Possibility of wound dressing using poly(L-leucine)/poly(ethylene glycol)/poly(L-leucine) triblock copolymer

Rational Design of Intelligent and Multifunctional Dressing to Promote Acute/Chronic Wound Healing

Currently, the clinic's treatment of acute/chronic wounds is still unsatisfactory due to the lack of functional and appropriate wound dressings. Intelligent and multifunctional dressings are considered the most advanced wound treatment modalities. It is essential to design and develop wound dressings with required functions according to the wound microenvironment in the clinical treatment. This work summarizes microenvironment characteristics of various common wounds, such as acute wound, diabetic wound, burns wound, scalded wound, mucosal wound, and ulcers wound. Furthermore, the factors of transformation from acute wounds to chronic wounds were analyzed. Then we focused on summarizing how researchers fully and thoroughly combined the complex microenvironment with modern advanced technology to ensure the usability and value of the dressing, such as photothermal-sensitive dressings, microenvironment dressing (pH-sensitive dressings, ROS-sensitive dressings, and osmotic pressure dressings), hemostatic dressing, guiding tissue regeneration dressing, microneedle dressings, and 3D/4D printing dressings. Finally, the revolutionary development of wound dressings and how to transform the existing advanced functional dressings into clinical needs as soon as possible have carried out a reasonable and meaningful outlook.

Antibacterial biomaterials for skin wound dressing

Bacterial infection and the ever-increasing bacterial resistance have imposed severe threat to human health. And bacterial contamination could significantly menace the wound healing process. Considering the sophisticated wound healing process, novel strategies for skin tissue engineering are focused on the integration of bioactive ingredients, antibacterial agents included, into biomaterials with different morphologies to improve cell behaviors and promote wound healing. However, a comprehensive review on anti-bacterial wound dressing to enhance wound healing has not been reported. In this review, various antibacterial biomaterials as wound dressings will be discussed. Different kinds of antibacterial agents, including antibiotics, nanoparticles (metal and metallic oxides, light-induced antibacterial agents), cationic organic agents, and others, and their recent advances are summarized. Biomaterial selection and fabrication of biomaterials with different structures and forms, including films, hydrogel, electrospun nanofibers, sponge, foam and three-dimension (3D) printed scaffold for skin regeneration, are elaborated discussed. Current challenges and the future perspectives are presented in this multidisciplinary field. We envision that this review will provide a general insight to the elegant design and further refinement of wound dressing.

Antimicrobial Peptides: The Promising Therapeutics for Cutaneous Wound Healing

Chronic wound infections have caused an increasing number of deaths and economic burden, which necessitates wound treatment options. Hitherto, the development of functional wound dressings has achieved reasonable progress. Antibacterial agents, growth factors, and miRNAs are incorporated in different wound dressings to treat various types of wounds. As an effective antimicrobial agent and emerging wound healing therapeutic, antimicrobial peptides (AMPs) have attracted significant attention. The present study focuses on the application of AMPs in wound healing and discusses the types, properties and formulation strategies of AMPs used for wound healing. In addition, the clinical trial and the current status of studies on "antimicrobial peptides and wound healing" are elaborated through bibliometrics. Also, the challenges and opportunities for further development and utilization of AMP formulations in wound healing are discussed.

Classification and Production of Polymeric Foams among the Systems for Wound Treatment

This work represents an overview on types of wounds according to their definition, classification and dressing treatments. Natural and synthetic polymeric wound dressings types have been analyzed, providing a historical overview, from ancient to modern times. Currently, there is a wide choice of materials for the treatment of wounds, such as hydrocolloids, polyurethane and alginate patches, wafers, hydrogels and semi-permeable film dressings. These systems are often loaded with drugs such as antibiotics for the simultaneous delivery of drugs to prevent or cure infections caused by the exposition of blood vessel to open air. Among the presented techniques, a focus on foams has been provided, describing the most diffused branded products and their chemical, physical, biological and mechanical properties. Conventional and high-pressure methods for the production of foams for wound dressing are also analyzed in this work, with a proposed comparison in terms of process steps, efficiency and removal of solvent residue. Case studies, in vivo tests and models have been reported to identify the real applications of the produced foams.

