Chitosan based hydrogels and their applications for drug delivery in wound dressings: A review

Molecular Staples for Tough and Stretchable Adhesion in Integrated Soft Materials

The integration of soft materials-biological tissues, gels, and elastomers-is a rapidly developing technology of this time. Whereas hard materials are adhered using adhesives of hard polymers since antiquity, these hard polymers are generally unsuited to adhere soft materials, because hard polymers constrain the deformation of soft materials. This paper describes a design principle to use hard polymers to adhere soft materials, such that adhesion remains tough after the adhered soft materials are subject to many cycles of large stretches in the plane of their interface. The two soft materials have stretchable polymer networks, but need not have functional groups for adhesion. The two soft materials are adhered by forming, in situ at their interface, islands of a hard polymer. The adhesion is tough if the islands themselves are strong, and the polymers of the islands are in topological entanglement with the polymer networks of the soft materials. The adhesion is stretchable if the islands are smaller than the flaw sensitivity length. Several methods of forming the hard polymer islands are demonstrated, and the mechanics and chemistry of adhesion are studied. The design principle will enable many hard polymers to form tough and stretchable adhesion between soft materials.

Preparation and Characterization of Chitosan–Alginate Polyelectrolyte Complexes Loaded with Antibacterial Thyme Oil Nanoemulsions

Biomedical industries are attempting to utilize natural materials, as they are bio-compatible, non-toxic, and show bioactive properties, like antimicrobial activity. In this study, natural polyelectrolyte complexed chitosan/alginate films (PECs) were prepared via a casting/solvent evaporation technique, and their characteristics and drug release properties were investigated. PEC films made with two different overall polymer contents, 0.4 and 1 w/v%, were loaded with thyme oil nanoemulsion as drug carrier. The structure of the films was studied by FTIR and optical and scanning electron microscopy. Prepared PEC films had good mechanical and water vapor permeability properties. Release of the thyme oil from the pH-sensitive PEC films (TM-PEC) was detected and followed by UV spectroscopy. The results indicated that the drug release rate of TM-PEC films was the fastest when the chitosan content was 1 %w/v, and various mathematical models were analyzed for investigating the drug release mechanism. Antibacterial tests were performed by counting the number of surviving gram-negative and gram-positive bacteria. The in vitro test indicated the limitation Escherichia coli (E. coli) and Staphylococcus aureus (S.aureus) growth in the presence of TM-PEC films. The MTT test showed more cell viability of the TM-PEC film in comparison with that of the PEC film without TM. Based on the measured physical and antibacterial properties, the chitosan–alginate PEC films loaded with antibacterial essential oils can be considered for biomedical applications, such as wound dressings or controlled release systems.

A dual-action chitosan-based nanogel system of triclosan and flurbiprofen for localised treatment of periodontitis

This study aimed to develop a dual action, namely anti-inflammatory and antimicrobial, nanogels (NG) for the treatment of periodontitis using triclosan (TCS) and flurbiprofen (FLB). Triclosan, an antimicrobial drug, was prepared as nanoparticles (NPs) using poly-ε-caprolactone (PCL), while flurbiprofen, an anti-inflammatory drug, was directly loaded in a chitosan (CS) based hydrogel. The entwinement of both NPs and hydrogel loaded systems resulted in the NG. The characterisation data confirmed that the developed formulation consists of nanosized spherical structures and displays pH-dependent swelling/erosion and temperature-responsiveness. Besides, the NG exhibited adequate bioadhesiveness using the chicken pouch model and displayed antibacterial activity through the agar plate method. An in-vivo study of the NG on experimental periodontitis (EP) rats confirmed the dual antibacterial and anti-inflammatory effects which revealed an excellent therapeutic outcome. In conclusion, a dual action NG was successfully developed and proved to have superior therapeutic effects in comparison to physical mixtures of the individual drugs.

