Amphiphilic quaternary ammonium chitosans self-assemble onto bacterial and fungal biofilms and kill adherent microorganisms

Quaternary ammonium chitosan-functionalized mesoporous silica nanoparticles: A promising targeted drug delivery system for the treatment of intracellular MRSA infection

The limited membrane permeability and bacterial resistance pose significant challenges in the management of intracellular drug-resistant bacterial infections. To overcome this issue, we developed a bacterial-targeted drug delivery system based on quaternary ammonium chitosan-modified mesoporous silica nanoparticles (MSN-NH2-CFP@HACC) for the treatment of intracellular Methicillin-resistant Staphylococcus aureus (MRSA) infections. This system utilizes amino-functionalized mesoporous silica nanoparticles to efficiently load cefoperazone (CFP), and the nanoparticles' surface is coated with 2-hydroxypropyltrimethyl ammonium chloride chitosan (HACC) to target bacteria and enhance macrophage uptake. The findings indicate that MSN-NH2-CFP@HACC nanoparticles are efficiently internalized by macrophages, demonstrate accelerated drug release in acidic environments, and exhibit enhanced antibacterial properties, effectively suppressing the proliferation and intracellular escape of MRSA. Moreover, HACC enhances the bacterial capture ability of the nanoparticles and reduces resistance by disrupting bacterial membrane structures and inhibiting bacterial β-lactamase activity. In a murine model of MRSA bacteremia, MSN-NH2-CFP@HACC exhibited remarkable antibacterial efficacy and significantly attenuated severe inflammatory responses. In conclusion, MSN-NH2-CFP@HACC represent a promising antibiotic delivery system with exceptional antibacterial efficacy and favorable biocompatibility, thus presenting a novel strategy for addressing intracellular drug-resistant bacterial infections and demonstrating significant potential for clinical application.

Preparation of N-(2-hydroxypropyltrimonium chloride)-O-dodecylylpyridine chitosan quaternary ammonium salt and its antibacterial activities

Chitosan derivatives, including O-carboxymethyl chitosan (CMC), N-(2-hydroxypropyltrimonium chloride)-O-carboxymethyl chitosan (QCMC), and N-(2-hydroxypropyltrimonium chloride)-O-dodecylylpyridine chitosan quaternary ammonium salt (DQCMC), were synthesized and characterized using Fourier transform infrared (FTIR) spectroscopy, 1H nuclear magnetic resonance (1H NMR) spectroscopy, Ultraviolet-visible (UV-vis) spectroscopy, and element analysis (EA). The antibacterial activities of chitosan and chitosan derivatives against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were evaluated through the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and antibacterial rate assays. Results demonstrated that DQCMC exhibited significantly higher antibacterial efficacy compared to chitosan, CMC, and QCMC. The MIC of DQCMC against E. coli and S. aureus were 31 μg/mL and 7 μg/mL, respectively, with a 100 % antibacterial rate at a concentration of 0.5 mg/mL. Furthermore, assessment of mouse fibroblast (L929) cell viability using cell counting kit-8 (CCK-8) methods revealed no toxicity associated with the material.

Effect of the structure of chitosan quaternary ammonium salts with different spacer groups on antibacterial and antibiofilm activities

In this study, three types of dodecyl chitosan quaternary ammonium salts, each with different spacer groups were synthesized. These chitosan derivatives are N',N'-dimethyl-N'-dodecyl-ammonium chloride-N-amino-acetyl chitosan (DMDAC), N'-dodecyl-N-isonicotinyl chitosan chloride (DINCC) and N',N'-dimethyl-N'-dodecyl-ammonium chloride-N-benzoyl chitosan (DMDBC). The synthesized products were characterized using Fourier transform infrared spectrometers, nuclear magnetic resonance, thermogravimetric analysis, and elemental analysis. The antibacterial and antibiofilm activities against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were investigated. The experimental results indicated that the introduction of hydrophobic groups of spacer groups could enhance the antibacterial and antibiofilm activities of the chitosan derivatives. The antibacterial rates of the chitosan derivatives were over 90 % for both E. coli and S. aureus at a concentration of 0.5 mg/mL. The chitosan derivatives removed >50 % of the mature biofilm of E. coli and over 90 % of the mature biofilm of S. aureus at a concentration of 2.5 mg/mL. Further, the synthesized chitosan derivatives were determined to be non-toxic to L929 cells. Among them, DMDBC exhibited the most promising overall performance and show potential for wide-ranging applications in food preservation, disinfectants, medical, and other fields.

