Massively parallel
spectroscopy (MPS) of many single nanoparticles
in an aqueous dispersion is reported. As a model system, bioconjugated
photon-upconversion nanoparticles (UCNPs) with a near-infrared excitation
are prepared. The UCNPs are doped either with Tm3+ (emission
450 and 802 nm) or Er3+ (emission 554 and 660 nm). These
UCNPs are conjugated to biotinylated bovine serum albumin (Tm3+-doped) or streptavidin (Er3+-doped). MPS is correlated
with an ensemble spectra measurement, and the limit of detection (1.6
fmol L–1) and the linearity range (4.8 fmol L–1 to 40 pmol L–1) for bioconjugated
UCNPs are estimated. MPS is used for observing the bioaffinity clustering
of bioconjugated UCNPs. This observation is correlated with a native
electrophoresis and bioaffinity assay on a microtiter plate. A competitive
MPS bioaffinity assay for biotin is developed and characterized with
a limit of detection of 6.6 nmol L–1. MPS from complex
biological matrices (cell cultivation medium) is performed without
increasing background. The compatibility with polydimethylsiloxane
microfluidics is proven by recording MPS from a 30 μm deep microfluidic
channel.
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