Recent Progress of Polysaccharide‐Based Hydrogel Interfaces for Wound Healing and Tissue Engineering

Polysaccharide is an abundant and reproducible natural material that is biocompatible and biodegradable. Polysaccharide and its derivatives also possess distinctive properties such as hydrophilicity, mechanical stability, as well as tunable functionality. Polysaccharide‐based hydrogels can be constructed via the physical and/or chemical crosslinking of polysaccharide derivatives with different functional molecules, as porous network structures or nanofibrillar structures. This review discusses the biomedical applications of polysaccharide‐based hydrogels containing native polysaccharides, polysaccharide derivatives, and polysaccharide‐composite hydrogels. Recent works on the fabrication, physical properties, advanced engineering, biomedical applications of cellulose‐, chitosan‐, alginate‐, and starch‐based hydrogels are also elaborated. Such porous swelling scaffolds exhibit great advantages at the interface of a negative pressure system such as wound dressing. In addition, the authors also discuss and summarize the exemplary research works of these hydrogels in the applications of drug release, wound dressing, and tissue engineering. Finally, challenges and future perspectives about the development of polysaccharide‐based hydrogels are discussed.

Chitosan/glyphosate formulation as a potential, environmental friendly herbicide with prolonged activity

Although there are many reports on the dangers posed by glyphosate, this herbicide is still one of the most popular and widely used total weed killers. Therefore, great effort should be made to minimize exposure to this herbicide and limit its losses into the environment. The aim of this study was to prepare a new formulation consisted of various molecular weight chitosans with glyphosate and their evaluation toward active substance release, phytotoxicity, and preliminary herbicidal efficiency. The phytotoxicity study of the obtained chitosan/glyphosate formulations was determined based on the Organisation for Economic Co-operation and Development 208 guideline. Among all tested formulations evaluated for phytotoxicity, that containing the highest molecular weight of chitosan was found to be the least toxic, showing simultaneously the most effective herbicidal activity against selected weeds. The release rate of glyphosate from the obtained formulations was dependent on the molecular weight and viscosity of chitosan.

Conversion of Chitin to Defined Chitosan Oligomers: Current Status and Future Prospects

Chitin is an abundant polysaccharide primarily produced as an industrial waste stream during the processing of crustaceans. Despite the limited applications of chitin, there is interest from the medical, agrochemical, food and cosmetic industries because it can be converted into chitosan and partially acetylated chitosan oligomers (COS). These molecules have various useful properties, including antimicrobial and anti-inflammatory activities. The chemical production of COS is environmentally hazardous and it is difficult to control the degree of polymerization and acetylation. These issues can be addressed by using specific enzymes, particularly chitinases, chitosanases and chitin deacetylases, which yield better-defined chitosan and COS mixtures. In this review, we summarize recent chemical and enzymatic approaches for the production of chitosan and COS. We also discuss a design-of-experiments approach for process optimization that could help to enhance enzymatic processes in terms of product yield and product characteristics. This may allow the production of novel COS structures with unique functional properties to further expand the applications of these diverse bioactive molecules.

An injectable self-healing hydrogel-cellulose nanocrystals conjugate with excellent mechanical strength and good biocompatibility

In this work, a novel strategy for the construction of injectable self-healing nanocomposite (NC) hydrogels dominated by reversible boronic ester bonds was demonstrated. Specifically, NC hydrogels were constructed by the solution-mixing of N,N-dimethylacrylamide-stat-3-acrylamidophenylboronicacid statistical copolymers (PDMA-stat-PAPBA) and poly(glycerolmonomethacrylate) (PGMA) chains grafted cellulose nanocrystals (CNC-g-PGMA). Rheology analysis indicated the as-constructed NC hydrogel displayed about 7-fold increase in the storage modulus with a low CNCs loading level of 1.43 wt% in comparison with PGMA/PDMA-stat-PAPBA hydrogel without CNCs. Furthermore, the mechanical strength of the CNC-g-PGMA/PDMA-stat-PAPBA hydrogel was far superior to that of its PGMA/PDMA-stat-PAPBA/CNCs hydrogel counterpart, in which PGMA chains were not covalently grafted on the surfaces of CNCs. Due to reversible boronic ester bonds cross-linking networks, CNC-g-PGMA/PDMA-stat-PAPBA NC hydrogel exhibited excellent self-healing and injectable properties as well as pH/glucose responsive sol-gel transitions. Good biocompatibility was also demonstrated through in vitro cytotoxicity tests.

