Biomedical Engineering Reference
In-Depth Information
target ligand, the δ -opioid G-protein coupled receptor agonist DPDPE, which reproducibly
exhibits subpicomolar binding affinity in an aqueous environment. This imprinted polymer
showed a broad structure-activity relationship profile, not unlike that found for protein
receptors. Such sensitivity and robustness of molecular imprinted polymers suggest potential
applications ranging from biowarfare agent detection to pharmaceutical screening.
Recently, considering the importance of the template shape and conformation in a pre-
polymerization mixture for protein imprinting, possible sources causing protein template
denaturation in the application of miniemulsion polymerization for molecular imprinting was
studied [53, 54]. It was suggested that to avoid high temperature or high-energy irradiation,
redox initiation would be a suitable alternative for protein imprinting. In addition, it was
found that a certain degree of interaction between the template protein and the micelles was
required to maintain the proteins at the particle surface. However, such an interaction should
not be too extensive to cause a significant conformational change to ensure the recognition of
proteins in their native states. Using poly(vinyl alcohol) as a co-surfactant had proved to be
effective in preserving the template protein structural integrity. On top of that, the high-shear
homogenization had been shown to cause negligible disruption to the template protein
conformation. Employed fluorescein isothiocyanate derivative-albumin as the protein
template molecule in an aqueous phase molecular imprinted polymer, for the first time,
Hawkins et al. [55] reported the use of a fluorescently labeled template. The selective
recognition material had been imaged using confocal microscopy. The resulting imformation
would contribute to the understanding of aqueous phase molecular imprinting protocols, with
the successful in situ imaging of real-time protein denaturation events being of particular
worth.
3. Surface Imprinting
Molecular imprinting has been considered one of the most promising techniques for the
preparation of synthetic receptors. In spite of the ease of the conventional imprinting
methodology and its associated success with the imprinting of small molecules, the approach
has its limititation for the imprinting of protein macromolecules. The major problem during
templating of large molecules is the poor efficiency of specific binding due to the multitude
of functional sites at these molecules, as well as the limited diffusion of the template
molecules into and out of an imprinted polymer network and the incompatibility of the fragile
protein template with the imprinting conditions. Confining the recognition sites of molecular
imprinted polymers onto the surface of matrix is a technique which has been developed to
circumvent the problems associated with the imprinting of biological macromolecules in
aqueous solution [56].
Today, surface imprinting has been widely studied as one method to improve the
performance of molecular imprinting polymers, for it can resolve the problems of limited
mass transfer and template molecule removal often associated with the traditional molecular
imprinting techniques, especially when imprinting biological macromolecules. Zhao et al.
[57, 58] simultaneously prepared calcium phosphate/alginate hybrid polymer microspheres
with bovine serum albumin embedded and coating on the surface. It is found that the surface
imprinted beads exhibited better imprinting efficiency and higher rebinding capacity.
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