Antibacterial, Antibiofilm, and Antiadhesive Properties of Different Quaternized Chitosan Derivatives

Valorization of fishery industry waste: Chitosan extraction and its application in the industry

Waste from the fishing industry is disposed of in soils and oceans, causing environmental damage. However, it is also a source of valuable compounds such as chitin. Although chitin is the second most abundant polymer in nature, its use in industry is limited due to the lack of standardized and scalable extraction methods and its poor solubility. The deacetylation process increases its potential applications by enabling the recovery of chitosan, which is soluble in dilute acidic solutions. Chitosan is a polymer of great importance due to its biocompatible and bioactive properties, which include antimicrobial and antioxidant capabilities. Chitin extraction and its deacetylation to obtain chitosan are typically performed using chemical processes that involve large amounts of strongly acidic and alkaline solutions. To reduce the environmental impact of this process, extraction methods based on biotechnological tools, such as fermentation and chitin deacetylase, as well as emerging technologies, have been proposed. These extraction methods have demonstrated the potential to reduce or even avoid using strong solvents and shorten extraction time, thereby reducing costs. Nevertheless, it is important to address existing gaps in this area, such as the requirements for large-scale implementation and the determination of the stoichiometric ratios for each process. This review highlights the use of biotechnological tools and emerging technologies for chitin extraction and chitosan production. These approaches truly minimize environmental impact, reduce the use of strong solvents, and shorten extraction time. They are a reliable alternative to fishery waste valorization, lowering costs; however, addressing the critical gaps for their large-scale implementation remains challenging.

Comparison of the Antimicrobial Efficacy of Conventional Versus Chitosan Re-inforced Heat-Polymerized Polymethylmethacrylate Dental Material: An In Vitro Study

INTRODUCTION

 Polymethylmethacrylate (PMMA) is widely used in the fabrication of dentures due to its aesthetic appeal and mechanical strength. However, PMMA's susceptibility to microbial colonization often leads to oral infections such as denture stomatitis. Enhancing the antimicrobial properties of denture materials is crucial for improving patient outcomes. Chitosan, a natural biopolymer, possesses inherent antimicrobial properties and could potentially enhance the microbial resistance of PMMA. This study has investigated the potential of chitosan-reinforced heat-polymerized PMMA denture material to reduce microbial colonization.

AIM

 The aim of the study was to evaluate and assess the anti-bacterial and antifungal properties of chitosan-reinforced heat-polymerized PMMA with conventional heat-polymerized PMMA Materials and methods: Chitosan-reinforced PMMA samples were fabricated with varying chitosan concentrations (0% control, 5%, 10%, and 15% by weight). The fabrication involved mixing chitosan powder with PMMA powder, adding monomer liquid, followed by mixing, packing, and curing using the conventional heat polymerization technique. The antimicrobial efficacy was assessed in vitro using two common oral pathogens: Streptococcus mutans and Candida albicans. Blood agar plates were used for S. mutans and Sabouraud agar plates were used for C. albicans. Each sample was placed on the respective agar plates inoculated with a standardized microbial suspension and incubated at 37°C for 24 hours. The number of colony-forming units (CFUs) was counted to quantify microbial growth. Statistical analyses, including linear regression analysis, one-way ANOVA test, and Pearson correlation were performed to evaluate the relationship between chitosan concentration and antimicrobial efficacy. The p-value was calculated to determine the statistical significance of the results.

RESULTS

 The chitosan-reinforced PMMA samples showed significantly greater antimicrobial efficacy compared to the conventional PMMA samples. The CFU counts for both S. mutans and C. albicans decreased with increasing chitosan concentration. Linear regression analysis indicated a strong negative correlation between chitosan concentration and CFU counts, with Pearson correlation coefficients of -0.97 for S. mutans and -0.98 for C. albicans. ANOVA analysis revealed a statistically significant difference in antimicrobial efficacy across different chitosan concentrations (p < 0.001).

CONCLUSION

 Incorporating chitosan into heat-polymerized PMMA significantly enhances its antimicrobial properties against S. mutans and C. albicans. The antimicrobial efficacy improves with higher concentrations of chitosan, with the 15% chitosan-reinforced samples showing the most substantial reduction in microbial growth. These results suggest that chitosan-reinforced PMMA dentures could be a superior alternative to conventional PMMA dentures, potentially reducing denture-related infections and improving oral health outcomes for denture wearers.

Synthesis and characterization of modified chitosan as a promising material for enterosorption of heavy metal ions

Currently, an important ecological problem is environmental pollution and its negative impact on living organisms, the consequences of which are deterioration in general health and the manifestation of various diseases, poisoning, endo- and exotoxicosis. Enterosorption method was proposed as a promising method for removing toxic substances from the living organisms using enterosorbents which can absorb various toxic substances of endogenous and exogenous nature in the lumen of the gastrointestinal tract. It has been proposed to use polymer-containing enterosorbents for eliminating of heavy metals from the organism. The purpose of this research was to synthesize a quaternized derivative of chitosan, specifically N-(2-hydroxybenzyl)-N-ethyl-N-methyl chitosan chloride (Q-CHS). The synthesis of Q-CHS involved the formation of a Schiff base, followed by the quaternization of the amino group of chitosan (CHS). The structures of both pure CHS and quaternized CHS were studied using various physico-chemical methods, including FTIR, NMR, XRD, SEM, DSC and TGA analyses in order to determine the structure and confirm the formation of the final product.

Chitosan-based biomaterial delivery strategies for hepatocellular carcinoma

Background

Hepatocellular carcinoma accounts for 80% of primary liver cancers, is the most common primary liver malignancy. Hepatocellular carcinoma is the third leading cause of tumor-related deaths worldwide, with a 5-year survival rate of approximately 18%. Chemotherapy, although commonly used for hepatocellular carcinoma treatment, is limited by systemic toxicity and drug resistance. Improving targeted delivery of chemotherapy drugs to tumor cells without causing systemic side effects is a current research focus. Chitosan, a biopolymer derived from chitin, possesses good biocompatibility and biodegradability, making it suitable for drug delivery. Enhanced chitosan formulations retain the anti-tumor properties while improving stability. Chitosan-based biomaterials promote hepatocellular carcinoma apoptosis, exhibit antioxidant and anti-inflammatory effects, inhibit tumor angiogenesis, and improve extracellular matrix remodeling for enhanced anti-tumor therapy.

Methods

We summarized published experimental papers by querying them.

Results and Conclusions

This review discusses the physicochemical properties of chitosan, its application in hepatocellular carcinoma treatment, and the challenges faced by chitosan-based biomaterials.

