WO2011046288A2 - Icg doped silica nanoparticles for biological imaging and preparation method thereof - Google Patents
Icg doped silica nanoparticles for biological imaging and preparation method thereof Download PDFInfo
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- WO2011046288A2 WO2011046288A2 PCT/KR2010/004750 KR2010004750W WO2011046288A2 WO 2011046288 A2 WO2011046288 A2 WO 2011046288A2 KR 2010004750 W KR2010004750 W KR 2010004750W WO 2011046288 A2 WO2011046288 A2 WO 2011046288A2
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims abstract description 197
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- MOFVSTNWEDAEEK-UHFFFAOYSA-M indocyanine green Chemical compound [Na+].[O-]S(=O)(=O)CCCCN1C2=CC=C3C=CC=CC3=C2C(C)(C)C1=CC=CC=CC=CC1=[N+](CCCCS([O-])(=O)=O)C2=CC=C(C=CC=C3)C3=C2C1(C)C MOFVSTNWEDAEEK-UHFFFAOYSA-M 0.000 claims abstract description 117
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82B—NANOSTRUCTURES FORMED BY MANIPULATION OF INDIVIDUAL ATOMS, MOLECULES, OR LIMITED COLLECTIONS OF ATOMS OR MOLECULES AS DISCRETE UNITS; MANUFACTURE OR TREATMENT THEREOF
- B82B1/00—Nanostructures formed by manipulation of individual atoms or molecules, or limited collections of atoms or molecules as discrete units
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
- A61K49/00—Preparations for testing in vivo
- A61K49/001—Preparation for luminescence or biological staining
- A61K49/0013—Luminescence
- A61K49/0017—Fluorescence in vivo
- A61K49/0019—Fluorescence in vivo characterised by the fluorescent group, e.g. oligomeric, polymeric or dendritic molecules
- A61K49/0021—Fluorescence in vivo characterised by the fluorescent group, e.g. oligomeric, polymeric or dendritic molecules the fluorescent group being a small organic molecule
- A61K49/0032—Methine dyes, e.g. cyanine dyes
- A61K49/0034—Indocyanine green, i.e. ICG, cardiogreen
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
- A61K49/00—Preparations for testing in vivo
- A61K49/001—Preparation for luminescence or biological staining
- A61K49/0063—Preparation for luminescence or biological staining characterised by a special physical or galenical form, e.g. emulsions, microspheres
- A61K49/0069—Preparation for luminescence or biological staining characterised by a special physical or galenical form, e.g. emulsions, microspheres the agent being in a particular physical galenical form
- A61K49/0089—Particulate, powder, adsorbate, bead, sphere
- A61K49/0091—Microparticle, microcapsule, microbubble, microsphere, microbead, i.e. having a size or diameter higher or equal to 1 micrometer
- A61K49/0093—Nanoparticle, nanocapsule, nanobubble, nanosphere, nanobead, i.e. having a size or diameter smaller than 1 micrometer, e.g. polymeric nanoparticle
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82B—NANOSTRUCTURES FORMED BY MANIPULATION OF INDIVIDUAL ATOMS, MOLECULES, OR LIMITED COLLECTIONS OF ATOMS OR MOLECULES AS DISCRETE UNITS; MANUFACTURE OR TREATMENT THEREOF
- B82B3/00—Manufacture or treatment of nanostructures by manipulation of individual atoms or molecules, or limited collections of atoms or molecules as discrete units
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09B—ORGANIC DYES OR CLOSELY-RELATED COMPOUNDS FOR PRODUCING DYES, e.g. PIGMENTS; MORDANTS; LAKES
- C09B23/00—Methine or polymethine dyes, e.g. cyanine dyes
- C09B23/02—Methine or polymethine dyes, e.g. cyanine dyes the polymethine chain containing an odd number of >CH- or >C[alkyl]- groups
- C09B23/08—Methine or polymethine dyes, e.g. cyanine dyes the polymethine chain containing an odd number of >CH- or >C[alkyl]- groups more than three >CH- groups, e.g. polycarbocyanines
- C09B23/086—Methine or polymethine dyes, e.g. cyanine dyes the polymethine chain containing an odd number of >CH- or >C[alkyl]- groups more than three >CH- groups, e.g. polycarbocyanines more than five >CH- groups
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09B—ORGANIC DYES OR CLOSELY-RELATED COMPOUNDS FOR PRODUCING DYES, e.g. PIGMENTS; MORDANTS; LAKES
- C09B69/00—Dyes not provided for by a single group of this subclass
- C09B69/008—Dyes containing a substituent, which contains a silicium atom
Definitions
- the present invention relates to indocyanine green (ICG)-doped silica nanoparticles and a preparation method thereof, and more particularly to ICG-doped silica nanoparticles and a preparation method thereof, in which a cationic additive is used to dope silica nanoparticles with ICG in a more stable manner and to increase the fluorescence intensity and stability of the nanoparticles.
- ICG indocyanine green
- NIR fluorescence agents have provided an important tool for bio-imaging and the detection of disease markers in vivo .
- the relatively large penetration depth of NIR light in most biological media offers the potential for imaging deep into the organs and soft tissues of living systems without damaging (Cheong, W. et. al., IEEE Journal of Quantum Electronics, 1990. 26 (12): p. 2166-2185).
- NIR fluorescence absorption bands can be sufficiently removed from the intrinsic fluorescence of most biological tissues and scatter of the glass service or solvent, thereby suppressing the background noise (Anderson, R. and J. Parrish, Journal of Investigative Dermatology, 1981. 77 (1): p. 13-19).
- ICG indocyanine green
- aqueous ICG has a low fluorescence quantum yield and nonspecific quenching (Benson, R. and H. Kues, Physics in Medicine and Biology, 1978. 23 (1): p. 159-163).
