| Recently, Microfluidic paper-based analytical devices (?PADs) have witnessed growing interest in many different areas, such as life sciences, environmental analysis, or health-care. The methods based on ?PADs are different from the conventional analytical methods, and they often do not require expensive automated equipment and skilled workers, on the contrary, they are mostly based on cellulose paper substrate, which make ?PADs possess many attractive advantages, such as low-cost, disposable and simple to use. It is believed that ?PADs is one of the cheapest platforms whose basis lies on the creation of hydrophilic microchannels on cellulose by means of different hydrophobic patterning materials. Cellulose paper is compatible with biological samples, so ?PADs can provide a platform with many new capabilities for bioanalysis. Although ?PADs have many new and useful applications, it is still a new field in analytical chemistry and there are many opportunities to expand their capabilities. These include how to develop new simple methods for volume fabricating of ?PADs, the development of methods for stabilizing reagents stored in ?PADs, and the development of new technologies for measuring the results of paper-based assays.Thus, in this paper we developed a new fabricating ?PADs method and researched two new applications of it.The specific works are summarized as follows:(1) The ink-jet printing technology is utilized here to fabricate a high precision ?PADs. Creating microfluidic patterns and channels by generating a hydrophilic-hydrophobic contrast on the paper surface is crucial to a ?PADs, we first investigate hydrophobization effect on paper of three hydrophobic materials and we choose a highly hydrophobic material polymethyl hydrogen siloxane (PMHS) as jet ink, and n-butyl alcohol adjust the viscosity and surface tension to achieve the required ink properties. The printing process need only a few seconds and after some gentle treatment we can obtain a good reproducibility of hydrophobic patterns, it make the method a promising means for volume fabricating ?PADs.(2) In this work we show that quantum dots (QDs) can be used to develop a fluorescent test paper for quantitative analysis method of trypsin. We solved three problems in the processes of fabrication of flurescent test paper and its application for trypsin testing. First, we investigate how can we immobilize QDs in the cellulose paper, and we choose positive charged silicon balls binding QDs to prevent QDs diffusion on the paper. Second,we utilize 3D printing technology to fabricate a incubator for trypsin digestion under 37? condition. Third, a smartphone is used here to take the flurescent pictures of the test papers, followed by imageJ software processing the pictures, and we obtain a good linear response. In addition, the assay we developed can detect different proteases via change substrate peptide. Thus, we developed a protable, universal and point of care suitable protease detection method.(3) We developed two visual colorimetric assays for detecting glucose and protein in urine sample on the paper. For the glucose assay, we use glucose oxidase (GOX) to catalyze the oxidation of ?-D-glucose and generates an equivalent amount of H2O2, then ABTS is catalyzed by HRP into the radical-cation (ABTS·+) in the presence of H2O2, appearing a green color. For the protein assay, we utilize ionized TBPB binds to protein on the paper, and the result will be indicated by a color change from yellow to blue. We use smart phone take the paper color result as pictures and process pictures using imageJ software to carry out linear regression for glucose and protein. Finally, we analyze the glucose and protein in the urine samples to verify the method can be used to real sample test. |
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