Carboxymethyl chitosan prevents formation of broad-spectrum biofilm

Advances of biomacromolecule-based antibacterial hydrogels and their performance evaluation for wound healing: A review

Biomacromolecule hydrogels possess excellent mechanical properties and biocompatibility, but their inability to combat bacteria restricts their application in the biomedical field. With the increasing requirements and demands for hydrogel dressings, wound dressings with antibacterial properties of biomacromolecule hydrogels reinforced by adding antibacterial agents have attracted much attention, and related reviews are emerging. In this paper, the advances of biomacromolecule antibacterial hydrogels (including chitosan, sodium alginate, Hyaluronic acid, cellulose and gelatin) were first overviewed, and the antibacterial agents incorporated into hydrogels were classified (including metals and their derivatives, carbon-based materials, and native compounds). A series of performance evaluations of antibacterial hydrogels in the process of promoting wound healing were then reviewed, including basic properties (mechanical, rheological, injectable and self-healing, etc.), in vitro experiments (hemostasis, antibacterial, anti-inflammatory, anti-oxidation, biocompatibility) and in vivo experiments (in vivo model, histomorphology analysis, cytokines). Finally, the future development of biomacromolecule-based antibacterial hydrogels for wound healing is prospected. This work can provide a useful reference for researchers to prepare practical new wound hydrogel dressings.

Co-Delivery of Naringin and Ciprofloxacin by Oleic Acid Lipid Core Encapsulated in Carboxymethyl Chitosan/Alginate Nanoparticle Composite for Enhanced Antimicrobial Activity

A novel combination of antibiotic, ciprofloxacin (CIP) with herbal counterpart naringin (NAR) was encapsulated by an oleic acid lipid core and carboxymethyl chitosan (CM-CS)/Alginate (AG) nanoparticle composite (CIP + NAR-CM-CS/AG-NPs) for improved antimicrobial efficacy of antibiotic. Herein, this study explored the design and preparation of a composite system that enables to deliver both CIP and NAR from the oleic acid lipid core of CM-CS/AG nanoparticles using a nonsolvent ionic gelation technique. The nanoparticles (NPs) were fabricated with improved long-acting antimicrobial activity against E. coli and S. aureus. The optimized composition was investigated for physicochemical properties particle size, particle distribution, and ζ-potential. A diverse array of analytical tools was employed to characterize the optimized formulation including DSC, XRD, Malvern Zetasizer for particle size, ζ-potential, TEM, and SEM. Further, the preparation was investigated for % drug release, flux determination, antioxidant, and antimicrobial activity. The formulation stability was tested for 90 days and also evaluated formulation stability in fetal bovine serum to inspect the modification in physicochemical characteristics. NPs size was determined at 85 nm, PDI, and ζ-potential was recorded at 0.318, and 0.7 ± 0.4 mV. The % CIP and NAR entrapment efficiency and % loading were incurred as 91 ± 1.9, and 89.5 ± 1.2; 11.5 ± 0.6, and 10.8 ± 0.5%, respectively. The drug release erupted in the beginning phase followed by sustained and prolonged release for 48 h. The analytical experiments by DSC ensured the noninteracting and safe use of excipients in combination. X-ray studies demonstrated the amorphous state of the drug in the formulation. The insignificant alteration of formulation characteristics in FBS suggested stable and robust preparation. Storage stability of the developed formulation ensured consistent and uniform stability for three months. The DPPH assays demonstrated that NAR had good antioxidant capacity and supported improving antimicrobial activity of CIP. The hemolytic test suggested the developed formulation was compatible and caused insignificant RBC destruction. The in-house built formulation CIP + NAR-CM-CS/AG-NPs significantly improved the antimicrobial activity compared to CIP alone, offering a novel choice in antimicrobial application.

