The preparation and characterization of chitosan wound dressings with different degrees of acetylation

Chitosan fibers have in recent years found applications in various fields such as antimicrobial textiles and wound dressings. In this study, chitosan fibers with different degrees of acetylation were prepared by controlling the ratio between the amount of acetic anhydride and the weight of the fibers during the acetylation process. The absorption and antimicrobial properties, as well as the dry and wet strength of nonwoven chitosan wound dressings with different degrees of acetylation were studied. Results showed that the partially acetylated chitosan wound dressing had a much higher absorption capacity than the original untreated chitosan samples, while there was a reduction in the wet strength and antimicrobial property for the partially acetylated chitosan nonwoven dressing. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Photoactive antimicrobial PVA hydrogel prepared by freeze‐thawing process for wound dressing

A freeze‐thawing process was employed to produce both rose bengal (RB)/polyvinyl alcohol (PVA) and benzophenone (BP)/PVA hydrogels, respectively. Results indicated that only RB incorporated PVA (RB/PVA) could form hydrogel after undergoing three cycles of freeze‐thawing process; One of the cycles should be conducted by freezing at ?15°C ± 3°C for 18 h followed by thawing at 25°C for 6 h. The structural features and functional properties of the RB/PVA hydrogel were investigated by FTIR, XRD, SEM evaluations, and photo‐induced antimicrobial functions were examined as well. Release of RB from the RB/PVA hydrogel was examined by UV‐Vis spectroscopy. The freeze‐thawed RB/PVA hydrogel showed antimicrobial abilities against both E. coli and S. aureus under the exposure to fluorescence light as well as UVA (365 nm) light. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The characterization of alginate wound dressings with different fiber and textile structures

Seven commercially available alginate wound dressings with different polymer, fiber, and nonwoven structures were characterized in this study. The performances of these dressings were compared in terms of their absorbency capacities, gel swelling ratios in water and normal saline, wicking of fluid, and dry and wet strengths. Results show that the absorbency and swelling ratios were strongly affected by the guluronate and mannuronate contents of the alginate, the calcium and sodium contents of the fibers, and the nonwoven structures of the dressing. The different types of alginate wound dressings also had significantly different dry and wet strength. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2516–2520, 2006     

In vitro efficacy and toxicology evaluation of silver nanoparticle‐loaded gelatin hydrogel pads as antibacterial wound dressings

The silver nanoparticle (nAg)‐loaded gelatin hydrogel pads were prepared from 10 wt % gelatin aqueous solution containing silver nitrate (AgNO₃) at 0.75, 1.0, 1.5, 2.0, or 2.5 wt % by solvent‐casting technique. These AgNO₃‐containing gelatin solutions, that had been aged for 15, 12, 8, 8, and 8 h, respectively, showed noticeable amounts of the as‐formed nAgs, the size of which increased with an increase in the AgNO₃ concentration (i.e., from 7.7 to 10.8 nm, on average). The hydrogels were crosslinked with a glutaraldehyde aqueous solution (50 wt %, at 1 μL mL^?1). At 24 h of submersion in phosphate buffer saline (PBS) or simulated body fluid buffer (SBF) solution, about 40.5–56.4% or 44.4–79.6% of the as‐loaded amounts of silver was released. Based on the colony count method, these nAg‐loaded hydrogels were effective against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, with at least about 99.7% of bacterial growth inhibition. Unless they had been treated with a sodium metabisulfite aqueous solution, these hydrogels were proven, based on the indirect cytotoxicity evaluation, to be toxic to human's normal skin fibroblasts. Lastly, only the hydrogels that contained AgNO₃ at 0.75 and 1.0 wt % were not detrimental to the skin cells that had been cultured directly on them. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Characterization of minocycline loaded chitosan/polyethylene glycol/glycerol blend films as antibacterial wound dressings

