Amniotic membrane extract-loaded double-layered wound dressing: evaluation of gel properties and wound healing

The conservative single-layered wound dressing system is decomposed when mixed in polyvinyl alcohol (PVA) solution, which means it cannot be used with a temperature-sensitive drug. The goal of this investigation was to make an amniotic membrane extract (AME)-loaded double-layered wound dressing with an improved healing result compared to the conservative single-layered wound dressing systems. The double-layered wound dressing was developed with PVA/sodium alginate using a freeze–melting technique; one layer was PVA layer and the other was the drug-loaded sodium alginate layer. Its gel properties were assessed compared to single-layered wound dressings. Moreover, in vivo wound-healing effects and histopathology were calculated compared to commercial products. The double-layered wound dressing gave a similar gel fraction and Young’s module as single-layered wound bandages developed with only PVA, and a similar inflammation ability and WVTR as single-layered wound dressings developed with PVA and sodium alginate. Our data indicate that these double-layered wound bandages were just as swellable, but more elastic and stronger than single-layered wound dressings comprised of the same polymers and quantities, possibly giving an acceptable level of moisture and accumulation of exudates in the wound zone. Compared to the commercial product, the double-layered wound dressing comprising 6.7% PVA, 0.5% sodium alginate and 0.01% AME significantly enhanced the wound-healing effect in the wound-healing test. Histological investigations showed that superior full-thickness wound-healing effects compared to the commercial product. Therefore, the double-layered wound dressing would be an outstanding wound-dressing system with improved wound healing and good gel property.     

Preparation of green cellulose diacetate-based antibacterial wound dressings for wound healing

Managing wounds is a growing universal problem and developing effective wound dressings to staunch bleeding and protect wounds from bacterial infections is an increasingly serious challenge. In this work, a remolding electrospinning nanofiber three-dimensional structure wound dressing (CCP) was prepared with superhydrophilicity, high water absorption and absorbing capacity, excellent hemostatic capacity and antibacterial ability, and biocompatibility to promote wound healing. Polyhexamethylene guanidine hydrochloride (PHMG) was grafted to cellulose diacetate (CDA) wound dressing surface through an amide reaction. A water contact angle analysis demonstrated that CCP wound dressing could be beneficial to promote wound exudate management effectively with rapid absorption of water within 0.2 s. In vitro hemo- and cytocompatibility assay showed that a CCP wound dressing had no significant hemotoxicity or cytoxicity. Specifically, CCP wound dressings could be beneficial to accelerate wound hemostasis and further reduce mortality caused by uncontrolled bleeding. Furthermore, CCP wound dressings have an excellent antibacterial ability, which could be beneficial to inhibit wound inflammatory over-reaction and promote normal wound healing. Combined together, the prepared wound dressing in this research effort is expected to have high-potential in clinical applications.     

In vitro and in vivo evaluations of phenytoin sodium-loaded electrospun PVA, PCL, and their hybrid nanofibrous mats for use as active wound dressings

In this work, polyvinyl alcohol (PVA), poly(ε-caprolactone) (PCL), and their electrospun PVA/PCL (80/20) hybrid nanofibrous mats were used for the development of active wound dressings. The biocompatibility and therapeutic effects of the developed products were studied by in vitro cell culture and in vivo experimental rat wound model. The release rate measurements by HPLC showed that the PVA nanofibrous sample containing phenytoin sodium (PHT-Na) has a higher level of the drug release compared to the hybrid PVA/PCL (80/20) and PCL nanofibrous mats. A mesenchymal stem cell was seeded on neat as well as drug-loaded PVA nanofibrous mats. The results represented that the mats provide a suitable environment for cell growth and viability. PVA nanofibers containing PHT-Na have a unique performance for fibroblasts and myofibroblasts cells formation and consequently reaching to the remodeling phase and faster healing of the wounds. Also, PHT-Na-loaded electrospun PVA nanofibrous mats showed a remarkable efficiency in wound closure compared with the treatments results from gauze, commercial wound dressing Comfeel^®Plus, and 2 % PHT-Na ointment. Histology analysis showed the formation of epidermis, the lack of necrosis, and accumulation of collagen fibers in dermis for PVA nanofibrous mats containing PHT-Na.     