Comparison of the therapeutic efficacy of salicylic acid paste with a polyurethane wound dressing for the treatment of digital dermatitis lesions in dairy cows

There is little evidence of the efficacy of artificial polymers for controlling bovine digital dermatitis (BDD) as a major problem of intensive dairy productions worldwide. We therefore aimed to compare salicylic acid (SA)-based paste with a polyurethane (PU) wound dressing on a German Holstein dairy farm over a maximum 56-d period. On d 0, 109 ft with active BDD lesions from 109 cows were randomly assigned to two treatment groups: (1) SA group received a topical SA-containing paste and (2) PU group was treated with a PU wound dressing. Dressing changes were performed according to manufacturer's instructions until clinical cure (transition from active M1 or M2 to non-active M4 or healed M0 stages), whereby a clinical scoring of lesions was additionally conducted. Data from 100 ft could be analyzed (n_SA = 54; n_PU = 46). There was a significant reduction of the lesion score over time within each group (SA: d 0-d 14; PU: d 0-d 28, p < .05). Score differences between first (d 0) and second (SA: d 7; PU: d 14) as well as between first and third (SA: d 14; PU: d 28) evaluation did not differ significantly (p > .05). The proportion of clinically cured cows was higher in SA than in PU on d 14 (96.3 vs. 32.6%) as well as on d 28 (100 vs. 54.3%) after initial treatment (p < .05). Analysis of survival to cure in a Cox regression model showed that hazard ratio (HR) was higher for SA with PU as baseline (HR: 6.324, 95% CI: 3.625-11.033, p < .05). However, while BDD scores at enrollment did not differ between treatments (p > .05), PU had a significantly lower final BDD score (p < .05). In conclusion, evidence on the efficacy of PU bandages to treat BDD lesions is provided and further studies on bacteriological cure as well as recurrence rates are needed.

Self-assembled PEG-poly(l-valine) hydrogels as promising 3D cell culture scaffolds

Self-assembled polypeptide aggregates have shown great promise in biomedical fields including drug delivery, tissue regeneration and regenerative medicine. In this study, we report self-assembled hydrogels based on mPEG-block-poly(l-valine) (PEV) copolymers. PEV copolymers with varying poly(l-valine) chain lengths were prepared by the ring-opening polymerization of N-carboxy anhydrides of l-valine using mPEG-NH₂ as the initiator. ¹H NMR and GPC confirmed their well-defined chemical structures. FT-IR analysis and DSC curves indicated the combined α-helix and β-sheet secondary polypeptide conformation and the PEG crystallization microphase in bulk solid state, respectively. Moreover, the poly(l-valine) block restricted the crystallization of PEG segment. DLS, TEM and circular dichroism spectra were employed to study the self-assembly profiles of PEV copolymers in aqueous solution. The results manifested that in diluted solution, PEV copolymers showed a combination of typical β-sheet and α-helical polypeptide structures and self-assembled into nanostructures with diverse morphologies and sizes. For concentrated PEV solutions, clear hydrogel phases were observed and dynamic rheological analyses demonstrated that the hydrogel modulus was sensitive to the polypeptide length, angular frequency, shear strain and temperature. The hydrogel formation was possibly dominated by the physical aggregation of PEV nanoassemblies as well as driven by the formation of particular polypeptide secondary structures. Human fibroblast NIH/3T3 cells were encapsulated and cultured within the hydrogel scaffolds. The encapsulated cells exhibited high viability, suggesting that PEV hydrogels have excellent cytocompatibility and could be used as three-dimensional (3D) cell culture matrices. Collectively, self-assembled PEGylated poly(l-valine) conjugate hydrogels represented a new kind of biomaterial scaffold in biomedical fields including but not limited to 3D cell culture.

Physical, morphological, and wound healing properties of a polyurethane foam-film dressing

Background

We investigated the physicochemical properties of Medifoam® N and its wound healing performance compared to other commercially available polyurethane (PU) foam dressing in vitro and in vivo to gain insight in their clinical performance.

