Shake It or Shrink It: Mass Transport and Kinetics in Surface Bioassays Using Agitation and Microfluidics

Design and simulation of biomimetic microfluidic designs to achieve uniform flow and DNA capture for high-throughput multiplexing

High-throughput multi-analyte point-of-care detection is often constrained by the limited number of analytes that can be effectively monitored. This study introduces bio-inspired microfluidic designs optimized for multi-analyte detection using 38-42 biosensors. Drawing inspiration from the human spinal cord and leaf vein networks, these perfusion-oriented designs ensure uniform flow velocity and consistent molecular capture while maintaining spatial separation to prevent cross-talk. In silico optimizations achieved velocity profile uniformity with coefficients of variance of 0.89% and 0.86% for the spine- and leaf-inspired designs, respectively. However, simulations revealed that velocity uniformity alone is insufficient for accurate molecular capture prediction without consistent reaction site channel dimensions. The bio-inspired designs demonstrated superior performance, stabilizing-coefficient of variance below 20%-in DNA capture within 10 minutes, compared to 68 minutes for a simple branched design. This work underscores the potential of bio-inspired microfluidics to enable scalable, uniform, and high-performance systems for multi-analyte detection.

Microfluidics-based automatic immunofluorescence staining for single-molecule localization microscopy

Full automation of single-molecule localization microscopy (SMLM) is crucial for large-scale and high-throughput cellular imaging. It is well-known that SMLM typically consists of three major steps: immunofluorescence (IF) staining, optical imaging, and image processing. Currently, automation in optical imaging and image processing is almost complete; however, the automation of IF staining has been slow to advance, probably due to its complicated experimental operations. Here we present a low-cost automated method for IF staining, called super-resolution immunofluorescence staining by microfluidics (SRIF-fluidics). This method is suitable for both adherent and suspension cells and supports single-color and multi-color IF staining for SMLM. Our results show that SRIF-fluidics reduces antibody consumption by about 75% and shortens the sample preparation time from 5.6 hours (manual operation) to 2.5 ∼ 4.4 hours, depending on the sample types. Importantly, this method provides a satisfactory consistency of imaging results without sacrificing sample labeling quality. We believe that the method proposed in this paper is a necessary supplement to achieving fully automated SMLM and facilitating high-throughput SMLM in the near future.

Quantitative detection of pre-ovulatory luteinizing hormone surges in urine using the microfluidic vertical agitation approach

Identifying the time of ovulation is an important process for women seeking and avoiding pregnancy. Luteinizing hormone (LH) plays an important role in ovulation, which is very important in the reproductive mechanism. Therefore, detecting the LH level is of great importance in monitoring ovulation. In this study, sensitive, rapid and selective electrochemical biosensors were developed to detect LH quantitatively from human urine samples and to monitor the ovulation period. Isopotential region and current density optimization studies revealed that sensors with an electrode width and spacing of 1 mm had the optimum performance. Electrochemical impedance spectra evidenced immobilization of DSP self-assembled monolayers and anti-LH-beta antibody on the surface. While the mobile phone vibrator led to a 3.5-fold enhancement in response signals, the agitation system developed resulted in a 10-fold improvement. The sensors displayed detection limits of 1.02 and 1.53 mIU/ml in the range of 0-40 mIU/ml LH concentration obtained using two statistical approaches. Additionally, the sensors showed no cross-reactivity to hCG, which is very similar in structure and is widely reported to have high cross-reactivity.

Physiological platelet aggregation assay to mitigate drug-induced thrombocytopenia using a microphysiological system

Developing a reliable method to predict thrombocytopenia is imperative in drug discovery. Here, we establish an assay using a microphysiological system (MPS) to recapitulate the in-vivo mechanisms of platelet aggregation and adhesion. This assay highlights the role of shear stress on platelet aggregation and their interactions with vascular endothelial cells. Platelet aggregation induced by soluble collagen was detected under agitated, but not static, conditions using a plate shaker and gravity-driven flow using MPS. Notably, aggregates adhered on vascular endothelial cells under gravity-driven flow in the MPS, and this incident increased in a concentration-dependent manner. Upon comparing the soluble collagen-induced aggregation activity in platelet-rich plasma (PRP) and whole blood, remarkable platelet aggregate formation was observed at concentrations of 30 µg/mL and 3 µg/mL in PRP and whole blood, respectively. Moreover, ODN2395, an oligonucleotide, induced platelet aggregation and adhesion to vascular endothelial cells. SYK inhibition, which mediated thrombogenic activity via glycoprotein VI on platelets, ameliorated platelet aggregation in the system, demonstrating that the mechanism of platelet aggregation was induced by soluble collagen and oligonucleotide. Our evaluation system partially recapitulated the aggregation mechanisms in blood vessels and can contribute to the discovery of safe drugs to mitigate the risk of thrombocytopenia.

