Measurement and evaluation of the effects of pH gradients on the antimicrobial and antivirulence activities of chitosan nanoparticles in Pseudomonas aeruginosa

Advances in ionic liquid-based antimicrobial wound healing platforms

Wound infections, marked by the proliferation of microorganisms at surgical sites, necessitate the development of innovative wound dressings with potent bactericidal properties to curb microbial growth and prevent bacterial infiltration. This study explores the recent strides in utilizing ionic liquid-based polymers as highly promising antimicrobial agents for advanced wound healing applications. Specifically, cationic polymers containing quaternary ammonium, imidazolium, guanidinium, pyridinium, triazolium, or phosphonium groups have emerged as exceptionally effective antimicrobial compounds. Their mechanism of action involves disrupting bacterial membranes, thereby preventing the development of resistance and minimizing toxicity to mammalian cells. This comprehensive review not only elucidates the intricate dynamics of the skin's immune response and the various stages of wound healing but also delves into the synthesis methodologies of ionic liquid-based polymers. By spotlighting the practical applications of antimicrobial wound dressings, particularly those incorporating ionic liquid-based materials, this review aims to lay the groundwork for future research endeavors in this burgeoning field. Through a nuanced examination of these advancements, this article seeks to contribute to the ongoing progress in developing cutting-edge wound healing platforms that can effectively address the challenges posed by microbial infections in surgical wounds.

Rhamnolipid production by Pseudomonas aeruginosa (SSL-4) on waste engine oil (WEO): Taguchi optimization, soil remediation, and phytotoxicity investigation

ABSTRACTEnvironmental concerns and rising biosurfactant demand emphasize the need for this study. The objective is to maximize rhamnolipid-biosurfactant production by Pseudomonas aeruginosa (SSL-4) utilizing waste engine oil (WEO) as the sole substrate for use in soil bioremediation and commercial production. Using an L16 Taguchi orthogonal array, a signal-to-noise ratio, and an analysis of variance (ANOVA), the effects of environmental (pH, incubation temperature) and dietary parameters (carbon source concentration, carbon/nitrogen (C/N) and carbon/phosphorus (C/P) ratio) are examined. Variations of the following parameters were made within a carefully selected range: incubation temperature of 25-40℃, pH range of 5-11, WEO concentration of 1-7% (v/v), and C/N and C/P ratios of 10-40. Response variables in this batch study include surface tension reduction (mN/m), dry cell biomass (DCBM) (g/L), and rhamnolipids yield based on substrate consumption, YP/S (g/g). Rhamnolipid was synthesized under optimal conditions, providing a yield of 21.42 g/g. The oil recovery of 74.05 ± 1.481% was achieved from oil-contaminated soil at a CMC of ∼70 mg/L. FTIR, 1H NMR, and UPLC-MS techniques were utilized for the characterization of rhamnolipids, and AAS for determining heavy metals concentration in WEO and residual waste engine oil (RWEO). The Germination Index (GI) of ∼82.55% indicated no phytotoxicity associated with synthesized rhamnolipid.

Chitosan loaded RNA polymerase inhibitor nanoparticles increased attenuation in toxin release from Streptococcus pneumonia

BACKGROUND

Multidrug-resistant (MDR) bacterial infections have become an emerging health concern around the world. Antibiotics resistance among S. pneumoniae strains increased recently contributing to increase in incidence of pneumococcal infection. This necessitates the discovery of novel antipnemococcal such as compound C3-005 which target the interaction between RNA polymerase and σ factors. Chitosan nanoparticles (CNPs) exhibited antibacterial activity including S. pneumonia. Therefore, the aims of the current investigation were to formulate CNPs loaded with C3-005 and characteristic their antimicrobial properties against S. pneumonia.

METHODS

The CNPs and C3-005 loaded CNPs were produced utilizing ionic gelation method, and their physicochemical characteristics including particle size, zeta potential, polydispersity index (PDI), encapsulation efficiency (EE%), and in vitro release profile were studied. Both differential scanning calorimetry (DSC) and fourier transform infrared spectroscopy (FTIR) were used for chemical characterization. The synthesized NPs' minimum inhibitory concentration (MIC) was determined using killing assay and broth dilution method, and their impact on bacteria induced hemolysis were also studied.

