Capillary Array Waveguide Amplified Fluorescence Detector formHealth

摘要

Mobile Health (mHealth) analytical technologies are potentially useful for carrying out modern medical diagnostics in resource-poor settings. Effective mHealth devices for underserved populations need to be simple, low cost, and portable. Although cell phone cameras have been used for biodetection, their sensitivity is a limiting factor because currently it is too low to be effective for many mHealth applications, which depend on detection of weak fluorescent signals.To improve the sensitivity of portable phones, a capillary tube array was developed to amplify fluorescence signals using their waveguide properties. An array configured with 36 capillary tubes was demonstrated to have a ~100X increase in sensitivity, lowering the limit of detection (LOD) of mobile phones from 1000 nM to 10 nM for fluorescein. To confirm that the amplification was due to waveguide behavior, we coated the external surfaces of the capillaries with silver. The silver coating interfered with the waveguide behavior and diminished the fluorescence signal, thereby proving that the waveguide behavior was the main mechanism for enhancing optical sensitivity.The optical configuration described here is novel in several ways. First, the use of capillaries waveguide properties to improve detection of weak florescence signal is new. Second we describe here a three dimensionalillumination system, while conventional angular laser waveguide illumination isspot (or line), which is functionally one-dimensional illumination, canilluminate only a single capillary or a single column (when a line generator isused) of capillaries and thus inherently limits the multiplexing capability ofdetection. The planar illumination demonstrated in this work enablesillumination of a two dimensional capillary array (e.g. x columns and y rows ofcapillaries). In addition, the waveguide light propagation viathe capillary wall provides a third dimension for illumination along the axis ofthe capillaries. Such an array can potentially be used for sensitive analysis ofmultiple fluorescent detection assays simultaneously.The simple phone based capillary array approach presented in this paperis capable of amplifying weak fluorescent signals thereby improving thesensitivity of optical detectors based on mobile phones. This may allowsensitive biological assays to be measured with low sensitivity detectors andmay make mHealth practical for many diagnostics applications, especially inresource-poor and global health settings.