Radiation‐induced effects in gamma‐irradiated PLLA and PCL at ambient and dry ice temperatures

Abstract

The effect of c-rays sterilization at ambient (23 C) and at dry ice temperatures (À78 C) on two biodegradable semicrystalline polyesters, namely poly(L-lactide) (PLLA) and poly(e-caprolactone) (PCL), was studied. The radical processes generated by irradiation were investigated by electron paramagnetic resonance (EPR) spectroscopy, whereas postradiation changes were monitored for 5 months by scanning calorimetry, thermogravimetric analysis, and apparent viscosity measurements. It was confirmed that the radiation sterilization initiates degradation in both studied polymers, however, the effect is smaller in PCL than in PLLA, and that the range of changes might be limited by lowering temperature of the exposure to c-rays. Newly formed oxygen containing functional groups confirmed by EPR and thermogravimetric analysis methods are produced in the irradiated polyesters. In PCL, the process might give rise to thermally induced cross-linking via oxygen containing intermolecular bridges. During storage, in both irradiated materials, morphology determined by differential scanning calorimetry is changing -PCL ability toward crystallization decreases insignificantly, whereas in PLLA the tendency is opposite -on irradiation a contribution of crystalline phase is growing considerably, from 18 and 19% to 41 and 31% for PLLA irradiated at 23 C and at À78 C, respectively.

Influence of internal pore architecture on biological and mechanical properties of three‐dimensional fiber deposited scaffolds for bone regeneration

“…However, the same irradiation cross‐links the chains increasing weight average molecular weight ( M w ). Increase of M w might result in increase of stiffness and strength of the polymer …”

“…Increase of M w might result in increase of stiffness and strength of the polymer. 48,49 Scaffold with high open interconnected porous network stimulates and supports bone ingrowth as well as subsequent remodeling and maturation by providing optimal stiffness and external and internal geometrical shapes. 37,40 The cell study showed that pore shape and size play a significant role for seeding efficiency and proliferation.…”

Use of Two-Step Grafting to Fabricate Dual-Functional Films and Site-Specific Functionalized Scaffolds

“…These observations are likely due to a combination of factors: Swelling of the substrate by the monomer solution; the production of α-carbon radicals that are stabilized by the carbonyl groups in both PCL and PAA 40,41 while the β-radicals formed in methacrylates are less stable; 40 and the high G-value for decarboxylation of PAA. 42 With only limited solubility parameters available for the substrates investigated, the first point cannot be properly evaluated.…”

Electron-Beam Irradiation of the PLLA/CMS/β-TCP Composite Nanofibers Obtained by Electrospinning

“…The effect of ionizing radiation on PLLA has been reported by several authors, either by gamma or electron beam [26][27][28]. Commonly, irradiation agents, such as triallyl isocyanurate, were used to improve strength by crosslinking the polymer chain.…”