A gravity-independent single-phase electrode reservoir for capillary electrophoresis applications.

Capillary electrophoresis (CE) holds great promise as an in situ analytical technique for a variety of applications. However, typical instrumentation operates with open reservoirs (e.g., vials) to accommodate reagents and samples, which is problematic for automated instruments designed for space or underwater applications that may be operated in various orientations. Microgravity conditions add an additional challenge due to the unpredictable position of the headspace (air layer above the liquid) in any two-phase reservoir. One potential solution for these applications is to use a headspace-free, flow-through reservoir design that is sealed and connected to the necessary reagents and samples. Here, we demonstrate a flow-through high-voltage (HV) reservoir for CE that is compatible with automated in situ exploration needs, and which can be electrically isolated from its source fluidics (in order to prevent unwanted leakage current). We also demonstrate how the overall system can be rationally designed based on the operational parameters for CE to prevent electrolysis products generated at the electrode from entering the capillary and interfering with the CE separation. A reservoir was demonstrated with a 19 mm long, 1.8 mm inner diameter channel connecting the separation capillary and the HV electrode. Tests of these reservoirs integrated into a CE system show reproducible CE system operation with a variety of background electrolytes at voltages up to 25 kV. Rotation of the reservoirs, and the system, showed that their performance was independent of the direction of the gravity vector.

Three-Dimensional Analysis of Particle Distribution on Filter Layers inside N95 Respirators by Deep Learning.

The global COVID-19 pandemic has changed many aspects of daily lives. Wearing personal protective equipment, especially respirators (face masks), has become common for both the public and medical professionals, proving to be effective in preventing spread of the virus. Nevertheless, a detailed understanding of respirator filtration-layer internal structures and their physical configurations is lacking. Here, we report three-dimensional (3D) internal analysis of N95 filtration layers via X-ray tomography. Using deep learning methods, we uncover how the distribution and diameters of fibers within these layers directly affect contaminant particle filtration. The average porosity of the filter layers is found to be 89.1%. Contaminants are more efficiently captured by denser fiber regions, with fibers <1.8 µm in diameter being particularly effective, presumably because of the stronger electric field gradient on smaller diameter fibers. This study provides critical information for further development of N95-type respirators that combine high efficiency with good breathability.

Blood group alters platelet binding kinetics to von Willebrand factor and consequently platelet function.

Blood type O is associated with a lower risk of myocardial infarction. Platelets play a critical role in myocardial infarction. It is not known whether the expression of blood group antigens on platelet proteins alters platelet function; we hypothesized that platelet function would be different between donors with blood type O and those with non-O. To address this hypothesis, we perfused blood from healthy type O donors (n = 33) or non-O donors (n = 54) over pooled plasma derived von Willebrand factor (VWF) protein and purified blood type-specific VWF at arterial shear and measured platelet translocation dynamics. We demonstrate for the first time that type O platelets travel farther at greater speeds before forming stable bonds with VWF. To further characterize these findings, we used a novel analytical model of platelet interaction. Modeling revealed that the kinetics for GPIb/VWF binding rate are significantly lower for type O compared with non-O platelets. Our results demonstrate that platelets from type O donors interact less with VWF at arterial shear than non-O platelets. Our results suggest a potential mechanism for the reduced risk of myocardial infarction associated with blood type O.

In Vitro Measurement and Modeling of Platelet Adhesion on VWF-Coated Surfaces in Channel Flow.