Methods

Wound contact layer and cross-section of eleven polyurethane foam dressings were assessed with field-emission scanning electron microscope. Thickness, density, tensile strength, elongation, moisture-vapor transmission rate (MVTR), retention and absorptivity were measured to compare physical properties. Phosphate-buffered saline (PBS) solution absorption patterns were compared. An animal model for wound-healing was applied to validate in vitro findings.

Results

Among eleven tested foam dressings, Medifoam® N has the smallest pore and cell sizes with excellent uniformity, i.e. it has 25 ~ 75 μm on the wound contact layer and 100 ~ 350 μm in the cross-section while other dressings have a larger pose size with larger variability. Compared to other PU foams, Medifoam® N also has moderate thickness, density, tensile strength, elongation and MVTR. Furthermore, it has excellent fluid absorption and retention capacity. These intrinsic properties of Medifoam® N contributed to improve fluid absorption patterns, i.e. other dressing material flawed out PBS solution on the dressings while Medifoam® N retained all the tested solutions. In animal wound-healing study, Medifoam® N treated animals showed excellent angiogenesis and collagen deposition even though epithelial recovery rate was not significantly different to other dressings.

Conclusions

Medifoam® N has optimized physical properties and thus improved fluid absorption/retention capacity. Compared to other dressings, Medifoam® N showed excellent fluid absorption patterns and these characteristics contributed to improved wound healing and excellent angiogenic potential. We found that Medifoam® N showed the best results among the employed dressing samples.

Electronic supplementary material

The online version of this article (doi:10.1186/s40824-016-0063-5) contains supplementary material, which is available to authorized users.

Structural insights into the effect of cholinium-based ionic liquids on the critical micellization temperature of aqueous triblock copolymers

A symmetrical PEG–PPG–PEG triblock copolymer with 82.5% PEG as the hydrophilic end blocks, and PPG as the hydrophobic middle block, was chosen to study the effect of ionic liquids on the critical micellization temperature of block copolymers in aqueous solution.

Sustainable antimicrobial effect of silver sulfadiazine-loaded nanosheets on infection in a mouse model of partial-thickness burn injury

Partial-thickness burn injury has the potential for reepithelialization and heals within 3weeks. If the wound is infected by bacteria before reepithelization, however, the depth of disruption increases and the lesion easily progresses to the full-thickness dermal layers. In the treatment of partial-thickness burn injury, it is important to prevent the wound area from bacterial infection with an antimicrobial dressing. Here, we have tested the antimicrobial properties of polymeric ultra-thin films composed of poly(lactic acid) (termed "PLA nanosheets"), which have high flexibility, adhesive strength and transparency, and silver sulfadiazine (AgSD), which exhibits antimicrobial efficacy. The AgSD-loaded nanosheet released Ag(+) for more than 3days, and exerted antimicrobial efficacy against methicillin-resistant Staphylococcus aureus (MRSA) in an in vitro Kirby-Bauer test. By contrast, a cell viability assay indicated that the dose of AgSD used in the PLA nanosheets did not show significant cytotoxicity toward fibroblasts. In vivo evaluation using a mouse model of infection in a partial-thickness burn wound demonstrated that the nanosheet significantly reduced the number of MRSA bacteria on the lesion (more than 10(5)-fold) and suppressed the inflammatory reaction, thereby preventing a protracted wound healing process.

Development and characterization of an electrospun mat from Eri silk fibroin and PLA blends for wound dressing application

Eri silk fibroin blend with poly-l-lactic acid polymer and tetracycline hydrochloride were electrospun as nanofibrous mat and evaluated for properties required for skin contact layer of multilayer wound dressing systems.

Synthesis of a semi-interpenetrating polymer network as a bioactive curcumin film

This study focused on the synthesis and characterization of a natural polymeric system employing the interpenetrating polymer network (IPN) comprising curcumin as a bioactive. Biopolymers and actives such as chitosan, hypromellose, citric acid, genipin, and curcumin were used to develop an effective, biodegradable, and biocompatible film employed therapeutically as a wound healing platform. The semi-IPN films were investigated for their physicochemical, physicomechanical, and biological properties by quantification by FTIR, DSC, and Young's modulus. Following characterization, an optimum candidate formulation was produced whereby further in vitro and ex vivo studies were performed. Results revealed a burst release occurring at the first hour with 1.1 mg bioactive released when in contact with the dissolution medium and 2.23 mg due to bioactive permeation through the skin, thus suggesting that the lipophilic nature of skin greatly impacted the bioactive release rate. Furthermore, chemical and mechanical characterization and tensile strength analysis revealed that the degree of crosslinking and concentration of polymeric material used significantly influenced the properties of the film.

