Addition of antimicrobial properties to hyaluronic acid by grafting of antimicrobial peptide

Rational design of antibiotic-free antimicrobial contact lenses: Trade-offs between antimicrobial performance and biocompatibility

Microbial keratitis associated with contact lenses (CLs) wear remains a significant clinical concern. Antibiotic therapy is the current standard of care. However, the emergence of multidrug-resistant pathogens necessitates the investigation of alternative strategies. Antibiotic-free antimicrobial contact lenses (AFAMCLs) represent a promising approach in this regard. The effectiveness of CLs constructed with a variety of antibiotic-free antimicrobial strategies against microorganisms has been demonstrated. However, the impact of these antimicrobial strategies on CLs biocompatibility remains unclear. In the design and development of AFAMCLs, striking a balance between robust antimicrobial performance and optimal biocompatibility, including safety and wearing comfort, is a key issue. This review provides a comprehensive overview of recent advancements in AFAMCLs technology. The focus is on the antimicrobial efficacy and safety of various strategies employed in AFAMCLs construction. Furthermore, this review investigates the potential impact of these strategies on CLs parameters related to wearer comfort. This review aims to contribute to the continuous improvement of AFAMCLs and provide a reference for the trade-off between resistance to microorganisms and wearing comfort. In addition, it is hoped that this review can also provide a reference for the antimicrobial design of other medical devices.

Chemical Modifications in Hyaluronic Acid-Based Electrospun Scaffolds

Hyaluronic acid (HA) is a natural, non-sulfated glycosaminoglycan (GAG) present in ECM. It is involved in different biological functions with appealing properties in cosmetics and pharmaceutical preparations as well as in tissue engineering. Generally, HA has been electrospun in blends with natural or synthetic polymers to produce fibers having diameters in the order of nano and micro-scale whose pores can host cells able to regenerate damaged tissues. In the last decade, a rich literature on electrospun HA-based materials arose. Chemical modifications were generally introduced in HA scaffolds to favour crosslinking or conjugation with bioactive molecules. Considering the high solubility of HA in water, HA-based electrospun scaffolds are cross-linked to increase the stability in biological fluids. Crosslinking is necessary also to avoid the release of HA from the hybrid scaffold when implanted in-vivo. Furthermore, to endow the HA based scaffolds with new chemical or biological properties, conjugation of bioactive molecules to HA was widely reported. Herein, we review the existing research classifying chemical modifications on HA and HA-based electrospun fibers into three categories: i) in-situ crosslinking of electrospun HA-based scaffolds ii) off-site crosslinking of electrospun HA-based scaffolds; iii) conjugation of biofunctional molecules to HA with focus on peptides.

Advances in guided bone regeneration membranes: a comprehensive review of materials and techniques

Guided tissue/bone regeneration (GTR/GBR) is a widely used technique in dentistry to facilitate the regeneration of damaged bone and tissue, which involves guiding materials that eventually degrade, allowing newly created tissue to take its place. This comprehensive review the evolution of biomaterials for guided bone regeneration that showcases a progressive shift from non-resorbable to highly biocompatible and bioactive materials, allowing for more effective and predictable bone regeneration. The evolution of biomaterials for guided bone regeneration GTR/GBR has marked a significant progression in regenerative dentistry and maxillofacial surgery. Biomaterials used in GBR have evolved over time to enhance biocompatibility, bioactivity, and efficacy in promoting bone growth and integration. This review also probes into several promising fabrication techniques like electrospinning and latest 3D printing fabrication techniques, which have shown potential in enhancing tissue and bone regeneration processes. Further, the challenges and future direction of GTR/GBR are explored and discussed.

Synthetic and biopolymers-based antimicrobial hybrid hydrogels: a focused review

The constantly accelerating occurrence of microbial infections and their antibiotic resistance has spurred advancement in the field of material sciences and has guided the development of novel materials with anti-bacterial properties. To address the clinical exigencies, the material of choice should be biodegradable, biocompatible, and able to offer prolonged antibacterial effects. As an attractive option, hydrogels have been explored globally as a potent biomaterial platform that can furnish essential antibacterial attributes owing to its three-dimensional (3D) hydrophilic polymeric network, adequate biocompatibility, and cellular adhesion. The current review focuses on the utilization of different antimicrobial hydrogels based on their sources (natural and synthetic). Further, the review also highlights the strategies for the generation of hydrogels with their advantages and disadvantages and their applications in different biomedical fields. Finally, the prospects in the development of hydrogels-based antimicrobial biomaterials are discussed along with some key challenges encountered during their development and clinical translation.

