Micro- and nanoimmunosensors: technology and applications

Abstract

Since the technique of surface plasmon resonance (SPR) [1] was first applied to the biosensing of an antibody-antigen interaction, the research and technological development of immunosensors have experienced an exponential growth. This technique showed the enormous potential for the direct, real-time and label-free detection of an immunoreaction. The success of the biosensor technology can be deduced from the increasing number of commercially available instruments. This reflects the growing acceptance of the methodology and the increased availability of the instrumentation. But there is still a long way to go to replace completely conventional immunoassays by biosensor technology in many fields and, especially, in clinical diagnostics [2]. Besides the excellent results obtained with the existing immunosensor technologies (mainly related to SPR sensors) [2], we still need biosensors able to detect, in a direct way, very low levels (picomolar to femtomolar) of a great number of chemical and biochemical substances in the areas of environmental monitoring, industrial and food processes, health care, biomedical technology, clinical analysis, etc. Ideally, we must achieve the fabrication of immunosensors with the following characteristics: very high sensitivity and selectivity, broad dynamic range, immunity to matrix effects, capable of multianalyte determination at the same time, with short analysis time, reversible, stable, simple to operate, robust, cheap and of small size [3]. In order to achieve all or most of the aforementioned characteristics, the application of the recent progress in microand nanotechnologies promises to revolutionise the applications of immunosensors [4]. Indeed, the application of such technologies is allowing the miniaturisation of the biosensor devices, the development of microfluidic platforms and the increase in the sensitivity of the immunoassays performed. We are assisting in the appearance of a cascade of new immunosensor devices at the microand nanoscale which could be easily integrated in portable “lab-on-a-chip” platforms to perform “point-of-care” analysis and which in the future could even work inside the human body as “nano-sentinels”.