Preparation of copper-chelate quaternized carboxymethyl chitosan/organic rectorite nanocomposites for algae inhibition

Rapid hemostatic antibacterial self-gelling powder based on methacryloylsulfonyl betaine and quaternized carboxymethyl chitosan

Hemostatic powders can be used for deep wounds and wounds with irregular shapes that are frequently inaccessible to traditional hemostatic dressings like hemostatic gauze, sponges, and foams. In this study, sulfobetaine methacrylate (SBMA) and quaternized carboxymethyl chitosan (QCCS) were combined to create an antibacterial hemostatic hydrogel through photopolymerization under green LED irradiation, which was then changed into PSBMA/QCCS powder. PSBMA/QCCS powder could quickly form hydrogel with strong wet adhesion. The internal structure, water absorption capacity, and adhesion properties of the powder were evaluated. The coagulation ability, antimicrobial properties, and biocompatibility of the powder were also characterized. The PSBMA/QCCS powder could aggregate blood cells and platelets to enhance hemostasis. Meanwhile, PSBMA/QCCS powder also showed effective antibacterial ability against both gram-positive bacteria (Staphylococcus aureus) and gram-negative bacteria (Escherichia coli). In summary, PSBMA/QCCS powder is a promising hemostatic agent with the characteristics of quick hemostasis, tough wet adhesion, satisfactory biocompatibility, considerable antibacterial effect, and adaptability to any irregularly shaped wounds.

Applications and perspectives of quaternized cellulose, chitin and chitosan: A review

Recently, increasing attention has been paid to natural polysaccharides for their low cost, biocompatibility and biodegradability. Quaternization is a modification method to improve the solubility and antibacterial ability of natural polysaccharides. Water-soluble derivatives of cellulose, chitin and chitosan offer the prospect of diverse applications in a wide range of fields, such as antibacterial products, drug delivery, wound healing, sewage treatment and ion exchange membranes. By combining the inherent properties of cellulose, chitin and chitosan with the inherent properties of the quaternary ammonium groups, new products with multiple functions and properties can be obtained. In this review, we summarized the research progress in the applications of quaternized cellulose, chitin and chitosan in recent five years. Moreover, ubiquitous challenges and personal perspectives on the further development of this promising field are also discussed.

Research progress of photocatalysis for algae killing and inhibition: a review

The healthy development of biodiversity has been threatened frequent water eutrophication. In recent years, photocatalytic technology, which has attracted researchers' attention, not only showed increasing potential in the field of organic pollutant degradation, but also many kinds of photocatalysts were used in the field of red tide pollution control at present, which showed superior ability to inactivate harmful algae and degrade algal toxins. Researches have also explored the mechanisms of photocatalytic algae inhibition. In this study, the current research progress in the field of photocatalytic algae inhibition was systematically discussed from several aspects, such as common types of photocatalysts, modification methods of photocatalysts, types of tested algae for photocatalytic algae inhibition, and action mechanism of inactivated algae cells, so as to provide a certain theoretical basis for further application research of photocatalysts in the field of algae removal in the later period.

Synthesis of Hydroxypropyltrimethyl Ammonium Chitosan Derivatives Bearing Thioctate and the Potential for Antioxidant Application

Hydroxypropyltrimethyl ammonium chloride chitosan (HACC) is one of the most important water-soluble chitosan derivatives; its derivatives have gained growing attention due to their potential biomedical applications. Here, hydroxypropyltrimethyl ammonium chitosan derivatives bearing thioctate (HACTs), with different degrees of substitution of thioctate, were prepared using HACC and α-lipoic acid as the reaction precursors, using an ion exchange method. The structural characteristics of the synthesized derivatives were confirmed by FTIR, ¹H NMR, and ¹³C NMR spectroscopy. In addition, their antioxidant behaviors were also investigated in vitro by the assays of reducing power, and scavenging activities against hydroxyl radicals and DPPH radicals. The antioxidant assay indicated that HACTs displayed strong antioxidant activity compared with HACC, especially in terms of reducing power. Besides, the antioxidant activities of the prepared products were further enhanced with the increase in the test concentration and the degrees of substitution of thioctate. At the maximum test concentration of 1.60 mg/mL, the absorbance value at 700 nm of HACTs, under the test conditions, was 4.346 ± 0.296, while the absorbance value of HACC was 0.041 ± 0.007. The aforementioned results support the use of HACTs as antioxidant biomaterials in food and the biomedical field.

