Synthesis and antibacterial activities of quaternary ammonium salt of chitosan

Biomedical Applications of Quaternized Chitosan

The natural polymer chitosan is the second most abundant biopolymer on earth after chitin and has been extensively explored for preparation of versatile drug delivery systems. The presence of two distinct reactive functional groups (an amino group at C2, and a primary and secondary hydroxyl group at C3 and C6) of chitosan are involved in the transformation of expedient derivatives such as acylated, alkylated, carboxylated, quaternized and esterified chitosan. Amongst these, quaternized chitosan is preferred in pharmaceutical industries owing to its prominent features including superior water solubility, augmented antimicrobial actions, modified wound healing, pH-sensitive targeting, biocompatibility, and biodegradability. It has been explored in a large realm of pharmaceuticals, cosmeceuticals, and the biomedical arena. Immense classy drug delivery systems containing quaternized chitosan have been intended for tissue engineering, wound healing, gene, and vaccine delivery. This review article outlines synthetic techniques, basic characteristics, inherent properties, biomedical applications, and ubiquitous challenges associated to quaternized chitosan.

Formulation and Antibacterial Activity Evaluation of Quaternized Aminochitosan Membrane for Wound Dressing Applications

Much attention has been paid to chitosan biopolymer for advanced wound dressing owing to its exceptional biological characteristics comprising biodegradability, biocompatibility and respectable antibacterial activity. This study intended to develop a new antibacterial membrane based on quaternized aminochitosan (QAMCS) derivative. Herein, aminochitosan (AMCS) derivative was quaternized by N-(2-Chloroethyl) dimethylamine hydrochloride with different ratios. The pre-fabricated membranes were characterized by several analysis tools. The results indicate that maximum surface potential of +42.2 mV was attained by QAMCS3 membrane compared with +33.6 mV for native AMCS membrane. Moreover, membranes displayed higher surface roughness (1.27 ± 0.24 μm) and higher water uptake value (237 ± 8%) for QAMCS3 compared with 0.81 ± 0.08 μm and 165 ± 6% for neat AMCS membranes. Furthermore, the antibacterial activities were evaluated against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus cereus. Superior antibacterial activities with maximum inhibition values of 80–98% were accomplished by QAMCS3 membranes compared with 57–72% for AMCS membrane. Minimum inhibition concentration (MIC) results denote that the antibacterial activities were significantly boosted with increasing of polymeric sample concentration from 25 to 250 µg/mL. Additionally, all membranes unveiled better biocompatibility and respectable biodegradability, suggesting their possible application for advanced wound dressing.

Reviewing Chitin/Chitosan Nanofibers and Associated Nanocomposites and Their Attained Medical Milestones

Chitin/chitosan research is an expanding field with wide scope within polymer research. This topic is highly inviting as chitin/chitosan's are natural biopolymers that can be recovered from food waste and hold high potentials for medical applications. This review gives a brief overview of the chitin/chitosan based nanomaterials, their preparation methods and their biomedical applications. Chitin nanofibers and Chitosan nanofibers have been reviewed, their fabrication methods presented and their biomedical applications summarized. The chitin/chitosan based nanocomposites have also been discussed. Chitin and chitosan nanofibers and their binary and ternary composites are represented by scattered superficial reports. Delving deep into synergistic approaches, bringing up novel chitin/chitosan nanocomposites, could help diligently deliver medical expectations. This review highlights such lacunae and further lapses in chitin related inputs towards medical applications. The grey areas and future outlook for aligning chitin/chitosan nanofiber research are outlined as research directions for the future.

A Versatile Method for Preparing Polysaccharide Conjugates via Thiol-Michael Addition

Polysaccharide conjugates are important renewable materials. If properly designed, they may for example be able to carry drugs, be proactive (e.g., with amino acid substituents) and can carry a charge. These aspects can be particularly useful for biomedical applications. Herein, we report a simple approach to preparing polysaccharide conjugates. Thiol-Michael additions can be mild, modular, and efficient, making them useful tools for post-modification and the tailoring of polysaccharide architecture. In this study, hydroxypropyl cellulose (HPC) and dextran (Dex) were modified by methacrylation. The resulting polysaccharide, bearing α,β-unsaturated esters with tunable DS (methacrylate), was reacted with various thiols, including 2-thioethylamine, cysteine, and thiol functional quaternary ammonium salt through thiol-Michael addition, affording functionalized conjugates. This click-like synthetic approach provided several advantages including a fast reaction rate, high conversion, and the use of water as a solvent. Among these polysaccharide conjugates, the ones bearing quaternary ammonium salts exhibited competitive antimicrobial performance, as supported by a minimum inhibitory concentration (MIC) study and tracked by SEM characterization. Overall, this methodology provides a versatile route to polysaccharide conjugates with diverse functionalities, enabling applications such as antimicrobial activity, gene or drug delivery, and biomimicry.