Synthesis, characterization, and antibacterial effect of St. John's wort oil loaded chitosan hydrogel

Hydrogels prepared with natural and synthetic polymers were found to be applicable for the development of resistance against some Gram positive and negative bacterial species. Numerous studies have shown that chitosan polymers can be advantageous to be used in medicine due to their high antibacterial activity. In this study, biocompatible yellow cantorone oil doped hydrogels (chitosan/poly(vinyl alcohol) based) with antimicrobial properties were synthesized. The structural, morphological, swelling and mechanical properties of these biocompatible hydrogels prepared by double crosslinking were investigated and characterized. FTIR spectroscopy showed the appearance of new imine and acetal bonds due to both covalent cross-linking. In vitro cytotoxicity evaluation revealed that hydrogels showed weak cytotoxic effect. In the antimicrobial evaluation, it was determined that the hydrogel containing only chitosan showed better antimicrobial effect against Escherichia coli, Pseudomonas auriginosa, Staphylococcus aureus and Enterococcus faecalis bacteria than the one containing St. John's Wort oil. The antibacterial effect of polyvinyl alcohol/chitosan hydrogel was low. In our wound healing study, chitosan hydrogel loaded with yellow St. John's Wort oil was more effective in reducing wound size.

Conjugation of antimicrobial peptides to enhance therapeutic efficacy

The growing prevalence of antimicrobial resistance (AMR) has brought with it a continual increase in the numbers of deaths from multidrug-resistant (MDR) infections. Since the current arsenal of antibiotics has become increasingly ineffective, there exists an urgent need for discovery and development of novel antimicrobials. Antimicrobial peptides (AMPs) are considered to be a promising class of molecules due to their broad-spectrum activities and low resistance rates compared with other types of antibiotics. Since AMPs also often play major roles in elevating the host immune response, the molecules may also be called "host defense peptides." Despite the great promise of AMPs, the majority remain unsuitable for clinical use due to issues of structural instability, degradation by proteases, and/or toxicity to host cells. Moreover, AMP activities in vivo can be influenced by many factors, such as interaction with blood and serum biomolecules, physiological salt concentrations or different pH values. To overcome these limitations, structural modifications can be made to the AMP. Among several modifications, physical and chemical conjugation of AMP to other biomolecules is widely considered an effective strategy. In this review, we discuss structural modification strategies related to conjugation of AMPs and their possible effects on mode of action. The conjugation of fatty acids, glycans, antibiotics, photosensitizers, polymers, nucleic acids, nanoparticles, and immobilization to biomaterials are highlighted.

Tapping on the Potential of Hyaluronic Acid: from Production to Application

The manufacture, purification, and applications of hyaluronic acid (HA) are discussed in this article. Concerning the growing need for affordable, high-quality HA, it is essential to consider diverse production techniques using renewable resources that pose little risk of cross-contamination. Many microorganisms can now be used to produce HA without limiting the availability of raw materials and in an environmentally friendly manner. The production of HA has been associated with Streptococci A and C, explicitly S. zooepidemicus and S. equi. Different fermentation techniques, including the continuous, batch, fed-batch, and repeated batch culture, have been explored to increase the formation of HA, particularly from S. zooepidemicus. The topic of current interest also involves a complex broth rich in metabolites and residual substrates, intensifying downstream processes to achieve high recovery rates and purity. Although there are already established methods for commercial HA production, the anticipated growth in trade and the diversification of application opportunities necessitate the development of new procedures to produce HA with escalated productivity, specified molecular weights, and purity. In this report, we have enacted the advancement of HA technical research by analyzing bacterial biomanufacturing elements, upstream and downstream methodologies, and commercial-scale HA scenarios.

Chitosan-Based Hydrogels for Infected Wound Treatment

Wound infections slow down the healing process and lead to complications such as septicemia, osteomyelitis, and even death. Although traditional methods relying on antibiotics are effective in controlling infection, they have led to the emergence of antibiotic-resistant bacteria. Hydrogels with antimicrobial function become a viable option for reducing bacterial colonization and infection while also accelerating healing processes. Chitosan is extensively developed as antibacterial wound dressings due to its unique biochemical properties and inherent antibacterial activity. In this review, the recent research progress of chitosan-based hydrogels for infected wound treatment, including the fabrication methods, antibacterial mechanisms, antibacterial performance, wound healing efficacy, etc., is summarized. A concise assessment of current limitations and future trends is presented.

Polysaccharide-based nanoassemblies: From synthesis methodologies and industrial applications to future prospects

Polysaccharides, due to their remarkable features, have gained significant prominence in the sustainable production of nanoparticles (NPs). High market demand and minimal production cost, compared to the chemically synthesised NPs, demonstrate a drive towards polysaccharide-based nanoparticles (PSNPs) benign to environment. Various approaches are used for the synthesis of PSNPs including cross-linking, polyelectrolyte complexation, and self-assembly. PSNPs have the potential to replace a wide diversity of chemical-based agents within the food, health, medical and pharmacy sectors. Nevertheless, the considerable challenges associated with optimising the characteristics of PSNPs to meet specific targeting applications are of utmost importance. This review provides a detailed compilation of recent accomplishments in the synthesis of PSNPs, the fundamental principles and critical factors that govern their rational fabrication, as well as various characterisation techniques. Noteworthy, the multiple use of PSNPs in different disciplines such as biomedical, cosmetics agrochemicals, energy storage, water detoxification, and food-related realms, is accounted in detail. Insights into the toxicological impacts of the PSNPs and their possible risks to human health are addressed, and efforts made in terms of PSNPs development and optimising strategies that allow for enhanced delivery are highlighted. Finally, limitations, potential drawbacks, market diffusion, economic viability and future possibilities for PSNPs to achieve widespread commercial use are also discussed.