- An aqueous ICG solution is unstable, as the compound undergoes thermal degradation and photo-degradation. It has been reported to be unstable in physiologically relevant solutions, such as water, salt solution, plasma, and blood.
- the ICG shows decreased absorption and reduced fluorescence, because oxidation and dimerization degrade the original molecule (Vishal Saxena, M.S. and Jun Shao, Journal of Pharmaceutical Sciences, 2003. 92 (10): p. 2090-2097).
- NPs fluorophore doped silica nanoparticles
- the silica matrix not only protects the dye but also provides some unique features. For example, it is a biocompatible substance and extremely stable in an adverse environment.
- inorganic and organic dye-doped silica nanoparticles have been developed (Santra, S. et al., Journal of Biomedical Optics, 2001. 6 : p. 160; Yan, J.
- the ICG dye could not be encapsulated directly into silica to form silica fluorescent nanoparticles for electrostatic repulsion between the negatively charged ICG dye and the negatively charged silica matrix.
- ICG demonstrates improved optical stability.
- these carriers suffered significant leakage with 78% ICG loss within 8 hr in physiological conditions.
- a silica-polymer composite microcapsule was developed to improve encapsulated ICG retention (17% ICG leakage after 8 hr at 37 °C), but the addition of the nanoparticulate shell increased the particle size to 0.4 ⁇ m to 1.0 ⁇ m.
- Silica nanoparticles can avoid dye leakage and photobleaching more effectively. The method makes it easy to control the size of nanoparticles at the nano level.
- the present inventors have made efforts to develop ICG dye-doped silica nanoparticles as a new type of NIR dye delivery material.
- the presentinventors have succeeded in preparing ICG-doped silica nanoparticles by conjugating indocyanine green (ICG)with polyethyleneimine (PEI) or the like as a core and successfully entrapping the PEI-conjugated ICG into a silica matrix by the Stober method, and have found that the prepared nanoparticles show high sensitivity and low leakage, thereby completing the present invention.
- ICG indocyanine green
- PEI polyethyleneimine
- Another object of the present invention is to provide a method for preparing said nanoparticles.
- the present invention provides silica nanoparticles doped with indocyanine green (ICG) conjugated with a positively charged molecule such as polyethylenimine (PEI), aminopropyl trimethoxysilane or bovine serum albumin, in which the ICG-doped silica nanoparticles can be used as a near-infrared fluorescent nanoprobe for biological imaging.
- ICG indocyanine green
- PEI polyethylenimine
- aminopropyl trimethoxysilane or bovine serum albumin a positively charged molecule
- the ICG-doped silica nanoparticles can be used as a near-infrared fluorescent nanoprobe for biological imaging.
- the present invention provides a method for preparing silica nanoparticles doped with ICG conjugated with a positively charged molecule, the method comprising the steps of: i) conjugating ICG with a positively charged molecule as a core; and incorporating the positively charged molecule-conjugated ICG into silica nanoparticles.
- the positively charged molecule used in the method of the present invention is a polymer, silica nanoparticles having stronger fluorescence intensity can be obtained.
- the ICG-doped silica nanoparticles synthesized according to the method of the present invention has advantages in that the size thereof is easily controlled at the nano level and in that they can be surface-modified via versatile routes and have low leakage, low toxicity, low photo bleaching, high sensitivity enough to apply for in vitro and in vivo imaging, and sustained stability.
- FIG. 1 shows the structural formula of indocyanine green (ICG) used in the present invention.
- FIG. 2 schematically shows the photobleaching of an ICG dye in silica nanoparticles.
- FIG. 3 is a graphic diagram showing the photobleaching of an ICG dye in silica nanoparticles.
- FIG. 4 is a graphic diagram showing dye leakage from silica nanoparticles.
- FIG. 5 is a TEM image of synthesized nanoparticles.
- FIG. 6 shows the absorbance and fluorescence spectra of nanoparticles.
- FIG. 7 is a set of graphs showing the fluorescence intensity of nanoparticles including the polymer polyethyleneimine(the left side graph) and the fluorescence intensity of nanoparticles including low-molecular-weight aminopropyl trimethoxysilane.
- FIG. 8 shows images of fluorescence penetrations at various thicknesses of pork.
- the present invention provides silica nanoparticles doped with indocyanine green (ICG) conjugated with a positively charged molecule, such as polyethylenimine, aminopropyl trimethoxysilane or bovine serum albumin, which can be used as a near-infrared fluorescence nanoprobe for biological imaging.
- ICG indocyanine green
- the positively charged molecule is preferably PEI.
- the presentinvention provides a method for preparing silica nanoparticles doped with ICG conjugated with a positively charged molecule, the method comprising the stepsof: i) conjugating ICG with a positively charged molecule as a core; and ii) incorporating the positively charged molecule-conjugated ICG into silica nanoparticles.
- the positively charged molecule is preferably selected from the group consisting of PEI, aminopropyl trimethoxysilane and bovine serum albumin. More preferably, the positively charged molecule is PEI.
- silica nanoparticles can have increased fluorescence intensity.
- the silica nanoparticles used in step (ii) are preferably produced by hydrolysis of tetraethyl orthosilicate (TEOS).
- Near-infrared light has a high penetration depth in the body compared to visible light and has less effect on the interference of scattered light, and thus it is highly useful for bio-imaging studies.
- Various near-infrared dyes have been developed, and particularly indocyanine green (ICG) was approved by the US FDA and is being used in clinical surgery.
- ICG indocyanine green
- the negatively charged indocyanine green has a problem in that it is not entrapped inside negatively charged silica nanoparticles due to repulsion with the silica nanoparticles.
- a method of adding a positively charged molecule to a dye solution was used.
- the positively charged molecule may be selected from the group consisting from the group consisting of low-molecular-weight aminopropyl trimethoxysilane, the positively charged polymer polyethyleneimine and the protein bovine serum albumin.
