Smart polymeric carriers for drug delivery enzyme-responsive nanocarriers

3 Smart polymeric carriers for drug delivery enzyme-responsive nanocarriers 

An emerging area of research in stimuli-responsive polymeric nanocarriers is related to nanomaterials that experience macroscopic property changes mediated by the catalytic activity of enzymes. The importance of this field is evident by the large number of recent publications related to it (de la Rica et al., 2012 Fleige et al., 2012 Hu et al., 2012). 

These systems have a distinctive specificity, as enzymes are highly selective biomolecules. Moreover, enzymes are functional under mild conditions (which is a crucial feature in vivo), and are critical components in many biological pathways. For instance, enzymes are key targets for drug development, since they play a key role in cell regulation. Enzymatically sensitive nanomaterials can be designed to deliver and release their cargos specifically at 

To date, two main approaches have been adopted for developing enzyme-responsive materials. In the first and most common approach, the nanocarrier itself is sensitive to enzymatic transformation. This is achieved by the use of either an enzymatically degradable polymer or enzymatically sensitive linkers between the drug and the polymer. 

The second approach is based on the surface modification of the nanocarriers with molecules that confer enzymatically triggered changes of the physical properties of the carrier solution. This approach is extremely versatile and has been mainly used in developing inorganic enzyme-responsive nanoparticles (Medintz et al, 2005 Stevens et al, 2004 Zelzer and Ulijn, 2010) for which use as DDS has not been so fully developed because of toxicological concerns. It will not therefore be discussed in this chapter. For further information the reader is referred to some excellent recent literature (de la Rica et al, 2012 Ghadiali and Stevens, 2008 Hu et al, 2012 Nie era/., 2009). 

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