Synthesis and Characterization of Quantum Dot ...

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Journal of Nanoscience and Nanotechnology Vol. 17, 2720–2723, 2017 www.aspbs.com/jnn

Synthesis and Characterization of Quantum Dot-Loaded Poly(lactic-co-glycolic) Acid Nanocomposite Fibers by an Electrospinning Process Seshadri Reddy Ankireddy and Jongsung Kim∗ Department of Chemical and Biological Engineering, Gachon University, Seongnam, Gyeonggi-Do 461-701, Korea Poly(lactic-co-glycolic) acid (PLGA) is one of the most successfully developed biodegradable polymers. PLGA is a copolymer of polylactic and glycolic acid. In this work, quantum dot (QD)-loaded PLGA nanofibers were fabricated via a simple one-step electrospinning process. The surface morphology of the fibers was characterized by scanning electron microscopy (SEM). It was shown that the PLGA nanofibers had both smooth and rough surfaces with an average fiber diameter of 150 ± 25 nm and 350 ± 60 nm for the PLGA and QD-loaded PLGA nanofibers, respectively. The needle size, applied voltage, and solvent flow rate in the syringe were maintained at 23 G, 20 kV, and 1.5 mL/h, respectively. The SEM analysis showed that nanofibers with a very thin and uniform size were formed and the InP/ZnS QDs were homogeneously loaded into the PLGA nanofiber matrix. TheDelivered thermal properties of to: the State PLGA-QD nanofibers were explored by thermogravimetric by Ingenta University of New York at Binghamton analysis (TGA) and differential scanning calorimetry (DSC). The surface chemical structure and IP: 95.181.218.177 On: Tue, 25 Apr 2017 13:29:22 functionalities were characterized by Fourier transform infrared (FTIR) spectroscopy and X-ray powCopyright: American Scientific Publishers der diffraction (XRPD).

Keywords: PLGA, QD-Loaded PLGA, Electrospinning, Tissue Engineering.

1. INTRODUCTION In the 21st century, the field of tissue engineering is one of the foremost, promising, and pioneering technologies. It uses a combination of cells and suitable biochemical materials for the growth of new connective tissues, which are implanted within the human body for various biological functions.1 Nanoscale materials, such as biomolecules, polymers, and organic and inorganic compounds have also been used in tissue engineering technology. Polymer-based nanofibers and nanoparticles are widely used carriers in the field of medicine.2 Biomaterials play an important role in tissue engineering by serving as 3-D synthetic frameworks (commonly referred to as scaffolds, matrices, or constructs) for cellular attachment, proliferation, and growth; this ultimately leads to new tissue generation. Synthetic materials, such as polylactic acid (PLA), polyglycolic acid (PGA), polycaprolactone (PCL), and poly(lactic-co-glycolic) acid (PGLA) are biocompatible and nontoxic polymers that are essential and powerful ∗

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tools for the multidisciplinary field of tissue engineering. Among them, PLGA is one of the most successfully used polymers for biomedical and clinical applications in tissue engineering because of its excellent biocompatibility and biodegradability.3 PLGA nanofibers are excellent nanocarriers that can be used as drug delivery vehicles in the field of nanobiotechnology.4 5 Nanofibers have been applied for the regeneration of musculoskeletal tissues for several reasons. Nanofibers are mainly used for various target tissues, such as heart, lung, liver, bone, and muscles because they mimic the extracellular matrices of tissues and organs.6–9 In recent years, several studies have been conducted on nanofibers and their applications for nanomedicine and tissue engineering. Nanoscale materials can be fabricated into different forms such as nanoparticles, nanofibers, nanospheres, nanotubes, and scaffolds. These nanostructures can be prepared using various biofabrication methods such as electrospinning, molecule self-assembly, electrospraying, spray drying, and phase separation. Among these methods, electrospinning is the most versatile tool for tissue regeneration applications.10 The electrospinning technique involves the use of high voltage to 1533-4880/2017/17/2720/004