Synthesis and Antibiotic Activity of Chitosan-Based Comb-like Co-Polypeptides

Infections caused by multidrug-resistant Gram-negative bacteria have been named one of the most urgent global health threats due to antimicrobial resistance. Considerable efforts have been made to develop new antibiotic drugs and investigate the mechanism of resistance. Recently, Anti-Microbial Peptides (AMPs) have served as a paradigm in the design of novel drugs that are active against multidrug-resistant organisms. AMPs are rapid-acting, potent, possess an unusually broad spectrum of activity, and have shown efficacy as topical agents. Unlike traditional therapeutics that interfere with essential bacterial enzymes, AMPs interact with microbial membranes through electrostatic interactions and physically damage cell integrity. However, naturally occurring AMPs have limited selectivity and modest efficacy. Therefore, recent efforts have focused on the development of synthetic AMP analogs with optimal pharmacodynamics and an ideal selectivity profile. Hence, this work explores the development of novel antimicrobial agents which mimic the structure of graft copolymers and mirror the mode of action of AMPs. A family of polymers comprised of chitosan backbone and AMP side chains were synthesized via the ring-opening polymerization of the N-carboxyanhydride of l-lysine and l-leucine. The polymerization was initiated from the functional groups of chitosan. The derivatives with random- and block-copolymer side chains were explored as drug targets. These graft copolymer systems exhibited activity against clinically significant pathogens and disrupted biofilm formation. Our studies highlight the potential of chitosan-graft-polypeptide structures in biomedical applications.

Biocompatible carboxymethyl chitosan-modified glass ionomer cement with enhanced mechanical and anti-bacterial properties

Due to the potential adverse effects of conventional dental cements, the demand for biocompatible cements have grown tremendously in the field of dentistry. In this respect, Glass ionomer cements (GICs) are being developed by different researchers. However, low mechanical strength of GIC make them unsuitable for application in high-stress areas. Thus, numerous initiatives to improve mechanical performance have been attempted till date including incorporation of reinforcing fillers. Novelty of the study lies in using carboxymethyl chitosan (CMC) to develop a biocompatible dental cement (DC/CMC-m-GP), which would have enhanced mechanical strength due to greater interaction of CMC with the particles of GIC and better cyto-compatibility due to its cell-proliferation activity. The mechanical strength, acid erosion and fluoride release of DC/CMC-m-GP were studied and compared with control dental cement (DC/Control). DC/CMC-m-GP shows compressive strength of 157.45 M Pa and flexural strength of 18.76 M Pa which was higher as compared to DC/Control. The morphology of the GICs were studied through FESEM. Anti-microbial activity of DC/CMC-m-GP was studied by Agar disc-diffusion method and biofilm assay against S. mutans, which shows that DC/CMC-m-GP inhibits bacterial adhesion on its surface. MTT assay infers that DC/CMC-m-GP was non-cytotoxic and did not affect the cell viability significantly.

Addition time plays a major role in the inhibitory effect of chitosan on the production of Pseudomonas aeruginosa virulence factors

Pseudomonas aeruginosa is a gram-negative bacterium capable of forming persistent biofilms that are extremely difficult to eradicate. The species is most infamously known due to complications in cystic fibrosis patients. The high mortality of cystic fibrosis is caused by P. aeruginosa biofilms occurring in pathologically overly mucous lungs, which are the major cause facilitating the organ failure. Due to Pseudomonas biofilm-associated infections, remarkably high doses of antibiotics must be administered, eventually contributing to the development of antibiotic resistance. Nowadays, multidrug resistant P. aeruginosa is one of the most terrible threats in medicine, and the search for novel antimicrobial drugs is of the utmost importance. We have studied the effect of low molecular weight chitosan (LMWCH) on various stages of P. aeruginosa ATCC 10145 biofilm formation and eradication, as well as on production of other virulence factors. LMWCH is a well-known naturally occurring agent with a vast antimicrobial spectrum, which has already found application in various fields of medicine and industry. LMWCH at a concentration of 40 mg/L was able to completely prevent biofilm formation. At a concentration of 60 mg/L, this agent was capable to eradicate already formed biofilm in most studied times of addition (2-12 h of cultivation). LMWCH (50 mg/L) was also able to suppress pyocyanin production when added 2 and 4 h after cultivation. The treatment resulted in reduced formation of cell clusters. LMWCH was proved to be an effective antibiofilm agent worth further clinical research with the potential to become a novel drug for the treatment of P. aeruginosa infections.