Synthesis of N-isonicotinic sulfonate chitosan and its antibiofilm activity against E. coli and S.aureus

N-(sodium 2-hydroxypropylsulfonate) chitosan (HSCS), N-sulfonate chitosan (SCS) and N-isonicotinic sulfonate chitosan (ISCS) were prepared. The structures of the prepared chitosan derivatives were characterized by nuclear magnetic resonance (1H NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy and elemental analysis (EA). Antibacterial and antibiofilm activities of these chitosan derivatives were evaluated in vitro. The minimum inhibitory concentration (MIC) of HSCS and SCS against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were 0.625 mg/mL and 0.156 mg/mL, respectively. ISCS exhibited MIC values of 0.313 mg/mL and 0.078 mg/mL against E. coli and S. aureus, respectively. ISCS demonstrated superior antibacterial and antibiofilm properties compared to SCS and HSCS. These findings suggest that the incorporation of a pyridine structure into sulfonate chitosan enhances its antibacterial and antibiofilm activities, and the prepared ISCS has a promising application prospect for controlling the reproduction of microorganisms in the field of food packaging.

Exploring the antimicrobial potential of chitosan nanoparticles: synthesis, characterization and impact on Pseudomonas aeruginosa virulence factors

The escalating antibiotic resistance observed in bacteria poses a significant threat to society, with the global prevalence of resistant strains of Pseudomonas aeruginosa on the rise. Addressing this challenge necessitates exploring strategies that would complement existing antimicrobial agents, e.g. by substances mitigating bacterial virulence without eliciting selective pressure for resistance emergence. In this respect, free-form chitosan has demonstrated promising efficacy, prompting our investigation into reinforcing its effects through nanoparticle formulations. Our study focuses on the preparation of chitosan nanoparticles under suitable conditions while emphasizing the challenges associated with stability that can affect biological activity. These challenges are mitigated by introducing quaternized chitosan, which ensures colloidal stability in the culture media. Our approach led to the production of trimethylchitosan nanoparticles with a median size of 103 nm, circularity of 0.967, and a charge of 14.9 ± 3.1 mV, stable within a one-month period in a water stock solution, showing promising attributes for further valorization. Furthermore, the study delves into the antimicrobial activity of trimethylchitosan nanoparticles on Pseudomonas aeruginosa and confirms the benefits of both nanoformulation and modification of chitosan, as our prepared nanoparticles inhibit 50% of the bacterial population at concentration ≥160 mg L-1 within tested strains. Additionally, we identified a concentration of 5 mg L-1 that no longer impedes bacterial growth, allowing reliable verification of the effect of the prepared nanoparticles on Pseudomonas aeruginosa virulence factors, including motility, protease activity, hemolytic activity, rhamnolipids, pyocyanin, and biofilm production. Although trimethylchitosan nanoparticles exhibit promise as an effective antibiofilm agent (reducing biofilm development by 50% at concentrations ranging from 80 to 160 mg L-1) their impact on virulence manifestation is likely not directly associated with quorum sensing. Instead, it can probably be attributed to non-specific interactions with the bacterial surface. This exploration provides valuable insights into the potential of quaternized chitosan nanoparticles in addressing Pseudomonas aeruginosa infections and underscores the multifaceted nature of their antimicrobial effects.

Biopolymer Drug Delivery Systems for Oromucosal Application: Recent Trends in Pharmaceutical R&D

Oromucosal drug delivery, both local and transmucosal (buccal), is an effective alternative to traditional oral and parenteral dosage forms because it increases drug bioavailability and reduces systemic drug toxicity. The oral mucosa has a good blood supply, which ensures that drug molecules enter the systemic circulation directly, avoiding drug metabolism during the first passage through the liver. At the same time, the mucosa has a number of barriers, including mucus, epithelium, enzymes, and immunocompetent cells, that are designed to prevent the entry of foreign substances into the body, which also complicates the absorption of drugs. The development of oromucosal drug delivery systems based on mucoadhesive biopolymers and their derivatives (especially thiolated and catecholated derivatives) is a promising strategy for the pharmaceutical development of safe and effective dosage forms. Solid, semi-solid and liquid pharmaceutical formulations based on biopolymers have several advantageous properties, such as prolonged residence time on the mucosa due to high mucoadhesion, unidirectional and modified drug release capabilities, and enhanced drug permeability. Biopolymers are non-toxic, biocompatible, biodegradable and may possess intrinsic bioactivity. A rational approach to the design of oromucosal delivery systems requires an understanding of both the anatomy/physiology of the oral mucosa and the physicochemical and biopharmaceutical properties of the drug molecule/biopolymer, as presented in this review. This review summarizes the advances in the pharmaceutical development of mucoadhesive oromucosal dosage forms (e.g., patches, buccal tablets, and hydrogel systems), including nanotechnology-based biopolymer nanoparticle delivery systems (e.g., solid lipid particles, liposomes, biopolymer polyelectrolyte particles, hybrid nanoparticles, etc.).

Synthesis of new quaternized chitosan Schiff bases and their N-alkyl derivatives as antimicrobial and anti-biofilm retardants in membrane technology

New quaternized salicylidene chitosan Schiff bases (QSCSBs) and their N-octyl derivatives (OQCs) have been synthesized and characterized, aiming to develop innovative antimicrobial and anti-biofilm agents. This research holds immense potential, as these compounds could be utilized as anti-biofouling additives in membrane technology in the future. The synthesis involved the modification of low molecular-weight-chitosan (LMC) through simultaneous Schiff base formation and quaternization processes to create QSCSBs. Subsequently, QSCSBs were catalytically reduced to form quaternized N-benzyl chitosan (QBCs) intermediates, which then underwent nucleophilic substitution reactions affording N-octyl quaternized chitosans (OQCs). Characterization techniques such as elemental, spectral, and microscopic analyses were used to confirm the successful synthesis of these materials. As membrane technology relies on surface charge, QSCSBs and OQCs with large zeta potentials could be used as positively charged additives. Moreover, SEM image revealed the regular distribution of pores and voids across the additives' surfaces raises intriguing questions about their implications for membrane performance. Meanwhile, the superior antibacterial and antibiofilm potential of these materials, particularly QSCSB2 and OQC2, indicate that the utilization of these compounds as anti-biofouling additives in membrane technology could significantly improve the performance and longevity of membranes used in various applications such as water treatment and desalination.

