Antimicrobial and cytocompatible chitosan, N,N,N-trimethyl chitosan, and tanfloc-based polyelectrolyte multilayers on gellan gum films.

In this work free-standing gels formed from gellan gum (GG) by solvent evaporation are coated with polysaccharide-based polyelectrolyte multilayers, using the layer-by-layer approach. We show that PEMs composed of iota-carrageenan (CAR) and three different natural polycationic polymers have composition-dependent antimicrobial properties, and support mammalian cell growth. Cationic polymers (chitosan (CHT), N,N,N-trimethyl chitosan (TMC), and an amino-functionalized tannin derivative (TN)) are individually assembled with the anionic iota-carrageenan (CAR) at pH 5.0. PEMs (15-layers) are alternately deposited on the GG film. The GG film and coated GG films with PEMs are characterized by infrared spectroscopy with attenuated total reflectance (FTIR-ATR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and water contact angle (WCA) measurements. The TN/CAR coating provides a hydrophobic (WCA = 127°) and rough surface (Rq = 243 ± 48 nm), and the TMC/CAR coating provides a hydrophilic surface (WCA = 78°) with the lowest roughness (Rq = 97 ± 12 nm). Polymer coatings promote stability and durability of the GG film, and introduce antimicrobial properties against Gram-negative (Salmonella enteritidis) and Gram-positive (Staphylococcus aureus) bacteria. The films are also cytocompatible. Therefore, they have properties that can be further developed as wound dressings and food packaging.

Composite materials based on chitosan/gold nanoparticles: From synthesis to biomedical applications.

Conventional strategies (Turkevich's, and modified Turkevich's methods) often synthesize gold nanoparticles (AuNPs). These pathways produce AuNPs using toxic chemistries to reduce Au(III) and stabilize Au(0) atoms upon the AuNP surfaces. To overcome the disadvantages of conventional approaches, chitosan and chitosan-based materials associate with Au(III) to produce composites. Chitosan and derivatives reduce Au(III) and stabilize AuNPs, promoting biocompatibility to the composites, following approaches in-situ. In this review, we report methods to develop chitosan/AuNPs-based composites. The main criticism is about the mechanism of composite formation. Also, we highlight applications of chitosan/AuNPs-based devices in the biomedical arena. We report the synthesis of biosensors, drug delivery devices, scaffolds, antimicrobial coatings, and others. The major criticism is concerning the material design and the lack of data regarding the composite biocompatibility. We support a critical viewpoint.

Polysaccharide-based adsorbents prepared in ionic liquid with high performance for removing Pb(II) from aqueous systems.

Alginate/chitosan (ALG/CHT) and alginate/N,N-dimethyl chitosan (ALG/DMC) polyelectrolyte complex (PEC)-based adsorbents with high capacities for removing Pb(II) from aqueous systems are produced in [1-hydrogen-3-methylimidazolium hydrogen sulfate ionic liquid ([Hmim][HSO4-]). The [Hmim][HSO4-] is recovered, characterized by 1H NMR and reused to yield novel polysaccharide-based adsorbents. As-obtained PEC materials are characterized through infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and Zeta potential measurements. Kinetic and equilibrium adsorption studies reveal that the pseudo-second-order Kinetic, as well as the Redlich-Peterson isotherm, provide the best fits for the experimental data, respectively. CHT/ALG and DMC/ALG adsorbents promoted maximum adsorption capacities (qm) of 529.4 mg g-1 and 560.2 mg g-1, respectively. After adsorption, the materials are characterized by infrared spectroscopy and X-ray photoelectron spectroscopy, confirming that the chemisorption prevails upon Pb(II) removal. Also, PECs produced in the recovered [Hmim][HSO4-] have good capacities for removing Pb(II) ions from aqueous systems as well. This study showed that the [Hmim][HSO4-] is an alternative solvent to prepare novel and eco-friendly PEC-based adsorbents.

Chitosan/chondroitin sulfate hydrogels prepared in [Hmim][HSO4] ionic liquid.

[Hmim][HSO4] ionic liquid (IL) and bio-renewable sources as chitosan (CHT) and chondroitin sulfate (CS) were used to yield hydrogel-based materials (CHT/CS). The use of IL to solubilize both polysaccharides was considered an innovative way based on "green chemistry" principle, aiming the production of CHT/CS blended systems. CHT/CS hydrogels were carried out in homogeneous medium from short dissolution times. The hydrogels were characterized and achieved with excellent stabilities (in the 1.2-10pH range), larger swelling capacities, as well as devoid of cytotoxicity towards the normal VERO and diseased HT29 cells. The CHT/CS hydrogels carried out in [Hmim][HSO4] could be applied in many technological purposes, like medical, pharmaceutical, and environmental fields.