海藻酸钙海绵的结构与性能

以海藻酸钠为原料,氯化钙/甘油/酒精溶液为凝固浴,采用冷冻干燥方法制备了海藻酸钙海绵,通过红外光谱和扫描电镜对其结构进行了表征,并对其物理和力学性能、孔隙率、透气率、吸液量和保液量进行评价和测定。结果表明,海藻酸钙海绵的弹性和柔韧性好,具有均匀、连通的孔隙结构,孔径大小为100μm～500μm,孔隙率为84.37%,透气率为44.75%,拉伸强度为0.21 MPa,初始模量为7.72 N/mm,对伤口渗出液的吸液量和保液量为30.48 g/g和5.13 g/g,各项性能均优于或接近海藻酸钙无纺布医用敷料。     

Assessment of reinforced poly(ethylene glycol) chitosan hydrogels as dressings in a mouse skin wound defect model

Wound dressings of chitosan are biocompatible, biodegradable, antibacterial and hemostatic biomaterials. However, applications for chitosan are limited due to its poor mechanical properties. Here, we conducted an in vivo mouse angiogenesis study on reinforced poly(ethylene glycol) (PEG)-chitosan (RPC) hydrogels. RPC hydrogels were formed by cross-linking chitosan with PEGs of different molecular weights at various PEG to chitosan ratios in our previous paper. These dressings can keep the wound moist, had good gas exchange capacity, and was capable of absorbing or removing the wound exudate. We examined the ability of these RPC hydrogels and neat chitosan to heal small cuts and full-thickness skin defects on the backs of male Balb/c mice. Histological examination revealed that chitosan suppressed the infiltration of inflammatory cells and accelerated fibroblast proliferation, while PEG enhanced epithelial migration. The RPC hydrogels promoted wound healing in the small cuts and full layer wounds. The optimal RPC hydrogel had a swelling ratio of 100% and a water vapor transmission rate (WVTR) of about 2000 g/m²/day. In addition, they possess good mechanical property and appropriate degradation rates. Thus, the optimal RPC hydrogel formulation functioned effectively as a wound dressing and promoted wound healing.     

A Self‐Pumping Dressing for Draining Excessive Biofluid around Wounds

Excessive biofluid around wounds often causes infection and hinders wound healing. However, the intrinsic hydrophilicity of the conventional dressing inevitably retains excessive biofluid at the interface between the dressing and the wound. Herein, a self‐pumping dressing is reported, by electrospinning a hydrophobic nanofiber array onto a hydrophilic microfiber network, which can unidirectionally drain excessive biofluid away from wounds and finally accelerate the wound healing process. The hydrophilic microfiber network offers a draining force to pump excessive biofluid through the hydrophobic nanofiber array, which can further keep those pumped biofluids from rewetting the wounds. In the proof of concept, the self‐pumping dressing unidirectionally drains the biofluid from murine dorsum wounds, thereby resulting in faster wound healing than conventional dressings. This unique self‐pumping dressing has enormous potential to be a next‐generation dressing for healing wounds clinically.     

Development of fibroblast culture in three-dimensional activated carbon fiber-based scaffold for wound healing

This work developed a novel bi-layer wound dressing composed of 3D activated carbon fibers that allows facilitates fibroblast cell growth and migration to a wound site for tissue reconstruction, and the gentamicin is incorporated into a poly(γ-glutamic acid)/gelatin membrane to prevent bacterial infection. In an in vitro, field emission scanning electron microscopy shows that rat skin fibroblasts appeared and spread on the surface of activated carbon fibers, and penetrated the interior and exterior of the 3D activated carbon fiber construct to a depth of roughly 200 μm. An in vivo analysis shows that fibroblast cells containing the proposed 3D scaffold had the potential of a biologically functionalized dressing to accelerate wound closure. Additionally, fibroblasts migrated to the wound site in a bi-layer wound dressing containing fibroblasts, enhancing fibronectin and type I collagen expression, resulting in faster skin regeneration than that achieved with a Tegaderm? hydrocolloid dressing or gauze.     

Hydrogel-gauze dressing for moderate-to-severe atopic dermatitis: development and efficacy study on atopic dermatitis-like skin lesions in NC/Nga mice

Topical emollients are known to provide symptomatic relief for atopic dermatitis. In hospitals, wet-wrap therapy has been shown to benefit children with moderate-to-severe atopic dermatitis (AD), but the application of wet-wraps is tedious and time-consuming. Topical emollients have low residence time and often dry out easily. The aim of this work was to develop a hydrogel-gauze dressing that is not only easy to apply but also rehydrates and traps moisture to provide longer relief for AD patients. In this study, a prototype hydrogel-gauze dressing was developed with varying ratios of sodium carboxymethylcellulose (NaCMC) and propylene glycol. The hydrogel-gauze dressings were assessed based on the moisture vapor transmission rate, moisture absorption, mechanical properties and storage stability over three months. Then, the efficacy of the hydrogel-gauze dressing was compared to topical emollients using transgenic NC/Nga mice with AD-like lesions. The NaCMC hydrogel-gauze dressings significantly lowered transepidermal water loss, and the animals displayed a faster recovery, which indicates that hydrogel-gauze dressings can trap moisture more effectively and accelerate AD healing. Hence, we propose that hydrogel-gauze dressings can potentially become an alternative to wet-wrap therapy due to the ease of application and the higher efficacy compared to topical products.     