A novel iron-conjugated acid-modified chitosan derivatives as an oral phosphate binding agent to improve phosphorus adsorption efficacy in vitro and in vivo, synthesis and their characterization

Current phosphate binders used for hyperphosphatemia treatment need large daily dose which make patients' compliance worse and the therapeutic efficacy may not conform the expectation. In this study, three polyacid modified iron-based chitosan derivatives were developed as an oral phosphate binding agent to improve phosphorus adsorption efficacy. The result showed that modification of chitosan by citric acid (CA) could facilitate the conjugation of iron by two folds (272.0 ± 12.1-315.3 ± 20.5 mg Fe/g vs. 141.0 ± 4.9-156.5 ± 8.3 mg Fe/g). All of these iron-based acid-modified chitosan had acceptable safety with cell viability >75% in the concentration up to 250 μg/mL. The stability in terms of iron release in pH 1.0 for 2 h was in the order of DPCS-NAc-CA-Fe (8.9 ± 2.3%) < DPCS-CA-Fe (19.1 ± 4.1%) < DADPCS-CA-Fe (24.6 ± 2.6%) indicating DPCS-NAc-CA-Fe was the most stable one. These iron-based acid-modified chitosan derivatives efficiently adsorbed 255.7 ± 11.3-271.2 ± 19.3 mg of phosphate especially in simulated gastro pH 1.0 in vitro. Furthermore, oral administration of DPCS-NAc-CA-Fe significantly lowered serum phosphorus level from 5.82 ± 0.45 mg/dL to 4.84 ± 0.56 mg/dL (p < 0.01) at 0.25% low feeding dose for 3 weeks without losing of weight, appetite, and activity of Wistar rats.

Theranostic biocomposite scaffold membrane

Acute and chronic wounds affect millions and are associated with billions of dollars in healthcare costs. The use of healing markers, biochemical cues from biocompatible matrices and materials, and their correlation with wound healing has the potential to generate valuable diagnostic, prognostic, and therapeutic information. In this study, we developed a collagen-dextran oxygen-sensing biocomposite scaffold membrane in which a phosphorescent oxygen sensor was incorporated to monitor physiological oxygen using in vivo phosphorescence imaging in a preclinical mouse model of wound healing. The oxygen-sensing biocomposite scaffold membrane enabled the noninvasive and longitudinal monitoring of oxygenation changes in vivo in an approach compatible with commercially available preclinical in vivo imaging system instruments. This study provides a new and novel capability where a biocomposite material can serve as a biocompatible, biodegradable theranostic platform to promote and assess tissue oxygenation during wound healing.

Carbohydrate-based nanomaterials for biomedical applications

Carbohydrates are abundant biomolecules, with a strong tendency to form supramolecular networks. A host of carbohydrate-based nanomaterials have been exploited for biomedical applications. These structures are based on simple mono- or disaccharides, as well as on complex, polymeric systems. Chemical modifications serve to tune the shapes and properties of these materials. In particular, carbohydrate-based nanoparticles and nanogels were used for drug delivery, imaging, and tissue engineering applications. Due to the reversible nature of the assembly, often based on a combination of hydrogen bonding and hydrophobic interactions, carbohydrate-based materials are valuable substrates for the creations of responsive systems. Herein, we review the current research on carbohydrate-based nanomaterials, with a particular focus on carbohydrate assembly. We will discuss how these systems are formed and how their properties are tuned. Particular emphasis will be placed on the use of carbohydrates for biomedical applications. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

The Use of Lanthanum Ions and Chitosan for Boron Elimination from Aqueous Solutions

