The preparation of polyurethane foam combined with pH-sensitive alginate/bentonite hydrogel for wound dressings

Polyurethane (PU) foam was combined with protein drug-loaded pH-sensitive alginate-bentonite hydrogel for wound dressings. Alginate is a linear copolymer composed of 1–4-linked β-D-mannuronic acid (M) and its c-5-epimer α-Lguluronic acid (G). The amount of (M) and (G) and their sequential distribution are varied depending on the alginate source. Soluble sodium alginate can become a hydrogel when cross-linked with divalent cations and has widespread applications in the food, drink, pharmaceutical and bioengineering industries. Recently, it has been also proposed as a biomaterial for drug delivery systems. Bentonites are the natural inorganic polymers consisting of a large proportion of expandable clay minerals with a three-layer structure such as montmorillonite, beidellite, nontronite, etc. They are important adjutants and supports for medical products, and they have many useful physicochemical, mechanical, and biological properties such as absence of toxicity, indifference to other raw materials, sorption, swelling, and complex formation properties. Alginate-bentonite hydrogels were prepared at concentration ratios of 10/0, 7/3, 5/5, 3/7. PU foams were prepared using hydrophilic polyols. We investigated the controlled release of a protein drug from PU foam combined with alginate-bentonite hydrogel at different pH values of 4.2, 5.2, 7.2, 8.2. The mechanical properties and cytotoxicity tests of this foam were also studied.     

Composite wound dressing for drug release

Present study is focused on the preparation of two layers composite wound dressing for drug release. The outer layer is made of hydrogel which contains of drug and the core layer is made of fabric. The two layers structure of composite dressing is formed by grafting of polyacrylamide-co-acrylic acid hydrogel on cotton fabric using ammonium per sulphate (APS) as chemical initiator and polyethylene glycol (PEG) as crosslinker. The major factors affecting graft copolymerization of hydrogel on cotton fabric are optimized by varying concentration of monomers & initiator, reaction temperature and addition time of crosslinker. Maximum grafting of hydrogel is obtained at 5 % (w/v) APS and 15 % acrylamide/acrylic acid (1:1 w/w ratio) concentration. The FTIR spectra of composite dressing shows characteristics peak of acrylic acid and acrylamide. The composite wound dressing material is loaded with model drug bovine serum albumin (BSA) and drug release behaviour is studied at different pH. The dressing shows drug release in different pH with maximum release of drug in acidic medium.     

Advanced Strategies for 3D Bioprinting of Tissue and Organ Analogs Using Alginate Hydrogel Bioinks

Alginate is a natural polysaccharide that typically originates from various species of algae. Due to its low cost, good biocompatibility, and rapid ionic gelation, the alginate hydrogel has become a good option of bioink source for 3D bioprinting. However, the lack of cell adhesive moieties, erratic biodegradability, and poor printability are the critical limitations of alginate hydrogel bioink. This review discusses the pivotal properties of alginate hydrogel as a bioink for 3D bioprinting technologies. Afterward, a variety of advanced material formulations and biofabrication strategies that have recently been developed to overcome the drawbacks of alginate hydrogel bioink will be focused on. In addition, the applications of these advanced solutions for 3D bioprinting of tissue/organ mimicries such as regenerative implants and in vitro tissue models using alginate-based bioink will be systematically summarized.     

The effect of bentonite concentration on the drug delivery efficacy of a pH-sensitive alginate/bentonite hydrogel

We produced a protein loaded, pH-sensitive alginate-bentonite hydrogel for wound dressings. Alginate is a nontoxic polysaccharide with favorable pH-sensitive properties that make it useful for the intestinal delivery of protein drugs. However, the use of alginate for drug delivery is limited by drug leaching and rapid dissolution of alginate at the higher pH, which may result in lower entrapment efficiency and a burst in the release of entrapped protein drugs. To overcome these problems, we created a novel cross-linked alginate-bentonite hydrogel by combining mineral-rich bentonite with the alginate matrix along with an additive to ensure controlled release. We analyzed the gel in the drug loading process in an aqueous environment by looking at the release profiles of a model protein drug (BSA) from the hydrogel at pH values of 4.5, 5.2 (skin area) and 7.4, 9.2 (wound area). The swelling ratio decreased with bentonite concentration, but did not fall below 6. The rate of drug release was slowest at a pH value of 4.5 and fastest at a pH value of 9.2. The rate of drug release decreased with bentonite concentration. The presence of bentonite prevents the rapid dissolution of alginate at the higher pH, ensuring the controlled release of the entrapped drug.     