In vitro evaluation of biocompatibility of different wound dressing materials

The in vitro biocompatibility of newly developed wound dressings consisting of different chitosan salts (chitosan lactate, glutamate and chloride) and a chitosan derivative (methylpyroolidinone chitosan) was compared with three commercially available wound dressings made of collagen, calciumalginate, and gelatin, by evaluation in a fibroblast cell culture system. Three experimental models which reflect relevant stages of wound healing were used, and the significant influence of the experimental setting on the results was demonstrated. Collagen and methylpyrrolidinone chitosan were the most compatible materials under the investigated test conditions. Chitosan chloride and glutamate were the least compatible substances. The results indicated that wound dressings made of chitosan lactate and methylpyrrolidinone chitosan as well as the three commercially available dressings are well tolerated.     

Antimicrobial and release study of drug loaded PVA/PEO/CMC wound dressings

The aim of the present study was to develop PVA/PEO/CMC/aloe vera (PPCAV) and PVA/PEO/CMC/curcumin (PPCCu) dressings with nonwoven polyester fabric as the support layer via freeze-drying (FD) approach. Tetracycline hydrochloride drug (TC) was loaded along with curcumin and aloe vera on these dressings. The morphology of the dressings was characterized by scanning electron microscopy. The swelling behavior, water vapor transmission rate (WVTR), in vitro drug release and antimicrobial nature were analyzed to assess the applicability of these freeze-dried membranes as wound dressing materials. The results show that these dressings made from PPCAVTC and PPCCuTC were highly porous with three-dimensional interconnected porous morphology. The cumulative release of drug from the dressings increases with increasing immersion time and continued up to 24 h, after that it gets leveled off. These dressings evidenced wonderful antimicrobial nature in vitro. These dressings were found to have more than 900 % PBS uptake, WVTR was found to be in the range 2,000–2,500 gm^?2 day^?1. These dressings possess many characteristics desirable in an ideal wound dressing material.     

In vivo tests of a novel wound dressing based on biomaterials with tissue adhesion controlled through external stimuli

The high incidence of wounds by second intention and the high costs associated with their treatment give rise to the need for the development of wound dressings that protect not only the wounds themselves but that are also able to promote cell proliferation and skin regeneration. Moreover, it is also very important that no damage to the new regenerated tissue is generated while removing the dressing. In this work, a novel wound dressing, which would be able to favor tissue repair and be removed at an appropriate scheduled moment by means of an external stimulus without promoting extensive damage to the new tissue, was produced and tested. Polyurethane membranes were modified by grafting polymers based on poly(n-isopropylacrylamide) (P-N-IPAAm). P-N-IPAAm undergoes a phase transition at approximately 32°C, which changes its behavior from hydrophilic (below 32°C) to hydrophobic. It was hypothesized that, by reducing the temperature near the wound dressing to values lower than 32°C, the detachment of the dressing would become more effective. The wound dressings containing P-N-IPAAm grafts were tested in vivo by covering excisional wounds produced in mice. The produced dressings were placed in direct contact with the lesions for 3 days. Results showed that the hypothermia due to anesthesia required to remove the dressings from mice lowered the local temperature to 28°C and favored the detachment of the wound dressings containing P-N-IPAAm grafts. Histological analyses showed that lesions covered by dressings presented less intense inflammatory events and denser connective tissue than did the wounds without dressings. The wounds covered by polyurethane membranes with P-N-IPAAm grafts showed signs of more intense re-epithelization and angiogenesis than did the lesions covered by polyurethane without grafts.     

A superabsorbent polymer-containing wound dressing efficiently sequesters MMPs and inhibits collagenase activity in vitro

Superabsorbent polymer (SAP)-containing wound dressings present a valuable and unique category of wound management products. An in vitro approach was used to assess the effects of a new SAP dressing in treatment of non-healing wounds. It was shown that the SAP dressing possesses a significant binding capacity for MMP-2 and MMP-9 in vitro (P < 0.001). The inclusion of the bound proteases was so strong that no MMP-2 and only marginal amounts of MMP-9 were released from the dressing samples in a subsequent elution step. In addition, the SAP dressing was able to take up collagenase and reduce its activity in vitro. However, collagenase was not completely inactivated upon binding and enzyme-mediated substrate turnover could be observed at the dressings. In conclusion, in vitro data confirm the positive effect of the SAP wound dressing observed in vivo. The findings suggest that it should be specifically useful for highly exuding wounds with an elevated proteolytic activity that needs to be reduced to support healing.     

