A team of researchers affiliated with multiple institutions in Korea and two in India has developed a fidget-spinner-like device that is able to detect UTIs in urine samples.
In their paper published in the journal Nature Biomedical Engineering, the group describes how the device works and ways that it might be useful.
Urinary tract infections (UTIs) are a very common condition around the globe. They are much more often found in women and lead to millions of dollars in healthcare costs in addition to the pain and discomfort suffered by those afflicted.
UTIs are also very common in pregnant women and can lead to a wide variety of problems for both the mother and baby.
Currently, UTIs are diagnosed by doctors assessing patient-reported symptoms followed by pathogen detection in labs from submitted patient samples – a process that can take many hours or even days, depending on lab conditions.
Because of such delays in detection, doctors very often prescribe antibiotics before a confirmation from a lab. This is a problem because over-prescription can lead to bacterial resistance.
In this new effort, the researchers have created a device that can be used to diagnose UTIs in just 45 minutes – and it can be done at home without assistance from medical professionals.
The device looks very much like a commercial fidget spinner. Urine samples are placed inside of it and the device spins using hand action. The spinning motion forces the urine though a thin membrane, leaving any bacteria behind on the inside.
If bacteria accumulate on the membrane, it will interact with a dye, revealing its presence. The process involves two spins of the device over the course of 45 minutes. The person performing the test can receive their diagnosis directly from the device by noting if the dye has been activated.
The researchers note that because it is fast, simple and easy to use, and requires no electricity, it could be deployed in developed countries as well as remote sites with limited access to health care.
Fidget spinners are boomerang-shaped toys whose ball bearings reduce friction and allow things to rotate freely for a long time (Figure 1A). One flick of the fidget with a finger sets the gadget in motion.
By exploiting the centrifugal force derived from the design of a fidget spinner and their novel mechanism called, a fluid assisted separation technology (FAST), the research team optimized the fluidic dynamics in Dx-FS.
This mechanism enables the Dx-FS to work just with one or two spins by hand and to produce 100 times more enriched pathogens that can be easily seen by naked-eyes without the need of bacteria culture (Figure 1B).
Conventional approach for the diagnostics of the infectious disease require time-consuming cell culture as well as modern laboratory facilities. Worse yet, typical bacterial cell enrichment requires huge force and it is prone to membrane fouling or clogging due to the pressure imbalance in the filtration chamber.
“Though the centrifugal force serves as an “engine” of the device, the force is felt more strongly in the outer path as it acts outwardly away from the center of rotation.
The imbalanced impact of the centrifugal force keeps some of the sample left in the membrane. We utilized hydrodynamic forces that acts vertically to the centrifugal force by filling the filter membrane with liquid before the spinning process.
This minimized the pressure drop and brought the uniform pressure balance throughout the entire area of the membrane.
This allowed for maximized bacterial cell enrichment efficiency while minimizing the force needed for the filtration. Therefore, one or two spins were enough to filter 1 mL of sample despite large variation in the spin speed among different operators with different hand power (Figure 1C).” explains professor CHO Yoon-Kyoung, the corresponding author of the study.
In FAST-based particle separation, the fluid flow caused by centrifugal force is in a direction perpendicular to the filtration flow through the membrane. In addition, the drainage chamber underneath the membrane remains fully filled with the liquid during the entire filtration process.
This is achieved by placing a buffer solution in the bottom chamber of the membrane prior to the spinning process, which ensures uniform filtration across the entire area of the membrane and significantly reduces the hydrodynamic resistance.
The research team verified Dx-FS can perform “sample-in-answer-out” analyses.
The research team tested urine samples from 39 UTI suspects in Tiruchirappalli, India. Compared to the gold-standard culture method, which has a relatively long turnaround time, Dx-FS provided a comparable answer on site in 50 minutes.
The experiment shows 59% of UTI suspects were over/under-treated for antibiotics, which may be saved by using Dx-FS (Figure 2).
Further, they performed a rapid antimicrobial susceptibility test (AST) for two antimicrobial drugs on 30 UTI patients using Dx-FS. The test produced 100% accurate results within 120 minutes (Figure 3).
Overall, this simple, hand-powered, portable device allows rapid enrichment of pathogens from human urine samples, showing high potential for future low-cost POCT diagnostic applications. A simple tool like Dx-FS provides UTI management and prevention of resistance in low resource settings.
More information: Issac Michael et al. A fidget spinner for the point-of-care diagnosis of urinary tract infection, Nature Biomedical Engineering (2020). DOI: 10.1038/s41551-020-0557-2