Jinping Suo

Physicochemical characterization and biocompatibility in vitro of biphasic calcium phosphate/polyvinyl alcohol scaffolds prepared by freeze-drying method for bone tissue engineering applications

In this study, a well developed porous biphasic calcium phosphate (BCP)/polyvinyl alcohol (PVA) scaffold was prepared by emulsion foam freeze-drying method possessed moderate inter-connected pores and porosity. The SEM analysis showed that BCP nano-particles could disperse uniformly in the scaffolds, and the pore size, porosity, and compressive strength could be controlled by the weight ratio of BCP/PVA. The in vitro degradation and cytocompatibility of scaffolds were examined in this study. The degradation analysis showed the prepared scaffolds have a low variation of pH values (approximately 7.18-7.36) in SBF solution, and have the biodegradation rate of BCP/PVA scaffolds decreased with the increase of PVA concentration. Moreover, MTT assay indicated that the BCP/PVA porous scaffold has no negative effects on cells growth and proliferation, and the hBMSCs possessed a favorable spreading morphology on the BCP/PVA scaffold surface. The inter-connected pore structure, mechanical strength, biodegradation rate and cytocompatibility of the prepared BCP/PVA scaffold can meet essential requirements for blame bearing bone tissue engineering and regeneration.

Preparation and properties of biphasic calcium phosphate scaffolds multiply coated with HA/PLLA nanocomposites for bone tissue engineering applications

A well-developed BCP scaffolds coated with multilayer of HA/PLLA nanocomposites with interconnectivity, high porosity, and moderate compressive strength as well as good biocompatibility were fabricated for bone tissue engineering. After being multiply coated with HA/PLLA nanocomposites, the scaffolds maintained the BCP framework structure, and the porous network structure of scaffolds remained unchanged; however, the compressive strength was increased with the increase of coating layer number of HA/PLLA nanocomposites. The prepared scaffolds showed lower variation of pH values in SBF solution, and an increase of coating layer number led to the decrease of the biodegradation rate at different days. Moreover, the multilayer coating scaffolds had good cytocompatibility, showing no negative effects on cells growth and proliferation. Furthermore, the bone-like apatite layer was built obviously in the interface of scaffold after 21 days after implantation in SD rat muscle. In conclusion, the BCP scaffold coated with multilayer of HA/PLLA nanocomposites could be a candidate as an excellent substitute for damaged or defect bone in bone tissue engineering.

Temperature-responsive biodegradable star-shaped block copolymers for vaginal gels

A novel biodegradable temperature-responsive copolymer, 4-arm star-shaped poly(D,L-lactic-co-glycolic acid)-b-methoxy poly(ethylene glycol) (4sPLGA-mPEG), was synthesized via the arm-first method. The copolymer solution of various concentrations was prepared to form vaginal gels at body temperature, in order to encapsulate different anti-HIV drugs, anti-inflammatory drugs or contraceptive drugs. The 4sPLGA-mPEG block copolymer solutions were liquid at room temperature and only the 4sPLGA-mPEG block copolymer solutions with a copolymer concentration from 20 to 40 wt% show a sol–gel transition as the temperature was increased. The viscosity change associated with the sol–gel phase transition depended on the copolymer concentration and DL-lactide/glycolide (LA/GA) mol ratio. The in vitro and in vivo biodegradation and biocompatibility of a thermogelling polymeric material were examined in this study. The degradation of the copolymer gel, proceeded by hydrolysis of ester bonds, was followed by the erosion of the gel in a simulated vaginal fluid solution at body temperature for nearly one month. Mass loss and reduction of the molecular weight were detected. The LA/GA mol ratio was found to significantly influence the degradation profiles. The rapid in vivo gel formation was confirmed after subcutaneous injection of the copolymer solution into Sprague-Dawley (SD) rats. The in vivo degradation was slightly accelerated compared to in vitro hydrolysis, and the persistence time of the injected hydrogels in vivo was found to be tuned by the LA/GA mol ratio. MTT assay and histological observations were used to examine the copolymer solution. Both in vitro and in vivo results illustrate acceptable biocompatibility of our materials. Collectively, our results show that the 4sPLGA-mPEG block copolymer is a promising candidate as a novel vaginal gel.

A detailed view of PLGA-mPEG microsphere formation by double emulsion solvent evaporation method

PLGA, mPEG diblock copolymer was synthesized by bulk ring-opening polymerization method. The double emulsion solvent evaporation method was used to prepare bovine serum albumin (BSA)-loaded microspheres. Optical microscopy was used to observe the whole microsphere fabrication process. It is confirmed that the proportion of inner aqueous phase is one of the most critical factors that determines the morphology of microspheres. Double emulsion droplets which have appropriate amount of inner aqueous phase can form closed and dense microspheres, while, too much inner aqueous phase will cause a collapse of the double emulsion droplets, resulting in a loss of drug. The proportion of inner aqueous phase was varied to prepare microspheres of different morphology. The results show that with increasing the amount of inner aqueous phase, a higher percent of broken microspheres and lower encapsulation efficiency appeared, and also, a more severe initial burst release and faster release rate.

Temperature-sensitive star-shaped block copolymers hydrogels for an injection application: phase transition behavior and biocompatibility

A series of star-shaped poly(d,l-lactic-co-glycolic acid)-b–methoxy poly(ethylene glycol) (PLGA–mPEG) block copolymers with varying PLGA/mPEG block weight ratios, mPEG block length, and arm numbers were synthesized and phase transition behaviors were investigated. Phase transition characteristics, such as critical gel concentration (CGC) and critical gel temperature (CGT), were closely related to the molecular structure of the star-shaped block copolymers. The CGC was mainly determined by the balance of hydrophobic PLGA and hydrophilic mPEG block (PLGA/mPEG block ratio). The CGTs showed a stronger dependence on mPEG block length and arm number. Also, the CGTs can be adjusted by adding mPEG homopolymer additives. The weight fraction of mPEG had a stronger influence on the CGT values than molecular weight of mPEG. In addition, the MTT assay and histological observations confirmed the acceptable biocompatibility of the star-shaped block copolymer. Hence, the star-shaped PLGA-mPEG block copolymer was a promising candidate as a novel injectable gel.