Disposable Insulin Delivery System Mid-semester report BME 200/300 Team Members Cullen Rotroff (Leader) Tyler Allee (BSAC) Kailey Feyereisen (Communicator) Malini Soundarrajan (BWIG) Client Michael J. MacDonald, M.D. Head, Pediatrics Diabetes and Endocrinology Division Director, Children’s Diabetes Center UW Hospital and Clinics Advisor Professor William L. Murphy, PhD Department of Biomedical EngineeringAbstract Doctor Michael J. MacDonald specializes in type I, juvenile onset diabetes. A great deal of time, money, and research is invested into insulin delivery for insulin dependant diabetics. While extremely intricate systems like Medtronic’s MiniMed can effectively interact with a patient’s daily routine to provide a complex daily insulin diet, these systems are extremely expensive. Our goal is to develop a cheap, disposable drug pump that will deliver the basal rate of insulin for at least eight hours. We developed three designs that could solve the problem and chose one design to pursue for prototyping and further research. Our design will use hydrogels as an actuator and a valve to deliver constant increments of insulin. If prototyping is feasible, we believe we can develop this product for well under $100.00, a dramatic step down from the $6,195 MiniMed Paradigm. Problem Statement Our objective is to design a novel method of drug delivery that is disposable, small, light, and inexpensive. The system must be comfortable and discrete while in use. The product should utilize micro-fluidics to deliver a constant flow rate between ten and fifty micro liters per hour with minimal error or fluctuation for no less than eight consecutive hours. Introduction The human body uses a complex metabolic system to sustain life and power its everyday actions. It converts complex forms of food into glucose, a type of sugar. Insulin, a hormone secreted from beta cells of the pancreas, convert glucose into more useable forms of energy. Ifthe body is in need of energy, it aides the movement of glucose into cells for break down into useable energy forms. Surplus glucose is then converted by insulin into glycogen for storage in liver, muscle, or fat cells. Meanwhile, glucagon released from alpha cells of the pancreas break glycogen down from the liver and release it into the blood stream between meals each day. This homeostasis system can be seen in figure 1. Figure 1. Flow chart of insulin, glucagon, and glucose in the body. http://nema.cap.ed.ac.uk/teaching/odl/odl5/insulin.jpg Diabetes is a disease that disturbs the body’s the body’s use or production of insulin in the body. This disease has three main forms: Type I, Type II, and gestational diabetes. Diabetes II is the most prominent form in the United States. The problem occurs when muscle, liver, and fat cells develop an insulin resistance condition that inhibits glucose uptake into cells. The pancreas responds by creating more insulin to compensate. Over time, the pancreas will become fatigued and will eventually lose the battle with insulin inefficiency; Though it is possible todelay the development of diabetes II with a good diet and frequent exercise, the pancreas will eventually fail to secrete enough insulin to adequately respond to glucose intake during meals. A second, less serious form of diabetes is gestational diabetes, which develops temporarily in women in their late stages of pregnancy. Though little is known about the causes of this diabetes type, it is believed that developmental hormones from the mother’s placenta also cause insulin resistance (American Diabetes Association). Our client Michael J MacDonald, M.D., specializes in Type I diabetes. Type I develops from an autoimmune response in which the body’s white blood cells attack the insulin-producing beta cells of the pancreas. More than 700,000 children and young adults are affected each year. Type I is most commonly developed in children, which is why it is sometimes referred to as Juvenile onset Diabetes. Type I is also called insulin dependant diabetes; because the insulin producing beta cells are destroyed, this type of diabetes necessitates treatment with insulin supplements. Without the constant treatment of insulin, blood glucose levels will become far too high, which can have fatal repercussions for the diabetic. Desirable glucose levels in a non diabetic human are between 70 and 120 milligrams per deciliter (WebMD, Inc.). These levels normally rise after meals, but should return to normal a few hours after. If insulin levels are too low, glucose levels will remain over 180 mg/dL. Immediate responses include blurry vision, frequent urination, and nausea; however, there are many dangerous long term results of having consistently high levels of glucose. High blood glucose levels cause blood vessels in the eyes to bleed, which can result in blindness. High glucose levels are hard on the kidneys and can eventually lead to kidney failure, a loss that would require a transplant or use of a dialysis machine for survival. High glucose levels can also result in nerve damage, which would most notably be detected by pain or complete loss of feeling inthe legs, feet, arms, or hands. Hyperglycemia can also lead to gum infections, as well as infections of bones that hold the teeth in place. Finally, long term high glucose rates increase the risk of heart disease. A type one diabetic must supplement the lacking insulin production of their destroyed beta cells with insulin injections. Because insulin is a large protein it cannot be administered transdermally (through the skin), without the aid of ultrasonic frequency vibrations to further open the pores of the skin. It can also not be administered via pills, because the protein would be broken down by the acids and enzymes of the stomach. Although, a great deal of research is committed to discovering alternative methods of insulin delivery, subcutaneous injection is the major method at this time. Insulin is ideally injected subcutaneously into adipose tissue of the abdomen, which requires 9.1 mmHg of pressure. Injection location must be rotated to avoid hypertrophy, a build up of scar tissue at the injection site. A picture of where subcutaneous tissue is located is shown in figure 2. Figure 2. Picture of skin anatomy, shows where the subcutaneous layer is http://www.engr.utexas.edu/bme/faculty/schmidt/Research/TissEng/img_skindiagram.jpg Insulin regulation can be broken down into two main
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