Wound care has been a challenging subject for medical teams and researchers. Bacterial infections are one of the most serious complications in injured skins that often affect healing process. Antibacterial wound dressings can be used to facilitate wound healing process. The purpose of this study is to fabricate chitosan (Chito)/polyethylene glycol (PEG) antibacterial wound dressing doped with minocycline, and to evaluate the influence of composition ratio on the blending properties of the films. To improve the mechanical properties of these films, we examined various amounts of glycerol as a plasticizer. Moreover, we investigated morphological and mechanical aspects, water uptake, degradation, water vapor transmission and wettability properties of the films prepared with various ratios of Chito/PEG/Gly. Assessment of mechanical properties revealed that film containing 80:20 ratio Chito/PEG with 40 PHR Gly content exhibits the highest ultimate tensile strength and elongation at break (9.74 MPa and 45.73% respectively). Furthermore, results demonstrated that upon increasing PEG and Gly contents, degradability and hydrophilicity of the films increased whereas water uptake decreased. Water vapor transmission rate of the films was close to the range of 530–1200 g/m²d, indicating that the as formed films are possible candidates for dressing low exudate wounds or burns. Minocycline loaded films exhibited a biphasic drug release profile and it was more effective on gram-positive bacteria than on gram-negative bacteria. The polymeric film with the highest amount of loaded drug (2%) exhibited insignificant cytotoxicity (88%) against normal fibroblast cell line.     

Design of moxifloxacin encapsulated network hydrogel wound dressings: Evaluation of polymer-drug,polymer-blood,and polymer-bio membrane interactions

It is an exploration of the inherent wound-healing tendency of Azadirachta indica gum (AIG) or neem gum polysaccharides to develop the hydrogel wound dressings with enhanced potential during wound management. Herein this research work, antibiotic moxifloxacin encapsulated AIG network copolymeric hydrogels were developed by functionalizing with carbapol and poly(acrylamide) [poly(AAm)] for better wound healing. The polymer-drug, polymer-blood, and polymer-bio membrane interactions were evaluated in biomedical properties. The copolymeric network structure was confirmed by scanning electron micrographs (SEMs), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), and ¹³C solid-state nuclear magnetic resonance (NMR) spectroscopy. The results confirmed sustained release of the moxifloxacin with diffusion by non-Fickian process and Korsmeyer–Peppas kinetic model in the phosphate buffer saline (PBS). These interactions inferred the blood-compatible (hemolytic index 3.41 ± 0.70%) and mucoadhesive nature (polymer-biomembrane detachment force 0.09 ± 0.01 mN) of hydrogel dressing. The per gram of hydrogel dressings absorbed 10.22 ± 0.23 g of simulated wound fluid which is very useful to maintain moist wound environment for better wound healing. All these interactions and properties indicated the suitability of the hydrogel material for wound dressing applications for better wound care.     

Preparation of antimicrobial poly(ϵ‐caprolactone) electrospun nanofibers containing silver‐loaded zirconium phosphate nanoparticles

Antimicrobial nanofibers of poly(?‐caprolactone) (PCL) were prepared by electrospinning of a PCL solution with small amounts of silver‐loaded zirconium phosphate nanoparticles (nanoAgZ) for potential use in wound dressing applications. The electrospun nanoAgZ‐containing PCL nanofibers were characterized using field emission scanning electron microscopy, energy dispersive X‐ray spectrum (EDX), X‐ray diffraction analysis (XRD), antimicrobial tests, and biocompatibility tests. The SEM, EDX, and XRD investigations of the electrospun fibers confirmed that silver‐containing nanoparticles were incorporated and well dispersed in smooth and beadless PCL nanofibers. The results of the antimicrobial tests showed that these fibers have maintained the strong killing abilities of Ag⁺ existed in the nanoAgZ against the tested bacteria strains and discoloration has not been observed for the nanofibers. To test the biocompatibility of nanofibers as potential wound dressings, primary human dermal fibroblasts (HDFs) were cultured on the nanofibrous mats. The cultured cells were evaluated in terms of cell proliferation and morphology. The results indicated that the cells attached and proliferated as continuous layers on the nanoAgZ‐containing nanofibers and maintained the healthy morphology of HDFs. The earlier results suggested that nanoAgZ‐containing fibers may be expected to be a novel material for potential wound dressing applications because of the significant bacteriostatic activities and good biocompatibility. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation and characterization of ciprofloxacin‐loaded alginate/chitosan sponge as a wound dressing material

The aim of this study is preparation and characterization of alginate/chitosan sponges including a model antibiotic (i.e., ciprofloxacin) to use in wound and/or burn treatment. Sponges were prepared firstly by the gelation of sodium alginate followed by lyophilization, crosslinking with calcium chloride, and finally coating with chitosan. Sponges were characterized with respect to morphology, water uptake, in vitro drug release behavior, and antimicrobial activity. Investigated and evaluated parameters in all of these studies were selected as the concentration of calcium chloride, alginate viscosity, drug content, and molecular weight of chitosan. Drug release and water uptake were found to be greatly influenced by these parameters. Water uptake and drug release rate were decreased by increasing the crosslinking density, chitosan molecular weight, and alginate viscosity. In the antimicrobial tests, it was obtained that the antimicrobial activity is directly proportional with the release rates and water uptake. Morphological studies showed a highly porous structure with interconnected pores. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1602–1609, 2006     

