OPTIMAL ELECTRO-CHEMICAL ENHANCEMENT OF TRANSDERMAL INSULIN DELIVERY USING POLYACRYLAMIDE BASED HYDROGEL PATCHES

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1 OPTIMAL ELECTRO-CHEMICAL ENHANCEMENT OF TRANSDERMAL INSULIN DELIVERY USING POLYACRYLAMIDE BASED HYDROGEL PATCHES by AMIT KUMAR CENTRE FOR BIOMEDICAL ENGINEERING sithmitted In fulfillment of the requirements of the degree of DOCTOR OF PHILOSOPHY to the INDIAN INSTITUTE OF TECHNOLOGY, DELHI August, 2004

2 Th CiS 3C,/ O is I. T. LLL1 AMY [LIRR

3 CERTIFICATE This is to certify that the thesis entitled "OPTIMAL ELECTRO- CHEMICAL ENHANCEMENT OF TRANSDERMAL INSULIN DELIVERY USING POLYACRYIAMIDE BASED HYDROGEL PATCHES" bein submitted by Mr. Amit Kumar to Indian Institute of Technology, Delhi, for the award of "DocroR PiilLosoptrv", is a record of bonalide research work carried out by him. Mr. Amit Kumar has worked under our guidance and supervision and has fulfilled the requirements for the submission of this thesis, which to our knowledge has reached the requisite' standard. The results contained in this thesis are original and have not been submitted, in part or :lull, to any other University or Institute for the award of any other degree or diploma. Centre for Biomedical Engineering, Indian Institute of Technology, New Delhi, India Dr. Veena Koul, Assistant Professor, Centre for Biomedical Engineering, Indian Institute of Technology, New Delhi, India Date: 30 th August, 04 Date: 30 th August, 04

4 ACKNOWLEDGEMENTS I feel honored to acknowledge my immense gratitude to my supervisors Prof Such Anand and Dr. Veena Koul for their excellent supervision, immense motivation, constant support, and keen interest throughout the research period. Their constant vigil, which was always full of affection and dedication, helped me in the completion of this work. I was greatly benefited by their vast and practical experience. It is my great privilege to thank Prof. Harpal Singh, Head of the Department, Centre for Biomedical Engineering (CBME), IIT, Delhi for providing necessary research facilities. I feel pleasure in expressing my sincere thanks to Dr. Amit Dinda, Department of Pathology, AIIMS, Delhi for his cooperation in carrying out histopathology studies. I acknowledge the co-operation and help provided by Prof. Roop Kishen Khar and Dr. Farhan, Faculty of Pharmacy, Jamia Hamdard, to carry out DSC at their premises. I am thankful to Mr. Raieev Yadav, CBME, IIT Delhi for his help in fabrication of iontophore.tie delivery system. I wish my special and sincere thanks to Dr. Mohammed Changez, Dr. Burugapalli Krishna and Mrs. Rachna Prasad, Biosensor Lab, CBME, IIT, Delhi for their co-operation, encouragement and consistent help. I am greatly thankful to Mr. Devender Gupta, CBME, IIT Delhi. for recording FT-IR spectra and Ms. Pushplata, CBME, IIT Delhi, for her help in the laboratory at various stages of experimental work. Thanks are due to Mr. Anil Pandey, Biosenor Lab, CBME, IIT Delhi for his assistance through out research work in general and especially for his help in animal handling. I would like to express my special thanks to Dr. Raj eev Raghuvanshi, Associate Director, NDDS, Ranbaxy Research Laboratories for his encouragement and cooperation during thesis writing.

5 I cannot fail to mention the love, care, wholehearted support and encouragement provided by my parents and family members during my research work. Their sacrifices, affection, inspiration and blessings made me what I am today. Last, but not the least, mere words may not express my loving acknowledgement for my wife Dr. Shikha Kumar, for her constant inspiration, moral support, valuable suggestions and every possible help in completion of my studies successfully. But for all, I thank God, whose divine grace was never slow. Date: 30th August, 04 (AMIT KUMAR)

6 ABSTRACT Diabetes mellitus is metabolic disorder characterized by high blood..., ',, glucose concentration. It affects about 150 million people worldwide out of which 20 million are in India. Protracted hyperglycemia leads to irreversible changes at cellular and organ level. Multiple insulin injection therapy is not clinically acceptable. Among the various alternative approaches transdermal route of delivery is the most attractive option due to patient acceptance and lesser proteolytic enzyme activity of skin. However, large molecular size, charge and hydrophilicity of insulin limits absorption through this route. Transdermal iontophoresis, which uses mild electric current to facilitates the transport of charged molecules. In the present thesis a comprehensive approach has been adopted to overcome the problems associated with existing ionotophoretic techniques. A biocompatible polyacrylamide based hydrogel patch was synthesised with model properties to load desired levels of insulin. The hydrogel patches were evaluated for insulin content, croqslinker concentration, co-polymerisation, and LPN with gelatin. Finally, polyacrylamide patch with 0.5 mole % cross-linking concentration and 30IU of insulin loading was selected on the basis of its swelling behavior and drug release characteristics. In vitro studies with mice skin interface were optimised for intensity, frequency and waveshape. A programmable mable ionotophoretic device was laboratory designed and fabricated to accommodate all the abovementioned requirements. Electromotive flux with

