Abstract

It is critical for the clinical success to take the biological function into consideration when integrating the antibacterial function into the implanted biomaterials. To this aim, we prepared gentamycin sulfate (GS) loaded carboxymethyl-chitosan (CM-chitosan) hydrogel crosslinked by genipin. The prepared hydrogels not only achieved superb inhibition on bacteria growth and biofilm formation of Staphylococcus aureus, but also significantly enhanced the adhesion, proliferation and differentiation of MC3T3-E1 cells. The observed dual functions were likely based on the intrinsic property of the positive charged chitosan-based hydrogel, which could be modified to selectively disrupt the bacteria wall/membrane and promote cell adhesion and proliferation, as suggested by the membrane permeability study. The genipin concentration played an important role in controlling the degradation time of the chitosan hydrogel and the MC3T3-E1 cell responses. The loading of GS not only significantly increased the antibacterial efficiency but also was beneficial for the osteoblastic cell responses. Overall, the biocompatibility of the prepared chitosan-GS hydrogel could be tuned with both the genipin and GS concentrations, which control the available positive charged sites of chitosan. The results demonstrated that chitosan-GS hydrogel is an effective and simple approach to achieving combined antibacterial efficacy and excellent osteoblastic cell responses, which has great potential in orthopedic applications.

2.2.2. In vitro release of the GS

Cadherin, runt-related transcription factor-2 (Runx2), alkaline phosphatase (ALP) activity were determined using the quantitative enzyme-linked immunosorbent assay (ELISA) after 1, 3, 5, 7 days. The protein expressions were measured according to the instructions of the ELISA kits (ColorfulGene, Colorfulgene Biological Ltd., Wuhan, China) by the absorbance at 450 nm with a spectrophotometer (MK3, Thermo Electron Ltd., USA), compared against a calibration curve produced using a set of standard samples.