RESULTS

The NPs encapsulating C3-005 were successfully prepared with particle size of 343.5 nm ± 1.3, zeta potential of 29.8 ± 0.37, and PDI of 0.20 ± 0.03. 70 % of C3-005 were encapsulated in CNPs and sustained release pattern of C3-005 from CNPs was revealed by an in vitro release study. CNPs containing C3-005 exhibited higher antipnomcoccal activity with MIC50 of 30 µg/ml when compared with C3-005 and empty CNPs alone. The prepared C3-CNPs showed a reduction of bacterial hemolysis in a concentration-related (dependent) manner and was higher than C3-005 alone.

CONCLUSIONS

The findings of this study showed the potential for using C3-005 loaded CNPs to treat pneumococcal infection.

Chitosan as a potential biomaterial for the management of oral mucositis, a common complication of cancer treatment

Oral mucositis is a serious issue in patients receiving oncological therapies. Mucosal protectants considered to be one of the preferred choices used in the management of mucositis. However, the protective efficacy of currently available mucosal protectants has been significantly compromised due to poor retention, lack of lubrication, poor biodegradability, and inability to manage secondary complications. Chitosan is a promising material for mucosal applications due to its beneficial biomedical properties. Chitosan is also anti-inflammatory, anti-microbial, and capable of scavenging free radicals, makes it a good candidate for the treatment of oral mucositis. Additionally, chitosan's amino polysaccharide skeleton permits a number of chemical alterations with better bioactive performance. This article provides a summary of key biological properties of chitosan and its derivatives that are useful for treating oral mucositis. Current literature evidence shows that Chitosan has superior mucosal protective properties when utilised alone or as delivery systems for co-encapsulated drugs.

Insights into the Biocompatibility and Biological Potential of a Chitosan Nanoencapsulated Textile Dye

Traditionally synthetic textile dyes are hazardous and toxic compounds devoid of any biological activity. As nanoencapsulation of yellow everzol textile dye with chitosan has been shown to produce biocompatible nanoparticles which were still capable of dyeing textiles, this work aims to further characterize the biocompatibility of yellow everzol nanoparticles (NPs) and to ascertain if the produced nanoencapsulated dyes possess any biological activity against various skin pathogens in vitro assays and in a cell infection model. The results showed that the NPs had no deleterious effects on the HaCat cells' metabolism and cell wall, contrary to the high toxicity of the dye. The biological activity evaluation showed that NPs had a significant antimicrobial activity, with low MICs (0.5-2 mg/mL) and MBCs (1-3 mg/mL) being registered. Additionally, NPs inhibited biofilm formation of all tested microorganisms (inhibitions between 30 and 87%) and biofilm quorum sensing. Lastly, the dye NPs were effective in managing MRSA infection of HaCat cells as they significantly reduced intracellular and extracellular bacterial counts.

Attenuation of Pseudomonas aeruginosa Quorum Sensing Virulence of Biofilm and Pyocyanin by mBTL-Loaded Calcium Alginate Nanoparticles

