(K-414) Rod-shaped magnetic particle-based multipurpose immunoassay system for rapid and accurate point-of-care tests: VEUS

In medical fields, especially in hospital emergencies, point-of-care tests (POCTs) combined with the capability of precision diagnostics are in escalating demand to initiate timely medical interventions. Challenges of existing POCTs remain the concurrent achievement of high sensitivity, accuracy, multiplex capability, and rapidity; meanwhile, precision diagnostics lead to at least a day of turnaround time and require skilled operators and costly and bulky equipment. Here we present a versatile, easy, user-friendly system (VEUS) overcoming such challenges by integrating four prominent features: 1) length-encoded rod-shaped magnetic particles (RSMPs), 2) complete automation throughout assay workflow, 3) circumferentially focusing illumination with 1× imaging, and 4) high-throughput artificial intelligence (AI)-based decoding and image processing. These implementations rendered 10 times higher optical sensitivity than conventional microscopy and reduced sample-in-to-readout time within 50 min. We chose traumatic brain injury (TBI) to verify clinical applicability, and the detection limits of GFAP and UCH-L1 were below 1 pg/mL. By quantification with 50 μL serum for each of the 30 subjects, we affirmed accurately equivalent diagnostic power to the conventional clinical diagnostics: CT scanning.

To quantify GFAP and UCH-L1 concentrations, the VEUPLEX™ TBI assay kit was used. The kit contained six sealed 8-well cartridges, each pre-filled with the necessary materials and reagents. In well 1, RSMPs(Rod-shaped magnetic particles) with capture antibodies were suspended in MES buffer. Well 2 contained a reaction buffer for binding target biomarkers on RSMPs. Wells 3, 6, and 7 contained a wash buffer, while well 4 held biotinylated detection antibodies. Well 5 had a staining buffer for the reporting fluorophore, SA-PE, and well 8 was for imaging.

The procedure involved:

1. Loading the cartridges into a holder.


2. Spiking clinical serum samples or diluted standards in well 2.


3. Automated processing by the VEUS using the M-bar's and T-tip's movements.


4. RSMPs were magnetically attached to the T-tip in well 1.


5. RSMPs were transferred to well 2 for immunoreactions.


6. RSMPs were moved to well 3 for washing.


7. RSMPs were transferred to well 4 for detection antibody binding.


8. RSMPs were moved to well 6 for another wash.


9. RSMPs were transferred to well 5 for SA-PE binding.


10. RSMPs were moved to well 7 for additional washes.


11. RSMPs were transferred to well 8 for imaging.


12. The VEUS acquired and analyzed bright-field and fluorescence images.

During steps 5 to 10, the M-bar magnetized and demagnetized the RSMPs to ensure proper mixing.

In conclusion, the development of a versatile and user-friendly point-of-care testing (POCT) system with high accuracy is crucial in the medical field. The VEUS, our advanced diagnostic instrument, addresses the challenges faced by existing technologies by integrating four key features: length-encoded RSMPs, complete automation of handling, circumferentially focusing illuminating module, and AI-based decoding and image processing. These implementations have significantly reduced the time for clinical sample-in-to-resultant readouts without the need for a well-trained operator. The VEUS optical module demonstrates superior sensitivity, optical uniformity, and minimal photobleaching compared to conventional microscopy.

Our experiments with multiplex immunoassays for traumatic brain injury (TBI) diagnostics using the VEUS showed that the limit of detection (LoD) for the astrocytic marker GFAP and neuronal marker UCH-L1 was below 1 pg/mL, two orders of magnitude lower than the TBI-positive cut-off values. Additionally, the VEUS exhibited a four-fold higher analytical sensitivity than traditional immunoassays such as ELISA. By quantifying the concentration of these TBI markers in the blood of 30 subjects, we confirmed that the VEUS provided accurate diagnostic power comparable to conventional CT imaging.

The VEUS holds immense potential in the rapid and accurate diagnostics of TBI and other diseases requiring timely interventions, including heart disease, cancer, sepsis, pandemic viral infections (e.g., COVID-19), cytokines, growth factors, and hormones. Furthermore, the four key features of the VEUS make it a versatile platform for molecular diagnostics beyond immunoassays, enabling the detection of RNAs and other molecular targets. As a result, we envision that the VEUS will pave the way for rapid and accurate diagnoses suitable for emergency departments or small hospitals, revolutionizing point-of-care testing.

We acknowledge support from the Korea Medical Device Development Fund grant funded by the Korean government (the Ministry of Science and ICT, the Ministry of Trade, Industry, and Energy, the Ministry of Health & Welfare, the Ministry of Food and Drug Safety) (Project Number: KMDF_PR_20210525_0002, RS-2021-KD000002).