Di-functional Cu2+-doped BiOCl photocatalyst for degradation of organic pollutant and inhibition of cyanobacterial growth

Photocatalytic oxidation of contaminants in water has recently gained extensive attentions. In this study, Cu²⁺-doped BiOCl microsphere photocatalysts were prepared using solvothermal method. The effects of Cu²⁺ doping ratio on the morphological structures and photoelectric and photocatalytic properties of BiOCl were studied in detail. Results showed that Cu²⁺ doping affected the particle size of BiOCl microspheres. The introduction of Cu²⁺ ions gradually increased the light absorption range and decreased the electron recombination rate of photocatalysts as shown by ultraviolet-visible diffuse reflection and photoluminescence spectra. The best doping ratio was 0.25 Cu²⁺-BiOCl, showing the highest photocatalytic activity for rhodamine B (14.25 time higher than BiOCl) and a good inhibition of algal growth. The main reactants in the photocatalytic system were·OH and h⁺ (electron holes). Density functional theory (DFT) calculations further demonstrated that the doping of Cu²⁺ ions made the photogenerated carriers in BiOCl easier to generate and ensured the charge was transferred more rapidly. In conclusion, a novel high-efficiency multifunctional photocatalyst is proposed for the efficient organic pollutants removal and algae growth inhibition from water.

Natural polysaccharides based self-assembled nanoparticles for biomedical applications - A review

In recent years, nanoparticles (NPs) derived from the self-assembly of natural polysaccharides have shown great potential in the biomedical field. Here, we described several self-assembly modes of natural polysaccharides in detail, summarized the natural polysaccharides mostly used for self-assembly, and provided insights into the current applications and achievements of these self-assembled NPs. As one of the most widespread substances in nature, most natural polysaccharides exhibit advantages of biodegradability, low immunogenicity, low toxicity, and degradable properties. Therefore, they have been fully explored, and the application of chitosan, hyaluronic acid, alginate, starch, and their derivatives has been extensively studied, especially in the fields of biomedical. Polysaccharides based NPs were proved to improve the solubility of insoluble drugs, enhance tissue target ability and realize the controlled and sustained release of drugs. When modified by hydrophobic groups, the amphiphilic polysaccharides can self-assemble into NPs. Other driven forces of self-assembly include electrostatic interaction and hydrogen bonds. Up to the present, polysaccharides-based nanoparticles have been widely applied for tumor treatment, antibacterial application, gene therapy, photodynamic therapy and transporting insulin.

Au@Carbon quantum Dots-MXene nanocomposite as an electrochemical sensor for sensitive detection of nitrite

A highly sensitive electrochemical sensor was developed through a one-pot green synthesis method for nitrite detection based on the electrochemical technique. Xylan-based carbon quantum dots (CQDs) were used as green in situ reducing agent to prepare CQDs capped gold nanoparticles (Au@CQDs). MXene of good electrical conductivity was used as the immobilized matrix to fabricate Au@CQDs-MXene nanocomposites with the advantages of good electrical conductivity and electrocatalysis. An electrochemical sensor for nitrite monitor was obtained by loading the Au@CQDs-MXene on a glassy carbon electrode. The sensor presents high sensitivity, good stability, wide linear range, and excellent selectivity due to the high catalytic activity of AuNPs and CQDs, the large specific surface area of MXene, and exceptional electrical conductivity of AuNPs and MXene. Under the optimal condition, the linear detection range of the sensor was from 1 μM to 3200 μM with a detection limit of 0.078 μM (S/N = 3), which was superior to most reported sensors using differential pulse voltammetry (DPV) method. Furthermore, this sensor was successfully applied to detect nitrite in tap water and salted vegetables with satisfactory recoveries. This modified electrocatalytic sensor shows a new pathway to fabricate nitrite detection sensor with feasibility for practical application.

Incorporation of Layered Rectorite into Biocompatible Core-Sheath Nanofibrous Mats for Sustained Drug Delivery

Searching for drug carries with controlled release and good biocompatibility has always been one of the research hotspots and difficulties. Herein, core-sheath nanofibrous mats (NFs) consisting of biocompatible poly(ethylene oxide) (PEO, core) and poly(l-lactic acid) (PLLA, sheath) for drug delivery were fabricated via coaxial electrospinning strategy. The nontoxic layered silicate rectorite (REC) with 0.5-1 wt % amount was introduced in the sheath for sustained drug delivery. Layered REC could be intercalated with PLLA macromolecule chains, leading to the densified structure for loading and keeping doxorubicin hydrochloride (DOX) while reversibly capturing and releasing DOX to delay the drug migration due to its high cation activity. The addition of REC in NFs could delay the initial burst release of DOX and prolong the residence time from 12 to 96 h. Moreover, DOX-loaded core-sheath NFs had in vitro culture with strong antitumor activity, which was confirmed by cytotoxicity results and live and dead assay. HepG₂ tumor-bearing xenograft further demonstrated the tumor-suppression effect and the excellent safety of the DOX-loaded core-sheath NFs in vivo. The constructed NFs as drug carriers showed great potential in the local treatment of solid tumors.

A review on functional polymer-clay based nanocomposite membranes for treatment of water

Water is essential for every living being. Increasing population, mismanagement of water sources, urbanization, industrialization, globalization, and global warming have all contributed to the scarcity of fresh water sources and the growing demand of such resources. Securing and allocating sufficient water resources has thus become one of the current major global challenges. Membrane technology has dominated the field of water purification due to its ease of usage and fabrication with high efficiency. The development of novel membrane materials can hence play a central role in advancing the field of membrane technology. It is noted that polymer-clay nanocomposites have been used widely for treatment of waste water. Nonetheless, not much efforts have been put to functionalize their membranes to be selective for specific targets. This review was organized to offer better insights into various types of functional polymer and clays composite membranes developed for efficient treatment and purification of water/wastewater. Our discussion was extended further to evaluate the efficacy of membrane techniques employed in the water industry against major chemical (e.g., heavy metal, dye, and phenol) and biological contaminants (e.g., biofouling).

