Multimode smartphone biosensing: the transmission, reflection, and intensity spectral (TRI)-analyzer

Abstract

We demonstrate a smartphone-integrated handheld detection instrument capable of utilizing the internal rear-facing camera as a high-resolution spectrometer for measuring the colorimetric absorption spectrum, fluorescence emission spectrum, and resonant reflection spectrum from a microfluidic cartridge inserted into the measurement light path. Under user selection, the instrument gathers light from either the white “flash” LED of the smartphone or an integrated green laser diode to direct illumination into a liquid test sample or onto a photonic crystal biosensor. Light emerging from each type of assay is gathered via optical fiber and passed through a diffraction grating placed directly over the smartphone camera to generate spectra from the assay when an image is collected. Each sensing modality is associated with a unique configuration of a microfluidic “stick” containing a linear array of liquid chambers that are swiped through the instrument while the smartphone captures videoand the software automatically selects spectra representative of each compartment. The system is demonstrated for representative assays in the field of point-of-care (POC) maternal and infant health: an ELISA assay for the fetal fibronectin protein used as an indicator for pre-term birth and a fluorescent assay for phenylalanine as an indicator for phenylketonuria. In each case, the TRI-Analyzer is capable of achieving limits of detection that are comparable to those obtained for the same assay measured with a conventional laboratory microplate reader, demonstrating the flexibility of the system to serve as a platform for rapid, simple translation of existing commercially available biosensing assays to a POC setting.

Point-of-use detection of ascorbic acid using a spectrometric smartphone-based system

“…The optical design, fabrication and main features of a recently-developed smartphoneintegrated handheld detection instrument have been previously introduced (Long et al 2017;Scherr et al 2017). Fig.…”

“…The results obtained clearly demonstrate that the spectrometric smartphone-based system has an enormous potential for commercial applications. The analytical instrument used provides important advantages such as portability, fast, reliable AA quantification, and a platform that can be readily adapted to a number of analytes, some of which have already been demonstrated (Gallegos et al 2013;Long, et al 2014;Long, et al 2017;Yu et al 2014).…”

Analysis of Paper-Based Colorimetric Assays With a Smartphone Spectrometer

“…ASSAYS that generate a colored liquid or a fluorescence-generating liquid represent broad classes of tests that are used in many applications that include health and wellness diagnostics [1], water and food safety monitoring [2], manufacturing quality control [3], forensic analysis, and product authenticity verification [4]. For these applications, the ability to measure the visible-wavelength absorption/emission spectrum not only enables the system to be applicable to a broad range of chromophores and fluorophores, but also facilitates the quantification of subtle changes in color that are not possible to differentiate by analyzing small set of wavelengths (such as with a few color filters, or through analysis of the redgreen-blue pixel intensities of a conventional image).…”

“…Recently, we demonstrated a compact "cradle" for an ordinary smartphone that enabled its rear-facing camera to be utilized as a spectrophotometer for measuring the absorption spectra of bio-assay liquids [2], the fluorescence emission spectra from tagged nucleic acids [30], and the resonant reflection spectra from label-free photonic crystal biosensors. The Transmission-Reflection-Intensity (TRI)-Analyzer is capable of utilizing the rear-facing flash LED to channel broadband "white" light to a test sample through an optical fiber, and to gather light from a test sample into a separate optical fiber that directs light through a diffraction grating placed directly in front of the camera lens [1]. The cradle, comprised of a plastic housing that places inexpensive passive optical components into alignment with the LED and camera of a mobile phone, was demonstrated to perform an equivalent function to laboratory-based spectrophotometers in terms of detection limit and dynamic range for several representative assays [1].…”

“…The Transmission-Reflection-Intensity (TRI)-Analyzer is capable of utilizing the rear-facing flash LED to channel broadband "white" light to a test sample through an optical fiber, and to gather light from a test sample into a separate optical fiber that directs light through a diffraction grating placed directly in front of the camera lens [1]. The cradle, comprised of a plastic housing that places inexpensive passive optical components into alignment with the LED and camera of a mobile phone, was demonstrated to perform an equivalent function to laboratory-based spectrophotometers in terms of detection limit and dynamic range for several representative assays [1]. Although the read head of the instrument illuminates only a single point, we also demonstrated that a cartridge comprised of a linear series of liquid compartments could be measured rapidly in series by scanning the cartridge through the instrument while the phone's camera records video, using an image processing algorithm to automate selection of video frames that represent spectra from the center of each compartment.…”