Summary and conclusions

Transcription

1 Chapter 6 Wound which refers to a sharp injury damaging the dermis of the skin is a common problem in day to day life. Wound management is careful and accurate assessment of the wound with the use of proper wound care products which will help repair of an epithelial wound by enhancing scaling up of normal process of wound healing involving 4 stages such as hemostasis, inflammation, proliferation or granulation and remodeling or maturation. İn conventional wound management products, no single product is suitable for all wound types or at all stages of healing so development of new generation wound care products which will help at various stages of wound healing is an evolving field of research today. Based on available evidence and clinical experience, modern dressings do appear to have role at various stages of the wound healing process. Absorbable haemostats and hydrogel dressings are the part of modern wound management systems which help in haemostasis and moist wound healing by enhancing cell proliferation. In the research project presented in this thesis attempts have been made to design and develop following advanced wound management products to provide cost effective advanced wound management systems. 1. Absorbable haemostats 2. Haemostats to prevent postoperative infection 3. Drug loaded haemostats for postoperative analgesia 4. Hydrogel for moist wound healing 5. Antibacterial hydrogel for wound healing 6. Drug loaded hydrogels for moist wound healing with anesthetic effect Absorbable haemostat was prepared by crosslinking porcine gelatin by the process of Lyophilization. Preparation of Hydrogels was attempted by the process of chemical polymerization and γ-radiation polymerization. Gentamicin sulphate and Lidocaine HCl were used as model drugs for preparation of drug loaded absorbable haemostats and hydrogels. The research work presented is summerised in following sections. Design and development of surgical dressings for advanced wound management 254

2 2A. Preformulation and standardization of drugs and excipients Physicochemical characterization of drugs and excipients used during present research work was carried out to assess their quality, suitability and compatibility as described in chapter 2A. Gentamicin sulphate and Lidocaine HCl were standardized as per IP 2007 and were found to comply with compendial specifications. Gelatin was characterized as per IP 2007, PVA as per USPXXII, 1990, formaldehyde and glutaraldehyde were standardized as per the respective monographs in BP Results of organoleptic characterization and identification tests complied with compendial specifications. Drug excipients compatibility was studied by comparing FTIR and DSC results of GS, LH, Gelatin and PVA. Presence of chemical functional groups at different wavelengths in FTIR spectra of individual drugs and excipients confirmed that there was no overlap of chemical structure of the drug and excipients. Endotherms of GS, LH and other excipients indicated no overlap; hence no drug excipients interactions were predicted, this indicated compatibility. Effect of gamma radiation on GS and LH was evaluated by comparing FTIR of original drugs with FTIR spectra of drugs after gamma irradiation [Figure 2.9; 2.10]. No change in peak position and intensities indicated that there was no change in chemical compositions after irradiation by gamma radiations. 2B Analytical method development 2B.1 Development of analytical method for Lidocaine HCl UV-visible spectrometric and HPLC methods were developed and validated for analysis of LH in developed formulations. 2B.1.1 UV-Visible spectrophotometric method for estimation of LH LH dissolved in phosphate buffer ph 7.4 was scanned at UV range of nm. The λmax for LH was found to be 263nm [Figure 2.11]. The method was validated so that it could be used for routine analysis of formulations. The method was found to be linear with R 2 value of [Figure 2.12] and accurate with % recovery of %w/w for analysis of LH in formulations. Design and development of surgical dressings for advanced wound management 255

