Medical grade sterilization affects synthetic polymer film properties intended for peripheral nerve repair: an in vitro study.

In vitro characterization of synthetic scaffolds in the laboratory commonly employs sterilization techniques, such as, ultraviolet light or ethanol (EtOH) soaking. These sterilization methods are not sufficient, however, to gain Regulatory approval for therapeutic use. Neglecting the effects medical grade sterilization may have on material properties could lead to years of research never translating to the clinic. The objective of this study was to ascertain whether medical grade gamma irradiation affected the properties of solvent-cast poly(ε-caprolactone)/poly(D, L-lactic acid) blend films for peripheral nerve repair. Scaffolds were sterilized at eight incremental doses of Gamma radiation (0-45 kGy). With increasing radiation dose, tensile testing identified significant reductions in both maximum tensile strength (>40 %) and strain (>90 %); gel permeation chromatography showed a dose-dependent reduction in polymer molecular weight (>46 %) and differential scanning calorimetry highlighted an increase in crystallinity. NG108-15 nerve cells were cultured up to 7 days on gamma irradiated and EtOH soaked films (control). Scanning electron microscopy showed cells proliferated on all films during this time and confirmed cell morphology was unaffected by sterilization method. However, cellular proliferation and number were greater for gamma irradiated films compared to EtOH soaked. Despite material properties being significantly altered, the in vitro response was encouraging and gamma irradiation may prove effective for medical grade sterilization of films intended for peripheral nerve repair.