Advances in Antimicrobial Peptide Discovery via Machine Learning and Delivery via Nanotechnology

Antimicrobial peptides (AMPs) have been investigated for their potential use as an alternative to antibiotics due to the increased demand for new antimicrobial agents. AMPs, widely found in nature and obtained from microorganisms, have a broad range of antimicrobial protection, allowing them to be applied in the treatment of infections caused by various pathogenic microorganisms. Since these peptides are primarily cationic, they prefer anionic bacterial membranes due to electrostatic interactions. However, the applications of AMPs are currently limited owing to their hemolytic activity, poor bioavailability, degradation from proteolytic enzymes, and high-cost production. To overcome these limitations, nanotechnology has been used to improve AMP bioavailability, permeation across barriers, and/or protection against degradation. In addition, machine learning has been investigated due to its time-saving and cost-effective algorithms to predict AMPs. There are numerous databases available to train machine learning models. In this review, we focus on nanotechnology approaches for AMP delivery and advances in AMP design via machine learning. The AMP sources, classification, structures, antimicrobial mechanisms, their role in diseases, peptide engineering technologies, currently available databases, and machine learning techniques used to predict AMPs with minimal toxicity are discussed in detail.

Hyaluronic Acid-Based Antibacterial Hydrogels for Use as Wound Dressings

Wound dressings have been shifting toward a more active role in the wound-healing process. Hydrated environments with additives to aid in the healing process are currently being explored through the application of hydrocolloid dressings. However, these moist healing environments are also ideal for bacterial growth, leading to the widespread use of antibiotics with concerns of antibiotic resistance and toxicity. To overcome this concern, we present a hydrogel wound dressing consisting of hyaluronic acid (HA) cross-linked with gentamicin. This hydrogel treats bacterial infection locally, lowering the effective dose and reducing the concerns of antibiotic resistance and systemic exposure. Changing the cross-linking density, by using varied amounts of a cross-linker, created gels that provided a sustained release of gentamicin for up to 9 days with a range of adhesive and cohesive properties. Overall, this HA hydrogel could provide an important solution in treating local infection in burns and other dermal injuries.

Lidocaine- and chloramphenicol-loaded nanoparticles embedded in a chitosan/hyaluronic acid/glycerol matrix: Drug-eluting biomembranes with potential for guided tissue regeneration

Guided tissue regeneration (GTR) is a dentistry technique based on the use of polymeric biomembranes as physical barriers for selective cell exclusion, directing the growth of gingival tissue, bone tissue, and periodontal ligaments in a region previously affected by periodontitis. Postoperative pain and microbial infection constitute, however, two major challenges to be tackled right after implantation. To address these challenges, we prepared and characterized eight chitosan/hyaluronic acid/glycerol (CS/HA/GL) bioresorbable membranes embedded with lidocaine- and chloramphenicol-loaded polycaprolactone nanoparticles (LDNP and CHNP, respectively), combining the local anesthetic effects of lidocaine with the antibacterial effects of chloramphenicol. The formulations were prepared with varying amounts of CS, HA, GL, LDNP, and CHNP. As a plasticizing agent, GL could modulate the samples mechanical properties such as thickness, morphology, tensile strength, elongation at break, as well as swelling and degradation in simulated saliva. Two samples exhibited greater resistance to biodegradation and were selected for further studies. Their drug release profiles indicated that LDNP and CHNP first detach from the membrane matrix, and a zeroth order drug release kinetics from the detached NPs dominates the overall process thereafter, with lidocaine being released 3 times faster than chloramphenicol, in a controlled and sustained rate over time. Drug encapsulation efficiency was such that optimal samples exhibited bactericidal activity (inhibition halos) against gram-positive S. aureus and gram-negative A. actinomycetemcomitans strains similar to that observed for free chloramphenicol. Finally, one of these samples showed no intrinsic toxicity against healthy mammalian model cells (99% viability for the unloaded membrane; 80% viability for the fully LDNP- and CHNP-loaded membrane), and may now be further optimized as a drug-eluting biomembrane with potential for GTR.

