A Capacitive Touch Screen Sensor for Detection of Urinary Tract Infections in Portable Biomedical Devices

Incidence of urinary tract infections (UTIs) is the second highest among all infections; thus, there is a high demand for bacteriuria detection. Escherichia coli are the main cause of UTIs, with microscopy methods and urine culture being the detection standard of these bacteria. However, the urine sampling and analysis required for these methods can be both time-consuming and complex. This work proposes a capacitive touch screen sensor (CTSS) concept as feasible alternative for a portable UTI detection device. Finite element method (FEM) simulations were conducted with a CTSS model. An exponential response of the model to increasing amounts of E. coli and liquid samples was observed. A measurable capacitance change due to E. coli presence and a tangible difference in the response given to urine and water samples were also detected. Preliminary experimental studies were also conducted on a commercial CTSS using liquid solutions with increasing amounts of dissolved ions. The CTSS was capable of distinguishing different volumes of liquids, also giving an exponential response. Furthermore, the CTSS gave higher responses to solutions with a superior amount of ions. Urine samples gave the top response among tested liquids. Thus, the CTSS showed the capability to differentiate solutions by their ionic content

Electrical Characterization and Detection of Blood Cells and Stones in Urine

Urine contains an immense amount of information related to its physical, chemical, and biological components; hence, it is a promising tool in detecting various diseases. Available methods for detecting hematuria (blood in the urine) are not accurate. Results are influenced by many factors, such as, health and vitals of the patients, settings of the equipment and laboratories, which leads to false positive or false negative outputs. This necessitates the development of new, accurate, and easy-access methods that save time and effort. This study demonstrates a label-free and accurate method for detecting the presence of red and white blood cells (RBCs and WBCs) in urine by measuring the changes in the dielectric properties of urine upon increasing concentrations of both cell types. The current method could detect changes in the electrical properties of fresh urine over a short time interval, making this method suitable for detecting changes that cannot be recognized by conventional methods. Correcting these changes enabled the detection of a minimum cell concentration of 10² RBCs per ml which is not possible by conventional methods used in the labs except for the semi-quantitative method that can detect 50 RBCs per ml, but it is a lengthy and involved procedure, not suitable for high volume labs. This ability to detect a very small amount of both types of cells makes the proposed technique an attractive tool for detecting hematuria, the presence of which is indicative of problems in the excretory system. Furthermore, urolithiasis is also a very common problem worldwide, affecting adults, kids, and even animals. Calcium oxalate is the major constituent of urinary tract stones in individuals, primarily due to the consumption of high oxalate foods. The occurrence of urinary oxalate occurs by endogenous synthesis, especially in the upper urinary tract. In a normal, healthy individual, the excretion of oxalate ranges from 10 to 45 mg/day, depending on the age and gender, but the risk of stone formation starts at 25 mg/day depending on the health history of the individual. This study also addresses the detection of the presence of calcium oxalate in urine following the same label-free approach. This can be done by measuring the changes in the dielectric properties of urine with increasing concentrations of calcium oxalate hydrate (CaC₂O₄.H₂O). The current method could detect dynamic changes in the electrical properties of urine over a time interval in samples containing calcium oxalate hydrate even at a concentration as low as 10 μg/mL of urine, making this method suitable for detecting changes that cannot be recognized by conventional methods. The ability to detect a very small amount of stones makes it an attractive tool for detecting and quantifying stones in kidneys. Using a non-invasive method which also works as a precautionary measure for early detection of some severe ailments, holds a good scope. It forms the basis of the cytological examinations and molecular assays for the diagnosis of several diseases. This method can be considered a point-of-care test because the results can be instantaneously shared with the members of the medical team. Based on these results, it is anticipated that the present approach to be a starting point towards establishing the foundation for label-free electrical-based identification and quantification of an unlimited number of nano-sized particles

Determination of antibiotic susceptibility of the bacteria causing urinary tract infections using a novel lab-on-a-chip design

Urinary tract infections (UTIs) are one of the most common types of bacterial infection in the UK, and also are expensive to treat costing the National Health Service ~£54 million between 2016 and 2017. Culture-based antibiotic susceptibility testing (AST) is used to identify an antibiotic to treat drug-resistant urinary tract infections and takes 48 hours to complete. Faster prescription of effective antibiotics should reduce the risk of sepsis and poor clinical outcomes. To address this need, we developed a Lab-on-a-Chip (LOC) based method to conduct electrochemical AST using screen-printed macroelectrodes (SPEs) and antibiotic-loaded hydrogels. SPEs were fabricated using carbon-graphite based inks, with resazurin bulk modified SPEs (R-SPEs) being fabricated through modification of the SPEs WE. Polyvinyl alcohol (PVA) based hydrogels were loaded with the following antibiotics were used; cephalexin, ceftriaxone, colistin, gentamicin, piperacillin, trimethoprim and vancomycin as well as an antibiotic-free control. LOC devices were then designed to encapsulate both the R-SPEs and the antibiotic hydrogels to enable multiplexed electrochemical AST to occur on a single device. In the initial testing of the R-SPEs and the antibiotic hydrogels independently of a LOC device, antibiotic susceptibility could be determined in 90 minutes for E. coli. After the preliminary work, eight chambered LOC devices were spiked with simulated UTI samples. Each chamber contained an R-SPE and an antibiotic hydrogel. After an incubation step, susceptibility of Escherichia coli and Klebsiella pneumoniae could be established in 85 minutes of testing which is significantly faster than the 48 hours required for conventional culture-based AST. The sensitive detection of resazurin afforded by using the electrochemical detection methodology incorporated onto a LOC device described here offers an inexpensive and simple method for the determination of antibiotic susceptibility that is faster than using a culture-based approach