In-Situ Synthesis of Silver Nanoparticle within Self-Assembling Ultrashort Peptide Hydrogel as Antibacterial with Wound Healing Properties

Silver nanoparticles (AgNPs) are promising antimicrobial agents, but their synthesis often involves toxic reducing agents. To address this, we developed a green synthesis methodology employing an in-situ approach for synthesizing AgNPs within self-assembled ultrashort peptide hydrogels through photochemical synthesis, eliminating the need for toxic chemicals.

A novel tetrapeptide was designed and synthesized to form hydrogels in aqueous solutions. AgNPs were incorporated into the hydrogel via in-situ photochemical synthesis using sunlight. The hydrogel and AgNPs were characterized through spectroscopic and microscopic techniques. The antibacterial efficacy of the AgNP-loaded hydrogel was assessed against gram-positive and gram-negative bacteria, and its wound-healing potential in mammalian cell lines was evaluated.

Among the peptides synthesized, PHG-2 formed a hydrogel at a 1% w/v concentration in aqueous solution. Characterization using the gel inversion assay, circular dichroism (CD) spectroscopy, and transmission electron microscopy (TEM) revealed uniform nanofibril self-assembly. UV spectroscopy and TEM confirmed the formation of AgNPs within the hydrogel. While the peptide hydrogel exhibited moderate antibacterial activity alone, the AgNP-loaded hydrogel demonstrated synergistic antibacterial effects against methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli. A docking study of all the synthesized peptides was performed against FmtA (an enzyme for cell wall synthesis of MRSA) and results were correlated with the obtained docking score. The silver-loaded peptide hydrogel showed a twofold increase in antibacterial activity against MRSA compared to silver nitrate solutions. The hydrogel significantly promoted wound healing in HEK-293T and MCF-7 cells compared to the control.

This study introduces a novel ultrashort tetrapeptide sequence for developing antibacterial agents that are effective against infected wounds while supporting wound healing. Utilizing in-situ photochemical synthesis, the green synthesis approach provides an environmentally friendly and sustainable alternative to conventional methods.