The overall goal of this research is to develop a new point-of-care system for early detection and
characterization of cardiac markers to aid in diagnosis of acute coronary syndrome. The envisioned final technology
platform incorporates functionalized gold colloidal nanoparticles trapped at the entrance to a nanofluidic device
providing a robust means for analyte detection at trace levels using surface enhanced Raman spectroscopy (SERS).
To discriminate a specific biomarker, we designed an assay format analogous to a competitive ELISA. Notably, the
biomarker would be captured by an antibody and in turn displace a peptide fragment, containing the binding epitope
of the antibody labeled with a Raman reporter molecule that would not interfere with blood serum proteins. To
demonstrate the feasibility of this approach, we used C-reactive protein (CRP) as a surrogate biomarker. We
functionalized agarose beads with anti-CRP that were placed outside the nanochannel, then added either
Rhodamine-6-G (R6G) labeled-CRP and gold (as a surrogate of a sample without analyte present), or R6G labeled
CRP, gold, and unlabeled CRP (as a surrogate of a sample with analyte present). Analyzing the spectra we see an
increase in peak intensity in the presence of analyte at characteristic peaks for R6G specifically, 1284 and1567 cm-
1. Further, our results illustrate the reproducibility of the Raman spectra collected for R6G-labeled CRP in the
nanochannel. Overall, we believe that this method will provide the advantage of sensitivity and narrow line widths
characteristic of SERS as well as the specificity toward the biomarker of interest.
According to the World Health Organization, cardiovascular disease is the most common cause of death in the world. In
the US, over 115 million people visit the emergency department (ED), 5 million of which may have acute coronary
syndrome (ACS). Cardiac biomarkers can provide early identification and diagnosis of ACS, and can provide
information on the prognosis of the patient by assessing the risk of death. In addition, the biomarkers can serve as criteria
for admission, indicate possibility of re-infarction, or eliminate ACS as a diagnosis altogether. We propose a SERSbased
multi-marker approach towards a point-of-care diagnostic system for ACS. Using a nanofluidic device consisting
of a microchannel leading into a nanochannel, we formed SERS active sites by mechanically aggregating gold particles
(60 nm) at the entrance to the nanochannel (40nm×1μm). The induced capillary flow produces a high density of
aggregated nanoparticles at this precise region, creating areas with enhanced electromagnetic fields within the
aggregates, shifting the plasmon resonance to the near infrared region, in resonance with incident laser wavelength. With
this robust sensing platform, we were able to obtain qualitative information of brain natriuretic peptide (biomarker of
ventricular dysfunction or pulmonary stress), troponin I (biomarker of myocardial necrosis), and C-reactive protein
(biomarker of inflammation potentially caused by atherosclerosis).
Alzheimer's disease (AD), a neurodegenerative disease and the most common cause of dementia, affects 4.5 million
people according to the 2000 US census and is expected to triple to 13.2 million by the year 2050. Since no definitive
pre-mortem tests exist to distinguish AD from mild cognitive impairment due to the natural aging process, we focus on
detecting the beta amyloid (Aβ) protein, the primary component of the senile plaques characteristic of AD. We
specifically detect cytotoxic species of Aβ by exploiting surface enhanced Raman scattering (SERS). Using a
nanofluidic device with a bottleneck shape (a microchannel leading into a nanochannel); we trapped gold colloid
particles (60 nm) at the entrance to the nanochannel, with Aβ restricted within the interstices between the aggregated
nanoparticles. The continuous flow generated from pumping the solution into the device produced size-dependent
trapping of the gold colloid particles, resulting in a high density of aggregated nanoparticles at this precise region,
creating localized "hot spots" in the interstitial region between nanoparticles, and shifting the plasmon resonance to the
near infrared region, in resonance with incident laser wavelength. With this robust sensing platform, we were able to
obtain concentration-dependent SERS spectra of Aβ and of different proteins present in the cerebrospinal fluid of
healthy people and people with Alzheimer's disease.
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