Liquefied chitin/polyvinyl alcohol based blend membranes: Preparation and characterization and antibacterial activity

Z-scheme heterojunction g-C3N4-TiO2 reinforced chitosan/poly(vinyl alcohol) film: Efficient and recyclable for fruit packaging

Nanoparticles-loaded bio-based polymers have emerged as a sustainable substitute to traditional oil-based packaging materials, addressing the challenges of limited recyclability and significant environmental impact. However, the functionality and efficiency of nanoparticles have a significant impact on the application of bio-based composite films. Herein, graphitic carbon nitride (g-C3N4) and titanium dioxide (TiO2) coupled photocatalyst (g-C3N4-TiO2) was prepared by one-step calcination and introduced into chitosan (CS) and polyvinyl alcohol (PVA) solution to fabricate g-C3N4-TiO2/CS/PVA green renewable composite film via solution casting method. The results demonstrated the successful preparation of a Z-scheme heterojunction g-C3N4-TiO2 with exceptional photocatalytic activity. Furthermore, the incorporation of heterojunction enhanced mechanical properties, water barrier, and ultraviolet (UV) resistance properties of the fresh-keeping film. The g-C3N4-TiO2/CS/PVA composite film exhibited superior photocatalytic antibacterial preservation efficacy on strawberries under LED light, with a prolonged preservation time of up to 120 h, when compared to other films such as polyethylene (PE), CS/PVA, g-C3N4/CS/PVA, and TiO2/CS/PVA. In addition, the composite film has good recyclability and renewability. This work is expected to have great potential for low-cost fruit preservation and sustainable packaging, which also contributes to environmental protection.

New thiadiazole modified chitosan derivative to control the growth of human pathogenic microbes and cancer cell lines

The emergence of multidrug-resistant microbes and the propagation of cancer cells are global health issues. The unique properties of chitosan and its derivatives make it an important candidate for therapeutic applications. Herein, a new thiadiazole derivative, 4-((5-(butylthio)-1,3,4-thiadiazol-2-yl) amino)-4-oxo butanoic acid (BuTD-COOH) was synthesized and used to modify the chitosan through amide linkages, forming a new thiadiazole chitosan derivative (BuTD-CH). The formation of thiadiazole and the chitosan derivative was confirmed by FT-IR, ¹H/¹³C-NMR, GC-MS, TGA, Elemental analysis, and XPS. The BuTD-CH showed a high antimicrobial effect against human pathogens Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Staphylococcus aureus, and Candida albicans with low MIC values of 25-50 μg ml^-1 compared to unmodified chitosan. The in-vitro cytotoxicity of BuTD-CH was evaluated against two cancer cell lines (MCF-7 and HepG2) and one normal cell (HFB4) using the MTT method. The newly synthesized derivatives showed high efficacy against cancerous cells and targeted them at low concentrations (IC₅₀ was 178.9 ± 9.1 and 147.8 ± 10.5 μg ml^-1 for MCF-7 and HepG2, respectively) compared with normal HFB4 cells (IC₅₀ was 335.7 ± 11.4 μg ml^-1). Thus, low concentrations of newly synthesized BuTD-CH could be safely used as an antimicrobial and pharmacological agent for inhibiting the growth of human pathogenic microbes and hepatocellular and adenocarcinoma therapy.

Rational Design of Photothermal and Anti-Bacterial Foam With Macroporous Structure for Efficient Desalination of Water

With the environmental deterioration and the rise in demand for sustainability, the lack of freshwater resources has emerged as a global concern. To address this issue, the desalination of water using solar evaporation is centered on as a promising approach. In this study, we designed a light and photothermal liquefied-chitin-based polyurethane foam to achieve efficient water evaporation benefiting from their powerful solar spectral absorption, low thermal conductivity, quick transportation of water, hierarchically porous structures, and anti-biofouling natures. Moreover, because of the introduction of nano-silver, the newly developed foam exhibits considerable antibacterial ability and improved photothermal performance. Notably, the low thermal conductivity of the foam can reduce the loss of absorbed solar heat, whereas its large porous structure provides a smooth water transport channel. More importantly, with the assistance of heat, polyacrylamide hydrogels adhering along with the pores rapidly absorb and desorb water molecules, promoting the evaporation of water and improving solar energy conversion efficiency. Ultimately, under irradiation by one sunlight, the proposed material demonstrated a water evaporation rate and solar photothermal conversion efficiency of 2.44 kg m-2 h-1 and 153.2%, respectively.

Manganese-doped ferrihydrite/cellulose/polyvinyl alcohol composite membrane: Easily recyclable adsorbent for simultaneous removal of arsenic and cadmium from soil

Simultaneous removal of arsenic (As) and cadmium (Cd) from soil has been a matter of great concern. In this study, manganese-doped ferrihydrite/cellulose/polyvinyl alcohol composite membranes were prepared via loading manganese-doped ferrihydrite on cellulose mesh and then wrapping with polyvinyl alcohol. The obtained composite membranes exhibited excellent mechanical properties and could be easily separated from soil. The adsorption capacities of Cd(II) and As(III) on the composite membrane were 11.11 mg/g and 72.08 mg/g respectively. After mixing the composite membrane with polluted soil at dosage of 0.3% (w/w), the removal efficiency of the toxicity characteristic leaching procedure leachable As and Cd reached 65% and 69% respectively with one cycle. The stability and reusability of composite membrane were demonstrated by no decrease in tensile strength and the retention of 94% and 96% of As(III) and Cd(II) removal efficiency respectively after four adsorption cycles. The prepared composite membrane had application prospect in the remediation of As and Cd co-polluted soil.