Pseudomonas aeruginosa contributes to many chronic infections and has been found to be resistant to multiple antibiotics. Pseudomonas use a quorum sensing system (QS) to control biofilm establishment and virulence factors, and, thus, quorum sensing inhibitors (QSIs), such as meta-bromo-thiolactone (mBTL), are promising anti-infective agents. Accordingly, this study intended to investigate the antibacterial and anti-virulence activity of mBTL-loaded calcium alginate nanoparticles (CANPs) against Pseudomonas aeruginosa and different QS mutants. The results show that the mBTL-CANPs had higher antibacterial activity, which was made evident by decreases in all tested strains except the ∆lasR/∆rhlR double mutant, with MIC₅₀ (0.5 mg/mL) of mBTL-CANPs compared with free mBTL at MIC₅₀ (˃1 mg/mL). The biofilm formation of P. aeruginosa and some QS-deficient mutants were reduced in response to 0.5-0.125 mg/mL of mBTL-encapsulating CANPs. The pyocyanin production of the tested strains except ∆lasA and ∆rhlR decreased when challenged with 0.5 mg/mL of mBTL-loaded NPs. The subsequent characterization of the cytotoxic effect of these NPs on human lung epithelial cells (A549) and cystic fibrosis fibroblast cells (LL 29) demonstrated that synthesized NPs were cytocompatible at MIC₅₀ in both cell lines and markedly reduced the cytotoxic effect observed with mBTL alone on these cells. The resulting formulation reduced the P. aeruginosa strains' adhesion to A549 comparably with mBTL, suggesting their potential anti-adhesive effect. Given the virulence suppressing action, cytocompatibility, and enhanced anti-biofilm effect of mBTL-CANPs, and the advantage of alginate-based NPs as an antimicrobial delivery system these nanoparticles have great potential in the prophylaxis and treatment of infection caused by Pseudomonas aeruginosa.

Efficient epidermal delivery of antibiotics by self-assembled lecithin/chitosan nanoparticles for enhanced therapy on epidermal bacterial infections

The treatment for epidermal bacterial infections has become a primary healthy concern, producing a significant therapeutic challenge. Here we present a facile strategy to fabricate lecithin/chitosan nanoparticles (LCNPs) for efficient epidermal drug delivery over epidermal bacterial infections. The central rotatable composite design method was used for the optimization of the preparation, and that the optimal size (212.63 ± 1.95 nm) was obtained via analysis of variance (ANOVA). The prepared CIP-LCNPs show an average diameter of 325.9 ± 7.4 nm and a zeta potential of 26.6 ± 1.2 mV. Antibiotics can be well encapsulated in LCNPs and its release kinetics is studied with cumulative release of 93.81 ± 2.05 % for 48 h. The hemolytic activity, cytotoxicity, and skin irritation are further investigated. The zones of inhibition are 2.16 ± 0.04 cm and 2.92 ± 0.03 cm for Escherichia coli and Staphylococcus aureus, respectively. Moreover, in vitro permeation studies demonstrate that LCNPs can increase the accumulation of antibiotics in the epidermis with retention ratio 2-3 fold higher than commercial formulations. The in vivo result over epidermal-infected wound demonstrates the superior therapeutic effects of LCNPs. The developed LCNPs represent an important advance in fabricating therapeutic materials for enhanced therapy over epidermal bacterial infections.

Cationic polymer contributes to broaden the spectrum of vancomycin activity achieving eradication of Pseudomonas aeruginosa

Vancomycin (VAN) is unable to penetrate the outer membrane of Gram-negative bacteria and reach the target site. One approach to overcome this limitation is to associate it with compounds with permeabilizing or antimicrobial properties. Eudragit E100^® (Eu) is a cationic polymer insufficiently characterized for its potential antimicrobial action. Eu-VAN combinations were characterized, the antimicrobial efficacy against Pseudomonas aeruginosa was evaluated and previous studies on the effects of Eu on bacterial envelopes were extended. Time-kill assays showed eradication of P. aeruginosa within 3-6 h exposure to Eu-VAN, whilst VAN was ineffective. Eu showed regrowth in 24 h and delayed colony pigmentation. Although permeabilization of bacterial envelopes or morphological alterations observed by TEM and flow cytometry after exposure to Eu were insufficient to cause bacterial death, they allowed access of VAN to the target site, since Eu-VAN/Van-FL-treated cultures showed fluorescent staining in all bacterial cells, indicating Van-FL internalization. Consequently, Eu potentiated the activity of an otherwise inactive antibiotic against P. aeruginosa. Moreover, Eu-VAN combinations exhibited improved physicochemical properties and could be used in the development of therapeutic alternatives in the treatment of bacterial keratitis.

