With an increasing globalisation as well as a growing population we are faced with different threats like terrorism, such as bioterrorism, influenza outbreaks and a number of environmentally hazardous chemicals. To be able to react in a fast and effective way whatever happens it is very important to develop cost effective detection methods which in a fast and reliable way can detect the presence of, for example, a pathogen (such as a bacterium or a virus) or a toxic compound (e.g. an environmental hazard). With a growing elderly population there is also a need of developing early detection methods which at an early stage can detect a disease or disorder, such as cancer or Alzheimer's disease for prevention or individualized and effective treatment.
Today, the above mentioned disease markers, pathogens and compounds are detected by the use of rather large sample volumes, such as in the μl range, e.g. in an Enzyme-linked immunosorbent Assay (ELISA). Additionally, the specificity and sensitivity of current detection methods is sometimes low. Commonly used methods are polymerase chain reaction (PCR), ELISA and enzyme-linked immunoassay (EIA). For the detection of microorganisms the said detection methods are often preceded by cultivation of the microorganism, e.g. virus or bacteria. Whereas this procedure increases the sensitivity of the method it also significantly decreases the speed of detection.
Presently several attempts are ongoing in which the detection methods are being miniaturised by the combination of antibodies, oligonucleotides or other recognition elements with state-of-the art nanotechnology1, 2. Hereby, extremely complex techniques are developed which combine micro-fluidics systems with the binding of the different components to micro or nanostructured surfaces3, wherein specific biological recognition elements are used. Detection of the binding between the compound and the antibodies or oligonucleotides can be determined by advanced methods such as altered conductance of nanowires4 or carbon nanotubes5 or altered resonance in a nano-cantilever6. In other cases increases in sensitivity have been obtained by the use of antibodies which have been bound to magnetic nanoparticles and the very specific identification obtained through oligonucleotide sequences7. In the different nanotechnology-related methods there is always a need to use different types of nanoparticles, nanowires etc. This is not completely unproblematic since the use of larger amounts of nanoparticles as well as nanotubes has an impact on the environment since they are potentially toxic. Additionally, methods based on state-of-the-art nanotechnology are presently complex and expensive. All the mentioned drawbacks may be reasons why these methods are not used on a large scale today. Thereby it is evident that there is a need for new techniques which are reliable, cost efficient and environmentally friendly at the same time as they are highly sensitive and with the potential to be used in a miniaturised system.