Rita Singh

Radiation Processed Amniotic Membranes in the Treatment of Non-Healing Ulcers of Different Etiologies

The amniotic membranes were collected from the placentae of selected and screened donors. Processing was done by washing the fresh amniotic membrane successively in sterile saline, 0.05% sodium hypochlorite solution and sterile distilled water until it was completely cleared of blood particles. The membranes were sterilized by gamma irradiation at 25 kGy. The processed amniotic membranes were applied to 50 open wounds comprising of 42 full thickness defects and eight partial thickness defects. These included leprotic, diabetic, traumatic, gravitational ulcers and superficial burn in the form of scald and corrosive burn. The radiation processed amniotic membranes favoured healing of unresponsive and non-healing ulcers of different etiologies. Ulcers with duration of minimum 3 weeks to maximum 12 months were found to heal in 2–6 weeks by the application of amniotic membranes.

Chitin membrane for wound dressing application – preparation, characterisation and toxicological evaluation

Chitin, a unique biopolymer based on the N‐acetyl‐glucosamine monomer is envisioned to promote rapid dermal regeneration and accelerate wound healing. It has many useful and advantageous biological properties for its application as a wound dressing. Chitin membranes were prepared using lithium chloride/dimethylacetamide solvent system and evaluated for use as a wound dressing. Swelling behaviour, moisture vapour transmission rate, microbial impermeability and antimicrobial efficacy of the dressings was evaluated. The chitin dressing provided an effective barrier to microbial penetration and exerted a broad bacteriostatic action against Gram‐positive and Gram‐negative organisms. Gamma irradiation at 25 kGy was found suitable for sterilisation of the dressings. The thermal decomposition of unirradiated and irradiated chitin membranes was investigated. No significant change in the thermal behaviour because of irradiation at 25 kGy was observed. In vitro biodegradation of unirradiated and irradiated chitin membranes showed the susceptibility of the chitin dressing to lysozyme. Irritant effect of the chitin membrane dressings on skin was tested. Subcutaneous and scarification test in guinea pigs showed no signs of inflammation. This was further supported by the Finkelstein’s test performed in rabbits. The chitin membranes were found to have optimal performance characteristics of a wound dressing and showed no toxicity or possible adverse reactions. The study shows the chitin dressings as useful adjunct in wound care.

Chitin membranes containing silver nanoparticles for wound dressing application

Silver nanoparticles are gaining importance as an antimicrobial agent in wound dressings. Chitin is a biopolymer envisioned to promote rapid dermal regeneration and accelerate wound healing. This study was focused on the evaluation of chitin membranes containing silver nanoparticles for use as an antimicrobial wound dressing. Silver nanoparticles were synthesised by gamma irradiation at doses of 50 kGy in the presence of sodium alginate as stabiliser. The UV–Vis absorption spectra of nanoparticles exhibited an absorption band at 415–420 nm, which is the typical plasmon resonance band of silver nanoparticles. The peaks in the X‐ray diffraction (XRD) pattern are in agreement with the standard values of the face‐centred cubic silver. Transmission electron microscopy (TEM) images indicate silver nanoparticles with spherical morphology and small particle size in the range of 3–13 nm. In vitro antimicrobial tests were performed using Pseudomonas aeruginosa and Staphylococcus aureus to determine the antimicrobial efficiency of the chitin membranes containing 30, 50, 70 and 100 ppm nanosilver. No viable counts for P. aeruginosa were detected with 70 ppm silver nanoparticles dressing after 1‐hour exposure. A 2‐log reduction in viable cell count was observed for S. aureus after 1 hour and a 4‐log reduction after 6 hours with 100 ppm nanosilver chitin membranes. This study demonstrates the antimicrobial capability of chitin membranes containing silver nanoparticles. The chitin membranes with 100 ppm nanosilver showed promising antimicrobial activity against common wound pathogens.

Development and evaluation of silver-impregnated amniotic membrane as an antimicrobial burn dressing.

