Radiolysis Effect of the High Proportion of Ethanol in the Preparation of Albumin Nanoparticle

The effects of ionising radiation on proteins have been studied since the initial stages of this technology. These effects can be either direct or indirect, and many radical reactions are expected to occur according to the irradiation conditions and sample preparation. Recently, albumin nanoparticles have been prepared, for technological purposes, by irradiation of protein solutions in the presence of a high amount of ethanol.The radiation-induced crosslinking process in the protein nanoparticle preparation is a matter of study; therefore in the present work different experimental data and reported results are evaluated in order to discuss the radical reactions involved in this process.According to a quantitative analysis of solvent radiolysis, based on reported data and some key experimental determinations, the hydroxyethyl radicals and solvated electrons are the main radiolysis species present in the media. Selected free amino acids dissolved in water with a high amount of ethanol were gamma-irradiated to study the gradiation of modification by radiolysis, using UV-vis and fluorescence spectroscopy as well as HPLC-EIS-MS/MS. Amino acids such as alanine, tyrosine and phenylalanine showed a low degree of chemical modifications; meanwhile, histidine, cystine and tryptophan were modified by solvent radiolysis. Using SDS-PAGE, it is demonstrated the participation of reducible chemical bridges in the nanoparticle stabilisation. A prototypical model of the crosslinking process involved in albumin nanoparticle preparation is discussed in the base to (i) SDS-PAGE analysis of protein composition of albumin nanoparticle under reductive and non-reductive conditions; (ii) radiolysis effect onto some free amino acid solutions in the same experimental conditions; and (iii) analysis of reported studies of reductive radical stress onto albumin.