On the Enhanced Antibacterial Activity of Antibiotics Mixed with Gold Nanoparticles.

G L Burygin,N G Khlebtsov,A N Shantrokha,L A Dykman,B N Khlebtsov,V A Bogatyrev

doi:10.1007/s11671-009-9316-8

Abstract

The bacterial action of gentamicin and that of a mixture of gentamicin and 15-nm colloidal-gold particles onEscherichia coliK12 was examined by the agar-well-diffusion method, enumeration of colony-forming units, and turbidimetry. Addition of gentamicin to colloidal gold changed the gold color and extinction spectrum. Within the experimental errors, there were no significant differences in antibacterial activity between pure gentamicin and its mixture with gold nanoparticles (NPs). Atomic absorption spectroscopy showed that upon application of the gentamicin-particle mixture, there were no gold NPs in the zone of bacterial-growth suppression in agar. Yet, free NPs diffused into the agar. These facts are in conflict with the earlier findings indicating an enhancement of the bacterial activity of similar gentamicin–gold nanoparticle mixtures. The possible causes for these discrepancies are discussed, and the suggestion is made that a necessary condition for enhancement of antibacterial activity is the preparation of stable conjugates of NPs coated with the antibiotic molecules.

Highlights

Over the recent decade, gold nanoparticles (NPs) [1–3] have attracted significant interest as a novel platform for various applications such as nanobiotechnology and biomedicine [4–7] because of convenient surface bioconjugation [8] with molecular probes and remarkable plasmon-resonant optical properties [9]
We have studied the effect of 16-nm gold NPs on the antibacterial activity of gentamicin
Within the limits of experimental error, no differences have been found between the antibacterial activity of gentamicin and that of a gentamicin–gold NP mixture at various gentamicin and particle concentrations

Summary

Introduction

Gold nanoparticles (NPs) [1–3] have attracted significant interest as a novel platform for various applications such as nanobiotechnology and biomedicine [4–7] because of convenient surface bioconjugation [8] with molecular probes and remarkable plasmon-resonant optical properties [9]. Published examples include applications of NPs to biosensorics [10], genomics [11, 12], clinical chemistry [13], immunoassays [14], immune response enhancement [15], detection and control of microorganisms [16], optical imaging of biological cells (including cancer cell imaging with resonance scattering [17, 18], optical coherence tomography [19], two-photon luminescence [20], and photoacoustic [21, 22] techniques), cancer cell photothermolysis [23, 24], and targeted delivery of drugs or genetic and immunological substances [25–29]. Gu et al [40] synthesized stable gold NPs covered with vancomycin and Nanoscale Res Lett (2009) 4:794–801 showed significant enhancement of antibacterial activity for this conjugate, in comparison with the activity of the free antibiotic. A similar result was reported for ciprofloxacin conjugated with Au/SiO2 core/shell NPs [41]

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Results

Conclusion