KR20120101242A - Quantum dot encapsulated ps-psma nanofibers and a use of the same - Google Patents

Abstract

PURPOSE: A polystyrene-poly(styrene-co-maleic anhydride) nanofiber composite containing quantum dots is provided to ensure durability. CONSTITUTION: A polystyrene-poly(styrene-co-maleic anhydride) nanofiber composite contains quantum dots. A sensor for gas sensing contains the nanofiber composite. The gas is a volatile organic solvent. An enzyme-nanofiber composite is prepared by fixing an enzyme to the nanofiber composite. The enzyme is esterase, chymostrypsin, or lipase. A method for preparing the composite comprises: a step of mixing polystyrene and poly(styrene-co-maleic anhydride) in a container; a step of adding dimethyl formamide(DMF), tetrahdyrofurane, or a mixture solvent of tetrahydrofurane and acetone; a step of adding quantum dots; and a step of electrospinning the mixture solution.

Description

Polystyrene-poly (styrene-co-maleic hydride) nanofiber composites containing quantum dots and its application {Quantum Dot Encapsulated PS-PSMA Nanofibers and a use of the same}

The present invention relates to polystyrene-poly (styrene-co-maleic hydride) nanofiber composites comprising quantum dots and more specifically to polystyrene-poly (styrene-co-maleic hydride) comprising quantum dots. Ride) nanofiber composite and the use thereof as a support for gas sensing or enzyme immobilization.

In general, electrospun functional nanofibers have various applications in the fields of chemical sensors, enzyme immobilization, tissue engineering, drug delivery membrane filters and fibers (HS Yoo, TG Kim and TG Park, Adv. Drug Deliv. Rev., 61 (2009) 1033-1042; J. Yoon, SK Chae and J.-M. Kim, J. Am. Chem. Soc., 129 (2007) 3038-3039; A. Greiner and J. Wendorff, Angew.Chem.-Int.Edit., 46 (2007) 5670-5703; JY Lee, CA Bashur, AS Goldstein and CE Schmidt, Biomaterials, 30 (2009) 4325-4335; A. Camposeo, FD Benedetto, R. Stabile , AAR Neves, R. Cingolani and D. Pisignano, Small, 5 (2009), 562-566; G. Ren, X. Xu, Q. Liu, J. Cheng, X. Yuan, L. Wu and Y. Wan , React.Funct.Polym., 66 (2006), 1559-1564; L. Wannatong and A. Sirivat, React.Funct.Polym., 68 (2008), 1646-1651; A. Senecal, J. Magnone, P. Marek and K. Senecal, React. Funct. Polym., 68 (2008), 1492-1434).

Enzymes, on the other hand, are biocatalysts with great specificity that play an important role in the production of valuable products. They can be applied to food processing, pharmaceuticals, chemical conversion, detergent fields, biological restoration, biosensors, and biofuel cells (KM Koeller and CH Wong, Nature , 2001, 409 , 232-240; A. Schmid, JS Dordick). , B. Hauer, A. Kiener, M. Wubbolts and B. Witholt, Nature , 2001, 409 , 258-268; N. Duran and E. Esposito, Appl Catal B- Environ , 2000, 28 , 83-99; A. Morana, A. Mangione, L. Maurelli, I. Fiume, O. Paris, R. Cannio and M. Rossi, Enzyme Microb Tech , 2006, 39 , 1205-1213; E. Katz and I. Willner, J Am Chem Soc , 2003, 125 , 6803-6813). Although enzymes are important biological catalysts, they have limitations due to their short life cycle. Given that the functional role of proteins is primarily in their structure, enzyme proteins are destabilized due to structural changes induced by the local environment. Also the separation of enzymes from the reaction products and their reuse are very difficult and it creates a need for a carrier or stable enzyme system in terms of cost effectiveness and is a necessary requirement for successful application.

In order to overcome this problem, the researchers have been devoted to developing an enzyme immobilization method, and since immobilized enzymes have their increased bioactivity, they can be applied to various processes and reused.