Hyaluronic Acid-Based Wound Dressing with Antimicrobial Properties for Wound Healing Application

Wound healing is a naturally occurring process that can be aided by a wound dressing properly designed to assure an efficient healing process. An infection caused by several microorganisms could interfere with this process, delaying or even impairing wound healing. Hyaluronic acid (HA), a main constituent of the extracellular matrix (ECM) of a vertebrate’s connective tissue, represents a promising biomaterial for wound dressing thanks to its intrinsic biocompatibility, hydrophilicity and bacteriostatic properties. In this review, different and recent types of HA-based wound dressings endowed with intrinsic antimicrobial properties or co-adjuvated by antimicrobial natural or synthetic agents are highlighted.

Biocomposite Hydrogels for the Treatment of Bacterial Infections: Physicochemical Characterization and In Vitro Assessment

Hydrogels based on natural and synthetic polymers and inorganic nanoparticles proved to be a viable strategy in the fight against some Gram-positive and Gram-negative bacteria. Additionally, numerous studies have demonstrated the advantages of using ZnO nanoparticles in medicine due to their high antibacterial efficacy and relatively low cost. Consequently, the purpose of our study was to incorporate ZnO nanoparticles into chitosan/poly (vinyl alcohol)-based hydrogels in order to obtain a biocomposite with antimicrobial properties. These biocomposite hydrogels, prepared by a double crosslinking (covalent and ionic) were characterized from a structural, morphological, swelling degree, and mechanical point of view. FTIR spectroscopy demonstrated both the apparition of new imine and acetal bonds due to covalent crosslinking and the presence of the sulfate group following ionic crosslinking. The morphology, swelling degree, and mechanical properties of the obtained hydrogels were influenced by both the degree of covalent crosslinking and the amount of ZnO nanoparticles incorporated. In vitro cytotoxicity assessment showed that hydrogels without ZnONPs are non-cytotoxic while the biocomposite hydrogels are weak (with 3% ZnONPs) or moderately (with 4 and 5% ZnONPs) cytotoxic. Compared to nanoparticle-free hydrogels, the biocomposite hydrogels show significant antimicrobial activity against S. aureus, E. coli, and K. pneumonia.

Discovery, Optimization, and Clinical Application of Natural Antimicrobial Peptides

Antimicrobial peptides (AMPs) are widespread in multicellular organisms. These structurally diverse molecules are produced as the first line of defense against pathogens such as bacteria, viruses, fungi, and parasites. Also known as host defense peptides in higher eukaryotic organisms, AMPs display immunomodulatory and anticancer activities. During the last 30 years, technological advances have boosted the research on antimicrobial peptides, which have also attracted great interest as an alternative to tackling the antimicrobial resistance scenario mainly provoked by some bacterial and fungal pathogens. However, the introduction of natural AMPs in clinical trials faces challenges such as proteolytic digestion, short half-lives, and cytotoxicity upon systemic and oral application. Therefore, some strategies have been implemented to improve the properties of AMPs aiming to be used as effective therapeutic agents. In the present review, we summarize the discovery path of AMPs, focusing on preclinical development, recent advances in chemical optimization and peptide delivery systems, and their introduction into the market.

Molecular engineering of antimicrobial peptide (AMP)-polymer conjugates

As antimicrobial resistance becomes an increasing threat, bringing significant economic and health burdens, innovative antimicrobial treatments are urgently needed. While antimicrobial peptides (AMPs) are promising therapeutics, exhibiting high activity against resistant bacterial strains, limited stability and toxicity to mammalian cells has hindered clinical development. Attaching AMPs to polymers provides opportunities to present AMPs in a way that maximizes bacterial killing while enhancing compatibility with mammalian cells, stability, and solubility. Conjugation of an AMP to a linear hydrophilic polymer yields the desired improvements in stability, mammalian cell compatibility, and solubility, yet often markedly reduces bactericidal effects. Non-linear polymer architectures and supramolecular assemblies that accommodate multiple AMPs per polymer chain afford AMP-polymer conjugates that strike a superior balance of antimicrobial activity, mammalian cell compatibility, stability, and solubility. Therefore, we review the design criteria, building blocks, and synthetic strategies for engineering AMP-polymer conjugates, emphasizing the connection between molecular architecture and antimicrobial performance to inspire and enable further innovation to advance this emerging class of biomaterials.

Advantages of Hyaluronic Acid and Its Combination with Other Bioactive Ingredients in Cosmeceuticals

This study proposes a review on hyaluronic acid (HA) known as hyaluronan or hyaluronate and its derivates and their application in cosmetic formulations. HA is a glycosaminoglycan constituted from two disaccharides (N-acetylglucosamine and D-glucuronic acid), isolated initially from the vitreous humour of the eye, and subsequently discovered in different tissues or fluids (especially in the articular cartilage and the synovial fluid). It is ubiquitous in vertebrates, including humans, and it is involved in diverse biological processes, such as cell differentiation, embryological development, inflammation, wound healing, etc. HA has many qualities that recommend it over other substances used in skin regeneration, with moisturizing and anti-ageing effects. HA molecular weight influences its penetration into the skin and its biological activity. Considering that, nowadays, hyaluronic acid has a wide use and a multitude of applications (in ophthalmology, arthrology, pneumology, rhinology, aesthetic medicine, oncology, nutrition, and cosmetics), the present study describes the main aspects related to its use in cosmetology. The biological effect of HA on the skin level and its potential adverse effects are discussed. Some available cosmetic products containing HA have been identified from the brand portfolio of most known manufacturers and their composition was evaluated. Further, additional biological effects due to the other active ingredients (plant extracts, vitamins, amino acids, peptides, proteins, saccharides, probiotics, etc.) are presented, as well as a description of their possible toxic effects.