3 2B.1.2 HPLC method for estimation of Lidocaine HCl HPLC method for estimation of LH described in USP was validated for precision, linearity, limit of detection, limit of quantification, intermediate precision and accuracy. HPLC method was developed using HiQsil C18HS column (4.6mmØ x 250 mm) 2.5 µm with mobile phase of [930ml water+50ml Glacial acetic acid (ph 3.4)] : Acetonitrile (4:1) with flow rate of 1 ml/min. LH eluted at retention time of 12.5 minutes was detected by UV detector at 254nm. HPLC method was validated for linearity, precision, accuracy. The method was found to be precise in the concentration range of μg/ml with % RSD of LOD and LOQ of LH were found to be 2μg/ml and 5μg/ml. HPLC method was linear with R 2 value of ± %RSD of [Table 2.11] and accurate with percent recovery 99.41% ± %RSD of 0.14[Table 2.14]. 2B.2 Colorimetric method of estimation of gentamicin sulphate Gentamicin poorly absorbs ultraviolet and visible light; an indirect spectrophotometric method suggested by P. Frutos, Susana Torrado et al using ninhydrin as colorimetric reagent was developed and validated. The method was validated for ninhydringentamicin reaction by evaluating effect of concentration of ninhydrin and heating time for completion of colorimetric reaction. Absorbance of colored complex of ninhydringentamicin was measured at 324nm. The method was found to be linear [R 2 =0.9984] in the concentration range of μg/ml of GS, 2.5mg/ml of ninhydrin reagent and 15 minute of heating time at 95 o C in phosphate buffer ph A. Development of absorbable gelatin sponges as biodegradable haemostats Absorbable gelatin sponges were prepared by lyophilizing crosslinked foam of natural polymer, gelatin using formaldehyde as crosslinking reagent. The formulations were optimized to get pore size in the range of μm, wall thickness of 3-5μm, digestibility in pepsin in <75 minutes, water absorption >35x of initial weight and residual formaldehyde <0.001%. Design and development of surgical dressings for advanced wound management 256

4 3A.1 Optimization and characterization of gelatin foam The developed sponges were optimized for concentration of gelatin and whipping conditions such as time and speed of stirring in terms of pore size and wall thickness. The properties and stability of gelatin foams as a function of gelatin concentration, its ph, concentration of crosslinking agent and conditions of whipping process were also evaluated. Gelatin foam was optimized for foam volume, foam uniformity, foam stability and apparent foam density. Effect of gelatin and formaldehyde concentrations on pore size and wall thickness of sponges was determined by using surface response curve methodology. Stable homogenous gelatin foams with small ( μm) size pores were achieved from gelatin concentration of 5% w/v of at ph 7.5, formaldehyde concentration of 0.3%w/w and whipping at rpm. The produced sponges had desired characteristics as described in section 3A.1 under chapter 3A. 3A.2 Drying of absorbable gelatin sponges by Lyophilization Lyophilization cycle for drying of gelatin sponge was developed by optimizing time and temperature of freezing, primary drying and secondary drying. Primary drying temperature was decided by determining glass transition temperature (Tg) with the help of DSC studies to prevent collapse of porous structure of formulation. Desired characteristics of gelatin sponges were obtained at -35 o C of freezing temperature, -50 o C of drying temperature at vacuum of 2mbar. Primary drying time for gelatin sponge was found to be 12 hrs and it took 16hrs for completion of secondary drying as described in section 3A.2 under chapter 3A. 3A.3 In vitro characterization of developed formulations Developed formulations were evaluated for appearance and physical characteristics, loss on drying, water absorption, morphology, residual formaldehyde content, digestibility, FTIR and degree of crosslinking. Developed formulations of gelatin sponges were white, porous in nature with pore size in the range of μm, wall thickness 3-5μm, 10% LOD, digestible within 15 minutes and capable of absorbing water times of the weight. Design and development of surgical dressings for advanced wound management 257

