Biomolecule-responsive surfaces

In other biomolecule-responsive surfaces, the incorporation of molecules with various functional groups in responsive polymers has been investigated, for example, benzo-18-crown-6 residue for ion selectivity [72], affinity binding between biotin and streptavidin [73], and oligopeptides for chiral recognition [74]. 

There are numerous examples of polymer surfaces that react with a change of their properties when brought into contact with certain species. These trigger species can be low molar mass molecules (chemoresponsive) or complex biomolecules like DNA or proteins (bioresponsive). Both types of responsive surfaces exist in several varieties depending on their mode of action and the parameter that they affect. 

The ability to control the interaction between a wide diversity of biomolecules with surfaces can be also exploited as an effective way to develop reagentless, sensitive, reusable, and real-time biosensors [51-56]. Such sophisticated biosensors are expected to impact a wide range of applications, from clinical diagnosis[57] and environmental monitoring [58] to forensic analysis [59]. Another significant potential application of dynamic surfaces is in bioseparation of proteins and other biomolecules for basic life science research, as well as industrial applications [60-63]. With the rapid development of recombinant proteins in the treatment of various human diseases, the dynamic surface-based bioseparation systems could meet the demand for more reliable and efficient protein purification methods [64]. Stimuli-responsive surfaces are also expected to play a crucial role in the search for more controllable and precise drug delivery systems [65]. 

By their nature, peptide-based responsive surfaces have been predominantly considered for biological applications. Three applications areas have been explored thus far (1) biosensors (2) control of the adhesion of proteins, cells, and other biomolecules and (3) bioseparation. The current state of the art for these three application areas will be outlined below. 

The book provides an overview of recent advances in responsive surfaces and materials designed for biomedical applications. Both bulk responsive materials and surface modification techniques are included. The interactions of biomolecules and cells with responsive interfaces are specifically reviewed, with discussion of emerging applications that could change our lives. The book is divided into two parts with four interdisciplinary topics. The first part reviews switchable and responsive material technologies for biomedical applications (Chapters 1-6). The two topics of Part One are responsive materials and responsive surface modification respectively. Part Two (Chapters 7-11) explores two topics include the interaction of switchable surfaces with proteins and cells, as well as multidispUnary research toward different biomedical applications. 

Experimental techniques based on the application of mechanical forces to single molecules in small assemblies have been applied to study the binding properties of biomolecules and their response to external mechanical manipulations. Among such techniques are atomic force microscopy (AFM), optical tweezers, biomembrane force probe, and surface force apparatus experiments (Binning et al., 1986 Block and Svoboda, 1994 Evans et ah, 1995 Israelachvili, 1992). These techniques have inspired us and others (see also the chapters by Eichinger et al. and by Hermans et al. in this volume) to adopt a similar approach for the study of biomolecules by means of computer simulations. 

Mainly, three approaches have been used to immobilize the enzyme on transducer or electrode surface, single layer, bilayer, and sandwich configurations [69, 98], In some studies enzymes are covalently linked with sol-gel thin films [99], Sol-gel thin films are highly convenient for fast, large, and homogeneous electron transfer [17]. With an increase in gel thickness the signal decays and diffusion of analytes to biomolecule active site becomes difficult eventually these factors lead to poor response. By employing thin films various biosensors such as optical and electrochemical biosensors have been reported. 

Regarding the mechanism of biomolecules functionalized CNTs entering into cells, endocytosis mechanism may be responsible for the phenomena, a theory model is also suggested (Gao et al., 2005) the optimal size of particles entering into cells is between 20 nm and 700 nm or so, too small nanopaiticles are very difficult to enter into cells because of cellular surface tension force and adhesion. The further mechanism of effects of CNTs on human healthcare and environment is being investigated from the following four scales such as molecular, cellular, animals, and environment levels. 

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