The use of PS-PSMA polymer nanofibers for enzyme immobilization has been reported (BC Kim, S. Nair, JB Kim, JH Kwak, J. W Grate, SH Kim and MB Gu, Nanotechnology, 16 (2005), S382-S388 ; JH Lee, ET Hwang, BC Kim, SM Lee, BI Sang, YS Choi, JB Kim and MB Gu, Appl.Microbiol.Biotechnol., 75 (2007), 1301-1307; BC Kim, SM Lee, D. Lofez Ferrer, HK Kim, S. Nair, SH Kim, BS Kim, K. Petritis, DG Camp, JW Grate, RD Smith, YM Koo, JB Kim and MB Gu, Proteomics, 9 (2009), 1893-1900; HK Ahn, BC Kim, SH Jun, MS Chang, D. Lopez-Ferrer, RD Smith, MB Gu, SW Lee, BS Kim and JB Kim, Biotechnol.Bioeng., 107 (2010), 917-923).

Surface functionalization, immobilization of biomolecules, and mixing of organic materials such as chemical drugs enable their various usefulness, but incorporation of inorganic materials, such as quantum dots (hereinafter referred to as 'QD'), can be achieved in polymer matrices. It is difficult to succeed due to aggregation of quantum dots. It is therefore desirable and necessary to have a single, homogeneous distribution of quantum dots within a nanofiber polymer network.

Nanocrystalline quantum dots are photostable fluorophores with unique optical spectrum properties and are widely used in the fields of labeling, imaging and sensing. Nanofibers prepared by electrospinning with QDs filled with a polymer matrix can be used as wave guides (H. Liu, J. Edel, L. Bellan and HG Craighead, Small, 2 (2006), 495-499). Yang, X. Jiang, F. Gu, Z. Ma, J. Zhang and L. Tong, J. Appl.Polym. Sci., 110 (2008), 1080-1084; M. Li, J. Zhang , H. Zhang, Y. Liu, C. Wang, X. Xu, Y. Tang and B. Yang, Adv. Funct. Mater., 17 (2007), 3650-3656). The unique nature of flickering under light indicates that the quantum dots are well distributed and exist as single nanoparticles in the medium.

In the present invention, we report that such novel nanofiber nanocomposites are synthesized which may have unique physical properties. The synthesized fibers have induced electrical properties that can be used in gas sensing applications and other mold and infrastructure technologies.

The present invention has been made in view of the above necessity, and an object of the present invention is to provide a nanofiber composite having novel physical properties.

In order to achieve the above object, the present invention provides a polystyrene (PS) -poly (styrene-co-maleic hydride) nanofiber composite including a quantum dot.

In another aspect, the present invention provides a sensor for gas sensing comprising the nanofiber composite of the present invention.

In one embodiment of the present invention, the gas is preferably a volatile organic solvent, more preferably chloroform, dimethylformamide (DMF) or tetrahydrofuran (THF), but is not limited thereto.

The present invention also provides an enzyme-nanofiber complex in which an enzyme is immobilized on the nanofiber complex of the present invention.

In one embodiment of the present invention, the enzyme may be any enzyme commercially available, preferably esterase, chymotrypsin or lipase, but is not limited thereto.

In addition, the present invention is to mix the polystyrene (PS) and poly (styrene-co-maleic hydride) in the container,

To the vessel is added a mixed solvent of dimethylformamide (DMF), tetrahydrofuran or tetrahydrofuran and acetone, to which a quantum dot is added and mixed,

Provided is a method for preparing a polystyrene (PS) -poly (styrene-co-maleic hydride) nanofiber composite including a quantum dot comprising electrospinning the prepared mixed solution.

In one embodiment of the present invention, the mixing ratio of the polystyrene (PS) and poly (styrene-co-maleic hydride) may vary depending on the amount of the electrospinning and the amount of the solvent, and various combinations are possible. In the embodiment of the invention is adopted that the 4: 1 weight ratio, but is not limited thereto.

Hereinafter, the present invention will be described.

Electrospinning is an effective method for distributing nanoparticles such as quantum dots (hereinafter referred to as 'QDs') in polymer matrices for producing novel composite nanofibers.