Biopolymeric Nanoparticles-Multifunctional Materials of the Future

Nanotechnology plays an important role in biological research, especially in the development of delivery systems with lower toxicity and greater efficiency. These include not only metallic nanoparticles, but also biopolymeric nanoparticles. Biopolymeric nanoparticles (BPNs) are mainly developed for their provision of several advantages, such as biocompatibility, biodegradability, and minimal toxicity, in addition to the general advantages of nanoparticles. Therefore, given that biopolymers are biodegradable, natural, and environmentally friendly, they have attracted great attention due to their multiple applications in biomedicine, such as drug delivery, antibacterial activity, etc. This review on biopolymeric nanoparticles highlights their various synthesis methods, such as the ionic gelation method, nanoprecipitation method, and microemulsion method. In addition, the review also covers the applications of biodegradable polymeric nanoparticles in different areas-especially in the pharmaceutical, biomedical, and agricultural domains. In conclusion, the present review highlights recent advances in the synthesis and applications of biopolymeric nanoparticles and presents both fundamental and applied aspects that can be used for further development in the field of biopolymeric nanoparticles.

Chitosan Enhances the Anti-Biofilm Activity of Biodentine against an Interkingdom Biofilm Model

Endodontic infection is a biofilm disease that is difficult to irradicate with current treatment protocols, and as such, persistent micro-organisms may lead to ongoing or recurrent disease. The potential for the use of enhanced filling materials to modify biofilm regrowth is a promising strategy. This current study aimed to evaluate the anti-biofilm efficacy of calcium silicate cements modified with chitosan. The development of mono-species and multi-species biofilms on ProRoot MTA, Biodentine and bovine dentine discs were explored using quantitative microbiology analysis. The effect on regrowth of biofilms was assessed following the addition of chitosan to each cement. In comparison to a dentine substrate, both materials did not show the ability to inhibit biofilm regrowth. Biodentine incorporated with chitosan displayed a dose-dependent reduction in multi-species biofilm regrowth, unlike MTA. Notably, interkingdom biofilms were shown to enhance bacterial tolerance in the presence of chitosan. This study demonstrates the potential to enhance the antimicrobial properties of Biodentine. The findings highlight the need for appropriate model systems when exploring antimicrobial properties of materials in vitro so that interspecies and interkingdom interactions that modify tolerance are not overlooked while still supporting the development of innovative materials.

Capsule Independent Antimicrobial Activity Induced by Nanochitosan against Streptococcus pneumoniae

Background: Streptococcus pneumoniae remains a major cause of community-acquired pneumonia, meningitis, and other diseases, contributing significantly to high morbidity and mortality worldwide. Although it responds to antibiotics, their use is becoming limited due to the rise in antibiotic resistance, which necessitates the development of new therapeutics. Nanotechnology is used to counteract antimicrobial resistance. In this regard, polymeric nanoparticles (NPs) made of natural, biodegradable, biocompatible, and cationic polymers such as Chitosan (CNPs) exhibit wide-spectrum antimicrobial activity. Therefore, this study aimed to prepare CNPs, characterize their physiochemical characteristics: particle size (PZ), polydispersity index (PDI), and zeta potential (ZP), and investigate their antimicrobial activity against Streptococcus pneumoniae TIGR4 (virulent serotype 4) and its capsular mutant (∆cps). Methods: CNPs were prepared at 1, 2.5, and 5 mg/mL concentrations using the ion gelation method. Then, PZ, PDI, and ZP were characterized using a Zetasizer. Transmission electron microscopy (TEM) was used to visualize the CNP’s morphology. Broth and agar dilution methods were used to assess their antimicrobial activity. Cytotoxicity of prepared NPs on A549 cells and their effect on pneumococcal hemolysis were also investigated. Results: Spherical CNPs were produced with PZ ranging from 133.3 nm ± 0.57 to 423 nm ± 12.93 PDI < 0.35, and ZP from 19 ± 0.115 to 27 ± 0.819. The prepared CNPs exhibited antibacterial activity against TIGR4 and its capsule mutant with a minimum inhibitory concentration (MIC90) of 0.5 to 2.5 mg/mL in a non-acidic environment. The hemolysis assay results revealed that CNPs reduced bacterial hemolysis in a concentration-dependent manner. Their mammalian cytotoxicity results indicated that CNPs formed from low concentrations of Chitosan (Cs) were cytocompatible. Conclusion: Nanochitosan particles showed anti-pneumococcal activity regardless of the presence of capsules. They resulted in a concentration-dependent reduction in bacterial hemolysis and were cytocompatible at a lower concentration of Cs. These findings highlight the potential of CNPs in the treatment of pneumococcal diseases.