Molecular fingerprinting of biological nanoparticles with a label-free optofluidic platform

Label-free detection of multiple analytes in a high-throughput fashion has been one of the long-sought goals in biosensing applications. Yet, for all-optical approaches, interfacing state-of-the-art label-free techniques with microfluidics tools that can process small volumes of sample with high throughput, and with surface chemistry that grants analyte specificity, poses a critical challenge to date. Here, we introduce an optofluidic platform that brings together state-of-the-art digital holography with PDMS microfluidics by using supported lipid bilayers as a surface chemistry building block to integrate both technologies. Specifically, this platform fingerprints heterogeneous biological nanoparticle populations via a multiplexed label-free immunoaffinity assay with single particle sensitivity. First, we characterise the robustness and performance of the platform, and then apply it to profile four distinct ovarian cell-derived extracellular vesicle populations over a panel of surface protein biomarkers, thus developing a unique biomarker fingerprint for each cell line. We foresee that our approach will find many applications where routine and multiplexed characterisation of biological nanoparticles are required.

Interplay between environmental yielding and dynamic forcing modulates bacterial growth

Many bacterial habitats-ranging from gels and tissues in the body to cell-secreted exopolysaccharides in biofilms-are rheologically complex, undergo dynamic external forcing, and have unevenly distributed nutrients. How do these features jointly influence how the resident cells grow and proliferate? Here, we address this question by studying the growth of Escherichia coli dispersed in granular hydrogel matrices with defined and highly tunable structural and rheological properties, under different amounts of external forcing imposed by mechanical shaking, and in both aerobic and anaerobic conditions. Our experiments establish a general principle: that the balance between the yield stress of the environment that the cells inhabit, σy, and the external stress imposed on the environment, σ, modulates bacterial growth by altering transport of essential nutrients to the cells. In particular, when σy<σ, the environment is easily fluidized and mixed over large scales, providing nutrients to the cells and sustaining complete cellular growth. By contrast, when σy>σ, the elasticity of the environment suppresses large-scale fluid mixing, limiting nutrient availability and arresting cellular growth. Our work thus reveals a new mechanism, beyond effects that change cellular behavior via local forcing, by which the rheology of the environment may modulate microbial physiology in diverse natural and industrial settings.

A microfluidic cover converts a standard 96-well plate into a mass-transport-controlled immunoassay system

96-well microtiter plates, widely used in immunoassays, face challenges such as prolonged assay time and limited sensitivity due to the lack of analyte transport control. Orbital shakers, commonly employed to facilitate mass transport, offer limited improvements and can introduce assay inconsistencies. While microfluidic devices offer performance enhancements, their complexity and incompatibility with existing platforms limit their wide adoption. This study introduces a novel microfluidic 96-well cover designed to convert a standard 96-well plate to a mass-transport-controlled surface bioreactor. The cover employs microfluidic methods to enhance the diffusion flux of analytes toward the receptors immobilized on the well bottom. Both simulation and experimental results demonstrated that the cover significantly enhances the capture rate of analyte molecules, resulting in increased signal strength for various detection methods and a lower detection limit. The cover serves as an effective add-on to standard 96-well plates, offering enhanced assay performance without requiring modifications to existing infrastructure or reagents. This innovation holds promise for improving the efficiency and reliability of microtiter plate based immunoassays.

Theoretical analysis of immunochromatographic assay and consideration of its operating parameters for efficient designing of high-sensitivity cardiac troponin I (hs-cTnI) detection

Troponin is the American College of Cardiology and American Heart Association preferred biomarker for diagnosing acute myocardial infarction (MI). We provide a modeling framework for high sensitivity cardiac Troponin I (hs-cTnI) detection in chromatographic immunoassays (flow displacement mode) with an analytical limit of detection, i.e., LOD < 10 ng/L. We show that each of the various control parameters exert a significant influence over the design requirements to reach the desired LOD. Additionally, the design implications in a multiplexed fluidic network, as in the case of Simple Plex™ Ella instrument, are significantly affected by the choice of the number of channels or partitions in the network. We also provide an upgrade on the existing LOD equation to evaluate the necessary minimum volume to detect a particular concentration by considering the effects of stochastics and directly incorporating the target number of copies in each of the partitions in case of multiplexed networks. Even though a special case of cTnI has been considered in this study, the model and analysis are analyte agnostic and may be applied to a wide class of chromatographic immunoassays. We believe that this contribution will lead to more efficient designing of the immunochromatographic assays.