Silver- and sulfadiazine-loaded nanostructured silica materials as potential replacement of silver sulfadiazine

Sulfadiazine-loaded silver nanoporous silica carriers have similar antibacterial properties as silver sulfadiazine.

Gentamicin-loaded wound dressing with polyvinyl alcohol/dextran hydrogel: gel characterization and in vivo healing evaluation

To develop a gentamicin-loaded wound dressing, cross-linked hydrogel films were prepared with polyvinyl alcohol (PVA) and dextran using the freezing-thawing method. Their gel properties such as gel fraction, swelling, water vapor transmission test, morphology, tensile strength, and thermal property were investigated. In vitro protein adsorption test, in vivo wound healing test, and histopathology were performed. Dextran decreased the gel fraction, maximum strength, and thermal stability of hydrogels. However, it increased the swelling ability, water vapor transmission rate, elasticity, porosity, and protein adsorption. The drug gave a little positive effect on the gel properties of hydrogels. The gentamicin-loaded wound dressing composed of 2.5% PVA, 1.13% dextran, and 0.1% drug was more swellable, flexible, and elastic than that with only PVA because of its cross-linking interaction with PVA. In particular, it could provide an adequate level of moisture and build up the exudates on the wound area. From the in vivo wound healing and histological results, this gentamicin-loaded wound dressing enhanced the healing effect more compared to conventional product because of the potential healing effect of gentamicin. Thus, this gentamicin-loaded wound dressing would be used as a potential wound dressing with excellent forming and improved healing effect in wound care.

Wound healing evaluation of sodium fucidate-loaded polyvinylalcohol/sodium carboxymethylcellulose-based wound dressing

The cross-linked hydrogel films containing sodium fucidate were previously reported to be prepared polyvinyl alcohol (PVA) and sodium carboxymethylcellulose (Na-CMC) using the freeze-thawing method and their physicochemical property was investigated. For the development of novel sodium fucidate-loaded wound dressing, here its in vivo wound healing test and histopathology were performed compared with the conventional ointment product. In wound healing test, the sodium fucidate-loaded composed of 2.5% PVA, 1.125% Na-CMC and 0.2% drug showed faster healing of the wound made in rat dorsum than the hydrogel without drug, indicating the potential healing effect of sodium fucidate. Furthermore, from the histological examination, the healing effect of sodium fucidate-loaded hydrogel was greater than that of the conventional ointment product and hydrogel without drug, since it might gave an adequate level of moisture and build up the exudates on the wound area. Thus, the sodium fucidate-loaded wound dressing composed of 5% PVA, 1.125% Na-CMC and 0.2% drug is a potential wound dressing with excellent wound healing.

Multifunctional silane polymers for persistent surface derivatization and their antimicrobial properties

We demonstrate a versatile methodology combining both covalent surface anchoring and polymer cross-linking that is capable of forming long-lasting coatings on reactive and nonreactive surfaces. Polymers containing reactive methoxysilane groups form strong Si-O-Si links to oxide surfaces, thereby anchoring the polymer chains at multiple points. The interchain cross-linking of the methoxysilane groups provides additional durability to the coating and makes the coatings highly resistant to solvents. By tailoring the chemical structure of the polymer, we were able to control the surface energy (wetting) of a variety of surfaces over a wide range of water contact angles of 30-140 degrees . In addition, we synthesized covalently linked layer-by-layer polymeric assemblies from these novel methoxysilane polymers. Finally, antibacterial agents, such as silver bromide nanoparticles and triiodide ions, were introduced into these functional polymers to generate long-lasting and renewable antiseptic coatings on glass, metals, and textiles.