Combining with domiphen bromide restores colistin efficacy against colistin-resistant Gram-negative bacteria in vitro and in vivo

Today, colistin is considered a last-resort antibiotic for treating multidrug-resistant (MDR) Gram-negative bacteria (GNB). However, the increased and improper use of colistin has led to the emergence of colistin-resistant (Col-R) GNB. Thus, it is urgent to develop new drugs and therapies in response to the ongoing emergence of colistin resistance. In this study, we investigated the antibacterial and antibiofilm activities of the quaternary ammonium compound domiphen bromide (DB) in combination with colistin against clinical Col-R GNB both in vitro and in vivo. Checkerboard assay and time-kill analysis demonstrated significant synergistic antibacterial effects of the colistin/DB combination. The synergistic antibiofilm activity was confirmed through crystal violet staining and scanning electron microscopy (SEM). Furthermore, the colistin/DB combination exhibited increased survival rates in infected larvae and reduced bacterial loads in a mouse thigh infection model. The cytotoxicity measurement and hemolysis test showed that the combination did not adversely affect cell viability at synergistic concentrations. The alkaline phosphatase (ALP) leak test and propidium iodide (PI) staining analysis further revealed that the colistin/DB combination enhanced the therapeutic effect of colistin by altering bacterial membrane permeability. The ROS assays revealed that the combination induced the accumulation of bacterial ROS, leading to bacterial death. In conclusion, our study is the first to identify DB as a colistin potentiator, effectively restoring the sensitivity of bacteria to colistin. It provides a promising alternative approach for combating Col-R GNB infections.

Shifting from Ammonium to Phosphonium Salts: A Promising Strategy to Develop Next-Generation Weapons against Biofilms

Since they are difficult and sometimes impossible to treat, infections sustained by multidrug-resistant (MDR) pathogens, emerging especially in nosocomial environments, are an increasing global public health concern, translating into high mortality and healthcare costs. In addition to having acquired intrinsic abilities to resist available antibiotic treatments, MDR bacteria can transmit genetic material encoding for resistance to non-mutated bacteria, thus strongly decreasing the number of available effective antibiotics. Moreover, several pathogens develop resistance by forming biofilms (BFs), a safe and antibiotic-resistant home for microorganisms. BFs are made of well-organized bacterial communities, encased and protected in a self-produced extracellular polymeric matrix, which impedes antibiotics' ability to reach bacteria, thus causing them to lose efficacy. By adhering to living or abiotic surfaces in healthcare settings, especially in intensive care units where immunocompromised older patients with several comorbidities are hospitalized BFs cause the onset of difficult-to-eradicate infections. In this context, recent studies have demonstrated that quaternary ammonium compounds (QACs), acting as membrane disruptors and initially with a low tendency to develop resistance, have demonstrated anti-BF potentialities. However, a paucity of innovation in this space has driven the emergence of QAC resistance. More recently, quaternary phosphonium salts (QPSs), including tri-phenyl alkyl phosphonium derivatives, achievable by easy one-step reactions and well known as intermediates of the Wittig reaction, have shown promising anti-BF effects in vitro. Here, after an overview of pathogen resistance, BFs, and QACs, we have reviewed the QPSs developed and assayed to this end, so far. Finally, the synthetic strategies used to prepare QPSs have also been provided and discussed to spur the synthesis of novel compounds of this class. We think that the extension of the knowledge about these materials by this review could be a successful approach to finding effective weapons for treating chronic infections and device-associated diseases sustained by BF-producing MDR bacteria.

Physiological Concentrations of Calcium Interact with Alginate and Extracellular DNA in the Matrices of Pseudomonas aeruginosa Biofilms to Impede Phagocytosis by Neutrophils

Biofilms are communities of interacting microbes embedded in a matrix of polymer, protein, and other materials. Biofilms develop distinct mechanical characteristics that depend on their predominant matrix components. These matrix components may be produced by microbes themselves or, for infections in vivo, incorporated from the host environment. Pseudomonas aeruginosa (P. aeruginosa) is a human pathogen that forms robust biofilms that extensively tolerate antibiotics and effectively evade clearance by the immune system. Two of the important bacterial-produced polymers in the matrices of P. aeruginosa biofilms are alginate and extracellular DNA (eDNA), both of which are anionic and therefore have the potential to interact electrostatically with cations. Many physiological sites of infection contain significant concentrations of the calcium ion (Ca2+). In this study, we investigate the structural and mechanical impacts of Ca2+ supplementation in alginate-dominated biofilms grown in vitro, and we evaluate the impact of targeted enzyme treatments on clearance by immune cells. We use multiple-particle tracking microrheology to evaluate the changes in biofilm viscoelasticity caused by treatment with alginate lyase or DNase I. For biofilms grown without Ca2+, we correlate a decrease in relative elasticity with increased phagocytic success. However, we find that growth with Ca2+ supplementation disrupts this correlation except in the case where both enzymes are applied. This suggests that the calcium cation may be impacting the microstructure of the biofilm in nontrivial ways. Indeed, confocal laser scanning fluorescence microscopy and scanning electron microscopy reveal unique Ca2+-dependent eDNA and alginate microstructures. Our results suggest that the presence of Ca2+ drives the formation of structurally and compositionally discrete microdomains within the biofilm through electrostatic interactions with the anionic matrix components eDNA and alginate. Further, we observe that these structures serve a protective function as the dissolution of both components is required to render biofilm bacteria vulnerable to phagocytosis by neutrophils.

Physiological concentrations of calcium interact with alginate and extracellular DNA in the matrices of Pseudomonas aeruginosa biofilms to impede phagocytosis by neutrophils

Biofilms are communities of interacting microbes embedded in a matrix of polymer, protein, and other materials. Biofilms develop distinct mechanical characteristics that depend on their predominant matrix components. These matrix components may be produced by microbes themselves or, for infections in vivo, incorporated from the host environment. Pseudomonas aeruginosa is a human pathogen that forms robust biofilms that extensively tolerate antibiotics and effectively evade clearance by the immune system. Two of the important bacterial-produced polymers in the matrices of P. aeruginosa biofilms are alginate and extracellular DNA (eDNA), both of which are anionic and therefore have the potential to interact electrostatically with cations. Many physiological sites of infection contain significant concentrations of the calcium ion (Ca2+). In this study we investigate the structural and mechanical impacts of Ca2+ supplementation in alginate-dominated biofilms grown in vitro and we evaluate the impact of targeted enzyme treatments on clearance by immune cells. We use multiple particle tracking microrheology to evaluate the changes in biofilm viscoelasticity caused by treatment with alginate lyase and/or DNAse I. For biofilms grown without Ca2+, we correlate a decrease in relative elasticity with increased phagocytic success. However, we find that growth with Ca2+ supplementation disrupts this correlation except in the case where both enzymes are applied. This suggests that the calcium cation may be impacting the microstructure of the biofilm in non-trivial ways. Indeed, confocal laser scanning fluorescence microscopy and scanning electron microscopy reveal unique Ca2+-dependent eDNA and alginate microstructures. Our results suggest that the presence of Ca2+ drives the formation of structurally and compositionally discrete microdomains within the biofilm through electrostatic interactions with the anionic matrix components eDNA and alginate. Further, we observe that these structures serve a protective function as the dissolution of both components is required to render biofilm bacteria vulnerable to phagocytosis by neutrophils.

