Fabrication of Biosensors - Biosensors and Biosensor Kinetics - page 38

report that proteins were dissolved in de-ionized water. The thiol was dissolved in acetic acid.
A mixture solution was then made by blending them in 19:1 (water:acetic acid) ratio. Thus, a
good solubility was obtained for thiol and there was no precipitation of the proteins and for-
mation of supramolecular structure ( Singh et al., 1999 ). The gold-coated plate was then
immersed in the solution for at least 2 h. The thiol molecules are tightly attached to the elec-
trode surface via the sulfur-metal bond. The proteins are adsorbed on the gold surface
through hydrophilic interactions and electrostatic forces in the absence of strong chemical
bindings ( Kaufmann et al., 2007 ). Cavities that are complementary to the template proteins
were created in the SAM matrix. This was done by repeated rinsing with deionized water
to remove the protein molecules. This unique complementarity on the prepared electrode
facilitated the high affinity for the adsorption of the same kind of template proteins. The
authors then state that their prepared electrode was dried at room temperature overnight
before electrochemical measurements were made.
Wang et al. (2008) report that proteins in aqueous solution act as polyelectrolytes. These have
a net electrical charge. This net electrical charge depends on (a) the isoelectric point of the
protein and (b) the ioinic composition of the solution. Janata (1975) points out that when
charged proteins are trapped in a thin insulating layer deposited on a metallic conductor a
change in surface potential occurs. This change in surface potential may be measured
potentiometrically by using a reference electrode in the same solution.
Finally, Wang et al. (2008) report that their surface molecular imprinted biosensor is capable
of detecting myoglobin and hemoglobin in solution. Their biosensor has the capability to rec-
ognize a specific protein in a solution of multiple proteins. Their results indicate that the size
and shape match is critical for precise recognition.
3.2.3 Fabrication of Molecularly Imprinted Polymer Microarray on a Chip
( Henry et al., 2008 )
Henry et al. (2008) have recently fabricated a molecularly imprinted polymer microarray on a
chip by mid-infrared laser pulse initiated polymerization. These authors indicate that MIPs
have been employed in separation science ( Wei and Mizaikoff, 2007 ) and catalysis ( Tada
and Iwasawa, 2005 ) as well as in chemical and biochemical sensing ( Henry et al., 2005 ).
Lotizero et al. (2004) have indicated that MIPs now compete with natural receptors in terms
of selectivity and sensitivity. Henry et al. (2005) report that MIPs are now an attractive,
cheap, and robust alternative for the detection of small ( Jiang et al., 2007 ), and large
molecules ( Bossi et al., 2007 ).
Henry et al. (2008) point out that the scarcity of publications in the area of multi-MIP platforms
wherein several MIPs prepared against different analytes have been integrated on a single
chip vis-a-vis microarray technology used in genomics, proteomics, and drug screening.