5 3A.4 Sterilization of gelatin sponges Sterilization of developed formulations was carried out by gamma radiation technique at dose of 2.4Mrad. The effect of gamma radiation sterilization on gelatin sponges was determined by comparing the characteristics of gelatin sponges before and after sterilization as described in section 3A.3.2 under chapter 3A. The radiation method showed no change in the characteristics of the sponges so this method can be employed for sterilization of surgical sponges and product was found to be sterile when checked by sterility test IP. 3A.5 In vitro biodegradation of gelatin sponges In vitro biodegradation of developed formulations was investigated in pepsin solution to check biocompatibility of the material as described in section 3A.3.3. It was observed that developed plain gelatin sponge gets totally degraded in 72 hours. The characteristics of developed sponges were compared with similar products available in local and international market, AbGel and Surgifoam sponges. The developed sponges were comparable with marketed products in terms of physicochemical characteristics. 3A.6 Scale up and reproducibility studies Scale up studies for production of absorbable gelatin sponges were carried out at two stages viz. Pilot scale and Commercial scale from the optimized laboratory scale on the basis of 20 pieces and 60 pieces of 8x5x1cm size of gelatin sponges per cycle. The study was divided into two major steps of Formulation process scale up and Lyophilization process scale up as described in section 3A.4 in chapter 3A. Formulation process scale up The formulation process was optimized to get stable foams with apparent foam density less than 400mg/ml and foam volume up to 4-5ml/mg by varying the concentrations of gelatin, crosslinking agent and whipping conditions. Manufacturing vessel and stirrer were designed to maintain geometric similarity with laboratory scale. Stable homogenous gelatin foams with small (80-120μm) size pores were produced at gelatin concentration of 5% w/v at ph 7.5 and formaldehyde concentration of 0.3mg/ml. whipping duration of 15 minutes was needed for stage 1and 30 minutes for stage 2 of production. Design and development of surgical dressings for advanced wound management 258

6 Lyophilization process scale up Lyophilization process was optimized to get desired end point by optimizing freezing temperature, freezing time, drying temperature and drying time. Freezing temp of - 35 o C, condenser temp of - 50 o C and heater temp of + 50 o C were found to give white, soft gelatin sponges with pore size in the range of μm, μm wall thickness, times water absorption. Lyophilization cycles applicable for both the scale up stages were found o be similar. Complete drying of gelatin sponges at both the stages of scale up was observed within 16hrs of Lyophilization. Depending on the requirement of quantity of the product, drying chamber of lyophilizer for commercial scale was designed as described in section 3A in chapter 3A. All the scale up batches showed good batch to batch reproducibility. Final products of gelatin sponges were packed in double envelopes and then in cartons to protect from environmental conditions and were subjected to gamma radiation sterilization at the dose of 2.4Mrad. 3B. Development of sustained release drug loaded absorbable gelatin sponges Sustained release drug loaded gelatin sponges were prepared by incorporating biodegradable, drug loaded microspheres of drug into the sponges. Gentamicin sulphate and Lidocaine HCl were selected as drug candidates for development of formulations. 3B.1 Development of biodegradable microspheres The drugs, lidocaine HCl and gentamicin sulphate were encapsulated separately by using emulsion chemical crosslinking method and gelatin as biodegradable polymer. 3B.1.1 Development of blank microspheres Blank microspheres were prepared to optimize the % yield, appearance, particle size, shape and surface characteristics and percent water content of formulations. Gelatin concentrations of 0.25, 0.5 and 1% with formaldehyde concentration of 0.3% at stirring speed of rpm were found to give spherical, hardened microspheres with μm particle size and % yield within range of 80-90% as described in section 3B.1. Design and development of surgical dressings for advanced wound management 259

