LECTURE 6BIOMATERIALS1 BIOSENSORS A biosensor is an analytical device which converts a biological response into an electrical signal. The term 'biosensor' is often used to cover sensor devices used in order to determine the concentration of substances and other parameters of biological interest even where they do not utilise a biological system directly. Research and development in this field is wide and multidisciplinary, spanning biochemistry, bioreactor science, physical chemistry, electrochemistry, electronics and software engineering.

LECTURE 6BIOMATERIALS2 BIOSENSORS A successful biosensor must possess at least some of the following beneficial features: The biocatalyst must be highly specific for the purpose of the analyses,be stable under normal storage conditions. The reaction should be as independent of such physical parameters as stirring, pH and temperature as is manageable. If the reaction involves cofactors or coenzymes these should, preferably, also be co-immobilised with the enzyme.

LECTURE 6BIOMATERIALS3 BIOSENSORS Schematic diagram showing the main components of a biosensor. The biocatalyst (a) converts the substrate to product. This reaction is determined by the transducer (b) which converts it to an electrical signal. The output from the transducer is amplified (c), processed (d) and displayed (e).

LECTURE 6BIOMATERIALS4 BIOSENSORS The key part of a biosensor is the transducer which makes use of a physical change accompanying the reaction. This may be the heat output by the reaction,changes in the distribution of charges causing an electrical potential to be produced,movement of electrons produced in a redox reaction,light output during the reaction or a light absorbance difference between the reactants and products,or effects due to the mass of the reactants or products.

LECTURE 6BIOMATERIALS5 BIOSENSORS There are three so-called 'generations' of biosensors; First generation biosensors where the normal product of the reaction diffuses to the transducer and causes the electrical response. Second generation biosensors which involve specific 'mediators' between the reaction and the transducer in order to generate improved response. Third generation biosensors where the reaction itself causes the response and no product or mediator diffusion is directly involved.

LECTURE 6BIOMATERIALS6 BIOSENSORS The electrical signal from the transducer is often low and superimposed upon a relatively high and noisy baseline. The signal processing normally involves subtracting a 'reference' baseline signal, derived from a similar transducer without any biocatalytic membrane, from the sample signal, amplifying the resultant signal difference and electronically filtering (smoothing) out the unwanted signal noise.

LECTURE 6BIOMATERIALS7 BIOSENSORS The relatively slow nature of the biosensor response considerably eases the problem of electrical noise filtration. The analogue signal produced at this stage may be output directly but is usually converted to a digital signal and passed to a microprocessor stage where the data is processed, converted to concentration units and output to a display device or data store.

LECTURE 6BIOMATERIALS8 TISSUE ENGINEERING Tissue engineering / regenerative medicine is an emerging multidisciplinary field involving biology, medicine, and engineering that is likely to revolutionize the ways we improve the health and quality of life for millions of people worldwide by restoring, maintaining, or enhancing tissue and organ function. In addition to having a therapeutic application, where the tissue is either grown in a patient or outside the patient and transplanted, tissue engineering can have diagnostic applications where the tissue is made in vitro and used for testing drug metabolism and uptake, toxicity, and pathogenicity.

LECTURE 6BIOMATERIALS9 TISSUE ENGINEERING Tissue engineering has been defined as "the use of living cells together with extracellular components, either natural or synthetic, in the development of implantable parts or devices for the restoration or replacement of biological function". In other words, tissue engineering includes isolated cells,tissue-inducing substances, and cells placed within matrices.

LECTURE 6BIOMATERIALS10 TISSUE ENGINEERING  Organs contains one or more tissues and tissues are made up of specific cells.  The three parts of tissue that regulate the performance of a cell are (i)The cells themselves (ii)Non-soluble factors within the extracellular matrix (ECM) such as laminins,collagens,and other molecules (iii)Soluble factors such as cytokines, hormones, nutrients, vitamins, and minerals.

LECTURE 6BIOMATERIALS11 TISSUE ENGINEERING In tissue engineering, there are several steps, which need be considered to accomplish a specific goal.These steps include: cell isolation cell culture scaffold material choice cell scaffold co-culture studies implantation in animals human trials

LECTURE 6BIOMATERIALS12 TISSUE ENGINEERING Thus, tissue-engineering procedure can be divided into two broad categories in vitro construction of tissue containing devices, in vivo alteration of cell growth and function.

LECTURE 6BIOMATERIALS13 TISSUE ENGINEERING Tissue engineering has many applications like, it is used as Implantable Devices - vascular grafts, bone and cartilage grafts Extracorporeal devices - artificial liver and artificial pancreas Cell production and Cell growth - skin cells, nerve regeneration

LECTURE 6BIOMATERIALS14 TISSUE ENGINEERING Now a days absorbable materials like synthetic polysters,polyvinyl alcohol etc are used in tissue engineering to support tissue growth. The tissues are grown on absorbable support. As new tissues forms the absorbable material disappears.

LECTURE 6BIOMATERIALS15 TISSUE ENGINEERING Tissue engineering finds wide applications in the field of medicine. The method of transplantation and reconstruction are of huge costs. Tissue engineering provides substitutes that are less expensive than the donor organs and leads to less complications.