Enhancing the Hydrophobicity and Antibacterial Properties of SiCN-Coated Surfaces with Quaternization to Address Peri-Implantitis

Peri-implantitis is a major cause of dental implant failure. This disease is an inflammation of the tissues surrounding the implant, and, while the cause is multi-factorial, bacteria is the main culprit in initiating an inflammatory reaction. Dental implants with silicon carbonitride (SiCN) coatings have several potential advantages over traditional titanium implants, but their antibacterial efficiency has not yet been evaluated. The purpose of this study was to determine the anti-bacterial potential of SiCN by modifying the surface of SiCN-coated implants to have a positive charge on the nitrogen atoms through the quaternization of the surface atoms. The changes in surface chemistry were confirmed using contact angle measurement and XPS analysis. The modified SiCN surfaces were inoculated with Streptococcus mutans (S. mutans) and compared with a silicon control. The cultured bacterial colonies for the experimental group were 80% less than the control silicon surface. Fluorescent microscopy with live bacteria staining demonstrated significantly reduced bacterial coverage after 3 and 7 days of incubation. Scanning electron microscopy (SEM) was used to visualize the coated surfaces after bacterial inoculation, and the mechanism for the antibacterial properties of the quaternized SiCN was confirmed by observing ruptured bacteria membrane along the surface.

Molar-mass-dependent antibacterial activity of cationic dextran derivatives against resistant nosocomial pathogens

The rise of various multidrug-resistant bacteria has created a need for new biocompatible and biodegradable antibacterial compounds. Cationic polysaccharides are promising candidates for this role. Therefore, cationic derivatives of commercial dextrans with molar masses of 11 kDa, 76 kDa, 411 kDa, and 1500-2500 kDa and various degrees of substitution (DS_Q 0.34-0.52) were prepared and their antimicrobial properties against four gram-negative nosocomial bacteria were tested. As expected, a higher DS_Q led to higher efficiency. The best antimicrobial properties were found for derivatives of 411 kDa, followed by 76 kDa and 1500-2000 kDa dextrans. This indicates that there is a certain optimum molar mass with the best antimicrobial properties. However, as molar mass increased, the biocompatibility of cationic dextran steadily decreased, with increased hemagglutination and toxicity being seen for human cells. The derivatives of 76 kDa dextran with higher DS_Q (0.40-0.52) were the best antimicrobial agents suitable for further clinical testing.

Cross-linked chitosan/lysozyme hydrogels with inherent antibacterial activity and tuneable drug release properties for cutaneous drug administration

Gels with high drug release sustainability and intrinsic antibacterial properties are of high practical potential for cutaneous drug administration, particularly for wound care and skin disease treatment. This study reports the generation and characterization of gels formed by 1,5-pentanedial-mediated crosslinking between chitosan and lysozyme for cutaneous drug delivery. Structures of the gels are characterized by using scanning electron microscopy, X-ray diffractometry and Fourier-transform infrared spectroscopy. An increase in the mass percentage of lysozyme leads to an increase in the swelling ratio and erosion susceptibility of the resulting gels. The drug delivery performance of the gels can be changed simply by manipulating the chitosan/lysozyme mass-to-mass ratio, with an increase in the mass percentage of lysozyme leading to a decline in the encapsulation efficiency and drug release sustainability of the gels. Not only do all gels tested in this study show negligible toxicity in NIH/3T3 fibroblasts, they also demonstrate intrinsic antibacterial effects against both Gram-negative and Gram-positive bacteria, with the magnitude of the effect being positively related to the mass percentage of lysozyme. All these warrant the gels to be further developed as intrinsically antibacterial carriers for cutaneous drug administration.

DEAE/Catechol-Chitosan Conjugates as Bioactive Polymers: Synthesis, Characterization, and Potential Applications

This work provides the first description of the synthesis and characterization of water-soluble chitosan (Cs) derivatives based on the conjugation of both diethylaminoethyl (DEAE) and catechol groups onto the Cs backbone (Cs-DC) in order to obtain a Cs derivative with antioxidant and antimicrobial properties. The degree of substitution [DS (%)] was 35.46% for DEAE and 2.53% for catechol, determined by spectroscopy. Changes in the molecular packing due to the incorporation of both pendant groups were described by X-ray diffraction and thermogravimetric analysis. For Cs, the crystallinity index was 59.46% and the maximum decomposition rate appeared at 309.3 °C, while for Cs-DC, the values corresponded to 16.98% and 236.4 °C, respectively. The incorporation of DEAE and catechol groups also increases the solubility of the polymer at pH > 7 without harming the antimicrobial activity displayed by the unmodified polymer. The catecholic derivatives increase the radical scavenging activity in terms of the half-maximum effective concentration (EC₅₀). An EC₅₀ of 1.20 μg/mL was found for neat hydrocaffeic acid (HCA) solution, while for chitosan-catechol (Cs-Ca) and Cs-DC solutions, concentrations equivalent to free HCA of 0.33 and 0.41 μg/mL were required, respectively. Cell culture results show that all Cs derivatives have low cytotoxicity, and Cs-DC showed the ability to reduce the activity of reactive oxygen species by 40% at concentrations as low as 4 μg/mL. Polymeric nanoparticles of Cs derivatives with a hydrodynamic diameter (D_h) of around 200 nm, unimodal size distributions, and a negative ζ-potential were obtained by ionotropic gelation and coated with hyaluronic acid in aqueous suspension, providing the multifunctional nanoparticles with higher stability and a narrower size distribution.