Hyaluronan/colistin polyelectrolyte complexes: Promising antiinfective drug delivery systems

Nanotechnology-based modification of known antimicrobial agents is a rational and straightforward way to improve their safety and effectiveness. The aim of this study was to develop colistin (CT)-loaded polymeric carriers based on hyaluronic acid (HA) for potential application as antimicrobial agents against multi-resistant gram-negative microorganisms (including ESKAPE pathogens). CT-containing particles were obtained via a polyelectrolyte interaction between protonated CT amino groups and HA carboxyl groups (the CT-HA complex formation constant [logK_CT-HA] was about 5.0). The resulting polyelectrolyte complexes had a size of 210-250 nm and a negative charge (ζ-potential -19 mV), with encapsulation and loading efficiencies of 100% and 20%, respectively. The developed CT delivery systems were characterized by modified release (45% and 85% of CT released in 15 and 60 min, respectively) compared to pure CT (100% CT released in 15 min). In vitro tests showed that the encapsulation of CT in polymer particles did not reduce its pharmacological activity; the minimum inhibitory concentrations of both encapsulated CT and pure CT were 1 μg/mL (against Pseudomonas aeruginosa).

Characterization of hyaluronic acid extracted from Liparis tessellatus eggs grafted with phenolic acids and nisin

In polymer therapeutics, polymer-based carrier systems conjugated with antioxidants have been synthesized and studied to improve diagnosis and treatment of diseases, such as, in cancer and tumor. The natural bioactive compound hyaluronic acid (HA), which is essential in medical and pharmaceutical fields, is a linear polymer composed of repeating disaccharide units of β-1,3-N-acetyl glucosamine and β-1,4-glucuronic acid. In this study, HA fractions of enzyme-assisted glycosaminoglycans (GAGs) extract from Liparis tessellatus eggs were grafted with gallic acid (GA), caffeic acid (CA), and ferulic acid (FA) via a free radical-mediated method, and with nisin via amide bond formation. The modification has been confirmed through FTIR and ¹H NMR spectroscopy and quantified by Folin-Ciocalteu and Bradford assay. FTIR spectra of grafted HA samples exhibited the typical phenolic characteristics within 1450-1650 cm^-1, and the formation of amide bond in nisin-grafted HA was shown by absorption peak within 1545-1646 cm^-1. ¹H NMR spectra showed new peaks of phenyl protons at 6.3-7.7 ppm and new peaks at 0.9-2.9 ppm of amino acids residues protons. These results all confirmed the successful grafting of GA, CA, FA and nisin onto the HA backbone extracted from L. tessellatus eggs.

Supramolecular Peptide Assemblies as Antimicrobial Scaffolds

Antimicrobial discovery in the age of antibiotic resistance has demanded the prioritization of non-conventional therapies that act on new targets or employ novel mechanisms. Among these, supramolecular antimicrobial peptide assemblies have emerged as attractive therapeutic platforms, operating as both the bactericidal agent and delivery vector for combinatorial antibiotics. Leveraging their programmable inter- and intra-molecular interactions, peptides can be engineered to form higher ordered monolithic or co-assembled structures, including nano-fibers, -nets, and -tubes, where their unique bifunctionalities often emerge from the supramolecular state. Further advancements have included the formation of macroscopic hydrogels that act as bioresponsive, bactericidal materials. This systematic review covers recent advances in the development of supramolecular antimicrobial peptide technologies and discusses their potential impact on future drug discovery efforts.

Clinical Applications of Antimicrobial Peptides (AMPs): Where do we Stand Now?

In this era of multi-drug resistance (MDR), antimicrobial peptides (AMPs) are one of the most promising classes of potential drug candidates to combat communicable as well as noncommunicable diseases such as cancers and diabetes. AMPs show a wide spectrum of biological activities which include antiviral, antifungal, anti-mitogenic, anticancer, and anti-inflammatory properties. Apart from these prospective therapeutic potentials, the AMPs can act as food preservatives and immune modulators. Therefore, AMPs have the potential to replace conventional drugs and may gain a significant global drug market share. Although several AMPs have shown therapeutic potential in vitro or in vivo, in most cases they have failed the clinical trial owing to various issues. In this review, we discuss in brief (i) molecular mechanisms of AMPs in various diseases, (ii) importance of AMPs in pharmaceutical industries, (iii) the challenges in using AMPs as therapeutics and how to overcome, (iv) available AMP therapeutics in market, and (v) AMPs under clinical trials. Here, we specifically focus on the therapeutic AMPs in the areas of dermatology, surgery, oncology and metabolic diseases.

