Centrifugal disc liquid reciprocation flow considerations for antibody binding to COVID antigen array during microfluidic integration.

Heterogeneous immunoassays (HI) are an invaluable tool for biomarker detection and remain an ideal candidate for microfluidic point-of-care diagnostics. However, automating and controlling sustained fluid flow from benchtop to microfluidics for the HI reaction during the extended sample incubation step, remains difficult to implement; this leads to challenges for assay integration and assay result interpretation. To address these issues, we investigated the liquid reciprocation process on a microfluidic centrifugal disc (CD) to generate continuous, bidirectional fluid flow using only a rotating motor. Large volumetric flow rates (µL s-1) through the HI reaction chamber were sustained for extended durations (up to 1 h). The CD liquid reciprocation operating behavior was characterized experimentally and simulated to determine fluid flow shear rates through our HI reaction chamber. We demonstrated the continuous CD liquid reciprocation for target molecule incubation for a microarray HI and that higher fluid shear rates negatively influenced our fluorescence intensity. We highlight the importance of proper fluid flow considerations when integrating HIs with microfluidics.

Rapid sample preparation for detection of antibiotic resistance on a microfluidic disc platform.

Rapid, point-of-care (PoC) diagnostics for antibiotic susceptibility testing (AST) are critical in combating the antimicrobial resistance epidemic. While new, alternative technologies are capable of rapidly identifying antibiotic resistance, traditional AST methods, where a patient sample is incubated with different antibiotics, remain the most reliable and practical in determining antibiotic effectiveness. Here, we demonstrate a novel sample incubation technique on a microfluidic centrifugal disc (CD) as a proof of concept automated sample processing platform for AST. By using ribosomal RNA (rRNA) as a marker for cell growth, we demonstrated that incubation on the microfluidic CD was enhanced (>1.6 fold) for 11 out of 14 clinically relevant isolates of Escherichia coli compared to traditional shaker incubators. Finally, we utilize the system to identify antibiotic resistance of 11 E. coli isolates incubated with 5 different antibiotics in under 2 hours.

Nanofibrous Carbon Multifunctional Smart Scaffolds for Simultaneous Cell Differentiation and Dopamine Detection.

Advances in stem-cell therapy rely on new, multifunctional smart scaffolds (MSS) to promote growth while simultaneously characterizing stem cells undergoing selective differentiation. Nondestructive cell characterization techniques, such as electrochemical detection of lineage-specific metabolites, play a critical role in translational stem-cell therapy by providing clinicians with real-time information to evaluate cell-readiness for transplant. However, electrochemical sensors that provide biophysical cues capable of guiding cell fate, while preserving electroactive functionality, remain unavailable. In this work, a carbon MSS is fabricated by pyrolyzing polyacrylonitrile (PAN) with optimal multiwalled carbon nanotube (MWCNT) loading to optimize electrochemical activity and with a tunable surface to promote cell growth and organization. Carbon MSS is used to (1) enhance the morphology and differentiation of mouse neural stem/progenitor cells (mNSPCs) derived from different regions of the developing brain and (2) simultaneously detect a neurotransmitter, dopamine, from a model dopaminergic cell line growing on the electrode. The study presents a carbon multifunctional smart scaffold for advancing stem-cell therapy toward clinically relevant applications.

Rapid Iodine Sensing on Mechanically Treated Carbon Nanofibers.

In this work, we report on a rapid, efficient electrochemical iodine sensor based on mechanically treated carbon nanofiber (MCNF) electrodes. The electrode’s highly graphitic content, unique microstructure, and the presence of nitrogen heteroatoms in its atomic lattice contribute to increased heterogeneous electron transfer and improved kinetics compared to conventional pyrolytic carbons. The electrode demonstrates selectivity for iodide ions in the presence of both interfering agents and high salt concentrations. The sensor exhibits clinically relevant limits of detection of 0.59 µM and 1.41 µM, in 1X PBS and synthetic urine, respectively, and a wide dynamic range between 5 µM and 700 µM. These results illustrate the advantages of the material’s unique electrochemical properties for iodide sensing, in addition to its simple, inexpensive fabrication. The reported iodine sensor eliminates the need for specimen processing, revealing its aptitude for applications in point-of-care diagnostics.

Lab-on-a-CD: A Fully Integrated Molecular Diagnostic System.

The field of centrifugal microfluidics has experienced tremendous growth during the past 15 years, especially in applications such as lab-on-a-disc (LoD) diagnostics. The strength of LoD systems lies in its potential for development into fully integrated sample-to-answer analysis systems. This review highlights the technologies necessary to develop the next generation of these systems. In addition to outlining valving and other fluid-handling operations, we discuss the recent advances and future outlook in four categories of LoD processes: reagent storage, sample preparation, nucleic acid amplification, and analyte detection strategies.

CD-Based Microfluidics for Primary Care in Extreme Point-of-Care Settings.

We review the utility of centrifugal microfluidic technologies applied to point-of-care diagnosis in extremely under-resourced environments. The various challenges faced in these settings are showcased, using areas in India and Africa as examples. Measures for the ability of integrated devices to effectively address point-of-care challenges are highlighted, and centrifugal, often termed CD-based microfluidic technologies, technologies are presented as a promising platform to address these challenges. We describe the advantages of centrifugal liquid handling, as well as the ability of a standard CD player to perform a number of common laboratory tests, fulfilling the role of an integrated lab-on-a-CD. Innovative centrifugal approaches for point-of-care in extremely resource-poor settings are highlighted, including sensing and detection strategies, smart power sources and biomimetic inspiration for environmental control. The evolution of centrifugal microfluidics, along with examples of commercial and advanced prototype centrifugal microfluidic systems, is presented, illustrating the success of deployment at the point-of-care. A close fit of emerging centrifugal systems to address a critical panel of tests for under-resourced clinic settings, formulated by medical experts, is demonstrated. This emphasizes the potential of centrifugal microfluidic technologies to be applied effectively to extremely challenging point-of-care scenarios and in playing a role in improving primary care in resource-limited settings across the developing world.