A Novel Semi-bionanofibers through Introducing <Emphasis Type="Italic">Tragacanth Gum</Emphasis> into PET Attaining Rapid Wetting and Degradation

Untreated polyethylene terephthalate has limitation in some medical applications, such as wound dressing due to the hydrophobic property. Thereby, Tragacanth Gum (TG) as a natural polysaccharide utilized in polymer solution led to novel semi-bionanofibers of PET/TG blends (15:1, 15:2 and 15:3) through electrospinning method. Fourier transform infrared spectroscopy results confirmed the existence of hydrophilic groups of TG such as hydroxyl groups. Moreover, twice water uptake of PET/TG comparing with PET nanofibers indicated the hydrogel properties, also PET/TG nanofibers possessed high surface wettability through reduction of contact angle from 113 to 0°. Further, differential scanning calorimetry analysis indicated the alteration in the crystalline structure of PET/TG nanofibers that led to faster degradation in various pH values. The SEM images of PET/TG nanofibers displayed the greater average diameter with increasing TG content (283 nm) comparing with PET nanofibers (193 nm). Also introducing more TG in the nanofibers exhibited lower mechanical properties.     

Controlling the moisture absorption capacity in a fiber-reinforced thermoplastic starch using sodium trimetaphosphate

A novel biodegradable material derived from thermoplastic potato starch was prepared with intended uses in high moisture environments where its high water sorption characteristics are beneficial, such as wound dressing, transdermal patches or food packaging. A modified composite was prepared for this purpose by reactive extrusion whereby potato starch and 2.5-25% (w/w) sisal cellulose fibers were compounded together in the presence of 2.7% (w/w) sodium trimetaphosphate. The fibers were included to increase the wet strength of the material. A low degree of substitution (0.088-0.113) was sought by bound phosphate groups with anionic character in order to overcome a reduction in moisture absorption capacity resulting from fiber incorporation, yet being insufficient to cause embrittlement via crosslinking. The results showed the approach has sufficient merit to minimize the influence of the hydrophobic fibers on the water absorption capacity of the starch material but adhering to so low of a degree of substitution could not fully prevent a reduction. The results also suggested that the fibers may have participated in the crosslinking reaction.     

Alginate Hydrogels Coated with Chitosan for Wound Dressing

In this work, a coating of chitosan onto alginate hydrogels was realized using the water-soluble hydrochloride form of chitosan (CH-Cl), with the dual purpose of imparting antibacterial activity and delaying the release of hydrophilic molecules from the alginate matrix. Alginate hydrogels with different calcium contents were prepared by the internal setting method and coated by immersion in a CH-Cl solution. Structural analysis by cryo-scanning electron microscopy was carried out to highlight morphological alterations due to the coating layer. Tests in vitro with human mesenchymal stromal cells (MSC) were assessed to check the absence of toxicity of CH-Cl. Swelling, stability in physiological solution and release characteristics using rhodamine B as the hydrophilic model drug were compared to those of relative uncoated hydrogels. Finally, antibacterial activity against Escherichia coli was tested. Results show that alginate hydrogels coated with chitosan hydrochloride described here can be proposed as a novel medicated dressing by associating intrinsic antimicrobial activity with improved sustained release characteristics.     

Preparation of Cross-linked Chitosan Quaternary Ammonium Salt Hydrogel Films Loading Drug of Gentamicin Sulfate for Antibacterial Wound Dressing

Hydrogels, possessing high biocompatibility and adaptability to biological tissue, show great usability in medical applications. In this research, a series of novel cross-linked chitosan quaternary ammonium salt loading with gentamicin sulfate (CTMCSG) hydrogel films with different cross-linking degrees were successfully obtained by the reaction of chitosan quaternary ammonium salt (TMCS) and epichlorohydrin. Fourier transform infrared spectroscopy (FTIR), thermal analysis, and scanning electron microscope (SEM) were used to characterize the chemical structure and surface morphology of CTMCSG hydrogel films. The physicochemical property, gentamicin sulphate release behavior, cytotoxicity, and antibacterial activity of the CTMCSG against Escherichia coli and Staphylococcus aureus were determined. Experimental results demonstrated that CTMCSG hydrogel films exhibited good water stability, thermal stability, drug release capacity, as well as antibacterial property. The inhibition zone of CTMCSG hydrogel films against Escherichia coli and Staphylococcus aureus could be up to about 30 mm. Specifically, the increases in maximum decomposition temperature, mechanical property, water content, swelling degree, and a reduction in water vapor permeability of the hydrogel films were observed as the amount of the cross-linking agent increased. The results indicated that the CTMCSG-4 hydrogel film with an interesting physicochemical property, admirable antibacterial activity, and slight cytotoxicity showed the potential value as excellent antibacterial wound dressing.     