Regulating Biomolecular Surface Interactions Using Tunable Acoustic Streaming

Diffusion limitations and nonspecific surface absorption are great challenges for developing micro-/nanoscale affinity biosensors. There are very limited approaches that can solve these issues at the same time. Here, an acoustic streaming approach enabled by a gigahertz (GHz) resonator is presented to promote mass transfer of analytes through the jet mode and biofouling removal through the shear mode, which can be switched by tuning the deviation angle, α, between the resonator and the sensor. Simulations show that the jet mode (α ≤ 0) drives the analytes in the fluid toward the sensing surface, overcomes the diffusion limitation, and enhances the binding; while the shear mode (0 < α < π/4) provides a scouring action to remove the biofouling from the sensor. Experimental studies were performed by integrating this GHz resonator with optoelectronic sensing systems, where a 34-fold enhancement for the initial binding rate was obtained. Featuring high efficiency, controllability, and versatility, we believe that this GHz acoustic streaming approach holds promise for many kinds of biosensing systems as well as lab-on-chip systems.

Micro-/nanoscale robotics for chemical and biological sensing

The field of micro-/nanorobotics has attracted extensive interest from a variety of research communities and witnessed enormous progress in a broad array of applications ranging from basic research to global healthcare and to environmental remediation and protection. In particular, micro-/nanoscale robots provide an enabling platform for the development of next-generation chemical and biological sensing modalities, owing to their unique advantages as programmable, self-sustainable, and/or autonomous mobile carriers to accommodate and promote physical and chemical processes. In this review, we intend to provide an overview of the state-of-the-art development in this area and share our perspective in the future trend. This review starts with a general introduction of micro-/nanorobotics and the commonly used methods for propulsion of micro-/nanorobots in solution, along with the commonly used methods in their fabrication. Next, we comprehensively summarize the current status of the micro/nanorobotic research in relevance to chemical and biological sensing (e.g., motion-based sensing, optical sensing, and electrochemical sensing). Following that, we provide an overview of the primary challenges currently faced in the micro-/nanorobotic research. Finally, we conclude this review by providing our perspective detailing the future application of soft robotics in chemical and biological sensing.

Plasmon-Enhanced Expansion Microscopy

Expansion microscopy (ExM) is a rapidly emerging super-resolution microscopy technique that involves isotropic expansion of biological samples to improve spatial resolution. However, fluorescence signal dilution due to volumetric expansion is a hindrance to the widespread application of ExM. Here, we introduce plasmon-enhanced expansion microscopy (p-ExM) by harnessing an ultrabright fluorescent nanoconstruct, called plasmonic-fluor (PF), as a nanolabel. The unique structure of PFs renders nearly 15000-fold brighter fluorescence signal intensity and higher fluorescence retention following the ExM protocol (nearly 76%) compared to their conventional counterparts (<16% for IR-650). Individual PFs can be easily imaged using conventional fluorescence microscopes, making them excellent "digital" labels for ExM. We demonstrate that p-ExM enables improved tracing and decrypting of neural networks labeled with PFs, as evidenced by improved quantification of morphological markers (nearly a 2.5-fold increase in number of neurite terminal points). Overall, p-ExM complements the existing ExM techniques for probing structure-function relationships of various biological systems.

Skipping the Boundary Layer: High-Speed Droplet-Based Immunoassay Using Rayleigh Acoustic Streaming

Acoustic mixing of droplets is a promising way to implement biosensors that combine high speed and minimal reagent consumption. To date, this type of droplet mixing is driven by a volume force resulting from the absorption of high-frequency acoustic waves in the bulk of the fluid. Here, we show that the speed of these sensors is limited by the slow advection of analyte to the sensor surface due to the formation of a hydrodynamic boundary layer. We eliminate this hydrodynamic boundary layer by using much lower ultrasonic frequencies to excite the droplet, which drives a Rayleigh streaming that behaves essentially like a slip velocity. At equal average flow velocity in the droplet, both experiment and three-dimensional simulations show that this provides a three-fold speedup compared to Eckart streaming. Experimentally, we further shorten a SARS-CoV-2 antibody immunoassay from 20 min to 40 s taking advantage of Rayleigh acoustic streaming.