Latest Trends in Surface Modification for Dental Implantology: Innovative Developments and Analytical Applications

An increase in the world population and its life expectancy, as well as the ongoing concern about our physical appearance, have elevated the relevance of dental implantology in recent decades. Engineering strategies to improve the survival rate of dental implants have been widely investigated, focusing on implant material composition, geometry (usually guided to reduce stiffness), and interface surrounding tissues. Although efforts to develop different implant surface modifications are being applied in commercial dental prostheses today, the inclusion of surface coatings has gained special interest, as they can be tailored to efficiently enhance osseointegration, as well as to reduce bacterial-related infection, minimizing peri-implantitis appearance and its associated risks. The use of biomaterials to replace teeth has highlighted the need for the development of reliable analytical methods to assess the therapeutic benefits of implants. This literature review considers the state-of-the-art strategies for surface modification or coating and analytical methodologies for increasing the survival rate for teeth restoration.

Antimicrobial peptides - Unleashing their therapeutic potential using nanotechnology

Antimicrobial peptides (AMPs) are potent, mostly cationic, and amphiphilic broad-spectrum host defense antimicrobials that are produced by all organisms ranging from prokaryotes to humans. In addition to their antimicrobial actions, they modulate inflammatory and immune responses and promote wound healing. Although they have clear benefits over traditional antibiotic drugs, their wide therapeutic utilization is compromised by concerns of toxicity, stability, and production costs. Recent advances in nanotechnology have attracted increasing interest to unleash the AMPs' immense potential as broad-spectrum antibiotics and anti-biofilm agents, against which the bacteria have less chances to develop resistance. Topical application of AMPs promotes migration of keratinocytes and fibroblasts, and contributes significantly to an accelerated wound healing process. Delivery of AMPs by employing nanotechnological approaches avoids the major disadvantages of AMPs, such as instability and toxicity, and provides a controlled delivery profile together with prolonged activity. In this review, we provide an overview of the key properties of AMPs and discuss the latest developments in topical AMP therapy using nanocarriers. We use chronic hard-to-heal wounds-complicated by infections, inflammation, and stagnated healing-as an example of an unmet medical need for which the AMPs' wide range of therapeutic actions could provide the most potential benefit. The use of innovative materials and sophisticated nanotechnological approaches offering various possibilities are discussed in more depth.

Physicochemical and Antimicrobial Properties of Thermosensitive Chitosan Hydrogel Loaded with Fosfomycin

Thermosensitive chitosan hydrogels-renewable, biocompatible materials-have many applications as injectable biomaterials for localized drug delivery in the treatment of a variety of diseases. To combat infections such as Staphylococcus aureus osteomyelitis, localized antibiotic delivery would allow for higher doses at the site of infection without the risks associated with traditional antibiotic regimens. Fosfomycin, a small antibiotic in its own class, was loaded into a chitosan hydrogel system with varied beta-glycerol phosphate (β-GP) and fosfomycin (FOS) concentrations. The purpose of this study was to elucidate the interactions between FOS and chitosan hydrogel. The Kirby Bauer assay revealed an unexpected concentration-dependent inhibition of S. aureus, with reduced efficacy at the high FOS concentration but only at the low β-GP concentration. No effect of FOS concentration was observed for the planktonic assay. Rheological testing revealed that increasing β-GP concentration increased the storage modulus while decreasing gelation temperature. NMR showed that FOS was removed from the liquid portion of the hydrogel by reaction over 12 h. SEM and FTIR confirmed gels degraded and released organophosphates over 5 days. This work provides insight into the physicochemical interactions between fosfomycin and chitosan hydrogel systems and informs selection of biomaterial components for improving infection treatment.