Silver has been widely used as an antimicrobial agent in burn wound care. A number of dressings containing silver have been developed using textiles, polyurethane films, foams, hydrogels, and hydrocolloids. However, biological-derived wound dressings have been advocated for their ability to more effectively promote healing and regulation of evaporation and exudation at the wound site. An antimicrobial burn dressing was developed by impregnation of silver on the amniotic membrane. The dressing was assessed for antimicrobial effectiveness and physical properties of relevance to clinical performance. Silver-impregnated dressings exhibited antimicrobial activity in contact for 5 days. An in vitro evaluation of the microbicidal efficacy of the silver-impregnated dressing was performed using Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans with different contamination level. More than 95% reduction in viable counts was observed in 2 to 4 hours. The release of silver from the dressings was observed for up to 4 days. Moisture vapor transmission rate was 1037 ± 38 g/m2/24 hr for silver-impregnated dressings and 1024 ± 44 g/m2/24 hr for amniotic membrane. The fluid absorption by the silver-impregnated dressings was comparable to the amniotic membranes. The total fluid handling capacity of the silver-impregnated amniotic membrane dressing examined ranged from 4 to 6.6 g/10 cm2 in 24 to 96 hours. The silver-impregnated amniotic membranes also provided an effective barrier to bacterial penetration. The study has demonstrated the ability of silver-impregnated amniotic membrane to combat microbial infection and its ideal physical characteristics for clinical use as a burn wound dressing.

Radiation sterilization of tissue allografts: A review

Tissue substitutes are required in a number of clinical conditions for treatment of injured and diseased tissues. Tissues like bone, skin, amniotic membrane and soft tissues obtained from human donor can be used for repair or reconstruction of the injured part of the body. Allograft tissues from human donor provide an excellent alternative to autografts. However, major concern with the use of allografts is the risk of infectious disease transmission. Therefore, tissue allografts should be sterilized to make them safe for clinical use. Gamma radiation has several advantages and is the most suitable method for sterilization of biological tissues. This review summarizes the use of gamma irradiation technology as an effective method for sterilization of biological tissues and ensuring safety of tissue allografts.

Properties of Air Dried Radiation Processed Amniotic Membranes under Different Storage Conditions.

Amniotic membranes collected from the placentae of screened donors were processed, air dried and sterilized by gamma irradiation at 25 kGy. Effect of storage under different temperature and humidity conditions (10°C, RH 80–90%; 10°C, RH 40–50%; 40°C, RH 50–60% and 40°C, RH 10–20%) on the properties of the membrane were examined. Infrared (IR) spectral scanning was carried out to examine degradation or change if any in the tissue under different storage conditions. The degradation of amnion on irradiation with gamma rays or during storage after irradiation would tend to produce the relative variation in IR absorption troughs. This kind of addendum was absent in all the samples indicating no qualitative change in the material property of amnion. Water absorption and water vapour transmission rate (WVTR) of the membrane remained unchanged even after 6 months. No effect on the microbial permeability of membrane was observed during storage. The amniotic membranes were found to be impermeable to different strains of bacteria – Bacillus, Escherichia coli, Pseudomonas, Citrobacter, Flavimonas and Staphylococcus. The results indicate that amniotic membranes processed by air-drying are stable and can be stored under different environmental conditions without compromise to their clinical performance.

Polyvinyl pyrrolidone/carrageenan blend hydrogels with nanosilver prepared by gamma radiation for use as an antimicrobial wound dressing.

Hydrogels were prepared using polyvinyl pyrrolidone (PVP) blended with carrageenan by gamma irradiation at different doses of 25 and 40 kGy. Gel fraction of hydrogels prepared using 10 and 15% PVP in combination with 0.25 and 0.5% carrageenan was evaluated. Based on gel fraction, 15% PVP in combination with 0.25% carrageenan and radiation dose of 25 kGy was selected for the preparation of hydrogels with nanosilver. Radiolytic synthesis of silver nanoparticles within the PVP hydrogel was carried out. The hydrogels with silver nanoparticles were assessed for antimicrobial effectiveness and physical properties of relevance to clinical performance. Fluid handling capacity (FHC) for PVP/carrageenan was 2.35 ± 0.39–6.63 ± 0.63 g/10 cm2 in 2–24 h. No counts for Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, and Candida albicans were observed in the presence of hydrogels containing 100 ppm nanosilver after 3–6 h. The release of silver from hydrogels containing 100 ppm nanosilver was 20.42 ± 1.98 ppm/100 cm2 in 24 h. Hydrogels containing 100 ppm nanosilver with efficient FHC demonstrated potential microbicidal activity (≥3 log10 decrease in CFU/ml) against wound pathogens, P. aeruginosa, S. aureus, E. coli, and C. albicans. PVP/carrageenan hydrogels containing silver nanoparticles can be used as wound dressings to control infection and facilitate the healing process for burns and other skin injuries.

