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. 2008;9(4):1110-8.
doi: 10.1208/s12249-008-9150-9. Epub 2008 Nov 7.

gamma-irradiation of PEGd,lPLA and PEG-PLGA multiblock copolymers: II. effect of oxygen and EPR investigation

R Dorati  1 , C Colonna, C Tomasi, I Genta, T Modena, A Faucitano, A Buttafava, B Conti
Affiliations

gamma-irradiation of PEGd,lPLA and PEG-PLGA multiblock copolymers: II. effect of oxygen and EPR investigation

R Dorati et al. AAPS PharmSciTech. 2008.

Abstract

The purpose of this research was to evaluate how the presence of oxygen can affect irradiation-induced degradation reactions of PEGd,lPLA and PEG-PLGA multiblock copolymers submitted to gamma irradiation and to investigate the radiolytic behavior of the polymers. PEGd,lPLA, PEG-PLGA, PLA, and PLGA were irradiated by using a (60)Co irradiation source in air and under vacuum at 25 kGy total dose. Mw and Mn were evaluated by gel permeation chromatography. The stability study was carried out on three samples sets: (a) polymer samples irradiated and stored in air, (b) polymer samples irradiated and stored under vacuum, and (c) polymer samples irradiated under vacuum and stored in air. The thermal and radiolytic behavior was investigated by differential scanning calorimetry and electron paramagnetic resonance (EPR), respectively. Samples irradiated in air showed remarkable Mw and Mn reduction and Tg value reduction due to radiation-induced chain scission reactions. Higher stability was observed for samples irradiated and stored under vacuum. EPR spectra showed that the presence of PEG units in multiblock copolymer chains leads to: (a) decrease of the radiolytic yield of radicals and (b) decrease of the radical trapping efficiency and faster radical decay rates. It can be concluded that the presence of oxygen during the irradiation process and the storage phase significantly increases the entity of irradiation-induced damage.

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Figures

Fig. 1
Fig. 1
Stability study of a PEGd,lPLA and b PLA polymers treated in different conditions: irradiated and stored in air (diamonds); irradiated and stored under vacuum (squares); irradiated under vacuum and then open to air (circles)
Fig. 2
Fig. 2
Stability study of a PEG-PLGA and b PLGA polymers treated in different conditions: irradiated and stored in air (diamonds); irradiated and stored under vacuum (squares); irradiated under vacuum and then stored in open air (circles)
Fig. 3
Fig. 3
EPR spectra of PLGA vs PLA after irradiation under vacuum at 77 K, recorded at 120 K and after temperature annealing at 290 K
Fig. 4
Fig. 4
EPR spectra of PEG homopolymer after irradiation under vacuum at 77 K, recorded at increasing of temperature from 120 to 298 K
Fig. 5
Fig. 5
a EPR spectra of PLGA vs PEG-PLGA (60 mol%) multiblock copolymer recorded at 120 K following irradiation at 77 K. Spectrum b shows the difference between PLGA and PEG-PLGA
Fig. 6
Fig. 6
EPR spectra of PEGd,lPLA (5 mol% of PEG) recorded as function of temperature after irradiation at 77 K
Fig. 7
Fig. 7
EPR spectra of PEG-PLGA (60mol% of PEG) recorded as function of temperature after irradiation at 77 K
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References

    1. European Medicines Agency. The use of ionizing radiation in the manufacture of medicinal products European Guidelines 3AQ4a. (1991).
    1. Loo J. S. C., Ooi C. P., C Boey F. Y. Degradation of poly(lactide-co-glycolide) (PLGA) and poly(L-lactide) (PLLA) by electron beam radiation. Biomaterials. 2005;26:1359–1367. doi: 10.1016/j.biomaterials.2004.05.001. - DOI - PubMed
    1. K. J. Hemmerich. Radiation sterilization, Polymer materials selection for radiation-sterilized products. Medical Device and Diagnostic Industry MDDI Feb. 2000, p. 78.
    1. Bushell J. A., Claybourn M., Williams H. E., Murphy D. M. An EPR and ENDOR study of gamma and beta-radiation sterilization in poly(lactide-co-glycolide) polymers and microspheres. J. Control. Release. 2005;110(1):49–57. doi: 10.1016/j.jconrel.2005.09.009. - DOI - PubMed
    1. Dorati R., Genta I., Montanari L., Buttafava A., Faucitano A., Conti B. The effect of γ-irradiation on PLGA/PEG microspheres containing ovalbumin. J. Control. Release. 2005;107:78–90. doi: 10.1016/j.jconrel.2005.05.029. - DOI - PubMed

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