The process of platelet adhesion is initiated by glycoprotein (GP)Ib and GPIIbIIIa receptors on the platelet surface binding with von Willebrand factor on the vascular walls. This initial adhesion and detachment of a single platelet is a complex process that involves multiple bonds forming and breaking and is strongly influenced by the surrounding blood-flow environment. In addition to bond-level kinetics, external factors such as shear rate, hematocrit, and GPIb and GPIIbIIIa receptor densities have also been identified as influencing the platelet-level rate constants in separate studies, but this still leaves a gap in understanding between these two length scales. In this study, we investigate the fundamental relationship of the dynamics of platelet adhesion, including these interrelating factors, using a coherent strategy. We build a, to our knowledge, novel and computationally efficient multiscale model accounting for multibond kinetics and hydrodynamic effects due to the flow of a cellular suspension. The model predictions of platelet-level kinetics are verified by our microfluidic experiments, which systematically investigate the role of each external factor on platelet adhesion in an in vitro setting. We derive quantitative formulas describing how the rates of platelet adhesion, translocation, and detachment are defined by the molecular-level kinetic constants, the local platelet concentration near the reactive surface determined by red-blood-cell migration, the platelet effective reactive area due to its tumbling motion, and the platelet surface receptor density. Furthermore, if any of these aspects involved have abnormalities, e.g., in a disease condition, our findings also have clinical relevance in predicting the resulting change in the adhesion dynamics, which is essential to hemostasis and thrombosis.

Dynamic platelet function is markedly different in patients with cancer compared to healthy donors.

Despite a fivefold increased risk of thromboembolism in patients with cancer, the mechanism of arterial thromboembolism is poorly understood. To address this, we investigated platelet function in cancer patients and healthy controls using an assay that mimics the arterial vasculature. Blood samples from cancer patients (n = 36) and healthy controls (n = 22) were perfused through custom-made parallel-plate flow chambers coated with von Willebrand factor (VWF) under arterial shear (1,500 s-1). Multiparameter measurements of platelet interactions with the immobilized VWF surface were recorded by digital-image microscopy and analyzed using custom-designed platelet-tracking software. Six measured parameters that characterize in detail the surface motion and surface binding of several hundred platelets per blood sample differed significantly in those with cancer from the healthy donors. In particular, it was found that patients with cancer had decreased numbers of platelets interacting, translocating and adhering to VWF. There were also reductions in the speed and distances that platelets traveled on VWF in comparison to healthy controls. Platelet function differed between those with early-stage cancer compared to those with later stage cancer. Patients with advanced cancer had an increased number of platelets stably adhering to VWF and greater platelet surface coverage after a given time of interaction. To the best of our knowledge, our results demonstrate for the first time that dynamic platelet function is markedly different in patients with cancer compared to healthy donors.

Self-Powered Microfluidic Device for Rapid Assay of Antiplatelet Drugs.

We report the development of a microfluidic device for the rapid assay in whole blood of interfacial platelet-protein interactions indicative of the efficacy of antiplatelet drugs, for example, aspirin and Plavix, two of the world's most widely used drugs, in patients with cardiovascular disease (CVD). Because platelet adhesion to surface-confined protein matrices is an interfacial phenomenon modulated by fluid shear rates at the blood/protein interface, and because such binding is a better indicator of platelet function than platelet self-aggregation, we designed, fabricated, and characterized the performance of a family of disposable, self-powered microfluidic chips with well-defined flow and interfacial shear rates suitable for small blood volumes (≤200 µL). This work demonstrates that accurate quantification of cell adhesion to protein matrices, an important interfacial biological phenomenon, can be used as a powerful diagnostic tool in those with CVD, the world's leading cause of death. To enable such measurements, we developed a simple technique to fabricate single-use self-powered chips incorporating shear control (SpearChips). These parallel-plate flow devices integrate on-chip vacuum-driven blood flow, using a predegassed elastomer component to obviate active pumping, with microcontact-printed arrays of 6-µm-diameter fluorescently labeled fibrinogen dots on a cyclic olefin polymer base plate as a means to quantitatively count platelet-protein binding events. The use of SpearChips to assess in whole blood samples the effects of GPIIb/IIIa and P2Y12 inhibitors, two important classes of "antiplatelet" drugs, is reported.

Examining platelet adhesion via Stokes flow simulations and microfluidic experiments.

