Label-free techniques for detection of NAs.
(A) Hydrogel-embedded PC allows simple detection of DNA hybridization based on reflected light (i). Functionalization with probe strands and binding of target strands affect relative distance of PC beads and cause color shift (ii). Adapted from Ref.  with permission of The Royal Society of Chemistry. (B) Optical configuration of surface plasmon resonance phase imaging (SPR-PI), with polarizer P, wedge retardance plate W, and bandpass filter BP. An example of phase shift differences is also shown: horizontal stripes correspond to patterning with different biomolecular interactions, while vertical stripes are the imposed sinusoidal phase fringes. Adapted with permission from Ref. . Copyright 2011 American Chemical Society. (C) Schematic representation of miRNA detection based on LSPR, superimposed to AFM image of nanometric gold nanoprisms functionalized with single-stranded DNA complementary to target RNA. Adapted from Ref. .