Platinum cross‐linked chitosan hydrogels synthesized in water saturated with CO₂ under high pressure

Abstract

The creation of biocompatible composite hydrogels from renewable biopolymers with stabilized functional platinum nanoparticles seems to be an important scientific task. The formation of such hydrogels in a unique medium of carbonic acid under high pressure CO 2 is promising due to its sterilizing ability under pressure, biocompatibility after decompression and environmental friendliness. In the present work, stable chitosan hydrogels with platinum nanoparticles were obtained in such solutions. The hydrogel nature of the composites was confirmed by rotational rheology. The physicochemical characteristics were studied using Fourier transform infrared, X-ray photoelectron, ultraviolet-visible spectroscopies, transmission electron, scanning electron and atomic force microscopies. It was found that nanoparticles of oxidized Pt of approximately 4.5 nm in size are stabilized by chitosan in the composite. The resulting chitosan/Pt hydrogels were also tested for antimicrobial activity and shown strong activity against Gram-positive bacteria (B. subtilis and B. coagulans) and slight activity against E. coli.

Effect of chitosan coating on polypropylene fibers on the deposition of copper ions

“…Presumably, most of cupric ions were deposited on the fibers in the form of a thin uniform nanolayer, and it can be concluded that the presence of chitosan on polypropylene fibers actually stabilizes the deposition and growth of cupric ion structures. We believe that amino‐ and hydroxyl‐groups of chitosan are responsible for the stabilizing interaction with cupric ion through chelation/complexation 25,26 . Indeed, according to the theory of hard and soft acids and bases, amino groups can be considered as ligands that have a greater affinity for transition metal cations 36 …”

“…We believe that amino-and hydroxyl-groups of chitosan are responsible for the stabilizing interaction with cupric ion through chelation/complexation. 25,26 Indeed, according to the theory of hard and soft acids and bases, amino groups can be considered as ligands that have a greater affinity for transition metal cations. 36 An EDS analysis was performed to confirm that the adsorbate on the fibers visible in the SEM images was indeed copper-containing one (Figure 5).…”

“…Chitosan coating increases the affinity of copper ions and reduces the possibility of large particles agglomeration 22–24 . Indeed, the amino‐ and hydroxyl‐groups of chitosan are interacting with transition metal ions via donor‐acceptor mechanism 25,26 . Generally, the preliminary modification with chitosan is carried out from acetic acid solutions.…”

“…[22][23][24] Indeed, the amino-and hydroxyl-groups of chitosan are interacting with transition metal ions via donor-acceptor mechanism. 25,26 Generally, the preliminary modification with chitosan is carried out from acetic acid solutions. However, a new method that explores deposition of chitosan coatings from a carbonic acid solution was recently proposed.…”

Water Saturated with Pressurized CO2 as a Tool to Create Various 3D Morphologies of Composites Based on Chitosan and Copper Nanoparticles

“…Another advantage of this medium is that the product formed in such a system is not contaminated with any traces of solvents, since the CO 2 spontaneously self-eliminates after decompression, while the resulting product remains in the water. Previously, chitosan solutions in the presence of carbonic acid have been used to develop composites based on chitosan and silver, platinum, and gold nanoparticles [ 38 , 39 , 40 ], but the possibilities of composites structure and form modification were not explored. It is also worth noting that copper is a transition metal, that differs somewhat from noble ones in its properties, which is why a detailed review of the characteristics of gels based on copper and chitosan is quite useful.…”