While critically important, the platelet function at the high shear rates typical of the microcirculation is relatively poorly understood. Using a large scale Stokes flow simulation, Zhao et al. recently showed that RBC-induced velocity fluctuations cause platelets to marginate into the RBC free near-wall region [Zhao et al., Physics of Fluids, 2012, 24, 011902]. We extend their work by investigating the dynamics of platelets in shear after margination. An overall platelet adhesion model is proposed in terms of a continuous time Markov process and the transition rates are established with numerical simulations involving platelet-wall adhesion. Hydrodynamic drag and Brownian forces are calculated with the boundary element method, while the RBC collisions are incorporated through an autoregressive process. Hookean springs with first order bond kinetics are used to model receptor-ligand bonds formed between the platelet and the wall. The simulations are compared with in vitro microfluidic experiments involving platelet adhesion to Von Willebrand Factor (VWF) coated surfaces.

Analysis of binary mixtures of aqueous aromatic hydrocarbons with low-phase-noise shear-horizontal surface acoustic wave sensors using multielectrode transducer designs.

The present work investigates a compact sensor system that provides rapid, real-time, in situ measurements of the identities and concentrations of aromatic hydrocarbons at parts-per-billion concentrations in water through the combined use of kinetic and thermodynamic response parameters. The system uses shear-horizontal surface acoustic wave (SH-SAW) sensors operating directly in the liquid phase. The 103 MHz SAW sensors are coated with thin sorbent polymer films to provide the appropriate limits of detection as well as partial selectivity for the analytes of interest, the BTEX compounds (benzene, toluene, ethylbenzene, and xylenes), which are common indicators of fuel and oil accidental releases in groundwater. Particular emphasis is placed on benzene, a known carcinogen and the most challenging BTEX analyte with regard to both regulated levels and its solubility properties. To demonstrate the identification and quantification of individual compounds in multicomponent aqueous samples, responses to binary mixtures of benzene with toluene as well as ethylbenzene were characterized at concentrations below 1 ppm (1 mg/L). The use of both thermodynamic and kinetic (i.e., steady-state and transient) responses from a single polymer-coated SH-SAW sensor enabled identification and quantification of the two BTEX compounds in binary mixtures in aqueous solution. The signal-to-noise ratio was improved, resulting in lower limits of detection and improved identification at low concentrations, by designing and implementing a type of multielectrode transducer pattern, not previously reported for chemical sensor applications. The design significantly reduces signal distortion and root-mean-square (RMS) phase noise by minimizing acoustic wave reflections from electrode edges, thus enabling limits of detection for BTEX analytes of 9-83 ppb (calculated from RMS noise); concentrations of benzene in water as low as ~100 ppb were measured directly. Reliable quantification of BTEX analytes in binary mixtures is demonstrated in the sub-parts-per-million concentration range.

Identification and quantification of aqueous aromatic hydrocarbons using SH-surface acoustic wave sensors.

A need exists for compact sensor systems capable of in situ monitoring of groundwater for accidental releases of fuel and oil. The work reported here addresses this need, using shear horizontal surface acoustic wave (SH-SAW) sensors, which function effectively in liquid environments. To achieve enhanced sensitivity and partial selectivity for hydrocarbons, the devices are coated with thin chemically sensitive polymer films. Various polymer materials are investigated with the goal of identifying a set of coatings suitable for a sensor array. The system is tested with compounds indicative of fuel and oil releases, in particular, the BTEX compounds (benzene, toluene, ethylbenzene, and xylenes), in the low milligrams/liters to high micrograms/liters concentration range. Particular emphasis is placed on detection of benzene, a known carcinogen. It was observed that within the above concentration range, responses to multiple analytes in a mixture are additive, and there is a characteristic response time for each coating/analyte pair, which is largely independent of concentration. With the use of both the steady-state and transient-response information of SH-SAW sensor devices coated with three different polymer materials, poly(ethyl acrylate), poly(epichlorohydrin), and poly(isobutylene), a response pattern was obtained for benzene that is easily distinguishable from those of the other BTEX compounds. The time courses of the responses to binary analyte mixtures were modeled accurately using dual-exponential fits, yielding a characteristic concentration-independent time constant for each analyte/coating pair. Benzene concentration was quantified in the aqueous phase in the presence of the other BTEX compounds.

