Fast and precise blood group detection can be a matter of life or death for patients undergoing transfusion medicine. Now, a fiber optic sensor based on surface plasmon resonance (SPR) could be just the answer, with designers claiming that it eliminates the possibility of false measurements. The probe’s creators at Friedrich-Schiller University, along with their collaborators at the University of Central Florida in the US and at the Institute of Photonic Sciences (ICFO) in Barcelona, Spain, are in talks with a number of firms in India and elsewhere to commercialize their approach. They say that the probe can provide more reliable and accurate blood group information than currently available methods. Working as an Alexander von Humboldt Research Fellow at Friedrich-Schiller University in Jena, Germany, Dr. Anuj Sharma headed up the research, which promises to provide physicians with an errorless means of testing human blood groups. “No doubt, easier techniques are already available for blood group detection. However, in a number of biomedical procedures, there is no space for error and/or false blood group measurements,” said Dr. Anuj Sharma, who headed up the research. “Transfusion of mismatched blood groups to patients can cause fatal inflammatory and hemolytic reactions. Our sensor can be seriously useful in such applications.” Recent studies have linked blood group type with the risk of pancreatic cancer and malaria. Other applications of blood group detection include organ transplants, paternity testing and genetic linkage testing. Besides offering errorless blood group detection, the probe delivers results more quickly than is currently possible, which is particularly useful during emergency operations. Also, because of the high optical activity of surface plasmons, a much smaller blood sample is required. The probe design is described in the November/December 2009 issue of the Journal of Biomedical Optics. First, a few nanometers of an SPR-active metal, such as silver, are coated onto a small segment of optical fiber (typically 10 to 15 mm). The thin metal layer is then coated with a buffer that prevents any contaminants from depositing on top of the metal, as shown in Figure 1. Figure 1. Shown is a proposed fiber optic SPR sensor probe for detecting human blood groups. The output signal (P) exhibits a sharp dip at a resonance wavelength because of strong optical absorption by the surface plasmon wave (occurrence of SPR). δλSPR marks the shift in resonance wavelength. Images courtesy of Dr. Anuj Sharma. For actual measurements, the blood sample is brought into contact with the probe, and light is launched into the input end of the optical fiber. The resulting light emitted at the other end of the probe provides information such as resonant wavelength, from which blood group can be deduced. The researchers achieved optimum results using an optical fiber with a large core diameter and small sensing regions with silver layer thicknesses typically around 50 nm. And with an appropriate buffer solution, they found that they could reuse the probe. Sharma and his colleagues hope to extend the list of applications for the probe to detecting blood-sugar levels and various human diseases. “We plan to design optical sensors for other biomedical applications, both daily life as well as more sophisticated examples,” Sharma said. “We are also thinking of exploring techniques other than SPR for optical biosensing.” For more information about this work, please e-mail Sharma at: anujsharma@gmail.com.