Herbal drug incorporated antibacterial nanofibrous mat fabricated by electrospinning: An excellent matrix for wound dressings

Nano‐components and nano‐systems for health care and medical applications are the focus of many research projects worldwide. Nanofibrous membranes are highly soft materials with high surface‐to‐volume ratios, and therefore can serve as excellent carriers for therapeutic agents that are antibacterial or accelerate wound healing. PCL/PVP Nanofiber mat containing chloroform: methanol (4:1) crude bark extract of Tecomella undulata, a medicinal plant widely known for its traditional medical applications including its wound healing ability, were prepared and evaluated for their antibacterial properties. With good drug stability and high drug‐loading efficacy, the incorporation of herbal extract in the polymer media did not appear to influence the morphology of the resulting fibers, as both the drug‐free and the drug‐loaded nanofibers remained unaltered, microscopically. Activity was tested against standard strains of Pseudomonas aeruginosa MTCC 2297, Staphylococcus aureus ATCC 933, Escherichia coli (IP‐406006). Extract loaded PCL/PVP nanofiber mat were able to inhibit the growth of the bacterial strains which indicate that it could act not only as a drug delivery system but also in the treatment of wound healing or dermal bacterial infections thereby proving a potential application for use as a wound dressing. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Development of silver nanoparticles‐loaded calcium alginate beads embedded in gelatin scaffolds for use as wound dressings

Silver nanoparticles (AgNPs)‐loaded calcium alginate beads embedded in gelatin scaffolds were developed to sustain and maintain the release of silver (Ag⁺) ions over an extended time period. The UV irradiation technique was used to reduce Ag⁺ ions in alginate solution to AgNPs. The average sizes of AgNPs ranged between ca 20 and ca 22 nm. The AgNPs‐loaded calcium alginate beads were prepared by electrospraying of a sodium alginate solution containing AgNPs into calcium chloride (CaCl₂) solution. The AgNPs‐loaded calcium alginate beads were then embedded into gelatin scaffolds. The release characteristics of Ag⁺ ions from both the AgNPs‐loaded calcium alginate beads and the AgNPs‐loaded calcium alginate beads embedded in gelatin scaffolds were determined in either deionized water or phosphate buffer solution at 37 °C for 7 days. Moreover, the AgNPs‐loaded calcium alginate beads embedded in gelatin scaffolds were tested for their antibacterial activity and cytotoxicity. © 2014 Society of Chemical Industry     

Influence of the weight ratio of polydimethylsiloxane modified gelatin to silicone rubber on the potential performance of asymmetric bilayer membranes as wound dressings

Asymmetric bilayer membranes have been regarded as ideal wound dressings for skin regeneration. Our previous work reported the potential advantages of polydimethylsiloxane modified gelatin/silicone rubber (PGE/SR) asymmetric bilayer membrane as a wound dressing. However, it is still unknown whether the proportion of the two components of the bilayer membrane has a prominent influence on its relevant performance. Herein, various PGE/SR membranes with different PGE:SR weight ratios (100:25, 100:50 and 100:100) were fabricated through a self‐stratification method driven by surface tension gradients. Subsequently, the effects of the PGE:SR ratios on the relevant performance (i.e. porous structure, mechanical properties, degradability and biocompatibility) of PGE/SR membranes were systematically investigated. The current results demonstrate that the separating force between the PGE and SR components was reduced significantly on increasing the content of SR, and in particular the PGE/SR1 membrane (100:25) exhibited a well‐defined asymmetric bilayer structure with high porosity, appropriate toughness, water uptake, swelling ratio and water permeability. Concomitantly, the maximum weight loss for the PGE/SR1 membrane was ca 70.65% after 9 days of enzymatic degradation, which met the typical healing period of a normal skin wound. In addition, both the original and degraded PGE/SR1 membrane possessed favorable cytocompatibility in vitro, suggesting its potential application as a wound dressing. © 2019 Society of Chemical Industry     