Three-dimensional wax patterning of paper fluidic devices.

In this paper we describe a method for three-dimensional wax patterning of microfluidic paper-based analytical devices (µPADs). The method is rooted in the fundamental details of wax transport in paper and provides a simple way to fabricate complex channel architectures such as hemichannels and fully enclosed channels. We show that three-dimensional µPADs can be fabricated with half as much paper by using hemichannels rather than ordinary open channels. We also provide evidence that fully enclosed channels are efficiently isolated from the exterior environment, decreasing contamination risks, simplifying the handling of the device, and slowing evaporation of solvents.

Organics Exposure in Orbit (OREOcube): A next-generation space exposure platform.

The OREOcube (ORganics Exposure in Orbit cube) experiment on the International Space Station (ISS) will investigate the effects of solar and cosmic radiation on organic thin films supported on inorganic substrates. Probing the kinetics of structural changes and photomodulated organic-inorganic interactions with real-time in situ UV-visible spectroscopy, this experiment will investigate the role played by solid mineral surfaces in the (photo)chemical evolution, transport, and distribution of organics in our solar system and beyond. In preparation for the OREOcube ISS experiment, we report here laboratory measurements of the photostability of thin films of the 9,10-anthraquinone derivative anthrarufin (51 nm thick) layered upon ultrathin films of iron oxides magnetite and hematite (4 nm thick), as well as supported directly on fused silica. During irradiation with UV and visible light simulating the photon flux and spectral distribution on the surface of Mars, anthrarufin/iron oxide bilayer thin films were exposed to CO2 (800 Pa), the main constituent (and pressure) of the martian atmosphere. The time-dependent photodegradation of anthrarufin thin films revealed the inhibition of degradation by both types of underlying iron oxides relative to anthrarufin on bare fused silica. Interactions between the organic and inorganic thin films, apparent in spectral shifts of the anthrarufin bands, are consistent with presumed free-electron quenching of semiquinone anion radicals by the iron oxide layers, effectively protecting the organic compound from photodegradation. Combining such in situ real-time kinetic measurements of thin films in future space exposure experiments on the ISS with postflight sample return and analysis will provide time-course studies complemented by in-depth chemical analysis. This will facilitate the characterization and modeling of the chemistry of organic species associated with mineral surfaces in astrobiological contexts.

Quantifying Global Origin-Diagnostic Features and Patterns in Biotic and Abiotic Acyclic Lipids for Life Detection.

Lipids are a geologically robust class of organics ubiquitous to life as we know it. Lipid-like soluble organics are synthesized abiotically and have been identified in carbonaceous meteorites and on Mars. Ascertaining the origin of lipids on Mars would be a profound astrobiological achievement. We enumerate origin-diagnostic features and patterns in two acyclic lipid classes, fatty acids (i.e., carboxylic acids) and acyclic hydrocarbons, by collecting and analyzing molecular data reported in over 1500 samples from previously published studies of terrestrial and meteoritic organics. We identify 27 combined (15 for fatty acids, 12 for acyclic hydrocarbons) molecular patterns and structural features that can aid in distinguishing biotic from abiotic synthesis. Principal component analysis (PCA) demonstrates that multivariate analyses of molecular features (16 for fatty acids, 14 for acyclic hydrocarbons) can potentially indicate sample origin. Terrestrial lipids are dominated by longer straight-chain molecules (C4-C34 fatty acids, C14-C46 acyclic hydrocarbons), with predominance for specific branched and unsaturated isomers. Lipid-like meteoritic soluble organics are shorter, with random configurations. Organic solvent-extraction techniques are most commonly reported, motivating the design of our novel instrument, the Extractor for Chemical Analysis of Lipid Biomarkers in Regolith (ExCALiBR), which extracts lipids while preserving origin-diagnostic features that can indicate biogenicity.

