9/19/2018 Biomaterials Lec # 1-2

What is a Biomaterial? A biomaterial is a nonviable material used in a medical device, intended to interact with biological systems (Williams, 1987) [OR] Any material of natural or of synthetic origin that comes in contact with tissue, blood or biological fluids, and intended for use in prosthetic, diagnostic, therapeutic or storage application without adversely affecting the living organism and its components. 9/19/2018

Term Definitions Biomaterial: A synthetic material used to make devices to replace part of a living system or to function in intimate contact with living tissue. Biological Material: A material that is produced by a biological system. Bio-compatibility: Acceptance of an artificial implant by the surrounding tissues and by the body as a whole. 9/19/2018

Fields of Knowledge to Develop Biomaterials 1- Science and engineering: (Materials Science) structure-property relationships of synthetic and biological materials including metals, ceramics, polymers, composites, tissues (blood and connective tissues), etc. 2- Biology and Physiology: Cell and molecular biology, anatomy, animal and human physiology, histopathology, experimental surgery, immunology, etc. 3- Clinical Sciences: (All the clinical Specialties) density, maxillofacial, neurosurgery, obstetrics and gynecology, ophthalmology, orthopedics, plastic and reconstructive surgery, thoracic and cardiovascular surgery, veterinary medicine and surgery, etc. 9/19/2018

Uses of Biomaterials Uses of Biomaterials Example Replacement of diseased and   damaged part Artificial hip joint, kidney dialysis machine Assist in healing Sutures, bone plates and screws Improve function Cardiac pacemaker, intra-ocular lens Correct functional abnormalities Cardiac pacemaker Correct cosmetic problem Mastectomy augmentation, chin augmentation Aid to diagnosis Probes and catheters Aid to treatment Catheters, drains 9/19/2018

Biomaterials in Organs Example Heart Cardiac pacemaker, artificial heart valve, Totally artificial heart Lung Oxy-generator machine Eye Contact lens, intraocular lens Ear Artificial stapes, cochlea implant Bone Bone plate, intra-medullary rod Kidney Kidney dialysis machine Bladder Catheter and stent 9/19/2018

Need for Biomaterials Millions of patients suffer end stage organ and tissue failure annually. 8 million surgical procedures. Treatment options include transplantation, reconstruction, mechanical devices. 9/19/2018

The options and Limitations Transplantation Critical donor shortage 3000 livers annually for 30000 people in need Disease Transmission HIV Hepatitis Other transmittable diseases. Surgical Reconstruction Not always possible Complications 9/19/2018

Continues… Mechanical Devices Engineering approach – engineer new tissues, systems Limited by Complexity of the human body Multiple functions Living components versus non living components Materials? Tissue based Polymers Metals Ceramics 9/19/2018

Commonly Used Biomaterials Material Applications Silicone rubber Catheters, tubing Dacron Vascular grafts Cellulose Dialysis membranes Polyurethanes Catheters, pacemaker leads Hydrogels Ophthalmological devices, Drug Delivery Stainless steel Orthopedic devices, stents Titanium Orthopedic and dental devices Alumina Orthopedic and dental devices Hydroxyapatite Orthopedic and dental devices Collagen (reprocessed) Ophthalmologic applications, wound dressings 9/19/2018

Significance of Biomaterials Replace diseased part – Dialysis Assist in Healing – Sutures Improves Function – Contacts Correct Function – Spinal rods Correct Cosmetic – Nose, Ear Aids – Probes / Catheters Replace dead - Skin 9/19/2018

Characteristics of Biomaterials Physical Requirements Hard Materials. Flexible Material. Chemical Requirements Must not react with any tissue in the body. Must be non-toxic to the body. Long-term replacement must not be biodegradable. Biocompatibility is defined as the property of being biologically compatible by not producing a toxic, injurious, or immunological response in living tissue. The human body has an extraordinary ability to be able to tell whether an object is foreign or not. This is part of the bodies protection against invasion from an outside organism. If a substance is placed in the body and the body can tell it is foreign, then an immune system response will be generated. When an object is incorporated into the body without any immune responses it is said to be BIOCOMPATIBLE. In order for a device to be biocompatible, it must follow a very stringent set of demands from the body.  The device must be very strong so it does not break inside the body. Depending on the circumstances, it may need to be either very hard or very flexible. Anything placed into the body must be able to take a constant physical beating from one's body. For instance, the valves in a heart open and close about 70 - 80 times a minute. Over the course of years and years this adds up to millions of pumps. If the artificial valve cannot meet these standards and fails, the person will die.  9/19/2018

History More than 2000 years ago, Romans, Chinese, and Aztec’s used gold in dentistry. Turn of century, synthetic implants become available. 1937 Poly(methyl methacrylate) (PMMA) introduced in dentistry. 1958, Rob suggests Dacron Fabrics can be used to fabricate an arterial prosthetic. 9/19/2018

Synthetic BIOMATERIALS Polymers Skin/cartilage Drug Delivery Devices Ocular implants Bone replacements Orthopedic screws/fixation Ceramics Metals Heart valves Synthetic BIOMATERIALS Semiconductor Materials Dental Implants Dental Implants Biosensors Implantable Microelectrodes 9/19/2018