7 current density of 0.38 majcm2 at lkhz sine wave provided the best choice for ionotophoretic flux for insulin permeation, followed by triangular, square (Duty cycle 50%), exponential exp20 and DC. In vitro! in vivo correlation (0.93) was established by studies on mice. In vivo pharmacodynamic parameters like, Rmax (maximum reduction in %BGL) and AAC (Area Above time versus % reduction in BGL Curve) were studied and a linear correlation was established for both the parameters. The desired BGL could not be achieved by ionotophoresis alone. Pretreatment of skin by GRAS chemical enhancers for short duration was carried out. Skin pretreatment with neat ethanol, ethyl acetate or glycerol followed by iontophoresis (sine, 1kHz, 0.38 ma/cm2) did not elicit sufficient enhancement. Enhancers having independent properties of lipid extraction and forming creating aqueous channels were tried. This two-tier system (E-1 and E-2), containing above enhancers in different combinations and proportions were evaluated. The enhancement in insulin permeation after enhancer treatment was 86% and 191% for E-1 and E-2 respectively. However, when compared with DC iontophoresis alone the enhancement comes out to be 390% and 441% respectively. A rapid fall in blood glucose level was maintained for over 6h in STZ-diabetic mice. Lower level of blood glucose was maintained for additional two hours, when a single formulation (E-3) was employed. An enhancement in insulin permeation obtained was 222% when compared to sine iontophoresis alone and 576% when compared to DC iontophoresis. The histopathological studies on in vivo skin samples treated with DC iontophoresis revealed maximum tissue reaction with total irritation score of 11.

8 However, the studies conducted on the enhancers alone or in combination to sine iontophoresis revealed lesser tissue reaction like thinning of epidermis, mild vascular changes, mild spongiosis and moderate oedema. All these tissue reactions were temporary and complete reversibility was obtained within 48h. SEM demonstrated wider appendageal pathway after iontophoresis treatment compared to control skin. FT-IR of in vitro and in vivo skin samples demonstrated increase in ratio between amidel and amide 2, which indicates hydration level of skin, after iontophoresis. The ratio was maximum, 1.90, for sine iontophoresis and minimum, 1.29, for DC iontophoresis. Further skin FT-IR after enhancer treatment showed shift in.vyin and c.r,sym CH stretching frequency towards higher levels and indicates lipid acyl chain mobility and extraction. DSC of skin samples after sine iontophoresis treatment demonstrated disorganization of lipid protein domains, whereas DC and sqr50 clearly demonstrated the extraction of intercellular lipids without affecting keratin of SC. The present study has lead to therapeutic levels of insulin permeation via transdermal route by synergistic combination of sine ionotophoresis and GRAS chemical enhancers.

9 CONTENTS List of Figures List of Table V CHAPTER 1: INTRODUCTION AND LITERATURE REVIW INTRODUCTION DIABETES MELLITUS A COMMON DISEASE Classification, causes and symptoms of diabetes Insulin Insulin Treatment TRANSDERMAL DRUG DELIVERY Skin Barrier to transdermal drug delivery Routes of penetration Facilitated transdermal drug delivery Transdermal insulin delivery IONTOPHORETIC DELIVERY OF PEPTIDES Human clinical data Factors effecting peptide delivery Effect of patch variables on peptide delivery HYDROGELS FOR IONTOPHORETIC APPLICATION Hydrogels Swelling behaviour of hydrogels 35

10 Kinetics of swelling Factors affecting the swelling of a hydrogel Application in iontophoresis OBJECTIVES PLAN OF WORK 40 CHAPTER 2: SYNTHESIS AND EVALUATION OF HYDROGEL MATRIX FOR DRUG DELIVERY 2.1. INTRODUCTION EXPERIMENTAL Materials Synthesis of hydrogels Preparation of transdermal patches RESULTS AND DISCUSSION Characterization of hydrogels Characterization of transdermal patches CONCLUSIONS 59 CHAPTER 3: IN VITRO OPTIMISATION OF ELECTRICAL AND CHEMICAL PARAMETERS FOR ELECTROMOTIVE DELIVERY OF INSULIN 3.1. INTRODUCTION 3.2. EXPERIMENTAL Materials Selection of electrode

11 lontophoresis instruments Skin preparation In vitro iontophoresis Insulin analysis Synergistic studies RESULTS AND DISCUSSION Hydrogel optimization Optimization of electrical parameters Synergistic iontophoresis with chemical enhancer CONCLUSIONS 90 CHAPTER 4: SYNERGISTIC STUDY ON INDUCED DIABETIC MICE AND TISSUE COMPATIBILITY STUDIES 4.1. INTRODUCTION EXPERIMENTAL Materials Induction of diabetes in mice In vivo iontophoresis Synergistic studies Patch skin compatibility testing Histopathology of skin Data presentation RESULTS AND DISCUSSION 103

12 In vivo iontophoresis Synergistic study Patch skin compatibility Histopathological study CONCLUSIONS 120 CHAPTER 5: MECHANISM OF INSULIN PERMEATION WITH ELECTRO- CHEMICAL ENHANCER 5.1. INTRODUCTION 5.2. EXPERIMENTAL SEM of slcin FT-IR of skin DSC of skin 5.3. RESULTS AND DISCUSSION Transport number SEM of skin FT-IR of skin DSC of skin 5.4. CONCLUSIONS CHAPTER 6: SUMMARY, CONCLUSION AND SUGGESTION FOR FUTURE WORK 6.1. SUMMARY Introduction

13 Synthesis and evaluation of hydrogel matrix for drug delivery In vitro optimisation of electrical and chemical parameters for 146 electromotive delivery of insulin Synergistic study on induced diabetic mice and tissue 149 compatibility studies Mechanism of insulin permeation with electro-chemical enhancer CONCLUSIONS SUGGESTION FOR FUTURE WORK 154 REFERENCES 157