Flow Rate-Independent Multiscale Liquid Biopsy for Precision Oncology

Immunoaffinity-based liquid biopsies of circulating tumor cells (CTCs) hold great promise for cancer management but typically suffer from low throughput, relative complexity, and postprocessing limitations. Here, we address these issues simultaneously by decoupling and independently optimizing the nano-, micro-, and macro-scales of an enrichment device that is simple to fabricate and operate. Unlike other affinity-based devices, our scalable mesh approach enables optimum capture conditions at any flow rate, as demonstrated with constant capture efficiencies, above 75% between 50 and 200 μL min-1. The device achieved 96% sensitivity and 100% specificity when used to detect CTCs in the blood of 79 cancer patients and 20 healthy controls. We demonstrate its postprocessing capacity with the identification of potential responders to immune checkpoint inhibition (ICI) therapy and the detection of HER2 positive breast cancer. The results compare well with other assays, including clinical standards. This suggests that our approach, which overcomes major limitations associated with affinity-based liquid biopsies, could help improve cancer management.

Analyte Sensing with Catalytic Micromotors

Catalytic micromotors can be used to detect molecules of interest in several ways. The straightforward approach is to use such motors as sensors of their "fuel" (i.e., of the species consumed for self-propulsion). Another way is in the detection of species which are not fuel but still modulate the catalytic processes facilitating self-propulsion. Both of these require analysis of the motion of the micromotors because the speed (or the diffusion coefficient) of the micromotors is the analytical signal. Alternatively, catalytic micromotors can be used as the means to enhance mass transport, and thus increase the probability of specific recognition events in the sample. This latter approach is based on "classic" (e.g., electrochemical) analytical signals and does not require an analysis of the motion of the micromotors. Together with a discussion of the current limitations faced by sensing concepts based on the speed (or diffusion coefficient) of catalytic micromotors, we review the findings of the studies devoted to the analytical performances of catalytic micromotor sensors. We conclude that the qualitative (rather than quantitative) analysis of small samples, in resource poor environments, is the most promising niche for the catalytic micromotors in analytical chemistry.

Efficient Pathogen Capture and Sensing Promoted by Dynamic Deformable Nanointerfaces

The M13 bacteriophage (M13 phage) has emerged as an attractive bionanomaterial due to its chemistry/gene modifiable feature and unique structures. Herein, a dynamic deformable nanointerface is fabricated taking advantage of the unique feature of the M13 phage for ultrasensitive detection of pathogens. PIII proteins at the tip of the M13 phage are genetically modified to display 6His peptide for site-specific anchoring onto Ni-NTA microbeads, whereas pVIII proteins along the side of the M13 phage are orderly arranged with thousands of aptamers and their complementary strands (c-apt). The flexible M13 nanofibers with rich recognition sites act as octopus tentacles, resulting in a 19-fold improvement in the capture affinity toward the target. The competitive binding of the target pathogen releases c-apts and initiates rolling circle amplification (RCA). The sway motion of M13 nanofibers accelerates the diffusion of c-apts, thus promoting RCA efficiency. Benefiting from the strengthened capture ability toward the target and the accelerated RCA process, three-orders of magnitude improvement in the sensitivity is achieved, with a detection limit of 8 cfu mL^-1 for Staphylococcus aureus. The promoted capture ability and assay performance highlights the essential role of the deformable feature of the engineered interface. This may provide inspiration for the construction of more efficient reaction interfaces.

Automatic Microtitrator for Small Volume Samples

Electroanalytical sensors for point-of-care biomedical or point-of-use environmental sample analysis are gaining popularity due to low limits of detection, ease of miniaturization, convenience, and ability to work with small sample volumes. Since pH must be tightly controlled for optimum electrochemical performance, adjustment of pH in these samples is often a necessity. Yet manual titration is time-consuming and can be especially challenging for small volumes. End point determination can also be difficult. Current commercial automatic pH titrators are generally designed for large volume (>1 mL) batch titrations, while the existing microvolume titrators are semiautomatic at best, still relying on multiple manual steps. To address the gap, we developed an automatic microtitration system suitable for small volume samples. The system was validated using digested whole blood microsamples, successfully demonstrating accurate and rapid pH adjustment for samples as small as 100 μL. The simple modular construction of the system makes it compatible with acid washing for trace metal detection and other cleaning or sample preparation steps. The electrochemical detection of manganese heavy metal in blood at the parts per billion level showed no detectable contamination induced by the system. Ultimately, our simple, accurate, user-friendly automatic microtitration system can be used in the pH adjustment of microvolume samples and can potentially be extended to other pH end point analysis.