Enhancement of Nano-Biopolymer Antibacterial Activity by Pulsed Electric Fields

Chronic wounds are commonly colonized with bacteria in a way that prevents full healing process and capacity for repair. Nano-chitosan, a biodegradable and nontoxic biopolymer, has shown bacteriostatic activity against a wide spectrum of bacteria. Effectively, pulsed electromagnetic fields are shown to have both wound healing enhancement and antibacterial activity. This work aimed to combine the use of nano-chitosan and exposure to a pulsed electric field to overcome two common types of infectious bacteria, namely P. aeruginosa and S. aureus. Here, bacteria growing rate, growth kinetics and cell cytotoxicity (levels of lactate dehydrogenase, protein leakage and nucleic acid leakage) were investigated. Our findings confirmed the maximum antibacterial synergistic combination of nano-chitosan and exposure against P. aeruginosa than using each one alone. It is presumed that the exposure has influenced bacteria membrane charge distribution in a manner that allowed more chitosan to anchor the surface and enter inside the cell. Significantly, cell cytotoxicity substantiates high enzymatic levels as a result of cell membrane disintegration. In conclusion, exposure to pulsed electromagnetic fields has a synergistic antibacterial effect against S. aureus and P. aeruginosa with maximum inhibitory effect for the last one. Extensive work should be done to evaluate the combination against different bacteria types to get general conclusive results. The ability of using pulsed electromagnetic fields as a wound healing accelerator and antibacterial cofactor has been proved, but in vivo experimental work in the future to verify the use of such a new combination against infectious wounds and to determine optimum treatment conditions is a must.

Endothelium-Mimicking Surface Combats Thrombosis and Biofouling via Synergistic Long- and Short-Distance Defense Strategy

Thrombosis and infections are the main causes of implant failures (e.g., extracorporeal circuits and indwelling medical devices), which induce significant morbidity and mortality. In this work, an endothelium-mimicking surface is engineered, which combines the nitric oxide (NO)-generating property and anti-fouling function of a healthy endothelium. The released gas signal molecules NO and the glycocalyx matrix macromolecules hyaluronic acid (HA) jointly combine long- and short-distance defense actions against thrombogenicity and biofouling. The biomimetic surface is efficiently fabricated by cografting a NO-generating species (i.e., Tri-tert-butyl 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetate-chelated Cu²⁺ , DTris@Cu) and the macromolecular HA on an aminated tube surface through one-pot amide condensation chemistry. The active attack (i.e., NO release) and zone defense (i.e., HA tethering) system endow the tubing surface with significant inhibition of platelets, fibrinogen, and bacteria adhesion, finally leading to long-term anti-thrombogenic and anti-fouling properties over 1 month. It is envisioned that this endothelium-mimicking surface engineering strategy will provide a promising solution to address the clinical issues of long-term blood-contacting devices associated with thrombosis and infection.

Study on polysaccharide polyelectrolyte complex and fabrication of alginate/chitosan derivative composite fibers

Sodium alginate (SA) blending with quaternary ammonium chitosan (QAC) polysaccharide polyelectrolyte complex (PEC) system was chosen to research the binary blending of anionic and cationic polyelectrolytes in detail and to fabricate SA/QAC composite fibers. The potential charge and the rheology of the PEC solution were characterized through Zeta Laser Particle Size Analyzer and DV-C Rotary Rheometer, the structure and properties of the composite fiber were examined by FT-IR, XRD, SEM, EDS, and YG004 single fiber strength meter. The results showed that as the mass ratio of SA to QAC increased from 0/1 to 10/1, the state of the binary solution in water changed from transparent uniform solution to turbid solution with flocculent precipitate, then back to uniform solution, accompanied by the electrical potential change. Moreover, the electrical potential also depended on salt in solution. By using this uniform PEC solution with the mass ratio of SA to QAC 10/1 and concentration 5.5 wt% in water, SA/QAC composite fibers with excellent performances of breaking strength 2.37 cN·dtex^-1 and breaking elongation 14.11%, good antibacterial and hydrophobic properties were fabricated via green wet-spinning process. The FT-IR and EDS determination indicated there formed egg-box between SA and Ca²⁺, cross-linked network between glutaraldehyde(GA) and SA, QAC, respectively. Depending on its mechanical, natural, and antibacterial properties, the SA/QAC composite fiber has advantages in wound dressing, medical gauze, medical absorbable suture, and tissue engineering.

