Preparation, Characterization And In Vitro Degradation Of CdSe-ZnS Quantum Dots/Poly(Lactide-co-glycolide) Nanocomposites

In vivo studies of graft materials are generally made up of material preparation, in vitro experiments, in vivo experiments and clinical trials. Usually a large number of experimental animals are kept and then are executed by stages in vivo degradation experiments, in which needs a large number of test samples, sample preparation, supply of animals and cumbersome sample sectioning and staining works. Thus it extending the study period and increase the research costs. If materials were brought effective fluorescent labels such as quantum dots, in vivo degradation behavior can be dynamic monitored through the change of fluorescent effect in material, which can reduce the number of implants and surgical removal, and also avoids using of a large number of experiments animal and experimental samples. This article made the following studies on preparation and characterization of CdSe-ZnS QDs/PLGA nanocomposites and in vitro degradation behavior.1. In this study, CdSe-ZnS quantum dots(QDs)/Poly(lactide-co-glycolide)(PLGA-50/50) nanocomposites films, containing different concentration of CdSe-ZnS QDs, were prepared via the method of solution casting. The Fourier transform infrared spectroscopy(FTIR), transmission electron microscopy(TEM), UV-visible spectrophotometer(UV-Vis), fluorescence spectrophotometer(PL), thermal gravimetric analyzer(TGA) surface tension meter, Gel permeation chromatography(GPC), pH meter and digital camera were adopt to investigate the microstructure, macro-morphology, optical properties, thermal properties, hydrophilic properties and in vitro degradation behavior of the composites. The results showed that CdSe-ZnS QDs/PLGA nanocomposite can be successfully prepared through the solution casting method. The TEM pictures revealed that QDs were uniformly dispersed in the PLGA matrix when the mass fraction of quantum dots is below 3%, while partial agglomeration occurs after it goes to 4%. PL spectra and UV spectra explained that there was no effect to the optical properties of QDs after being composited with PLGA, whose intensities increased by augmenting the concentration of QDs in PLGA films. With the addition of the QDs, the thermal stability of PLGA gradually increased and the hydrophilic properties decreased to some extent. The result also showed that the degradation process of composites had close relationship with the change of fluorescent effect. Both the results of gel permeation chromatography and the pH of buffer solution of PLGA and QDs/PLGA nanocomposites films confirmed that the presence and uniform dispersion of QDs in the PLGA, to some extent, led to a faster degradation rate of the QDs/PLGA compared with unfilled PLGA. The molecular weight distribution narrowed gradually for the sake of degradation before experiment. The PL intensity of QDs/PLGA nanocomposites films decreased along with the degradation process. With the degradation time extends, pores and wrinkles began to emerge on the surfaces of the films and increased gradually; as a result, degradation debris fell from the films.2. In this study, CdSe-ZnS QDs/PLGA-75/25 nanocomposites films, containing different concentration of CdSe-ZnS QDs, were prepared via the method of solution casting. FTIR, TEM, UV-Vis, PL, TGA, GPC, pH meter and digital camera were adopt to investigate the microstructure, macro-morphology, optical properties, thermal properties and in vitro degradation behavior of the composites. PL spectra and UV-Vis spectra explained that there was no effect to the optical properties of QDs after being composited with PLGA, whose intensities increased by augmenting the concentration of QDs in PLGA films. The TEM pictures revealed that QDs were uniformly dispersed in the PLGA matrix. With the addition of the QDs, the thermal stability of PLGA was sharply declined. Both the results of GPC and the pH of buffer solution of PLGA and QDs/PLGA nanocomposites films confirmed that the presence and uniform dispersion of QDs in the PLGA, to some extent, led to a faster degradation rate of the QDs/PLGA compared with unfilled PLGA. The molecular weight distribution widened at first and narrowed soon afterwards, and then proved alternate variations until the end of degradation process. The PL intensity of QDs/PLGA nanocomposites films decreased along with the degradation process. With the degradation time extends, the films inflated gradually, pores and wrinkles began to emerge on the surfaces of the films, as a result, degradation debris fell from the films matrix. A large number of cracks occurred in films after being dried.To sum up, CdSe-ZnS QDs/PLGA nanocomposite with excellent luminescent properties and stable degradation performance has been successfully prepared through the solution casting method. If the quantitative relationship between fluorescence intensity and nanocomposite degradation process was built, it is expected to dynamically monitor the in vivo degradation behavior by detecting the change of the fluorescence effect of nanocomposites, which has potential application value in tissue engineering and life sciences.