Sterilization of bone allografts by microwave and gamma radiation

Abstract Purpose: Bone allografts are used to enhance healing in osteotomies, arthrodesis, fractures and to replace bone loss resulting from tumour or trauma. However, a major concern associated with the bone allografts is the potential for disease transmission. Various sterilization techniques have been developed to prevent infection through allografts. This study was undertaken with the aim of exploring the use of microwave radiation for sterilization of bone allografts and to compare with gamma radiation sterilization. Materials and methods: Bone allografts were processed from femoral heads obtained from living donors. The effect of microwave and gamma radiation on the bacteria isolated from bone allograft was evaluated. The microwave radiation treatment was performed at 2450 MHz (frequency) for varying lengths of time at maximum power 900 Watts (W). Viability of three Gram-positive bacteria – Bacillus subtilis, Corynebacterium, Staphylococcus aureus and three Gram-negative bacteria – Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa was examined after irradiation of bacterial suspensions and contaminated processed bone allografts. The sterility test of microwave and gamma irradiated bone allograft was carried out in accordance with ISO (International Organization for Standardization) 11737-2. Results: Microwave irradiation (2450 MHz and 900 W) of bacterial isolates resulted in complete inactivation within 60 seconds. The contaminated bone samples showed no growth of organisms after 2 minutes of exposure to microwave irradiation. No viable counts were detected in bone grafts inoculated with Gram-negative bacterial species on gamma irradiation to a dose of 15 kGy. Bones contaminated with Gram-positive bacteria required a higher dose of 20 kGy for complete inactivation. Conclusions: The study shows that sterilization of contaminated femoral head bone allografts can be achieved by short exposure of 2 min to 2450 MHz and 900 W microwave radiation.

Use of gamma-irradiated amniotic membrane for the healing of split skin graft donor site

The management of split skin graft donor site is targeted towards promoting the healing process, while minimizing adverse effects and complications. The aim was to study the efficacy of gamma-irradiated amniotic membrane dressing for the healing of split skin graft donor site. Amniotic membranes isolated from the placenta were processed and sterilized by gamma radiation. Thirty patients with split skin graft donor site were included in the study. The average age of the patients was 33.33±16.45 years in study group and 38.93±18.52 years in control group. The average ulcer size was 92.8±66.2 cm2 in study group and 82.5±56.0 cm2 in control group. Processed amniotic membranes were applied just after taking split skin graft. Split skin graft donor site was assessed on day 8 and 12 for epithelialization, pain during change of dressing, discharge from donor site, status of healing and any adverse reactions. Significant (p < 0.0001) reduction in pain during change of amniotic membrane dressing as compared to conventional dressing was observed. The average per day rate of epithelialization on split skin graft donor site was 10.31% in the study group and 7.31% in the control group (p > 0.05). Significant (p < 0.001) enhancement in the healing of donor site was observed with amniotic membrane dressing as compared to the paraffin gauze dressing. The patients with processed gamma-irradiated amniotic membrane experienced no pain during change of dressing and improved epithelialization.

Chitin and chitosan: biopolymers for wound management

Chitin and chitosan are biopolymers with excellent bioactive properties, such as biodegradability, non‐toxicity, biocompatibility, haemostatic activity and antimicrobial activity. A wide variety of biomedical applications for chitin and chitin derivatives have been reported, including wound‐healing applications. They are reported to promote rapid dermal regeneration and accelerate wound healing. A number of dressing materials based on chitin and chitosan have been developed for the treatment of wounds. Chitin and chitosan with beneficial intrinsic properties and high potential for wound healing are attractive biopolymers for wound management. This review presents an overview of properties, biomedical applications and the role of these biopolymers in wound care.