Monitoring Corona Exchange Dynamics on Single-Walled Carbon Nanotubes Using Multiplexed Fluorophore Quenching

Abstract

Single-walled carbon nanotubes (SWCNTs) non-covalently modified with DNA have been widely implemented as probes for near-infrared molecular sensing and imaging in biological systems. However, these constructs show poor stability in biomolecule-rich, in vivo environments leading to attenuation of sensor response. To study the relevant interactions that occur between DNA-SWCNTs in a biological environment, we develop a method to capture real-time binding behavior of fluorophore-labeled biomolecules, utilizing the SWCNT surface as a fluorescence quencher. We apply this assay to monitor corona dynamics of proteins adsorbing on single-stranded DNA (ssDNA) functionalized SWCNT dopamine sensor. We show the proteins albumin and fibrinogen adsorb to varying degrees on the ssDNA-SWCNT surface. Fibrinogen adsorption was 168% greater than that of albumin on a mass basis. Furthermore, fibrinogen induced more DNA desorption than albumin. These results are recapitulated by the respective kinetic rate constants for adsorption and desorption, calculated by fitting experimental adsorption data to a competitive adsorption model. Greater fibrinogen adsorption and induced DNA desorption coincide with a 78.2% reduction in dopamine response compared to 52.2% for albumin. We use this method to further study the passivation of ssDNA-SWCNTs with PEGylated phospholipid, a molecule shown to improve biocompatibility of nanoparticle platforms. The non-covalent interaction causes marginal desorption of DNA but significantly reduces subsequent adsorption of fibrinogen. The mitigated protein adsorption by phospholipid-PEG coincides with a reduction in sensor response attenuation. This methodology presents a generic yet robust protocol to track solution-phase competitive adsorption of multiple chemical species on a nanoparticle surface and to relate these phenomena to sensor efficacy.