Carbon-Based Nanomaterials: Promising Antiviral Agents to Combat COVID-19 in the Microbial-Resistant Era

Therapeutic options for the highly pathogenic human severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing the current pandemic coronavirus disease (COVID-19) are urgently needed. COVID-19 is associated with viral pneumonia and acute respiratory distress syndrome causing significant morbidity and mortality. The proposed treatments for COVID-19 have shown little or no effect in the clinic so far. Additionally, bacterial and fungal pathogens contribute to the SARS-CoV-2-mediated pneumonia disease complex. The antibiotic resistance in pneumonia treatment is increasing at an alarming rate. Therefore, carbon-based nanomaterials (CBNs), such as fullerene, carbon dots, graphene, and their derivatives constitute a promising alternative due to their wide-spectrum antimicrobial activity, biocompatibility, biodegradability, and capacity to induce tissue regeneration. Furthermore, the antimicrobial mode of action is mainly physical (e.g., membrane distortion), characterized by a low risk of antimicrobial resistance. In this Review, we evaluated the literature on the antiviral activity and broad-spectrum antimicrobial properties of CBNs. CBNs had antiviral activity against 13 enveloped positive-sense single-stranded RNA viruses, including SARS-CoV-2. CBNs with low or no toxicity to humans are promising therapeutics against the COVID-19 pneumonia complex with other viruses, bacteria, and fungi, including those that are multidrug-resistant.

Tuning the Surface Properties of Poly(Allylamine Hydrochloride)-Based Multilayer Films

The layer-by-layer (LbL) method of polyelectrolyte multilayer (PEM) fabrication is extremely versatile. It allows using a pair of any oppositely charged polyelectrolytes. Nevertheless, it may be difficult to ascribe a particular physicochemical property of the resulting PEM to a structural or chemical feature of a single component. A solution to this problem is based on the application of a polycation and a polyanion obtained by proper modification of the same parent polymer. Polyelectrolyte multilayers (PEMs) were prepared using the LbL technique from hydrophilic and amphiphilic derivatives of poly(allylamine hydrochloride) (PAH). PAH derivatives were obtained by the substitution of amine groups in PAH with sulfonate, ammonium, and hydrophobic groups. The PEMs were stable in 1 M NaCl and showed three different modes of thickness growth: exponential, mixed exponential-linear, and linear. Their surfaces ranged from very hydrophilic to hydrophobic. Root mean square (RMS) roughness was very variable and depended on the PEM composition, sample environment (dry, wet), and the polymer constituting the topmost layer. Atomic force microscopy (AFM) imaging of the surfaces showed very different morphologies of PEMs, including very smooth, porous, and structured PEMs with micellar aggregates. Thus, by proper choice of PAH derivatives, surfaces with different physicochemical features (growth type, thickness, charge, wettability, roughness, surface morphology) were obtained.

Molecular Machinery Responsible for Graphene Oxide's Distinct Inhibitory Effects towards Pseudomonas aeruginosa and Staphylococcus aureus Pathogens

Graphene oxide flakes are considered as potential inhibitors for different pathogenic bacteria. However, the efficacy of inhibition changes for different types and strains of bacteria. In this work, we examine Pseudomonas aeruginosa and Staphylococcus aureus, two common hospital-acquired infections, which react quite differently to graphene oxide flakes. The minimum inhibitory tests yield two distinct outcomes: stopped proliferation for S. aureus versus almost no effect for P. aeruginosa. Integrating our experimental evidence with molecular dynamics simulations, we elucidate the molecular machinery involved, explaining the behavior we see in scanning electron microscopy images. According to our simulations, the peptidoglycan network, the outermost layer of S. aureus, is completely entangled with the flakes, acting as a hunting ground, which consequently results in the inhibition of the pathogen itself. Lipopolysaccharides, the outermost layer of P. aeruginosa, on the other hand, resist interacting with the flakes. Lipopolysaccharides make no effective contacts, and thus no effective inhibition of the pathogen takes place. Likewise, the electron microscopy images show complete coverage and wrapping of S. aureus. In contrast, for P. aeruginosa, barely any bacteria are spotted with any flakes on top except for some loosely half-covered cases. As we did not observe any damaged bacteria in our images, we exclude the knife-cutting inhibition mechanism and suggest the wrapping and trapping mechanism for S. aureus for our flakes' rather large size (average area of 0.05 μm2). The molecular machinery suggested in this work can be used for molecular engineering and functionalizing graphene flakes to inhibit different pathogens.

Preparation and characterization of an imogolite/chitosan hybrid with pyridoxal-5′-phosphate as an interfacial modifier

Imogolite/chitosan hybrid films were prepared using pyridoxal-5′-phosphate (PLP) as an interfacial modifier. Thermogravimetric analysis and spectroscopic measurements revealed that the phosphate group of PLP was adsorbed on the imogolite. Furthermore, rheological measurements suggested that the PLP-modified imogolites (PLP–imogolite) had strong interactions with chitosan in solution. Moreover, UV absorption of the hybrid film showed that PLP and chitosan formed Schiff base linkages. Therefore, the hybrid films exhibited a significant improvement in their mechanical properties compared to those of pristine chitosan/imogolite hybrid films.

