A Microfabricated Array Sensor for the Electrochemical Detection of Biological Molecules
The ability to detect ultra low concentrations of heme and hemoglobin in bodily fluids has great value in clinical and medical diagnostic applications. Clinical screening for many diseases, such as colorectal cancer and malaria, is predominantly related to the concentrations of hemoglobin or heme in different biofluids. The detection of porphyrins in urine, saliva, cerebrospinal fluid and swabs from the nasopharyngeal cavity may also be used to indicate infection, trauma or other frank diseases. The false positive rates experienced while analyzing the different fluids can be high and often leads to the use of expensive, invasive and stressful follow on tests like colonoscopies.
Researchers at The Johns Hopkins University Applied Physics Laboratory and the Bloomberg School of Public Health are developing a detection system, including a one-time use sensor array, for screening blood and other bodily fluids for the presence of heme or hemoglobin. This system utilizes well-known electrochemical principles, with some innovative modifications, to detect ultra low concentrations of heme in the presence of normal concentrations of hemoglobin. The sensor array consists of carefully cleaned and uniformly-thiolated, high-surface-area electrodes. The electrodes adsorb and concentrate trace amounts of heme present in the sample. The system can also be used for other third world medical applications in which the presence of blood is of diagnostic value, such as screening for the urinary form of shistosomiasis. The adsorbed molecules are detected and characterized by electrochemical techniques such as AC Voltommetry. JHUAPL has designed and tested several miniaturized, programmable electrochemical devices that are inexpensive to manufacture, and consume less than 5 mW power. The example in the figure shows the currents measured by the electrochemical system in blood containing about 90, 180 and 650 malarial parasites per microliter.
*Currently, JHU/APL is seeking a corporate partner for this technology