- the positively charged molecule was used to prepare nanoparticles doped with indocyanine green.
- the present inventors have designed ICG dye-doped silica nanoparticles as a new type of NIR dye delivery material.
- the ICG dye is successfully entrapped inside the silica matrix, and the sensitivity of ICG dye-doped silica nanoparticles is improved.
- PEI has a positively charged amine group, and ICG has a negative charge. For this reason, in order to successfully entrap ICG inside the silica matrix, ICG is first conjugated with polyethylenimine(PEI) as a core.
- ICG-doped nanoparticles are prepared using the PEI-conjugated ICG as a core and a silica, produced by hydrolysis of tetraethyl orthosilicate (TEOS), as a shell, by the Stober method (Stober, W. and A. Fink, Bohn, (1968) Controlled growth of monodisperse silica spheres in the micron size range.
- Colloid Interface Sci. 26 p. 62:69; Wang, L. and W. Tan, Multicolor FRET silica nanoparticles by single wavelength excitation. Nano letters, 2006. 6 (1): p. 84).
- ICG is a weak fluorophore having a low quantum yield of only 1.3% in an aqueous solvent, because it has complicated solution behavior due to its amphiphilic nature (hydrophilic sulfate groups and hydrophobic dimethylated benzoindotricarbocyanin groups) (see FIG. 1). It forms aggregates in water depending on its concentration. According to the design of the present inventors, the ICG dye is held by each amine group on the polymer chains, which force the ICG molecules to aggregate with each other, so this kind of structure reduces the self quenching.
- the PEI-conjugated ICG is a very large molecule, so it reduces the dye leakage.
- the present invention describes the successful synthesis of PEI-conjugated ICG-doped silica nanoparticles, the size of which is easily controlled at the nano level and which can be surface-modified via versatile routesand have low leakage, low toxicity, low photo bleaching and high sensitivity enough to apply for in vitro and in vivo imaging.
- the cationic additive functions not only to entrap the dye molecule inside the silica nanoparticles, but also increase the fluorescence intensity of the nanoparticles. If the concentration of the dye in the nanoparticles is excessively high, the dye will absorb the fluorescence of the surrounding molecules,or the light scattering will be increased, leading to a decrease in fluorescence intensity. Wiesner introduced the core-shell concept, and according to the present invention, when the polymer additive is added to the dye molecules, the dye molecules are dispersed in the nanoparticles, and thus the fluorescent signal is increased.
- the present inventors prepared PEI-conjugated ICG-doped silica nanoparticles and ICG-doped silica nanoparticles.
- ICG was conjugated with an ethylenimine polymer as a core, and APTS and a PEI solution were added to the ICG/DMSO solution to link the ICG to the PEI and the APTS, thereby covalently conjugating the ICG-PEI to silica nanoparticles.
- an ammonium hydroxide solution was added to the mixture to cause an activation reaction.
- ICG-doped silica nanoparticles were synthesized by the Stober method in the same manner as described above, except that the core consisted only of ICG.
- ICG has two polycyclic parts imparting a lipophilic property to the molecule, and a sulfate group bound to each polycyclic part and imparting property to the molecule. ICG cannot be doped into the silica nanoparticles because of the repulsion between the negatively chargedsulfate group of ICG and the negatively charged silica matrix in the neutral pH range.
- the negatively charged sulfate group of ICG can be conjugated with the positively charged amine group of APTS, and then it can be doped into silica nanoparticles by the Stober method.
- ICG forms aggregates in water depending on its concentration. Since ICG has a low quantum yield in an aqueous solvent, the ICG-doped silica nanoparticles emit a too weak signal, and thus it is difficult to perform in vivo imaging using the ICG-doped silica nanoparticles .
- the core structure having PEI conjugated to ICG forces the ICG molecules to aggregate with each other and increases the signal intensity by about 2 times.
- the PEI-conjugated ICG-doped silica nanoparticles can be used as a near-infrared fluorescent nanoprobe for biological imaging (see FIG. 2).
- the present inventors investigated the photostability of the ICG-PEI-doped silica nanoparticles in an aqueous phase.
- the ICG-PEI-doped nanoparticles showed a little photobleaching and high light emission intensity compared to the nanoparticles doped only with the ICG dye. This is because the photostability of the ICG dye was increased in the process of conjugating ICG with the PEI polymer and doping the PEI-conjugated ICG into the silica matrix (see FIG. 3).
- the leakage of the ICG dye from the silica nanoparticles with the change in the fluorescence intensity of a solution of the nanoparticles was measured.
- the emission intensity of the ICGdye-doped silica nanoparticles was maintained at 78% of the original emission intensity, and the emission intensity of the ICG-PEI-doped nanoparticles was maintained at 90% of the original emission strength (see FIG. 4).
- ICG Indocyanine green
- APTS 3-(aminopropyl)triethoxysilane
- PBS phosphate buffered saline
- PEI Polyethylenimine
- TEOS Tetraethyl orthosilicate
- 29 wt% aqueous solution of ammonia were purchased from Aldrich (Milwaukee, WI).
- ICG-doped silica nanoparticles were synthesized using the Stober method (Stober, W. and A. Fink, Bohn, (1968) Controlled growth of monodisperse silica spheres in the micron size range. Colloid Interface Sci. 26 : p. 62:69; Wang, L. and W. Tan, Multicolor FRET silica nanoparticles by single wavelength excitation. Nano letters, 2006. 6 (1): p. 84).
- ICG was conjugated with an ethyleneimine polymer as a core.
- the stirred mixture was centrifuged at 13,800 rpm for 30minutes to separate the silica nanoparticles from unreacted silica compounds.
- the separated silica nanoparticles were washed twice with ethanol and several times with PBS.
