Investigations of paper-based lab-on-chips for on-diaper point-of-care screening of urinary tract infections
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UTIs are common infection diseases in the hospitals, especially in the elderly. Detecting UTIs in the elderly is a difficult and time-consuming procedure. Sampling and detection on a diaper could be the solution. Sampling from diapers has been investigated and experimented, and the results have shown that injecting salt water can release the urine absorbed by the diaper. Different biomarkers have been investigated, and two methods were attempted using the existing tools: a bioluminescence ATP-detection lab-on-chip and an electrochemical sensor for the diagnosis of UTIs after extracting urine from the diaper. Finally, based on the literature, bio-sensing paper-based lab-on-chip were used for UTI point-of-diagnosis. By using a combination of lateral flow and paper-based lab-on-chip, a urine sample can be conveniently collected and analysed directly on the diaper. For the bioluminescent lab-on-chip method, an existing novel multifunctional silicon lab-on-chip (LOC) was used to provide a highly efficient long-term continuous analysis platform for measuring the concentration of adenosine 5'-triphosphate (ATP) and thus detect the UTI based on bioluminescence. A new two-sided silicon lab-unchip (LOC) was also designed, and numerous investigations proved that combing it with segmented flow analysis (SFA), T-junction droplet generator, which is stable to transport the sample, and a micro mixer can achieve an outstanding mixing efficiency in a small space. The existing chip had been tested, and the materials were well prepared before testing the PMT detecting system. The data from PMT were visualized by the Labview™, and they showed good linearity between the voltage values and the ATP concentrations, which ranged from 2×10-12 M to 2×10-8 M. Fresh urine samples with different amounts of Escherichia coli were measured by the system and showed a good linearity trend between the voltage values and the number of E. coli. This study successfully expressed the concept of measuring ATP directly in the urine to quickly and accurately detect UTI on a microfluidic chip. An electrochemical nitrite sensor was assembled and calibrated, and the artificial urine sample was measured; the feasibility of the electrochemical nitrite sensor, including the error effect, was detected around -5.1~2.3%. The possibility of detecting artificial UTIs in urine samples is approximately 95.5%, and the approximate relationship between the number of E. coli and the electrode potential was Ε=228.3193-3.78225×L n (N+2.29101e6), thus building the relationship between UTI possibility and measurement. Finally, the electrochemical sensor array was conceived and designed to measure different biomarkers and thus obtain the maximum UTI possibility and to show the data for the UTI possibility directly on the screen. Furthermore, this array can easily be used and transported for home-users or patients in hospitals. the bio-sensing paper-based lab-on-chip method for determining UTIs with an on-diaper point-of-care diagnosis application combines the lateral flow and biochemistry reactions. Topics related with paper-based lab-on-chip microfludics and fabrication methods were investigated. The design to make channels on paper and tested were done by me. Another design for realising the reaction on one paper with reactions to form channels and barriers were designed by others but the wax-based fabrication method for this were investigated and finally fabricated by me. Continuous tests of this reaction layer of biosensor were performed in the bioMEMS lab, fold generated by wearing will not affect the result, the channels were formed ideally by hydrophilic wax and the results were kept for more than 24 hours, which covers the disadvantage of the commonly used urine strips. Additionally, it only took 2 min to read the results, which covers the disadvantage of both the gold method-urine culture and microscope. It proved to be a successful point-of-diagnostics biosensor for the diaper-based screening of urinary tract infections (UTIs) in elderly people.