Formation and enhanced biocidal activity of water-dispersable organic nanoparticles

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Water-insoluble organic compounds are often used in aqueous environments in various pharmaceutical and consumer products. To overcome insolubility, the particles are dispersed in a medium during product formation1, but large particles that are formed may affect product performance and safety. Many techniques have been used to produce nanodispersions—dispersions with nanometre-scale dimensions—that have properties similar to solutions2,3,4. However, making nanodispersions requires complex processing, and it is difficult to achieve stability over long periods1. Here we report a generic method for producing organic nanoparticles with a combination of modified emulsion-templating5 and freeze-drying. The dry powder composites formed using this method are highly porous, stable and form nanodispersions upon simple addition of water. Aqueous nanodispersions of Triclosan (a commercial antimicrobial agent) produced with this approach show greater activity than organic/aqueous solutions of Triclosan.

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Figure 1: Characterization of solid nanocomposites and nanodispersions.
Figure 2: Comparison of conventional surfactant solubilization and nanodispersions of Oil-Red (OR).
Figure 3: Schematic/mechanistic representation of nanoparticle formation during freeze-drying.
Figure 4: Scanning electron microscopy images of freeze-dried atomized powders.
Figure 5: Evaluation of the minimum inhibitory concentration (MIC) of different forms of the antibacterial agent Triclosan.


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The authors thank IOTA NanoSolutions Limited for an Industrial Senior Research Fellowship (S.R.), the Royal Society for a University Research Fellowship (A.C.) and an Industry Fellowship (S.R.) and Research Councils UK for an Academic Fellowship (H.Z.). We also acknowledge the Centre for Materials Discovery (University of Liverpool) for access to analytical equipment and specifically J. Weaver for help conducting surface tension measurements. The EPSRC (grant GR/N39999/01 and Portfolio Partnership in Complex Materials Discovery EP/C511794/1), IOTA NanoSolutions Limited and Unilever are thanked for financial support.

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All authors contributed to the experimental programme, either through design of the experiment or practice. D.T. led the microbiological testing. H.Z., A.C. and S.R. co-wrote the manuscript.

Correspondence to Andrew I. Cooper or Steven P. Rannard.

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