In-situ detection of density alteration in non-physiological cells with polarimetric tilted fiber grating sensors

• The polarimetric tilted fiber grating as a rapid, high sensitivity and simple biosensor platform was proposed.
• In-situ detection of “Density Alteration in Non-physiological Cells” (DANCE) was demonstrated.
• The combination of a micro-fluidic technique with the fiber grating results in sub-microliter required analyte volumes.
• The study of DANCE helps to the understanding of drug resistance, discovery of new physiological or pathological properties of cells.

Tilted fiber Bragg grating (TFBG) biosensors can be used as a cost-effective and relatively simple-to-implement alternative to well established biosensor platforms for high sensitivity biological sample measurements in situ or possibly in vivo. The fiber biosensor presented in this study utilizes an in-fiber 12° tilted Bragg grating to excite a strong evanescent field on the surface of the sensor over a large range of external medium refractive indices. The devices have minimal cross-sensitivity to temperature and their fabrication does not impact the structural integrity of the fiber and its surface functionalization. Human acute leukemia cells with different intracellular densities and refractive index (RI) ranging from 1.3342 to 1.3344 were clearly discriminated in-situ by using the differential transmission spectrum between two orthogonal polarizations for the last guided mode resonance before “cut-off”, with an amplitude variation sensitivity of 1.8×104 dB/RIU, a wavelength shift sensitivity of 180 nm/RIU, and a limit of detection of 2×10−5 RIU. The detection process was precisely controlled with a micro-fluidic chip which allows the measurement of nL-volumes of bio-samples. The proposed in-fiber polarimetric biosensor is an appealing solution for rapid, sub-microliter dose and highly sensitive detection of analytes at low concentrations in medicine, chemical and environmental monitoring. @ 2013 Elsevier B.V. All rights reserved.