Individual platelet adhesion assay: measuring platelet function and antiplatelet therapies in whole blood via digital quantification of cell adhesion.

Widespread monitoring of platelet function and the effect of antiplatelet drugs will improve outcomes in cardiovascular patients, but platelet function testing is not routine in clinical practice. We report a rapid, accurate methodology to quantify platelet-protein interactions: a microarray of contact-printed 6-µm fibrinogen dots on a transparent substrate binds platelets from whole blood, one platelet per dot. The fractional occupancy of an array of fibrinogen dots after a predefined incubation time quantitatively assays platelet adhesion to the protein matrix. We demonstrate this technique by measurement of platelet adhesion to fibrinogen as a means to quantify the effect of the P2Y12 and αIIbß3 receptor inhibitors cangrelor and abciximab, respectively, both in vitro--by incubating the drug with a freshly drawn blood sample--and in blood from patients treated with antiplatelet agents. The effects of single- and dual-antiplatelet therapy are also assessed. Results from this platelet-binding assay are well correlated with standard techniques including flow cytometry and light transmission aggregometry. This assay technology, readily integrated with microfluidic platforms, is generally applicable to the assay of cell-protein interactions and promises more effective, rapid assay of drug effects in cardiovascular disease patients.

Assaying the efficacy of dual-antiplatelet therapy: use of a controlled-shear-rate microfluidic device with a well-defined collagen surface to track dynamic platelet adhesion.

We report the development and demonstration of an assay that distinguishes the pharmacological effects of two widely used antiplatelet therapies, aspirin (COX-1 inhibitor) and clopidogrel (P2Y12 inhibitor). Whole blood is perfused through a low-volume microfluidic device in contact with a well-characterized (ellipsometry, atomic force microscopy) acid-soluble type I collagen surface. Whole human blood treated in vitro with a P2Y12 inhibitor 2-methylthioadenosine 5'-monophosphate triethylammonium salt (2-MeSAMP) extended the time to the start of platelet recruitment, i.e., platelet binding to the collagen surface. Treatment with 2-MeSAMP also slowed the rate of aggregate buildup, with an overall reduced average platelet aggregate area after 8 min of constant blood flow. A far smaller effect was observed for in vitro treatment with aspirin, for which the rate of change of surface coverage is indistinguishable from controls. In whole blood obtained from patients under treatment with dual-antiplatelet therapy (aspirin and clopidogrel), a significant extension of time to platelet recruitment was observed along with a slowed rate of aggregate buildup and an average aggregate size approximately half that of control measurements. Differentiation of the pharmacological effects of these two well-targeted antiplatelet pathways suggests a role for this assay in determining the antiplatelet effects of these and related new therapeutics in clinical settings.

Electronic Nose Development and Preliminary Human Breath Testing for Rapid, Non-Invasive COVID-19 Detection.

We adapted an existing, spaceflight-proven, robust "electronic nose" (E-Nose) that uses an array of electrical resistivity-based nanosensors mimicking aspects of mammalian olfaction to conduct on-site, rapid screening for COVID-19 infection by measuring the pattern of sensor responses to volatile organic compounds (VOCs) in exhaled human breath. We built and tested multiple copies of a hand-held prototype E-Nose sensor system, composed of 64 chemically sensitive nanomaterial sensing elements tailored to COVID-19 VOC detection; data acquisition electronics; a smart tablet with software (App) for sensor control, data acquisition and display; and a sampling fixture to capture exhaled breath samples and deliver them to the sensor array inside the E-Nose. The sensing elements detect the combination of VOCs typical in breath at parts-per-billion (ppb) levels, with repeatability of 0.02% and reproducibility of 1.2%; the measurement electronics in the E-Nose provide measurement accuracy and signal-to-noise ratios comparable to benchtop instrumentation. Preliminary clinical testing at Stanford Medicine with 63 participants, their COVID-19-positive or COVID-19-negative status determined by concomitant RT-PCR, discriminated between these two categories of human breath with a 79% correct identification rate using "leave-one-out" training-and-analysis methods. Analyzing the E-Nose response in conjunction with body temperature and other non-invasive symptom screening using advanced machine learning methods, with a much larger database of responses from a wider swath of the population, is expected to provide more accurate on-the-spot answers. Additional clinical testing, design refinement, and a mass manufacturing approach are the main steps toward deploying this technology to rapidly screen for active infection in clinics and hospitals, public and commercial venues, or at home.

