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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.

The objective of this paper is to evaluate the accuracy of the NASA BioSentinel Pixel Dosimeter (BPD) using gamma-ray and neutron sources in a standard calibration lab. The dosimeter tested here is the ground-based version of the BPD that will be onboard the BioSentinel mission. The BPD was exposed to radiation from (60)Co, (137)Cs, and (252)Cf at selected distances (dose rates) at the Lawrence Livermore National Laboratory (LLNL) Radiation Calibration Laboratory (RCL), and the results were compared with NIST traceable benchmark values. It is recognized that these sources are not analogs for the space environment but do provide direct comparisons between BPD response and well characterized calibration lab values. For gamma rays, the BPD measured absorbed dose agrees to ≤ 3.8% compared with RCL benchmark values. For neutrons, the results show that the BPD is insensitive, i.e., the BPD detected only the gamma-ray dose component from (252)Cf. The LET spectra obtained for gamma rays from (60)Co and (252)Cf are consistent with expectations for these gamma-ray energies, but the LET spectrum from the (137)Cs gamma rays differs substantially. The potential causes for this difference are the high dose rate from (137)Cs and the lower secondary electron energy produced by (137)Cs gamma rays. However, neither of these results in errors in the absorbed dose. Based on comparisons with NIST-traceable standards, it is evident that the BPD can measure absorbed dose accurately from low LET charged particles. The sensor’s insensitivity to neutrons is unlikely to be a limitation for the BioSentinel mission due to the expected low secondary neutron fluence.

Background Breath samples collected from patients infected with respiratory viruses are necessary for viral detection using breath analyzer devices. Given the highly transmissible nature of many of these illnesses, sample collection requires a multi-layered approach to ensure the safety of the research staff responsible for obtaining and transporting these samples. Our team established a protocol to minimize exposure to and transmission of COVID-19 when collecting breath samples. Methods We collected breath samples from 64 participants, of which 31 (48.4%) were positive for SARS-CoV-2 at the time of their visit. Before we started sample collection, biosafety inspection was conducted. We used a five-pronged approach to enhance safety and minimize transmission. First, we collected specimens in an outdoor space while the patients were seated in their vehicles. Second, we used a disposable mouthpiece and a one-way valve to fill a 1L TEDLAR bag. Third, patients were instructed to close the valve tightly before returning it to the staff. Fourth, we placed the bag in secondary containers which were placed in tertiary containers to minimize any contact with aerosols in the TEDLAR bag. In the last step, we placed a portable HEPA filter near the indoor sample processing unit to minimize exposure and air contamination with the samples. Study staff donned all forms of necessary personal protective equipment, including gloves, gowns, N95 respirators, and protective eyewear, during sample collection and transportation. Results A total of 64 breath samples were collected from 64 adult participants from February to March 2022. A total of 30 participants (46.9%) were within 7 days of their initial diagnosis. All participants were able to successfully collect samples without additional resources or attempts. All samples were able to be transported successfully into the lab. No staff contracted COVID-19 during the study period. Conclusion Layered safety measures, including protective equipment, physical barriers, and well-ventilated environments mitigated the risks associated with breath sample collections from infected participants. Disclosures Yvonne A. Maldonado, MD, Pfizer: Grant/Research Support|Pfizer: Member, DSMB, Pfizer Meningococcal Vaccine clinical trial.

The E. coli AntiMicrobial Satellite (EcAMSat) was a successful spaceflight mission that performed an autonomous experiment to investigate the effects of microgravity on the antibiotic resistance of uropathogenic E. coli; the latest in a series of biology-focused CubeSats developed at NASA Ames Research Center. While maintaining the bacteria at 37 °C, the payload delivered growth medium, different doses of the antibiotic gentamicin, and finally the metabolic indicator alamarBlue to each of 48 microwells in the fluidic card. An LED and detector system was used to monitor the changes in absorbance in each experiment well at three wavelengths (470, 525, and 615 nm), from which the growth of cells and their metabolic activity could be measured. The success of the mission was in part due to leveraging lessons learned and proven technologies from previous bio-CubeSat missions, including modified spare hardware from the PharmaSat payload. This paper details the design and assembly of the biofluidic system payload; the modifications to the PharmaSat hardware required to run the EcAMSat experiment and the challenges those changes created; and finally, the testing approach employed to ensure the success of the payload during the flight campaign.