Quantifying Antibody Binding Kinetics on Fixed Cells and Tissues via Fluorescence Lifetime Imaging

We present a method for monitoring spatially localized antigen-antibody binding events on physiologically relevant substrates (cell and tissue sections) using fluorescence lifetime imaging. Specifically, we use the difference between the fluorescence decay times of fluorescently tagged antibodies in free solution and in the bound state to track the bound fraction over time and hence deduce the binding kinetics. We make use of a microfluidic probe format to minimize the mass transport effects and localize the analysis to specific regions of interest on the biological substrates. This enables measurement of binding constants (k_on) on surface-bound antigens and on cell blocks using model biomarkers. Finally, we directly measure p53 kinetics with differential biomarker expression in ovarian cancer tissue sections, observing that the degree of expression corresponds to the changes in k_on, with values of 3.27-3.50 × 10³ M^-1 s^-1 for high biomarker expression and 2.27-2.79 × 10³ M^-1 s^-1 for low biomarker expression.

Ultrafast Electrothermal Flow-Enhanced Magneto Biosensor for Highly Sensitive Protein Detection in Whole Blood

Current diagnostic tests for sensitive protein detection rely on immunological techniques, such as ELISA, which require sample purification, multiple washing steps and lengthy incubation, hindering their use for rapid testing. Here, we report a simple electrothermal flow-enhanced biosensor for ultrafast, high sensitivity measurements of protein biomarkers in whole blood. Magnetic nanobeads dually-labeled with a detection antibody and enzyme reporter are used to form immunocomplexes with the target protein, which are readily transported to the sensor via magnetic concentration. The incorporation of electrothermal flows enhances immunocomplex formation, allowing for rapid and sensitive detection without requiring blood purification or lengthy incubation. Proof of concept was carried out using Plasmodium falciparum histidine-rich protein 2 (PfHRP2), a malaria parasite biomarker, which could be detected at concentrations as low as 5.7 pg mL-1 (95 fM) in whole blood in 7 min. The speed, sensitivity and simplicity of this device make it attractive for rapid diagnostic testing.

Simple add-on devices to enhance the efficacy of conventional surface immunoassays implemented on standard labware

We propose microfluidic add-ons easily placed on standard assay labware such as microwells and slides to enhance the kinetics of immunoassays. The devices are compatible with mass production, well-established assay protocols and automated platforms.

Toward the Development of Rapid, Specific, and Sensitive Microfluidic Sensors: A Comprehensive Device Blueprint

Recent advances in nano/microfluidics have led to the miniaturization of surface-based chemical and biochemical sensors, with applications ranging from environmental monitoring to disease diagnostics. These systems rely on the detection of analytes flowing in a liquid sample, by exploiting their innate nature to react with specific receptors immobilized on the microchannel walls. The efficiency of these systems is defined by the cumulative effect of analyte detection speed, sensitivity, and specificity. In this perspective, we provide a fresh outlook on the use of important parameters obtained from well-characterized analytical models, by connecting the mass transport and reaction limits with the experimentally attainable limits of analyte detection efficiency. Specifically, we breakdown when and how the operational (e.g., flow rates, channel geometries, mode of detection, etc.) and molecular (e.g., receptor affinity and functionality) variables can be tailored to enhance the analyte detection time, analytical specificity, and sensitivity of the system (i.e., limit of detection). Finally, we present a simple yet cohesive blueprint for the development of high-efficiency surface-based microfluidic sensors for rapid, sensitive, and specific detection of chemical and biochemical analytes, pertinent to a variety of applications.

Biopatterning: The Art of Patterning Biomolecules on Surfaces

Patterning biomolecules on surfaces provides numerous opportunities for miniaturizing biological assays; biosensing; studying proteins, cells, and tissue sections; and engineering surfaces that include biological components. In this Feature Article, we summarize the themes presented in our recent Langmuir Lecture on patterning biomolecules on surfaces, miniaturizing surface assays, and interacting with biointerfaces using three key technologies: microcontact printing, microfluidic networks, and microfluidic probes.