Incorporation of Bioglass Improved the Mechanical Stability and Bioactivity of Alginate/Carboxymethyl Chitosan Hydrogel Wound Dressing

Recently, hydrogel wound dressings were popular in wound healing because of their advantages over traditional gauze dressings. The alginate/carboxymethyl chitosan (SA/CMCS) hydrogel wound dressing has been widely studied because of its biocompatibility and antibacterial ability. However, the poor mechanical stability and lack of bioactivity limit their applications. Bioglass (BG) has been well acknowledged as a bioactive material, and SA/BG hydrogels have been reported to be able to promote wound healing. Calcium ions released from BG can further cross-link SA, which may enhance the mechanical stability of the SA/CMCS hydrogels. Therefore, in this study, BG was incorporated into SA/CMCS hydrogel in order to obtain a bioactive alginate/CMCS/BG (SA/CMCS/BG) hydrogel wound dressing with improved mechanical stability. Results showed that the Young's modulus of SA/CMCS/BG hydrogel was three times higher than that of SA/CMCS hydrogel. In addition to better antibacterial and coagulation properties, SA/CMCS/BG hydrogels possess stronger bioactivity than SA/CMCS hydrogels as they could accelerate skin wound closure by regulating the host inflammation responses, stimulating angiogenesis, and enhancing collagen deposition in wound sites, which suggests that SA/CMCS/BG hydrogels are good candidates for clinic wound dressings.

Chinese White Wax Solid Lipid Nanoparticles as a Novel Nanocarrier of Curcumin for Inhibiting the Formation of Staphylococcus aureus Biofilms

Chinese white wax solid lipid nanoparticles (cwSLNs) were prepared by high shear homogenization and ultrasound methods. Using an optimized formula, spherical cwSLNs with an average particle size of 401.9 ± 21.3 nm were obtained. The cwSLNs showed high entrapment efficiency, approximately 84.6%, for loading curcumin. The curcumin loaded cwSLNs (Cur-cwSLNs) exhibited sustained drug release properties. Notably, Cur-cwSLNs had a higher drug release rate at pH 4.5 than at pH 7.4, which suggested their applicability in an acidic environment. Cur-cwSLNs were able to inhibit the growth of Staphylococcus aureus and were more effective at reducing the biofilms produced by this bacterium compared to free curcumin. This study confirmed that cwSLNs may be novel carriers for increasing the bioavailability of curcumin with the potential to inhibit the formation of S. aureus biofilms.

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.

In vitro antibacterial and early stage biofilm inhibitory potential of an edible chitosan and its phenolic conjugates against Pseudomonas aeruginosa and Listeria monocytogenes

In the present study, the antibacterial potential of chitosan grafted with phenolics (CPCs) such as caffeic acid (CCA), ferulic (CFA), and sinapic acid (CSA) were evaluated against foodborne pathogens like Pseudomonas aeruginosa (PA) and Listeria monocytogenes (LM). The geometric means of minimum inhibitory concentration (MIC range 0.05-0.33 mg/ml), bactericidal concentration (MBC range 0.30-0.45 mg/ml), biofilm inhibitory concentration (BIC range 0.42-0.83 mg/ml), and biofilm eradication concentration (BEC range 1.71-3.70 mg/ml) of CPCs were found to be lower than the MIC (0.12-1.08 mg/ml), MBC (0.17-1.84 mg/ml), BIC (4.0-4.50 mg/ml), and BEC (17.4-23.0 mg/ml) of unmodified chitosan against PA and LM. CPCs attenuated the biofilms of PA and LM by increasing the membrane permeability of bacteria embedded within the biofilms. Further, sub MIC of CPCs (0.5 × MIC) significantly reduced the biofilm adhesion (p < 0.001) by representative strains of LM (CCA: 72.2 ± 3.5, CFA: 79.3 ± 0.9, and CSA: 74.9 ± 1.5%) and PA (CCA: 64 ± 1.1, CFA: 67.8 ± 0.8, and CSA: 65.7 ± 4.9%). These results suggested the antibacterial and anti-biofilm potential of CPCs that can be exploited to control foodborne pathogenic infections.