In the present invention, fluorescent CdSe with ZnS core shell QDs was successfully distributed in the mixture at 4: 1 ratio of Polystyrene (PS) and Polystyrene-co-maleic anhydride (PSMA) without forming naked phase beads in the fibers. The resulting nanofibers were characterized by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM), and finally the fluorescence measurements were performed to determine the uniformity of PS-PSMA nanofibers with a single size distribution and high aspect ratio. It was used to evaluate. Incorporation of QDs into PS-PSMA nanofibers induced electrical conductivity that could be applied to many sensing applications, but similar electrical conductivity was not observed when QDs were replaced with iron oxide or gold nanoparticles (AuNPs). These nanocomposite nanofibers also exhibited an electrical conductivity of two to three times increased in the presence of volatile organic compounds. The obtained quantum dot nanofibers (hereinafter, referred to as 'Qd-NFs') have a light stability of 600 to 650 nm that are uniformly distributed with light stability of 6 months or more, and can be applied to the field of electric fluorescence or gas-based sensing.

In addition, the inventors have developed and applied a nonwoven patch type polymer nanofibers filled with quantum dots (QDs) through an electrospinning process for enzyme immobilization. The QDs are believed to induce shape rigidity and high compactness in nanofibers. Compactness changes observed in nanofibers can lead to improved immobilization efficiency of enzymes. Esterase-nanofiber composites are prepared by cross linking of enzyme-aggregates on the surface of nanofibers. We compared the reaction rate constants of QDs-nanofibers and pristine nanofibers, and the QDs-nanofiber composites did not show breakage of halide even after long-term storage and could be reused with preserved stability. The novel composite materials developed in the present invention could be successfully applied as scaffolds for enzyme immobilization and could be attractive carriers for enzyme based processes due to the ease of morphological control.

Hereinafter, the present invention will be described in detail.

Nanoparticles PS - PSMA  Synthesis and Properties of Nanofibers

Conditions for PS-PSMA nanofibers without gross bead formation with high aspect ratio and single size were determined by varying the proportion of PS and PSMA dissolved in different solvents and electrospinning at different operating voltages. To prepare the novel polymeric nanofiber composites, two different emission (green and red) fluorescent hydrophobic (TOPO) surface modified CdSe / ZnS QDs were used. To obtain QDs encapsulated nanofiber composites, each of the two QDs was uniformly mixed and electrospun in a PS-PSMA solution. 1 shows a comparison between emission spectra of green fluorescent QDs PS-PSMA nanofibers and PS-PSMA nanofibers alone with strong emission peaks as observed at 565 nm. PS-PSMA nanofibers exhibited some degree of auto fluorescence in the 400-500 nm wavelength range associated with the polymer matrix itself. On the other hand, QDs PS-PSMA nanofibers showed a high emission peak consistent with the release of green QDs encapsulated in nanofibers. This electrospun nonwoven nanofibers were then observed through a fluorescence microscope to identify a single distribution of QDs in the PS-PSMA polymer nanofibers. The fluorescence micrograph shown in FIG. 2 is a representative image of several electrospun nanofibers. We found that both green and red QDs were uniformly distributed in the PS-PSMA nanofiber length direction (FIGS. 2A and 2B). Fluorescence micrographs show a uniform distribution of QDs in a typical nonwoven QDs PS-PSMA nanofiber sheet (FIG. 2C). Some QDs PS-PSMA aggregates are formed by droplets from an electrospinning solution, but they are not part of the nanofiber structure. Fluorescence images show that QDs are mostly encapsulated in a single fluorescence intensity throughout the nanofiber composite. 3A shows an SEM image of PS-PSMA having a thickness range between 600 and 700 nm, and the diameter of the PS-PSMA nanofibers can be further controlled by precise control of the applied flow rate and potential. This thickness of several hundred nanometers is desirable when considering nanoparticle encapsulation because their hydrodynamic radii is ˜100 nm or less in the polymer matrix. FIG. 3B shows an SEM image of iron oxide PS-PSMA nanofibers easily attracted to permanent magnets exhibiting induced paramagnetic properties, and similarly FIG. 3C shows similar morphology and aspect ratio compared to nanofibers with PS-PSMA only AuNPs encapsulated AuNPs PS-PSMA nanofibers show that the morphological stability of the nanofibers is independent of the nature of the nanoparticles used for mixing. Nanoparticle encapsulations of size up to 50 nm did not affect the morphology of the electrospun nanofiber result as observed and shown in FIG. 3D showing SEM micrographs of fluorescent green QDs PS-PSMA nanofiber composites. It is very similar in appearance with PSMA nanofibers. From the obtained fluorescence micrographs and SEM images, the electrospun PS-PSMA polymer matrix provides an excellent support base for encapsulating nanoparticles without phase separation to obtain a single, high aspect ratio nanofiber composite derived from the partial physical properties of the nanoparticles. It can be concluded that