Effect of chitosan nanoparticles on quorum sensing-controlled virulence factors and expression of LasI and RhlI genes among Pseudomonas aeruginosa clinical isolates

<abstract> <p>Antibiotic-resistant strains of <italic>Pseudomonas aeruginosa (P. aeruginosa</italic>) pose a major threat for healthcare-associated and community-acquired infections. <italic>P. aeruginosa</italic> is recognized as an opportunistic pathogen using quorum sensing (QS) system to regulate the expression of virulence factors and biofilm development. Thus, meddling with the QS system would give alternate methods of controlling the pathogenicity. This study aimed to assess the inhibitory impact of chitosan nanoparticles (CS-NPs) on <italic>P. aeruginosa</italic> virulence factors regulated by QS (e.g., motility and biofilm formation) and <italic>LasI</italic> and <italic>RhlI</italic> gene expression. Minimum inhibitory concentration (MIC) of CS-NPs against 30 isolates of <italic>P. aeruginosa</italic> was determined. The CS-NPs at sub-MIC were utilized to assess their inhibitory effect on motility, biofilm formation, and the expression levels of <italic>LasI</italic> and <italic>RhlI</italic> genes. CS-NPs remarkably inhibited the tested virulence factors as compared to the controls grown without the nanoparticles. The mean (±SD) diameter of swimming motility was decreased from 3.93 (±1.5) to 1.63 (±1.02) cm, and the mean of the swarming motility was reduced from 3.5 (±1.6) to 1.9 (±1.07) cm. All isolates became non-biofilm producers, and the mean percentage rate of biofilm inhibition was 84.95% (±6.18). Quantitative real-time PCR affirmed the opposition of QS activity by lowering the expression levels of <italic>LasI</italic> and <italic>RhlI</italic> genes; the expression level was decreased by 90- and 100-folds, respectively. In conclusion, the application of CS-NPs reduces the virulence factors significantly at both genotypic and phenotypic levels. These promising results can breathe hope in the fight against resistant <italic>P. aeruginosa</italic> by repressing its QS-regulated virulence factors.</p> </abstract>

Evaluating the effect of antibiotics sub-inhibitory dose on Pseudomonas aeruginosa quorum sensing dependent virulence and its phenotypes

The opportunistic Pseudomonas aeruginosa virulence controlled by quorum sensing (QS) also identified as, cell-cell communication. QS system is organized by the LasI-LasR and the RhlI-RhlR components. Provided that QS tends to perform a key role in virulence gene expression and host defence function, QS inhibitors have been proposed as potential antipseudomonal therapies. Sub-inhibitory concentrations (sub-MIC) of antibiotics, although having biostatic effect on bacteria, but can interfere with bacterial QS system and virulence. This research aimed to examine the impact of sub-MIC of azithromycin, imipenem, cefepime and piperacillin/tazobactam on the QS-dependent virulence including pyocyanin and biofilm production, haemolysin, protease and DNase in P. aeruginosa wildtype and mutant strains; transcriptional-regulator (ΔLasR), autoinducer synthesis protein (ΔLasI), transcriptional-regulator (ΔRhlR), protease precursor (ΔLasA) and double regulators mutants (ΔLasR/RhlR). The growth of all strains showed similar pattern, however, in presence of antibiotics significant growth variation was observed among mutant strains when compared to wild type strain. Antimicrobial activity tested by agar diffusion method of all antibiotics on all strains were used to compare the zones of therapeutic and sub-MIC doses showing a significant difference in the inhibition zone. QS-dependant virulence as biofilm, pyocyanin, protease, haemolysin and DNase production showed significant variation on all strains compared to wild type in response to antibiotics used at sub-MIC doses. In conclusion well known antibiotics can be used in sub-MIC doses to decrease the virulence of P. aeruginosa in addition to overcoming the major side effect of the high doses and the occurrence of resistance.