Evaluation of semi-interpenetrating polymer networks composed of chitosan and poloxamer for wound dressing application

We have elsewhere reported the work on the preparation of semi-interpenetrating polymer networks (SIPNs) composed of chitosan (CS) and poloxamer to improve the mechanical strength of CS sponge. This study focuses on evaluation of the CS/poloxamer SIPNs to intend for wound dressing application and the efficacy of dehydroepiandrosterone (DHEA)-loaded CS/poloxamer SIPNs in the wound model studies. The properties required for ideal wound dressing, such as equilibrium water content (EWC), water absorption (A(w)), water vapor transmission rate (WVTR), and evaporative water loss, were examined. The CS/poloxamer SIPNs were found to have a water content of 90% of their weight which could prevent the wound bed from accumulation of exudates and also have excellent water adsorption. The WVTR of CS/poloxamer SIPNs was found to be 2,508.2+/-65.7gm(-2)day(-1), indicating that the SIPNs can maintain a moist environment over wound bed in moderate to heavily exuding wound which enhances epithelial cell migration during the healing process. Also, the CS/poloxamer SIPNs in vitro assessment showed proper biodegradation and low cytotoxicity for wound dressing application. The wound healing efficacy of CS/poloxamer SIPNs as a wound dressing was evaluated on experimental full thickness wounds in a mouse model. It was found that the wounds covered with CS/poloxamer SIPNs or DHEA-loaded CS/poloxamer SIPNs were completely filled with new epithelium without any significant adverse reactions after 3 weeks. The results thus indicate that CS/poloxamer SIPNs could be employed in the future as potential wound dressing materials.

The endotoxin binding and antioxidative properties of ceramic granules

OBJECTIVE

To investigate the possible antimicrobial activities and the detoxification (endotoxin binding and free radical scavenging) properties of Cerdak.

METHOD

In order to measure the antimicrobial activity of Cerdak, microorganisms were separately inoculated into nutrient agar in the presence of Cerdak, and growth was observed over 48 hours. Cerdak was incubated with 4000EU/ml endotoxin, and the residual endotoxin was determined over 24 hours. The decrease in the colour of ABTS and DPPH (inorganic free radicals) in the presence of Cerdak was colourimetrically monitored as a measure of Cerdax's free radical scavenging ability. DNA was exposed to hydrogen peroxide and ultraviolet irradiation in the presence and absence of Cerdak. The DNA strand break was then observed through electrophoresis.

RESULTS

While Cerdak had little or no antibacterial activities, it demonstrated a high water and endotoxin-binding capacity. It also protected DNA from damage by reactive oxygen species.

CONCLUSION

The detoxification properties of Cerdak could contribute to its healing abilities.

Thermodynamic Confinement and α-Helix Persistence Length in Poly(γ-benzyl-l-glutamate)-b-poly(dimethyl siloxane)-b-poly(γ-benzyl-l-glutamate) Triblock Copolymers

The structure and the associated dynamics of a series of poly(gamma-benzyl-L-glutamate)-b-poly(dimethyl siloxane)-b-poly(gamma-benzyl-L-glutamate) (PBLG-b-PDMS-b-PBLG) triblock copolymers were investigated using small- and wide-angle X-ray scattering, NMR, transmission electron microscopy, and dielectric spectroscopy, respectively. The structural analysis revealed phase separation in the case of the longer blocks with defected alpha-helical segments embedded within the block copolymer nanodomains. The alpha-helical persistence length was found to depend on the degree of segregation; thermodynamic confinement and chain stretching results in the partial annihilation of helical defects.

The use of polymers for dermal and transdermal delivery

The use of polymers for skin preparations is manifold. Requirements of such polymers are dependent on the formulation types. The most applied polymers on skin belong to various classes, for example to cellulose derivatives, chitosan, carageenan, polyacrylates, polyvinylalcohol, polyvinylpyrrolidone and silicones. They are gelating agents, matrices in patches and wound dressings, anti-nucleants and penetration enhancers. Correlations between commercially available products and results of new scientific investigations are often difficult or not possible, because of the lack of comparative data especially for transdermal patches. Finally, two promising future trends of polymeric systems, gene delivery and tissue engineering, are discussed.