Functionalized aliphatic polyketones with germicide activity

The COVID-19 pandemic has further confirmed to the community that direct contact with contaminated surfaces and objects represents an important source of pathogen spreading among humans. Therefore, it is of paramount importance to design effective germicidal paints to ensure a rapid and potent disinfectant action of surfaces. In this work, we design novel germicide polymeric coatings by inserting quaternary ammonium and sugar groups on the macromolecular backbone, thus respectively endowing the polymer with germicide features and hydrophilicity to interact with the surfaces. An aliphatic polyketone was selected as a starting polymer matrix that was functionalized with primary amine derivatives via the Paal-Knorr reaction. The resulting polymers were deposited on cellulose filter papers and checkboard charts with excellent coating yield and substrate coverage as determined by scanning electron microscopy for cellulose. Remarkably, the substrates coated by the functional polymers bearing quaternary ammonium compounds showed excellent bactericide properties with antibacterial rate of 99% and logarithmic reduction of >3. Notably, the polymers with higher hydrophobicity showed better retention on the substrate after being treated with water at neutral pH.

Chitosan and its application in dental implantology

OBJECTIVE

The aim of this review was to evaluate the properties of chitosan for an application in dental implantology.

METHODS

Electronic Databases: PubMed, Google Scholar, Scopus, were used to recherche the articles published from 2010 to 2021. The keywords used were: chitosan, biocompatible, antibacterial, osseointegration, implant, bioactive. After a carefully selection according to the above keywords 46 articles met the condition to be studied RESULTS: Chitosan is a biopolymer, that can be easy produced. Its antibacterial, anti-inflammatory, anti-fugal, hemostatic, analgesic, mucoadhesive, osseointegrative properties and its excellent film-forming ability make chitosan a material with a future in dental implantology and in other areas of dental applications. Titan implants coated with chitosan showed better bioactive properties than uncoated implants. The treatment of the implant surface played an important role on the stability of implants. The activity of osteoblasts increased when the surface was laser-treated followed by coating with chitosan. The subsequent coating with apatite improved the bioactivity of chitosan.

CONCLUSION

Chitosan is a promising biocompatible and bioactive material in dental implantology. Its antibacterial properties can be enhanced by modification of its structure. Its bioactive properties can be improved when mixing with hydroxy apatite.

Synthesis, physicochemical characterization, antibacterial activity, and biocompatibility of quaternized hawthorn pectin

Quaternized polysaccharides are considered as potential antimicrobial materials due to their antimicrobial activity, biodegradability, biocompatibility, and water solubility. In this work, hawthorn pectin (HP) was obtained by ultrasound‑sodium citrate assisted extraction, quaternized hawthorn pectin (QHP) derivatives (namely: QHP-1, QHP-2, QHP-3, and QHP-4) with different degree of substitution were produced using (3-Chloro-2-hydroxypropyl) trimethylammonium chloride under alkaline conditions. The structure, properties, and morphology of HP and QHP were characterized by FTIR, XRD, ¹H NMR, high-performance gel permeation chromatography (HPGPC), thermal analysis, and SEM. The results of FTIR and ¹H NMR demonstrated that the quaternary ammonium modification was successful, and the degree of substitution (DS) of derivatives was calculated through elemental analysis. The determination of the minimum inhibitory concentrations and biofilm inhibition assay exhibited that QHP has a certain inhibitory effect on Escherichia coli and Staphylococcus aureus. Acceptable values of QHP were obtained in cytotoxicity assay on human keratinocytes.

Metabolomics-Driven Exploration of the Antibacterial Activity and Mechanism of 2-Methoxycinnamaldehyde

Methicillin-resistant Staphylococcus epidermidis (MRSE) is one of the most commonly found pathogens that may cause uncontrollable infections in immunocompromised and hospitalized patients. Compounds isolated from cinnamon such as cinnamaldehyde and cinnamic acid showed promising anti-oxidant, anti-tumor, and immunoregulatory effects; more importantly, these compounds also possess promising broad-spectrum antibacterial activity. In this study, the potential antibacterial activity of 2-methoxycinnamaldehyde (MCA), another compound in cinnamon, against MRSE was investigated. Combining the broth microdilution test, live/dead assay, and biofilm formation assay, we found MCA was able to inhibit the proliferation, as well as the biofilm formation of MRSE, indicating MCA could not only affect the growth of MRSE but also inhibit the pathogenic potential of this bacterium. Additionally, the results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) demonstrated that MCA caused morphological changes and the leakage of DNA, RNA, and cellular contents of MRSE. Due to the close relationship between cell wall synthesis, ROS formation, and cell metabolism, the ROS level and metabolic profile of MRSE were explored. Our study showed MCA significantly increased the ROS production in MRSE, and the following metabolomics analysis showed that the increased ROS production may partially be due to the increased metabolic flux through the TCA cycle. In addition, we noticed the metabolic flux through the pentose phosphate pathway (PPP) was upregulated accompanied by elevated ROS production. Therefore, the alterations in cell metabolism and increased ROS production could lead to the damage of the cell wall, which in turn decreased the proliferation of MRSE. In conclusion, MCA seemed to be a promising alternative antimicrobial agent to control MRSE infections.

Functionalized boron nanosheets with near-infrared-triggered photothermal and nitric oxide release activities for efficient antibacterial treatment and wound healing promotion

The spread of bacterial resistance is a rising serious threat to global public health, and has created an urgent need for the development of a new generation of antibacterial nano-agents to take the place of antibiotics. In this work, a multifunctional nanoplatform based on boron nanosheet (B NS)-coated quaternized chitosan (QCS) and the nitric oxide (NO) donor N,N'-di-sec-butyl-N,N'-dinitroso-1,4-phenylenediamine (BNN6) (B-QCS-BNN6) was prepared via a liquid-phase exfoliation and electrostatic adsorption method. The 2D B NSs could convert near-infrared (NIR) light into heat energy as well as assemble positively charged QCS and BNN6 to trap negatively charged bacteria, and the positive charge made it easily captured by bacteria, increasing the opportunities for NO diffusion to the bacterial surface. The B-QCS-BNN6 nanoplatform not only exhibited photothermal therapy (PTT) efficacy but could also control NO release precisely after stimulation with an 808 nm laser for the rapid and effective treatment of typical Gram-negative and Gram-positive bacteria. The enhanced PTT/NO antibacterial function achieved >99.9% inactivation of bacteria within 5 min. Furthermore, this synergetic antibacterial strategy could also be conveniently employed for highly efficient disinfection of a methicillin-resistant Staphylococcus aureus (MRSA) infected wound and promotion of the reconstruction of damaged tissues for in vivo MRSA-infected wound therapy.

