Chemical inactivators as sterilization agents for bovine collagen materials

The use of collagen as a biomedical implant raises safety issues with regard to viruses and prions. Specific chemical agents that inactivate prion infectivity could be applied to collagen implants. The physicochemical changes and the in vitro and in vivo biocompatibility of collagen treated by formic acid (FA), trifluoroacetic acid (TFA), tetrafluorethanol (TFE), and hexafluoroisopropanol (HFIP) were investigated. In addition, the effects of these treatments on nucleic acids incorporated in collagen were analyzed. The molecules of FA and, more important, of TFA remained within collagen. FA, TFA, and HFIP treatments modify the secondary structure of collagen, as shown by Fourier transform infrared spectroscopy, while TFE does not. Differential scanning calorimetry measurements showed a decrease in the denaturation temperature compared to untreated collagen. However, resistance to collagenase was modified only after HFIP treatment. In vitro, cell growth was not impaired; in vivo, implants induced a temporary inflammatory reaction that was prolonged with TFA and HFIP treatments. TFE and FA-treated collagen were thoroughly infiltrated by fibroblasts. On the other hand, FA and TFA resulted in extensive depurination of nucleic acids while HFIP and TFE did so to a lesser degree. Among the investigated chemical scrapie inactivators, FA treatment could offer a safe and biocompatible collagen-derived material for biomedical use.