Radiation induced hydrophilic polymers for biomedical applications

RADIATION INDUCED HYDROPHILIC POLYMERS FOR BIOMEDICAL APPLICATIONS

by

HARPAL SINGH

Centre for Biomedical Engineering

thesis submitted in fulfilment of the requirements of the degree of

DOCTOR OF PHILOSOPHY

to the Indian Institute of Technology, Delhi

Department of Textile Technology Indian Institute of Technology, Delhi

September, 1981

CERTIFICATE

This is to certify that the thesis entitled

"RADIATION INDUCED HYDROPHILIC POLYMERS FOR BIOMEDICAL APPLICATIONS" being submitted by Mr. Harpal Singh to the Indian Institute of Technology, Delhi for the award of the Degree of DOCTOR OF PHILOSOPHY in the Department of Textile Technology, is a record of bonafide research carried out by him. Mr. Harpal Singh has worked under our guidance and supervision and has fulfilled the requirements for the submission of the thesis.

The results contained in this thesis have not been submitted, in part or in full, to any other University or Institute for the award of any degree

or diploma.

1 ⁴⁵

( Dr. Alok Ranjan Ray ) Thesis Supervisor

Centre for Biomedical Engineering Jndian Institute of Technology,

New Delhi-110 016.

( Dr. Padma Vasudevan ) Thesis Supervisor Centre for RD and AT

Indian Institute of Technoloc New Delhi-110 016.

ACKNOWLEDGEMENTS

I wish to express my deep sense of gratitude to Dr. (Mrs.) P. Vasudevan and Dr. A.R. Ray under whose constant encouragement this work has been possible. I thank Prof. S.K. Guha and Prof. S.N.

Tandon for providing me the laboratory and other

facilities at the Centre for Biomedical Engineering, Indian Institute of Technology, Delhi and All India Institute of Medical Sciences (AIIMS), Delhi.

Prof. P.C. Kesvan and Prof. P. Mohanty have helped me by permitting me to avail of the 60Co—y

radiation facilities at Jawaharlal Nehru University, Delhi. Mr. Alexander and Mr. Khan of the School of Life Science4,J.N.U. have taken a great deal of trouble in carrying out the irradiation of the samples. My sincere thanks to them for their constant help.

I sincerely thank Dr. Indra Nath, Assistant Prof., Department of Pathology, AIIMS for helping me in evaluating the biocompatibility of modified and unmodified polyvinyl chloride samples. I also thank Prof. Kusum Verma, Department of Pathology, AIIMS

for her help in vas deferens histopathological studies.

I would like to thank Prof. N. Gopinath, Head, Department of Cardiothoracic Surgery for providing me medical grade polyvinyl chloride (Polystan,Denmark)

ii.

samples. I am indebted to Prof. L.N. Mahapatra, Head, Microbiology, A.I.I.M.S. for providing me the facilities for microbiological work.

My special thanks arc due to Mr. Manjeet Singh Jabbal for his invaluable discussion and help for carrying out biological experiments. It is my pleasure to acknowledge the contribution of Mr. Manmohan Misro in contraceptive studies and of Dr. Kiran Bala in microbiological work. I feel it a pleasure to acknowledge the assistance from

technical staff for their cooperation rendered to carry out this work smoothly.

I am unable to express in words the help

rendered by Mr. S.N. Garg, Mr. Manjit Singh Dhillion and Mr. Sabu Joseph, in the preparation of the

manuscript. It would not have been possible for me to bring this work in the present form without their efforts.

A special word of praise and appreciation is due to members of my family and all friends.

The financial assistance provided for carrying out this work by the Bhabha Atomic Research Centre, Bombay and Council of Scientific and Industrial

Research, New Delhi, is gratefully acknowledged.

( Harp ingh )

ABSTRACT

Various methods of preparation of synthetic polymeric hydrogels and their biomedical applications are discussed. Radiation induced hydrophilic copolymers and graft copolymers were synthesised and evaluated for biomedical applications. Specifically the aspects of biocompatibility and applications of hydrogels in sus-

tained delivery of drugs and male fertility control were examined.

In the first part of the thesis a new method of fertility control in male has been proposed and tested in rat as an experimental model. The technique involves the use of polymer which when injected into the vas

deferens get precipitated there and lowers: the pH to kill the spermatozoa passing through it. Poly (hydroxy- ethylmethacrylate-methacrylic acid) poly(HEMA-MAC), and polystyrene-maleic anhydride) poly(S-MA) were synthe- sised for this purpose. Polymers were characterised using viscosity measurements, pH titration and swelling measurements in saline as well as distilled water. The results indicated that MAC content in the poly (HE MA-MAC) copolymers was roughly proportional to the percentage

of MAC taken in the HEMA : MAC monomer mixture. Viscosity increased with increasing the MAC content in HEMA-MAC

copolymers. In vitro as well as long term in vivo

experiments were carried out to assess the contraceptive

action of the polymers. It was found that this method of male fertility control is non-occlusivel reversible

and has contraceptive effect upto six months in rats.

