Maria Sanchez-Purra
University of Massachusetts Boston
Dr. Maria Sánchez-Purrà received a Bacherlor's degree in Organic Chemistry, in 2008, and a PhD in Bioengineering, in 2015, from IQS School of Engineering in Barcelona, Spain. In her PhD, she worked in the development of polymeric and liposomal drug delivery nanocarriers for cancer therapy. In 2016, she moved to the US to work as a postdoctoral researcher for the NanoBiointerfaces Lab at the University of Massachusetts Boston, where she develops rapid diagnostics for the detection of infectious diseases.
Introduction
Zika and Dengue are mosquito-borne diseases that are currently a major global threat. They can co-circulate in endemic areas, as they are transmitted by the same vector and show similar non-specific symptoms with dramatically different outcomes. Because many outbreaks occur in areas that are resource-poor, assays that are user-friendly, inexpensive and require no power are in need for patient treatment, quarantining, and surveillance. Paper-based sandwich immunoassays, such as lateral flow assays (LFA), are attractive as point-of-care solutions as they have the potential for wider deployability than lab-based assays such as PCR. However, the low sensitivity of these assays imposes limitations on their ability to detect low biomarker levels, which is the case of Zika infections, co-infections with other viruses, and also for early diagnosis of any disease. Here, we exploit the high sensitivity of surface-enhanced Raman spectroscopy (SERS) in a multiplexed assay that can distinguish between Zika and Dengue non-structural protein (NS1) biomarkers.
Methods
Gold nanostars absorbing in the NIR range, which can provide a high SERS effect, were synthesized. Two Raman reporter molecules, BPE and 4-MBA, were absorbed onto the nanostars that were further conjugated to specific antibodies for Zika and Dengue NS1 biomarker, respectively. LFA were run in a dipstick conformation mixing the SERS-encoded nanostars with commercial NS1. When NS1 was present in the sample, the antibody sandwich was formed rendering a colored spot in the test line, that was analyzed with a Raman microscope.
Results
Using SERS allowed the detection of low concentrations of the viral biomarkers with a limit of detection of 15-fold and 7-fold, for ZIKV and DENV, lower than that of colorimetric LFA, being able to detect down to 0.72 ng/ml and 55.3 ng/ml of viral NS1, respectively.
Discussion
The combination of SERS with LFA can make a promising platform for a point-of-care device, as it can provide a much higher sensitivity than optical LFA devices, giving a result within minutes. In addition, it allowed the multiplexed detection of both biomarkers, which can help to decrease the amount of patient sample required for the test.