Boron is an essential element for plants and living organisms; however, it can be harmful if its concentration in the environment is too high. In this paper, lanthanum(III) ions were introduced to the structure of chitosan via an encapsulation technique and the obtained hydrogel (La-CTS) was used for the elimination of the excess of B(III) from modelling solutions. The reaction between boric acid and hydroxyl groups bound to the lanthanum coordinated by chitosan active centres was the preponderant mechanism of the bio-adsorption removal process. The results demonstrated that La-CTS removed boric acid from the aqueous solution more efficiently than either lanthanum hydroxide or native chitosan hydrogel, respectively. When the initial boron concentration was 100 mg/dm³, the maximum adsorption capacity of 11.1 ± 0.3 mg/g was achieved at pH 5 and the adsorption time of 24 h. The successful introduction of La(III) ions to the chitosan backbone was confirmed by Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy, Fourier-Transform Infrared Spectroscopy, X-Ray Diffraction, X-ray Photoelectron Spectroscopy, and Inductively Coupled Plasma Optical Emission Spectroscopy. Due to its high-performance boron adsorption-desorption cycle and convenient form, La-CTS seems to be a promising bio-adsorbent for water treatment.

A review on cellulose nanocrystals as promising biocompounds for the synthesis of nanocomposite hydrogels

Hydrogels are hydrophilic cross-linked polymer networks formed via the simple reaction of one or more monomers with the ability to retain a significant extent of water. Owing to an increased demand for environmentally friendly, biodegradable, and biocompatible products, cellulose nanocrystals (CNCs) with high hydrophilicity have emerged as a promising sustainable material for the formation of hydrogels. The cytocompatibility, swellability, and non-toxicity make CNC hydrogels of great interest in biomedical, biosensing, and wastewater treatment applications. There has been a considerable progress in the research of CNC hydrogels, as the number of scientific publications has exponentially increased (>600%) in the last five years. In this paper, recent progress in CNC hydrogels with particular emphasis on design, materials, and fabrication techniques to control hydrogel architecture, and advanced applications are discussed.

pH and folic acid dual responsive polysaccharide nanospheres used for nuclear targeted cancer chemotherapy

Ideal nanoscale drug delivery system (DDS) should be biocompatible, having targeted recognition and controlled release properties. In this work, monodispersed, doxorubicin (Dox) loaded chitosan (Cts) nanospheres functionalized by mesoporous SiO₂ and folic acid (FA) were prepared, briefly named as DCSF NSs. The prepared raspberry-like DCSF NSs had an average size of 440 nm and drug loading efficiency (DLE) of 42.61%. The drug release results confirmed that the release of Dox could be controlled by pH change. Cell apoptosis results indicated that the obtained DCSF NSs could kill 90% of MCF-7 cells in 48 h. Confocal laser scanning microscopy (CLSM) results further revealed that folic acid could mediate the cellular uptake of DCSF NSs. These results demonstrated that the obtained DCSF NSs were pH-responsive, folic acid-triggered nuclear targeted, which can be used as ideal DDS for tumor chemotherapy.

Defective Black Nano-Titania Thermogels for Cutaneous Tumor-Induced Therapy and Healing

Current challenges in cutaneous tumor therapy are healing the skin wounds resulting from surgical resection and eliminating possible residual tumor cells to prevent recurrence. To address this issue, bifunctional biomaterials equipped with effective tumor therapeutic capacity for skin cancers and simultaneous tissue regenerative ability for wound closure are highly recommended. Herein, we report an injectable thermosensitive hydrogel (named BT-CTS thermogel) with the integration of nanosized black titania (B-TiO_{2- x}, ∼50 nm) nanoparticles into a chitosan (CTS) matrix. The B-TiO_{2- x} nanocrystal exhibits a crystalline/amorphous core-shell structure with abundant oxygen vacancies, which endows the BT-CTS thermogels with simultaneous photothermal therapy (PTT) and photodynamic therapy (PDT) effects under single-wavelength near-infrared laser irradiation, leading to an excellent therapeutic effect on skin tumors in vitro and in vivo. Moreover, the BT-CTS thermogel not only supports the adhesion, proliferation, and migration of normal skin cells but also facilitates skin tissue regeneration in a murine chronic wound model. Therefore, such BT-CTS thermogels with easy injectability, excellent thermostability, and simultaneous PTT and PDT efficacy as well as tissue regenerative activity offers a promising pathway for the healing of cutaneous tumor-induced wounds.