BioSentinel: A Biofluidic Nanosatellite Monitoring Microbial Growth and Activity in Deep Space.

Small satellite technologies, particularly CubeSats, are enabling breakthrough research in space. Over the past 15 years, NASA Ames Research Center has developed and flown half a dozen biological CubeSats in low Earth orbit (LEO) to conduct space biology and astrobiology research investigating the effects of the space environment on microbiological organisms. These studies of the impacts of radiation and reduced gravity on cellular processes include dose-dependent interactions with antimicrobial drugs, measurements of gene expression and signaling, and assessment of radiation damage. BioSentinel, the newest addition to this series, will be the first deep space biological CubeSat, its heliocentric orbit extending far beyond the radiation-shielded environment of low Earth orbit. BioSentinel's 4U biosensing payload, the first living biology space experiment ever conducted beyond the Earth-Moon system, will use a microbial bioassay to assess repair of radiation-induced DNA damage in eukaryotic cells over a duration of 6-12 months. Part of a special collection of articles focused on BioSentinel and its science mission, this article describes the design, development, and testing of the biosensing payload's microfluidics and optical systems, highlighting improvements relative to previous CubeSat life-support and bioanalytical measurement technologies.

Future space experiment platforms for astrobiology and astrochemistry research.

Space experiments are a technically challenging but a scientifically important part of astrobiology and astrochemistry research. The International Space Station (ISS) is an excellent example of a highly successful and long-lasting research platform for experiments in space, that has provided a wealth of scientific data over the last two decades. However, future space platforms present new opportunities to conduct experiments with the potential to address key topics in astrobiology and astrochemistry. In this perspective, the European Space Agency (ESA) Topical Team Astrobiology and Astrochemistry (with feedback from the wider scientific community) identifies a number of key topics and summarizes the 2021 "ESA SciSpacE Science Community White Paper" for astrobiology and astrochemistry. We highlight recommendations for the development and implementation of future experiments, discuss types of in situ measurements, experimental parameters, exposure scenarios and orbits, and identify knowledge gaps and how to advance scientific utilization of future space-exposure platforms that are either currently under development or in an advanced planning stage. In addition to the ISS, these platforms include CubeSats and SmallSats, as well as larger platforms such as the Lunar Orbital Gateway. We also provide an outlook for in situ experiments on the Moon and Mars, and welcome new possibilities to support the search for exoplanets and potential biosignatures within and beyond our solar system.

Application-Specific Adaptable Coatings for Sensors: Using a Single Polymer-Plasticizer Pair to Detect Aromatic Hydrocarbons, Mixtures, and Interferents in Water with Single Sensors and Arrays.

