE of AmP and AgP is more similar than for the non-oxidized sample. The subsequent decay is again non-exponential, with components of 7 and 83 ps, once again on a faster timescale than for the non-oxidized sample. To better highlight the effect of the oxidized shell, we also report the decay kinetics in Figure 3g and 3h at three representative wavelengths ascribed respectively to the AmP (blue), coexistence of both AmP and AgP (yellow) and AgP (red). Since both PL decay and GSB recovery show the same trend, we conclude that the oxidized sample has an additional decay path. Since the TA signal includes a decay in both SE and GSB components (Figures 3d,f), we can ascribe it to energy transfer to the shell, as charge transfer would preserve the GSB signatures.

Longer time kinetics, from ns to ps, are summarized in Figure 4. For both samples, we observe a bi-exponential relaxation, with only a negligible amount of signal being left at the end of the experimental temporal window. The non-oxidized sample lifetimes are 7.7 and 90 ns, while those of the maximally oxidized samples are 7.2 and 75 ns. The spectrum from the non-oxidized sample shows a quasi-isosbestic point around 660 nm and a clear PA above that wavelength that is typically assigned to polaron pairs. In the oxidized sample there is hardly any change in sign. Possibly long-lived charges in the oxidized sample are located in the shell, where GSB spectrally overlaps with PA.

It is worth noticing that, due to experimental constraints, the different measurements are performed using pump at different wavelengths (and energies): 400 nm, 355 nm and 532 nm for the fs-TA, ps-TA and TRPL, respectively. As a consequence, we could have a distinct configuration of starting population of the Am and Ag phases, determining a different relative contribution of each transition, favoring one with respect to the other. Example 5: Oxidized core@shell NPs are effective in the photostimulation of retinal neurons

To study the ability of core@shell P3HT-NPs of stimulating neural activity modulation, we extracellularly recorded the light-evoked firing activity of retinal ganglion cells (RGCs) in retinal explants from 12-14 months-old dystrophic RCS rats, an experimental model of Retinitis Pigmentosa (see a) A. Gal, Y. Li, D.A. Thompson, J. Weir, U. Orth, S.G. Jacobson, E. Apfelstedt-Sylla, D. Vollrath, Nat Genet 2000, 26, 270; b) M. M. LaVail, B. A. Battelle. Exp Eye Res 1975, 21, 167). For recordings, retina explants containing the choroid were placed with the RGC layer in contact with MEA electrodes (epiretinal recording) with the NPs devices microinjected in the subretinal space, between the choroid and the retina, in place of the dead photoreceptors (Figure 5a) (see J. F. Maya-Vetencourt, G. Manfredi, M. Mete, E. Colombo, M. Bramini, S. Di Marco, D. Shmal, G. Mantero, M. Dipalo, A. Rocchi, M. L. DiFrancesco, E. D. Papaleo, A. Russo, J. Barsotti, C. Eleftheriou,

F. Di Maria, V. Cossu, F. Piazza, L. Emionite, F. Ticconi, C. Marini, G. Sambuceti,

G. Pertile, G. Lanzani, F. Benfenati, Nat. Nanotechnol. 2020, 15, 698 and M. L. Di Francesco, E. Colombo, E. D. Papaleo, J. F. Maya-Vetencourt, G. Manfredi, G. Lanzani, F. Benfenati, Carbon 2020, 162, 308). In the absence of the external photoreceptor layer, the microinjected NPs contact the bipolar cells present in the outer plexiform layer and inner nuclear layer (INL) that are not affected by degeneration. Under this subretinal configuration, the stimulating light passes through the RGC layer first, recapitulating the physiological pathway of visual stimulation that reaches the outer retina after crossing the inner retina layers. No significant light-dependent effect on firing was present in control samples up to the maximum power density tested (18 mW/mm²), consistent with the total blindness of the fully degenerate RCS retinas used in the experiments (Figure 5 b,c). Notably, the presence of core@shell NPs in the subretinal space markedly increased the percentage of RGCs with a statistically significant firing modulation (Figure 5b) and brought about evoked RGC firing that was time-locked to the stimulus, highly significant already at 7 mW/mm² and further increased at higher power (Figure 5c). We have previously shown that non-oxidized P3HT-NPs were able to induce a light-dependent increase of RGC firing in retinal explants an effect that was subsequently confirmed after in vivo implantation in the dystrophic RCS rat (see J. F. Maya-Vetencourt, G. Manfredi, M. Mete, E. Colombo, M. Bramini, S. Di Marco, D. Shmal, G. Mantero, M. Dipalo, A. Rocchi, M. L. DiFrancesco, E. D. Papaleo, A. Russo, J. Barsotti, C. Eleftheriou, F. Di Maria, V. Cossu, F. Piazza, L. Emionite, F. Ticconi, C. Marini, G. Sambuceti, G. Pertile, G. Lanzani, F. Benfenati, Nat. Nanotechnol. 2020, 15, 698). Thus, we compared the efficiency of RGC photostimulation by core@shell NPs with that triggered by the previously described non-oxidized P3HT-NPs under the same experimental conditions. Interestingly, while both NP populations were active in triggering light induced RGC firing, core@shell NPs displayed a significantly increased performance at both 7 and 18 mW/mm², indicating a higher sensitivity and more efficient energy conversion (Figure 5d).

The above experiments show that core@shell NPs made of poly(3-hexylthio- phene), which were oxidized by Rozen’s reagent, display unique properties, in particular as regards their size, the zeta potential and the absorption spectra, which properties account for a favorable effect in terms of photostimulation of retinal neurons. Figure 5 shows the particularly favorable effect of core@shell NPs having a P3HT:PTDO ratio of 1 .5 in terms of efficiency of RGC photostimulation. These particles displayed a significantly increased performance at both 7 and 18 mW/mm² indicating a higher sensitivity and more efficient energy conversion.