An eco-friendly hybrid film of chitosan and imogolite was prepared using pyridoxal-5′-phosphate as a surface modifier.

Antimicrobial effect of insect chitosan on Salmonella Typhimurium, Escherichia coli O157:H7 and Listeria monocytogenes survival

The antimicrobial capability of chitosan from Tenebrio molitor as compared with chitosan from crustacean (Penaeus monodon) on different pathogenic microorganisms of concern in food safety was studied. The antimicrobial effect was tested at pH 5 and pH 6.2 and at two different initial concentrations (10³ or 10⁶ CFU/mL). Results indicated that chitosan from both sources have antimicrobial activity, although the effect depended on the microorganism considered (Salmonella Typhimurium, Listeria monocytogenes and Escherichia coli O157:H7). Our results indicated that Salmonella was the most resistant bacteria, and that chitosan from insect was less active than chitosan from crustacean, especially against Salmonella. Another important factor on antimicrobial activity was the pH of the sample. When chitosan was added to a solution with a pH of 6.2 it was more active against Listeria and Escherichia coli, than at pH 5.00. Besides, the effect of chitosan appears to decrease with the incubation time, since some increases in counts were observed on E. coli and Salmonella after the 24 and 49 hours of incubation.

A review on chitosan and its development as pulmonary particulate anti-infective and anti-cancer drug carriers

Chitosan, as a biodegradable and biocompatible polymer, is characterized by anti-microbial and anti-cancer properties. It lately has received a widespread interest for use as the pulmonary particulate backbone materials of drug carrier for the treatment of infectious disease and cancer. The success of chitosan as pulmonary particulate drug carrier is a critical interplay of their mucoadhesive, permeation enhancement and site/cell-specific attributes. In the case of nanocarriers, various microencapsulation and micro-nano blending systems have been devised to equip them with an appropriate aerodynamic character to enable efficient pulmonary aerosolization and inhalation. The late COVID-19 infection is met with acute respiratory distress syndrome and cancer. Chitosan and its derivatives are found useful in combating HCoV and cancer as a function of their molecular weight, substituent type and its degree of substitution. The interest in chitosan is expected to rise in the next decade from the perspectives of drug delivery in combination with its therapeutic performance.

Antimicrobial and antioxidant properties of chitosan and its derivatives and their applications: A review

In this era, there is a global concern in the use of bioactive molecules such as chitosan in the field of antimicrobial and antioxidant benefits. Because of its biodegradability, biological compatibility, antimicrobial, antioxidants activity, and high safety, chitosan could be used in a large number of applications. It could exist in many forms, such as fibers, gels, films, sponges, nanoparticles, and beads. The different biological activities of chitosan and its products are extensively investigated to broaden the application fields in several areas. Chitosan's natural properties depend strongly on water and other solvent solubility. Consequently, the chitosan oligosaccharides with a low polymerization degree are getting significant attention in the pharmaceutical and medical applications because they have lower viscosity and higher water solubility than chitosan. The objective of this review article is to put the antioxidant and antimicrobial properties of chitosan and its derivatives under the spotlight. The impacts of chitosan on physicochemical parameters like molecular weight and deacetylation degree on its bioactivities are also identified. Additionally, other applications of chitosan and its derivatives, including wound healing products, wastewater treatment, and cosmetics, have also been highlighted.

Ionic Hydrogen-Bonded Organic Frameworks for Ion-Responsive Antimicrobial Membranes

Functionalization of hydrogen-bonded organic frameworks (HOFs) for specific applications has been a long-lasting challenge in HOF materials. Here, an efficient way to integrate functional species in the HOF structure through constructing an anionic framework is presented. The obtained HOFs, taking PFC-33 (PFC = porous materials from FJIRSM,CAS) as an example, integrate a porphyrin photosensitizer as a porous backbone and a commercial biocide as counterions in the structure. The permanent channels and the electrostatic interaction between the framework and the counterions provide PFC-33 ion-responsive biocide-release behavior in various physiological environments, thus exhibiting synergistic photodynamic and chemical antimicrobial efficiency. The unbonded carboxyl groups residing on the HOF surface further allow for manipulating the interfacial interaction between the PFC-33 and the polymer matrix for membrane fabrication. Therefore, a polyHOF membrane with high stability, desired flexibility, and good permeability is obtained, which demonstrates noticeable bacterial inhibition toward Escherichia coli. This study may shed light on the functionalization of HOF materials for broad application potentials.