PS - PSMA  Conductivity of Nanocomposite Nanofibers

After mixing inorganic nanoparticles such as AuNPs, QDs and iron oxides in the PS-PSMA polymer matrix, the nanofiber results are typically expected to achieve fluorescence and paramagnetism induced in the nanofiber composites. Since organic polymers are usually insulators and used as thermoplastics, both PS and PSMA polymers are electrically inert in nature. The resulting electrospun nanofiber composite was tested for induced electrical conductivity by internally inserting conductive fillers such as AuNPs, iron oxide and QDs. The sheet conductivity of the nonwoven electrospun PS-PSMA nanofibers and composites thereof was measured at a constant thickness and length, with the weight of the nanofibers kept constant. 4 shows a current versus voltage (IV) graph of PS-PSMA nanofibers and composites thereof. As expected, the PS-PSMA nanofibers did not exhibit conductivity because the base polymer matrix is insulated in nature. However, by insertion of inorganic iron oxide or metallic AuNPs conductive nanoparticles, both iron-oxide PS-PSMA and AuNPs PS-PSMA nanofiber composites were similarly non-conductive. However, semiconductor QDs induced electrical conductivity in the PS-PSMA polymer matrix, as shown in FIG. 4. To demonstrate that the conductivity is single through the QDs PS-PSMA nanofibers, nanofiber sheet conductivity of various lengths (1.5 mm to 20 mm) was measured using a probe station. As can be seen in Figure 4, the electrical conductivity is uniform throughout the length of the nanofiber in accordance with Ohm's law, the conductivity is calculated in the range 1.15 ~ 1.65 x 10 ^-6 S / m while PS conductivity is 10 ^-16 S / m. This can be inferred that QDs interact with the PSMA site chain to induce charge transfer; This was not observed when QDs were encapsulated in PS nanofibers (not shown). It can be concluded that 2 wt% of QD can induce conductivity in the PS-PSMA polymer matrix compared to 10 wt% iron oxide nanopowders which did not induce large amounts or charge transfers.

Gas induced conductivity

Nanocomposites filled with conductive fillers may be useful materials for organic vapor sensing applications due to ease of use and cost effectiveness. When gas vapor diffuses into the polymer matrix, expansion occurs resulting in the expansion of the matrix and the distance inside the molecule increases between the conductive fillers, resulting in poor conductivity. Since conductivity was observed in QDs PS-PSMA nanofibers, these materials were tested for applicability with gas sensors. Current was measured in a closed glass chamber with three different organic solvents, THF (Tetrahydrofuran), chloroform and DMF (N, N-dimethylformamide) vapor. When only PS-PSMA nanofibers were performed for gas sensing measurements, no detectable conductivity was measured in any organic solvent. 5A-C show the results of gas conductivity experiments of QDs PS-PSMA nanofibers under the influence of chloroform DMF and THF vapor in a saturated atmosphere of 0.001% to 99.9%. As the solvent concentration increased, the conductivity in QDs PS-PSMA nanofibers increased rapidly with very stable output. This reaction is often in stark contrast to the fact that organic solvents can increase resistance in nanofibers (AR Hopkins and NS Lewis, Anal. Chem., 73 (2001), 884-892). For gas sensing purposes, QDs PS-PSMA nanofibers showed higher conductivity in the presence of chloroform and THF vapor compared to DMF. After gas sensing experiments, QDs PS-PSMA nanofibers were examined to determine if there was a solvent vapor induced morphological change. After exposure to 99.9% solvent vapor atmosphere, the nanofibers were sensing experiments which showed no significant change in morphology (not shown). The QDs PS-PSMA nanofibers exhibited stable conductive reactions in the presence of volatile organic solvents with a reaction time of several seconds or less and can be reused as gas sensors without loss of conductivity for more than six months.

