Biology subjects

Grist, S. M.

Publications and source records attributed to Grist, S. M..

4 recordsLinked to original sources

bioRxiv2026

Multiplexed hormone immunoassays for women's health on a regenerable silicon photonic chip

Hormone dynamics are central to a multitude of conditions in women's health; however, limitations in the cost, convenience, and multiplexing capacity of current hormone assays preclude routine longitudinal hormone testing. This limitation severely restricts our understanding in this historically neglected field, presenting a need for improved bioanalytical tools to support hormone-informed care. Silicon photonic resonator sensors have excellent multiplexing capacity and scalable fabrication, and offer strong potential to meet this important need. Here we demonstrate, for the first time, multiplexed silicon photonic detection of two urinary hormone biomarkers, follicle-stimulating hormone (FSH) and pregnanediol-3-glucuronide (PdG), using sub-wavelength grating ring resonators and a polydopamine-based, regenerable surface chemistry. We combine a sandwich immunoassay for FSH and an antigen-down competitive immunoassay for PdG on the same chip, both amplified using a commercially available quantum-dot-streptavidin conjugate and with on-chip regeneration over multiple measurement cycles. In artificial urine, this proof-of-principle multiplexed assay achieves limits of detection of 0.594 ng/mL for FSH and 19.1 ng/mL for PdG. This architecture is inherently scalable to tens of hormone targets on a millimetre-scale chip (a >10x multiplexing improvement over typical lateral-flow immunoassays) enabling future low-cost, quantitative at-home hormone panels that could transform research, diagnostics, and treatment in women's health.

bioengineering↗

bioRxiv2025

What Could Go Wrong? Promoting Success by Planning for Failure in Label-Free Biosensor Assay Development

Label-free biosensors offer powerful platforms for detecting molecular interactions, but developing robust assays on these systems presents several challenges due to the complexity of the testing systems and intersection of disciplines. In this work, we describe a lightweight, 3-step experimental workflow supporting troubleshooting and root cause analysis that we developed during the design and optimization of silicon photonic biosensor assays in an academic research setting. Because such environments often lack the resources and formal quality-management infrastructure available in industry, our approach emphasizes practicality and ease of adoption. Drawing from our own assay failures and successes, we identify common failure modes, propose structured troubleshooting workflows, and provide case studies illustrating the application of established frameworks, including the Five Whys, the Plan-Do-Check-Act cycle, Open-Narrow-Close and the Ishikawa (fishbone) diagram. By applying this framework to our research, we increased our assay yield by a factor of 2, from ~45% to ~90%. This paper aims to support other teams engaged in label-free assay development by equipping them with practical tools and experimental best practices. HighlightsO_LIWe doubled assay yield from ~45% to ~90% by planning for failure, not just success. C_LIO_LITailored troubleshooting frameworks help pinpoint and solve various assay failures. C_LIO_LIApplying innovative problem-solving to workflows accelerates biosensor development. C_LIO_LISystematic troubleshooting improves assay development across a range of lab settings. C_LIO_LIA 3-step workflow highlighting what could go wrong supports continuous improvement. C_LI

bioengineering↗

bioRxiv2025

Resonating with replicability: factors shaping assay yield and variability in microfluidics-integrated silicon photonic biosensors

The integration of biosensors and microfluidics has facilitated the development of compact analytical devices capable of performing automated and information-rich detection of myriad targets, both in the lab and at the point of need. However, optimization of microfluidics-integrated biosensor systems and replicability challenges present roadblocks in validation and commercialization. Understanding factors contributing to yield and replicability in biosensor performance is key to the development of biosensor optimization frameworks and technology translation beyond the research setting. Hence, for the first time, we present a detailed analysis of factors affecting performance, assay yield, and intra- and inter-assay replicability in microfluidics-integrated silicon photonic (SiP) evanescent-field microring resonator biosensors. Strategies for mitigating bubbles--a major operational hurdle and contributor to instability and variability in microfluidics-integrated biosensors--are analyzed to improve assay yield. Effective bubble mitigation is demonstrated by combining microfluidic device degassing, plasma treatment, and microchannel pre-wetting with surfactant solution. Both intrinsic and analyte-detection performance metrics and their replicability are quantified for the first time for sub-wavelength grating-based SiP biosensors, highlighting a path to further optimization. Lastly, the effects of sensor functionalization on analyte detection performance and replicability are evaluated. We compare polydopamine-vs. Protein A-mediated bioreceptor immobilization chemistries and spotting-vs. flow-mediated bioreceptor patterning approaches. We find that simple polydopamine-mediated, spotting-based functionalization improves spike protein (1 {micro}g/mL) detection signal by 8.2x and 5.8x compared to polydopamine/flow and Protein A/flow approaches, respectively, and yields an inter-assay coefficient of variability below the standard 20% threshold for immunoassay validation. Overall, this work proposes a practical framework through which evanescent-field SiP biosensors, and microfluidics-integrated biosensors more generally, can be characterized, compared, and optimized to facilitate efficient biosensor development.

bioengineering↗

bioRxiv2019

3D projection electrophoresis for single-cell immunoblotting

While immunoassays and mass spectrometry are powerful single-cell protein analysis tools, bottlenecks remain in interfacing and throughput. Here, we introduce highly parallel, synchronous, three-dimensional single-cell immunoblots to detect both cytosolic and nuclear proteins. The novel threedimensional microfluidic device is a photoactive polyacrylamide gel with a high-density microwell array patterned on one face (x-y) for cell isolation and lysis. From each microwell, single-cell lysate is electrophoretically projected into the 3rd dimension (z-axis), separated by size, and photo-captured for immunoprobing and three-dimensional interrogation by confocal/light sheet microscopy. Design guidelines for throughput and separation performance are informed by simulation, analyses, and deconvolution postprocessing based on physics of 3D diffusion. Importantly, separations are nearly synchronous, whereas serial analyses can impart hours of delay between the first and last cell. We achieve an electrophoresis throughput of >2.5 cells/s (70X faster than serial sampling) and perform 25 immunoblots/mm2 device area (>10X increase over previous immunoblots). A straightforward device for parallel single-cell immunoblotting, projection electrophoresis promises to advance integration of protein-level profiles into the emerging single-cell atlas of genomic and transcriptomic profiles.

bioengineering↗