Synthesis of promising nanocomposites from an antitumer and biologically active heterocyclic compound uploaded by clay and chitosan polymers

The innovative nanocomposites (NCs) of antibacterial and antitumor 2-amino-5-S-benzyl-1, 3, 4-thiadiazole (ABMT): binary (NC₁): ABMT-clay as well as the ternary (NC₂): ABMT-clay-chitosan have been prepared following the top-down approach method. The ABMT molecules have been efficiently uploaded on the inorganic polymer potassium montmorlinite clay polymer (MMT). The NC is homogenously dispersed in the aqueous solutions without crystallization of ABMT. However, the dispersity of the small particle size and the crystallinity of NC₁ is greatly enhanced in the presence of the biopolymer chitosan. The nanocomposites showed good non linear optical activity with suitable band gaps indicated the electron confinement in the NC. The loading and entrapment efficiency of ABMT onto MMT reached 89.3% in NC₁ during 6 h of contact time with the aqueous solution of pH 6.8. The enhanced redox characteristics of NC₁ relative to that of MMT suggested the better biological (antibacterial and antitumor) activity of NC₁. Chitosan enhanced the redox and the optical properties of NC₁ and its ability to undergo intercharge transfer to any acceptor sites. Hence, chitosan may added synergestic electron donation and, hence antitumor activity to the binary NC₁.

Water sorption, antimicrobial activity, and thermal and mechanical properties of chitosan/clay/glycerol nanocomposite films

Chitosan-based nanocomposites films with different clay loadings (0, 5, 10, 15 wt %), with (10, 20, 30 wt%) and without glycerol as plasticizer, were prepared by solution casting. The effects of the addition of clay and glycerol on the thermal, mechanical, water absorption, and antimicrobial activity properties of chitosan/clay nanocomposites films were investigated in this study. XRD results indicated that the intercalated structure was obtained in the chitosan/clay nanocomposites with and without glycerol. The thermal stability of the chitosan was significantly enhanced by the presence of clay and glycerol. It was found that the addition of clay into the chitosan improved significantly the tensile strength and tensile modulus. The highest values in strength and stiffness were achieved for the chitosal/clay nanocomposites with 5 wt% of clay and 20 wt% of glycerol. The addition of both clay and glycerol reduced drastically the ductility of chitosan. The best water resistance was obtained for the chitosan film containing 5 wt% of clay and 20 wt% of glycerol. The chitosan/clay nanocomposite film had potential for application of alternative food packing materials.

Chitosan capped copper oxide/copper nanoparticles encapsulated microbial resistant nanocomposite films

Chitosan (CH) capped inorganic nanomaterials have been considered as significant antibacterial materials in the clinical field. This work shows the synthesis of two new different antibacterial composite films as a result of the incorporation of CH capped copper oxide (CHCuO) and copper (CHCu) nanoparticles (NPs). Here, CHCuO and CHCu NPs were achieved by a facile chemical reduction of Cu²⁺ ions using sodium hydroxide and ascorbic acid. TEM analysis revealed the morphology as rod-type nanoflakes for CHCuO and a spherical shape for CHCu NPs with ~7 ± 2 nm size. Antimicrobial activity of the developed materials was studied by the inhibition zone method, against both gram-negative and gram-positive bacteria. The antimicrobial activity revealed that the CHCuO NPs and CHCuO-CH film showed a higher inhibition zone than the other nanomaterials. The results suggested that the synthesized materials can be used in wound dressing applications.

Green synthesis of antimicrobial and antitumor N,N,N-trimethyl chitosan chloride/poly (acrylic acid)/silver nanocomposites

The present study is imported to solve two critical problems we face in our daily life which are microbial pollution and colon cancer. One pot green synthesis of a water soluble polyelectrolyte complex (PEC) between cationic polysaccharide as N,N,N-trimethyl chitosan chloride (TMC) and anionic polymer as poly (acrylic acid) (PAA) in presence of silver nanoparticles to yield (TMC/PAA/Ag) nanocomposites with different Ag weight ratios. Structure of TMC, PAA and TMC/PAA (PEC) were proved via different analysis tools. TMC/PAA and its Ag nanocomposites are used as antimicrobial agents against different pathogenic bacteria and fungi to solve microbial pollution. TMC/PAA-Silver nanocomposites had the highest antimicrobial activity which increases with increasing Ag %. Cytotoxicity data confirmed also that TMC/PAA/Ag (3%) had the most cytotoxic effect (the less cell viability %) towards colon cancer. TMC/PAA (PEC) was formed through electrostatic interactions between N-quaternized (-N⁺R₃) groups in TMC and carboxylate (-COO^-) groups in PAA.