Plasmonics enhances the sensitivity of smartphone microscopy

Press Release (ePRNews.com) - Los Angeles, CA - May 22, 2017 - An international team of researchers from the University of California, Los Angeles (UCLA, USA) and the Braunschweig University of Technology (Germany) has developed an approach to enhance the sensitivity of smartphone based fluorescence microscopes by ten-fold compared to previously reported mobile phone based handheld microscopes. This is an important development toward the use of mobile phones for advanced microscopic investigation of samples, sensing of disease biomarkers, tracking of chronic conditions, and molecular diagnostics and testing in general.

Fluorescence is one of the predominant detection modalities for molecular diagnostic tools and medical tests due to the sensitivity and specificity that it enables. An important need in smartphone-based microscopy and sensing techniques is to improve the detection sensitivity to enable quantification of extremely low concentrations of target molecules, for example cancer biomarkers, pathogen proteins or even DNA. Therefore, these recent results on enhanced fluorescence microscopy using mobile phones are especially important to provide highly sensitive, mobile and cost-effective readers for molecular diagnostic tests, potentially impacting global health and point of care applications.

The sensitivity enhancement was accomplished by using a thin silver film on which the fluorescent samples were placed. Although the thickness of the silver film is approximately two thousand fold thinner than the human hair, it is sufficient to enhance the strength of the excitation light, especially in the vicinity of the fluorescent samples. This is achieved by coupling the energy of an optical beam into plasmonic waves (known as surface plasmon polaritons) that are formed by electron oscillations in the silver film. This plasmonics based optical enhancement resulted in a cost-effective mobile phone fluorescence microscope that weighs approximately 370 grams including the smartphone, and achieved repeatable detection of single quantum-dots and as few as ~50-80 fluorophores per sample spot. Compared to standard benchtop fluorescence microscopes, this mobile device is more than twenty fold cheaper and lighter.

“We are now capable of detecting a few tens of fluorophores for each sample spot using a low-cost pocket microscope, enabled by plasmonics and mobile phones. This will create numerous new opportunities for bringing advanced molecular testing and diagnostics for tackling global health problems, especially in developing countries,” said Aydogan Ozcan, who led the research team at UCLA and is a Chancellor’s Professor of Electrical Engineering and Bioengineering and an associate director of the California NanoSystems Institute (CNSI).

The first author of the research is Dr. Qingshan Wei, a former postdoctoral scholar at Ozcan Lab, who has recently moved to North Carolina State University (USA) as an Assistant Professor at the Department of Chemical and Biomolecular Engineering.

This collaboration between UCLA (Ozcan Lab) and Braunschweig University of Technology (Tinnefeld Lab) was published in Scientific Reports. Earlier this year, Ozcan Lab also reported targeted DNA sequencing and mutation analysis using a mobile phone based multimodal microscope, which was published in Nature Communications.

Ozcan Lab was supported by the National Science Foundation, Office of Naval Research, Army Research Office, National Institutes of Health, Vodafone Americas Foundation and Howard Hughes Medical Institute (HHMI).

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