Hyaluronic Acid and Controlled Release: A Review

Hyaluronic acid (HA) also known as hyaluronan, is a natural polysaccharide—an anionic, non-sulfated glycosaminoglycan—commonly found in our bodies. It occurs in the highest concentrations in the eyes and joints. Today HA is used during certain eye surgeries and in the treatment of dry eye disease. It is a remarkable natural lubricant that can be injected into the knee for patients with knee osteoarthritis. HA has also excellent gelling properties due to its capability to bind water very quickly. As such, it is one the most attractive controlled drug release matrices and as such, it is frequently used in various biomedical applications. Due to its reactivity, HA can be cross-linked or conjugated with assorted bio-macromolecules and it can effectively encapsulate several different types of drugs, even at nanoscale. Moreover, the physiological significance of the interactions between HA and its main membrane receptor, CD44 (a cell-surface glycoprotein that modulates cell–cell interactions, cell adhesion and migration), in pathological processes, e.g., cancer, is well recognized and this has resulted in an extensive amount of studies on cancer drug delivery and tumor targeting. HA acts as a therapeutic but also as a tunable matrix for drug release. Thus, this review focuses on controlled or sustained drug release systems assembled from HA and its derivatives. More specifically, recent advances in controlled release of proteins, antiseptics, antibiotics and cancer targeting drugs from HA and its derivatives were reviewed. It was shown that controlled release from HA has many benefits such as optimum drug concentration maintenance, enhanced therapeutic effects, improved efficiency of treatment with less drug, very low or insignificant toxicity and prolonged in vivo release rates.

Polyanionic Hydrogels as Reservoirs for Polycationic Antibiotic Substitutes Providing Prolonged Antibacterial Activity

Implantation of biomedical devices is often followed by bacterial infections that may seriously affect implant functionalities and lead to their failure. In the context of bacterial resistance to antibiotics, which is a growing problem worldwide, new strategies that are able to overcome these problems are needed. In this work, we introduce a new formulation of hyaluronic acid (HA)-based antimicrobial material: HA hydrogels loaded with polyarginine (PAR), a polycationic antibiotic substitute. The loading is possible through electrostatic interactions between negatively charged HA and positively charged PAR. Such hydrogels absorb high quantities of PAR, which are then gradually released from the hydrogel. This original system provides a long-lasting antibacterial effect on an in vitro model of repetitive infection, thus demonstrating a strong potential to fight multiple rounds of infections that are resistant to antibiotic treatment. In addition, HA-PAR hydrogels could be deposited onto/into medical devices such as wound dressings and mesh prostheses used in clinical applications. Finally, we performed first in vivo tests of hydrogel-coated mesh materials to verify their biocompatibility in a rat model, which show no difference between control HA hydrogel and PAR-loaded hydrogel in terms of inflammation.

Functionalized polysaccharides with aminoguaiacol: a competition between associative behavior and antibacterial and antioxidant activities

In a previous study, we presented the development of a series of functionalized carboxymethylpullulan (CMP) grafted with aminoguaiacol (derivative of guaiacol with known antibacterial and antioxidant activities) leading to CMP-G derivatives with various degrees of substitution [DS(Ga)] from 0.16 to 0.58. Our results have shown the efficiency of the grafting both with the evidence of antioxidant and antibacterial activities (Staphylococcus aureus) of the CMP-G derivatives. Nevertheless, an important result has shown surprisingly that such biological activity was not clearly improved with the DS(Ga) unlike the antioxidant activity. These results were probably correlated with a peculiar associative behavior of the derivative (i.e. amphiphilic character) due to the grafted hydrophobic guaiacol groups leading to preferential intramolecular association which was particularly important in the more concentrated regime (polysoap behavior). To complete this study, we propose here two strategies in order to diminish the associative character and notably the polysoap behavior: (i) decrease the DS(Ga) of CMP derivative with a CMP-G0.05 [grafted with a DS(Ga) = 0.05], (ii) conduct the functionalization onto a more rigid polysaccharide backbone as alginate. Our results show a good correlation of the associative physicochemical behaviors with both antioxidant and antibacterial activities. They also confirm the availability of these strategies mainly for the first one (i.e. CMP-G0.05). The main result indicates that the lower is the DS(Ga), the better is the antibacterial activity thanks to a lower associative character. Finally, this study also shows that the grafting of aminoguaiacol is possible onto another anionic polysaccharide (i.e. alginate).

Structural design and antimicrobial properties of polypeptides and saccharide–polypeptide conjugates

The development and progress of antimicrobial polypeptides and saccharide–polypeptide conjugates in regards to their structural design, biological functions and antimicrobial mechanism.