QD  Structural Changes of Encapsulated Nanofibers

The difference due to QD encapsulation in the nanofibers is clearly seen in FIGS. 6A and 6B where the nanofibers with QDs are denser than the pristine nanofibers and closely packed with very little distance inside the nanofibers. The single distribution of QD-nanofibers causing its compactness is mainly due to its tightly packed nanofibers. Changes in the compactness and morphology of QDs-nanofibers were confirmed by SEM images (not shown) and found to be induced by increasing the concentration of QDs. The mechanism of morphology change after introduction of QDs is not yet clear, but it is believed that QDs contribute to the morphological reshaping of QDs-nanofibers in QDs-polymer mixed solutions. 6C shows a TEM image of QDs arranged in parallel in the longitudinal direction of the nanofibers, so it is believed that the nanofibers impart rigidity to the nanofibers produced by electrospinning. 6D shows photographs of 1.5 mm ² sized QDs-nanofibers cut into small patches. It has been found that QDs-nanofibers with high stiffness and strength are easily stamped like paper with little force. However, for pristine nanofibers, the manipulation of nanofibers with patches was not possible due to their properties showing low density and rigidity.

On enzyme immobilization QD  Application of Encapsulated Nanofibers

Structural changes induced by QDs in nanofibers can affect enzyme immobilization. The present inventors compared the difference between esterase-nanofibers and esterase-pristine nanofibers treated with the same amount of esterase and the same amount of nanofibers to evaluate the enzyme immobilization efficiency of the QD-encapsulated nanofibers. The reaction rate constants were investigated. After immobilization, enzyme aggregation on the surface of the nanofibers encapsulated with QD was confirmed using SEM microscopy. From Figures A, B, C, and D, the enzyme aggregated on the nanofibers was clearly visible. Because PS-PSMA nanofibers are hydrophobic, they float on the surface of the solution upon suspension in water, as can be seen on the left side of FIG. 7E. However, in the case of esterase-QDs-nanofiber complexes, the patch type of enzyme-QDs-nanofiber complexes sinks in the buffer as shown on the right side of FIG. 7E. Observed changes in their physical properties affect the efficiency of enzymatic aggregation. Table 1 shows the difference between the two types. Enzymes immobilized on QDs encapsulated nanofibers have too high V _max and lower K _m values compared to those of pristine nanofibers.

Table 1 summarizes the Lineweaver-Burke plot between the QD encapsulated esterase-nanofiber composites and the esterase-pristine nanofiber composites.

We measured the storage and regeneration stability of both types of nanofiber composites. 8 shows storage and regeneration stability in both cases, and the immobilized esterases are very stable in ten regeneration reactions or maintained their initial activity for more than 50 days. This may be due to the fact that potent enzyme aggregates inhibit the loss of enzymes into solution and are no more denaturing. The compactness of the QDs-nanofiber composites increases the efficiency of immobilization as most enzymes can aggregate and form strong crosslinks on the surface of the QDs-nanofibers. In conclusion, V _max is higher than that of nanofibers due to the higher amount of enzyme loading. Although V _max is higher, the aggregation of enzymes affects contact with the substrate and is accompanied by different modes of interaction by altered morphology and density in the buffer solution so that the K _m of the QDs-nanofiber complex is smaller than that of pristine. Lose.

As can be seen in the present invention, QDs were uniformly distributed and encapsulated in PS-PSMA nanofibers. The newly synthesized nanofibers were also electrically conductive. This conductivity is mainly due to the interaction between the QDs and the PSMA side chain. Subsequent experiments showed that these QD PS-PSMA nanofibers can be used to detect organic solvents having a reaction time of 1 second or less. Thus, these nanofibers can be used in gas sensing applications and have been shown in the present invention to have a fast reaction time and long durability.