doi:10.1166/jnn.2017.13357

Ankireddy and Kim

Synthesis and Characterization of Quantum Dot-Loaded PLGA Nanocomposite Fibers

induce the formation of a liquid jet. PLGA nanofibers are USA). The vortex mixing was performed using a vortex mixer (KMC-1300 V, Vision Scientific Co., Ltd., easily prepared by the electrospinning process; however, Korea). Fluorescence images were obtained using a fluvarious complex parameters are involved, such as the neeorescence microscope (Nikon, Japan). Tip syringes (BD dle gauge, applied voltage, solvent to polymer ratio, and 10 mL Luer-LokTM, Becton, Dickinson and Company, distance between the needle and fiber collector.11 Singapore) were used during the procedure. In recent years, much attention has been focused on the preparation of nanoparticle or polymer composite fibers 2.2. Preparation of QD-Loaded Electrospun by electrospinning with materials such as TiO2 /PPV12 and PLGA Nanofibers CdS/PVP.13 The properties of composite nanomaterials could be improved by novel strategies that involve the The QD-loaded PLGA nanofibers were prepared using an electrospraying system (NanoNC, Co., Ltd., Korea). incorporation of nanoparticles into fibers. TiO2 and CdS The electro-spraying device was equipped with a highQDs are harmful to the environment, and exhibit cytotoxivoltage direct current (DC) power supply and precision city when dissolved in a solvent via ionization.14 InP QDs fluid metering pump. Pure PLGA (50:50) pellets were disare extremely promising as they are not only cadmiumsolved in THF:DMF (1:3) solvent with a w/v ratio of free, but they are also structurally robust owing to the pres32% and magnetically stirred at room temperature for ence of covalent bonds between the component elements. 3 h. Approximately 1 mg of pure QDs were also added In this study, we used an electrospinning process to to the same mixture. The polymer solution was subseprepare PLGA and InP/ZnS QD-loaded PLGA nanofibers. quently loaded into a syringe and a high voltage electric The optical and chemical properties of the QD-loaded field (DC high voltage power supply, NanoNC Co., Ltd., PLGA were characterized using photoluminescence (PL), Korea) was applied to draw the ultra-fine fibers from the Fourier transform infrared (FTIR) spectroscopy, and X-ray 23 G needle onto the collector drum. The 23 G needle powder diffraction (XRPD). The thermal properties were was ground to form a flat tip to produce smooth and constudied using thermogravimetric analysis (TGA) and diftinuous nanofibers. A constant flow rate of 1.5 mL/h was ferential scanning calorimetry (DSC). The morphology of maintained using a syringe pump. A high voltage of 20 kV the PLGA and InP/ZnS QD-loaded PLGA nanofibers were was applied to the metallic needle, and a Teflon sheet characterized using scanning electron microscopy (SEM). was used to collect electrosprayed samples. The disDelivered byhave Ingenta University of New York atthe Binghamton To the best of our knowledge, there beento: noState reports tance between the nozzle IP: 95.181.218.177 On: Tue, 25 Apr 2017 13:29:22 and collector was set as 10 cm. published on the preparation of InP/ZnS QD-loaded PLGA Copyright: American Scientific Publishersprocess was performed under ambient The electrospinning nanofibers by an electrospinning process. conditions. The electrospun nanofibers were subsequently vacuum dried to aid the removal of any residual solvents 2. EXPERIMENTAL DETAILS within the fibers, and the nanofibers were stored in a refrig2.1. Materials and Instruments erator for further use. Poly(d,l-lactide-co-glycolide) (LA/GA 50/50, Mw = 36,000–70,000), tetrahydrofuran (THF), and N ,N 3. RESULTS AND DISCUSSION dimethylformamide (DMF) were purchased from SigmaA schematic representation of the van der Waals’ interacAldrich. InP/ZnS QDs in toluene (5 mg/mL, emission tions between the PLGA and InP/ZnS QDs is depicted in wavelength 625 nm) were purchased from Mesolight Figure 1. The morphological changes occurring on the sur(China). All the chemicals were used directly without face of the QD-loaded PLGA nanofibers were examined further purification. PLGA nanofibers were prepared using an electrospinning machine (NanoNC, Co., Ltd., Korea). The size and morphology of the PLGA nanofibers were characterized using a scanning electron microscope (SEM, S-4700, HITACHI, Japan) at an accelerating voltage of 20 kV. The fluorescence emission spectra of the QDs were obtained using a fluoroluminescence spectrometer (Quanta Master, Photon Technology International, NJ, USA) equipped with a xenon lamp (Arc Lamp Housing, A-1010B™ ), monochromator, and power supply (Brytexbox). The X-ray diffraction (XRD) patterns of the particles were obtained using an X-ray Automatic Diffractometer (Rigaku Rint 2200 Series, Rikagu, Tokyo, Japan. (Cu K radiation at a wavelength of 1.5406 Å)). The FTIR spectra were Figure 1. Schematic representation of van der Waals’ interactions recorded using a FTIR spectrometer (Vortex 70, Bruker, between PLGA and InP/ZnS QDs. J. Nanosci. Nanotechnol. 17, 2720–2723, 2017

