Biomaterials Topics at Texas Materials Institute
A biomaterial is any material, natural or man-made, that comprises whole or part of a living structure or biomedical device which performs, augments, or replaces a natural function. Biomaterials can be metals and alloys, polymers (synthetic or natural), ceramics and composites. Often single materials cannot fulfill all the requirements imposed by a specific application. A total hip prosthesis, for example, needs more than one material: a titanium alloy (mechanical strength) coated with hydroxyapatite (bone-integration) for the bulk of the stem, a ball head in alumina (wear resistance), and a polythene cup.
Materials are critical for many biomedical and biotechnology applications, including biosensors, medical implants, controlled drug delivery, and device coatings. Furthermore, the study of natural biopolymers, such as DNA and cytoskeletal proteins, is essential to understand the function of biological systems and how to mimic, augment, or detect such systems.
(Faculty: Heller, Shear, Korgel, Shih, Ellington, Käs)
Biosensors can be classified as structures or devices that specifically monitor the presence or concentration of a desired biological component. Examples of such biosensors include devices that detect the concentration of glucose in the blood and microfabricated arrays of nano-detectors capable of rapidly analyzing complex solutions for the presence of many analytes such as toxins and drug metabolites. An essential component of a molecular sensor is the reagent layer(s). Creation of these layers requires the immobilization of recognition elements for the detection method. In the case of biosensors, these recognition elements are typically biomolecules such as enzymes, antibodies, and whole cells. These reagent layers are usually constructed from various polymers which can be easily deposited, and whose properties can be tailored according to hydrophilicity, hydrophobicity and mechanical requirements, while still allowing the covalent attachment of biorecognition ligands or the incorporation of whole cells.
(Faculty: Schmidt, Barlow)
As advances have been made in the medical sciences, the average life expectancy has increased. More organs, joints, and other critical body parts will wear out and must be replaced if people are to maintain a good quality of life. Biomaterials now play a major role in replacing or improving the function of every major body system. Some common implants include orthopedic devices such as total knee and hip joint replacements, spinal implants, and bone fixators; cardiac implants such as artificial heart valves and pacemakers; soft tissue implants such as breast implants and injectable collagen for soft tissue augmentation; and dental implants to replace teeth/root systems and bony tissue in the oral cavity. The number of implants in use in this country (e.g., 811,000 artificial hips in 1988 and 170,000 artificial heart valves in 1994) indicates their importance to health care and the economic impact of the biomaterials industry. Design, material selection, and biocompatibility remain the three critical issues for today’s biomedical implants and devices. Furthermore, new research into the synthesis and modification of degradable polymers has been crucial for the area of “tissue engineering”, in which tissue cells and biodegradable materials can be combined to create natural, living tissue replacements.
Controlled Drug Delivery
(Faculty: Johnston, Lloyd, Paul)
Controlled drug delivery occurs when a polymer, whether natural or synthetic, is judiciously combined with a drug or other active agent in such a way that the active agent is released from the material in a predesigned manner. The release of the active agent may be constant over a long period, it may be cyclic over a long period, or it may be triggered by the environment or other external events. In any case, the purpose behind controlling the drug delivery is to achieve more effective therapies while eliminating the potential for both under- and overdosing. Other advantages of using controlled-delivery systems can include the maintenance of drug levels within a desired range, the need for fewer administrations, optimal use of the drug in question, and increased patient compliance. While these advantages can be significant, the potential disadvantages cannot be ignored: the possible toxicity or nonbiocompatibility of the materials used, undesirable by-products of degradation, any surgery required to implant or remove the system, the chance of patient discomfort from the delivery device, and the higher cost of controlled-release systems compared with traditional pharmaceutical formulations.
(Faculty: Heller, Lloyd)
A natural exploitation of biomaterials is also found in other applications requiring a ‘bioactive’ interface. For example, the problem of biofouling and biocorrosion, may be overcome with bacteriacidal or inhibitory surfaces. The modification of materials such as polymers to produce an activated or conversely deactivated surface, for packaging and encapsulation, is important to establish the critical parameters in enhancing or inhibiting a surface or solution reaction.
(Faculty: Käs, Brown, Schmidt)
The study of natural biopolymers is fundamental for understanding how animal and plant cells and animal tissues function and respond under certain conditions. Such an understanding is crucial if these cells and tissues are to be augmented, modified, detected, or used to produce important therapeutic agents. For example, knowledge of the three-dimensional structure of proteins is necessary for understanding and consequently controlling the modification of their biological activity, as might be required for the proper design of a biosensor.