Environment-friendly crosslinking of cornstarch by pentanedioic acid for stabilizing the viscosity of starch paste during warp sizing

Acid-thinned cornstarch was crosslinked with pentanedioic acid to different degrees to enhance viscosity stability of cooked starch paste for replacing the currently used toxic crosslinking agents such as formaldehyde and epichlorohydrin in the preparation of starch sizing agents. The degree of crosslinking was determined according to the stability, adhesion-to-fibers, film properties, desizability, and aerobic biodegradation of crosslinked starch. The degree of crosslinking showed significant effects on the stability, adhesion, desizability, and film properties, but was less sensitive to the biodegradation and wear loss of starch film. Suitable degree of crosslinking resulted in stable viscosity, good adhesion to fibers, strong and bending resistant film, and better desizability. Low degree of crosslinking could be utilized to increase the stability and improve usability of the starch used as warp sizing agent. The degree of crosslinking range (902-477 anhydroglucose units per crosslink) was recommended to stabilize the viscosity of cooked starch paste and improve the sizing properties of starch sizing agents.     

Structures,Properties and Applications of Alginates

Alginate is a hydrocolloid from algae, specifically brown algae, which is a group that includes many of the seaweeds, like kelps and an extracellular polymer of some bacteria. Sodium alginate is one of the best-known members of the hydrogel group. The hydrogel is a water-swollen and cross-linked polymeric network produced by the simple reaction of one or more monomers. It has a linear (unbranched) structure based on d-mannuronic and l-guluronic acids. The placement of these monomers depending on the source of its production is alternating, sequential and random. The same arrangement of monomers can affect the physical and chemical properties of this polysaccharide. This polyuronide has a wide range of applications in various industries including the food industry, medicine, tissue engineering, wastewater treatment, the pharmaceutical industry and fuel. It is generally recognized as safe when used in accordance with good manufacturing or feeding practice. This review discusses its application in addition to its structural, physical, and chemical properties.     

Manufacturing and analyses of wet-laid nonwoven consisting of carboxymethyl cellulose fibers

Carboxymethyl cellulose (CMC) is a cellulose derivative having water-soluble property, biodegradability, and biocompatibility. It has been used in various medical applications as forms of gel, film, membrane, or powder. In this study, composite CMC nonwovens were produced, by a wet-laid nonwoven process, to improve the wet strength of carboxymethyl cellulose nonwovens. Followed by preparing the CMC fibers from cotton fiber, the composite CMC nonwovens composed of CMC fibers and PE/PP bicomponent fibers were manufactured by using 85/15 % v/v of ethanol/water solution as a dispersion medium. Structural analyses of CMC fibers, such as XRD, TGA, FT-IR, and degree of substitution indicated that CMC fibers were successfully produced. The wet strength of CMC nonwoven was dramatically increased by blending with the PE/PP fibers without sacrificing the key properties for wound dressing materials such as liquid absorption, gel blocking and liquid retention. It is expected that the composite CMC nonwovens will be a good candidate for wound dressing materials for mild exudate condition.     

SPI/PEO blended electrospun martrix for wound healing

Conventional textile based wound dressing materials are cost effective and highly absorbent, but when used alone fails to provide optimal wound healing conditions like homeostasis, non-adherence, maintenance of a moist wound bed, etc. Electrospun polymer web meets the requirements outlined for wound healing, by their microfibrous structures provide suitable environment for wound healing apart from the function of polymers. In this study, blends of soy protein isolate (SPI) and poly(ethylene oxide) (PEO) nano fiber web was prepared by electro spinning process. The developed blended nano fiber web was subjected to SEM, FTIR to evaluate fiber size and functional properties respectively. The Moisture vapour transmission rate (MVTR) result shows the blended electrospun web gives suitable mosit environment over wound bed such as the MVTR is 2994 g/m²/day. The blended electrospun web gives positive result on antimicrobial activity. The effect of SPI/PEO blended electrospun web on wound healing was experimented with female wistar rats and the blended electrospun web shows excellent result on wound healing by the growth of new epithelium without any significant adverse reaction. Forming of SPI/PEO electrospun fiber was fulfilled many critical elements desirable in a wound material.     

