Examples of microfluidic designs for LSPR biosensors.
(A) Scheme of an integrated LSPR optofluidic platform that includes an Au nanostructured surface, a microfluidic chamber with in and out channels (the chamber has integrated micropillar array to trap bead-bound target cells), and a top layer as structural support for light alignment and sample delivery. A scheme representing the different steps of the process (cell separation, incubation, and subsequent detection of secreted cytokines) is also shown. Adapted and reprinted with permission from . © Copyright 2014 American Chemical Society. (B) Scheme showing the microfluidic design for the simultaneous detection of six cytokines with a nanorod microarray. It consists of eight parallel microfluidic channels (each one with independent inlet and outlet for sample delivery, which are perpendicularly located to the nanoparticle array). A nonpermanently bonded PDMS mask has been used for patterning the Au nanorod stripes (2 cm length and 50 μm pitch, as can be seen in the dark-field microscopy images). Subsequent antibody conjugation was done before removing the mask and incorporating the final one. The current chip design integrates 480 AuNR microarray sensor spots, as can be seen in the final microarray chip layout (60 antibody-functionalized AuNR stripes segmented by 8 microfluidic detection channels). The obtained calibration curves are also shown. Adapted and reprinted with permission from . © Copyright 2015 American Chemical Society. (C) Label-free detection of exosomes with an nPLEX sensor. From left to right: Pictures of the Au nanoholes used as LSPR sensor, including an SEM image where the exosomes are captured by the antibody-coated surface, are shown; picture of the microfluidic cell with 12 independent channels and with three differentiated sensing areas; a photograph of the miniaturized imaging version of the setup, including the nPLEX chip. Reprinted with permission from Macmillan Publishers Ltd.: Nature Biotechnology . © Copyright 2014. (D) Scheme of a nanoplasmonic electrical field-enhanced resonating device (NE2RD). The 3D-oriented Au nanoparticle substrate and the portable setup based on a disposable microfluidic chip with eight individual incubation chambers are shown. Images reproduced with permission from . © Copyright Proceedings of the National Academy of Science of the United States of America.