7 3B.1.2 Preparation and Evaluation of Drug loaded Microspheres For evaluation of drug loaded microspheres, developed analytical methods for estimation of drug content and in vitro release profiles were evaluated for non-interference of excipients as described in section 3B B.1.3 Preparation of gelatin: GS loaded microspheres GS microspheres were prepared from 1g gelatin and 500mg of GS resulted in 67% of drug entrapment and 88% yield. LH microspheres were prepared using 1g gelatin and 500mg of LH and 72% of drug entrapment and 88% yield as obtained. Drug release profiles of GS and LH microspheres were investigated using Flow Through cell apparatus in phosphate saline buffer, ph 7.4. The microspheres showed nonlinear release profiles and failed to sustain the release for more than 4 and 3 hrs respectively. Gelatin along with another natural, biodegradable polymer sodium alginate in combination was hence tried to sustain drug release as described in section 3B.3. 3B.1.4 Formulation development of gelatin: sodium alginate drug loaded microspheres Microspheres of GS and LH were prepared using gelatin along with sodium alginate for retarding the drug release. GS microspheres prepared with 1% gelatin, 0.5% sodium alginate and 500mg of GS were found to give percent yield of 90% with 70% drug entrapment. LH microspheres were prepared using 1% gelatin, 0.5% sodium alginate and 500mg of LH to give percent yield of 91% with 76% of percent entrapment. The drug release kinetics of GS and LH microspheres showed sustained release for 8 and 10 hrs respectively following zero order drug release with Higuchian diffusion mechanism. Levels of residual solvents acetone and isopropyl alcohol in final microspheres formulation were well below the acceptable limits given in European Pharmacopoeia limits, Version IV. Optimized formulations were further incorporated into gelatin sponges for development of sustained release, GS and LH loaded biodegradable haemostats. 3B.2 Incorporation of microspheres into biodegradable sponges GS and LH loaded gelatin sponges were prepared by incorporating 100mg of optimized microspheres in 5% of aqueous gelatin solution and crosslinking with 0.06% and 0.05%w/w formaldehyde. The resulting stable foams were lyophilized with optimized Lyophilization cycle as described in section 3A.4.3. The drug loaded sponges were further characterized for morphology, LOD, digestibility, dissolution medium uptake Design and development of surgical dressings for advanced wound management 260

8 capacity, residual formaldehyde content, pore size, wall thickness, drug content and drug release using Franz diffusion cell and in vitro biodegradation profile. 3B.2.1 GS loaded sponges GS loaded sponges were pale yellow and porous with visible microspheres in the matrix, μm pore size and 3-5μm wall thickness. They showed 10% LOD, digestible within 75 minutes with dissolution medium absorption capacity of 40-50%w/w and residual formaldehyde content less than 0.001%w/w. Drug content of the formulation was 97% and sponges able to sustain the drug release upto 6hrs which followed first order release kinetics with Higuchian diffusion. 3B.2.2 LH loaded sponges LH loaded sponges were off white in colour, porous with visible microspheres in the matrix with μm pore size and 3-5μm wall thickness. They showed 8% LOD, were digestible within 80 minutes and had dissolution medium absorption capacity of 40-50%w/w and residual formaldehyde less than 0.001%w/w. Drug content of the formulation was 96% and sponges were able to sustain the drug release upto 8hrs with Higuchian diffusion following first order release kinetics. GS and LH loaded sponge were found to biodegrade in vitro within 72 hrs leaving soft gelatinous mass as remnants of microspheres in biodegradation medium which also degraded completely within 80 hrs. 4A. Development of hydrogel formulations Hydrogel formulations were attempted by polymerizing PVA along with carrageenan as natural polymer (NP) by chemical and gamma radiation polymerization. Hydrogel formulations prepared were characterized for morphology, swelling behaviour, mechanical properties, sol-gel analysis, FTIR, microbe penetration test and sterility. 4A.1 Preparation of hydrogels by chemical polymerization Chemical polymerization of PVA was tried with glutaraldehyde reagent as crosslinking agent. Hydrogel formulations with 10% PVA, 1%NP and 0.3% formaldehyde resulted in chemically crosslinked hydrogels with 205 of maximum swelling and 450kPa tensile strength as described in chapter section. Design and development of surgical dressings for advanced wound management 261