Chitosan-based biomaterials for the treatment of bone disorders

Bone is an alive and dynamic organ that is well-differentiated and originated from mesenchymal tissues. Bone undergoes continuous remodeling during the lifetime of an individual. Although knowledge regarding bones and their disorders has been constantly growing, much attention has been devoted to effective treatments that can be used, both from materials and medical performance points of view. Polymers derived from natural sources, for example polysaccharides, are generally biocompatible and are therefore considered excellent candidates for various biomedical applications. This review outlines the development of chitosan-based biomaterials for the treatment of bone disorders including bone fracture, osteoporosis, osteoarthritis, arthritis rheumatoid, and osteosarcoma. Different examples of chitosan-based formulations in the form of gels, micro/nanoparticles, and films are discussed herein. The work also reviews recent patents and important developments related to the use of chitosan in the treatment of bone disorders. Although most of the cited research was accomplished before reaching the clinical application level, this manuscript summarizes the latest achievements within chitosan-based biomaterials used for the treatment of bone disorders and provides perspectives for future scientific activities.

Mechanically Competent Chitosan-Based Bioadhesive for Tendon-to-Bone Repair

Current suture-based surgical techniques used to repair torn rotator cuff tendons do not result in mechanically competent tendon-to-bone attachments, leading to high postoperative failure rates. Although adhesives have been proposed to protect against sutures tearing through tendon during healing, no currently available adhesive meets the clinical needs of adhesive strength, biocompatibility, and promotion of healing. Here, a biocompatible, graded, 3,4-dihydroxy phenyl chitosan (BGC) bioadhesive designed to meet these needs is presented. Although 3,4-dihydroxy phenyl chitosan (DP-chitosan) bioadhesives are biocompatible, their adhesion strength is low; soluble oxidants or cross-linking agents can be added for higher bonding strength, but this sacrifices biocompatibility. These challenges are overcome by developing a periodate-modified ion exchange resin-bead filtration system that oxidizes catechol moieties to quinones and filters off the activating agent and resin. The resulting BGC bioadhesive exhibited sixfold higher strength compared to commercially available tissue adhesives, with strength in the range necessary to improve tendon-to-bone repair (≈1MPa, ≈20% of current suture repair strength). The bioadhesive is biocompatible and promoted tenogenesis; cells exposed to the bioadhesive demonstrated enhanced expression of collagen I and the tenogenic marker Scx. Results demonstrated that the bioadhesive has the potential to improve the strength of a tendon-to-bone repair and promote healing.

Chitosan biological molecule improves bactericidal competence of ceftazidime against Burkholderia pseudomallei biofilms

Biofilm-associated Burkholderia pseudomallei infections (melioidosis) are problematic because of reduced sensitivity to antibiotics and high frequency of relapse. Biofilm dispersal agents are essential to liberate the biofilm-encased cells, which then become planktonic and are more susceptible to antibiotics. This study aimed to evaluate the ability of deacetylated chitosan (dCS), an antimicrobial and antibiofilm biological macromolecule, to disrupt established biofilms, thus enabling ceftazidime (CAZ) to kill biofilm-embedded B. pseudomallei. We combined dCS with CAZ using a mechanical stirring method to generate dCS/CAZ. In combination, 1.25-2.5 mg ml^-1 dCS/1-2 μg ml^-1 CAZ acted synergistically to kill cells more effectively than did either dCS or CAZ alone. Notably, a combination of 5-10 mg ml^-1 dCS with 256-512 μg ml^-1 CAZ, prepared either by mechanical stirring (dCS/CAZ) or mixing (dCS + CAZ), drastically improved bactericidal activities against biofilm cells leading to a 3-6 log CFU reduction. Confocal laser-scanning microscope (CLSM) images revealed that 10 mg ml^-1 dCS/512 μg ml^-1 CAZ is by far the best formulation to diminish B. pseudomallei biofilm biomass and produces the lowest live/dead cell ratios of B. pseudomallei in biofilm matrix. Collectively, these findings emphasize the potential of novel therapeutic antibacterial and antibiofilm agents to fight against antibiotic-tolerant B. pseudomallei biofilm-associated infections.

Planktonic and Biofilm-Associated Pseudomonas aeruginosa and Staphylococcus epidermidis Elicit Differential Human Peripheral Blood Cell Responses

Despite the considerable progress made in recent years, our understanding of the human immune response to microbial biofilms is still poor. The aim of the present study was to compare the in vitro response of human peripheral blood mononuclear cells (PBMC) to biofilms and planktonic cells of Pseudomonas aeruginosa and Staphylococcus epidermidis, two bacterial species particularly relevant in patients with cystic fibrosis or undergoing endovascular catheterization, respectively. PBMC isolated from healthy donors were co-cultured with 24 h-old biofilms or with exponentially growing cells of both species. Following 24 h of co-culture, the expression of early activation markers and the levels of cytokines in the culture supernatants were assessed by flow cytometry, while biofilm biomass and architecture were evaluated by crystal violet staining, CFU count, and confocal microscopy. Around 20% of PBMC was activated in response to both biofilms and planktonic cells of P. aeruginosa. In contrast, planktonic cells of S. epidermidis induced a statistically higher degree of activation than their biofilm counterpart (25% versus 15%; p < 0.01). P. aeruginosa biofilms stimulated pro-inflammatory (TNF-α, IL-1β, IFN-γ, and IL-6) and anti-inflammatory (IL-10) cytokine production at statistically significant levels higher than its planktonic counterpart, while an opposite trend was observed with S. epidermidis. Differences in the architecture of the biofilms and in the number of PBMC infiltrating the biofilms between the two bacterial species may at least partially explain these findings. Collectively, the results obtained highlighted marked differences in the host–cell response depending on the species and the mode of growth (biofilms versus planktonic cultures), allowing speculations on the different strategies adopted by P. aeruginosa and S. epidermidis to persist in the host during the course of chronic infections.

Effect of Poloxamer-Based Thermo-Sensitive Sol-Gel Agent on Upper Limb Dysfunction after Axillary Lymph Node Dissection: A Double-Blind Randomized Clinical Trial

PURPOSE

Restricted shoulder motion is a major morbidity associated with a lower quality of life and disability after axillary lymph node dissection (ALND) in patients with breast cancer. This study sought to evaluate the antiadhesive effect of a poloxamer-based thermosensitive sol-gel (PTAS) agent after ALND.

METHODS

We designed a double-blind, multicenter randomized controlled study to evaluate the clinical efficacy and safety of PTAS in reducing upper-limb dysfunction after ALND. The primary outcome was the change in the range of motion (ROM) of the shoulder before surgery and 4 weeks after ALND (early postoperative period). Secondary outcomes were shoulder ROM at six months, axillary web syndrome, and lymphedema (late postoperative period).

