You might have pondered over the materials used in medicines or any other implants. What is the covering of the capsule that you might have seen, quite colourful with smooth texture? Or what the dentist uses when you need tooth replacement and the list goes on. All these materials are known as Biomaterials. Biomaterials are non-viable materials that are used in medical devices, these are intended to interact with biological systems with no side effects.
According to Merriam- Webster, these are materials used for or suitable for use in prostheses that come in direct contact with living tissue. These materials may be natural or synthetic. Biomaterials find use in medical applications to support, enhance or replace damaged tissue. Metals (dental implants, orthopedic screws/ fixations), ceramics (heart valves, bone replacements, dental implants) , composites (biosensors, implantable microelectrodes), polymers (drug delivery systems, ocular implants) and natural biomaterials can be used in creating a biomaterial.
Biomaterials are of three types which can be implanted inside human body as per need, which are mentioned below-
Bio-inert or biologically inert materials are those biomaterials that once placed inside the human body have minimal interaction with the surrounding tissue. These biomaterials do not initiate a response or interact when introduced to biological tissue. The main reason behind choosing this kind of material is that it has no deleterious effects on the host. Bio-inert biomaterials cause fibrous capsule formation upon implantation which favors the appearance of micro-movements in the implant-tissue interface so the prosthesis fails. Examples of bio-inert materials are titanium, stainless steel, alumina, phosphoryl choline, diamond and ultra high molecular weight polyethylene.
Bioactive or biologically active biomaterials are those which form strong bonds when exposed to living tissues. These are non toxic and lead to formation of a direct chemical bond between the implant and host tissue. These can be either natural (collagen, gelatin, fibrin, agarose, chitosan,silk) or synthetic (ceramics, metals, polymers, hydro gels, composites). Bioactive biomaterials elicit a specific biological response. These materials are widely used in medical devices and drug delivery systems. Prime examples are synthetic hydroxyapatite [Ca10(PO4) (OH)2], bioceramic glasses, bioglass, ceravital, etc.
Bio-resorbable or biodegradable materials are those biomaterials which get dissolved or absorbed when placed over a living tissue and are slowly replaced by advancing tissues such as bone. These materials end up being degraded, solubilised or phagocytosed by the body. The major use of these is as stents for blood vessels and other internal ducts. Some common examples are calcium oxide, gypsum, tri calcium phosphate [Ca3(PO4)2], calcium carbonate and polylactic-polyglycolic acid copolymers.
⇒Biomaterials that are implanted need to be biocompatible.
MAIN FEATURES FOR MEDICAL APPLICATIONS-
BIOCOMPATIBILITY is defined as the ability of the material to perform with an appropriate host response in specific applications. Material is biocompatible only if it doesn’t produce any side effects inside the human body and gets easily accepted. It does not produce any toxic effect or immunological response when it comes into contact with the body or its fluids.
BIOFUNCTIONALITY is used to describe a material whose physical and mechanical function is dependent on biological function.
APPLICATIONS OF BIOMATERIALS:
In the cardiovascular system or circulatory system, various problems may arise with heart valves and arteries, both of which can be successfully treated with the help of implants. The valve is coated with pyrolytic carbon and connected to the surrounding tissue with the network of woven fabric known as dacron.
The tissues of eyes are very sensitive and are more prone to suffer from several diseases, which eventually leads to blindness. For example, cataracts cause clouding of the lens. Intraocular lenses are used to replace opaque crystalline lenses (cataract). Inflexible IOL is PMMA (Polymethylmethacrylate) and flexible IOL is silicone acrylate + MMA.
We suffer from various tooth and gum problems now and then. Dental cavities, the dissolution of teeth is associated with the activity of plaque (film of mucus that traps bacteria on the surface of the teeth), can cause extensive loss of tooth. PMMA glass fillers are composites used as dental cements. Alumina and carbons are used as dental implants. Hg – Ag- An amalgam, gold alloys are used in dental restorations and Ni- Ti are used in orthodontics wires.
One of the oldest uses of implantable biomaterials can be traced back to the introduction to sutures for wound closure. Synthetic suture materials included both polymers (the most widely synthetic suture material) and some metals (eg: stainless steel and tantalum).
Both osteoarthritis and rheumatoid arthritis affect the structure of freely movable (synovial) joints, such as hip, knee, shoulder, ankle and elbow. Materials such as chromium, polyethylene, and ceramic (alumina, zirconia) are broadly used biomaterial for orthopedic implants.
BIOMATERIALS- A BOOMING INDUSTRY
Many developments are being processed in this area. It has scope of significant growth now and in the next decade. It is the interface of biotechnology and traditional engineering. Biomaterials have a wide range of use in future. Its uses cover almost all fields of medicine and with more advances many impossible things will be possible soon. Utilization of polymers as biomaterials has greatly impacted the advancement of modern medicine. A wide range of natural and synthetic degradable polymers has been investigated for biomedical applications with novel materials constantly being developed to meet new challenges. As many of you have heard that the future belongs to biomaterials.
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