- the resulting product was redispersed in PBS and stored in a dark place at 4 °C for future use.Meanwhile, ICG-doped silica nanoparticles were also synthesized using the Stober method in the same manner as described above, except that the core of the nanoparticles consisted only of ICG.
- the shape of the nanoparticles prepared in Example 2 was examined under a transmission electron microscope (H-7600, Hitachi, Tokyo, Japan). The size of the nanoparticles was measured by the image J. The fluorescence intensity of the nanoparticles was determined by a Varioskan Flash spectral scanning multimode reader (Thermo Fisher Scientific NYSE: TMO). The excitation wavelength used in all the studies was 789 nm.
- ICG has a complex molecular structure, which has two polycyclic parts imparting a lipophilic property to the molecule and a sulfate group bound to each polycyclic part and imparting a hydrophilic property to the molecule.
- ICG shows solubility in various organic solvents such as DMSO, methanol, acetonitrile, etc.
- ICG could not be doped into silica nanoparticles because of the repulsion between the negatively charged sulfate group of ICG and the negatively charged silica matrix in the neutral pH range.
- the negatively charged sulfate group of ICG can be conjugated with the positively charged amine group of APTS, and then ICG can be doped into silica nanoparticles by the Stober method.
- ICG forms aggregates in water depending on its concentration. Since ICG has a low quantum yield in an aqueous solvent, the ICG-doped silica nanoparticles emit a too weak signal, and thus it is difficult to perform in vivo imaging using the ICG-doped silica nanoparticles .
- the present inventors designed a core structure in which PEI was conjugated to ICG through electrostatic interaction. This kind of structure forces the ICG molecules to aggregate with each other and increases the signal intensity of the nanoparticles by about two times.
- the PEI-conjugated ICG-doped silica nanoparticles provide enough sensitivity to be used as a near-infrared fluorescent nanoprobe for biological imaging (see FIG. 2).
- a solution of 2 mg/ml ICG in DMSO and a solution of 5 mg/ml ICG-PEI-doped nanoparticles in PBS buffer were prepared.
- the samples were excited at 790 nm, and the emission wavelength was recorded at 820 nm 7 times at 90-min intervals with a Varian Carey Eclipse Fluorescence Spectrophotometer.
- the solutions were exposed to UV light.
- the present inventors investigated the photostability of the ICG-PEI-doped silica nanoparticles in an aqueous phase.
- the ICG dye-doped nanoparticles showed a little photobleaching, and the emission intensity thereof decreased to about 87.8%. However, the intensity of pure dye decreased to about 15.6%.
- the dye-doped silica nanoparticles improve the stability of the ICG dye.
- the ICG-PEI-doped nanoparticles showed a little photobleaching, and the emission intensity thereof decreased to about 93.7%.
- Such results demonstrate that the photostability of the ICG dye was increased when ICG was conjugated with the PEI polymer and doped into the silica matrix (see FIG. 3).
- the leakage of ICG dye from the silica nanoparticles with the change in the fluorescence intensity of a solution of the nanoparticles was measured.
- 10 mg of the nanoparticles were dispersed in 2 ml of PBS buffer.
- the nanoparticle sample was centrifuged at 13,800 rpm for 15 minutes, redispersed in 2 ml of PBS buffer and stored in a dark place at room temperature.
- the nanoparticles were washed for one week, and then the total fluorescence intensity of the ICG dye in the nanoparticles was measured at 24-hour intervals.
- the emission intensity of the ICG dye-doped silica nanoparticles was maintained at 78% of the original emission intensity, and the emission intensity of the ICG-PEI nanoparticles was maintained at 90% of the original emission intensity (FIG. 4).
- the silica nanoparticles can effectively prevent dye leakage and that the PEI which isa long-chain polymer can more effectively prevent dye leakage.
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Abstract
The present invention relates to indocyanine green (ICG)-doped silica nanoparticles, which can be used as a near-infrared fluorescent nanoprobe for biological imaging, and a preparation method thereof. More specifically, the invention relates to silica nanoparticles doped with ICG conjugated with a positively charged molecule such as polyethylenimine (PEI), aminopropyl trimethoxysilane or bovine serum albumin, and a preparation method thereof comprising the steps of: conjugating ICG with a positively charged molecule as a core; and incorporating the positively charged molecule-conjugated into silica nanoparticles. The ICG-doped silica nanoparticles synthesized according to the preparation method of the invention has advantages in that the size thereof is easily controlled at the nano level and in that they can be surface-modified via versatile routes and have low leakage, low toxicity, low photo bleaching, high sensitivity enough to apply for in vitro and in vivo imaging, and sustained stability.
Description
The present invention relates to indocyanine green (ICG)-doped silica nanoparticles and a preparation method thereof, and more particularly to ICG-doped silica nanoparticles and a preparation method thereof, in which a cationic additive is used to dope silica nanoparticles with ICG in a more stable manner and to increase the fluorescence intensity and stability of the nanoparticles.
Near-infrared (NIR) fluorescence agents have provided an important tool for bio-imaging and the detection of disease markers in vivo. The relatively large penetration depth of NIR light in most biological media offers the potential for imaging deep into the organs and soft tissues of living systems without damaging (Cheong, W. et. al., IEEE Journal of Quantum Electronics, 1990. 26(12): p. 2166-2185). In biological applications, NIR fluorescence absorption bands can be sufficiently removed from the intrinsic fluorescence of most biological tissues and scatter of the glass service or solvent, thereby suppressing the background noise (Anderson, R. and J. Parrish, Journal of Investigative Dermatology, 1981. 77(1): p. 13-19). As a biomarker which requires long circulation half-life, targetability, accumulation at the tumor sites and prolonged stay at the site of action, an injectable ICG dye with low toxicity (Taichman Gc Fau - Hendry et. al., The use of cardio-green for intraoperative visualization of the coronary circulation: evaluation of myocardial toxicity. (0730-2347 (Print)) would be of great interest.
