Page - (000248) - in Biomedical Chemistry: Current Trends and Developments

and sterilization steps required for biomaterials synthesis, many of which cause protein denaturation. The use of RGD, as compared with native ECM proteins, also minimizes the risk of immune reactivity or pathogen transfer. Another benefit is that the synthesis of RGD peptides is relatively simple and inexpensive, which facilitates translation into the clinic (Bellis, 2011). 3.1.3.3.3 Peptide-based Biomaterials Responsive to Environmental Cues The design and development of materials that react accordingly to the surrounding environment is expected to open up the potential of peptide-based materials (Mart, 2006). Peptides are ideally suited for this purpose because of the range of distinct physical properties available from the naturally occurring amino acids. This diversity allows for rational incorporation of non-covalent interactions including electrostatic (acidic and basic amino acids), hydrophobic, ππ-stacking (aromatic amino acids), hydrogen bonding (polar amino acids) as well as covalent (disulfide) bonds and steric contributions (strand directing amino acids). While individually these interactions are quite weak, collectively they can give rise to very stable structures. These interactions depend significantly in different ways on environmental conditions such as ionic strength, pH and temperature (Mart, 2006). Enzyme responsiveness can be programmed into these materials by incorporation of peptide sequences that are known substrates for proteases, kinases, or phosphatases. The dynamic nature of these interactions allows the protein molecular organization to be altered in response to changes in the direct environment. The degradation rate of the scaffold is another critical factor that can control tissue morphogenesis. In this context, enzyme-sensitive hybrid hydrogels composed of synthetic or natural polymers and peptide/protein domains, which respond to specific cell-secreted proteases (particularly proteases) have been prepared using genetic engineering and/or chemical approaches (Lin & Anseth, 2009). The action of enzymes can be used as stimuli for triggering drug release and also to facilitate scaffold remodelling and replacement by resident and host cells, enabling the infiltration of blood vessels as well as controlling the