A portable magnetofluidic platform for detecting sexually transmitted infections and antimicrobial susceptibility

Abstract

Effective treatment of sexually transmitted infections (STIs) is limited by diagnostics that cannot deliver results rapidly while the patient is still in the clinic. The gold standard methods for identification of STIs are nucleic acid amplification tests (NAATs), which are too expensive for widespread use and have lengthy turnaround times. To address the need for fast and affordable diagnostics, we have developed a portable, rapid, on-cartridge magnetofluidic purification and testing (PROMPT) polymerase chain reaction (PCR) test. We show that it can detect Neisseria gonorrhoeae, the pathogen causing gonorrhea, with simultaneous genotyping of the pathogen for resistance to the antimicrobial drug ciprofloxacin in <15 min. The duplex test was integrated into a low-cost thermoplastic cartridge with automated processing of penile swab samples from patients using magnetic beads. A compact instrument conducted DNA extraction, PCR, and analysis of results while relaying data to the user via a smartphone app. This platform was tested on penile swab samples from sexual health clinics in Baltimore, MD, USA (n = 66) and Kampala, Uganda (n = 151) with an overall sensitivity and specificity of 97.7% (95% CI, 94.7 to 100%) and 97.6% (95% CI, 94.1 to 100%), respectively, for N. gonorrhoeae detection and 100% concordance with culture results for ciprofloxacin resistance. This study paves the way for delivering accessible PCR diagnostics for rapidly detecting STIs at the point of care, helping to guide treatment decisions and combat the rise of antimicrobial resistant pathogens.

Magnetofluidic immuno-PCR for point-of-care COVID-19 serological testing

“…We next adapted the magnetic-based immuno-PCR assay for POC use by employing a palm-sized magnetofluidic device ( Shin et al, 2018 ; Trick et al, 2021 ), previously developed by our group, that utilizes a disposable thermoplastic cartridge to automate its sample processing and PCR detection. The magnetofluidic device relies on a pre-programmed biaxial manipulator to move magnetic beads from one well to another in the cartridge using two opposing permanent magnets that are attached to a servo motor assembly ( Supplementary Fig.…”

“…After the beads are washed to remove nonspecifically-adsorbed oligo-anti-IgG conjugate, they are then transferred to the PCR reaction well and PCR is initiated. To speed up PCR for POC testing, we improved the reaction kinetics with enhanced assay chemistry and accelerated the temperature ramping by optimizing heat block geometry ( Trick et al, 2021 ). As a result, we achieved a maximal thermal ramping rate of 10.4 °C/s and a maximal cooling rate of 18.5 °C/s between 60 to 100 °C.…”

“…, oligo-anti-IgG) binding, into a 15 min single-step, one-pot reaction. We then implement the streamlined assay into the palm-sized magnetofluidic device, which uses magnetic particles to transport bimolecular targets through discrete reagent droplets, enabling the integration of biomolecular assays without the need for complex fluidic cartridges and instrumentation ( Chen et al, 2019 ; Shin et al, 2018 , 2017 ; Trick et al, 2021 ; Zhang and Nguyen, 2017 ; Zhang and Wang, 2013 ). Our magnetofluidic device automates magnetic bead transfer across different wells in a USB drive-sized disposable cartridge, performs an ultrafast 15 min PCR using a miniature thermocycler and a fluorescence detector, and finally reports the testing results to a smartphone app via Bluetooth.…”

The impact of COVID-19 pandemic on technologic and process innovation in point-of-care diagnostics for sexually transmitted infections

“…Getting these patients traced and treated is time-consuming and expensive as is partner treatment. Furthermore, for NG, rapid information on antibiotic resistance mutations could allow tailored antibiotic regimens [22] . In a dynamic modeling study which included transmission among sexual partners, a hypothetical test with sensitivity ∼10% lower than currently available reference tests could still have substantial impact on chlamydia prevalence and pelvic inflammatory disease incidence if, over 60% of the screened individuals received immediate treatment, and baseline lost-to-follow up was 20% in the current care delivery model [23] .…”

Filtration-assisted magnetofluidic cartridge platform for HIV RNA detection from blood

“…We have previously demonstrated use of droplet magnetofluidics to enable automation of nucleic acid purification coupled to nucleic acid amplification directly from clinical samples in a point-of-care format. 19–24 In contrast to traditional microfluidic techniques that require precise fluidic controls and microchannel fabrication, magnetofluidics leverages transfer of magnetic beads through discrete droplets of reagents for fully integrated sample-to-answer bioassays using simple low-power actuation of permanent magnets. 25,26 Due to the simplicity of our cartridge construction, each cartridge can be fabricated for around $2 to provide an affordable alternative to currently available commercial products.…”