Ultraefficient OG-Mediated Photodynamic Inactivation Mechanism for Ablation of Bacteria and Biofilms in Water Augmented by Potassium Iodide under Blue Light Irradiation

While photodynamic inactivation (PDI) has emerged as a novel sterilization strategy for drinking water treatment that recently attracted tremendous attention, its efficiency needs to be further improved. In this study, we aimed to clarify the ultraefficient mechanism by which potassium iodide (KI) potentiates octyl gallate (OG)-mediated PDI against bacteria and biofilms in water. When OG (0.15 mM) and bacteria were exposed to blue light (BL, 420 nm, 210 mW/cm2), complete sterilization (>7.5 Log cfu/mL of killing) was achieved by the addition of KI (250 mM) within only 5 min (63.9 J/cm2). In addition, at lower doses of OG (0.1 mM) with KI (100 mM), the biofilm was completely eradicated within 10 min (127.8 J/cm2). The KI-potentiated mechanism involves in situ rapid photogeneration of a multitude of reactive oxygen species, especially hydroxyl radicals (•OH), reactive iodine species, and new photocytocidal substances (quinone) by multiple photochemical pathways, which led to the destruction of cell membranes and membrane proteins, the cleavage of genomic DNA and extracellular DNA within biofilms, and the degradation of QS signaling molecules. This multitarget synergistic strategy provided new insights into the development of an environmentally friendly, safe, and ultraefficient photodynamic drinking water sterilization technology.

Effect of the structure of chitosan quaternary phosphonium salt and chitosan quaternary ammonium salt on the antibacterial and antibiofilm activity

N-(4-N', N', N'-trimethylphosphonium chloride) benzoyl chitosan (TMPCS), N-(4-N', N', N'-triphenylphosphonium chloride) benzoyl chitosan (TPPCS), and N-(4-N', N', N'-trimethylmethanaminium chloride) benzoyl chitosan (TMACS) were synthesized. The structures of the products were characterized by Fourier transform infrared spectroscopy, Nuclear magnetic resonance spectroscopy and ultraviolet-visible spectroscopy. Their antibacterial activities against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were investigated in vitro using the antibacterial rate, minimal inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), the antibiofilm activity was investigated by crystal violet assay. The antibacterial assessment revealed that the chitosan quaternary phosphonium salts of similar structure had superior antibacterial activity than chitosan quaternary ammonium salt. The antibacterial rate of CS, TMPCS, TPPCS and TMACS against E. coli at 0.5 mg/mL was 10.4 %, 42.0 %, 58.5 % and 21.6 % respectively. At the same concentration, the antibacterial rate of TMPCS, TPPCS and TMACS against S.aureus was all up to 100 %. The biofilm inhibition rate of CS, TMPCS, TPPCS and TMACS at a half of MIC against E.coli was 28.4 %, 33.9 %, 56.6 % and 57.6 % respectively, and against S.aureus was 30.8 %, 53.8 %, 62.2 % and 58.5 % respectively. The biofilm removal rate of CS, TMPCS, TPPCS, TMACS against E.coli at 2.5 mg/mL was 20.6 %, 46.4 %, 48.9 % and 41.6 % respectively, and against S.aureus at 2.5 mg/mL was 41.5 %, 60.4 %, 69.9 % and 59.01 % respectively.

From Antibacterial to Antibiofilm Targeting: An Emerging Paradigm Shift in the Development of Quaternary Ammonium Compounds (QACs)

In a previous development stage, mostly individual antibacterial activity was a target in the optimization of biologically active compounds and antiseptic agents. Although this targeting is still valuable, a new trend has appeared since the discovery of superhigh resistance of bacterial cells upon their aggregation into groups. Indeed, it is now well established that the great majority of pathogenic germs are found in the environment as surface-associated microbial communities called biofilms. The protective properties of biofilms and microbial resistance, even to high concentrations of biocides, cause many chronic infections in medical settings and lead to serious economic losses in various areas. A paradigm shift from individual bacterial targeting to also affecting more complex cellular frameworks is taking place and involves multiple strategies for combating biofilms with compounds that are effective at different stages of microbiome formation. Quaternary ammonium compounds (QACs) play a key role in many of these treatments and prophylactic techniques on the basis of both the use of individual antibacterial agents and combination technologies. In this review, we summarize the literature data on the effectiveness of using commercially available and newly synthesized QACs, as well as synergistic treatment techniques based on them. As an important focus, techniques for developing and applying antimicrobial coatings that prevent the formation of biofilms on various surfaces over time are discussed. The information analyzed in this review will be useful to researchers and engineers working in many fields, including the development of a new generation of applied materials; understanding biofilm surface growth; and conducting research in medical, pharmaceutical, and materials sciences. Although regular studies of antibacterial activity are still widely conducted, a promising new trend is also to evaluate antibiofilm activity in a comprehensive study in order to meet the current requirements for the development of highly needed practical applications.

