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Nanoparticles have been employed to develop nanosensors and drug carriers that accumulate in tumors. Thus, it is necessary to control the particle size, surface potential, and biodegradability of these nanoparticles for effective tumor accumulation and safe medical application. In this study, to form a nanoparticle platform suitable for diagnostic and drug delivery system (DDS) applications, peptides composed of aromatic amino acid residues were designed and synthesized based on the radiation crosslinking mechanism of proteins. The peptide nanoparticles, which were produced by γ-ray irradiation, displayed a positive surface potential, maintained biodegradability, and were stable in water and phosphoric buffer solution during actual diagnosis. The surface potential of the peptide nanoparticles could be changed to negative by using a fluorescent labeling reagent, so that the fluorescent-labeled peptide nanoparticles were uptaken by HeLa cells. The radiation-crosslinked nanoparticles can be applied as a platform for tumor-targeting diagnostics and DDS therapy. [ABSTRACT FROM AUTHOR]

The potential of a radiation crosslinking technique for developing gelatin scaffolds for tissue engineering was evaluated by comparing it with a chemical crosslinking method. Radiation-crosslinked gelatin exhibited higher visible light transmittance as compared to chemically crosslinked gelatin. The radiation crosslinking efficiency of the gelatin was estimated to be 91%; it was affected by hydroxyl (OH) radicals formed by γ-radiolysis of the aqueous gelatin solution under nitrous oxide or nitrogen-saturated conditions. The proportions of phenylalanine, tyrosine, and histidine in the gelatin decreased significantly with increasing absorbed dose. At the same time, the amounts of 12 other amino acids remained almost unchanged after γ-ray irradiation, and these amino acids did not participate in the crosslinking reactions. The contents of tyrosine, phenylalanine, and histidine in gelatin were the most important factors for radiation crosslinking. Cell adhesion of the radiation-crosslinked gelatin would be maintained before and after γ-ray irradiation because there was no decrease in the proportion of the cell adhesion active sequence (arginine-glycine-aspartic acid, RGD motif). The yield for dityrosine formation was estimated to be 0.030 µmol l−1 Gy−1, and this is considered to be the point at which crosslinking occurred in the radiation-crosslinked gelatin. As the crosslinked gelatin and degradation products have no absorption bands in the visible region, the radiation crosslinking technique, unlike chemically crosslinking techniques, can modify the gelatin while maintaining high transparency. • Radiation-crosslinked gelatin exhibits high transmittance of visible wavelengths. • The cell adhesion motif of crosslinked gelatin was maintained after irradiation. • Dityrosine was the main crosslinked point in radiation-crosslinked gelatins. [ABSTRACT FROM AUTHOR]