First Generation Biomaterials Specified by physicians using common and borrowed materials. Most successes were accidental rather than by design. 9/19/2018

Second Generation of Biomaterials Developed through collaborations of physicians and engineers. Engineered implants using common and borrowed materials. Built on first generation experiences. Used advances in materials science (from other fields). 9/19/2018

Third generation implants Bioengineered implants using bioengineered materials. Few examples on the market. Some modified and new polymeric devices. Many under development. 9/19/2018

Examples of Biomaterial Applications Heart Valve Artificial Tissue Dental Implants Intraocular Lenses Vascular Grafts Hip Replacements 9/19/2018

Heart Valve Fabricated from carbons, metals, fabrics, and natural valves. Must NOT React With Chemicals in Body. Attached By Polyester Mesh. Tissue Growth Facilitated By Polar Oxygen- Containing Groups. 9/19/2018

Heart Valve Almost as soon as valve implanted cardiac function is restored to near normal. Bileaflet tilting disk heart valve used most widely. More than 45,000 replacement valves implanted every year in the United States. 9/19/2018

Bileaflet Heart Valves 9/19/2018

Problems with Heart Valve’s Degeneration of Tissue. Mechanical Failure. Postoperative infection. Induction of blood clots. 9/19/2018

Dental Implants Small titanium fixture that serves as the replacement for the root portion of a missing natural tooth. Implant is placed in the bone of the upper or lower jaw and allowed to bond with the bone. Most dental implants are: pure titanium screw-shaped cylinders that act as roots for crowns and bridges, or as supports for dentures. 9/19/2018

Capable of bonding to bone, a phenomenon known as "osseointegration”. Dental Implants Capable of bonding to bone, a phenomenon known as "osseointegration”. Bio-inert, there is no reaction in tissue and no rejection or allergic reactions. 9/19/2018

Dental Implants 9/19/2018

Intraocular Lenses Made of PMM, silicone, and other materials. By age 75 more than 50% of population suffers from cataracts. 1.4 million implantations in the United States yearly. Good vision is generally restored almost immediately after lens is inserted. 9/19/2018

Intraocular Lenses 9/19/2018

Hip-Replacements Most Common Medical Practice Using Biomaterials. Corrosion Resistant high-strength Metal Alloys. Very High Molecular Weight Polymers. Thermoset Plastics. 9/19/2018

Hip-Replacements Some hip replacements ambulatory function restored within days after surgery. Others require an extensive healing period for attachment between bone and the implant. Most cases good function restored. After 10-15 years, implant loosens requiring another operation. 9/19/2018

Hip-Replacements 9/19/2018

Biomaterials - An Emerging Industry Next generation of medical implants and therapeutic modalities. Interface of biotechnology and traditional engineering. Significant industrial growth in the next 15 years -- potential of a multi-billion dollar industry. 9/19/2018

Biomaterials Companies Baxter International develops technologies related to the blood and circulatory system. Biocompatibles Ltd. develops commercial applications for technology in the field of biocompatibility. Carmeda makes a biologically active surface that interacts with and supports the bodys own control mechanisms Collagen Aesthetics Inc. bovine and human placental sourced collagens, recombinant collagens, and PEG-polymers Endura-Tec Systems Corp. bio-mechanical endurance testing ofstents, grafts, and cardiovascular materials Howmedica develops and manufactures products in orthopaedics. MATECH Biomedical Technologies, development of biomaterials by chemical polymerization methods. Medtronic, Inc. is a medical technology company specializing in implantable and invasive therapies. Molecular Geodesics Inc., biomimetic materials for biomedical, industrial, and military applications Polymer Technology Group is involved in the synthesis, characterization, and manufacture of new polymer products. SurModics, offers PhotoLink(R) surface modification technology that can be used to immobilize biomolecules W.L. Gore Medical Products Division, PTFE microstructures configured to exclude or accept tissue ingrowth. Zimmer, design, manufacture and distribution of orthopaedic implants and related equipment and supplies 9/19/2018

Development of biomaterials devices: Fig 6. It provides a perspective on how different disciplines work together, starting from the identification of a need for a biomaterial through development, manufacture, implantation, and removal from the patient. 9/19/2018

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Success and Failure Most biomaterials and medical devices perform satisfactorily, improving the quality of life for the recipient or saving lives. However, no manmade construct is perfect. All manufactured devices have a failure rate. Also, all humans are different with differing genetics, gender, body chemistries, living environment, and degrees of physical activity. Furthermore, physicians implant or use these devices with varying degrees of skill. 9/19/2018

Success and Failure The other side to the medical device success story is that there are problems, compromises, and complications that occur with medical devices. Central issues for the biomaterials scientist, manufacturer, patient, physician, and attorney are, (1) what represents good design, (2) who should be responsible when devices perform " with an inappropriate host response," and (3) what are the cost/risk or cost/benefit ratios for the implant or therapy? 9/19/2018

THANKS 9/19/2018