Sensing and detecting disease biomarkers
Potential threats to the body’s well-being include foreign substances from the environment such as bacteria or pollen. Substances formed within the body such as toxins or even the body’s own tissue cells (hence the term autoimmune response) can also trigger an immune response. Antibodies are formed by the body to fight the enemies and any substance inducing formation of antibodies is called an antigen. The latter are typically located on the surface of suspect cells. The antibody binds to its specific antigen in a lock-and-key fashion immobilising it until other immune cells can destroy it or take it away. A series of experimental observations demonstrated that antibodies loaded onto an electro-conductive matrix (one capable of conducting electricity) produced an electrical current when they transiently bound to their antigens. European researchers sought to establish the nature and origin of the signal transduction mechanism at these nanostructured interfaces with funding for the ‘Electronic immuno-interfaces and surface nanobiotechnology: A heterodoxical approach’ (Elisha) project. Advanced understanding of mechanisms together with creation of appropriate specialised electronics led to the development of a variety of novel, low-cost and reliable immunosensors for medical diagnostic use. Elisha fabrication protocols enabled production of an immunosensor capable of detecting the prostate cancer marker, prostate-specific antigen (PSA). PSA was detectable at much lower levels than those present in the blood, the conventional biological sample for screening. Similar results were also achieved for a biomarker of trauma, such as that produced by stroke or heart attack. Another sensor detected a biomarker of micro-haemoglobinuria, a condition in which small amounts of blood are passed into the urine. The Elisha immunosensor systems were fabricated in simple portable devices incorporating rapid signal processing algorithms. They could easily be used in mobile applications (ambulances) as well as home healthcare for immediate data processing as well as filtering of non-specific binding responses. The Elisha method is thus a template from which innumerable immunosensors could be developed for rapid and reliable detection of antigens present in very low quantities. Its commercialisation potential is exciting and implementation should greatly enhance medical diagnostics and human health.