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Download fileDirect Surface Enhanced Raman Spectroscopic Detection of Cortisol at Physiological Concentrations
journal contribution
posted on 2020-01-07, 18:42 authored by T. Joshua Moore, Bhavya SharmaCortisol
is an important steroid hormone in human physiology. Variations
or abnormalities in the physiological cortisol levels control acute
and chronic stress response, as well as contribute to diseases and
syndromes including Addison’s disease and Cushing syndrome.
The ability to monitor cortisol levels in the physiological range
is key in diagnosis and monitoring of these conditions, where current
methodology for determination of cortisol levels relies on instrumentation
that requires extensive sample preparation, long run times, and is destructive to the
sample. Raman spectroscopy provides rapid sample analysis with relatively
simple instrumentation; however, Raman spectroscopy is an inherently
weak technique. To provide an enhanced Raman signal, we use surface
enhanced Raman spectroscopy (SERS) which utilizes oscillating electric
fields of metal nanoparticles, enhancing the overall electric field
and therefore resulting in an enhanced signal. We demonstrate SERS-based
detection of cortisol in the physiologically relevant range using
colloidal silver nanoparticles in ethanolic solutions and bovine serum
albumin. The SERS spectra obtained in an ethanol matrix demonstrate
a sigmoidal concentration response over the physiologically relevant
concentration range, with a limit of detection established at 177
nM. Analysis of cortisol solutions in a complex matrix (bovine serum
albumin in phosphate buffered saline) is also demonstrated through
the use of principal components analysis, a multivariate technique,
which shows the separation of cortisol in a linear fashion with respect
to cortisol concentration.