The inventors have also successfully developed reformable nanofibers that impart high aspect ratios according to the stiffness induced using QDs in an electrospinning method without phase separation. The compactness of this nanofiber composite varies with the amount of QDs used when the QDs are uniformly distributed in the polymer matrix. This new type of QDs-nanofiber is well controlled in its manufacture and can easily be molded into the desired shape. The altered properties affect the efficiency of immobilized enzymes on nanofibers. Esterases immobilized on QDs-nanofibers are very stable and can be reused even with prolonged storage without loss of activity. Moreover, there is no decrease in its activity. These QDs-nanofibers of the patch type would be universally applicable to enzymes since immobilization increases its stability.

1 shows emission spectra (excitation wavelength at 350 nm) of PS-PSMA nanofibers and QDs PS-PSMA nanofibers.
2 is a) low density nonwoven 555 nm QDs PS-PSMA nanofibers; b) low density nonwoven 605 nm QDs PS-PSMA nanofibers; c) Fluorescence microscopy image of high density nonwoven 605 nm QDs PS-PSMA nanofiber sheet.
3 is a) PS-PSMA nanofibers; b) Iron oxide PS-PSMA nanofibers; c) AuNPs PS-PSMA nanofibers; d) SEM image of QDs PS-PSMA nanofibers.
4 is a) 1.5 mm x 1.0 mm Iron oxide PS-PSMA nanofibers; b) 1.5 mm x 1.0 mm AuNPs PS-PSMA nanofibers; c) 20 mm x 1.0 mm QDs PS-PSMA nanofibers; d) 10 mm × 1.0 mm QDs PS-PSMA nanofibers; e) 5 mm x 1.0 mm QDs PS-PSMA nanofibers; f) 3 mm × 1.0 mm QDs PS-PSMA nanofibers; g) IV characterization of 1.5 mm x 1.0 mm QDs PS-PSMA nanofibers.
FIG. 5 shows a) Chloroform b) DMF c) of 1 mg of PS-PSMA QD nanofibers in various concentrations of solvent using nitrogen as carrier gas by the 2-probe method at 5V contact distance at 5V in the presence of vapor. Figure showing current response.
Figure 6 is a figure showing the characteristics of PS-PSMA nanofibers encapsulated with QDs in the present invention. 6 (a) is a SEM image of PS-PSMA nanofibers, 6 (b) is PSD-PSMA nanofibers encapsulated with QD, and FIG. 6 (c) is a cross-sectional TEM image of PS-PSMA nanofibers encapsulated with QD. 6 (d) is a digital image of PS-PSMA nanofibers encapsulated with QD.
7 is an SEM image of an enzyme coating on the surface of QDs-nanofibers before esterase immobilization, (c) and (d) are images after immobilization, (e) pristine nanofibers and QD- after immobilization in buffer Digital image of nanofibers.
Figure 8 shows the stability of the esterase immobilized on the nanofibers, (a) 50 days storage stability of esterase-QDs-nanofiber composites, esterase-pristine nanofiber composites and esterase under free conditions, ( b) Figure 10 shows the reuse stability of esterase-QDs-nanofiber composites and esterase-pristine nanofiber composites. Relative activity was calculated using residual activity at each time point compared to that found initially at day zero.

The present invention will now be described in more detail by way of non-limiting examples. The following examples are intended to illustrate the invention and the scope of the invention is not to be construed as being limited by the following examples.

900,000, Pressure Chemical), Poly (styrene-co-maleic anhydride) (PSMA) (Mw

240,000, Aldrich), N, N-dimethylformamide (DMF) (99.8%, Sigma-Aldrich), Tetrahydrofuran (THF) (99.5%, Sigma-Aldrich), 클로로포름 (Aldrich), 및 CdSe/ZnS QDs ( 560/605 nm ). ZnS capped CdSe QDs(tri-n-octylphosphine oxide (TOPO) 및 octadecylamine (ODA) 표면 리간드로 코팅된)는 기존에 보고된 주지된 방법(J.Jack. Li, Y.A. Wang, W. Guo, J.C. Keay, T.D. Mishima, M.B. Johnson and X. Peng, J. Am. Chem. Soc. 125 (2003))을 사용하여 제조되었다. 10 nm 구연산 안정화된 금 나노입자는 전에 공개된 프로토콜(M.-D. Li, W.-L. Tseng and T.-L. Cheng, J. Chromatogr. A, 1216 (2009), 6451-6458.)을 사용하여 합성되었다. Polystyrene (PS) (Mw) used in the present invention