Evaluation of various silver-containing dressing on infected excision wound healing study

Silver-containing dressings have been widely used for controlling wound infection. However, the relationship between different concentrations of silver in dressings and their antimicrobial activities and wound-healing efficacies remains unclear. In the present study, we (in cooperation with Bio-medical Carbon Technology) investigated various silver-containing activated carbon fibers to understand the effects of different silver concentrations on the efficacies of a silver containing dressing. Our results indicated that various silver-containing activated carbon fibers exhibited good antibacterial effects and biocompatibility in terms of cell viability and that silver concentration showed a minor influence on cell growth. The infected excision wound model indicated that compared to silver-containing activated carbon fiber and other commercial silver-containing dressings assisted wound healing by promoting granulation and collagen deposition. Meanwhile, the silver ion can only be restrained in epidermis by intact skin. During application on the wound area, a temporary increase of serum silver can be detected, but this elevated serum silver level decreased to a subtle level after the removal of silver-containing activated carbon fiber.     

Dynamics of silver nanoparticle release from wound dressings revealed via in situ nanoscale imaging

The use of silver nanoparticles (AgNPs) in textiles for enhanced anti-microbial properties has led to concern about their release and impact on both human and environmental health. Here a novel method for in situ visualization of AgNP release from silver-impregnated wound dressings is introduced. By combining an environmental scanning electron microscope, a gaseous analytical detector and a peltier cooling stage, this technique provides near-instantaneous nanoscale characterization of interactions between individual water droplets and AgNPs. We show that dressings with different silver application methods have very distinct AgNP release dynamics. Specifically, water condensation on dressings with AgNP deposited directly on the fiber surface resulted in substantial and rapid AgNP release. By comparison, AgNP release from wound dressing with nanoparticles grown, not deposited, from the fiber surface was either much slower or negligible. Our methodology complements standard bulk techniques for studying of silver release from fabrics by providing dynamic nanoscale information about mechanisms governing AgNP release from individual fibers. Thus coupling these nano and macro-scale methods can provide insight into how the wound dressing fabrication could be engineered to optimize AgNP release for different applications.     

Radiation synthesis of PVP/alginate hydrogel containing nanosilver as wound dressing

Hydrogels with polyvinyl pyrrolidone (PVP) and alginate were synthesized and silver nanoparticles were incorporated in hydrogel network using gamma radiation. PVP (10?and 15?%) in combination with 0.5?and 1?% alginate was gamma irradiated at different doses of 25?and 40?kGy. Maximum gel percent was obtained with 15?% PVP in combination with 0.5?% alginate. The fluid absorption capacity for the PVP/alginate hydrogels was about 1881–2361?% at 24?h. Moisture vapour transmission rate (MVTR) of hydrogels containing nanosilver at 24?h was 278.44?g/(m²h). The absorption capacity and moisture permeability of the PVP/alginate–nanosilver composite hydrogel dressings show the ability of the hydrogels to prevent fluid accumulation in exudating wound. The hydrogels containing nanosilver demonstrated strong antimicrobial effect and complete inhibition of microbial growth was observed with 70?ppm nanosilver dressings. PVP/alginate hydrogels containing nanosilver with efficient fluid handling capacity and antimicrobial activity was found suitable for use as wound dressing.     

Preparation of antimicrobial wound dressings via thiol–ene photopolymerization reaction

Preparation of poly (urethane-acrylate) based wound dressings with the ability to boost self-healing of skin tissue through physical protection and maintaining hygiene and moist environment over wounded area is described in the present work. The dressings were prepared via a visible-light induced thiol–ene photopolymerization reaction of a mixture consisting methacrylate urethane prepolymers with hydrophilic and hydrophobic backbones, a quaternary ammonium salt containing methacrylate monomer as an antimicrobial agent, hydroxyethyl methacrylate as reactive diluent and a tetra-functional thiol molecule as a transfer agent. The prepared dressings were characterized and their performance as wound dressings were evaluated through measuring their equilibrium water absorption (EWA), water vapor transmission rate (WVTR), mechanical, and biological properties. Based on recorded data, the optimized dressing formulation had suitable tensile strength even at fully hydrated state and it could preserve the appropriate moist environment by balanced EWA and WVTR ratio. MTT assay confirmed proper cytocompatibility of those dressings containing optimized concentration of quaternary ammonium salt containing monomer (20 wt% or less). Examination of antibacterial activity against different Gram positive, Gram negative bacteria and a fungal strain revealed a complete killing ability for those dressings containing at least 20 wt% of quaternary ammonium salt containing monomer.     