Comparison of high and low molecular weight chitosan as in-vitro boosting agent for photodynamic therapy against Helicobacter pylori using methylene blue and endoscopic light

BACKGROUND

We reported in a previous study that photodynamic therapy (PDT) of Helicobacter pylori(H. pylori) could potentiate bactericidal effect by adding chitosan. As a next step, we compared the bactericidal effects of low molecular weight (LMW) combined with Photodynamic Therapy to high molecular weight (HMW) chitosan.

METHOD

To perform PDT to kill H. pylori, we used endoscopic light as light source, methylene blue (MB) as a photosensitizer and chitosan (310-375, 50-190 kDa). We evaluated bacterial removal rate and its membrane damage by ethidium bromide monoazide PCR method (EMA q-PCR). 8-oxo-2'-dexoyguanosine by ELISA was measured for oxidative stress.

RESULTS

At a chitosan concentration of ≤0.05%, the killing effect did not differ between the two molecular weights, and 100% bacterial removal rate was observed at a light energy ≥ 6.23 mJ/cm² powers under 0.02% MB. After 15 min irradiation, LMW chitosan with high concentration of MB (0.004%) showed highest killing effects, which were consistent with the results of EMA q-PCR but not with the level of 8-OHdG. Bactericidal effects of LMW chitosan plus PDT using 0.002 and 0.004% MB for 15 min irradiation were significantly higher than those using HMW chitosan plus PDT.

CONCLUSION

We found that PDT using methylene blue with LMW chitosan to kill H. pylori exerted greater bactericidal effects through bacterial membrane damage than PDT with HMW chitosan. These results suggest that it would be better to choose LMW chitosan to enhance the effect of PDT for clinical application, even at a very low concentration of PS.

Molecular Mechanisms of Chitosan Interactions with Fungi and Plants

Chitosan is a versatile compound with multiple biotechnological applications. This polymer inhibits clinically important human fungal pathogens under the same carbon and nitrogen status as in blood. Chitosan permeabilises their high-fluidity plasma membrane and increases production of intracellular oxygen species (ROS). Conversely, chitosan is compatible with mammalian cell lines as well as with biocontrol fungi (BCF). BCF resistant to chitosan have low-fluidity membranes and high glucan/chitin ratios in their cell walls. Recent studies illustrate molecular and physiological basis of chitosan-root interactions. Chitosan induces auxin accumulation in Arabidopsis roots. This polymer causes overexpression of tryptophan-dependent auxin biosynthesis pathway. It also blocks auxin translocation in roots. Chitosan is a plant defense modulator. Endophytes and fungal pathogens evade plant immunity converting chitin into chitosan. LysM effectors shield chitin and protect fungal cell walls from plant chitinases. These enzymes together with fungal chitin deacetylases, chitosanases and effectors play determinant roles during fungal colonization of plants. This review describes chitosan mode of action (cell and gene targets) in fungi and plants. This knowledge will help to develop chitosan for agrobiotechnological and medical applications.

Folate-Functionalized Thiomeric Nanoparticles for Enhanced Docetaxel Cytotoxicity and Improved Oral Bioavailability