RESULTS

A total of 170 patients with planned ALND were randomly assigned to one of 2 groups (poloxamer and control) and 15 patients were excluded. In the poloxamer group (n = 76), PTAS was applied to the surface of the operative field after ALND. ALND was performed without the use of poloxamer in the control group (n = 79). Relative to the control group, the poloxamer group had significantly lower early postoperative restrictions in total shoulder ROM at four weeks (-30.04 ± 27.76 vs. -42.59 ± 36.79; p = 0.0236). In particular, the poloxamer group showed greater reductions in horizontal abduction at four weeks (-3.92 ± 9.80 vs. -10.25 ± 15.42; p = 0.0050). The ROM of the shoulder at 24 weeks, axillary web syndrome, and lymphedema were not significantly different between the two groups. No adverse effects were observed in either group.

CONCLUSION

We suggest that poloxamer might improve the early postoperative shoulder ROM in patients with breast cancer who have undergone ALND.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02967146.

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.

Antibacterial efficacy of quaternized chitosan coating on 3D printed titanium cage in rat intervertebral disc space

BACKGROUND CONTEXT

Infection around intervertebral fusion cages can be intractable because of the avascular nature of the intervertebral disc space. Intervertebral cages with antibacterial effects may be a method by which this complication can be prevented.

PURPOSE

To investigate the bacterial load on the antibacterial coating cages for spinal interbody fusion STUDY DESIGN: An experimental in vitro and in vivo study.

METHODS

Based on the micro-computed tomography (CT) data of rat caudal discs, mesh-like titanium (Ti) cages that anatomically fit into the discs were fabricated by three-dimensional (3D) printing. Additionally, an antibacterial coating was applied with quaternized chitosan (hydroxypropyltrimethyl ammonium chloride chitosan, HACC). In vitro release kinetics of the HACC was performed, and the antibacterial performance of the HACC-coated (Ti-HACC) cages (via inhibition zone assay, bacterial adhesion assay, and biofilm formation assay) was evaluated. Then, Ti-HACC- or noncoated (Ti) cages were implanted in the caudal discs of rats with bioluminescent Staphylococcus aureus. Bacterial survival was investigated using an in vivo imaging system (IVIS) on postoperative days 1, 3, and 5. On day 5, the infection-related changes (bone destruction and migration of cages) were assessed using micro-CT, and the healing status of the surgical wounds was also assessed. After the removal of the cages, the quantification of bacteria attached to the cages was obtained by IVIS. Histological evaluation was performed by hematoxylin and eosin staining and TRAP (tartrate-resistant acid phosphatase) staining.

RESULTS

Release kinetic analysis showed the sustained release of HACC over 3 days from Ti-HACC cages. Antibacterial effects of Ti-HACC cages were demonstrated in all in vitro assays. IVIS evaluation indicated that the in vivo implantation of Ti-HACC cages with S. aureus exhibited better wound healing, less infection-related changes on micro-CT, and reduced bacterial quantity in the extracted cages compared to Ti cages. Histological evaluation demonstrated an increased number of TRAP-positive osteoclasts and severe bone destruction in the rats treated with Ti cages.

CONCLUSIONS

We developed a novel antibacterial HACC-coated intervertebral cage that exhibited prominent antibacterial efficacy and prevented the structural damage caused by the infection in rat caudal discs.

CLINICAL SIGNIFICANCE

HACC-coated titanium intervertebral cages may be a promising option for preventing intractable postoperative infection in spinal interbody fusion surgery.

Does polysaccharide quaternization improve biological activity?

The natural polysaccharides, due to their structural diversity, commonly present very distinct solubility and physical chemical properties and additionally have intrinsic biological activities that, gene-rally, reveal themselves in a light way. The chemical modification of the molecular structure can improve these parameters. In this review, original articles that approached the quaternization of polysaccharides for purposes of biological application were selected, without limitation of year of publication, in the databases Scopus, Web of Science and PubMed. The results obtained from the bibliographic survey indicate that the increase in positive charges caused by quaternization improves the interaction between modified polysaccharides and structures that have negative charges on their surface, such as the cell wall of microorganisms and some cells in the human body, such as the DNA. This greater interaction is reflected as an increase in the biological activity of all polysaccharides broached in this study. Another important data obtained was the fact that the chemical changes did not affect or irrelevantly affect the toxicity of almost all of the polysaccharides that were quaternized. Therefore, polysaccharide quaternization is a safe and effective way to obtain improvements in the biological behavior of these macromolecules.

Antivirulence Properties of a Low-Molecular-Weight Quaternized Chitosan Derivative against Pseudomonas aeruginosa

The co-occurrence of increasing rates of resistance to current antibiotics and the paucity of novel antibiotics pose major challenges for the treatment of bacterial infections. In this scenario, treatments targeting bacterial virulence have gained considerable interest as they are expected to exert a weaker selection for resistance than conventional antibiotics. In a previous study, we demonstrated that a low-molecular-weight quaternized chitosan derivative, named QAL, displays antibiofilm activity against the major pathogen Pseudomonas aeruginosa at subinhibitory concentrations. The aim of this study was to investigate whether QAL was able to inhibit the production of relevant virulence factors of P. aeruginosa. When tested in vitro at subinhibiting concentrations (0.31-0.62 mg/mL), QAL markedly reduced the production of pyocyanin, pyoverdin, proteases, and LasA, as well as inhibited the swarming motility of three out of four P. aeruginosa strains tested. Furthermore, quantitative reverse transcription PCR (qRT-PCR) analyses demonstrated that expression of lasI and rhlI, two QS-related genes, was highly downregulated in a representative P. aeruginosa strain. Confocal scanning laser microscopy analysis suggested that FITC-labelled QAL accumulates intracellularly following incubation with P. aeruginosa. In contrast, the reduced production of virulence factors was not evidenced when QAL was used as the main polymeric component of polyelectrolyte-based nanoparticles. Additionally, combination of sub-MIC concentrations of QAL and tobramycin significantly reduced biofilm formation of P. aeruginosa, likely due to a synergistic activity towards planktonic bacteria. Overall, the results obtained demonstrated an antivirulence activity of QAL, possibly due to polymer intracellular localization and QS-inhibition, and its ability to inhibit P. aeruginosa growth synergizing with tobramycin.

Correction: Piras, A.M., et al. Antibacterial, Antibiofilm, and Antiadhesive Properties of Different Quaternized Chitosan Derivatives. Int. J. Mol. Sci. 2019, 20, 6297

The authors wish to make the following corrections to this paper [...].

