Abstract
Polyelectrolyte hydrogels bearing l-phenylalanine (PHE), l-valine (AVA), and l-histidine (Hist) residues were used as scaffolds for the formation of silver nanoparticles by reduction of Ag+ ions with NaBH4. The interaction with the metal ion allowed a prompt collapse of the swollen hydrogel, due to the neutralization reaction of basic groups present on the polymer. The imidazole nitrogen of the hydrogel with Hist demonstrated greater complexing capacity with the Ag+ ion compared to the hydrogels with carboxyl groups. The subsequent reduction to metallic silver allowed for the restoration of the hydrogel’s degree of swelling to the starting value. Transmission electron microscopy (TEM) and spectroscopic analyses showed, respectively, a uniform distribution of the 15 nm spherical silver nanoparticles embedded on the hydrogel and peak optical properties around a wavelength of 400 nm due to the surface plasmonic effect. Unlike native hydrogels, the composite hydrogels containing silver nanoparticles showed good antibacterial activity as gram+/gram− bactericides, and higher antifungal activity against S. cerevisiae.
Highlights
Today it is widely accepted that polymeric materials are extremely useful in various fields of science and technology
A series of polyelectrolyte hydrogels bearing α-amino acid residues (L-valine, L-phenylalanine, L -histidine), which better approximate the properties of biological tissues consisting of filamentous polyelectrolyte proteins, have been studied for many years (Scheme 1) [3,4,5]
As was to be expected, the N-acryloyl-L-phenylalanine (PHE) monomer exhibits no significant deviation of the titration curve in the presence and absence of silver ion (Figure 1) in the low pH range involving the ionization of the carboxylic group
Summary
Today it is widely accepted that polymeric materials are extremely useful in various fields of science and technology. Cross-linked polymers (hydrogels) play a fundamental role for various biomedical purposes due to their compatibility with soft tissues [1,2,3]. Hydrogels are materials capable of retaining a large amount of water inside their porous structure and are subject to deformation due to external triggers [3]; among these we can include direct stimuli (pH, temperature, ionic strength) or remote stimuli (alternating magnetic field, light). A series of polyelectrolyte hydrogels bearing α-amino acid residues L -histidine), which better approximate the properties of biological tissues consisting of filamentous polyelectrolyte proteins, have been studied for many years (Scheme 1) [3,4,5].
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