To achieve remotely directed delivery of anticancer drugs, surface-decorated nanoparticles with ligands are reported. In this study, folic acid- and thiol-decorated chitosan nanoparticles loaded with docetaxel (DTX-NPs) were prepared for enhanced cellular internalization in cancer cells and improved oral absorption. The DTX-NPs were explored through in vitro and in vivo parameters for various parameters. The DTX-NPs were found to be monodisperse nanoparticles with an average particle size of 158.50 ± 0.36 nm, a polydispersity index of 0.36 ± 0.0, a zeta potential of + 18.30 ± 2.52 mV, and an encapsulation efficiency of 71.47 ± 5.62%. The drug release from DTX-NPs followed the Korsmeyer-Peppas model with about 78% of drug release in 12 h. In in vitro cytotoxicity studies against folate receptor, positive MDA-MBB-231 cancerous cells showed improved cytotoxicity with IC₅₀ of 0.58 μg/mL, which is significantly lower as compared to docetaxel (DTX). Ex vivo permeation enhancement showed an efflux ratio of 0.99 indicating successful transport across the intestine. Oral bioavailability was significantly improved as C_max and AUC were higher than DTX suspension. Overall, the results suggest that DTX-NPs can be explored as a promising carrier for oral drug delivery.

Cellulose nanocrystals and cellulose nanofibrils based hydrogels for biomedical applications

The production of cellulose nanomaterials from lignocellulosic biomass opens an opportunity for the development and application of new materials in nanotechnology. Over the last decade, cellulose nanomaterials based hydrogels have emerged as promising materials in the field of biomedical applications due to their low toxicity, biocompatibility, biodegradability, as well as excellent mechanical stability. In this review, recent progress on the preparation of cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) based hydrogels and their biomedical applications is summarized and discussed based on the analyses of the latest studies (especially for the reports in the past five years). We begin with a brief introduction of the differences in preparation methods and properties of two main types of cellulose nanomaterials: CNCs and CNFs isolated from lignocellulosic biomass. Then, various processes for the fabrication of CNCs based hydrogels and CNFs based hydrogels were elaborated, respectively, with the focus on some new methods (e.g. 3D printing). Furthermore, a number of biomedical applications of CNCs and CNFs based hydrogels, including drug delivery, wound dressings and tissue engineering scaffolds were highlighted. Finally, the prospects and ongoing challenges of CNCs and CNFs based hydrogels for biomedical applications were summarized. This work demonstrated that the CNCs and CNFs based hydrogels have great promise in a wide range of biomedical applications in the future.

Non-thermal plasma assisted surface nano-textured carboxymethyl guar gum/chitosan hydrogels for biomedical applications

Smart hydrogels comprising carboxymethyl guar gum and chitosan (CMGG/CS) have been fabricated using tetraethyl orthosilicate as the crosslinker. To render the hydrogels an improved biological efficacy, non-thermal plasma assisted surface modification have been performed using Ar, O2 and a mixture of Ar and O2 gases. Enhanced surface wettability was witnessed post-plasma treatment. AFM analyses revealed the topographical changes of the hydrogels at the nano-scale level without any adverse effect on their bulk physical structure. The hydrogels exhibited pH-responsive swelling with maximum swelling in neutral pH. The release of diclofenac sodium from the hydrogels confirmed their potential towards colon-targeted drug delivery. Excellent biofilm eradication features against E. coli was demonstrated by the hydrogels. Hemolytic assay on human RBCs affirmed their hemocompatibility. Moreover, the hydrogels were found to be remarkably biodegradable. Thus, non-thermal plasma assisted surface nano-textured CMGG/CS hydrogels can be efficaciously explored for their diverse applications in biomedicine.

Fabrication and Characterization of Core-Shell Electrospun Fibrous Mats Containing Medicinal Herbs for Wound Healing and Skin Tissue Engineering

Nanofibrous structures mimicking the native extracellular matrix have attracted considerable attention for biomedical applications. The present study aims to design and produce drug-eluting core-shell fibrous scaffolds for wound healing and skin tissue engineering. Aloe vera extracts were encapsulated inside polymer fibers containing chitosan, polycaprolactone, and keratin using the co-axial electrospinning technique. Electron microscopic studies show that continuous and uniform fibers with an average diameter of 209 ± 47 nm were successfully fabricated. The fibers have a core-shell structure with a shell thickness of about 90 nm, as confirmed by transmission electron microscopy. By employing Fourier-transform infrared spectroscopy, the characteristic peaks of Aloe vera were detected, which indicate successful incorporation of this natural herb into the polymeric fibers. Tensile testing and hydrophilicity measurements indicated an ultimate strength of 5.3 MPa (elongation of 0.63%) and water contact angle of 89°. In-vitro biological assay revealed increased cellular growth and adhesion with the presence of Aloe vera without any cytotoxic effects. The prepared core-shell fibrous mats containing medical herbs have a great potential for wound healing applications.

