The MRD disk: automated minimal residual disease monitoring by highly sensitive centrifugal microfluidic multiplex qPCR

A capillary-driven microfluidic device for performing spatial multiplex PCR

Multiplex polymerase chain reaction (PCR) tests multiple biomarkers or pathogens that cause overlapping symptoms, making it an essential tool in syndromic testing. To achieve a multiplex PCR on chip, a design based on capillary-driven fluidic actuation is proposed. Our silicon chip features 22 reaction chambers and allows primers and probes to be pre-spotted in the reaction chambers prior to use. The design facilitates rapid sample loading through a common inlet channel, delivering reagents to all reaction chambers in less than 10 s. A custom clamping mechanism combined with a double depth cavity design ensures proper sealing during temperature cycling without the need for extra reagents like oil. Temperature cycling and fluorescence imaging were performed using custom-made hardware. As a proof of concept, two single nucleotide polymorphisms (SNPs), CyP2C19*2 and PCSK9 were detected. These results demonstrate the feasibility of on-chip multiplex PCR, compatible with different assays in parallel and requiring only a single pipetting step for reagent loading, without active fluidic actuation like pumping.

Automatic microdispenser-integrated multiplex enzyme-linked immunosorbent assay device with autonomously driven centrifugal microfluidic system

In this study, we established the control and design theory of an autonomously driven dispenser at a steady rotation speed and proposed a dispenser-integrated multiplex enzyme-linked immunosorbent assay (ELISA) device. In establishing the theory of the dispenser, we estimated the flow rate in the dispenser and the applied pressure onto the passive valves, so that the suitable burst pressure of the valves and flow rate could be designed. The dispenser-integrated multiplex ELISA device has the potential to perform flow control for executing an ELISA of 6 samples/standards per chip or 18 samples/standards per compact disk by just steadily rotating a chip. In the immunoassay evaluation of the device using mouse IgG detection, it was confirmed that the device could assay 5 μL of several standards in just 30 min without nonspecific reactions, and although this system has a high limit of detection (LOD, 63.4-164 pg mL-1) it is equal to that of manual assay with a titer plate. The device can be fabricated by transferring the microchannel pattern from a mold without complex assembly or alignment, and it can control the liquid operation by just steadily rotating. Thus, the device system developed will contribute to reducing the cost of fabricating chips and control equipment for ELISA systems. Consequently, a compact, portable, and low-cost ELISA system for point-of-care testing is expected to be realized.

Advanced Minimal Residual Disease Monitoring for Acute Lymphoblastic Leukemia with Multiplex Mediator Probe PCR

Acute lymphoblastic leukemia (ALL) is the most frequent malignancy in childhood. Minimal residual disease (MRD) monitoring is an important prognostic factor for treatment response and patient stratification. It uses personalized real-time PCR to measure the amount of cancer cells among normal cells. Due to clonal tumor evolution or secondary rearrangement processes, MRD markers can disappear during treatment, leading to false-negative MRD results and wrong decision-making in personalized treatments. Therefore, monitoring of multiple MRD markers per patient is required. For the first time, the authors present personalized multiplex mediator probe PCR (MP PCR) for MRD monitoring in ALL. These assays can precisely quantify more MRD markers in less sample material. Therefore, clinical outcomes will be less affected by clonal tumor evolution. Personalized duplex MP PCR assays were developed for different genomic MRD markers, including immunoglobulin/T-cell receptor gene rearrangements, gene fusions, and gene deletions. One duplex assay was successfully applied in a prospective patient case and compared with hydrolysis probes. Moreover, the authors increased the multiplex level from duplex to 4-plex and still met the EuroMRD requirements for reliable quantification. In addition, the authors' MRD-MP design guidelines and multiplex workflow facilitate and accelerate MP PCR assay development. This helps the standardization of personal diagnostics.