To
enhance signal acquisition stability and diminish background
interference for conventional flow bead-based fluorescence detection
methods, we demonstrate here an exceptional microfluidic chip assisted
platform by integrating near-infrared optical tweezers with upconversion
luminescence encoding. For the former, a single 980 nm laser is employed
to perform optical trapping and concurrently excite upconversion luminescence,
avoiding the fluctuation of the signals and the complexity of the
apparatus. By virtue of the favorable optical properties of upconversion
nanoparticles (UCNPs), the latter is carried out by employing two-color
UCNPs (Er-UCNPs and Tm-UCNPs) with negligible spectral overlaps. With
the assistance of the double key techniques, we fabricated complex
microbeads referred to a UCNPs–miRNAs–microbead sandwich
construct by a one-step nucleic acid hybridization process and then
obtained uniform terrace peaks for the automatic and simultaneous
quantitative determination of miRNA-205 and miRNA-21 sequences with
a detection limit of pM level on the basis of a special home-built
flow bead platform. Furthermore, the technique was successfully applied
for analyzing complex biological samples such as cell lysates and
human tissue lysates, holding certain potential for disease diagnosis.
In addition, it is expected that the flow platform can be utilized
to investigate many other biomolecules of single cells and to allow
analysis of particle heterogeneity in biological fluid by means of
optical tweezers.