Potential biofilm control strategies for extended spaceflight missions

Biofilms, surface-adherent microbial communities, are associated with microbial fouling and corrosion in terrestrial water-distribution systems. Biofilms are also present in human spaceflight, particularly in the Water Recovery System (WRS) on the International Space Station (ISS). The WRS is comprised of the Urine Processor Assembly (UPA) and the Water Processor Assembly (WPA) which together recycles wastewater from human urine and recovered humidity from the ISS atmosphere. These wastewaters and various process streams are continually inoculated with microorganisms primarily arising from the space crew microbiome. Biofilm-related fouling has been encountered and addressed in spacecraft in low Earth orbit, including ISS and the Russian Mir Space Station. However, planned future missions beyond low Earth orbit to the Moon and Mars present additional challenges, as resupplying spare parts or support materials would be impractical and the mission timeline would be in the order of years in the case of a mission to Mars. In addition, future missions are expected to include a period of dormancy in which the WRS would be unused for an extended duration. The concepts developed in this review arose from a workshop including NASA personnel and representatives with biofilm expertise from a wide range of industrial and academic backgrounds. Here, we address current strategies that are employed on Earth for biofilm control, including antifouling coatings and biocides and mechanisms for mitigating biofilm growth and damage. These ideas are presented in the context of their applicability to spaceflight and identify proposed new topics of biofilm control that need to be addressed in order to facilitate future extended, crewed, spaceflight missions.

An Overview of Current Knowledge on the Properties, Synthesis and Applications of Quaternary Chitosan Derivatives

Chitosan, a chitin-derivative polysaccharide, known for its non-toxicity, biocompatibility and biodegradability, presents limited applications due to its low solubility in neutral or basic pH medium. Quaternization stands out as an alternative to modify this natural polymer, aiming to improve its solubility over a wide pH range and, consequently, expand its range of applications. Quaternization occurs by introducing a quaternary ammonium moiety onto or outside the chitosan backbone, via chemical reactions with primary amino and hydroxyl groups, under vast experimental conditions. The oldest and most common forms of quaternized chitosan involve N,N,N-trimethyl chitosan (TMC) and N-[(2-hydroxy-3-trimethyl ammonium) propyl] chitosan (HTCC) and, more recently, quaternized chitosan by insertion of pyridinium or phosphonium salts. By modifying chitosan through the insertion of a quaternary moiety, permanent cationic charges on the polysaccharide backbone are achieved and properties such as water solubility, antimicrobial activity, mucoadhesiveness and permeability are significantly improved, enabling the application mainly in the biomedical and pharmaceutical areas. In this review, the main quaternized chitosan compounds are addressed in terms of their structure, properties, synthesis routes and applications. In addition, other less explored compounds are also presented, involving the main findings and future prospects regarding the field of quaternized chitosans.

Synthesis of cationic acrylate copolyvidone-iodine nanoparticles with double active centers and their antibacterial application

Antibacterial materials are rapidly emerging as a primary component in the mitigation of bacterial pathogens, and functional polymers play a vital role in the preparation of antibacterial coatings. In this study, a novel antibacterial polymer with double active centers was synthesized. Firstly, using one-pot soap-free emulsion polymerization technology, the cationic acrylate copolymeric polyvidone (CACPV) was synthesized by copolymerization of four monomers with different functions, which were methyl methacrylate (MMA), N-vinyl-2-pyrrolidone (NVP), γ-methacryloxypropyltrimethoxysilane (MAPTS) and [3-(methacryloylamino)propyl]trimethylammonium chloride (MAPTAC). Secondly, using iodine complexation, the cationic acrylate copolyvidone-iodine (CACPVI) nanoparticles were prepared. After being characterized by scanning electron microscopy (SEM), dynamic light scattering (DLS), X-ray photoelectron spectroscopy (XPS) and contact angle test, the antibacterial activity of CACPVI was evaluated against the typical human pathogens Escherichia coli (E. coli, Gram-negative) and Staphylococcus aureus (S. aureus, Gram-positive). Additionally, CACPVI was used to improve the antibacterial activities of some materials, such as ink, dye and coatings. It was found that CACPVI presented an excellent antibacterial synergy. When the antibacterial activities were more than 99% at a concentration of 40.00 μg mL-1, CACPVI exhibited long-term antibacterial performance as expected. The antibacterial mechanism of this synergy was also investigated. In summary, a novel antibacterial polymer material with double active centers was successfully synthesized and was widely applied in coating, dye and ink materials for minimizing bacterial infection.

