Antibacterial Activity of Novel Agent N-2-Hydroxypropyl Trimethyl Ammonium Chloride Chitosan against Streptococcus mutans.

Dental caries (DC) is one of the most common oral diseases and is mainly caused by Streptococcus mutans (S. mutans). The use of antibiotics against S. mutans usually has side effects, including developing resistance. N-2-Hydroxypropyl trimethyl ammonium chloride chitosan (N-2-HACC), a natural product, has great potential utility in antibacterial agents owing to its low toxicity and good biocompatibility. Thus, the purpose of the present study was to explore the antimicrobial activity of N-2-HACC against S. mutans through the permeability of the cell wall, integrity of cell membrane, protein and nucleic acid synthesis, respiratory metabolism, and biofilm formation. Our results confirmed that the MIC of N-2-HACC against S. mutans was 0.625 mg/mL with a 90.01 ± 1.54% inhibition rate. SEM observed the formation of cavities on the surface of S. mutans after 12 h N-2-HACC treatment. The level of alkaline phosphatase (AKP) activity was higher in the N-2-HACC treatment group than in the control group, indicating that N-2-HACC can improve the permeability of the cell wall. Also, N-2-HACC treatment can destroy the cell membrane of S. mutans by increasing conductivity and absorbance at 260 nm, decreasing cell metabolic activity, and enhancing the fluorescence at 488 nm. Respiratory metabolism revealed that the activities of the Na+-K+-ATP enzyme, pyruvate kinase (PK), succinate dehydrogenase (SDH), and malate dehydrogenase (MDH) were decreased after N-2-HACC treatment, revealing that N-2-HACC can inhibit glycolysis and the tricarboxylic acid cycle (TCA cycle) of S. mutans. Moreover, N-2-HACC can also decrease the contents of the nucleic acid and solution protein of S. mutans, interfere with biofilm formation, and decrease the mRNA expression level of biofilm formation-related genes. Therefore, these results verify that N-2-HACC has strong antibacterial activity against S. mutans, acting via cell membrane integrity damage, increasing the permeability of cell walls, interfering with bacterial protein and nucleic acid synthesis, perturbing glycolysis and the TCA cycle, and inhibiting biofilm formation. It is suggested that N-2-HACC may represent a new potential synthetically modified antibacterial material against S. mutans.

Antimicrobial Application of Chitosan Derivatives and their Nanocomposites.

Chitosan is derived from chitin polysaccharide, the main component of crustacean shells. Chitosan is a biocompatible, nontoxic, and biodegradable polymer soluble in acidic solutions. It is widely used in the medical and pharmaceutical fields. Antimicrobial activities of chitosan against different bacterial, fungal, and viral pathogens have been considered one of its attractive properties, making chitosan valuable for biological applications, including textile, food, tissue engineering, agriculture, and environmental protection. Additionally, chitosan has beneficial effects on livestock, poultry, fish, and crustaceans, which can enhance immunity, improve feed conversion, and promote growth. However, the water solubility of chitosan influences antimicrobial capabilities, limiting its application. In the present work, we reviewed the preparation, factors affecting antimicrobial activity, morphological structure, antimicrobial mechanism, and application of chitosan derivatives, and the problems and prospects were pointed out. Collectively, this review provided an update on the application of chitosan derivatives and their potential for further advanced applications in the antimicrobial field.

Immune enhancement of N-2-Hydroxypropyl trimethyl ammonium chloride chitosan/carboxymethyl chitosan nanoparticles vaccine.

The immunogenicity and toxicity of N-2-Hydroxypropyl trimethyl ammonium chloride chitosan/N, O-carboxymethyl chitosan nanoparticles (N-2-HACC/CMCS NPs) as a universal vaccine adjuvant/delivery system remains unclear. The present study indicated that the positively charged N-2-HACC/CMCS NPs showed a regular spherical morphology, with a particle size of 219 ± 13.72 nm, zeta potential of 37.28 ± 4.58 mV, had hemocompatibility and biodegradation. Acute toxicity, repeated dose toxicity, abnormal toxicity, muscle stimulation, whole body allergic reaction evaluation in vitro, and cytotoxicity in vivo confirmed N-2-HACC/CMCS NPs is safe and non-toxic. N-2-HACC/OVA/CMCS NPs were prepared to evaluate the immunogenicity, which showed a particle size of 248.1 ± 15.53 nm, zeta potential of 17.24 ± 1.28 mV, encapsulation efficiency of 92.43 ± 0.96 %, and loading capacity of 42.97 ± 0.07 %. Oral or intramuscular route with the N-2-HACC/OVA/CMCS NPs in mice not only induced higher IgG, IgG1, IgG2a, and sIgA antibody titers, but also significantly produced higher levels of IL-6, IL-4, IFN-γ, and TNF-α, demonstrating that the N-2-HACC/OVA/CMCS NPs enhance humoral, cellular, and mucosal immune responses. Our results not only support the N-2-HACC/CMCS NPs to be a safe and potential universal nano adjuvant/delivery system in vaccine development, especially mucosal vaccines, but also rich the database knowledge of adjuvant/delivery systems, and provide new direction to introduce more licensed adjuvants.

[Effects of microbial pretreatment of kenaf stalk by the white-rot fungus Pleurotus sajor-caju on bioconversion of fuel ethanol production].

Kenaf stalk was pretreated by the white-rot fungus Pleurotus sajor-caju incubated in solid-state kenaf stalk cultivation medium. Delignification and subsequent enzymatic saccharification and fermentation of kenaf stalk were investigated in order to evaluate effects of microbial pretreatment on bioconversion of kenaf lignocellulose to fuel ethanol production. The highest delignification rate of 50.20% was obtained after 25-35 days cultivation by P. sajor-caju, which could improve subsequent enzymatic hydrolysis efficiency of kenaf cellulose. And the saccharification rate of pretreated kenaf stalk reached 69.33 to 78.64%, 4.5-5.1 times higher than the control. Simultaneous saccharification and fermentation (SSF) with microbial-pretreatment kenaf stalk as substrate was performed. The highest overall ethanol yield of 68.31% with 18.35 to 18.90 mg/mL was achieved after 72 h of SSF.