900,000, Pressure Chemical), Poly (styrene-co-maleic anhydride) (PSMA) (Mw

240,000, Aldrich), N, N-dimethylformamide (DMF) (99.8%, Sigma-Aldrich), Tetrahydrofuran (THF) (99.5%, Sigma-Aldrich), Chloroform (Aldrich), and CdSe / ZnS QDs (560/605 nm) ). ZnS capped CdSe QDs (coated with tri- n -octylphosphine oxide (TOPO) and octadecylamine (ODA) surface ligands) have been reported previously known methods (J. Jack. Li, YA Wang, W. Guo, JC Keay, TD Mishima, MB Johnson and X. Peng, J. Am. Chem. Soc. 125 (2003)). 10 nm citric acid stabilized gold nanoparticles are described in previously published protocols (M.-D. Li, W.-L. Tseng and T.-L. Cheng, J. Chromatogr. A, 1216 (2009), 6451-6458. Was synthesized.

Example  1: Electrospinning ( Electrospinning )

Each of 120 mg PS and 30 mg PSMA was added to a 24 mL (VWR) glass bottle. 2 mL of DMF was added to the glass bottle and the resulting solution was allowed to stand at room temperature for 2 hours. Then, 2 nmol quantum dots dissolved in 50 μl chloroform were added, and the glass bottle was sonicated at 28 ° C. for 1 hour. The solution was briefly vortexed and further sonicated at 28 ° C. for 30 minutes. A 1.5 mL aliquot of the prepared solution was loaded into 10 mL syringes respectively. The syringe needle (23 gauge) was held vertically with the clamp of the laboratory stand and the solution was electrospun using a Gamma high voltage Research (ES series). The calculated radial flow rate was fixed at 2.5 mL / hr, voltage was applied at 12 kV and the distance from tip to collector was 10 cm. Fixed square thermocon box collectors covered with aluminum foil were used to collect QDs PS-PSMA nanofibers.

Example  2: characterization

Fluorescence emission spectra were obtained with the help of Fluoromax4 fluorometer (Horiba Jobin Yvon, Japan) using an excitation wavelength of 350 nm UV light. A confocal scanning microscope (CLSM) and Zeiss Axiovert 200 microscope (equipped with Zeiss LSM 510 scanning device (Carl Zeiss Co. Ltd., Germany)) were used to examine the nanofibers by fluorescence microscopy. In order to excite the QDs present in the nanofibers, a 405-30 nm UV diode laser was used. Scanning electron microscopy (SEM) measurements were performed using S-2360N (Hitachi Co.) at a voltage of 10 kV.

The morphology of QDs-nanofibers was examined by scanning electron microscopy (SEM; S-2360N, Hitachi Co.). For TEM, QDs-nanofibers were mixed with Spurr resin (ERL 4221, DER®736, a mixture of NSA and DMAE, TedPella Inc.) and filled in polymerization for 8 hours. The filled resin was sliced to a thickness of 100 nm using ultramicrotome (XTXL, Boeckeler Instruments, Inc) and mounted on a 200 mesh copper grid. The grid was observed at 120 kV with a TEM (Tecnai 12, Philips, Eithoven, Netherlands) and images were acquired with a CCD camera (Multiscan 600W, Gatan).

Experimental Example  3: conductivity measurement

Sheet conductivity for 20 mm x 1 mm nanofiber composites was measured with a Keithley electrometer using a probe station (MS Tech, Korea). The contact was made using a probe station needle. The measurements were recorded using I-V graph software. The gas-sensitive properties of the composites were developed on-line for periodic changes between nitrogen gas (carrier gas) and organic vapors (Chloroform, DMF, THF) using a custom made instrumental setup consisting of two mass flow controllers connected to the gas chamber. The electrical reaction was recorded and investigated. Nanofibers were exposed to air at the end of the experiment to observe the drop in conductivity. Gas vapor reaction measurements were performed with a DAQPad-6015 (BNC-2090, National Instruments) connected to a PC via Preamp (1211, DL Instruments). The data was recorded in a LabVIEW program. The effects caused by exposure of the nanonananofiber composites to organic vapors were investigated by connecting gold coated crocodile clips to the ends of the 5 mm x 1 mm nanofiber composites in a closed glass chamber. The solvents used to generate the vapor were all analytical grade (99.9% purity).