Potential of discarded sardine scales (Sardina pilchardus) as chitosan sources

The random discharge of marine fish waste into the coast generates environmental pollution. However, a better valorization of these by-products leads to the extraction of sustainable biomolecules. Chitosan is a natural biopolymer that can be produced from various marine by-products, in particular the crustacean shells, crabs, and fish scales. The aim of this current study is the extraction of chitin and characterization of chitosan obtained after a deacetylation reaction from sardine scales (S. pilchardus) as a new marine source. The β form of chitin extracted undergoes deacetylation in 40% NaOH at 121°C for 20 min. The chemical structure of obtained chitosan was characterized based on Fourier transforms infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), Scanning electron microscope (SEM), and Energy-dispersive X-ray spectroscopy (EDS). The physicochemical properties of obtained chitosan such as the ash, moisture, nitrogen, solubility, molecular weight, fat, and water-binding capacity were also determined. According to the results of FTIR and XRD analysis, the degree of deacetylation (DDA), and the crystalline index (CrI) value of obtained chitosan is respectively about 87% and 95%. The SEM and EDS analysis revealed respectively fibrillar and pleated morphology with the presence of three major elements characterizing the chitosan, which are C, O, and N. The physicochemical analysis showed that the rate of ash, moisture, and nitrogen in obtained chitosan were respectively about 0.10, 0.34, and 7%. The solubility, molecular weight, fat, and water-binding capacity of produced chitosan were found to be 93%, 5.86 kDa, 310, and 510% respectively. Sardina pilchardus scales could be considered a promising and alternative source of chitin and chitosan, which will be applicable in a large number of fields. Implications: Direct rejection of marine biowaste as fish scales in nature, port, or fish processing plants, is a dramatic problem that is growing day after day. These uncontrollable discharges cause marine pollution and promote bacterial growth, which leads to a degradation of the soil and air quality. Taking into account the objectives of sustainable development, better development of these by-products would make it possible to produce valuable biomaterials that will be applied in various fields and which have benefits for the environment and humans. The central objective of this research is accentuated on the enhancement of Sardina pilchardus scales; by the conversion of chitin into chitosan and the determination of its physicochemical characterization. The obtained chitosan from Sardina pilchardus scales could be applied in the agricultural and food industry.

Antibacterial Activity of Chitosan Nanoparticles: A Review

In recent years, nanotechnology has attracted attention in many fields because it has several up-and-coming novel uses. Many researchers have suggested that chitosan nanoparticles (CS-NPs) and their derivatives are one of the best nanomaterials for delivering antibacterial activity. CS-NPs have a broad spectrum of antibacterial activity, but they manifest different inhibitory efficacy against gram-negative (G−) and gram-positive (G+) bacterial species. The mechanism of antibacterial action is an intricate process that varies between G− and G+ bacteria as a result of the differences in cell wall and cell membrane chemistry. In previous studies, greater antibacterial activity was more evident against G− bacteria than G+ bacteria, whereas in some studies G+ bacteria were more sensitive. Researchers predicted that the varied responses of bacteria are caused by the mixed hydrophilicity and negative charge distribution on the bacterial surface. Moreover, its activity depends on a number of variables including bacterial target (i.e., G− or G+ bacteria) and bacterial growth, as well as its concentration, pH, zeta-potential, molecular weight, and degree of acetylation. Therefore, this review examines current research on the mechanisms and factors affecting antibacterial activity, and application of CS-NPs specifically against animal and plant pathogenic bacteria.

Chitosan: Structural modification, biological activity and application

Many by-products that are harmful to the environment and human health are generated during food processing. However, these wastes are often potential resources with high-added value. For example, crustacean waste contains large amounts of chitin. Chitin is one of the most abundant polysaccharides in natural macromolecules, and is a typical component of crustaceans, mollusks, insect exoskeleton and fungal cell walls. Chitosan is prepared by deacetylation of chitin and a copolymer of D-glucosamine and N-acetyl-D-glucosamine through β-(1 → 4)-glycosidic bonds. Chitosan has better solubility, biocompatibility and degradability compared with chitin. This review introduces the preparation, physicochemical properties, chemical and physical modification methods of chitosan, which could help us understand its biological activities and applications. According to the latest reports, the antibacterial activity, antioxidant, immune and antitumor activities of chitosan and its derivatives are summarized. Simultaneously, the various applications of chitosan and its derivatives are reviewed, including food, chemical, textile, medical and health, and functional materials. Finally, some insights into its future potential are provided, including novel modification methods, directional modification according to structure-activity relationship, activity and application development direction, etc.

Antibacterial activities of microwave-assisted synthesized polypyrrole/chitosan and poly (pyrrole-N-(1-naphthyl) ethylenediamine) stimulated by C-dots

Polypyrrole grafted with chitosan (PPy-g-CS) and poly (pyrrole-N-(1-naphthyl) ethylenediamine, a copolymer, (COP) have been synthesized by a one-step microwave procedure with carbon dots(C-Dots) as initiators. The electrostatic interaction between the positively charged polymers and negatively charged microbial cell membranes is widely anticipated to be responsible for cellular lysis. However, Escherichia coli exposed to PPy-g-CS (zeta potential = +46.9 mV) was completely perished after 3 h while COP (zeta potential = +64.1 mV) exhibited no antimicrobial effect. The two polymers were capable of eradicating Staphylococcus aureus, implying the charged effect is the main mechanism of cell death. The two polymers could also chelate calcium and other nutrients as well as form an external barrier to suppress the penetration of essential nutrients to support microbial survival and proliferation. In particular, pyrrole grafted chitosan was reasoned to stack onto the bacterial surface to impede the mass transfer and suppress the bacterial metabolic activity. The binding of chitosan to teichoic acids, essential acids of Gram-positive bacteria, would provoke a sequence of events and lead to bacterial death.