Synthesis and characterization of thiazolium chitosan derivative with enhanced antimicrobial properties and its use as component of chitosan based films

In this work, chemical modification of chitosan using cationic thiazolium groups was investigated with the aim to improve water solubility and antimicrobial properties of chitosan. Enzymatic synthesis and ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS) chemistry were employed to synthesize and attach to chitosan through the amine groups the molecule bearing thiazolium moieties, quaternized 4-(2-(4-methylthiazol-5-yl) ethoxy)-4-oxobutanoic acid (MTBAQ). On the basis of Fourier transform infrared spectroscopy (FTIR), elemental analysis and solid state nuclear magnetic resonance (ssNMR), around 95 % of the available amine groups of chitosan (of 25 % degree of acetylation) reacted. The resulting derivative was water soluble at physiological pH and exhibit excellent antimicrobial activity against Listeria innocua, Staphylococcus epidermidis, Staphylococcus aureus and Methicillin Resistant S. aureus Gram-positive bacteria (MIC = 8-32 μg/ mL), whereas its efficiency decreases against fungi Candida albicans and Eschericia coli Gram-negative bacterium. Subsequently, the thiazolium chitosan derivative was employed as antimicrobial component (up to 7 wt%) of chitosan/glycerol based films. The incorporation of the chitosan derivative does not modify significantly the characteristics of the film in terms of thermal and mechanical properties, while enhances considerably the antimicrobial activity.

Polysaccharides to combat viruses (Covid-19) and microbes: New updates

COVID-19, which is speedily distributed across the world and presents a significant challenge to public health, is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Following MERS coronavirus (MERS-CoV) and SARS, this is the third severe coronavirus outbreak in less than 20 years. To date, there are no exact agents and vaccines available for the treatment of COVID-19 that are clinically successful. Antimicrobial medications are effective in controlling infectious diseases. However, the extensive use of antibiotics makes microbes more resistant to drugs and demands novel bioactive agents' development. Polysaccharides are currently commonly used in the biomedical and pharmaceutical industries for their remarkable applications. Polysaccharides appear to have a wide range of anti-virus (anti-coronavirus) and antimicrobial applications. Polysaccharides are able to induce bacterial cell membrane disruption as they demonstrate potency in binding onto the surfaces of microbial cells. Here, the antiviral mechanisms of such polysaccharides and their success in the application of antiviral infections are reviewed. Additionally, this report provides a summary of current advancements of well-recognized polysaccharides as antimicrobial and anti-biofilm agents.

Ultra-efficient antimicrobial photodynamic inactivation system based on blue light and octyl gallate for ablation of planktonic bacteria and biofilms of Pseudomonas fluorescens

Pseudomonas fluorescens is a Gram-negative spoilage bacterium and dense biofilm producer, causing food spoilage and persistent contamination. Here, we report an ultra-efficient photodynamic inactivation (PDI) system based on blue light (BL) and octyl gallate (OG) to eradicate bacteria and biofilms of P. fluorescens. OG-mediated PDI could lead to a > 5-Log reduction of viable cell counts within 15 min for P. fluorescens. The activity is exerted through rapid penetration of OG towards the cells with the generation of a high-level toxic reactive oxygen species triggered by BL irradiation. Moreover, OG plus BL irradiation can efficiently not only prevent the formation of biofilms but also scavenge the existing biofilms. Additionally, it was shown that the combination of OG/poly(lactic acid) electrospun nanofibers and BL have great potential as antimicrobial packagings for maintaining the freshness of the salamander storge. These prove that OG-mediated PDI can provide a superior platform for eradicating bacteria and biofilm.

Synergistic Photoantimicrobial Chemotherapy of Methylene Blue-Encapsulated Chitosan on Biofilm-Contaminated Titanium

Intensive efforts have been made to eliminate or substantial reduce bacterial adhesion and biofilm formation on titanium implants. However, in the management of peri-implantitis, the methylene blue (MB) photosensitizer commonly used in photoantimicrobial chemotherapy (PACT) is limited to a low retention on the implant surface. The purpose of this study was to assess enhancive effect of water-soluble quaternary ammonium chitosan (QTS) on MB retention on biofilm-infected SLA (sandblasted, large grid, and acid-etched) Ti alloy surfaces in vitro. The effectiveness of QTS + MB with different concentrations in eliminating Gram-negative A. actinomycetemcomitans or Gram-positive S. mutans bacteria was compared before and after PACT. Bacterial counting and lipopolysaccharide (LPS) detection were examined, and then the growth of human osteoblast-like MG63 cells was evaluated. The results indicated that the synergistic QTS + MB with retention ability significantly decreased the biofilm accumulation on the Ti alloy surface, which was better than the same concentration of 1 wt% methyl cellulose (MC). More importantly, the osteogenic activity of MG63 cells on the disinfected sample treated by QTS + MB-PACT modality was comparable to that of sterile Ti control, significantly higher than that by MC + MB-PACT modality. It is concluded that, in terms of improved retention efficacy, effective bacteria eradication, and enhanced cell growth, synergistically, PACT using the 100 μg/mL MB-encapsulated 1% QTS was a promising modality for the treatment of peri-implantitis.