Preparation and properties of polyvinyl alcohol/tannic acid composite film for topical treatment application

The purpose of this study was to develop an effective potential wound dressing material based on a polyvinyl alcohol (PVA) and tannic acid (TA) composite film. To prepare the PVA/TA films, PVA and TA blended aqueous solutions were cast into film form by spreading the solutions and drying them. Then the films were heat treated at 155 oC for 3 min to promote esterification between the PVA and TA. After removing un-crosslinked moieties from the films by rinsing and drying, the films were investigated by swelling behavior, FTIR spectroscopy, XRD and TGA. And, the antibacterial and antioxidant abilities of the films were also examined in this study. Through this investigation it was discovered that TA effectively acts as a functional antibacterial and antioxidant agent as well as crosslinker in the PVA/TA system. Thus, the PVA/TA composite films prepared by the casting and heat treatment method proposed in this study are expected to be used for topical medication, such as wound dressing material.     

Development and characterization of bamboo gauze fabric coated with polymer and drug for wound healing

The bamboo yarn of Ne 40^s was used for the preparation of the Gauze fabric. The physical properties such as areal density and stiffness of fabrics were measured. The fabric was then scoured and bleached as per the standard procedure using distilled water. Chitosan-sodium alginate, Calcium-sodium alginate polymer and their mixture were coated separately on the gauze structure to improve the antibacterial and wound healing property of the bandage. Scanning electron microscope (SEM) analysis was carried out to observe the uniform distribution of polymers in the samples. The antibiotic drugs were selected based on the antibiotic sensitivity test. The drugs such as Tetracycline hydrochloride (250 mg), Chloramphenicol (250 mg) and Rifampicin (250 mg) were immobilized on the polymer coated fabrics to increase the rate of wound healing and antibacterial activity. The drug loaded samples were subjected to drug release study for about four days in a static condition. The results show that good amount of drug was released during all the four days. Further, the antibacterial activity of the drug loaded and polymer coated samples were evaluated against S. aureus and Proteus bacteria. The results show excellent antibacterial activity.     

Acrylamide/potassium 3-sulfopropyl methacrylate/sodium alginate/bentonite hybrid hydrogels: Synthesis,characterization and its application in lauths violet removal from aqueous solutions

In this report, it was to investigate that the swelling and dye sorption properties of a series of novel hybrid composite hydrogel sorbent systems containing polysaccharide/clay polyelectrolyte based on acrylamide/potassium 3-sulfopropyl methacrylate and sodium alginate, and clay such as bentonite were synthesized with free radical solution polymerization by using ammonium persulfate/N,N,N’,N’-tetramethylethylenediamine as redox initiating pair in presence of poly(ethylene glycol) diacrylate as a crosslinker. Swelling experiments were performed in water at 25 °C, gravimetrically. The hydrogels, the semi-interpenetrating polymer networks, and the hybrid composite hydrogel systems that synthesized in this study have showed high water absorbency. Some swelling and diffusion properties were calculated, and they were discussed for the hybrid hydrogel systems prepared under various formulations. The equilibrium percentage swelling degree of highly swollen hybrid composite hydrogel systems ranges are 718-2055 %. FT-IR analysis and SEM technique were applied for characterization. For sorption of water-soluble cationic dye such as lauths violet into the hydrogel systems was studied by batch sorption technique at 25 °C. For equilibrium sorption studies, dye sorption percentage, dye uptake performance, and partition coefficient of the hydrogel systems have been investigated. The values of dye sorption percentage of the hydrogels were changed among 87.11-96.39 %. Consequently, the hydrogel systems developed in this study could serve as a potential device for water and dye sorbent.     

Designing double-layered nanofibrous membranes as a wound dressing material

New generation wound dressings require the criteria that both bioactive and conventional wound dressing materials can recompense the fundamental properties like defense of wound from microbial invasion, dehydration during the wound care duration and mimic the healing process. In this study, functional double-layered nanofibrous composite membranes were fabricated via electrospinning method. The matrices consist of a sheet of ampicillin loaded poly(2-hydroxylethyl methacrylate/polyacrylic acid (pHEMA/pAA) nanofibers on the upper side (first layer: pH sensitive antibacterial barrier) and a sheet of poly(ε-caprolactone) (PCL)/gelatin nanofibers (second layer: bioactive part). Ampicillin was successfully incorporated to double-layered matrices which greatly changed the mechanical properties, biodegradability and water uptake ratios (up to 4 fold higher values). The success of the antimicrobial activity of ampicillin on Staphylococcus aureus and Escherichia coli was indicated by the inhibition zone test. pH sensitivity was confirmed by the swelling and ampicillin release studies by shifting pH value to basic environment. Thus, double-layered pHEMA-pAA nanofibers suggest as a potential wound dressing material for its pH sensitive drug delivery ability and its bioactive part.     