Yet, until recently, the only NIR probe approved by the U.S. Food and Drug Administration (FDA) was indocyanine green (ICG) due to the above-mentioned issues. ICG, a carbocyanine dye, absorbs and fluoresces in the NIR region of light exhibiting absorption and emission maxima at about 780 nm and about 820 nm, respectively. ICG is used clinically as an agent for optical imaging in angiography (Florian Schot et. al., Clinical and Experimental Ophthalmology, 2002. 30(2): p. 110-114) and in guiding sentinel node biopsy (Motomura, K. et al., Sentinel node biopsy guided by indocyanine green dye in breast cancer patients. 1999, FPCR. p. 604-607) and so on. As mentioned above, these wavelengths are relatively transparent and the penetration depth of light in biological tissue is high (Anderson, R. and J. Parrish, Journal of Investigative Dermatology, 1981. 77(1): p. 13-19). However, several physicochemical characteristics limit the application of ICG in vitro and in vivo imaging. The pharmacokinetics of ICG is extremely fast, ICG binds to proteins to clear rapidly from the circulatory system with a plasma half life of 2-4 min (Desmettre, T. et. al., Survey of Ophthalmology, 2000. 45(1): p. 15-27; Serge Mordon et. al., Lasers in Surgery and Medicine, 1997. 21(4): p. 365-373), and aqueous ICG has a low fluorescence quantum yield and nonspecific quenching (Benson, R. and H. Kues, Physics in Medicine and Biology, 1978. 23(1): p. 159-163). An aqueous ICG solution is unstable, as the compound undergoes thermal degradation and photo-degradation. It has been reported to be unstable in physiologically relevant solutions, such as water, salt solution, plasma, and blood. The ICG shows decreased absorption and reduced fluorescence, because oxidation and dimerization degrade the original molecule (Vishal Saxena, M.S. and Jun Shao,, Journal of Pharmaceutical Sciences, 2003. 92(10): p. 2090-2097).
In recent years, various nanomaterials with controlled size and shape were developed and used widely. Thus, attention has also focused on the synthesis of fluorophore doped silica nanoparticles (NPs), which provide an effective barrier keeping the dye from the surrounding environment, and both photobleaching and photodegradation phenomena that often affect conventional dyes can be minimized, because the dye molecules are trapped inside the silica matrix. The silica matrix not only protects the dye but also provides some unique features. For example, it is a biocompatible substance and extremely stable in an adverse environment. Several kinds of inorganic and organic dye-doped silica nanoparticles have been developed (Santra, S. et al., Journal of Biomedical Optics, 2001. 6: p. 160; Yan, J. et al., Nano Today, 2007. 2(3): p. 44-50). However, the ICG dye could not be encapsulated directly into silica to form silica fluorescent nanoparticles for electrostatic repulsion between the negatively charged ICG dye and the negatively charged silica matrix.
In previous studies on NIR fluorescent biomarkers, polymer-based carriers used to address the intrinsic issues of ICG degradation and rapid blood clearance. Saxena et al. prepared about 300 nm poly(lactic-co-glycolic acid) (PLGA) particles that contained ICG (as much as 29 wt%), in which the chemical stability of the ICG was increased and the ICG clearance time was lengthened (Saxena, V. et. al., International journal of pharmaceutics, 2004. 278(2): p. 293-301). Yu, J. et al. reported ICG-containing nanoparticle-assembled silica capsules (Yu, J. et al., Chemistry of Materials, 2007. 19(6): p. 1277-1284). Among these technologies, ICG demonstrates improved optical stability. However, these carriers suffered significant leakage with 78% ICG loss within 8 hr in physiological conditions. Subsequently, a silica-polymer composite microcapsule was developed to improve encapsulated ICG retention (17% ICG leakage after 8 hr at 37 ℃), but the addition of the nanoparticulate shell increased the particle size to 0.4 μm to 1.0 μm. Silica nanoparticles can avoid dye leakage and photobleaching more effectively. The method makes it easy to control the size of nanoparticles at the nano level.
Accordingly, the present inventors have made efforts to develop ICG dye-doped silica nanoparticles as a new type of NIR dye delivery material. As a result, the presentinventors have succeeded in preparing ICG-doped silica nanoparticles by conjugating indocyanine green (ICG)with polyethyleneimine (PEI) or the like as a core and successfully entrapping the PEI-conjugated ICG into a silica matrix by the Stober method, and have found that the prepared nanoparticles show high sensitivity and low leakage, thereby completing the present invention.
It is an object of the present invention to provide silica nanoparticles, which can be used for in vitro and in vivo imaging and contains a dye in the core.
Another object of the present invention is to provide a method for preparing said nanoparticles.
To achieves the above objects, the present invention provides silica nanoparticles doped with indocyanine green (ICG) conjugated with a positively charged molecule such as polyethylenimine (PEI), aminopropyl trimethoxysilane or bovine serum albumin, in which the ICG-doped silica nanoparticles can be used as a near-infrared fluorescent nanoprobe for biological imaging.
Also, the present invention provides a method for preparing silica nanoparticles doped with ICG conjugated with a positively charged molecule, the method comprising the steps of: i) conjugating ICG with a positively charged molecule as a core; and incorporating the positively charged molecule-conjugated ICG into silica nanoparticles.
If the positively charged molecule used in the method of the present invention is a polymer, silica nanoparticles having stronger fluorescence intensity can be obtained.
As described above, the ICG-doped silica nanoparticles synthesized according to the method of the present invention has advantages in that the size thereof is easily controlled at the nano level and in that they can be surface-modified via versatile routes and have low leakage, low toxicity, low photo bleaching, high sensitivity enough to apply for in vitro and in vivo imaging, and sustained stability.
