The Expanded Role of Chitosan in Localized Antimicrobial Therapy

Chitosan is one of the most studied natural origin polymers for biomedical applications. This review focuses on the potential of chitosan in localized antimicrobial therapy to address the challenges of current rising antimicrobial resistance. Due to its mucoadhesiveness, chitosan offers the opportunity to prolong the formulation residence time at mucosal sites; its wound healing properties open possibilities to utilize chitosan as wound dressings with multitargeted activities and more. We provide an unbiased overview of the state-of-the-art chitosan-based delivery systems categorized by the administration site, addressing the site-related challenges and evaluating the representative formulations. Specifically, we offer an in-depth analysis of the current challenges of the chitosan-based novel delivery systems for skin and vaginal infections, including its formulations optimizations and limitations. A brief overview of chitosan’s potential in treating ocular, buccal and dental, and nasal infections is included. We close the review with remarks on toxicity issues and remaining challenges and perspectives

Liposomes-in-chitosan hydrogel boosts potential of chlorhexidine in biofilm eradication in vitro

Successful treatment of skin infections requires eradication of biofilms found in up to 90 % of all chronic wounds, causing delayed healing and increased morbidity. We hypothesized that chitosan hydrogel boosts the activity of liposomally-associated membrane active antimicrobials (MAA) and could potentially improve bacterial and biofilm eradication. Therefore, liposomes (∼300 nm) bearing chlorhexidine (CHX; ∼50 μg/mg lipid) as a model MAA were incorporated into chitosan hydrogel. The novel CHX-liposomes-in-hydrogel formulation was optimized for skin therapy. It significantly inhibited the production of nitric oxide (NO) in lipopolysaccharide (LPS)-induced macrophage and almost completely reduced biofilm formation. Moreover, it reduced Staphylococcus aureus and Pseudomonas aeruginosa adherent bacterial cells in biofilm by 64.2–98.1 %. Chitosan hydrogel boosted the anti-inflammatory and antimicrobial properties of CHX

Chitosan-based delivery system enhances antimicrobial activity of chlorhexidine

Infected chronic skin wounds and other skin infections are increasingly putting pressure on the health care providers and patients. The pressure is especially concerning due to the rise of antimicrobial resistance and biofilm-producing bacteria that further impair treatment success. Therefore, innovative strategies for wound healing and bacterial eradication are urgently needed; utilization of materials with inherent biological properties could offer a potential solution. Chitosan is one of the most frequently used polymers in delivery systems. This bioactive polymer is often regarded as an attractive constituent in delivery systems due to its inherent antimicrobial, anti-inflammatory, anti-oxidative, and wound healing properties. However, lipid-based vesicles and liposomes are generally considered more suitable as delivery systems for skin due to their ability to interact with the skin structure and provide prolonged release, protect the antimicrobial compound, and allow high local concentrations at the infected site. To take advantage of the beneficial attributes of the lipid-based vesicles and chitosan, these components can be combined into chitosan-containing liposomes or chitosomes and chitosan-coated liposomes. These systems have previously been investigated for use in wound therapy; however, their potential in infected wounds is not fully investigated. In this study, we aimed to investigate whether both the chitosan-containing and chitosan-coated liposomes tailored for infected wounds could improve the antimicrobial activity of the membrane-active antimicrobial chlorhexidine, while assuring both the anti-inflammatory activity and cell compatibility. Chlorhexidine was incorporated into three different vesicles, namely plain (chitosan-free), chitosan-containing and chitosan-coated liposomes that were optimized for skin wounds. Their release profile, antimicrobial activities, anti-inflammatory properties, and cell compatibility were assessed in vitro. The vesicles comprising chitosan demonstrated slower release rate of chlorhexidine and high cell compatibility. Additionally, the inflammatory responses in murine macrophages treated with these vesicles were reduced by about 60% compared to non-treated cells. Finally, liposomes containing both chitosan and chlorhexidine demonstrated the strongest antibacterial effect against Staphylococcus aureus. Both chitosan-containing and chitosan-coated liposomes comprising chlorhexidine could serve as excellent platforms for the delivery of membrane-active antimicrobials to infected wounds as confirmed by improved antimicrobial performance of chlorhexidine

Tailored anti-biofilm activity – Liposomal delivery for mimic of small antimicrobial peptide