A relatively simple design procedure is presented for new, adaptable chemical sensor coatings made from a single polymer-plasticizer pair to detect single or a mixture of chemical compounds (e.g., BTEX, the small aromatic hydrocarbon family). Affinity between coating components and target analytes, expressed through Hansen solubility parameters and relative energy difference values, describes the sensitivity of the resultant coatings to each analyte. While analyte affinity is paramount for plasticizer selection, for the aqueous-phase sensing application described here, it must be traded off with the permanence in the host polymer, i.e., resistance to leaching into the ambient aqueous phase; deleterious effects including coating creep must also be minimized. By varying the polymer:plasticizer mixing ratio, the physical and chemical properties of the resultant coatings can be tuned across a range of sensing properties, in particular the differential response magnitude and rate, for multiple analytes. Together with the measurement of multiple sensor response parameters (relative sensitivity and response time constant) for each coating, this approach allows for identification and quantification of target analytes not previously separable using commercial off-the-shelf (COTS) polymer sensor coatings. Sensing results using a five-sensor array based on five different mixing ratios of a single plasticizer polymer pair (plasticizer: ditridecyl phthalate; polymer: polystyrene) demonstrate unique identification of mixtures of BTEX analytes, including differentiation of the chemical isomers ethylbenzene and total xylene (or "xylenes"), something not previously feasible for separation-free liquid-phase sensing with commercially available polymer coatings. Ultimately, the response of a single optimized sensor coating identified and quantified the components of various mixtures, including identification of likely interferents, using a customized estimation-theory-based multivariate signal-processing technique.

Identification and Quantitation of Aqueous Single- and Multianalyte Solutions of the Isomers Ethylbenzene, m-, p-, and o-Xylene Using a Single Specifically Tailored Sensor Coating and Estimation Theory-Based Signal Processing.

The isomer-specific detection and quantitation of m-, p-, and o-xylene and ethylbenzene, dissolved singly and as mixtures in aqueous solutions at concentrations from 100 to 1200 ppb by volume, is reported for a specifically designed polymer-plasticizer coating on a shear-horizontal surface acoustic wave (SH-SAW) device. The polystyrene-ditridecyl phthalate-blend coating was designed utilizing Hansen solubility parameters and considering the dipole moment and polarizability of the analytical targets and coating components to optimize the affinity of the sensor coating for the four chemical isomers. The two key coating sorption properties, sensitivity and response time constant, are determined by the (slightly different) dipole moments and polarizabilities of the four target analytes: as analyte dipole moment decreases, coating sensitivity increases; as analyte polarizability decreases, coating response time lengthens. Using the measured sensitivities and time constants for the targets, sensor signals were processed with exponentially weighted recursive-least-squares estimation (EW-RLSE) to identify (with near 100% accuracy) and quantify (with ± 5-7% accuracy) the isomers. This impressive performance was achieved by combining the specifically tailored, high-sensitivity coating and an SH-SAW platform (yielding a detection limit of 5 ppb for the analytes) and using the EW-RLS estimator, which estimates unknown parameters accurately even in the presence of measurement noise and for analytes with only minor differences in response. Identification of the xylene isomers is important for applications including environmental monitoring and chemical manufacturing.

Microfluidics Microbial Activity MicroAssay: An Automated In Situ Microbial Metabolic Detection System.

With no direct extant-life detection instrumentation included in a space mission since the 1970s, the advancement of new technologies to be included in future space missions is imperative. We developed, optimized, and tested a semi-automated prototype, the microfluidics Microbial Activity MicroAssay (µMAMA). This system metabolically characterizes and detects extant microbial life by way of metabolism-indicator redox dyes. We first evaluated the robustness and sensitivity of six redox dye/buffer combinations, and we then tested their responses to metabolic activity in astrobiological analog high-Arctic samples. We determined that the Biolog Inoculating Fluid (IF)-C and AlamarBlue buffered in IF-0a (aB-IF0a) dye/buffer combinations were optimal, as they detected metabolic activity from the fewest microbial cells (102 cells/mL) while maintaining efficacy over a broad physiochemical range of pH (0-13), temperature (-10°C to 37°C), salinity and perchlorate (tested up to 30%), and in the presence of a Mars regolith simulant (MMS-2). The µMAMA, which incorporated these redox dyes, detected extant active cold-adapted microbial life from high Arctic analog sites, including samples amended with substrates targeting chemolithoautotrophic metabolisms. Given µMAMA's small size (we estimate a complete planetary instrument could occupy as little as 3 L) and potential for automation, it could easily be incorporated into almost any landed platform for life detection missions.