22. Biological Materials

Biological materials are chemically modified natural materials derived from proteins, carbohydrates, lipids and nucleic acids, whose properties can be tailored to suit the needs of specific applications in mind. There is an urgent need for such bio-derived materials which would demonstrate to have very high value in terms of function, durability, stability and price. One driving factor for our research efforts in this area has been the concern regarding the extensive accumulation of nonbiodegradable materials in our environment at an alarming rate, which is causing extensive damage to life on this planet, directly or indirectly. This problem needs urgent attention from scientists, engineers as well as the general public to find acceptable solutions. One approach is to extensively utilize natural materials such that they are rapidly degraded in a preprogrammed manner into harmless components when released into the environment after their useful lifetime as required for the particular goods. But, naturally occurring materials may not have the necessary characteristics and properties for the intended purpose, and hence chemical modification of the natural materials is required to tailor their properties. In this chapter, an introduction to such materials is provided with one specific example to demonstrate the strategy, scope and versatility of the approach and philosophy of making bio-derived materials for the long term sustainability of our standard of living on this planet. One major advantage of biological materials is that they can be rationally programmed to degrade when exposed to the environmental conditions over predetermined time scales and hence, they would not accumulate in the environment or generate toxic waste. Another advantage of biological materials is that these can be rationally designed based on fundamental principles of chemistry. A clear understanding of the properties of the biological materials with respect to their composition, surface chemistry, morphology, assembly, stability as well as interactions with other kinds of matter is essential to tailor their properties for specific applications. Examples of chemical modification of ordinary proteins to make protein fluorescent nanoparticles of controlled size are described in this chapter. A comparison is made between these bio-derived materials and the current state-of-the-art quantum dot equivalents. The examples illustrated here show the possibility of making biodegradable materials, which are functional, programmable, inexpensive, novel and also generate new and exciting chemistry. Progress in this area is intricately connected with recent advances made in understanding the interactions between the above natural materials and reagents used for the chemical modification of nature’s materials.