Poly(ε‐caprolactone) Biomaterial Sterilized by E‐Beam Irradiation

Abstract

The effects of ionizing radiation (electron beam) on poly(epsilon-caprolactone) (PCL) were studied by analyzing changes in viscosity-average and weight-average molecular weight and radius of gyration, and by performing sol-gel analysis and swelling tests. Samples were irradiated under various conditions: solid and molten PCL in the presence or absence of air. The overall efficiency of crosslinking is higher for samples irradiated in the molten state than in the solid state, and is reduced in the presence of oxygen. Based on three kinds of experiments (molecular weight dependence on the dose in the pre-gelation region, sol-gel analysis, and swelling study), radiation-chemical yields of intermolecular crosslinking and scission were determined and are discussed in terms of the mechanism of radiation-induced reactions in PCL. Properties of the gels formed by high-dose irradiation and mechanical properties of irradiated PCL were analyzed. Irradiation causes an increase in the compression modulus of PCL. This process occurs at the pre-gelation stage and continues in the gel-containing system. We have demonstrated, for the first time, that irradiation of solid PCL is accompanied by a pronounced post-effect, which manifests itself by changes in the average molecular weight. EPR data indicate that this effect, at least in part, is caused by the presence of long-lived radicals trapped in the crystalline regions. Irradiation with the sterilizing dose does not cause a statistically significant change in the biocompatibility of PCL after subsequent storage for 79 d, as determined by preliminary osteoblast vitality tests.

Effect of electron beam irradiation on the silk fibroin fiber/poly(ε‐caprolactone) composite

“…Therefore, the signals of secondary alkylether radicals are dominant and the signals of peroxyl radicals are not visible. In Figure 6, the EPR spectrum of PCL150 is similar to the signals observed by Filipczak et al16 The spectrum represents the radicals formed by abstraction of the hydrogen atom at α‐site to an ester group. The hyperfine splitting may be assigned to two different radicals (CH 2 CH 2 CH • COO or COOCH • CH 2 CH 2 ).…”

“…The hyperfine splitting may be assigned to two different radicals (CH 2 CH 2 CH • COO or COOCH • CH 2 CH 2 ). Filipczak et al16 also discussed the role of oxygen in irradiation of PCL. Oxygen can prevent crosslinking by reacting with alkyl radicals of PCL to form peroxyl radicals, which were usually more stable than alkyl radicals and were able to initiate a variety of reaction pathways.…”

Shape-memory polymers as a technology platform for biomedical applications

“…Irradiation-based sterilization techniques such as gand e-beam sterilization are instantaneous, penetrating and nontoxic, but may be associated with changes in the molecular structure [55]. Irradiation, for instance, is known to reduce the glass temperature (T g ) and the molecular weight of PLG (80:20) and PCL (M w = 80 kDa) [56][57][58][59][60]. The molecular weight of PLG, which is known as a candidate material for SMP synthesis, decreases after g-irradiation, and this degradation process continues on storage for 4 weeks [57,58,61].…”

Biodegradable Elastomers for Biomedical Applications and Regenerative Medicine

“…In the case of photo-induced crosslinking, the biocompatibility of the initiators is a concern as well, but some photoinitiators have been shown to be well-tolerated by a range of mammalian cells [69]. Some biodegradable polymers can be chemically crosslinked by e-beam irradiation [70]. As discussed below, γ-irradiation of PTMC results in crosslinked, flexible and elastic networks [71].…”