Aspects of recent development of immunosensors - Electrochemical Sensors, Biosensors and Their Biomedical Applications - page 247

9.4 CONCLUSION AND FUTURE TRENDS
Immunosensors incorporate the specifi c immunochemical reaction with the modern
transducers including electrochemical (potentiometric, conductometric, capacitative,
impedance, amperometric), optical (fl uorescence, luminescence, refractive index), and
microgravimetric transducers, etc. [1]. These immunosensor devices with dramatic
improvements in the sensitivity and selectivity possess the abilities to investigate the
reaction dynamics of antibody-antigen binding and the potential to revolutionize con-
ventional immunoassay techniques. With the rapid development of immunological rea-
gents and detection equipments, immunosensors have allowed an increasing range of
analytes to be identifi ed and quantifi ed. In particular, simple-to-use, inexpensive and
reliable immunosensing systems have been developed to bring immunoassay tech-
nology to much more diverse areas, such as outpatient monitoring, large screening
programs, and remote environmental surveillance [9]. However, there are still some
unsolved problems associated with the immobilization of immunoactive entities, non-
specifi c adsorption from sample backgrounds (e.g. blood, serum, plasma, urine, and
saliva) and practical applications of various transducer devices.
The current development of new immunosensors should aim at solving the prob-
lems of clinical analysis in medicine and of chemical analysis in the food industry and
biotechnology. The development trends of immunosensors are likely to be primarily
driven by the requirements of analytical practice on the improvement in sensitivity,
selectivity, rapidity, and especially effi ciency of assays (i.e. immunosensing array or
microfl uidic system). Immunosensors with lowered detection limits and increased sen-
sitivities have been developed in various fi elds, particularly in clinical analysis. For
example, the sandwich immunoassay using enzyme-functionalized liposomes as the
catalytic label is proposed to obtain the substantially improved assay sensitivity, as val-
idated in the immunoassay of cholera toxin [170]. Meanwhile, as the latest paradigm
of development topic, nanomaterials with unique chemical and physical properties
should continue to be exploited to offer important possibilities for new immunosensor
designs [29]. A noticeable development trend is also observed in the development of
immunosensors combining with other techniques such as fl ow injection analysis (FIA)
or capillary electrophoretic (CE) analysis, to complement and improve the present
immunoassay methods [171-172]. Moreover, the miniaturization and automation of
immunosensing devices should be another important intention of development to facil-
itate the signifi cantly shortened analysis time and simplifi ed analytical procedure (i.e.
one-step analysis). Of note, protein and antibody array technologies are envisaged to
have potential for biomedical and diagnostic applications in recent years [173-177].
Belov et al. have proposed a novel immunophenotyping method for leukemias using
a cluster of differentiation antibody microarray [174]. A microarray of enzyme-linked
immunosorbent assay has been developed for autoimmune diagnosis of systematic
rheumatic disease, where the high titers of antinuclear antibodies against various
nuclear proteins and nucleoprotein complexes might be detected with high through-
put [177]. At the same time, the screen-printing techniques may also appear to be the
most promising technology for immunosensor array to be commercialized on a large