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Liquid Nebulization–Ion Mobility Spectrometry Based Quantification of Nanoparticle–Protein Conjugate Formation
journal contribution
posted on 2016-07-02, 00:00 authored by Seongho Jeon, Derek R. Oberreit, Gary Van Schooneveld, Christopher J. HoganDespite
the importance of examining the formation of nanoparticle–protein
conjugates, there is a dearth of routine techniques for nanoparticle–protein
conjugate characterization. The most prominent change to a nanoparticle
population upon conjugate formation is a shift in the nanoparticle
size distribution function. However, commonly employed dynamic light
scattering based approaches for size distribution characterization
are ineffective for nonmonodisperse samples, and further they are
relatively insensitive to size shifts of only several nanometers,
which are common during conjugate formation. Conversely, gas phase
ion mobility spectrometry (IMS) techniques can be used to reliably
examine polydisperse samples, and are sensitive to ∼1 nm size
distribution function shifts; the challenge with IMS is to convert
nanoparticle–protein conjugates to aerosol particles without
bringing about nonspecific aggregation or conjugate formation. Except
in limited circumstances, electrospray based aerosolization has proven
difficult to apply for this purpose. Here we show that via liquid
nebulization (LN) with online, high-flow-rate dilution (with dilution
factors up to 10 000) it is possible to aerosolize nanoparticle–protein
conjugates, enabling IMS measurements of their conjugate size distribution
functions. We specifically employ the LN-IMS system to examine bovine
serum albumin binding to gold nanoparticles. Inferred maximum protein
surface coverages (∼0.025 nm–2) from measurements
are shown to be in excellent agreement with reported values for gold
from quartz crystal microbalance measurements. It is also shown that
LN-IMS measurements can be used to detect size distribution function
shifts on the order of 1 nm, even in circumstances where the size
distribution function itself has a standard deviation of ∼5
nm. In total, the reported measurements suggest that LN-IMS is a potentially
simple and robust technique for nanoparticle–protein conjugate
characterization.