FIG. 1 shows the structural formula of indocyanine green (ICG) used in the present invention.
FIG. 2 schematically shows the photobleaching of an ICG dye in silica nanoparticles.
FIG. 3 is a graphic diagram showing the photobleaching of an ICG dye in silica nanoparticles.
FIG. 4 is a graphic diagram showing dye leakage from silica nanoparticles.
FIG. 5 is a TEM image of synthesized nanoparticles.
FIG. 6 shows the absorbance and fluorescence spectra of nanoparticles.
FIG. 7 is a set of graphs showing the fluorescence intensity of nanoparticles including the polymer polyethyleneimine(the left side graph) and the fluorescence intensity of nanoparticles including low-molecular-weight aminopropyl trimethoxysilane.
FIG. 8 shows images of fluorescence penetrations at various thicknesses of pork.
Hereinafter, the present invention will be described in detail.
The present invention provides silica nanoparticles doped with indocyanine green (ICG) conjugated with a positively charged molecule, such as polyethylenimine, aminopropyl trimethoxysilane or bovine serum albumin, which can be used as a near-infrared fluorescence nanoprobe for biological imaging.
In the inventive silica nanoparticles doped with the ICG conjugated with the positively charged molecule, the positively charged molecule is preferably PEI.
Also, the presentinvention provides a method for preparing silica nanoparticles doped with ICG conjugated with a positively charged molecule, the method comprising the stepsof: i) conjugating ICG with a positively charged molecule as a core; and ii) incorporating the positively charged molecule-conjugated ICG into silica nanoparticles.
In the inventive method for preparing the silica nanoparticles doped with the ICG conjugated with the positively charged molecule, the positively charged molecule is preferably selected from the group consisting of PEI, aminopropyl trimethoxysilane and bovine serum albumin. More preferably, the positively charged molecule is PEI.
If a polymer such as PEI is used as the positively charged molecule, there is an advantage in that the resulting silica nanoparticles can have increased fluorescence intensity.
Also, in the method for preparing the silica nanoparticles doped with the ICG conjugated with the positively charged molecule, the silica nanoparticles used in step (ii) are preferably produced by hydrolysis of tetraethyl orthosilicate (TEOS).
Near-infrared light has a high penetration depth in the body compared to visible light and has less effect on the interference of scattered light, and thus it is highly useful for bio-imaging studies. Various near-infrared dyes have been developed, and particularly indocyanine green (ICG) was approved by the US FDA and is being used in clinical surgery. However, the negatively charged indocyanine green has a problem in that it is not entrapped inside negatively charged silica nanoparticles due to repulsion with the silica nanoparticles. To solve this problem, in the present invention, a method of adding a positively charged molecule to a dye solution was used. The positively charged molecule may be selected from the group consisting from the group consisting of low-molecular-weight aminopropyl trimethoxysilane, the positively charged polymer polyethyleneimine and the protein bovine serum albumin. In the present invention, the positively charged molecule was used to prepare nanoparticles doped with indocyanine green.
The present inventors have designed ICG dye-doped silica nanoparticles as a new type of NIR dye delivery material. In the method of the present invention, the ICG dye is successfully entrapped inside the silica matrix, and the sensitivity of ICG dye-doped silica nanoparticles is improved. Typically, PEI has a positively charged amine group, and ICG has a negative charge. For this reason, in order to successfully entrap ICG inside the silica matrix, ICG is first conjugated with polyethylenimine(PEI) as a core. Then, ICG-doped nanoparticles are prepared using the PEI-conjugated ICG as a core and a silica, produced by hydrolysis of tetraethyl orthosilicate (TEOS), as a shell, by the Stober method (Stober, W. and A. Fink, Bohn, (1968) Controlled growth of monodisperse silica spheres in the micron size range. Colloid Interface Sci. 26: p. 62:69; Wang, L. and W. Tan, Multicolor FRET silica nanoparticles by single wavelength excitation. Nano letters, 2006. 6(1): p. 84). The results show that the PEI-conjugated ICG-doped silica nanoparticles displayed high sensitivity and low leakage. ICG is a weak fluorophore having a low quantum yield of only 1.3% in an aqueous solvent, because it has complicated solution behavior due to its amphiphilic nature (hydrophilic sulfate groups and hydrophobic dimethylated benzoindotricarbocyanin groups) (see FIG. 1). It forms aggregates in water depending on its concentration. According to the design of the present inventors, the ICG dye is held by each amine group on the polymer chains, which force the ICG molecules to aggregate with each other, so this kind of structure reduces the self quenching. The PEI-conjugated ICG is a very large molecule, so it reduces the dye leakage. The present invention describes the successful synthesis of PEI-conjugated ICG-doped silica nanoparticles, the size of which is easily controlled at the nano level and which can be surface-modified via versatile routesand have low leakage, low toxicity, low photo bleaching and high sensitivity enough to apply for in vitro and in vivo imaging.
The cationic additive functions not only to entrap the dye molecule inside the silica nanoparticles, but also increase the fluorescence intensity of the nanoparticles. If the concentration of the dye in the nanoparticles is excessively high, the dye will absorb the fluorescence of the surrounding molecules,or the light scattering will be increased, leading to a decrease in fluorescence intensity. Wiesner introduced the core-shell concept, and according to the present invention, when the polymer additive is added to the dye molecules, the dye molecules are dispersed in the nanoparticles, and thus the fluorescent signal is increased.
Also, in order to examine the applicability of the near-infrared dye-doped silica nanoparticles to in vivo imaging, a solution of the nanoparticles was immobilized on a glass plate, pork was placed on the immobilized nanoparticles, and then a penetration experiment for the nanoparticles was carried out. As a result, as shown in FIG. 8, it was observed that fluorescence was emitted through the 2.5 cm thick pork.