The eradication of bacteria embedded in biofilms is among the most challenging obstacles in the management of chronic wounds. These biofilms are found in most chronic wounds; moreover, the biofilm-embedded bacteria are considerably less susceptible to conventional antimicrobial treatment than the planktonic bacteria. Antimicrobial peptides and their mimics are considered attractive candidates in the pursuit of novel therapeutic options for the treatment of chronic wounds and general bacterial eradication. However, some limitations linked to these membrane-active antimicrobials are making their clinical use challenging. Novel innovative delivery systems addressing these limitations represent a smart solution. We hypothesized that incorporation of a novel synthetic mimic of an antimicrobial peptide in liposomes could improve its anti-biofilm effect as well as the anti-inflammatory activity. The small synthetic mimic of an antimicrobial peptide, 7e-SMAMP, was incorporated into liposomes (~280 nm) tailored for skin wounds and evaluated for its potential activity against both biofilm formation and eradication of pre-formed biofilms. The 7e-SMAMP-liposomes significantly lowered inflammatory response in murine macrophages (~30 % reduction) without affecting the viability of macrophages or keratinocytes. Importantly, the 7e-SMAMP-liposomes completely eradicated biofilms produced by Staphylococcus aureus and Escherichia coli above concentrations of 6.25 μg/mL, whereas in Pseudomonas aeruginosa the eradication reached 75 % at the same concentration. Incorporation of 7e-SMAMP in liposomes improved both the inhibition of biofilm formation as well as biofilm eradication in vitro, as compared to non-formulated antimicrobial, therefore confirming its potential as a novel therapeutic option for bacteria-infected chronic wounds

Advanced topical delivery systems for membrane-active antimicrobials. Exploring nature to improve antimicrobial wound therapy

Currently, approximately 2% of the general population will experience at least one chronic wound throughout their lifetime. The numbers are expected to rise due to an aging population with a heightened disease burden. These wounds are major burdens for the patients; therefore, we need to find innovative approaches for bacterial eradication and improved wound treatment. We aimed to utilize nature’s toolbox to improve the effect of novel antimicrobial compounds, such as synthetic mimics of antimicrobial peptides (SMAMPs) and other membrane-active antimicrobials (MMAs), using pharmaceutical technology. In this project, we developed delivery systems based on liposomes and chitosan to improve anti-inflammatory, antimicrobial, anti-biofilm, and wound healing properties of novel SMAMPs. From the initial studies with the model compound chlorhexidine (CHX), liposomes-in-chitosan hydrogel was deemed the most suitable systems, and therefore selected for further development of delivery systems for two novel SMAMPs, namely 7e-SMAMP and 7a-SMAMP. From these studies, we confirmed that the 7e-SMAMP-liposomes and 7a-SMAMP incorporated in liposomes-in-chitosan hydrogel exhibited anti-inflammatory properties and a high level of biocompatibility. Furthermore, the anti-biofilm activities against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa of 7e-SMAMP improved upon its incorporation in liposomes and cell migration could be improved by incorporation of 7a-SMAMP in liposomes. Overall, the MAA-comprising liposomes-in-hydrogel systems proved to be suitable formulations with good biocompatibility and enhanced anti-inflammatory, antimicrobial, anti-biofilm, and wound healing properties. The novel delivery system comprising SMAMPs bears great potential as a platform in the therapeutic management of infected chronic skin wounds

Advanced topical delivery systems for membrane-active antimicrobials. Exploring nature to improve antimicrobial wound therapy