Anti-staphylococcal activity of quaternized mannan from the yeast Candida albicans

Global increase of antibiotic-resistant pathogens as well as elevated content of drug residues in the foodstuffs and the environment urgently calls for new biocompatible antimicrobial biomaterials. Yeast mannans represent readily available source of biodegradable materials for tailor-made derivatives that could be effective in biomedical applications. Here, antimicrobial properties of quaternized mannans (DS_Q 0.12, 0.24, 0.30, 0.62) from Candida albicans against clinical multi-resistant strains of Staphylococcus aureus are confronted with possible cytotoxicity against human cells. As expected, both effects increase with increasing degree of quaternization. However, it is possible to define the "window", at quaternized mannan with DS_Q 0.30 with good anti-microbial effectiveness and low cytotoxicity. This derivative exhibit minimum inhibitory (MIC) and minimum bactericidal (MBC) concentration from 62.5 to 250 μg/mL and demonstrate good biofilm inhibition effect. Also acceptable values were obtained in hemagglutination and hemolytic activity assays and also in cytotoxicity tests on human fibroblasts.

Antiviral Activity of Curcumin Loaded Milk Proteins Nanoparticles on Potato Virus Y

BACKGROUND AND OBJECTIVE

Potato is one of the world's leading vegetable crops. Potato viral diseases cause adversely effects on the agricultural sector. Recently there is a growing interest to control plant viruses using spices and herbs (including curcumin). Poor solubility of curcumin in water limited its applications. Therefore, the main objective of the present study was to evaluate the effect of antiviral activity of curcumin-milk proteins nanoparticles against potato virus Y (PVY).

MATERIALS AND METHODS

Curcumin-milk proteins nanoparticles were prepared via ionic gelation method. The antiviral activity of the resultant nanoparticles against PVY was evaluated at different concentrations (500, 1000 and 1500 mg/100 mL). Chlorophyll content as well as the activity of peroxidase (POX) and polyphenol oxidase (PPO) was examined.

RESULTS

Curcumin-milk proteins nanoparticles showed inhibitory effect on PVY in a concentration dependent manner.

CONCLUSION

Curcumin-milk proteins nanoparticles displayed a successful tool to control the PVY under green house conditions.

Universal Antibacterial Surfaces Fabricated from Quaternary Ammonium Salt-Based PNIPAM Microgels

Because of the excellent film-forming ability of poly(N-isopropylacrylamide) (PNIPAM) microgel and high-efficient bactericidal property of quaternary ammonium salt (QAS), QAS-based PNIPAM (QAS-PNIPAM) microgels are synthesized and employed to modify the surface of a range of commonly used materials including metal, plastic, and elastomer. Bacterial culture is carried out on such QAS-PNIPAM microgel-modified surfaces to examine the viability of the attached bacteria. It is found that the bactericidal efficiency is nearly 100% on the modified surfaces of all the studied materials. We attribute the high-efficient bactericidal performance of QAS-PNIPAM microgel film to the QAS component rather than the topography of the microgel film itself. In addition, the microgel film is robust and shows great integrity even after culture of the bacteria and repeated rinses, and the cell experiment demonstrates that this microgel film is cyto-compatible. Therefore, such a simple, versatile method of preparing antibacterial films paves the way for future bactericidal applications.

Aerosol-Assisted Synthesis of Tailor-Made Hollow Mesoporous Silica Microspheres for Controlled Release of Antibacterial and Anticancer Agents

Hollow mesoporous silica microsphere (HMSM) particles are one of the most promising vehicles for efficient drug delivery owing to their large hollow interior cavity for drug loading and the permeable mesoporous shell for controlled drug release. Here, we report an easily controllable aerosol-based approach to produce HMSM particles by continuous spray-drying of colloidal silica nanoparticles and Eudragit/Triton X100 composite (EUT) nanospheres as templates, followed by template removal. Importantly, the internal structure of the hollow cavity and the external morphology and the porosity of the mesoporous shell can be tuned to a certain extent by adjusting the experimental conditions (i.e., silica to EUT mass ratio and particle size of silica nanoparticles) to optimize the drug loading capacity and the controlled-release properties. Then, the application of aerosol-synthesized HMSM particles in controlled drug delivery was investigated by loading amoxicillin as an antibiotic compound with high entrapment efficiency (up to 46%). Furthermore, to improve the biocompatibility of the amoxicillin-loaded HMSM particles, their surfaces were functionalized with poly(allylamine hydrochloride) and alginate as biocompatible polymers via the layer-by-layer assembly. The resulting particles were evaluated toward Escherichia coli (Gram-negative) bacteria and indicated the bacterial inhibition up to 90% in less than 2 h. Finally, we explored the versatility of HMSMs as drug carriers for pancreatic cancer treatment. Because the pH value of the extracellular medium in pancreatic tumors is lower than that of the healthy tissue, chitosan as a pH-sensitive gatekeeper was grafted to the HMSM surface and then loaded with a pro-apoptotic NCL antagonist agent (N6L) as an anticancer drug. The obtained particles exhibited pH-responsive drug releases and excellent anticancer activities with inhibition of cancer cell growth up to 60%.