Using the Stober method, the present inventors prepared PEI-conjugated ICG-doped silica nanoparticles and ICG-doped silica nanoparticles. Specifically, ICG was conjugated with an ethylenimine polymer as a core, and APTS and a PEI solution were added to the ICG/DMSO solution to link the ICG to the PEI and the APTS, thereby covalently conjugating the ICG-PEI to silica nanoparticles. Then, an ammonium hydroxide solution was added to the mixture to cause an activation reaction. Also, ICG-doped silica nanoparticles were synthesized by the Stober method in the same manner as described above, except that the core consisted only of ICG.
The characteristics of the PEI-conjugated ICG-doped silica nanoparticles were analyzed. Namely, the size and fluorescence intensity of the nanoparticles were analyzed. ICG has two polycyclic parts imparting a lipophilic property to the molecule, and a sulfate group bound to each polycyclic part and imparting property to the molecule. ICG cannot be doped into the silica nanoparticles because of the repulsion between the negatively chargedsulfate group of ICG and the negatively charged silica matrix in the neutral pH range. The negatively charged sulfate group of ICG can be conjugated with the positively charged amine group of APTS, and then it can be doped into silica nanoparticles by the Stober method. However, ICG forms aggregates in water depending on its concentration. Since ICG has a low quantum yield in an aqueous solvent, the ICG-doped silica nanoparticles emit a too weak signal, and thus it is difficult to perform in vivo imaging using the ICG-doped silica nanoparticles.
In comparison with this, the core structure having PEI conjugated to ICG forces the ICG molecules to aggregate with each other and increases the signal intensity by about 2 times.Thus, the PEI-conjugated ICG-doped silica nanoparticles can be used as a near-infrared fluorescent nanoprobe for biological imaging (see FIG. 2).
The present inventors investigated the photostability of the ICG-PEI-doped silica nanoparticles in an aqueous phase. The ICG-PEI-doped nanoparticles showed a little photobleaching and high light emission intensity compared to the nanoparticles doped only with the ICG dye. This is because the photostability of the ICG dye was increased in the process of conjugating ICG with the PEI polymer and doping the PEI-conjugated ICG into the silica matrix (see FIG. 3).
The leakage of the ICG dye from the silica nanoparticles with the change in the fluorescence intensity of a solution of the nanoparticles was measured. As a result, the emission intensity of the ICGdye-doped silica nanoparticles was maintained at 78% of the original emission intensity, and the emission intensity of the ICG-PEI-doped nanoparticles was maintained at 90% of the original emission strength (see FIG. 4). These results indicate that, because the PEIis a long-chain polymer, the silica nanoparticles can effectively prevent due leakage.
Hereinafter, the present invention will be described in further detail with reference to examples. It is to be understood, however, that these examples are for illustrative purposes only and are not to be construed to limit the scope of the present invention. Also, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention.
Example 1: Materials
Indocyanine green (ICG), 3-(aminopropyl)triethoxysilane (APTS) and phosphate buffered saline (PBS) were purchased from Sigma (St. Louis, MO). Polyethylenimine (PEI) (MW 60,000) was purchased from Supelco and dissolved in acetone. Tetraethyl orthosilicate (TEOS) and a 29 wt% aqueous solution of ammonia were purchased from Aldrich (Milwaukee, WI). 2-[Methoxy(polyethylenoxy)propyl]trimethoxysilane (PEG-silane, 90%) was purchased from Gelest (Morrisville, PA).
Example 2: Preparation of PEI-conjugated ICG-doped silica nanoparticles and ICG-doped silica nanoparticles
PEI-conjugated ICG-doped silica nanoparticles were synthesized using the Stober method (Stober, W. and A. Fink, Bohn, (1968) Controlled growth of monodisperse silica spheres in the micron size range. Colloid Interface Sci. 26: p. 62:69; Wang, L. and W. Tan, Multicolor FRET silica nanoparticles by single wavelength excitation. Nano letters, 2006. 6(1): p. 84). First, ICG was conjugated with an ethyleneimine polymer as a core. 3.08 ㎖ of APTS and 3 ㎎ (50 nM) of PEI solution were added to 1 ㎖ of the ICG/DMSO solution (11 mM), and the mixture was vigorously stirred for 17 hours to link the ICG to the PEI and the APTS, thereby covalently conjugating the ICG-PEI to silica nanoparticles. Then, 1.244 ㎖ of ammonium hydroxide solution was added to the mixture which was then subjected to an activation reaction at room temperature for 5 hours. After 355 ㎖ of TEOS has been added, the mixture was stirred at room temperature for 36 hours. The stirred mixture was centrifuged at 13,800 rpm for 30minutes to separate the silica nanoparticles from unreacted silica compounds. The separated silica nanoparticles were washed twice with ethanol and several times with PBS. The resulting product was redispersed in PBS and stored in a dark place at 4 ℃ for future use.Meanwhile, ICG-doped silica nanoparticles were also synthesized using the Stober method in the same manner as described above, except that the core of the nanoparticles consisted only of ICG. Specifically, 3.08 ㎖ of APTS was added to 1 ㎖ of ICG solution, and the mixture was vigorously stirred for 17 hours to link the ICG to the APTS, thereby covalently conjugating the ICG to silica nanoparticles.
Example 3: Analysis of characteristics of PEI-conjugated ICG-doped silica nanoparticles
The shape of the nanoparticles prepared in Example 2 was examined under a transmission electron microscope (H-7600, Hitachi, Tokyo, Japan). The size of the nanoparticles was measured by the image J. The fluorescence intensity of the nanoparticles was determined by a Varioskan Flash spectral scanning multimode reader (Thermo Fisher Scientific NYSE: TMO). The excitation wavelength used in all the studies was 789 ㎚.