Enhancing biocompatibility and neuronal anti-inflammatory activity of polymyxin B through conjugation with gellan gum

Polymyxins, as strong antibiotics with high liposaccharide deactivation abilities, are rarely used as neuronal anti-inflammatory agent because of their high cytotoxicity. In this study, polymyxin B (PMB) was conjugated with deacylated gellan gum for the sustained release of PMB to reduce its cytotoxicity at high concentration without affecting the antibacterial and liposaccharide binding activities. For the conjugate of original PMB/GN ratio of 1.0 (GPC), the conjugating rate was 96.40%, and the releasing ratio of PMB was 30.12% within 60 h. The FT-IR spectra of GPC indicated that the amino groups of PMB were covalently bonded with the COOH groups of gellan and other PMB molecules. Most GPCs were micelle shaped regardless of whether they were under dry conditions or in an aqueous solution. The inhibition zones of PMB against Escherichia coli and Pseudomonas aeruginosa were small, but the half maximal inhibitory concentration value against BV-2 cells increased from 15.63 μg/mL to 2000.00 μg/mL after conjugation. GPC can also effectively depress the liposaccharide-stimulated overexpression of cytotoxic nitric oxide by BV-2 cells. This study revealed the possibility of using polymyxins for neuronal anti-inflammation and that this gellan/PMB conjugate can potentially be applied to wound healing and implants.

The application of hyaluronic acid in bone regeneration

Hyaluronic acid (HA) exists naturally as an important component of the extracellular matrix (ECM) in the human body. In recent decades, HA has been widely used in bone regeneration, and is currently a popular topic, particularly in the craniofacial and dental fields. From maxilla augmentation to craniofacial bone trauma, there is now a large demand for bone regenerative therapy. Serving as a cell-seeding scaffold or a carrier for bioactive components, hyaluronic acid-incorporated scaffolds and carriers in bone regeneration can be fabricated into either rigid or colloidal forms. Since the type of material used is a critical factor in the biological properties of a scaffold, HA derivatives or HA-incorporated composite scaffolds have shown excellent potential for improving osteogenesis and mineralization. Furthermore, in order to better enhance osteogenesis, local delivery carriers based on hyaluronic acid derivatives, rather than specifically serving as scaffolds, can be established by loading different osteoinductive or osteogenetic components and acquiring different release patterns. Such osteoinductive carriers immobilized on implant surfaces are also effective in improving osseointegration. Thus, as such a competent biomaterial, hyaluronic acid should be considered a promising tool in bone regeneration.

Various methods to combine hyaluronic acid and antimicrobial peptides coatings and evaluation of their antibacterial behaviour

To prevent bacterial adhesion and contamination, biomaterials exhibiting both antiadhesive and biocidal properties are the most promising way. However, control of the properties combination is not so easy due, in particular, to antagonist mechanisms. Antibacterial surfaces against Staphylococcus epidermidis adhesion were here elaborated by using both nisin grafting and repelling polysaccharide coating. We evaluated two strategies aiming to improve the antimicrobial peptide (AMP) immobilization parameters (i.e., the accessibility and/or local density) in order to obtain the best antimicrobial activity on surfaces. We thus (i) grafted the nisin on a surface previously coated with hydrolyzed hyaluronic acid (HA) (to decrease the length of the polysaccharide chains) or (ii) coupled nisin and HA in solution before grafting this complex on surfaces. XPS analysis pointed out a lower amount of nisin on the surface for both approaches compared to the immobilization of nisin on native HA. However, an antibacterial activity was maintained, probably due to a higher local density of the AMP when surfaces were modified with hydrolyzed hyaluronic acid, leading to a better combination of antiadhesive-biocidal properties. Microscopy fluorescent observations demonstrated that accumulation of dead cells was also avoided by some coatings architecture.

Modifications of Polymeric Membranes Used in Guided Tissue and Bone Regeneration

Guided tissue/bone regeneration (GTR/GBR) is a widely used procedure in contemporary dentistry. To achieve the required results of tissue regeneration, soft tissues that reproduce quickly are separated from the slow-growing bone tissue by membranes. Many types of membranes are currently in use, but none of them fulfil all of the desired features. To address this issue, further research on developing new membranes with better separation characteristics, such as membrane modification, is needed. Many of the current innovative modified materials are still in the phase of in vitro and experimental studies. A collective review on new trends in membrane modification to GTR/GBR is needed due to the widespread use of polymeric membranes and the constant development in the field of dentistry. Therefore, the aim of this review was to present an overview of polymeric membrane modifications to the GTR/GBR reported in the literature. The authors searched databases, including PubMed, SCOPUS, Web of Science, and OVID, for relevant studies that were published during 1999-2019. The following keywords were used: guided tissue regeneration, membranes, coating, and modification. A total of 17 papers were included in this review. Furthermore, the articles were divided into three groups that were based on the type of membrane modification: antibiotic coating, ion-use modifications, and others modifications, thus providing an overview of current existing knowledge in the field and encouraging further research. The results of included studies on modified barrier membranes seem to be promising, both in terms of safety and benefits for patients. However, modifications result in a large spectrum of effects. Further clinical studies are needed on a large group of patients to clearly confirm the effects that were observed in animal and in vitro studies.