9 The hydrogel sheet formed after chemical polymerization was non-transparent and involved tedious method for washing up of crosslinking agent. Tensile strength of 450kPa is far lower than failure strength of skin 30mPa so this hydrogel were not applicable for wound management. Therefore, the process of chemical polymerization was not carried further and radiation polymerization was attempted. 4A.2 Preparation of hydrogels by radiation polymerization Radiation polymerization of PVA was tried with gamma radiations emitted by 60 Co. Formulations with 10% PVA, 1% NP and 0.1KCl at gamma radiation dose of 25kGy resulted in formulation of transparent, flexible polymerized hydrogel sheets. The ph of aqueous extract of hydrogel sheet formed was found to be 5.7. Mechanical strength of developed hydrogel was observed to be1650kpa with 85% gel fraction with maximum swelling of 205% exhibiting superabsorbent property. Presence of O-H stretching at 3404 to 3416cm -1 in FTIR indicated presence of intermolecular hydrogen bonded hydroxyl groups having polymeric association resulting in good water holding capacity. Microbe penetration test showed that neither S. aureus nor E. coli passed through the hydrogel dressing as described in section Scale up of the hydrogel formulation was attempted 5 times of the laboratory batch size. All the scale up batches showed good batch to batch reproducibility with respect to gel fraction, mechanical properties, swelling behaviour and microbe penetration test. 4B Development of drug loaded hydrogel Optimized formula for hydrogel from section was used to prepare drug loaded hydrogels as described in section 4B. 4B.1 GS loaded hydrogels Formulations with 10% PVA, 2% NP, 0.25mg/ml GS resulted in yellow coloured hydrogels with maximum swelling of 180% and 1300kPa of tensile strength. Breaking of hydrogel film was observed after swelling for 150 minutes. GS loaded hydrogels were not polymerized properly even at the higher doses of gamma radiation or with addition of plasticizer. This may be due to presence of high concentration of amino acids in GS would have hindered polymerization process. Design and development of surgical dressings for advanced wound management 262

10 4B.2 LH loaded hydrogels Formulations with 10%PVA, 2%NP, 2mg/ml LH and 1%KCl were found to give transparent, flexible polymerized hydrogel sheets with ph 6.1, gel fraction 87%, drug content 97%, and tensile strength of 1720kPa with maximum swelling of 207%. FTIR spectra confirmed drug entrapment in hydrogels. Drug release kinetics of LH loaded hydrogels was investigated by calculating Fractional Drug Release (FDR). The release kinetics for first 60 minutes showed typical Fickian diffusion behaviour with n values of 0.5 characterized by a linear increase in the release rate of LH as a function of the square root of time. The gels displayed non-fickian (anomalous) diffusions kinetics with n value of 0.9 for further release of LH upto 8hrs indicating sustained drug release behaviour as described in figure 4.23a; 4.23b. Microbe penetration test proved that LH loading in hydrogel dressing does not affect microbial barrier properties of hydrogel dressing. 5A Stability studies as per ICH guidelines For stability studies on selected formulations, the products were classified prior to subjecting to stability conditions in two parts such as stability studies for existing formulations and new formulations. 5A.1 Stability testing of existing formulations As per IDMA-APA guidelines which are modeled parallel to the ICH guideline Stability testing of new drug substances and products and essentials from WHO guidelines and other international guidelines on stability studies. Absorbable gelatin sponges and hydrogels were stored at 30 o C±2 o C /65% RH±5% for the period of 12 months and 40 o C ±2 o C /75% RH±5% for the period of 6 months. Formulations were regularly assessed for physicochemical parameters like appearance, moisture content, water absorption, biodegradation time and sterility as described in chapter. Data was statistically analyzed and no significant changes were observed during storage period. Shelf life of the product hence could be predicted to be 2years as per IDMA-APA guidelines. Design and development of surgical dressings for advanced wound management 263

