Migration Resistant, Blood-Compatible Plasticized Polyvinyl Chloride for Medical and Related Applications S. Lakshmi and A. Jayakrishnan Polymer Chemistry Division, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India Abstract: Plasticized polyvinyl chloride (PVC), although not a blood-compatible polymer, is the material of choice for the manufacture of blood bags and hemodialysis tubing throughout the world. PVC is usually plasticized with di- (2-ethylhexyl phthalate) (DEHP) to impart flexibility and low temperature properties to the final product. DEHP belongs to a class of agents called hypolipidemic hepato- carcinogens, and it migrates in small quantities into the storage medium such as blood, plasma, or serum, resulting in a number of toxic effects. It has been shown that the migration resistance and blood compatibility of flexible PVC could be significantly improved by grafting polyeth- ylene glycol (PEG), the most blood-compatible polymer known today, onto the surface of flexible PVC by the clas- sical Williamson ether synthesis reaction. The technique is simple and versatile enough to produce blood-compatible, migration resistant PVC surfaces for many medical appli- cations. The method may also find use for preventing plas- ticizer migration from PVC cling films and polyvinylidene chloride films used extensively in food packaging. Key Words: Polyvinyl chloride—Polyethylene glycol— Grafting—Surface modification—Blood compatibility— Plasticizer migration—Di-(2-ethylhexyl phthalate). Plasticized polyvinyl chloride (PVC) is one of the most widely used polymeric materials in medical and related fields. In the medical field, flexible PVC is used for the manufacture of blood and blood com- ponent storage bags, heart lung bypass sets, endotra- cheal tubes, intravenous solution dispensing sets, blood tubings, urine bags, etc. The estimated market share of PVC is around 25% of all the polymeric materials used in medical devices (1). PVC as such is a rigid polymer, and additives known as plasticizers are incorporated into PVC to increase its flexibility and low temperature properties. The esters of phthalic acid, particularly di-(2-ethylhexyl phthalate) (DEHP), are the most preferred plasticizers for medical grade PVC. Because these additives are not held onto the base polymer by covalent linkages, the permanence of these chemicals is low. The migration of DEHP from flexible PVC based medical devices and storage bags into physiological fluids has been a subject of major concern for many years (2,3). Plas- ticized PVC used for the manufacture of blood bags and transfusion tubings contains up to 40 wt% DEHP (4). The toxicity of phthalate esters has raised serious questions about their use as plasticizers for polymers used in medical, pharmaceutical, and food packaging applications (5–8). DEHP belongs to a class of agents called hypolipidemic hepatocarcino- gens and is reported to be capable of producing ad- verse effects on pituitary gland tissues and causing liver abnormalities and testicular atrophy (9–12). Phthalate, adipate, and citrate plasticizers are also widely employed in the manufacture of PVC cling films and films of polyvinylidene chloride, cellulose acetate, and regenerated cellulose used for the pack- aging of foodstuffs such as cheese, meat, chocolate, and confectionary products (6). Concern over the high migration of such plasticizers into foodstuffs, especially fatty foods such as cheese and meat, has led some governments to impose restrictions on the use of PVC films for food packaging (13). Various attempts have been made to reduce plas- ticizer migration from flexible PVC. Methods em- ployed include the use of polymeric plasticizers, Received November 1997. Presented in part at the XI World Congress of the International Society for Artificial Organs, held June 29–July 1, 1997, in Provi- dence, Rhode Island, U.S.A. Address correspondence and reprint requests to Dr. A. Jayakrishnan, Polymer Chemistry Division, Biomedical Technol- ogy Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Satelmond Palace Campus, Trivandrum 695 012, In- dia. Artificial Organs 22(3):222–229, Blackwell Science, Inc. © 1998 International Society for Artificial Organs 222