Chitin and Chitosan: Prospective Biomedical Applications in Drug Delivery,Cancer Treatment,and Wound Healing

Chitin and its derivative chitosan are highly abundant polymers in nature, appearing in both the shells and exoskeletons of various marine and non-marine species. Since they possess favorable properties, such as biocompatibility, biodegradability, non-toxicity, and non-immunogenicity, they have gained recent attention due to their enormous potential biomedical applications. The polycationic surface of chitosan enables it to form hydrogenic and ionic bonds with drug molecules, which is one of its most useful properties. Because chitosan is biocompatible, it can therefore be used in drug delivery systems. The development of chitosan-based nanoparticles has also contributed to the significance of chitin as a drug delivery system that can deliver drugs topically. Furthermore, chitin can be used in cancer treatment as a vehicle for delivering cancer drugs to a specific site and has an antiproliferative effect by reducing the viability of cells. Finally, chitosan can be used as a wound dressing in order to promote the faster regeneration of skin epithelial cells and collagen production by fibroblasts. As discussed in this review, chitin and chitosan have diverse applications in the medical field. Recognizing the biomedical applications of these two polymers is essential for future research in tissue engineering and nanobiotechnology.     

Naringin-loaded Poly(ε-caprolactone)/Gelatin Electrospun Mat as a Potential Wound Dressing: In vitro and In vivo Evaluation

In the present study, naringin, a flavonoid isolated from the grape and citrus fruit species, was incorporated with poly(ε-caprolactone)/gelatin composite mats in order to develop a potential wound dressing. The composite mats were prepared by electrospinning of poly(ε-caprolactone)/gelatin (1:1 (w/w)) solution incorporated with 1.50 %, 3 % and 6 % (w/w) of naringin. The electrospun mats were evaluated regarding their morphology, contact angle, water-uptake capacity, water vapor transmission rate, tensile properties, drug release, cellular response and in vivo wound healing activity. The study showed that after 2 weeks, the full-thickness excisional wounds of Wistar rats treated with the naringin-loaded dressings achieved a wound closure of higher than 94 % and the dressing containing 6 % (w/w) naringin had almost 100 % wound closure. The sterile gauze, as the control group, showed nearly 86 % of wound closure after this period of time. Our results provided evidence that supports the possible applicability of naringin-loaded wound dressing for successful wound treatment.     

An Electrospun Scaffold Loaded with an Enteromorpha Polysaccharide for Accelerated Wound Healing in Diabetic Mice

The design and development of innovative multifunctional wound dressing materials in engineered biomaterials is essential for promoting tissue repair. In this study, nanofibrous wound dressing materials loaded with anti-inflammatory ingredients were manufactured by a promising electrospinning strategy, and their capability for treating diabetic wounds was also investigated. A scaffold blend consisting of an Enteromorpha polysaccharide and polyvinyl alcohol (PVA) was fabricated. The in vitro and in vivo studies confirmed the efficacy of PVA/EPP1 fiber. We found that PVA/EPP1 fiber accelerated the repair of a full-thickness skin wound in diabetic mice. The results suggest that this scaffold could effectively shorten the wound healing time by inhibiting inflammatory activity, which makes it a promising candidate for the treatment of hard-to-heal wounds caused by diabetes.     

Preparation and characterization of nylon-6/gelatin composite nanofibers via electrospinning for biomedical applications

Easy fabrication, porosity, good mechanical properties, and composition controllable of the electrospun nanofiber mat make this material a promising candidate for wound dressing applications. In the present study, nylon6/gelatin electrospun nanofiber mats are introduced as novel wound dressing materials. The introduced mats were synthesized by electrospinning of nylon6 and gelatin mixtures, three mats containing different gelatin content were prepared; 10, 20 and 30 wt%. Interestingly, addition of the gelatin did not affect the mechanical properties of the nylon 6, moreover the mat containing 10 wt% gelatin revealed higher mechanical properties due to formation of spider-net like structure from very thin nanofibers (～10 nm diameter) bonding the main nanofibers. Biologically study indicates that gelatin incorporation strongly enhances the bioactivity performance as increasing the gelatin content linearly increases the MC3T3-E1 cell attachment. Overall, the obtained results recommend exploiting the introduced mats as wound dressing material.