Characterization of alkali-treated collagen gels prepared by different crosslinkers.

We have developed a naturally-derived crosslinker named malic acid derivative (MAD). In the present study, we prepared alkali-treated collagen (AlCol) gels with different crosslinkers including MAD and commercially available crosslinkers such as 1-ethyl-3-(3('-dimethylaminopropyl) carbodiimide (EDC) and glutaraldehyde (GA). There are named as AlCol-MAD, AlCol-EDC, and AlCol-GA. We then compared their physicochemical properties. The residual amino groups in AlCol-MAD were not detected at MAD concentrations higher than 30 mM. On the other hand, the residual amino groups in AlCol-EDC and AlCol-GA were detected at crosslinker concentrations of 30 mM. The swelling ratios of AlCol-MAD, AlCol-EDC, and AlCol-GA decreased with increasing crosslinker concentration. Enzymatic degradation rate of AlCol-GA was slower than that of AlCol-MAD and AlCol-EDC. The cytotoxicity of MAD was clearly lower than that of EDC and GA. The number of adhered L929 on AlCol-MAD was higher than on AlCol-EDC and AlCol-GA after incubation for 1 day. After the culture for 3 and 7 days, excellent growth of L929 was observed on AlCol-MAD. These results suggested that MAD was excellent crosslinker for the reactivity with amino groups and cytocompatibility. Therefore, the resulting AlCol-MAD has potential for various biomedical applications like tissue engineering scaffolds and carrier for drug delivery systems.