Nanoplasmonics Enables Label-Free Measurement of Bacteria Formation

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Using nanochip technology and a targeted beam of light, scientists have devised a real-time, label-free way to monitor biofilms, an important component in the search for alternatives to bacteria-resistant antibiotics.

The team from the Okinawa Institute of Science and Technology (OIST) wanted to gain a better understanding of the biochemical reactions that allow bacteria to produce biofilms, which are slimy linked matrix structures. Finding no tools available that would allow them to monitor biofilm growth according to their requirements, the researchers modified an existing tool.

Nanomushroom chip created for testing biofilms. OIST.
The nanomushroom chip used to grow bacterial colonies for testing. Courtesy of OIST and CC 2.0.

“We created little chips with tiny structures for E. coli to grow on,” said researcher Nikhil Bhalla. "They are covered in mushroom-shaped nanostructures with a stem of silicon dioxide and a cap of gold."

When the researchers exposed the nanomushrooms to a beam of light, the nanostructures absorbed light through a localized surface plasmon resonance (LSPR) sensor. The sensor was able to capture the signatures of biofilm formation in real time by measuring the wavelength shift in the LSPR resonance peak with high temporal resolution. The researchers could observe the E. coli growing around the mushroom structures without damaging the sample.
A nanomushroom chip undergoing testing with an LSPR device. OIST.
A nanomushroom chip undergoing testing with an localized surface plasmon resonance (LSPR) device. Courtesy of OIST and CC 2.0.

The researchers used the LSPR sensor to investigate how biofilm formation is affected by different drugs, including conventional antibiotics. To enable a constant stream of data from the LSPR-based tool, the researchers developed a program to automate the data analysis and processing so they could monitor biofilm growth in real time.

The team believes that its benchtop tool could be used on a variety of clinically relevant bacteria for biofilm characterization and drug screening. It plans to miniaturize the technology to create a portable device that could be used in a range of biosensing applications.

(From left to right) researchers Kang-Yu Chu, Riccardo Funari, and Nikhil Bhalla brought together their diverse skills to tackle biofilms. Courtesy of OIST.
From left: Researchers Kang-Yu Chu, Riccardo Funari, and Nikhil Bhalla brought together their diverse skills to tackle biofilms. Courtesy of OIST.
According to researcher Riccardo Funari, “This could be a great tool for testing future drugs on lots of different kinds of bacteria." 

The research was published in ACS Sensors (doi: 10.1021/acssensors.8b00287).

Published: August 2018
Plasmonics is a field of science and technology that focuses on the interaction between electromagnetic radiation and free electrons in a metal or semiconductor at the nanoscale. Specifically, plasmonics deals with the collective oscillations of these free electrons, known as surface plasmons, which can confine and manipulate light on the nanometer scale. Surface plasmons are formed when incident photons couple with the conduction electrons at the interface between a metal or semiconductor...
An SI prefix meaning one billionth (10-9). Nano can also be used to indicate the study of atoms, molecules and other structures and particles on the nanometer scale. Nano-optics (also referred to as nanophotonics), for example, is the study of how light and light-matter interactions behave on the nanometer scale. See nanophotonics.
Research & TechnologyeducationOpticsplasmonicsnanonanoplasmonicsSensors & DetectorsBiophotonicsmedicalpharmaceuticalantiobiotic resistancebacteria-resistantbiofilmOISTOkinawa Institute of Science and TechnologyLSPRlocalized surface plasmon resonanceBioScan

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