Electrolytically deposited carbonate apatite coating demonstrates higher strength but weaker support for bone marrow stromal cell attachment than do biomimetically deposited coatings. It is hypothesized that the incorporation of chitosan will increase the biocompatibility of electrolytic coating while maintaining its original strength. To verify this hypothesis, we formed a hybrid calcium phosphate/chitosan coating through electrodeposition. We found that the incorporation of chitosan influenced calcium phosphate formation and crystallization. Moreover, coating thickness and surface roughness decreased with increasing chitosan concentration. Hybrid coating exhibited an increased dissolution rate in both acidic and neutral simulated physiologic solution, whereas no significant difference on adhesive strength was found between the hybrid and original coatings (P > 0.05). Most importantly, the calcium phosphate/chitosan coating proved to be a more favorable surface for goat bone marrow stromal cell attachment than an unincorporated coating (P < 0.01). Considering its economic and simple production, a hybrid calcium phosphate/chitosan coating is thought to be an attractive candidate for future applications.

To improve cell attachment and to understand the effects of positive charge on the behavior of osteoblasts, 2-(methacryloyloxy)ethyl-trimethylammonium chloride (MAETAC), a positively charged monomer, was incorporated into poly(ethylene glycol)-diacrylate (PEGDA) hydrogel. The physicochemical properties of the resultant polymers, including the degree of acrylation of PEGDA, pKa of MAETAC, swelling ratio, zeta potential, and protein adsorption were investigated. Meanwhile, osteoblast-like MC3T3-E1 cells were seeded on the hydrogel to evaluate the effect of the positive charge on the behavior of the cells, including attachment, proliferation, and differentiation. The results revealed that PEGDA was synthesized with 90 percent of acrylation and MAETAC had been successfully incorporated into PEGDA. The pKa value of MAETAC was 9.4 determined by acid-based titration. The electrically charged nature of modified hydrogels was confirmed by zeta potential. With increasing concentration of MAETAC, the swelling ratio of the hydrogel in deionized water increased, while the swelling ratio stayed constant in phosphate buffer solution. The protein adsorption of the hydrogel also increased with increasing concentration of MAETAC. The modification of positive charge not only enhanced the attachment and proliferation of osteoblast-like MC3T3-E1 cells on the hydrogel, but also up-regulated alkaline phosphatase activity in the cells as well as gene expression of focal adhesion kinase and osteogenic markers, including collagen I, osteopontin, and osteocalcin. These findings indicate that the positively charged PEGDA may not only be a promising scaffold candidate for bone tissue engineering, but also a good platform to study the effect of positive charge on cell behavior due to the controllable charge density.