Advection-Enhanced Kinetics in Microtiter Plates for Improved Surface Assay Quantitation and Multiplexing Capabilities

Surface assays such as ELISA are pervasive in clinics and research and predominantly standardized in microtiter plates (MTP). MTPs provide many advantages but are often detrimental to surface assay efficiency due to inherent mass transport limitations. Microscale flows can overcome these and largely improve assay kinetics. However, the disruptive nature of microfluidics with existing labware and protocols has narrowed its transformative potential. We present WellProbe, a novel microfluidic concept compatible with MTPs. With it, we show that immunoassays become more sensitive at low concentrations (up to 9× signal improvement in 12× less time), richer in information with 3-4 different kinetic conditions, and can be used to estimate kinetic parameters, minimize washing steps and non-specific binding, and identify compromised results. We further multiplex single-well assays combining WellProbe's kinetic regions with tailored microarrays. Finally, we demonstrate our system in a context of immunoglobulin subclass evaluation, increasingly regarded as clinically relevant.

Paper based analytical devices for blood grouping: a comprehensive review

The clinical importance of blood group (BG) antigens is related to their ability to induce immune antibodies that can cause hemolysis. Yet, ABO and D (Rh) are still considered to be the key antigens for healthy blood transfusion and secondary antigens are the next priority. Serological typing is the most widely used typing method. Rapid and accurate blood grouping plays an important role in some clinical conditions, rather than conventional techniques. Hence, developing a simple and economical model for rapid blood grouping would facilitate these tests. In recent decades, paper-based microfluidics such as μPADs has gained much interest in wide application areas such as point-of-care diagnostic. In this study, we evaluated μPADs that are performed for blood grouping and its recent progress. A comprehensive literature search was performed using databases including PUBMED, SCOPUS, Web of Science and Google Scholar. Keywords were blood grouping or typing, paper analytical device, rapid test, etc. After investigation of search results, 16 papers from 2010 to 2020 were included. Further information in detail was classified in Table 1. Generally, two principles for blood typing μPADs are introduced. The lateral chromatographic flow method and the vertical flow-through method that detects BG in a visual-based manner. To detect results with acceptable clarity many factors and challenges like paper, blood sample, buffer, Ab and RBC interaction and also μPADs stability need to be considered, which are discussed. In conclusion, the simplicity, stability, cheapness, portability and biocompatibility of μPADs for blood grouping confirming its utility and also they have the capability to robust, universal blood-grouping platform. Table 1 Summary of blood grouping tests using paper-based analytical devices Antigens Type of diagnosis Validation method Sample No Accuracy Action time Paper type Stability Sample dilution Buffer Ref A, B, Rh Forward volunteers records 5 - - Whatman No. 4 - 1/2 PBS* (Khan et al. 2010) A, B, Rh Forward gel assay test and conventional slide test 100 100% 1 min Whatman No. 4 and Kleeenex paper towel 7 Days in 4 °C 1/1 NSS (Al-Tamimi et al. 2012) A, B, Rh Forward gel card assay 99 100% 20 Sec + Washing Kleeenex paper towel - 1/1 NSS (Li et al. 2012) A, B, Rh Forward - - - - Kleeenex paper towel - 45/100 PSS (Li et al. 2013) A, B, Rh Forward gel card assay 98 100% 1.5 min Kleeenex paper towel - 85/100 PBS (Guan et al. 2014b) C, E, c, e, K, Jka, Jkb, M, N, S, P1, and Lea Forward gel card assay 266 100% - Kleeenex paper towel - 1/1 NSS (Li et al. 2014b) A, B, Rh Forward and Reverse conventional slide test 96 ≈ 91% 10 min Whatman No. 1 21 Days in 4 °C 1/2 NSS (Noiphung et al. 2015) C, c, E, e, K, k, Fya, Fyb, Jka, Jkb, M, N, S and s, P1, Lea and Leb Forward - 478 - - Kleeenex paper towel - 1/1 NSS, PBS (Then et al. 2015) A, B Forward and Reverse conventional slide test 76 100% 5-8 min Whatman No. 4 38 Days in 4 °C 1/4, 1/1 NSS (Songjaroen and Laiwattanapaisal 2016) D, K Forward volunteers records 210 - 7.5 min Kleenex paper towel - 1/1 NSS (Yeow et al. 2016) A, B, c, e, D, C, E, M, N, S, s, P1, Jka, Jkb, Lea, Leb, Fya, and Fyb Forward and Reverse gel card assay 3550 ≈100% 30 s Fiber glass and cotton linter 180 Days in 25 °C 45/100, 1/1 PBS (Zhang et al. 2017) A, B Forward conventional slide test 598 100% 3 min Whatman No. 113 14 Day in 4 °C 1/1 NSS (Songjaroen et al. 2018) A, B, Rh Forward conventional slide test - - 30 Sec + Washing Unrefined sisal paper - 1/2 NSS (Casals-Terré et al. 2019) A, B, Rh Forward - - - - Whatman No.1 - 1/1 NSS (Ansari et al. 2020) ABO & Rh Forward and Reverse conventional slide test - 100% Unrefined Eucalyptus papers - 1/2 NSS, PBS (Casals-Terré et al. 2020) A, B, Rh Forward - - - 30 Sec + Washing Whatman No. 4 modified with chitosan  ≥ 100 days in 25 °C 1/1 NSS (Parween et al. 2020) ^*phosphate buffer saline, normal saline solution.