Hydrogels with multiple clickable anchor points: synthesis and characterization of poly(furfuryl glycidyl ether)-block-poly(ethylene glycol) macromonomers

Functional polyacrylamide hydrogels containing multiple furfuryl anchor points for Diels–Alder reactions were prepared employing new macromonomers.

Tetracycline hydrochloride loaded citric acid functionalized chitosan hydrogel for wound healing

Citric modified chitosan (CC) hydrogel containing antibacterial drugs is developed by the freezing and thawing treatment method. The SEM image of the CC hydrogel revealed a porous structure. The rheological properties, porosity, swelling rate, water uptake, tensile properties and in vitro degradation were found to be tunable via CC concentration. To enhance antibacterial properties, tetracycline hydrochloride (TH) representing the drug model, was integrated into the CC hydrogel. The cumulative release of drug was also tunable via CC concentration. The drug loaded CC hydrogel showed enhanced antimicrobial activity against E. coli and S. aureus. In animal tests, it was found the TH loaded CC hydrogel accelerated the healing of the wounds created on rats. These results suggest that the drug loaded CC hydrogel has a promising future in wound healing as a wound dressing.

Citric modified chitosan (CC) hydrogel containing antibacterial drug for wound healing applications.

Remodeling of inherent antimicrobial nanofiber dressings with melamine-modified fibroin into neoskin

A melamine-modified fibroin was synthesized and fabricated into electrospun nanofiber films with broad-spectrum antimicrobial activity, sustained water retention, and fast reepithelialization and revascularization.

Tunable antibiotic delivery from gellan hydrogels

Hydrogels are used extensively in wound management. Many wounds are highly susceptible to infection and hydrogels can provide localized antibacterial delivery to treat and prevent this infection. There are several key considerations in designing antibacterial hydrogels for wound therapy, including preserving activity of encapsulated antibacterial agents, controlling drug release timescales and concentrations, and having the ability to conform to various wound configurations. In this work, we have used gellan, a U.S. Food and Drug Administration approved food additive, to develop antibiotic loaded hydrogels focusing on these criteria. These hydrogels were formed to exhibit a range of mechanical properties, which were investigated using oscillatory rheology. We denoted hydrogels formed using 1% w/v gellan and 1 mM CaCl₂"ointment" hydrogels and those formed using 4% w/v gellan and 7 mM CaCl₂"sheet" hydrogels. Vancomycin, a broad-spectrum antibiotic against Gram-positive bacteria, was encapsulated in these hydrogels both directly and/or in graphitized carbon black nanoparticles (CNPs). We found that vancomycin released from both sheet and ointment hydrogels at therapeutically effective concentrations over 9 days with CNPs and 6 days without CNPs. Applying the Ritger-Peppas and Peppas-Sahlin semi-empirical drug release models to sheet hydrogels, we determined that Fickian diffusion dominates release while case II relaxation also has a small contribution. The sheet hydrogels exhibited a larger overall release of the drug (83.6 ± 1.6% compared to 67.0 ± 2.6% for ointments), which was attributed to the larger swelling resulting from osmotic pressure differences between the hydrogel formulations and the release buffer. We also suggest that final drug release amounts are influenced by intermolecular interactions between vancomycin and gellan, which were observed via quartz crystal microbalance with dissipation monitoring. Lastly, we examined the potential for future in vivo translation. We demonstrated in vitro growth inhibition of Staphylococcus aureus (S. aureus) and methicillin-resistant S. aureus in the presence of these hydrogels, demonstrating that vancomycin activity is preserved upon encapsulation. We also showed that these hydrogels are non-toxic to important wound healing cells including fibroblasts and mesenchymal stem cells.