Multifunctional cotton fabrics with novel antibacterial coatings based on chitosan nanocapsules and polyacrylate.

Chitosan is a cationic polysaccharide with intrinsic antimicrobial properties that can be used as an ecological alternative to develop functional materials to inhibit the proliferation of microorganisms. This work evaluates chitosan nanocapsules (CNs) as a self-disinfecting agent to provide bactericidal activity on cotton fabrics (CF), using polyacrylate to bind the CNs on the CF surface. The fabrics were characterized by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), contact angle (CA), moisture retention, and antimicrobial tests against Escherichia coli and Bacillus subtilis. The FTIR results showed new peaks related to chitosan structure, indicating the adequate fixation of the CNs on the cotton fibers. SEM images corroborated the polyacrylate binder's efficient adhesion, connecting the CNs and the cotton fiber surface. The CF surface properties were considerably modified, while CN/polyacrylate coating promoted antibacterial activity against the B. subtilis (gram-positive bacteria) for the developed wipe, but they do not display bactericidal effects against E. coli (gram-negative bacteria). Supplementary Information: The online version contains supplementary material available at 10.1007/s11998-023-00761-y.

Analysis of selective fluorescence for the characterization of microplastic fibers: Use of a Nile Red-based analytical method to compare between natural and synthetic fibers.

The scientific community has been focusing on studying and understanding the extent of damage caused by microplastics (MPs) to flora, fauna, and humans, including the environmental and health risks associated with them. MPs with different morphologies have been described in different environments, with fibers being the most common type regardless of the environment. Various methods have been used to analyze MPs. Analytical methodologies such as visual inspection, spectroscopic methods, and others currently used to study MPs are time-consuming, and only subjective results are obtained when these methods are used for sample analysis. Researchers have used various dyes, such as Nile Red (NR), a selective fluorescent stain, to differentiate the polymers from the other sample components and address these problems. Using such dyes helps distinguish polymer particles from other contaminants present in the samples. We aimed to study the analytical process, morphology, and wettability of synthetic (such as polyethylene and polypropylene) and natural (such as linen and cotton) fibers using NR to characterize the fibers. The fibers were fragmented manually, and the samples were prepared using a cryomicrotome. The prepared samples were subjected to different NR incubation times of 30 min, 24 h, and 168 h, and characterized under ultraviolet light using optical microscopy. We investigated the effect of NR on different fibers, and the samples selection using the fluorescence properties generated when the fibers adsorbed the NR dye. The wettabilities of the samples indicated that polyethylene and polypropylene were hydrophobic, while linen and cotton were hydrophilic. Both synthetic and natural fibers exhibited fluorescence properties in the presence of NR. This increased the complexity of executing the MP characterization process, indicating that combined methodologies and optical and chemical identification processes should be used to characterize plastic specimens efficiently. We summarize and discuss the results and findings and provide recommendations for future laboratory research on microplastic fibers focusing on (I) microplastic selection, (II) stain preparation, and (III) microplastic characterization.

Essential oils loaded-chitosan nanocapsules incorporation in biodegradable starch films: A strategy to improve fruits shelf life.

Thermoplastic starch (TPS) films filled with chitosan nanocapsules (CN) containing essential oils (EO) were prepared aiming active packaging. Two different EOs were studied: Ho wood (H) and Cinnamon (C). Besides, different capsules concentrations were investigated (1, 3, and 5 wt%), and the films were evaluated by chemical structure, thermal stability, crystallinity, water vapor permeability, antimicrobial assays, and potential application for strawberry packaging. The TPS/CN-Ho wood films showed a strong interaction between chitosan-starch, mainly for 3 and 5 wt%, confirmed by XRD. The FT-Raman spectra of TPS/CN-Cinnamon film indicated that Cinnamon EO quickly migrated to starch films, probably due to the new crystal structure, named C-type, affecting the film's water permeability. The addition of 1 and 3 wt% CN loaded with Ho wood or Cinnamon EO to the films decreased the water permeability. 3 wt% CN was the optimum concentration to inhibit the Escherichia coli or Bacillus subtillis growth on the films, confirming their biological activity. The films' preservation properties were evaluated using strawberries, and films with 1 or 3 wt% loaded-CN could extend the strawberries' shelf life without fungi contamination. The developed TPS films can be used as active food packaging or other films for biomedical or pharmaceutical applications.

Biodegradable gelatin composite hydrogels filled with cellulose for chromium (VI) adsorption from contaminated water.

Biopolymers are promising materials for water treatment applications due to their abundance, low cost, expandability, and chemical structure. In this work, gelatin hydrogels filled with cellulose in the form of pristine eucalyptus residues (PER) or treated eucalyptus residues (TER) were prepared for adsorption and chromium removal in contaminated water. PER is a lignocellulosic compound, with cellulose, hemicellulose, and lignin, while TER has cellulose as a major component. FT-Raman Spectroscopy and FTIR analysis confirmed the crosslink reaction with glutaraldehyde and indicated that fillers altered the gelatin molecular vibrations and formed new hydrogen bonds, impacting the hydrogels' crystalline structure. The hydrogen bond energy was altered by the cellulosic fillers' addition and resulted in higher thermal stability (~10 °C). Hydrogels presented a Fickian diffusion, where gelatin hydrogel showed the highest swelling ability (466%), and composites showed lower values with the filler content increase. The chromium adsorption capacity presented values between 12 and 13 mg/g, i.e., featuring an excellent removal capacity which is related with hydrogel crosslinked structure and fibers surface hydroxyl groups, highlighting gelatin hydrogel TER 5% with better removal capacity. The developed hydrogels were produced from biomacromolecules with low-cost and potential application in contaminated water.