Caspase­9 was involved in cell apoptosis in human dental pulp stem cells from deciduous teeth.

As one type of adult stem cells (ASCs), human dental pulp stem cells (HDPSCs) have several properties, including high proliferation rate, self­renewal capability, and multi­lineage differentiation. However, the apoptotic mechanism underlying the development of dental pulp cells remains unclear. In the present study, a significant increase of apoptosis was observed in HDPSCs from the deciduous teeth compared with that from adult permanent teeth. In addition, the occurrence of cytochrome c expression and mitochondrial­mediated apoptosis pathway activity in HDPSCs were confirmed by quantitative polymerase chain reaction, and western blotting. Although caspase­8 and caspase­9 showed higher expression in deciduous teeth than in adult permanent teeth, only the knockdown of caspase­9 via RNA interference in HDPSC cells exhibited a significant reduction in apoptosis, and caspase­3 expression and activity. All these results revealed that caspase­9 and activated caspase­3 predominantly regulates cell apoptosis in HDPSCs from deciduous teeth.

Preparation and characterization of genipin-cross-linked silk fibroin/chitosan sustained-release microspheres.

We report the effects of distinct concentrations of genipin and silk fibroin (SF):chitosan (CS) ratios on the formation of SF-CS composite microspheres. We selected microspheres featuring an SF:CS ratio of 1:1, encapsulated various concentrations of bovine serum albumin (BSA), and then compared their encapsulation efficiency and sustained-release rate with those of pure CS microspheres. We determined that the following five groups of microspheres were highly spherical and featured particle sizes ranging from 70 µm to 147 µm: mass ratio of CS:SF =1:0.5, 0.1 g or 0.5 g genipin; CS:SF =1:1, 0.05 g or 1 g genipin; and CS:SF =1:2, 0.5 g genipin. The microspheres prepared using 1:1 CS:SF ratio and 0.05 g genipin in the presence of 10 mg, 20 mg, and 50 mg of BSA exhibited encapsulation efficiencies of 50.16%±4.32%, 56.58%±3.58%, and 42.19%±7.47%, respectively. Fourier-transform infrared spectroscopy (FTIR) results showed that SF and CS were cross-linked and that the α-helices and random coils of SF were converted into ß-sheets. BSA did not chemically react with CS or SF. Moreover, thermal gravimetric analysis (TGA) results showed that the melting point of BSA did not change, which confirmed the FTIR results, and X-ray diffraction results showed that BSA was entrapped in microspheres in a noncrystalline form, which further verified the TGA and FTIR data. The sustained-release microspheres prepared in the presence of 10 mg, 20 mg, and 50 mg of BSA burst release 30.79%±3.43%, 34.41%±4.46%, and 41.75%±0.96% of the entrapped BSA on the 1st day and cumulatively released 75.20%±2.52%, 79.16%±4.31%, and 89.04%±4.68% in 21 days, respectively. The pure CS microspheres prepared in the presence of 10 mg of BSA burst release 39.53%±1.76% of BSA on the 1st day and cumulatively released 83.57%±2.33% of the total encapsulated BSA in 21 days. The SF-CS composite microspheres exhibited higher sustained release than did the pure CS microspheres, and thus these composite microspheres might function as a superior drug carrier.

[Preparation and characterization of genipin-crosslinked silk fibroin/chitosan controlled-release microspheres].

OBJECTIVE: To investigate the property of genipin-crosslinked silk fibroin(SF)/chitosan(CS) microspheres for slow releasing of bovine serum albumin (BSA). METHODS: BSA-loaded genipin-crosslinked SF/CS microspheres were prepared by emulsion cross-linking technique. The micropheres were observed for surface morphology and size distribution under scanning electron microscope (SEM), and X-ray diffractometry (XRD) and fourier transform infrared spectroscopy (FTIR) were used to analyze their structural characteristics. BCA method was used for determining the drug entrapment, loading rate and cumulative drug release in 21 days. RESULT: The microspheres were spherical and showed a smooth surface with an average diameter of 7.84∓0.97 µm. The drug entrapment efficiency of the microspheres was (50.16∓4.32)% with a drug loading ratio of (1.25∓0.11)% and a cumulative release of the total drug of (75.2∓2.53)% in 21 days. CONCLUSION: Genipin-crosslinked SF/CS microspheres have a high drug entrapment efficiency and possess good capacity of sustained drug release.