Multifunctional Hydrophobized Microparticles for Accelerated Wound Healing after Endoscopic Submucosal Dissection

Endoscopic submucosal dissection (ESD) provides strong therapeutic benefits for early gastrointestinal cancer as a minimally invasive treatment. However, there is currently no reliable treatment to prevent scar contracture resulting from ESD which may lead to cicatricial stricture. Herein, a multifunctional colloidal wound dressing to promote tissue regeneration after ESD is demonstrated. This sprayable wound dressing, composed of hydrophobized microparticles, exhibits the multifunctionality necessary for wound healing including tissue adhesiveness, blood coagulation, re‐epithelialization, angiogenesis, and controlled inflammation based on hydrophobic interaction with biological systems. An in vivo feasibility study using swine gastric ESD models reveals that this colloidal wound dressing suppresses fibrosis and accelerates wound healing. Multifunctional colloidal and sprayable wound dressings have an enormous therapeutic potential for use in a wide range of biomedical applications including accelerated wound healing after ESD, prevention of perforation, and the treatment of inflammatory diseases.     

Experimental wound dressings of degradable PHA for skin defect repair

The present study reports construction of wound dressing materials from degradable natural polymers such as hydroxy derivatives of carboxylic acids (PHAs) and 3-hydroxybutyrate/4-hydroxybutyrate [P(3HB/4HB)] as copolymer. The developed polymer films and electrospun membranes were evaluated for its wound healing properties with Grafts—elastic nonwoven membranes carrying fibroblast cells derived from adipose tissue multipotent mesenchymal stem cells. The efficacy of nonwoven membranes of P(3HB/4HB) carrying the culture of allogenic fibroblasts was assessed against model skin defects in Wistar rats. The morphological, histological and molecular studies revealed the presence of fibroblasts on dressing materials which facilitated wound healing, vascularization and regeneration. Further it was also observed that cells secreted extracellular matrix proteins which formed a layer on the surface of membranes and promoted the migration of epidermal cells from the neighboring tissues surrounding the wound. The wounds under the P(3HB/4HB) membrane carrying cells healed 1.4 times faster than the wounds under the cell-free membrane and 3.5 times faster than the wounds healing under the eschar (control).The complete wound healing process was achieved at Day 14. Thus the study highlights the importance of nonwoven membranes developed from degradable P(3HB/4HB) polymers in reducing inflammation, enhancing angiogenic properties of skin and facilitating better wound healing process.     

Chitosan and alginate polyelectrolyte complex membranes and their properties for wound dressing application

This study investigated the characteristics and drug release properties of membranes of chitosan and alginate prepared via a casting/solvent evaporation technique. Membranes of chitosan and alginate with silver sulfadiazine as model drug incorporated in different concentrations and different membrane compositions were obtained. The polyblend solution viscosity reached to the highest at the composition polyblends of (1:1). This chitosan/alginate membranes showed pH- and ionic strength-dependent water uptake properties and had the WVTR rang from 442 to 618 g/m²/day. The maximum value of the dry membrane of breaking strength was 52.16 MPa and the maximum value of the wet membrane breaking elongation was 46.28%. The results of controlled release studies showed that the silver sulfadiazine release rate was the fastest when the alginate content was 50%. On the basis of the requisite physical properties, the chitosan–alginate PEC membrane can be considered for potential wound dressing or controlled release application.     

石松子粉粉尘爆炸试验研究

该论文采用20 L球形爆炸测试装置对粒径在75μm以下的石松子粉的粉尘爆炸下限浓度、爆炸压力和爆炸指数随粉尘浓度的变化规律等进行了研究。研究结果表明:石松子粉粉尘爆炸下限浓度在20～40 g/m3之间,在粉尘浓度相对较低的60～500 g/m3时,粉尘的爆炸压力和爆炸指数随着粉尘浓度的提高而急速上升,在浓度为500 g/m3时达到最大,此时最大爆炸压力为0.69 MPa,爆炸指数为17.20 MPa.m/s;继续增加粉尘浓度,爆炸压力和爆炸指数略有下降,但仍维持在较高值;并判定石松子粉粉尘爆炸危险性分级为Ⅰ级。