Antibacterial Activity of Chitosan Nanoparticles Against Pathogenic N. gonorrhoea

Purpose

The emergence of Neisseria gonorrhoeae strains that are resistant to the most commonly used antibiotics represents a great concern for global public health. This challenges the effectiveness of clinical treatment regimens and demands the development of alternative antigonococcal agent. In this regard, chitosan nanoparticles (CNPs) are known to have antimicrobial activity against a wide range of pathogens. Thus, they have become a potential candidate for combatting this era of multi-drug resistance. This study aims to formulate CNPs, characterize their physicochemical properties, and examine their antimicrobial activity against gonococcus.

Materials and Methods

The ionic gelation method was used to prepare CNPs of different concentrations. Characterization for their particle size (PZ), polydispersity index (PDI), and zeta potential (ZP) was performed. The anti-microbial activity of CNPs was investigated against 13 WHO N. gonorrhoeae reference strains, using the broth dilution method. Cytotoxicity of CNPs and their effect on bacterial adhesion to HeLa cells were investigated.

Results

The average PZ and ZP of the prepared NPs were increased when the concentration of chitosan was increased from 1 to 5 mg/mL and found to be in the range of 193 nm ± 1.9 to 530 nm ± 13.3, and 14 mV ± 0.5 to 20 mV ± 1, respectively. Transmission electron microscopes (TEM) images revealed spherical NPs, and the NPs had a low PDI value of ≤0.27. The formed CNPs produced antibacterial activity against all tested strains, including those resistant to multiple antibiotics, with a minimum inhibitory concentration (MIC₉₀) of 0.16 to 0.31 mg/mL and a minimum bactericidal concentration (MBC) of 0.31 to 0.61 mg/mL. Of note, at all MIC₉₀ and MBC, the CNPs had no significant cytotoxic effect on HeLa cells and reduced bacterial adhesion to these cells at MBC doses.

Conclusion

The present work findings suggest the potential of the CNPs for the treatment of gonorrhoea.

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.

Cell-free supernatant of Streptococcus salivarius M18 impairs the pathogenic properties of Pseudomonas aeruginosa and Klebsiella pneumonia

M18 strain of Streptococcus salivarius is a bacterial replacement probiotic that has been suggested for use in the oral cavity. Here, we have shown that S. salivarius M18 cell-free supernatant reduced the growth of the two most common human pathogens Pseudomonas aeruginosa and Klebsiella pneumonia and sensitized the pathogenic bacteria to antibiotic. Besides, the supernatant inhibited biofilm formation of P. aeruginosa drastically. For pinpointing the biomolecular changes that occurred in P. aeruginosa incubated with the probiotic supernatant, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy was used. Unsupervised learning algorithms, principal component analysis (PCA) and hierarchical cluster analysis (HCA), and intensity analyses of individual spectral bands exhibited comprehensive alterations in the polysaccharide and lipid contents and compositions of P. aeruginosa cultivated with S. salivarius M18 cell-free supernatant. These results indicate that S. salivarius M18 has the potential for the prevention or alleviation of different pathogen-induced infections along with the infections of oral pathogens.