In the second part of the thesis, radiation grafting with hydrogels using vinyl monomers was envisaged to

increase the biocompatibility as well as heat and ageing resistance of polyvinyl chloride (PVC). Grafting of vinyl monomers onto PVC films and tubes was carried out in different solvents at various dose, dose rate and monomer concentration in nitrogen atmosphere. HEMA,MAC, rIcrylic acid(AC) and N-vinyl-2-pyrrolidone(NVP) were used as monomers in grafting experiments. Effect of Cu ions on the grafting efficiency of HEMA, NVP and ++.

their different mixtureswas also studied in aqueous medium. Graft copolymers were characterized using pH titration, nitrogen estimation, swelling measurements in different media, scanning electron microscopy and thermogravimetric analysis.

It was observed that the grafting percentage was higher at low dose rate and increased with increasing monomer concentration and total dose. With increase in the MAC content in the HEMA-MAC mixture, the percentage grafting also increased. Ce+ionsdid not have a marked effect on grafting when only HEMA or NVP was used but with the mixture of HEMA-NVP, grafting increased signi- ficantly. Thermal stability of PVC increased after grafting with MAC and HEMA.

The tissue and blood compatibility of PVC was found to be increased after grafting with hydrogels.

The feasibility of formulating a drug depot for

sustained delivery using PVC grafted with functional hydrogels was also examined. It was found that

immobilized quaternary ammonium antimicrobial drugs retained their activity against microorganisms and the release was sustained upto 40 days.

CONENTS

CHAPTER PAGE

ABSTRACT

1 POLMERIC HYDROGELS : GENERAL INTRODUCTION

1.1 Review of literature 1 1.1.1 Copolymerization of hydro-

philic monomers with hydro- phobic monomers or with cross—

linking agents 2

1.1.1.1 Copolymerization by Chemical

initiator 2

1.1.1.2 Copolymerization by radiation 20 1.1.2 Grafting of hydrophilic mono-

mers onto stronger polymeric

support 23

1.1.2.1 Grafting by Chemical initiator 23 1.1.2.2 Grafting by radiation 25 1.2 Objective of the present work 33

References 38

2 SYNTHESIS AND CHARACTERIZATION OF HYDROPHILIC POLYMERS

2.1 Introduction 48

2.2 Experimental 49

2.3 Results and discussion 54 2.3.1 Standardization of dose rate

in the cobalt-60 chamber 54 2.3.2 Polymer characterization 54

References 59

3 RADIATION GRAFTED HYDROGELS ON POLYVINYL CHLORIDE : SYNTHESIS AND CHARACTERIZATION

3.1 Introduction 6C

3.2 Experimental 62

3.3 Results ^and discussion 70 3.3.1 Hydroxyethyl methacrylate-

methacrylic acid system 70 3.3.2 Hydroxyethyl methacrylate-

N—viny1-2—pyrrolidone system 75 3.3.3 Nature of the external

polymer 77

3.3.4 Characterization of polymers 80

References 90

4 NOVEL MODE OF MALE CONTRACEPTION USING POLYMERIC HYDROGELS

4.1 Introduction 93

Methods of Male Contraception 4.1.1 Ultra sonic vibration and

ionizing radiation 93 4.1.2 Chemical contraceptives 94 4.1.3 Steroidal contraceptives 94 4.1.4 Sperm enzyme inhibitors 97 4.1.5 Vas deferens contraception 98

4.2 Experimental 101

4.3 Results and discussion 107 4.3.1 In vitro studies 107 4.3.1.1 pH studies ¹⁰⁷ 4.3.1.2 Effect of polymers on rat

spermatozoa 108

4.3.1.3 Effect of polymers on human

spermatoza 109

4.3.1.4 Effect of polymers on the

activity of hyaluronidase 112 4.3.2 In vivo studies 115

References 119

BIOCOMPATIBILITY OF SYNTHESISED POLYMERS

5.1 Introduction 123

5.1.1 Response of the tissue to

implanted materials 123 5.1.2 Effect of materials on blood 125 5.2 Biocompatibility of polyvinyl chloride

(PVC) and modified PVC samples 131 5.2.1 Experimental 131 5.2.2 Results and discussion 135 5.2.2.1 Tissue compatibility of

polyvinyl chloride (PVC) and

hydrogel grafted PVC samples 135 5.2.2.2 Blood compatibility of

polyvinyl chloride(PVC) and

hydrogel grafted PVC samples 142 5.3 Biocompatibility-of _polymers used for

male fertility control 144 5.3.1 Experimental 144 5.3.2 Results and discussion 146 5.3.2.1 Morphological changes in the

rat vas deferens after

injection of the polymer 146

5.3:2.2 Morphological changes in the rat vas deferens after removal

of polymer 148

References 153

RADIATION GRAFTED HYDROGELS ON POLYVINYL CHLORIDE FOR IMMOBILIZATION OF ANTIMICRO- BIAL DRUGS

6.1 Introduction 155

6.2 Experimental 160

6.3 Results Elnd discussion 163 6.3.1

6.3.2

6.3.3

Immobilization of antimicro-

bial drugs on graft copolymers 163 Release of antimicrobial

drugs 164

Assessment of antimicrobial

activity 165

References 169

• SUMMARY AND SCOPE FOR FUTURE WORK

Summary 171

Scope for future work 175