Synthesis and characterization of poly(L-alanine)-block-poly(ethylene glycol) monomethyl ether as amphiphilic biodegradable co-polymers

Di-block co-polymers of poly(L-alanine) with poly(ethylene glycol) monomethyl ether (MPEG) were synthesized as amphiphilic biodegradable co-polymers. The ring-opening polymerization of N-carboxy-L-alanine anhydride (NCA) in dichloromethane was initiated by amino-terminated poly(ethylene glycol) monomethyl ether (MPEG-NH2, M(n) = 2000) to afford poly(L-alanine)-block-MPEG. The weight ratio of two blocks in the co-polymers could be altered by adjusting the feeding ratio of NCA to MPEG-NH2. Their chemical structures were characterized on the basis of infrared spectrometry and nuclear magnetic resonance. According to circular dichroism measurement, the poly(L-alanine) chain on the co-polymers in an aqueous medium had a alpha-helix conformation. Two melting points from MPEG block and poly(L-alanine), respectively, could be observed in differential scanning calorimetry curves of the co-polymers, suggesting that a micro-domain phase separation appeared in their bulky states. The co-polymers could take up some water and the capacity was dependent on the ratio of poly(L-alanine) block to MPEG. Such co-polymers might be useful in drug-delivery systems and other biomedical applications.

An infection-preventing bilayered collagen membrane containing antibiotic-loaded hyaluronan microparticles: physical and biological properties

An infection-preventing bilayered membrane consisting of a dense and porous collagen membrane has been developed. The membrane was fabricated using a combined freeze-drying/air-drying method. Hyaluronan (HA) microparticles containing silver sulfadiazine (AgSD) were fabricated by gelling an HA solution with calcium chloride and were incorporated into collagen layers to allow the sustained release of AgSD. In vitro biodegradability of the membrane and the release of AgSD from the membrane could be controlled by cross-linking the membrane with ultraviolet (UV) irradiation. In a cytotoxicity test, cellular damage was minimized by the sustained release of AgSD from dressings. The antibacterial capacity of the material against Pseudomonas aeruginosa was investigated using the Bauer-Kirby disk diffusion test, and bacterial growth was found to be inhibited for 4 days. In vivo tests showed that the bilayered membrane was associated with greater tissue regeneration than a polymeric membrane and with no infection-related biological signs.

Laminin modified infection-preventing collagen membrane containing silver sulfadiazine-hyaluronan microparticles

The newly developed laminin modified infection-preventing collagen membrane consists of a 3 component laminate, comprising 2 outer collagen layers and a central laminin layer. The 2 outer collagen layers (dense and porous layers) were fabricated by air-drying and freeze drying, respectively, and the laminin layer was formed by a straightforward liquid coating method. In addition, hyaluronan based microparticles containing silver sulfadiazine (AgSD) were incorporated into the 2 collagen layers (AgSD content 50 microg/cm2). Laminin coated collagen surfaces did not promote fibroblast attachment but showed a retarded fibroblast proliferation rate and an increased rate of collagen synthesis versus pure collagen surfaces. In an animal study, a laminin coating on a nonmedicated collagen membrane significantly increased both wound size reduction and vessel proliferation 7 days after application versus polyurethane film. Interestingly, the laminin coated AgSD medicated collagen membrane demonstrated higher wound size reduction and vessel proliferation and lower inflammation than the polyurethane control, suggesting that the laminin AgSD medicated collagen membrane substantially improves dermal wound healing.

Galactose dialdehyde as potential protein cross-linker: proof of principle

Combined enzymatic oxidation of D-galactose by D-galactose oxidase [EC 1.1.3.9] in water, amination with butylamine, and oxalic acid catalyzed Amadori rearrangement in methanol yielded 1,6-bis(butylamino)-1,6-dideoxy-erythro-hexo-2,5-diulose, demonstrating how in situ formed galacto-hexodialdose can be used to cross-link protein residues. The various species formed during this three-step conversion are present as bicyclic structures in solution as established by 13C labeling and in situ NMR spectroscopy of the reaction mixtures. Using protein (gelatin) instead of butylamine, distinct Amadori product formation was observed using 99% enriched D-(1-(13)C)- and D-(2-(13)C)-galactose.