Technologies

With diabetes mellitus, the body either fails to produce or to respond to insulin, which regulates glucose metabolism, resulting in large fluctuations in blood glucose levels. These fluctuations can cause a range of serious complications. Treatment generally consists of self-regulation of blood glucose levels through frequent monitoring, diet, medication, and insulin injection. Most patients measure their glucose levels by withdrawing small samples of blood using a "finger-stick" apparatus followed by electrochemical detection of a glucose oxidation product. This measurement is painful, inconvenient and can result in uneven monitoring with risk of secondary complications. A new blood glucose assay addressing these issues is desirable.

Ex vivo glucose was quantitatively assayed with EG3 self assemble coated AgFON substrates, mounted into a small volume flow cell. EG3-modified AgFON sensors were incubated in saline solution (pH = 7.4) containing glucose concentrations from 0-450 mg/dL (0-25 mM). A HeNe laser was used to produce the 632.8 nm excitation wavelength and the SERS spectra measured. The EG3-modified AgFON sensor quantitatively detected glucose over the physiological range examined.

In vivo analysis was also demonstrated with a fiber optic SERS glucose sensor surgically implanted in diabetes induced Sprague-Dawley rats. Raman spectra were collect via the optical fiber as the glucose levels of the rats were varied by injection of glucose or insulin and compared versus a standard laboratory glucose assay. The SERS measurements fell within the acceptable range and the data compared favorably with the previous in vitro results. The biosensor system has been demonstrated for blood glucose monitoring and promises similar potential for other critical biological analytes.