Protein immobilization smart polymers

A novel approach to immobilization of enzymes via covalent attachment is the use of stimulus-responsive smart polymers, which undergo dramatic conformational changes in response to small alterations in the environment, such as temperature, pH, and ionic strength [401 03], The most prominent example is a thermo-responsive and biocompatible polymer (poly-iV-isopropyl-acrylamide), which exhibits a critical solution temperature around 32°C, below which it readily dissolves in water, while it precipitates at elevated temperatures due to the expulsion of water molecules from its polymeric matrix. Hence, the biolransformation is performed under conditions, where the enzyme is soluble. Raising the temperature leads to precipitation of the immobilized protein, which allows its recovery and reuse. In addition, runaway reactions are avoided because in case the reaction temperature exceeds the critical solution temperature, the catalyst precipitates and the reaction shuts down. 

Protein immobilization is an important issue for biomedical and biotechnological applications, including controlled drug delivery, protein separation, and biosensors. Smart polymers can manage protein immobilization by the manipulation of environmental parameters (temperature, pH, ionic strength, electric field, and light) (Mendes, 2008). SPB are an attractive option for protein or enzyme immobilization (Jain et al., 2009). 

Fig. 15 Specific protein separation by a smart thermoresponsive polymer coating. Left PNIPAM with immobilized lactose and RCA 120 is below the LCST. The moieties are separated and, therefore, proteins from the mobile phase can bind to RCA120. Right PNIPAM below LCST. Polymer-bound lactose and RCA120 come into close contact and lactose displaces the protein. Reprinted, with permission, from [194]. Copyright (2003) American Chemical Society...

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