Molecularly Imprinted Au Nanoparticle Composites for Selective Sensing Applications - Designing Receptors for the Next Generation of Biosensors - page 189

Fig. 2 Schematic presentation for the imprinting of molecular recognition sites into a bis-
aniline-cross-linked Au NPs matrix for the specific sensing of a target molecule. Adapted with
permission from ref. 52. Copyright 2011 American Chemical Society

to the target analyte structure. Upon reaction of the vacant imprinted matrix with
the analyte, the affinity interactions between the analyte and the matrix facilitate
its concentration within the imprinted sites. These recognition events are, then,
transduced by a physical signal proportional to the concentration of the analyte.
The high affinity of the target analytes to the imprinted sites in the bis-aniline-
cross-linked Au NPs composites is reflected by high association constants, typically
ranging between 10 7 M 1 and 10 12 M 1 , resulting in low detection limits (lowest
detectable concentrations) for the sensing of different imprinted substrates by these
matrices (for further information, vide infra ). Furthermore, due to the delicate process
of imprinting, the imprinted matrices demonstrate an impressive selectivity in the
analysis of different substrates, and as will be shown, in addition to stereoselectivity, in
some cases chiroselectivity can also observed (e.g., see Sect. 2.3 ).
An important issue relates to the selection of the readout technique. The appropriate
choice of an analytical methodology that is used for the transduction of the recognition
signals, upon the binding of the analyte to the matrix, depends substantially on the
chemical and physical properties of the target analyte. For example, the association
of nitro-aromatic explosive compounds with the bis-aniline-cross-linked Au NPs
composite by -donor-acceptor interactions can be followed by the electrochemical

reduction of the nitrobenzene units associated with these explosives to hydroxylamine
groups [ 62 , 63 ]. Using the inherent electrochemical activity of nitro-aromatic
explosives and the three-dimensional electronic conductivity by the Au NPs in the
bis-aniline-cross-linked matrix, an electrochemical sensor for explosives, such as

p