We report that core@shell NPs, made of P3HT in the core and PTDO in the shell, exhibit a faster deactivation rate of the excited state and a reduced emission intensity compared to pristine P3HT-NPs. According to spectroscopic data, the most likely origin of both phenomena is an energy transfer occurring from the core to the oxidized shell. This brings about a different spatial localization of the excitation energy in the oxidized vs non-oxidized materials, with a prevalence of the surface states in the former. In addition, once surface states are excited, they could decay into polaron-pairs thus locating charges at the surface. A clear long- lived GSB in the oxidized sample was not detected, excluding surface polaron being more stable than those in the bulk. However, photobleach (PB) spectra might contain some subtle hint of the presence of those charges. PB reaches 700 nm in the presence of the oxidized shell, while it turns into photoinduced absorption (PA) above 650 nm in the non-oxidized sample (as it does in most P3HT samples). It is possible that polarons located in the shell are associated with a PB signal that covers the PA. Furthermore, we note that the full recovery of the TA signal after 1 jis indicates that any surviving population to longer time scale, if existing, should account for less than 10’³ of the initial population. This is relevant for biological applications that most likely occur in the ms time scale. Indeed, core@shell NPs evoked light-triggered responses in blind degenerated retinas that were superior to those triggered by non-oxidized P3HT-NPs. In conclusion, thiophene based core@shell NPs represent highly effective photon nanotransducers that advance our understanding of the coupling mechanism at the bio- tic/abiotic interface. Additionally, they may pave the way to potential biomedical applications in the context of neuronal stimulation and neuroprostheses.

Claims

1. Polymeric nanoparticles having a core@shell structure comprising polythiophene in the core and oxidized polythiophene in the shell, for use as a medicament.

2. The polymeric nanoparticles having a core@shell structure comprising polythiophene in the core and oxidized polythiophene in the shell according to the preceding claim for use as a medicament in ameliorating and/or treating degenerative retinal diseases.

3. The polymeric nanoparticles having a core@shell structure comprising polythiophene in the core and oxidized polythiophene in the shell according to any one of the preceding claims for use as a medicament, wherein said polythiophene polymer is represented by poly(3-hexylthiophene).

4. The polymeric nanoparticles having a core@shell structure comprising polythiophene in the core and oxidized polythiophene in the shell according to any one of the preceding claims for use as a medicament, wherein said oxidized polythiophene is represented by poly(3-hexylthiophene)-S,S-dioxide.

5. The polymeric nanoparticles having a core@shell structure comprising polythiophene in the core and oxidized polythiophene in the shell according to the preceding claim for use as a medicament, wherein the ratio of poly(3-hexylthio- phene) and poly(3-hexylthiophene)-S,S-dioxide is from about 1 :10 to 10:1 , preferably from about 7:1 and 4:1 .

6. The polymeric nanoparticles having a core@shell structure comprising polythiophene in the core and oxidized polythiophene in the shell according to any one of the preceding claims for use as a medicament, wherein each of said polymeric nanoparticle has a diameter from about 50 nm to about 500 nm.

7. The polymeric nanoparticles having a core@shell structure comprising polythiophene in the core and oxidized polythiophene in the shell for use as a medicament according any one of the preceding claims from 2 to 6, wherein said degenerative retinal disease is selected from the group comprising the age-related macular degeneration and retinitis pigmentosa.

8. The polymeric nanoparticles having a core@shell structure comprising polythiophene in the core and oxidized polythiophene in the shell for use as a medicament according any one of the preceding claims, wherein said polymeric nanoparticles are prepared by a process comprising the post-functionalization of a preformed colloidal suspension of poly(3-hexylthiophene) nanoparticles by the use of Rozen’s reagent.

9. A pharmaceutical formulation comprising the polymeric nanoparticles for use as a medicament according any one of the preceding claims.

10. The pharmaceutical formulation according to the preceding claim, wherein the polymeric nanoparticles are formulated as a formulation for subretinal injection.

11. A method for the treatment or improvement of degenerative retinal diseases comprising the step of administrating to a patient in need thereof of a pharmaceutically effective quantity of polymeric nanoparticles having a core@shell structure comprising polythiophene in the core and oxidized polythiophene in the shell.

12. The method for the treatment or improvement of degenerative retinal diseases according to the preceding claim, wherein said polythiophene polymer is represented by poly(3-hexylthiophene).

13. The method for the treatment or improvement of degenerative retinal diseases according to the preceding claim 1 1 , wherein said oxidized polythiophene is represented by poly(3-hexylthiophene)-S,S-dioxide.

14. The method for the treatment or improvement of degenerative retinal diseases according to the preceding claim 1 1 , wherein the ratio of poly(3- hexylthiophene) and poly(3-hexylthiophene)-S,S-dioxide is from about 1 :10 to 10:1 , preferably from about 7:1 and 4:1 .

15. The method for the treatment or improvement of degenerative retinal diseases according to the preceding claim 11 , wherein each of said polymeric na- noparticle has a diameter from about 50 nm to about 500 nm.

16. The method for the treatment or improvement of degenerative retinal diseases according to the preceding claim 1 1 , wherein said degenerative retinal disease is selected from the group comprising the age-related macular degeneration and retinitis pigmentosa.

17. The method for the treatment or improvement of degenerative retinal diseases according to the preceding claim 1 1 , wherein said polymeric nanoparticles are prepared by a process comprising the post-functionalization of a preformed colloidal suspension of poly(3-hexylthiophene) nanoparticles by the use of Ro- zen’s reagent.