Biomedical Engineering Reference
In-Depth Information
lagged far behind the output of research laboratories due to problems with stability and
sensitivity, and quality-assurance issues.
More research is needed in the future to enhance the generated sensor signal by increas-
ing the sensitivities of the transducers while reducing background noise. Some examples
where enhanced sensitivity of the transducer has been demonstrated include the detection
of a single virus particle (1). This has been possible due to the miniaturization of the trans-
ducers to one-dimensional (1D) nanostructured materials. Another advantage of 1D-
nanostructured materials is the possibility of fabricating miniaturized sensor devices and
the development of high-density arrays for the simultaneous analysis of a range of differ-
ent analytes as demonstrated recently in the multiplexed detection of various cancer
marker proteins up to 0.9 pg/mL levels (2). Also, 1D-nanostructured materials are
extremely attractive for nanoelectronics because they can function both as devices and as
the wires that access them.
Selectivity has also been a major issue in the development and application of biosensors.
Selectivity basically depends on the biorecognition elements used by the biosensor. Hence,
biotechnology and genetic engineering should provide improved molecular recognition
elements that are tailored toward specific analytes of interest. Biotechnology will also be
central in the future to improve the stability of the recognition elements, life usefulness,
and for the development of aptamers. Aptamers are synthetic single-stranded DNA or
RNA oligonucleotide sequences with the ability to recognize various target molecules
with high affinity and specificity. Biosensor innovations could also benefit from the
advancement of intelligent instrumentation, electronics, and multivariate signal-process-
ing methods. In conclusion, we will definitely see an increasing role played by these bio-
logical-oriented devices in providing powerful analytical tools to the medical,
environmental, military, agricultural, and food-safety sectors where rapid, affordable, and
high sensitivity and specificity measurements are required.
23.2.2
Biomimetic Sensor Designs
Biosensors inherently comprise a biological or biologically derived sensing element inti-
mately associated with, or integrated within, a physicochemical transducer. Over 1,500 arti-
cles are published each year describing the various permutations of sensing element and
transducer (3,4). Professor Anthony Turner (personal communication, 2005) from Cranfield
University at Silsoe informs us that these are applied mainly in medical diagnostics (5), in
environmental diagnostics (6), in the food industry (7), and for crime prevention and secu-
rity (8). The most significant impact of biosensors till date has been in the field of diabetes,
where mediated amperometric biosensors account for over $4 billion in sales.
Until now, however, no device has come close to delivering a truly one-step procedure.
In the immediate future we can expect to see new technology to deliver this objective. The
development of suitably robust biosensors for many situations outside glucose monitor-
ing has been hindered by several problems associated with the properties of biological
material. The search for possible solutions to these problems has led to the development
of biomimetic systems such as the electronic nose, which shows excellent practical poten-
tial for the detection of disease and infections (9).
An alternative approach has been to seek synthetic analogs of natural receptors and
antibodies using supramolecular systems. If nature can produce nanomaterials with
recognition and functional properties by evolution, molecular engineers should be able to
accomplish comparable, but broader capabilities by design, guided by examples from liv-
ing systems. One of the most promising areas of biomimetics is molecularly imprinted
polymers (MIPs) (10). A key element here is the need for rational design (11). The ability