Structurally, ICG has a complex molecular structure, which has two polycyclic parts imparting a lipophilic property to the molecule and a sulfate group bound to each polycyclic part and imparting a hydrophilic property to the molecule. Thus, ICG shows solubility in various organic solvents such as DMSO, methanol, acetonitrile, etc. ICG could not be doped into silica nanoparticles because of the repulsion between the negatively charged sulfate group of ICG and the negatively charged silica matrix in the neutral pH range. The negatively charged sulfate group of ICG can be conjugated with the positively charged amine group of APTS, and then ICG can be doped into silica nanoparticles by the Stober method. However, ICG forms aggregates in water depending on its concentration. Since ICG has a low quantum yield in an aqueous solvent, the ICG-doped silica nanoparticles emit a too weak signal, and thus it is difficult to perform in vivo imaging using the ICG-doped silica nanoparticles.
The present inventors designed a core structure in which PEI was conjugated to ICG through electrostatic interaction. This kind of structure forces the ICG molecules to aggregate with each other and increases the signal intensity of the nanoparticles by about two times. The PEI-conjugated ICG-doped silica nanoparticles provide enough sensitivity to be used as a near-infrared fluorescent nanoprobe for biological imaging (see FIG. 2).
Example 4: Photostability of free ICG dye and ICG-PEI-doped silica nanoparticles
A solution of 2 ㎎/㎖ ICG in DMSO and a solution of 5 ㎎/㎖ ICG-PEI-doped nanoparticles in PBS buffer were prepared. The samples were excited at 790 nm, and the emission wavelength was recorded at 820 nm 7 times at 90-min intervals with a Varian Carey Eclipse Fluorescence Spectrophotometer. The solutions were exposed to UV light.
The present inventors investigated the photostability of the ICG-PEI-doped silica nanoparticles in an aqueous phase. The ICG dye-doped nanoparticles showed a little photobleaching, and the emission intensity thereof decreased to about 87.8%. However, the intensity of pure dye decreased to about 15.6%. Such results indicate that the dye-doped silica nanoparticles improve the stability of the ICG dye. Also, the ICG-PEI-doped nanoparticles showed a little photobleaching, and the emission intensity thereof decreased to about 93.7%. Such results demonstrate that the photostability of the ICG dye was increased when ICG was conjugated with the PEI polymer and doped into the silica matrix (see FIG. 3).
Example 5: Dye leakage from silica nanoparticles
The leakage of ICG dye from the silica nanoparticles with the change in the fluorescence intensity of a solution of the nanoparticles was measured. For this purpose, 10 ㎎ of the nanoparticles were dispersed in 2 ㎖ of PBS buffer. The nanoparticle sample was centrifuged at 13,800 rpm for 15 minutes, redispersed in 2 ㎖ of PBS buffer and stored in a dark place at room temperature. The nanoparticles were washed for one week, and then the total fluorescence intensity of the ICG dye in the nanoparticles was measured at 24-hour intervals.
After the nanoparticles have been stored in the PBS buffer for one week, the emission intensity of the ICG dye-doped silica nanoparticles was maintained at 78% of the original emission intensity, and the emission intensity of the ICG-PEI nanoparticles was maintained at 90% of the original emission intensity (FIG. 4). Such results indicate that the silica nanoparticles can effectively prevent dye leakage and that the PEI which isa long-chain polymer can more effectively prevent dye leakage.
Although the preferred embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
Claims (6)
- Silica nanoparticles doped with indocyanine green (ICG) conjugated with a positively charged molecule.
- The silica nanoparticles of Claim 1, wherein the positively charged molecule is selected from the group consisting of polyethylenimine (PEI), aminopropyl trimethoxysilane and bovine serum albumin.
- The silica nanoparticles of Claim 1, wherein the positively charged molecule is a polymer.
- A method for preparing silica nanoparticles doped with ICG conjugated with a positively charged molecule, the method comprising the steps of:i) conjugating ICG with a positively charged molecule as a core; andii) incorporating the positively charged molecule-conjugated into silica nanoparticles.
- The method of Claim 4, wherein the positively charged molecule is selected from the group consisting of polyethylenimine (PEI), aminopropyl trimethoxysilane and bovine serum albumin.
- The method of Claim 4, wherein a polymer is used as the positively charged molecule to increase the fluorescence intensity of the nanoparticles.
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| CN106190106A (en) * | 2016-07-15 | 2016-12-07 | 中国科学院自动化研究所 | Near-infrared mesoporous silicon dioxide nano probe of target tumor and preparation method thereof |
| CN115245576A (en) * | 2021-12-20 | 2022-10-28 | 上海市第六人民医院 | Near-infrared phosphorescent carbon dot and cancer cell membrane encapsulated near-infrared fluorescent carbon dot composite nanoparticle, and preparation method and application thereof |
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| KR200481528Y1 (en) | 2016-07-19 | 2016-10-11 | 김덕우 | Apparatus for obtaining angiography image |
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| CN104974518A (en) * | 2015-07-24 | 2015-10-14 | 陕西师范大学 | Polyethyleneimine/silicon dioxide core-shell structure composite nano material and preparation method |
| CN106190106A (en) * | 2016-07-15 | 2016-12-07 | 中国科学院自动化研究所 | Near-infrared mesoporous silicon dioxide nano probe of target tumor and preparation method thereof |
| CN106190106B (en) * | 2016-07-15 | 2018-06-29 | 中国科学院自动化研究所 | Near-infrared mesoporous silicon dioxide nano probe of target tumor and preparation method thereof |
| CN115245576A (en) * | 2021-12-20 | 2022-10-28 | 上海市第六人民医院 | Near-infrared phosphorescent carbon dot and cancer cell membrane encapsulated near-infrared fluorescent carbon dot composite nanoparticle, and preparation method and application thereof |
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