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.

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.

Stem Cells in Aggregate Form to Enhance Chondrogenesis in Hydrogels.

There are a variety of exciting hydrogel technologies being explored for cartilage regenerative medicine. Our overall goal is to explore whether using stem cells in an aggregate form may be advantageous in these applications. 3D stem cell aggregates hold great promise as they may recapitulate the in vivo skeletal tissue condensation, a property that is not typically observed in 2D culture. We considered two different stem cell sources, human umbilical cord Wharton's jelly cells (hWJCs, currently being used in clinical trials) and rat bone marrow-derived mesenchymal stem cells (rBMSCs). The objective of the current study was to compare the influence of cell phenotype, aggregate size, and aggregate number on chondrogenic differentiation in a generic hydrogel (agarose) platform. Despite being differing cell sources, both rBMSC and hWJC aggregates were consistent in outperforming cell suspension control groups in biosynthesis and chondrogenesis. Higher cell density impacted biosynthesis favorably, and the number of aggregates positively influenced chondrogenesis. Therefore, we recommend that investigators employing hydrogels consider using cells in an aggregate form for enhanced chondrogenic performance.