Innovative approaches in alginate grafting: Amino acids of RGD peptide composition for biomimetic and biocompatible...

This study explores strategies to enhance the bioactivity of alginate by grafting individual amino acids-arginine, glycine, and aspartic acid-and their combinations onto the alginate backbone. Inspired by the cell-adhesive RGD sequence, this biomimetic approach aims to systematically investigate individual contributions of each residue-an aspect rarely studied in isolation-while also assessing synergistic effects. This methodology provides a more accessible, reproducible alternative to improve the functional performance of biopolymers, avoiding high cost and synthetic complexity typically associated with full peptide conjugation. Using optimized carbodiimide-mediated coupling, a set of alginate-amino acid conjugates was synthesized and characterized by FTIR-ATR, ¹H NMR, and ¹³C NMR, focusing on improved hemocompatibility and solubility. Nanostructured films were assembled via layer-by-layer (LbL) deposition, enabling precise modulation of film architecture and allowing evaluation of cellular interactions. Among the conjugates, arginine-modified alginate (ALG-G-ARG) notably improved cell adhesion (PC-3 cells), demonstrating a 6.3-fold increase compared to unmodified alginate. The conjugate containing a mixture of grafted amino acids (MIX) exhibited similar results to arginine alone, suggesting observed bioactivity is mainly driven by arginine. This enhancement may be related to arginine's interactions with cell membrane receptors and hydrogen bonding capabilities. Minimal or nonspecific bioactivity was observed with glycine and aspartic acid individually; however, their charge, steric properties modestly affected cellular responses. Overall, these findings highlight the critical role of chemical modification in tuning alginate's biofunctionality. This work offers insights into the individual contributions of specific amino acids within a known bioactive motif, providing a rational basis for designing macromolecule-based biomaterials for tissue engineering and biomedical applications.