Over the past few years, ricin has been discussed frequently because of letters sent to high-ranking government officials containing the easily extracted protein native to castor beans. Ricin B chain, commercially available and not dangerous when separated from the A chain, enables development of ricin sensors while minimizing the hazards of working with a bioterror agent that does not have a known antidote. Recent events have increased the risk of ricin exposure for civilians, and there is a need for rapid, real-time detection of ricin. To this end, aptamers have been used recently as an affinity agent to enable the detection of ricin in food products via surface-enhanced Raman spectroscopy (SERS) on colloidal substrates. One goal of this work is to extend ricin sensing into human whole blood; this goal requires application of a commonly used plasmonic surface, the silver film-over-nanosphere (AgFON) substrate, which offers stable SERS enhancement factors of 106 in human whole blood. Herein, this aptamer-conjugated AgFON platform enabled ricin B chain detection even after the aptamer-modified substrate had dwelled for up to 10 days in human whole blood. Principle component analysis (PCA) of the SERS data clearly identifies the presence or absence of ricin B chain in blood.
Bibliographical noteFunding Information:
We gratefully acknowledge financial support from DARPA under SSC Pacific grants (N660001-11-1-4179). Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of DARPA. The included SAMDI MS measurements were performed by Andreea Stuparu and Milan Mrksich.
© 2016 American Chemical Society.