Currently, approximately 2% of the general population will experience at least one chronic wound throughout their lifetime. The numbers are expected to rise due to an aging population with a heightened disease burden. These wounds are major burdens for the patients; therefore, we need to find innovative approaches for bacterial eradication and improved wound treatment. We aimed to utilize nature’s toolbox to improve the effect of novel antimicrobial compounds, such as synthetic mimics of antimicrobial peptides (SMAMPs) and other membrane-active antimicrobials (MMAs), using pharmaceutical technology. In this project, we developed delivery systems based on liposomes and chitosan to improve anti-inflammatory, antimicrobial, anti-biofilm, and wound healing properties of novel SMAMPs. From the initial studies with the model compound chlorhexidine (CHX), liposomes-in-chitosan hydrogel was deemed the most suitable systems, and therefore selected for further development of delivery systems for two novel SMAMPs, namely 7e-SMAMP and 7a-SMAMP. From these studies, we confirmed that the 7e-SMAMP-liposomes and 7a-SMAMP incorporated in liposomes-in-chitosan hydrogel exhibited anti-inflammatory properties and a high level of biocompatibility. Furthermore, the anti-biofilm activities against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa of 7e-SMAMP improved upon its incorporation in liposomes and cell migration could be improved by incorporation of 7a-SMAMP in liposomes. Overall, the MAA-comprising liposomes-in-hydrogel systems proved to be suitable formulations with good biocompatibility and enhanced anti-inflammatory, antimicrobial, anti-biofilm, and wound healing properties. The novel delivery system comprising SMAMPs bears great potential as a platform in the therapeutic management of infected chronic skin wounds.I dag vil om lag 2% av den generelle befolkningen få ett eller flere kroniske sår i løpet av livet, men på grunn av en aldrende befolkning med økt sykdomsbyrde forventes det at antallet vil øke. Disse sårene medfører ofte store belastninger for pasienter som understreker viktigheten av at vi finner nyskapende strategier for forbedret sårheling og bekjempelse av bakterier i infiserte kroniske hudsår. Vi ønsker å nyttiggjøre oss av naturens egen verktøykasse i kombinasjon med farmasøytisk teknologi for å forbedre effekten av nye antimikrobielle forbindelser, spesielt syntetiske etterligninger av antimikrobielle peptider (SMAMPer) og andre membranaktive forbindelser (MAAer). I dette prosjektet hadde vi som mål å utvikle farmasøytiske leveringssystemer basert på liposomer og kitosan for å forbedre de antiinflammatoriske, antimikrobielle, biofilmhemmende og sårhelende egenskapene til nyutviklede SMAMPer. Etter studier med modellsubstansen klorhexidin (CHX), ble liposomer-i-kitosanhydrogel ansett for å være det mest passende systemet og dermed valgt for den videre utviklingen av leveringssystemer for to nye SMAMPer, nemlig 7e-SMAMP og 7a-SMAMP. Fra resultatene av disse studiene fant vi at 7e-SMAMP-liposomer og 7a-SMAMP inkorporert i liposomer-i-kitosanhydrogel utviste lovende antiinflammatoriske egenskaper og høy grad av cellekompatibilitet. Videre fant vi også ut at de biofilmhemmende egenskapene mot Staphylococcus aureus, Escherichia coli og Pseudomonas aeruginosa økte når 7e-SMAMP ble inkorporert i liposomer. I tillegg så vi at vi kunne oppnå forbedret cellemigrasjon når cellene ble behandlet med 7a-SMAMP inkorporert i liposomer. Samlet gjennom prosjektet konkluderte vi med at liposomer-i-kitosanhydrogel med MAAer er en velegnet formulering med god biokompatibilitet og forbedrede antiinflammatoriske, antimikrobielle, biofilmhemmende og sårhelende egenskaper. Det nye leveringssystemet for SMAMPer har derfor et stort fremtidig potensial i videre utvikling for bedre behandling av infiserte kroniske hudsår

Chitosomes-In-Chitosan Hydrogel for Acute Skin Injuries: Prevention and Infection Control

Burns and other skin injuries are growing concerns as well as challenges in an era of antimicrobial resistance. Novel treatment options to improve the prevention and eradication of infectious skin biofilm-producing pathogens, while enhancing wound healing, are urgently needed for the timely treatment of infection-prone injuries. Treatment of acute skin injuries requires tailoring of formulation to assure both proper skin retention and the appropriate release of incorporated antimicrobials. The challenge remains to formulate antimicrobials with low water solubility, which often requires carriers as the primary vehicle, followed by a secondary skin-friendly vehicle. We focused on widely used chlorhexidine formulated in the chitosan-infused nanocarriers, chitosomes, incorporated into chitosan hydrogel for improved treatment of skin injuries. To prove our hypothesis, lipid nanocarriers and chitosan-comprising nanocarriers (≈250 nm) with membrane-active antimicrobial chlorhexidine were optimized and incorporated into chitosan hydrogel. The biological and antibacterial effects of both vesicles and a vesicles-in-hydrogel system were evaluated. The chitosomes-in-chitosan hydrogel formulation demonstrated promising physical properties and were proven safe. Additionally, the chitosan-based systems, both chitosomes and chitosan hydrogel, showed an improved antimicrobial effect against S. aureus and S. epidermidis compared to the formulations without chitosan. The novel formulation could serve as a foundation for infection prevention and bacterial eradication in acute wounds

Lecithin and Chitosan as Building Blocks in Anti-<i>Candida</i> Clotrimazole Nanoparticles

The main focus when considering treatment of non-healing and infected wounds is tied to the microbial, particularly bacterial, burden within the wound bed. However, as fungal contributions in these microbial communities become more recognized, the focus needs to be broadened, and the remaining participants in the complex wound microbiome need to be addressed in the development of new treatment strategies. In this study, lecithin/chitosan nanoparticles loaded with clotrimazole were tailored to eradicate one of the most abundant fungi in the wound environment, namely C. albicans. Moreover, this investigation was extended to the building blocks and their organization within the delivery system. In the evaluation of the novel nanoparticles, their compatibility with keratinocytes was confirmed. Furthermore, these biocompatible, biodegradable, and non-toxic carriers comprising clotrimazole (~189 nm, 24 mV) were evaluated for their antifungal activity through both disk diffusion and microdilution methods. It was found that the activity of clotrimazole was fully preserved upon its incorporation into this smart delivery system. These results indicate both that the novel carriers for clotrimazole could serve as a therapeutic alternative in the treatment of fungi-infected wounds and that the building blocks and their organization affect the performance of nanoparticles