Wound dressings containing bFGF‐impregnated microspheres: Preparation,characterization, in vitro and in vivo studies

The purpose of this study was to synthesize a novel wound dressing containing bFGF‐loaded microspheres for promoting healing and tissue regeneration. Gelatin was chosen as the underlying layer and was prepared in porous sponge. As the external layer, elastomeric polyurethane membranes were used. bFGF was loaded in microspheres to achieve prolonged release for higher efficiency. The microspheres were characterized for particle size, in vitro protein release, and bioactivity. The dressings were tested in in vivo experiments on skin defects created on pigs. At certain intervals, wound areas were measured and tissues from wound areas were biopsied for histological examinations. Average size of the microspheres was 14.36 ± 3.56 μm and the network sponges were characterized with an average pore size of 80–160 μm. Both the release efficiency and the protein bioactivity revealed that bFGF was released in a controlled manner and was biologically active, as assessed by its ability to induce the proliferation of fibroblasts. The rate of wound‐area decrease was much faster and the quality of the newly‐formed dermis was almost as good as the normal skin. The application of this novel bilayer wound dressing provided an optimum healing milieu for the proliferating cells and regenerating tissues. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4772–4781, 2006     

Synthesis and characterization of polyvinyl alcohol/dextran/Zataria wound dressing with superior antibacterial and antioxidant properties

The aim of the present research was to synthesize and characterize polyvinyl alcohol/dextran/Zataria essential oil hydrogel wound dressings. For this purpose, dressings were made with different concentrations of polymers (PVA and Dex) and ZMO by solvent casting method. By dissolving PVA and Dextran in de-ionized water, PVA-Dex gel was made. The polymeric solution was mixed with glycerol. The pH of PVA-DEX-Glycerol solution was adjusted to 3 and glutaraldehyde was used as a cross-linker. ZMO, as the antibacterial and antioxidant agent, was added to the samples in different percentages (2,5,10%). It was found that both Dex and ZMO significantly influenced the hydrophilicity, gel fraction, and water uptake capacity of hydrogel films. The results showed that by the addition of Dex to PVA, the contact angle decreased from 48.54° ± 0.95 to 45.90 ± 0.73°, whereas by the addition of ZMO, the contact angle increased to 71.1 ± 2.43. SEM investigations revealed that the fabricated films had a uniform structure and the surface roughness increased with the addition of ZMO. The results indicated an increased elongation of 11.5% with the incorporation of ZMO into the films. The antimicrobial evaluation of the produced films showed that the loading of 10% v/v ZMO could broaden the microbicidal activity of PVA/Dex/ZMO film. The investigations on the interactions between synthesized wound dressings and fibroblast cells showed that the addition of ZMO into hydrogel films improved cell viability. The findings showed that PVA/Dex/ZMO films could have considerable use as wound dressing.     

两性淀粉的取代度与吸湿保湿性能关系的研究

以淀粉为母体，3-氯-2-羟丙基三甲基氯化铵和氯乙酸为改性剂，通过清洁的半干法工艺合成出不同羧甲基取代度高的水溶性两性淀粉，并对其吸湿、保湿性能进行研究。结果表明，两性淀粉的吸湿、保湿性能均随着羧甲基取代度的增加而增强。当RH为81％，阴离子取代度大于0．08时，两性淀粉的吸湿性与甘油相当，而保湿性在RH81％和RH38％下均优于甘油；两性淀粉的吸湿速率随着羧甲基阴离子含量增加而提高。初步探讨了两性淀粉的吸湿动力学，水分子在两性淀粉中的扩散属于non-Fickian类型。     

Fabrication of cassava (Manihot esculenta Crantz) starch-based ultrafine fibers: Investigation of fundamental and antimicrobial properties

Micro/nano-based fibrous membranes loaded with antibacterial agents have been widely studied in the medical field. In this research, we describe the development of a new environmentally friendly medical dressing based on centrifugally spun cassava starch-based ultrafine fibers loaded with nanosilver (Ag). For this purpose, the spinnability of amylopectin-rich native cassava starch in a centrifugal spinning system was investigated. Polyvinyl alcohol (PVA) was applied to improve the water stability and mechanical properties of the starch-based fibers, and the water stability of the fibers was further improved by posttreatment with formic acid. The morphology, structure, thermal, and tensile properties were studied. The results indicated that the native cassava starch showed excellent spinnability in the centrifugal spinning system. The tensile strength and water stability of the obtained fibrous membranes were improved by adding PVA and further improved after the posttreatment. The antibacterial properties of fibers loaded with Ag were evaluated through a bacteriostatic zone test, and the results showed that the fibers presented good antibacterial properties against Escherichia coli. Therefore, the obtained fibers have great potential for application in the medical dressing field.     