Enhanced antibacterial activity of calcium silicate-based hybrid cements for bone repair

Calcium silicate cement has attracted much attention for bone defect repair and regeneration due to its osteogenic properties. Biomaterial-associated infections and washout have become a common clinical problem. In order to enhance the antibacterial and washout performance of calcium silicate cement to meet clinical needs, different types of chitosan, including chitosan polysaccharide (CTS), quaternary ammonium chitosan (QTS), and chitosan oligosaccharide (COS), as a liquid phase were added to the calcium silicate powder. The physicochemical properties, in vitro bioactivity, antibacterial efficacy, and osteogenic effects (MG63 cells) of the cement were evaluated. Antibacterial activity was conducted with Gram-negative Escherichia coli (E. coli) and a Gram-positive Staphylococcus aureus (S. aureus) bacteria. The amount of intracellular reactive oxygen species (ROS) produced in the bacteria cultured with the chitosan solution was also detected. The experimental results showed that the chitosan additive did not affect the crystalline phase of calcium silicate cement, but increased the setting time and strength of the cement in a concentration-dependent manner. Within the scope of this study, CTS and QTS solutions with a concentration of not <1 wt% improved the washout resistance of the control cement, while the COS solutions failed to strengthen the cement. When soaked in simulated body fluid (SBF) for 1 day, all cement samples formed apatite spherules. As the soaking time increased, the diametral tensile strength of all cements decreased and the porosity increased. The assays of MG63 cell function showed lower osteogenic activity of osteoblastic cells grown on the surfaces of the chitosan-incorporated cements in comparison with the control cement without chitosan. At the same 1% concentration, compared with QTS and COS cement, CTS cement had lower cell attachment, proliferation, differentiation, and mineralization. Conversely, the CTS cement resulted in the highest bacteriostasis ratio among the three hybrid cements against two bacteria. The ROS production followed the order of CTS > QTS > COS at the same 1% concentration. In conclusion, calcium silicate cement with 1% QTS may be a viable candidate for bone defect repair in view of anti-washout performance, setting time, antibacterial activity, and osteogenic activity shown in this study.

Review of Chitosan-Based Polymers as Proton Exchange Membranes and Roles of Chitosan-Supported Ionic Liquids

Perfluorosulphonic acid-based membranes such as Nafion are widely used in fuel cell applications. However, these membranes have several drawbacks, including high expense, non-eco-friendliness, and low proton conductivity under anhydrous conditions. Biopolymer-based membranes, such as chitosan (CS), cellulose, and carrageenan, are popular. They have been introduced and are being studied as alternative materials for enhancing fuel cell performance, because they are environmentally friendly and economical. Modifications that will enhance the proton conductivity of biopolymer-based membranes have been performed. Ionic liquids, which are good electrolytes, are studied for their potential to improve the ionic conductivity and thermal stability of fuel cell applications. This review summarizes the development and evolution of CS biopolymer-based membranes and ionic liquids in fuel cell applications over the past decade. It also focuses on the improved performances of fuel cell applications using biopolymer-based membranes and ionic liquids as promising clean energy.

Synthesis and characterization of quaternized agar in KOH/urea aqueous solution

Quaternized agar (QA) is synthesized in KOH/urea aqueous solution and shows low melting and gelling temperatures and antibacterial properties.

Quaternized Chitosan Nanoparticles in Vaccine Applications

Different natural and synthetic biodegradable polymers have been used in vaccine formulations as adjuvant and delivery system but have faced various limitations. Chitosan is a new delivery system with the potential to improve development of nano vaccines and drugs. However, chitosan is only soluble in acidic solutions of low concentration inorganic acids such as dilute acetic acid and dilute hydrochloric acid and in pure organic solvents, which greatly limits its application. Chemical modification of chitosan is an important way to improve its weak solubility. Quaternized chitosan not only retains the excellent properties of chitosan, but also improves its water solubility for a wider application. Recently, quaternized chitosan nanoparticles have been widely used in biomedical field. This review focuses on some quaternized chitosan nanoparticles, and points out the advantages and research direction of quaternized chitosan nanoparticles. As shown by the applications of quaternized chitosan nanoparticles as adjuvant and delivery carrier in vaccines, quaternized chitosan nanoparticles have promising potential in application for the development of nano vaccines in the future.