Adsorption properties of heavy metals and antibiotics by chitosan from larvae and adult Trypoxylus dichotomus

Chitosan was prepared by hydrothermal deacetylation from multi-step protein purification chitin based on Trypoxylus dichotomus, for treating heavy metals and antibiotics. Chitosan with higher deacetylation degree and lower molecular weight were synthesized. The adult chitosan was composed of nanofibers arranged more evenly, showing higher yield, thermal stabilities and antimicrobial properties. The adsorption capacities of Cu²⁺ and Fe³⁺ were 462 and 270 mg/g, lower than 934 mg/g of Pb²⁺. Levofloxacin and tetracycline hydrochloride adsorption capacity were 26 and 22 mg/g, lower than 67 mg/g of sulfamethoxazole. In addition, compared with single pollutants, the adsorption of sulfamethoxazole and Pb²⁺ can increase by 6% and 5% when they act as composite contaminants. The adsorption procedure can be well described by pseudo-second-order kinetics and Langmuir isothermal model, indicating it a homogeneous monolayer chemisorption. Therefore, the Trypoxylus dichotomus source chitosan prepared by hydrothermal deacetylation has potential applications in the adsorption of complex pollutants.

Facile production of chitin from shrimp shells using a deep eutectic solvent and acetic acid

High purity chitin was extracted from shrimp shells by a green, sustainable, and efficient one-pot approach using a deep eutectic solvent consisting of choline chloride and glycerol (ChCl–Gl) combined with a small amount of acetic acid. Under the conditions of an acetic acid concentration of 7.5 wt% and reaction temperature of 120 °C, the purity of isolated chitin was up to 96.1%, which was superior to that of 87.7% obtained by conventional chemical method. In addition, the viscosity-average molecular weight and crystallinity of the extracted chitin were revealed to be larger than for the latter. Moreover, the deep eutectic solvent could be recycled at least three times without losing the quality of the extracted chitin. This facile approach combining recyclable DES with a small amount of acetic acid was expected to be used for the green and sustainable production of chitin from shrimp shells.

High purity chitin was extracted from shrimp shells by a green, sustainable, and efficient one-pot approach using a deep eutectic solvent consisting of choline chloride and glycerol (ChCl–Gl) combined with a small amount of acetic acid.

Liquefaction of starch using solid-acid catalysts derived from spent coffee for the production of plasticized poly (vinyl alcohol) films

This paper reports a strategy for preparing polyether polyols from corn starch, with (i) a mixture of polyethylene glycol 400 and glycerin (7:3, w/w) as the liquefying solvent and (ii) a spent-coffee-derived solid-acid catalyst (SC-SAC) (1:10, w/w, SC-SAC/starch) at 433 K for 1.5 h, under which conditions the liquefaction yield exceeded 99 %. The SC-SAC was prepared via hydrothermal carbonization at 453 K for 12 h, followed by sulfonation with H₂SO₄ at 343 K for 10 h. The liquefied starch product (SLP) was then used to plasticize poly(vinyl alcohol) (PVA) films with various mixing ratios. The optimal 0.4 SLP/PVA blend film exhibited good mechanical properties (tensile strength 38.07 MPa, elongation at break 1199 %), good transparency, and excellent flexibility. The results highlight the possibility of using SLP/PVA films in the development of degradable packaging materials.

Exploration of Chitinous Scaffold-Based Interfaces for Glucose Sensing Assemblies

: The nanomaterial-integrated chitinous polymers have promoted the technological advancements in personal health care apparatus, particularly for enzyme-based devices like the glucometer. Chitin and chitosan, being natural biopolymers, have attracted great attention in the field of biocatalysts engineering. Their remarkable tunable properties have been explored for enhancing enzyme performance and biosensor advancements. Currently, incorporation of nanomaterials in chitin and chitosan-based biosensors are also widely exploited for enzyme stability and interference-free detection. Therefore, in this review, we focus on various innovative multi-faceted strategies used for the fabrication of biological assemblies using chitinous biomaterial interface. We aim to summarize the current development on chitin/chitosan and their nano-architecture scaffolds for interdisciplinary biosensor research, especially for analytes like glucose. This review article will be useful for understanding the overall multifunctional aspects and progress of chitin and chitosan-based polysaccharides in the food, biomedical, pharmaceutical, environmental, and other diverse applications.

Chitin and waste shrimp shells liquefaction and liquefied products/polyvinyl alcohol blend membranes

Ball-milled chitin was liquefied with an optimal yield of 92% under sulfuric acid in diethylene glycol (DEG) at 160 °C for 120 min. The resulting liquid mixture was roughly separated into two portions: the real products of the reaction (liquefied ball-milled chitin, LBMC) and the remaining unreacted DEG. LBMC was further mingled with polyvinyl alcohol (PVA) to prepare LBMC/PVA blend membranes. To promote the direct utilization of shellfishery waste, raw shrimp shells were used to replace chitin for the liquefaction and membrane preparation operations. Liquefied ball-milled shrimp shells (LBMS) and the corresponding LBMS/PVA blend membranes were obtained. After adding LBMC or LBMS, the mechanical, thermal, water content and antibacterial performance of blend membranes were significantly improved compared to pure PVA membrane. Surprisingly, all the measured properties of LBMC/PVA and LBMS/PVA blend membranes were comparable, and even some properties of the latter were slightly superior than those of the former.