Conjugation of Inulin Improves Anti-Biofilm Activity of Chitosan

Bacteria biofilm helps bacteria prevent phagocytosis during infection and increase resistance to antibiotics. Staphylococcus aureus is a Gram-positive pathogenic bacterium and is tightly associated with biofilm-related infections, which have led to great threat to human health. Chitosan, the only cationic polysaccharide in nature, has been demonstrated to have antimicrobial and anti-biofilm activities, which, however, require a relative high dosage of chitosan. Moreover, poor water solubility further restricts its applications on anti-infection therapy. Inulins are a group of polysaccharides produced by many types of plants, and are widely used in processed foods. Compared to chitosan, inulin is very soluble in water and possesses a mild antibacterial activity against certain pathogenic bacteria. In order to develop an effective strategy to treat biofilm-related infections, we introduce a method by covalent conjugation of inulin to chitosan. The physicochemical characterization of the inulin–chitosan conjugate was assayed, and the anti-biofilm activity was evaluated against S. aureus biofilm. The results indicated that, as compared to chitosan, this novel polysaccharide–polysaccharide conjugate significantly enhanced activities against S. aureus either in a biofilm or planktonic state. Of note, the conjugate also showed a broad spectrum anti-biofilm activity on different bacteria strains and low cellular toxicity to mammalian cells. These results suggested that chitosan conjugation of inulin was a viable strategy for treatment against biofilm-related infections. This finding may further spread the application of natural polysaccharides on treatments of infectious disease.

Preparation and characterization of gelatin/sericin/carboxymethyl chitosan medical tissue glue

Background:

The development and application of medical glue has been continuously expanding and advancing. However, there are few glues that combine low-cost with excellent biocompatibility.

Methods:

We have prepared a medical tissue glue using a gelatin (Gel), sericin (SS) and carboxymethyl chitosan (CMCS) blend solution, cross-linked with 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC). The combination’s characteristics and microstructure morphology were observed by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM). Bond strength tests were used to measure the bond strength of the glue. To assay blood compatibility, a hemolytic test, dynamic coagulation test and platelet adherence test were also investigated. Further, the cellular behavior of L-929 and a systemic acute toxicity test on the Gel/SS/CMCS tissue glue were also investigated by MTT and H&E staining.

Results:

Characterization analysis showed that there was stable binding between raw materials, forming an amide bond with homogeneous holes. The bond strength of the tissue glue reached 2.50 ± 0.04 N in 10 minutes, slightly higher than the alpha-cyanoacrylate biological glue (2.25 ± 0.05 N). Blood compatibility tests revealed that the glue had outstanding blood compatibility. Further, cytotoxicity test and systemic acute toxicity test both showed that the glue was without cytotoxicity and not toxic to the body.

Conclusions:

The Gel/SS/CMCS tissue glue we prepared at low cost had excellent biocompatibility and structural characteristics. It could be a better candidate for tissue engineering in biomedical applications applied in clinical practice to promote skin wound healing and to further reduce the formation of skin wound scars.

Efficacy of carboxymethyl chitosan against Candida tropicalis and Staphylococcus epidermidis monomicrobial and polymicrobial biofilms

Polymicrobial biofilms with fungi and bacteria are the leading cause for the failure of medical devices and related infections. In this study, antibiofilm activities of carboxymethyl chitosan (CM-chitosan) on monomicrobial and polymicrobial biofilms of Staphylococcus epidermidis and Candida tropicalis in vitro were evaluated. CM-chitosan was effective as a sole agent, inhibiting both monomicrobial and polymicrobial biofilms in microplates and also on the silicone surface in short- and long-term periods. Biofilm architecture was investigated by scanning electron microscopy and confocal laser scanning microscopy was used to examine living/dead organisms within biofilm. CM-chitosan inhibited planktonic growth as well as adhesion. Further biofilm formation was inhibited by CM-chitosan added at 90min or 12h after biofilm initiation. CM-chitosan may serve as a possible antibiofilm agent to limit monomicrobial and polymicrobial biofilm.

Inhibition of bacterial biofilms by carboxymethyl chitosan combined with silver, zinc and copper salts

Investigation of the antimicrobial action of carboxymethyl chitosan (CMCh) is among the alternative approaches in the control of pathogenic microorganisms. This study aimed to screen the toxicity using the brine shrimp lethality assay and to investigate the inhibitory activity of carboxymethyl in isolation or in combination with silver nitrate, copper sulfate and zinc sulfate on biofilm formation by Staphylococcus aureus ATCC 6538, Staphylococcus epidermidis ATCC 12228, Kocuria rhizophila ATCC 9341, Pseudomonas aeruginosa ATCC 9027, Escherichia coli ATCC 25312, and Burkholderia cepacia ATCC 17759. The CMCh was obtained by reacting chitosan with monochloroacetic acid under alkaline conditions, and the occurrence of carboxymethylation was evidenced by FTIR and ¹H NMR spectroscopy. The CMCh was combined with metallic salts (AgNO₃, CuSO₄·5H₂O and ZnSO₄) to perform the bioassays to screen the toxicity, to determine the minimum inhibitory concentration and the impact of sub-inhibitory concentrations against biofilm formation. Although CMCh did not show inhibitory activity against bacterial growth, it had an interesting level of inhibition of bacterial biofilm. The results suggest that sub-inhibitory concentrations of compounds were effective against biofilm formation.