Example  4: Nanofiber Phase Enzyme Immobilization

In order to prepare enzyme nanofiber composites, the present inventors used JH Lee, ET Hwang, BC Kim, SM Lee, BI Sang, YS Choi, J. Kim and MB Gu, Appl Microbiol Biot to construct stable esterase nanofiber composites. , 2007, 75 , 1301-1307, were made with some modifications to the protocol.

In summary, esterase solutions were prepared at 10 mg / mL in 100 mM phosphate buffer, pH 8.0. For incubation, QD-nanofibers were cut to 1 cm × 1 cm, mixed with 1 mL of enzyme solution in a glass bottle and vortexed at 200 rpm for 30 minutes at room temperature. The vial was then stirred at 60 rpm for 2 hours at 4 ° C. For enzymatic agglomeration, the enzyme was first agglomerated by adding a 2 mL solution containing 1.5 wt% gluteraldehyde and 0.5 g ammonium sulfate to the vial and stirred at 200 rpm for 2 hours at room temperature, followed by lacquer (30 rpm) at 4 ° C. Incubated overnight). The next day, discard all solutions and transfer the remaining enzyme-nanofiber complex coated with gluteraldehyde to a new glass bottle, wash briefly with 100 mM phosphate buffer, and remove the unbound functional groups on gluteraldehyde with 100 mM Tris-Cl (pH 7.8). Capping). After capping, the nanofiber complexes were washed three times with 10 mM phosphate buffer, pH 6.5. The prepared enzyme nanofiber complex was dispersed in 2 mL of 10 mM phosphate buffer (pH 6.5) and stored at 4 ° C. until further use.

Example  5: activity and stability measurements

The bioavailability of the enzyme-QDs-nanofiber complex was checked by monitoring the production of p-nitrophenol from hydrolysis of p-nitrophenyl butyrate dissolved in N, N-dimethylformamide. In summary, 1.98 mL of 100 mM phosphate buffer (pH 6.5) containing 20 μl of 50 mM p-nitrophenyl butyrate dissolved in N, N-dimethylformamide was prepared as a substrate. The QDs-nanofiber composite comprising the immobilized esterase was dispersed in the substrate solution and stirred at 200 rpm. After a short reaction, the initial activity was calculated from A400 nm vs time and the absorbance was calculated as the concentration of p -nitrophenol. For stability experiments, after measuring activity, the esterases immobilized on QD filled nanofibers were washed three times with 100 mM phosphate buffer (pH 6.5) and stored at room temperature for later use. The same experimental protocol was used when we measured the stability of esterase-nanofiber composites during repeated use. Esterase activity of one unit (U) was defined as the amount of enzyme that dissociates 1 μmol p -nitrophenol / min under assay conditions. All samples were repeated three times for error analysis. The standard deviation of the results is shown as an error bar on the graph.

Claims (7)

Polystyrene (PS) -poly (styrene-co-maleic hydride) nanofiber composite including Quantum Dot. Gas sensing sensor comprising the nanofiber composite of claim 1. The gas sensing sensor of claim 2, wherein the gas is a volatile organic solvent.  An enzyme-nanofiber complex in which an enzyme is immobilized on the nanofiber complex of claim 1. The enzyme-nanofiber complex according to claim 4, wherein the enzyme is esterase, chymotrypsin or lipase. Mix polystyrene (PS) and poly (styrene-co-maleic hydride) into the vessel,
To the vessel is added a mixed solvent of dimethylformamide (DMF), tetrahydrofuran or tetrahydrofuran and acetone, to which a quantum dot is added and mixed,
Method for producing a polystyrene (PS) -poly (styrene-co-maleic hydride) nanofiber composite comprising a quantum dot (Quantum Dot) comprising the step of electrospinning the prepared mixed solution. The polystyrene (PS) -poly containing a quantum dot (dot) characterized in that the mixing ratio of the polystyrene (PS) and poly (styrene-co-maleic anhydride) is 4: 1 weight ratio (Styrene-co-maleic hydride) A method of making a nanofiber composite.

Images