Antimicrobial polylysine decorated nano-structures prepared through polymerization induced self-assembly (PISA)

Polylysine decorated diblock copolymer nano-objects are prepared by polymerization-induced self-assemblyviaRAFT dispersion polymerization of 2-hydroxypropyl methacrylate. Antimicrobial properties of the resulting nano-objects evaluated using a gram positive bacteria.

Elastic-Plastic Transformation of Polyelectrolyte Complex Hydrogels from Chitosan and Sodium Hyaluronate

Hydrogels formed by polyelectrolyte complexation (PEC) of oppositely charged biopolymers, free of any chemical additives, are promising biomaterials. In this work, the mechanical behavior of hydrogels consisting of positively charged chitosan and negatively charged sodium hyaluronate (HA) at balanced charge composition is investigated. These hydrogels exhibit strong tensile strain and strain rate dependence. They are elastic-like, independent of the strain rate at small strain, but exhibit plastic-like behavior above the yield point by showing a monotonous decrease of the stress. The cyclic tensile test demonstrates that these hydrogels exhibit small and quickly recoverable hysteresis in the elastic-like region, but large and partially recoverable hysteresis above the yield point. The stress relaxation experiment shows a plateau in the reduced stress followed by an abrupt fracture, and the time-to-failure decreases exponentially with increasing applied step-strain. Such elastic-to-plastic-like transformation of the biopolymer PEC gels is quite different from the behaviors of PEC hydrogels formed by oppositely charged vinyl-type synthetic polyelectrolytes due to the difference in flexibility, charge density, and ionic bond strength of these polymers.

Anti-bacterial materials based on hyaluronic acid: Selection of research methodology and analysis of their anti-bacterial properties

In the frame of the presented research, highly-porous structures made of hyaluronic acid modified with bioactive compounds were prepared. The method of microbiological testing of hygroscopic materials has been elaborated by verification of the JIS L 1902:2002 and ASTM E2149-13a test methods. The research has shown that the method developed in accordance with ASTM E2149-13a is suitable for testing the activity of hyaluronic acid samples against bacteria. E. coli and S. aureus. In the case of E. coli it is preferred to use as a medium the phosphoric buffer and for S. aureus NaCl solution from NB. By analysing the results of the antibacterial properties, it is important to note that the introduction of a small amount of zinc and zinc oxide in the matrix from the hyaluronic acid (in the amount of 3% by weight of the polymer) makes it possible to obtain a material with a strong activity against the bacterial strains. It enables to use this type of material as a treatment for hard-to-treat, infected wounds. On the other hand, using a relatively small dose of the cephalosporin antibiotic did not result in high levels of activity against the bacteria Gram "+" and Gram "-".

Antibacterial Hydrogels

Antibacterial materials are recognized as important biomaterials due to their effective inhibition of bacterial infections. Hydrogels are 3D polymer networks crosslinked by either physical interactions or covalent bonds. Currently, hydrogels with an antibacterial function are a main focus in biomedical research. Many advanced antibacterial hydrogels are developed, each possessing unique qualities, namely high water swellability, high oxygen permeability, improved biocompatibility, ease of loading and releasing drugs, and structural diversity. Here, an overview of the structures, performances, mechanisms of action, loading and release behaviors, and applications of various antibacterial hydrogel formulations is provided. Furthermore, the prospects in biomedical research and clinical applications are predicted.

Synthesis, Self-Assembly, and Biomedical Applications of Antimicrobial Peptide-Polymer Conjugates

Antimicrobial peptides (AMPs) have been attracting much attention due to their excellent antimicrobial efficiency and low rate in driving antimicrobial resistance (AMR), which has been increasing globally to alarming levels. Conjugation of AMPs into functional polymers not only preserves excellent antimicrobial activities but reduces the toxicity and offers more functionalities, which brings new insight toward developing multifunctional biomedical materials such as hydrogels, polymer vesicles, polymer micelles, and so forth. These nanomaterials have been exhibiting excellent antimicrobial activity against a broad spectrum of bacteria including multidrug-resistant (MDR) ones, high selectivity, and low cytotoxicity, suggesting promising potentials in wound dressing, implant coating, antibiofilm, tissue engineering, and so forth. This Perspective seeks to highlight the state-of-the-art strategy for the synthesis, self-assembly, and biomedical applications of AMP-polymer conjugates and explore the promising directions for future research ranging from synthetic strategies, multistage and stimuli-responsive antibacterial activities, antifungi applications, and potentials in elimination of inflammation during medical treatment. It also will provide perspectives on how to stem the remaining challenges and unresolved problems in combating bacteria, including MDR ones.