Validation of Electrochemical Sensor for Determination of Manganese in Drinking Water

Manganese (Mn) is an essential nutrient for metabolic functions, yet excessive exposure can lead to neurological disease in adults and neurodevelopmental deficits in children. Drinking water represents one of the routes of excessive Mn exposure. Both natural enrichment from rocks and soil, and man-made contamination can pollute groundwater that supplies drinking water for a substantial fraction of the U.S. population. Conventional methods for Mn monitoring in drinking water are costly and involve a long turn-around time. Recent advancements in electrochemical sensing, however, have led to the development of miniature sensors for Mn determination. These sensors rely on a cathodic stripping voltammetry electroanalytical technique on a miniaturized platinum working electrode. In this study, we validate these electrochemical sensors for the determination of Mn concentrations in drinking water against the standard method using inductively coupled plasma mass spectrometry (ICP-MS). Drinking water samples (n = 78) in the 0.03 ppb to 5.3 ppm range were analyzed. Comparisons with ICP-MS yielded 100% agreement, ∼70% accuracy, and ∼91% precision. We envision the use of our system for rapid and inexpensive point-of-use identification of Mn levels in drinking water, which is especially valuable for frequent monitoring where contamination is present.

Mixing and oxygen transfer characteristics of a microplate bioreactor with surface-attached microposts

Bioprocess optimization for cell-based therapies is a resource heavy activity. To reduce the associated cost and time, process development may be carried out in small volume systems, with the caveat that such systems be predictive for process scale-up. The transport of oxygen from the gas phase into the culture medium, characterized using the volumetric mass transfer coefficient, k_L a, has been identified as a critical parameter for predictive process scale-up. Here, we describe the development of a 96-well microplate with integrated Redbud Posts to provide mixing and enhanced k_L a. Mixing in the microplate is characterized by observation of dyes and analyzed using the relative mixing index (RMI). The k_L a is measured via dynamic gassing out method. Actuating Redbud Posts are shown to increase rate of planar homogeneity (2 min) verse diffusion alone (120 min) and increase oxygenation, with increasing stirrer speed (3500-9000 rpm) and decreasing fill volume (150-350 μL) leading to an increase in k_L a (4-88 h^-1 ). Significant increase in Chinese Hamster Ovary growth in Redbud Labs vessel (580,000 cells mL^-1 ) versus the control (420,000 cells mL^-1 ); t(12.814) = 8.3678, p ≤ .001), and CD4⁺ Naïve cell growth in the microbioreactor indicates the potential for this technology in early stage bioprocess development and optimization.

Micro-scale technologies propel biology and medicine

Historically, technology has been central to new discoveries in biology and progress in medicine. Among various technologies, microtechnologies, in particular, have had a prominent role in the revolution experienced by the life sciences in the last few decades, which will surely continue in the years to come. In this Perspective, we illustrate how microtechnologies, with a focus on microfluidics, have evolved in trends/waves to tackle the boundary of knowledge in the life sciences. We provide illustrative examples of technology-enabled biological breakthroughs and their current and future use in clinics. Finally, we take a closer look at the translational process to understand why the incorporation of new micro-scale technologies in medicine has been comparatively slow so far.