11 5A.2 Stability testing of new products Selected formulations of GS and LH loaded sponges and LH loaded hydrogels were subjected to stability studies as per ICH guidelines and stored at 25 o C ±2 o C /60% RH±5%, 30 o C±2 o C /65% RH±5% and 40 o C ±2 o C /75% RH±5% for a period of 6 months. GS and LH loaded sponges were regularly assessed for physicochemical parameters like appearance, moisture content, water absorption, biodegradation time, sterility and drug content. LH loaded hydrogels were regularly assessed for gel fraction, water absorption, tensile strength and sterility of the formulations as described in chapter 5B. Data was statistically analyzed and no significant changes were observed during storage. Shelf life of the products hence could be predicted to be 2years as per ICH guidelines. 5B Preclinical studies on Absorbable gelatin sponges and Hydrogel formulations Preclinical studies on absorbable gelatin sponges and hydrogels were carried out by taking into consideration initial evaluation tests for application of medical devices as per ISO These guidelines describe biological evaluation of medical devices as per International Standard. 5B.1 Skin irritation testing Skin irritation test was carried out to determine applicability of developed products on wounds by evaluating primary skin irritation potential in accordance with the guidelines of the Consumer Product Safety Commission, Title 16, Chapter II, Part Dermal irritation potential of the selected formulations on intact and abraded skin of the rabbits was assessed by calculating primary skin irritation index. The back of the animals was clipped free of fur with a clipper before application of the sample, four parallel epidermal abrasions were made on the back of animal with a sterile needle at one test site while the skin at the opposite site remained intact. A 1cm 2 sheet of the developed product was then applied to each site. The samples of products were backed with polyurethane film [PU film]. At 24 and 72 hours after test article application, the test sites were examined for dermal reactions in accordance with the FHSA recommended Draize scoring criteria. The Primary Irritation Index (P.I.I.) of products was calculated following test completion. As defined in CFR16, Chapter II, Part Design and development of surgical dressings for advanced wound management 264

12 1500. The Primary Irritation Index of the all the products was calculated to be 0.00; no irritation was observed on the skin of the rabbits after application of test samples. All other preclinical studies on developed formulations were performed using Wistar rats as per protocol approved by animal ethical committee of C. U. Shah College of Pharmacy and Bombay veterinary college, Mumbai as described in Chapter 5A. 5B.2 Absorbable gelatin sponges Extent of haemostasis, Biodegradation after implantation and Wound healing capacity were investigated for assessment of in vivo activity of absorbable gelatin sponges. Haemostasis potential of selected formulations of absorbable gelatin sponge was assessed by modified Duke test method. Small incisions (5x1mm deep) were made on the back of Wistar rats with a disposable lancet after ketamine anesthesia. Incision sites were blotted every 15 seconds with gelatin sponge in animals of group I and with cotton gauze in group II. Time to stop bleeding completely was measured and compared. Gelatin sponges achieved complete haemostasis after 1 minute without further bleeding at the incision site; whereas incision sites where cotton gauze was used showed slow oozing even after 4 minutes. In vivo biodegradation of absorbable gelatin sponge was investigated by implanting the gelatin sponges subcutaneously. The rats were sedated with xylazine and anaesthetized with ketamine. The operative site was prepared on the right flank aseptically and incision (15x10mm deep) was made on the right flank to prepare subcutaneous pouch. Gelatin sponges were placed on the experimentally created subcutaneous pouch. The skin incision was sutured with interrupted nylon sutures and observed by reopening the wound after every 7 th, 14 th and 21 st day of operation. They showed complete biodegradation within 21 days of subcutaneous implantation. Wound healing activity of selected formulations was assessed by implanting the formulations in a highly prefused organ, kidney. The rats were anaesthetized under xylazine sedation and ketamine anesthesia. The operative site was prepared on the right flank aseptically. The incision was taken on the right flank and the greater curvature of right kidney was exteriorized. Gelatin sponge was placed aseptically on the experimentally created wound on the kidney. The kidney along with gelatin sponge was Design and development of surgical dressings for advanced wound management 265

