Chenchen Liang's research while affiliated with Northeastern University (Shenyang, China) and other places

With increasing attention to personalized healthcare, miniaturized and easily implementable devices are desired for point-of-care testing (POCT). Herein, hydrophilic patterns were designed on freestanding TiO2 nanotube arrays (TiNTs) as nanoreactors for a naked-eye colorimetric assay. With a high aspect ratio, TiNTs can provide a long observation length combined with a limited volume. Moreover, by combining the photocatalytic property of TiO2 and spatiotemporal controllability of light, hydrophilic nanoreactors were fabricated with minimal volume, and thus the indicator and analyte are limited in a confined void by the hydrophobic surroundings, thus allowing a higher sensitivity for sensing. We believe the proposed sensing platform could provide a promising strategy in developing POCT devices for routine health monitoring.

Taking advantage of the intrinsic photocatalysis of TiO2, hydrophilic reactor arrays were lithographically patterned on a hydrophobic paper via a simple UV irradiation. As a proof-of-concept, alkaline phosphatase (ALP) was used as the model analyte for colorimetric analysis. As ALP can induce hydrolysis of pyrophosphate-Zn(II) framework, the released Zn2+ ions are subsequently coordinated with red-colored zincon to form blue-colored zincon-Zn(II) chelate complex, and these color differences were applied for further colorimetric assay. The sensing platform showed response to ALP ranging from 20 ~ 800 U L−1 with a detection limit of 3 U L−1, and the recoveries of ALP in serum samples were in the range 95.7 ~ 104.5% with relative standard deviations from 2.10 to 3.84%. Additionally, the distinct wettability features of the proposed sensing platform effectively prevent lateral fluid spread out of hydrophilic reactors, thus allowing not only the use of minimum amount of analyte but it has also a high potential for simultaneous quantification of multiple samples.