Chitosan as a Wound Dressing Starting Material: Antimicrobial Properties and Mode of Action

Fighting bacterial resistance is one of the concerns in modern days, as antibiotics remain the main resource of bacterial control. Data shows that for every antibiotic developed, there is a microorganism that becomes resistant to it. Natural polymers, as the source of antibacterial agents, offer a new way to fight bacterial infection. The advantage over conventional synthetic antibiotics is that natural antimicrobial agents are biocompatible, non-toxic, and inexpensive. Chitosan is one of the natural polymers that represent a very promising source for the development of antimicrobial agents. In addition, chitosan is biodegradable, non-toxic, and most importantly, promotes wound healing, features that makes it suitable as a starting material for wound dressings. This paper reviews the antimicrobial properties of chitosan and describes the mechanisms of action toward microbial cells as well as the interactions with mammalian cells in terms of wound healing process. Finally, the applications of chitosan as a wound-dressing material are discussed along with the current status of chitosan-based wound dressings existing on the market.

The Antibacterial Activity and Mechanism of Chlorogenic Acid Against Foodborne Pathogen Pseudomonas aeruginosa

Chlorogenic acid (CA), an ester of caffeic acid, is a major phenolic compound in herbs. The antimicrobial activity of CA against Pseudomonas aeruginosa P1, a foodborne pathogen, was investigated in this study. To understand how CA injured target cells, the influence of CA on cell morphology was assessed. A sunken cell surface and detachment of outer membrane components in P. aeruginosa P1 were observed after being treated by CA. Following this, the intracellular membrane permeability and the content of lipopolysaccharide (LPS), a main component of outer membrane, were determined. The release of intracellular protein and ATP from P. aeruginosa P1 indicated that CA increased intracellular membrane permeability and resulted in the leakage of intracellular materials. The uptake of propidium iodide, a compromised cell membrane nucleic acid stain, further demonstrated that CA acted on the intracellular membrane. CA resulted in the decrease of LPS contents of P. aeruginosa P1, which supported the detachment of outer membrane. CA also downregulated the expression of major genes in LPS biosynthesis, suggesting that CA may inhibit intracellular metabolism of P. aeruginosa P1 cells. Thus, CA increased the intracellular membrane permeability, induced the exfoliation of outer membrane, and disturbed the intracellular metabolism. Damage of intracellular and outer membranes as well as disruption of cell metabolism resulted in cell death eventually. The finding suggested that CA has the potential to be developed as a preservative to control P. aeruginosa-associated foodborne diseases.

Preparation, characterization, and antibacterial activity of diclofenac-loaded chitosan nanoparticles

Emerging antibiotic resistance necessitates the development of new therapeutic approaches. Many studies have reported the antimicrobial activity of diclofenac sodium (DIC) and chitosan nanoparticles (CNPs). Hence, this study aimed to prepare non-antibiotic DIC-loaded CNPs (DIC.CNPs) and characterize their in vitro antibacterial activity. DIC.CNPs were prepared from low and high molecular weight (LMW and HMW, respectively) chitosan using an ionic gelation method. Prepared NPs were characterized, and their antibacterial activity against gram-positive Staphylococcus aureus and Bacillus subtilis was evaluated using the agar diffusion and broth dilution methods. The particle size, polydispersity index (PDI), and encapsulation efficiency of the formulated DIC.CNPs increased with increasing MW of chitosan. The prepared NPs showed a narrow size distribution with low PDI values (0.18 and 0.24) and encapsulation efficiency (29.3% and 31.1%) for LMW.DIC.CNPs and HMW.DIC.CNPs, respectively. The in vitro release profile of DIC from the DIC.CNPs was biphasic with a burst release followed by slow release and was influenced by the MW of chitosan. DIC.CNPs exhibited significantly higher antibacterial activity against S. aureus (minimum inhibitory concentration [MIC90] LMW.DIC.CNPs = 35 µg/mL and MIC90 HMW.DIC.CNPs = 18 µg/mL) and B. subtilis (MIC90 LMW.DIC.CNPs = 17.5 µg/mL and MIC90 HMW.DIC.CNPs = 9 µg/mL) than DIC alone did (MIC90 DIC = 250 and 50 µg/mL against S. aureus and B. subtilis, respectively). The antibacterial activity was influenced by pH and the MW of chitosan. Collectively, these results may suggest the potential usefulness of DIC.CNPs as non-antibiotic antibacterial agent necessitating further future studies to asses the stability of DIC.CNPs prepared.