Construction of novel antimicrobial peptide-modified extracellular matrix biologic scaffold material

In the field of implantable medical devices, the antibacterial extracellular matrix (ECM) biologic scaffold, which is constructed by modifying biomaterials with antibacterial peptides, has excellent potential. An antibacterial peptide-modified ECM scaffold was formed with chitosan (CS), antimicrobial peptide (AMP), and ECM scaffold. Chitosan has a firm positive-charge surface and can combine with the ECM scaffold material to form a positive-charge layer on the surface. The surface potential was characterized using a surface potential map. Infrared spectroscopy and scanning electron microscopy (SEM) were used to observe the scaffold surface characteristics and cell morphology. Fluorescence staining and MTS assay kit were used to assess cytotoxicity and biocompatibility. To evaluate the antibacterial and repairing effects on the infected wounds in vivo, a subcutaneous antibacterial test of rabbit back was conducted. The antibacterial peptide-modified ECM scaffold was successfully formed and presented an excellent three-dimensional micro-surface porous structure. The antibacterial peptide-modified ECM scaffold could be effectively-prepared by surface modification and activation. Fluorescence staining tests showed good cell adhesion, proliferation ability, and cell affinity. The in vivo experiment indicated that the antibacterial ECM scaffold had antibacterial and healing-promotion abilities.

Nanoparticles Based on Quaternary Ammonium Chitosan-methyl-β-cyclodextrin Conjugate for the Neuropeptide Dalargin Delivery to the Central Nervous System: An In Vitro Study

Peptide oral administration is a hard goal to reach, especially if the brain is the target site. The purpose of the present study was to set up a vehicle apt to promote oral absorption of the neuropeptide dalargin (DAL), allowing it to cross the intestinal mucosal barrier, resist enzymatic degradation, and transport drugs to the brain after crossing the blood–brain barrier. Therefore, a chitosan quaternary ammonium derivative was synthesized and conjugated with methyl-β-cyclodextrin to prepare DAL-medicated nanoparticles (DAL-NP). DAL-NP particle size was 227.7 nm, zeta potential +8.60 mV, encapsulation efficiency 89%. DAL-NP protected DAL from degradation by chymotrypsin or pancreatin and tripled DAL degradation time compared to non-encapsulated DAL. Use of DAL-NP was safe for either Caco-2 or bEnd.3 cells, with the latter selected as a blood–brain barrier model. DAL-NP could also cross either the Caco-2 or bEnd.3 monolayer by the transepithelial route. The results suggest a potential DAL-NP ability to transport to the brain a DAL dose fraction administered orally, although in vivo experiments will be needed to confirm the present data obtained in vitro.

Antimicrobial Nanogels with Nanoinjection Capabilities for Delivery of the Hydrophobic Antibacterial Agent Triclosan

With the ever-growing problem of antibiotic resistance, developing antimicrobial strategies is urgently needed. Herein, a hydrophobic drug delivery nanocarrier is developed for combating planktonic bacteria that enhances the efficiency of the hydrophobic antimicrobial agent, Triclosan, up to a 1000 times. The poly(N-isopropylacrylamide-co-N-[3-(dimethylamino)propyl]methacrylamide), p(NIPAM-co-DMAPMA), based nanogel is prepared via a one-pot precipitation polymerization, followed by quaternization with 1-bromododecane to form hydrophobic domains inside the nanogel network through intraparticle self-assembly of the aliphatic chains (C12). Triclosan, as the model hydrophobic antimicrobial drug, is loaded within the hydrophobic domains inside the nanogel. The nanogel can adhere to the bacterial cell wall via electrostatic interactions and induce membrane destruction via the insertion of the aliphatic chains into the cell membrane. The hydrophobic antimicrobial Triclosan can be actively injected into the cell through the destroyed membrane. This approach dramatically increases the effective concentration of Triclosan at the bacterial site. Both the minimal inhibitory concentration and minimal bactericidal concentration against the Gram-positive bacteria S. aureus and S. epidermidis decreased 3 orders of magnitude, compared to free Triclosan. The synergy of physical destruction and active nanoinjection significantly enhances the antimicrobial efficacy, and the designed nanoinjection delivery system holds great promise for combating antimicrobial resistance as well as the applications of hydrophobic drugs delivery for many other possible applications.

Quaternary Ammonium Chitosans: The Importance of the Positive Fixed Charge of the Drug Delivery Systems

As a natural polysaccharide, chitosan has good biocompatibility, biodegradability and biosecurity. The hydroxyl and amino groups present in its structure make it an extremely versatile and chemically modifiable material. In recent years, various synthetic strategies have been used to modify chitosan, mainly to solve the problem of its insolubility in neutral physiological fluids. Thus, derivatives with negative or positive fixed charge were synthesized and used to prepare innovative drug delivery systems. Positively charged conjugates showed improved properties compared to unmodified chitosan. In this review the main quaternary ammonium derivatives of chitosan will be considered, their preparation and their applications will be described to evaluate the impact of the positive fixed charge on the improvement of the properties of the drug delivery systems based on these polymers. Furthermore, the performances of the proposed systems resulting from in vitro and ex vivo experiments will be taken into consideration, with particular attention to cytotoxicity of systems, and their ability to promote drug absorption.

Positively Charged Polymers as Promising Devices against Multidrug Resistant Gram-Negative Bacteria: A Review

Antibiotic resistance has increased markedly in Gram-negative bacteria, causing severe infections intractable with traditional drugs and amplifying mortality and healthcare costs. Consequently, to find novel antimicrobial compounds, active on multidrug resistant bacteria, is mandatory. In this regard, cationic antimicrobial peptides (CAMPs)—able to kill pathogens on contact—could represent an appealing solution. However, low selectivity, hemolytic toxicity and cost of manufacturing, hamper their massive clinical application. In the recent years—starting from CAMPs as template molecules—less toxic and lower-cost synthetic mimics of CAMPs, including cationic peptides, polymers and dendrimers, have been developed. Although the pending issue of hemolytic toxicity and biodegradability is still left not completely solved, cationic antimicrobial polymers (CAPs), compared to small drug molecules, thanks to their high molecular weight, own appreciable selectivity, reduced toxicity toward eukaryotic cells, more long-term activity, stability and non-volatility. With this background, an updated overview concerning the main manufactured types of CAPs, active on Gram-negative bacteria, is herein reported, including synthetic procedure and action’s mechanism. Information about their structures, antibacterial activity, advantages and drawbacks, was reported in the form of tables, which allow faster consultation and quicker learning concerning current CAPs state of the art, in order not to retrace reviews already available.