Abstract
Point-of-care systems enable fast therapy decisions on site without the need of any healthcare infrastructure. In addition to the sensitive detection, stable measurement by inexperienced persons outside of laboratory facilities is indispensable. A particular challenge in field applications is to reduce interference from environmental factors, such as temperature, to acceptable levels without sacrificing simplicity. Here, we present a smartphone-based point-of-care sensor. The method uses an optofluidic grating composed of alternating detection and reference channels arranged as a reflective phase grating. Biomolecules adsorbing to the detection channel alter the optical path length, while the parallel reference channels enable a direct common mode rejection within a single measurement. The optical setup is integrated in a compact design of a mobile readout device and the usability is ensured by a smartphone application. Our results show that different ambient temperatures do not have any influence on the signal. In a proof-of concept experiment we measured the accumulation of specific molecules in functionalized detection channels in real-time and without the need of any labeling. Therefore, the channel walls have been modified with biotin as capture molecules and the specific binding of streptavidin was detected. A mobile, reliable and robust point-of-care device has been realized by combining an inherently differential measurement concept with a smartphone-based, mobile readout device.
Highlights
In many areas of the world, diseases that are treatable from a medical point of view remain a major problem due to a lack of medical infrastructure [1]
Our results show that refractive index changes can be measured with a sensitivity of 10−5 RIU and that the accumulation of biomolecules on the channel wall can be measured in real-time [14]
We show that a change in refractive index can be measured sensitively by the mobile platform
Summary
In many areas of the world, diseases that are treatable from a medical point of view remain a major problem due to a lack of medical infrastructure [1]. Our results show that refractive index changes can be measured with a sensitivity of 10−5 RIU and that the accumulation of biomolecules on the channel wall can be measured in real-time [14]. This makes the asymmetric nanofluidic detector a very promising technology for the implementation in POC. For the transfer of optical biosensing technologies from the laboratory scale to a mobile POC device, smartphones including digital cameras are a versatile tool to realize cheap and compact mobile platforms. The optical measurement setup was transferred to a portable system, where the acquisition as well as the evaluation of diffraction images is realized with the help of a smartphone. Surface functionalization of the nanochannels in the optical grating is used to detect the accumulation of specific molecules in a label-free manner
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