13 repositioned in visceral cavity and the muscle incision was sutured with catgut and skin incision was sutured with interrupted nylon sutures. The wounds were observed for gross necropsy. Histopathological studies were carried out to determine growth of granulation tissue which determined wound healing potential of gelatin sponges. Greater increase in granulation tissues compared to control group indicated that gelatin sponges played role in wound healing as shown in Histopathological observations in figure B.3 Hydrogels Wound healing efficacy of hydrogels was also investigated using excision wound model as described in chapter 5B. Rats were anesthetized separately with ketamine and excision wound of 1x1cm was prepared on the back of Wistar rat. Hydrogel patch was applied to the wound site with the help of PU film. The areas of the wounds were calculated using a graphical method for 4, 6, 12, 16 and 18 days of operation. Wound area analysis after treatment with hydrogel showed complete epithelialization of wound within 15 days which was less than that of control of 18days with treatment with cotton gauze [Figure 5.17]. Histopathological study showed that the wounds treated with PVA hydrogels showed mild inflammatory cells and mild chronic infiltration of the inflammatory cells in the dermal layer, compared to the control wounds [Figure 5.18]. Limitations and scope of future work Various approaches for advanced wound management via formulation development of absorbable gelatin sponges and hydrogels have been investigated in the present research work. The work can be extended towards development of sustained release absorbable gelatin sponges and hydrogels that releases the drug continuously for six to seven days for modern wound management. The novel element silver can be incorporated in developed formulations for antibacterial wound healing and minimize bacterial resistance. Accurate dosing of drug substance into developed sponge formulations is difficult to achieve for particular wound area since type and size of injury varies. Clinical studies on Human volunteer studies using drug loaded formulations need to be carried out to elucidate better efficacy and safety. Design and development of surgical dressings for advanced wound management 266

14 Conclusions Absorbable gelatin sponges Absorbable, porous and biodegradable gelatin sponges were developed using porcine gelatin using the process of Lyophilization and evaluated for in vitro characterization and in vivo safety and efficacy. The developed haemostatic sponges exhibited similar properties and haemostatic capability as sponges available in market. The biocompatibility and biodegradation of gelatin sponges after subcutaneous and renal implantation proved their potential as biodegradable haemostatics. Sustained release antibiotic and anesthetic sponges were developed by incorporating biodegradable microspheres of Gentamicin sulphate and Lidocaine HCl prepared by emulsion chemical crosslinking process using gelatin and sodium alginate polymer. Sodium alginate has a potential role in prolonging the drug release from microspheres. GS loaded sponges exhibited sustained release of drug for 6 hrs and LH loaded sponges showed sustained release for 8 hrs. The developed sponges showed biodegradation within 80hrs in vitro in pepsin solution. Drug loaded gelatin sponges did not show potential for skin irritation when evaluated by Draize patch test. Hydrogels Hydrogels were developed using PVA and natural polymer carrageenan by gamma radiation polymerization technique. Developed formulations showed properties to meet the requirements of an ideal wound dressing. The developed hydrogels can absorb fluids effectively, exhibit high elasticity with good mechanical strength and transparency, allowing observations of healing process. The hydrogels could prevent microbial infection as observed from microbe penetration test. Hence developed hydrogels were found convenient to be used as wound dressing. Comparative Histopathological studies and morphometric analysis after excision wound healing studies confirmed that hydrogels could facilitate healing of excision wounds in terms of epidermal healing rate. Design and development of surgical dressings for advanced wound management 267

15 Sustained release Lidocaine HCl loaded hydrogels showed their potential as drug carriers. Hence, such formulations could be tried for various biomedical applications as drug delivery systems and moist wound dressings. The selected drug loaded formulations of gelatin sponges and hydrogels were found to exhibit no significant changes in physicochemical properties for 6 months at accelerated temperature and humidity conditions. Shelf life of the selected plain gelatin sponges and hydrogels was predicted for 2years as per ICH guidelines. Developed surgical dressings exhibited desired biocompatibility, efficacy, less toxicity and have potential for advanced wound management. Design and development of surgical dressings for advanced wound management 268