Active Surface Hydrophobicity Switching and Dynamic Interfacial Trapping of Microbial Cells by Metal Nanoparticles for Preconcentration and In-Plane Optical Detection

Yuyeon Kim, Kwangyeong Jung, Jeehan Chang, Taejin Kwak, Youngwook Lim, Seonghak Kim, Jeonggeol Na, Jinwon Lee, Inhee Choi, Luke P. Lee, Dongchoul Kim, Taewook Kang

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

The surface hydrophobicity of a microbial cell is known to be one of the important factors in its adhesion to an interface. To date, such property has been altered by either genetic modification or external pH, temperature, and nutrient control. Here we report a new strategy to engineer a microbial cell surface and discover the unique dynamic trapping of hydrophilic cells at an air/water interface via hydrophobicity switching. We demonstrate the surface transformation and hydrophobicity switching of Escherichia coli (E. coli) by metal nanoparticles. By employing real-time dark-field imaging, we directly observe that hydrophobic gold nanoparticle-coated E. coli, unlike its naked counterpart, is irreversibly trapped at the air/water interface because of elevated hydrophobicity. We show that our surface transformation method and resulting dynamic interfacial trapping can be generally extended to Gram-positive bateria, Gram-negative bacteria, and fungi. As the dynamic interfacial trapping allows the preconcentration of microbial cells, high intensity of scattering light, in-plane focusing, and near-field enhancement, we are able to directly quantify E. coli as low as 1.0 × 103 cells/ml by using a smartphone with an image analyzer. We also establish the identification of different microbial cells by the characteristic Raman transitions directly measured from the interfacially trapped cells.

Original languageEnglish
Pages (from-to)7449-7456
Number of pages8
JournalNano Letters
Volume19
Issue number10
DOIs
StatePublished - 9 Oct 2019

Keywords

  • Surface hydrophobicity
  • in-plane optical detection
  • interfacial trapping
  • metal nanoparticles
  • microbial cells
  • preconcentration

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