Alginate fibres: an overview of the production processes and applications in wound management

Alginate fibers are made from sodium alginate, which is a natural polymer extracted from brown seaweeds. Over the last two decades, alginate fibers have become well established in the wound management industry where their ion‐exchange and gel‐forming abilities are particularly useful for the treatment of exuding wounds. In order to deliver functional performances for advanced wound management products, many improvements have been made in recent years to enhance the absorption and gel‐forming capabilities and the anti‐microbial properties of alginate fibers. In addition, attempts have been made to use alginate fibers as a carrier to deliver zinc, silver and other active ingredients that are beneficial to wound healing. This paper reviews the development in the production of various fibers from alginate, and summarizes the production processes for calcium alginate, calcium/sodium alginate, sodium alginate, zinc alginate, silver alginate and other types of alginate fibers containing novel functional ingredients. Copyright © 2007 Society of Chemical Industry     

In vivo and in vitro evaluation of the wound healing properties of chitosan extracted from Trametes versicolor

Journal of Polymer Research - Three chitosan-derived compounds, Ch-I, Ch-Qn, and Ch-TPA, were synthesized through condensation reactions between high-molecular weight chitosan and three different...     

Construction of a sandwich-type wound dressing with pain-reliever and pH-responsive antibiotic delivery system

A multifunctional sandwich type wound dressing was designed in which two types of microspheres, one to alleviate the pain (ibuprofen) and the other to protect the wound from infections (Gentamicin or Ciprofloxacin), were embedded into bilayer chitosan sponge. pH of the wound increases from acidic (pH ~ 5) to basic (pH ~ 8) via infection, so pH-dependent antibiotic release system was designed using gelatin B microspheres to respond to increasing pH. Ibuprofen release from chitosan microspheres, on the other hand, was pH-independent not to intervene with pain management in changing pH conditions. Crosslinking with glutaraldehyde (GA) affected both release profile and size distribution of microspheres and 2.5% GA was chosen to obtain pH-responsive gelatin microspheres with narrow size distribution (80% of microspheres in between 15 and 25 μm). The final system was found to be effective against both Staphylococcus aureus and Escherichia coli and changing pH seemed to affect the antimicrobial agent delivery as desired. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48252.     

Dependence of the mechanical properties of woodflour–polymer composites on the moisture content

Woodflour of Eucaliptus saligna with two different chemical treatments (mercerization and esterification with maleic anhydride) was used as filler of an unsaturated polyester matrix. Woodflour was treated to increase the interfacial adhesion with the matrix, to improve the dispersion of the particles, and to decrease the water sorption properties of the final composite. The objective of this study was to determine the influence of the moisture content and the woodflour chemical modification on the physical and mechanical properties of the different composites. Results indicated that mechanical properties (compression and bending tests) were severely affected by moisture and chemical modifications. In wet conditions, the composites made from treated woodflour had the lowest flexural modulus and ultimate stress. It was found that this was a reversible effect, because the original values of the compression properties were recovered after drying. Temperature scans in dynamic mechanical tests showed that an irreversible change occurred during exposure to humid environments, probably due to the hydrolysis of the polyester matrix. Essentially, the same behavior was observed for matrix and composites; however, a wood-related transition overlapped the main transition in the case of wet composites. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 2069–2076, 1998     

芦荟多糖/细菌纤维素复合膜应用于医用敷料的研究

通过生物复合的方法,在Acetobacter xylinum NUST4.2发酵培养基中加入芦荟多糖制备芦荟多糖/细菌纤维素改性复合膜,分别通过热干燥和冷冻干燥法制得改性膜薄膜和改性膜海绵状膜,并对它们作为医用敷料的相关物理性能如吸湿性、透湿性、孔隙率和拉伸性能进行测试。结果表明,改性不影响膜的孔隙率,而且海绵状改性膜的孔隙率较大;其吸湿性能也比较好,能够有效吸收伤口渗出液;同时也具有较高的水蒸气透过率,但作为敷料还需改善;而且抗拉性能要优于细菌纤维素,说明改性可以提高细菌纤维素的机械性能。