Plastic Antibodies - Designing Receptors for the Next Generation of Biosensors - page 120

Under optimized rebinding conditions MIP NPs were able to remove selectively
500-1,000 ppb of uranyl ions from water samples, about 25% more than non-
imprinted materials. When tested with spiked environmental waters, the recovery
performance was 94% for ground water. However, for salt water samples, the
recovery was lower (70%). Several groups also investigated the possibility of
using MIP NPs with magnetic cores [ 118 ]. Wang and coauthors prepared Fe 3 O 4
magnetic NPs coated with a silica layer imprinted for estrone [ 119 ]. MIP NPs
rebound estrone about 3.6-times more effectively and specifically than the
corresponding non-imprinted particles. However, the product was not tested in
“real” samples to assess its performance as a rapid recovery affinity material. Li
and coauthors prepared surface-imprinted magnetic polystyrene nanoparticles for
bovine hemoglobin through a multi-stage core-shell polymerization process [ 120 ].
It involved the use of 3-aminophenylboronic acid (APBA) as functional and cross-
linking monomer. In fact, thanks to its aqueous solubility and the variety of
reversible interactions which it establishes with amino acids, APBA is particularly
suitable for protein imprinting [ 121 ]. Magnetite core nanoparticles were coated
with MIP shells created by the polymerization of APBA in the presence of the
template. The final size of the coated particles reached a diameter of 480 nm with a
15-20 nm thick MIP film. The core-shell MIP NPs exhibited superparamagnetic
properties suitable for facile separation in a magnetic field. Additionally, they
showed rapid rebinding kinetics (30-120 min), good specificity and selectivity for
the template, as well as a very high adsorption capacity of around 45.5 mg g 1 . Such
a high capacity is unusual for this kind of material and together with their magnetic
properties makes these imprinted nanoparticles very attractive for enrichment
of low concentration proteins in proteomics. Another very interesting core-shell
approach for preparing magnetic MIP NPs for proteins has been developed by Zhou
and coauthors, who imprinted human hemoglobin in a polydopamine (PDA) layer
synthesized on the surface of magnetic Fe 3 O 4 nanoparticles [ 122 ]. The synthesized
nanoparticles exhibited strong recognition affinity towards hemoglobin, with a
dissociation constant of 18.13 gmL 1 . The binding capacity of MIP NPs was

22.3 m gmg 1 . In addition, they had a very good selectivity evaluated against proteins
such as myoglobin, horse radish peroxidase, and cytochrome c . The use of PDA
seems to be particularly suitable for protein imprinting, because it is hydrophilic,
biocompatible, and has amino and catechol groups which can help in establishing
interactions with the macromolecular template. Moreover, the thickness of the PDA
layer can be very easily tuned by changing the polymerization time [ 123 ].

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3.6 The Future: Biologically Active MIP Nanoparticles

Undoubtedly the most interesting, albeit distant future application for MIP NPs, is
the creation of biologically active systems that can be used as drugs, antibody, or
enzyme substitutes in vivo. The first example of water-soluble MIP NPs
demonstrating biological activity dates back to 2006 when Piletsky and coauthors
investigated the possibility of enhancing the photosynthetic reaction using MIPs