Recent Progress in Bile Acid-Based Antimicrobials

With the emergence of drug-resistant bacteria and the formation of biofilms by bacteria and fungi, microbial infections gradually threaten global health. Natural antimicrobial peptides (AMPs) have low susceptibility for developing resistance due to the membrane targeted mechanism, but instability and high manufacturing cost limit their applications in clinic. Bile acids, a group of steroids in the human body, with high stability, biocompatibility, and inherent facial amphiphilic structure similar to the characteristics of AMPs, have been applied to the biological field, such as drug delivery systems, self-healing hydrogels, antimicrobials, and so on. In this review, we mainly focus on the different classes of bile acid-based antimicrobials in recent years. Various designs and methods for the preparation of unimolecular antimicrobials with bile acid skeletons are first introduced, including coupling of primary amine, quaternary ammonium, and amino acid units with bile acid skeletons. Some representative oligomeric antimicrobials, including dimers of bile acids, are summarized. Finally, macromolecular antimicrobials bearing some positive charges at the main chain or side chain and interaction mechanisms of these bile acid-based antimicrobials are discussed.

Imminent antimicrobial bioink deploying cellulose, alginate, EPS and synthetic polymers for 3D bioprinting of tissue constructs

3D printing, one of its kinds has been a recent technological trend to fabricate complex and patterned biomaterial with controlled precision. With the conventional kick-start of printing metals and plastics, advancements in printing viable cells, polysaccharides or microbes themselves have been achieved. The additive antimicrobial properties in bioinks sourced from organic and inorganic materials have profound implications in tissue engineering. Cellulose, alginate, exopolysaccharides, ceramics and synthetic polymers are integrated as a viable component in inks and used for bio-printing. To date, bacterial infection and immunogenicity pose a potential health risk during a tissue implant or bone substitution. In order to mitigate microbial infection, antimicrobial bioinks with significant antimicrobial potential have been the much sought after strategies. This approach could be an effective frontline defense against microbial interference in tissue engineering and biomedical applications. An overview on the antimicrobial potential of polysaccharides as bioinks for 3D bioprinting has been critically reviewed.

Preparation of sulfatide mimicking oleic acid sulfated chitosan as a potential inhibitor for metastasis

Sulfatide is associated with numerous health problems, affecting different parts of the human body, including the metastasis; however, the underlying mechanisms are yet to be fully elucidated. Sulfatide has been used to potential inhibitor for tumor cell metastasis. In the present study we synthesized oleic acid sulfated chitosan (OlcShCs). It shows structural similarity to sulfatide because of its functional groups (sulfate and fatty acyl chains). Chitosan has smart properties such as biocompatibility, biodegradability and non-toxicity. We have prepared oleic acid sulfated chitosan (OlcShCs) by chitosan modification to mimic sulfatide. Its structure was characterized by FT-IR, H-NMR, and thermogravimetric analysis. After characterization studies its antimicrobial, antifungal and cytotoxic properties were investigated. Oleic acid sulfated chitosan (OlcShCs) was tested for its anti-cancer potential against human cancer cell lines (HeLa (ATCC® CCL-2™)) for 24 h, 48 h and 72 h using the MTT assays. This new material which is soluble at physiological conditions, is a potential candidate for further metastasis inhibition investigations.

Bio-Based Polymers with Antimicrobial Properties towards Sustainable Development

This article concisely reviews the most recent contributions to the development of sustainable bio-based polymers with antimicrobial properties. This is because some of the main problems that humanity faces, nowadays and in the future, are climate change and bacterial multi-resistance. Therefore, scientists are trying to provide solutions to these problems. In an attempt to organize these antimicrobial sustainable materials, we have classified them into the main families; i.e., polysaccharides, proteins/polypeptides, polyesters, and polyurethanes. The review then summarizes the most recent antimicrobial aspects of these sustainable materials with antimicrobial performance considering their main potential applications in the biomedical field and in the food industry. Furthermore, their use in other fields, such as water purification and coating technology, is also described. Finally, some concluding remarks will point out the promise of this theme.