Antifouling and antimicrobial biomaterials: an overview

The use of implantable medical devices is a common and indispensable part of medical care for both diagnostic and therapeutic purposes. However, as side effect, the implant of medical devices quite often leads to the occurrence of difficult-to-treat infections, as a consequence of the colonization of their abiotic surfaces by biofilm-growing microorganisms increasingly resistant to antimicrobial therapies. A promising strategy to combat device-related infections is based on anti-infective biomaterials that either repel microbes, so they cannot attach to the device surfaces, or kill them in the surrounding areas. In general, such biomaterials are characterized by antifouling coatings, exhibiting low adhesion or even repellent properties towards microorganisms, or antimicrobial coatings, able to kill microbes approaching the surface. In this light, the present overview will address the development in the last two decades of antifouling and antimicrobial biomaterials designed to potentially limit the initial stages of microbial adhesion, as well as the microbial growth and biofilm formation on medical device surfaces.

Inhibition of mixed fungal and bacterial biofilms on silicone by carboxymethyl chitosan

Mixed biofilms with fungi and bacteria are the leading cause for the failure of medical silicone devices, such as voice prostheses in laryngectomy. In this study, we determined the effect of carboxymethyl chitosan (CM-chitosan) on mixed biofilm formation of fungi and bacteria on silicone which is widely used for construction of medical devices. Mixed biofilm formations were inhibited 72.87% by CM-chitosan. Furthermore, CM-chitosan significantly decreased the metabolic activity of the biofilms using 2, 3-bis (2-methoxy-4-nitro-5-sulfo-phenyl)-2H-tetrazolium-5 carboxanilide (XTT) reduction assay. The examination using confocal laser scanning microscopy and scanning electron microscope confirmed that CM-chitosan inhibited the mixed biofilm and damaged the cells. Effects of CM-chitosan on different stages of biofilms were also evaluated. CM-chitosan inhibited the adhesion of fungi and bacteria with an efficiency of >90%. It prevented biofilm formation at efficiencies of 69.86%, 50.88% and 46.58% when CM-chitosan was added at 90min, 12h and 24h after biofilm initiation, respectively. Moreover, CM-chitosan inhibited Candida yeast-to-hyphal transition. CM-chitosan was not only able to inhibit the metabolic activity of biofilms, but also active upon the establishment and development of biofilm. Therefore, CM-chitosan may serve as a possible antibiofilm agent to limit biofilm formation on voice prostheses.

Antibiofilm activity of carboxymethyl chitosan on the biofilms of non-Candida albicans Candida species

Although most cases of candidiasis have been attributed to Candida albicans, non-C. albicans Candida species have been isolated in increasing numbers in patients. In this study, we determined the inhibition of carboxymethyl chitosan (CM-chitosan) on single and mixed species biofilm of non-albicans Candida species, including Candida tropicalis, Candida parapsilosis, Candida krusei and Candida glabrata. Biofilm by all tested species in microtiter plates were inhibited nearly 70%. CM-chitosan inhibited mixed species biofilm in microtiter plates and also on medical materials surfaces. To investigate the mechanism, the effect of CM-chitosan on cell viability and biofilm growth was employed. CM-chitosan inhibited Candida planktonic growth as well as adhesion. Further biofilm formation was inhibited with CM-chitosan added at 90min, 12h or 24h after biofilm initiation. CM-chitosan was not only able to inhibit the metabolic activity of Candida cells, but was also active upon the establishment and the development of biofilms.

