Miaosi Li

“Periodic-Table-Style” Paper Device for Monitoring Heavy Metals in Water

If a paper-based analytical device (μ-PAD) could be made by printing indicators for detection of heavy metals in chemical symbols of the metals in a style of the periodic table of elements, it could be possible for such μ-PAD to report the presence and the safety level of heavy metal ions in water simultaneously and by text message. This device would be able to provide easy solutions to field-based monitoring of heavy metals in industrial wastewater discharges and in irrigating and drinking water. Text-reporting could promptly inform even nonprofessional users of the water quality. This work presents a proof of concept study of this idea. Cu(II), Ni(II), and Cr(VI) were chosen to demonstrate the feasibility, specificity, and reliability of paper-based text-reporting devices for monitoring heavy metals in water.

Barcode-like paper sensor for smartphone diagnostics: An application of blood typing

This study introduced a barcode-like design into a paper-based blood typing device by integrating with smartphone-based technology. The concept of presenting a paper-based blood typing assay in a barcode-like pattern significantly enhanced the adaptability of the assay to the smartphone technology. The fabrication of this device involved the use of a printing technique to define hydrophilic bar channels which were, respectively, treated with Anti-A, -B, and -D antibodies. These channels were then used to perform blood typing assays by introducing a blood sample. Blood type can be visually identified from eluting lengths in bar channels. A smartphone-based analytical application was designed to read the bar channels, analogous to scanning a barcode, interpret this information, and then report results to users. The proposed paper-based blood typing device is rapidly read by smartphones and easy for the user to operate. We envisage that the adaptation of paper-based devices to the widely accepted smartphone technology will increase the capability of paper-based diagnostics with rapid assay result interpretation, data storage, and transmission.

Paper-based device for rapid typing of secondary human blood groups

We report the use of bioactive paper for typing of secondary human blood groups. Our recent work on using bioactive paper for human blood typing has led to the discovery of a new method for identifying haemagglutination of red blood cells. The primary human blood groups, i.e., ABO and RhD groups, have been successfully typed with this method. Clinically, however, many secondary blood groups can also cause fatal blood transfusion accidents, despite the fact that the haemagglutination reactions of secondary blood groups are generally weaker than those of the primary blood groups. We describe the design of a user-friendly sensor for rapid typing of secondary blood groups using bioactive paper. We also present mechanistic insights into interactions between secondary blood group antibodies and red blood cells obtained using confocal microscopy. Haemagglutination patterns under different conditions are revealed for optimization of the assay conditions.

The detection of blood group phenotypes using paper diagnostics

Paper biodiagnostics for blood typing are novel, cheap, fast and easy to use. Agglutinated red blood cells cannot travel through the porous structure of paper, indicating a positive antibody–antigen interaction has occurred. Conversely, non‐agglutinated blood can disperse and wick through the paper structure with the ease to indicate a negative result. This principle has been demonstrated to detect blood group phenotypes: ABO and RhD. However, typing for red blood cell antigens such as Rh, Kell, Duffy and Kidd has not yet been explored on paper.

Superhydrophobic surface supported bioassay--an application in blood typing.

This study presents a new application of superhydrophobic surfaces in conducting biological assays for human blood typing using a liquid drop micro reactor. The superhydrophobic substrate was fabricated by a simple printing technique with Teflon powder. The non-wetting and weak hysteresis characteristics of superhydrophobic surfaces enable the blood and antibody droplets to have a near-spherical shape, making it easy for the haemagglutination reaction inside the droplet to be photographed or recorded by a digital camera and then analyzed by image analysis software. This novel blood typing method requires only a small amount of blood sample. The evaluation of assay results using image analysis techniques offers potential to develop high throughput operations of rapid blood typing assays for pathological laboratories. With the capability of identifying detailed red blood cell agglutination patterns and intensities, this method is also useful for confirming blood samples that have weak red blood cell antigens.

A low-cost forward and reverse blood typing device—a blood sample is all you need to perform an assay

For all user-operated blood typing devices in todays market, including those designed by us in our previous research, a buffer-activation or buffer-washing step is required. The buffer-activation step, as is employed in some commercial blood typing devices, involves dissolving the antibodies deposited in the assaying zones of the device before the introduction of a blood sample for an assay. The buffer-washing step involves washing the blood sample in the assay zone in the end of the assay for result reporting. While all these devices work well, the activation or washing step does reduce the adaptability of those devices to resource-poor areas and under emergent circumstances. In this study, we designed a new device to perform forward and reverse blood typing assays without the buffer-activation or buffer-washing. Low-cost plastic slides were patterned to form channels containing dried grouping antibodies. Blood typing assays can be performed by simply placing a few microlitres of a blood sample into the channels and then tilting the slide. The sample flows along the channel under gravity, dissolving dried antibody and then spreading into a film, unveiling the reaction of red blood cells (RBCs) and antibodies. This device enables easy visual identification of the agglutinated and non-agglutinated RBCs in typically 1 minute. Both forward and reverse blood typing assays can be performed using this device. To optimize the device design, the antibody dissolution profile, assay sensitivity, and device longevity were investigated in this work.