Kaiyong Cai

Poly(d,l-lactic acid) surfaces modified by silk fibroin: effects on the culture of osteoblast in vitro

The objective of this study was to modify the surface of poly(D,L-lactic acid) (PDLLA) with different molecular weight of silk fibroins, and assess the effects of the modified surfaces on the functions of rat osteoblasts cultured in vitro. The properties of the modified PDLLA surface and the control one were investigated by contact angle and electron spectroscopy for chemical analysis (ESCA). The former indicated the variation of hydrophilicity and the latter suggested that the modified PDLLA film using silk fibroin is enriched with nitrogen atoms. The biocompatibility of the PDLLA film may be altered and in turn affects the seeded cell functions. Therefore, attachment and proliferation of osteoblasts seeded on the modified PDLLA films and the control one were examined. Cell morphologies on these films were studied by scanning electron microscopy (SEM) and cell viability was evaluated by MTT assay. In addition, differentiated cell function was assessed by measuring the alkaline phosphatase (ALP) activity. These results suggest that the silk fibroin-modified PDLLA surface can improve the interaction between osteoblasts and the PDLLA films.

Influence of different surface modification treatments on poly(D,L-lactic acid) with silk fibroin and their effects on the culture of osteoblast in vitro.

The objective of this study was to investigate the efficiency of two treatments for poly(D,L-lactic acid) (PDLLA) surface modification using silk fibroin. one chemical treatment and one physical treatment: 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (WSC) and entrapment. The properties of control films, WSC-modified and entrapment-treated PDLLA films were investigated by water contact angle measurement and electron spectroscopy for chemical analysis (ESCA). The water-contact angle measurement indicated the change of hydrophilicity and the ESCA analysis suggested that the modified PDLLA film using silk fibroin became enriched with nitrogen atoms. The biocompatibility of PDLLA film might be altered, which in turn would affect the functions of cells that were seeded on it. Therefore, attachment and proliferation of osteoblasts that were seeded on modified PDLLA films and control films were examined. Cell viability was evaluated by the MTT assay and differentiated cell function was assessed by measuring alkaline phosphatase activity. These results suggested that silk fibroin was used to modify PDLLA surface via WSC and that entrapment could improve the interactions between osteoblasts and PDLLA films. The entrapment treatment was more effective thin WSC treatment to accomplish the goal of surface modification.

Rat osteoblast functions on the o-carboxymethyl chitosan-modified poly(D,L-lactic acid) surface.

In this study, the functions of rat osteoblasts on o-carboxymethyl chitosan-modified poly(D,L-lactic acid) (PDLLA) films were investigated in vitro. The surface characterization was measured by contact angle and electron spectroscopy for chemical analysis (ESCA). Cell adhesion and proliferation were used to assess cell behavior on the modified surface and control. The MTT assay was used to determined cell viability and alkaline phosphatase (ALP) activity was performed to evaluate differentiated cell function. Compared to the control films, cell adhesion of osteoblasts on o-carboxymethyl chitosan-modified PDLLA films was significantly higher (p < 0.05) after 6 and 8 h culture, and osteoblast proliferation was also significantly hlgher (p < 0.01) between 4 and 7 days. The MTT assay suggested cell viability of osteoblasts cultured on o-carboxymethyl chitosan modified PDLLA films was significantly greater (p < 0.05) than that seeded on control one, and the ALP activity of cells cultured on modified PDLLA films was significantly higher (p < 0.01) than that found on control. These results give the first evidence that o-carboxymethyl chitosan could be used to modify PDLLA surface for improving biocompatibility.

Study of microstructure and properties of HEC-g-AA/SiO2 organic-inorganic hybrid materials

HEC-g-AA/SiO2 hybrid materials are prepared through a graft copolymerization reaction between acrylic acid (AA) monomer and hydroxyethyl cellulose (HEC), in the presence of a silica sol. The microstructure and properties of the hybrid materials are characterized by Fourier transform infrared spectra (FTIR), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM), respectively. The results show that a rigid inorganic phase SiO2 is dispersed in flexible organic continuous phase uniformly. HEC-g-AA/SiO2 hybrid material has no obvious phase separation in the presence of the crosslinking agent. The thermal performances of HEC-g-AA/SiO2 are excellent, and the glass transition temperature (T g) increases with the increased amount of the crosslinking agent.

Modulation of osteoblast function using poly(D, L-lactic acid) surfaces modified with alkylation derivative of chitosan

Poly(D,L-lactic acid) (PDLLA) was modified with alkylated chitosan (N-butyl chitosan and N-cetyl chitosan), and the effects of modified films on the functions of rat osteoblasts were investigated. The characteristics of surfaces(both modified and control) were examined by water contact angle measurement and electron spectroscopy for chemical analysis (ESCA). Cell morphologies on these surfaces were taken using scanning electron microscopy (SEM). Cell attachment and proliferation were used to assess cell behavior on modified surface and control. MTT assay was used to determined cell viability, and alkaline phosphatase (ALP) activity was taken to evaluate differentiated cell function. Compared with the untreated films, no significant difference in cell attachment of osteoblasts was found on the modified films at a period of 8 h (p > 0.05). However, cell proliferation of N-butyl chitosan rather than N-cetyl chitosan modified PDLLA films was significantly higher than that found on control one (p < 0.05) at the end of the 4th and 7th days. The cell viability of osteoblasts on N-butyl chitosan modified PDLLA films were found higher than that on control (p < 0.05). These results suggested that N-butyl chitosan contributed greater than N-cetyl chitosan when used to modify PDLLA films for improving its biocompatibility.

CHITOSAN /GELATIN NETWORK BASED BIOMATERIALS IN TISSUE ENGINEERING

Tissue can be looked upon as a cell composite, where cell expresses its functions, while extra cellular matrixes (ECMs) secreted provide cell information and do its matrix functions. Here ECMs are, physical and chemical networks consisted of proteins (e.g. collagen, fibronectin, laminin and vitronectin etc.) and glycosaminoglycans (GAGs, e.g. hyaluronic acid, chodroitin 4-sulfate, chodroitin 6-sulfate etc.). The idea cell-carrier should be the one, which most mimics the ECM. Therefore, chitosan in which the N-acetylglucosamine moiety is a structural feature also found in the GAGs, and gelatin, the partially denatured derivative of collagen were used to develop hiomaterials. They will exhibit related bioactivities, as their analogue and precursor, respectively. Chitosan gelatin network based biomaterials can be applied as membrane, scaffold, surface modifier and non-viral vectorfor. DNA delivery in tissue engineering. Some of our activities were reported. These biomaterials have promising perspectives.