Polysaccharide-based antibiofilm surfaces

Surface treatment by natural or modified polysaccharide polymers is a promising means to fight against implant-associated biofilm infections. The present review focuses on polysaccharide-based coatings that have been proposed over the last ten years to impede biofilm formation on material surfaces exposed to bacterial contamination. Anti-adhesive and bactericidal coatings are considered. Besides classical hydrophilic coatings based on hyaluronic acid and heparin, the promising anti-adhesive properties of the algal polysaccharide ulvan are underlined. Surface functionalization by antimicrobial chitosan and derivatives is extensively surveyed, in particular chitosan association with other polysaccharides in layer-by-layer assemblies to form both anti-adhesive and bactericidal coatings.

STATEMENT OF SIGNIFICANCE

Bacterial contamination of surfaces, leading to biofilm formation, is a major problem in fields as diverse as medicine, first, but also food and cosmetics. Many prophylactic strategies have emerged to try to eliminate or reduce bacterial adhesion and biofilm formation on surfaces of materials exposed to bacterial contamination, in particular implant materials. Polysaccharides are widely distributed in nature. A number of these natural polymers display antibiofilm properties. Hence, surface treatment by natural or modified polysaccharides is a promising means to fight against implant-associated biofilm infections. The present manuscript is an in-depth look at polysaccharide-based antibiofilm surfaces that have been proposed over the last ten years. This review, which is a novelty compared to published literature, will bring well documented and updated information to readers of Acta Biomaterialia.

Chitosan-based dressings loaded with neurotensin--an efficient strategy to improve early diabetic wound healing

One important complication of diabetes mellitus is chronic, non-healing diabetic foot ulcers (DFUs). This study aims to develop and use dressings based on chitosan derivatives for the sustained delivery of neurotensin (NT), a neuropeptide that acts as an inflammatory modulator in wound healing. Three different derivatives, namely N-carboxymethyl chitosan, 5-methyl pyrrolidinone chitosan (MPC) and N-succinyl chitosan, are presented as potential biomaterials for wound healing applications. Our results show that MPC has the best fluid handling capacity and delivery profile, also being non-toxic to Raw 264.7 and HaCaT cells. NT-loaded and non-loaded MPC dressings were applied to control/diabetic wounds to evaluate their in vitro/in vivo performance. The results show that the former induced more rapid healing (50% wound area reduction) in the early phases of wound healing in diabetic mice. A NT-loaded MPC foam also reduced expression of the inflammatory cytokine TNF-α (P<0.001) and decreased the amount of inflammatory infiltrate on day 3. On day 10 MMP-9 was reduced in diabetic skin (P<0.001), significantly increasing fibroblast migration and collagen (COL1A1, COL1A2 and COL3A1) expression and deposition. These results suggest that MPC-based dressings may work as an effective support for sustained NT release to reduce DFUs.

Recent advances on the development of wound dressings for diabetic foot ulcer treatment--a review

Diabetic foot ulcers (DFUs) are a chronic, non-healing complication of diabetes that lead to high hospital costs and, in extreme cases, to amputation. Diabetic neuropathy, peripheral vascular disease, abnormal cellular and cytokine/chemokine activity are among the main factors that hinder diabetic wound repair. DFUs represent a current and important challenge in the development of novel and efficient wound dressings. In general, an ideal wound dressing should provide a moist wound environment, offer protection from secondary infections, remove wound exudate and promote tissue regeneration. However, no existing dressing fulfills all the requirements associated with DFU treatment and the choice of the correct dressing depends on the wound type and stage, injury extension, patient condition and the tissues involved. Currently, there are different types of commercially available wound dressings that can be used for DFU treatment which differ on their application modes, materials, shape and on the methods employed for production. Dressing materials can include natural, modified and synthetic polymers, as well as their mixtures or combinations, processed in the form of films, foams, hydrocolloids and hydrogels. Moreover, wound dressings may be employed as medicated systems, through the delivery of healing enhancers and therapeutic substances (drugs, growth factors, peptides, stem cells and/or other bioactive substances). This work reviews the state of the art and the most recent advances in the development of wound dressings for DFU treatment. Special emphasis is given to systems employing new polymeric biomaterials, and to the latest and innovative therapeutic strategies and delivery approaches.