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approximately 1748 cm−1 , and 1100–1130 cm−1 , corresponding to alkanes (CH, CH2 , CH3 stretching), C O stretching, and C–O stretching, respectively. The results from previous papers were used to identify the three characteristic regions and shifts of the PLGA.15 A needlelike peak at 1748 cm−1 was assigned to carbonyl stretching (C–O) in the –CO–O– group of the PLGA, and was observed to shift from 1748 cm−1 to 1778 cm−1 for the QD-loaded PLGA nanofibers. Another needle-like peak at 1165 cm−1 was attributed to C O group stretching vibrations in the CH–O– of the PLGA polymer chain; the same peak shifted to 1175 cm−1 for the QD-loaded PLGA nanofibers. The characteristic peaks at 1180 and 1082 cm−1 , corresponding to CO–O-stretching vibrations Figure 2. SEM images showing the morphology (a) PLGA and in the pristine polymer chain, were shifted to 1220 and (b) QD-loaded PLGA nanofibers; the rough surface areas are indicated by 1125 cm−1 for the QD-loaded PLGA nanofibers, respeccircles. Fluorescence images of QD-loaded PLGA nanofibers (c) under tively. All the characteristic peaks indicate that the QDs in bright field, and (d) under dark field microscopy. the PLGA nanofiber had bound together to form a more stable structure. by SEM. Figure 2(a) shows the smooth and flat surface of The XRD analysis was performed at 40 kV and 20 mA the pristine PLGA nanofibers. Figure 2(b) shows the rough in the range of 2 = 0 to 60 with a scanning speed surface of the PLGA upon incorporation of the QDs; the of 10 min−1 . Figure 4 shows the XRD pattern of the rough surface areas are indicated by circles. The figure PLGA and InP/ZnS QD-loaded PLGA nanofibers. The shows that the randomly oriented PLGA nanofibers have three strong peaks with 2 values of 27.59, 41.12, and smooth surfaces with an average fiber diameter of 150 ± 50.28 were attributed to the (111), (220), and (311) 25 nm, while the QD-loaded PLGA nanofibers have rough planes, respectively, on the cubic lattice of the InP/ZnS surfaces with an average fiber diameter of 350 ± 60 nm. QDs. The diffractogram for the PLGA nanofibers exhibby Ingenta to: prepared State University of New York at Binghamton The figure also shows Delivered that the diameter of the ited obvious peaks, which indicates the presence of an IP: 95.181.218.177 25no Apr 2017 13:29:22 nanofibers increased with the addition of the QDs. On: The Tue,amorphous structure. Copyright: American Scientific Publishers SEM analysis shows that nanofibers with a very thin and Figure 5 shows the PL spectra of the PLGA and QDuniform size were formed, and that the InP/ZnS QDs were loaded PLGA nanofibers. We measured the PL spectra homogeneously loaded into the PLGA nanofiber matrix. at various positions on the composite nanofibers and no Figure 2 also shows fluorescence microscopy images of the obvious changes were observed in the corresponding PL PLGA and QD-loaded PLGA nanofibers under (c) bright intensity; this indicates that the QDs were well dispersed field and (d) dark field modes; the QDs were uniformly in the nanofiber matrix. The figure shows that the pristine loaded into the PLGA nanofiber matrix. PLGA nanofibers exhibit an emission peak at 535 nm, the FTIR spectroscopy was performed to elucidate the InP/ZnS QDs exhibit an emission peak at 625 nm, and functional groups of the PLGA and QD-loaded PLGA the QD-loaded PLGA nanofibers show a broader emission nanofibers and their combinations. Peak shifting clearly peak at 620 nm. The full width at half maximum (FWHM) occurred, as shown in Figure 3. The FTIR spectra for from the emission peak in the nanofiber was 50 nm greater the PLGA shows absorption bands at 2850–3000 cm−1 , than that of the QDs because of the interaction of the

Figure 3. FTIR spectra of (a) PLGA and (b) QD-loaded PLGA nanofibers.

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Figure 4. XRPD pattern for the (a) PLGA and (b) QD-loaded PLGA nanofibers.

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and electric devices, such as light-emitting diode (LED) sensors, and biosensors for medical and tissue engineering applications. Acknowledgment: This work was supported by GRRC program of Gachon University (GRRC2015-B-01).

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Received: 31 December 2015. Accepted: 22 March 2016.

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