We demonstrate the use of colloidal quantum dots (QDs) as refractive index signal amplifiers for the dual-mode, optical detection of biotin in streptavidin-functionalized porous silicon (PSi) biosensors. The nanoporous silicon host matrix was first analyzed to determine the relationship between different formation conditions, the resulting pore size distributions, and the efficiency with which different sized target molecules infiltrate and bind to the pore walls. Non-specific detection of glutathione conjugated with QDs was then demonstrated using PSi films with different average pore diameters. The specific detection of small biotin molecules was confirmed when the QD-biotin conjugates resulted in a six-fold increase in the reflectance fringe shift and a distinctive fluorescence spectrum upon exposure to an optimized, streptavidin-functionalized PSi sensor. A biotin detection limit of 0.5 fg/mm² is achievable.

Date Published: 19 February 2013
PDF: 11 pages
Proc. SPIE 8594, Nanoscale Imaging, Sensing, and Actuation for Biomedical Applications X, 859408 (19 February 2013); doi: 10.1117/12.2002889

Published in SPIE Proceedings Vol. 8594:
Nanoscale Imaging, Sensing, and Actuation for Biomedical Applications X
Alexander N. Cartwright; Dan V. Nicolau, Editor(s)