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Single Gold Nanoparticle Plasmonic Spectroscopy for Study of Chemical-Dependent Efflux Function of Single ABC Transporters of Single Live Bacillus subtilis Cells

Abstract

ATP-binding cassette (ABC) membrane transporters serve as self-defense transport apparatus in many living organisms and they can selectively extrude a wide variety of substrates, leading to multidrug resistance (MDR). The detailed molecular mechanisms remain elusive. Single nanoparticle plasmonic spectroscopy highly depend upon their sizes, shapes, chemical and surface properties. In our previous studies, we have used size-dependent plasmonic spectra of single silver nanoparticles (Ag NPs) to study real-time efflux kinetics of ABC (BmrA) transporter and MexAB-OprM transporter in single live cells (gram-positive and gram-negative bacterium), respectively. In this study, we prepared and used purified, biocompatible and stable (non-aggregated) gold nanoparticles (Au NPs) (12.4 ± 0.9 nm) to study efflux kinetics of single BmrA membrane transporters of single Bacillus subtillis live cells, aiming to probe chemical dependent efflux functions of BmrA transporters and their potential chemical sensing capability. Similar to those observed using Ag NPs, accumulation of the intracellular Au NPs in single live cells (WT and ΔBmrA) highly depends upon the cellular expression of BmrA and NP concentration (0.7 and 1.4 nM). The lower accumulation of intracellular Au NPs in WT (normal expression of BmrA) than ΔBmrA (deletion of bmrA) indicates that BmrA extrude the Au NPs out of the WT cells. The accumulation of Au NPs in the cells increases with NP concentration, suggesting that the Au NPs most likely passively diffuse into the cells, similar to antibiotics. The result demonstrates that such small Au NPs can serve as imaging probes to study the efflux function of BmrA membrane transporter in single live cells. Further, the dependence of accumulation rate of intracellular Au NPs in single live cells upon the expression of BmrA and concentration of the NPs is about twice higher than that of the same sized Ag NPs. This interesting finding suggests chemical-dependent efflux kinetics of BmrA and that BmrA could distinguish nearly identical sized Au NPs from Ag NPs and might possess chemical sensing machinery.

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Publication details

The article was received on 02 Nov 2017, accepted on 28 Jan 2018 and first published on 30 Jan 2018


Article type: Paper
DOI: 10.1039/C7AN01787A
Citation: Analyst, 2018, Accepted Manuscript
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    Single Gold Nanoparticle Plasmonic Spectroscopy for Study of Chemical-Dependent Efflux Function of Single ABC Transporters of Single Live Bacillus subtilis Cells

    L. M. Browning, K. J. Lee, P. K. Cherukuri, T. Huang, P. Songkiatisak, S. Warren and X. N. Xu, Analyst, 2018, Accepted Manuscript , DOI: 10.1039/C7AN01787A

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