BioSentinel is a 6U nanosatellite planned to launch in 2020 as a secondary payload onboard NASA's Space Launch System first exploration mission, Artemis-1, from which it will be deployed to a lunar fly-by trajectory leading to a heliocentric orbit. BioSentinel will conduct the first in situ measurements of biological response to space radiation outside low Earth orbit (LEO) in five decades; it will thus address strategic knowledge gaps related to the biological effects of space radiation. BioSentinel will measure the DNA damage and response to ambient space radiation in a model biological organism, which will be compared to information provided by an onboard physical radiation sensor and to data obtained in LEO (on the International Space Station) and on Earth. The spacecraft will operate in a deep-space environment with functions that include command and data handling, communications, power generation and energy storage, and attitude determination and control, including micropropulsion. The BioSentinel spacecraft advances multiple nanosatellite systems in order to function beyond LEO; by doing so, it provides an adaptable instrument platform to perform a range of human-exploration-relevant measurements in multiple space environments. BioSentinel's results will be critical for improving interpretation of the biological effects of space radiation exposure, and for reducing the risk to humans associated with long-term space exploration.

We report the results of the EcAMSat (Escherichia coli Antimicrobial Satellite) autonomous space flight experiment, investigating the role of σs in the development of antibiotic resistance in uropathogenic E. coli (UPEC) in microgravity (µ-g). The presence of σs, encoded by the rpoS gene, has been shown to increase antibiotic resistance in Earth gravity, but it was unknown if this effect occurs in µ-g. Two strains, wildtype (WT) UPEC and its isogenic ΔrpoS mutant, were grown to stationary phase aboard EcAMSat, an 11-kg small satellite, and in a parallel ground-based control experiment; cell growth rates for the two strains were found to be unaltered by µ-g. After starvation for over 24 h, stationary-phase cells were incubated with three doses of gentamicin (Gm), a common treatment for urinary tract infections (which have been reported in astronauts). Cellular metabolic activity was measured optically using the redox-based indicator alamarBlue (aB): both strains exhibited slower metabolism in µ-g, consistent with results from previous smallsat missions. The results also showed that µ-g did not enhance UPEC resistance to Gm; in fact, both strains were more susceptible to Gm in µ-g. It was also found, via a second ground-control experiment, that multi-week storage in the payload hardware stressed the cells, potentially obscuring small differential effects of the antibiotic between WT and mutant and/or between µ-g and ground. Overall, results showed that the ∆rpoS mutant was 34–37% less metabolically active than the WT for four different sets of conditions: ground without Gm, ground with Gm; µ-g without Gm, µ-g with Gm. We conclude therefore that the rpoS gene and its downstream products are important therapeutic targets for treating bacterial infections in space, much as they are on the ground.

A relatively simple design procedure is presented for new, adaptable chemical sensor coatings made from a single polymer

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.

Space microbiology research contributes to human safety and performance during space exploration by advancing understanding of the effects of reduced gravity and/or radiation on cells and organisms. Astrobiology, on the other hand, seeks a more fundamental understanding of life and the universe; its objectives are also furthered by spaceflight experiments. Experimental progress in both fields is limited partly by access to space aboard human-tended spacecraft and space stations. CubeSats are helping address such limitations by proving to be effective biological experiment spaceflight platforms. NASA's Ames Research Center has developed and operated five CubeSats in low Earth orbit with microbiology or astrobiology missions; technical advances and lessons learned from each “nanosatellite” served as the starting point for the next. Here, we present technical and performance overviews of these biological CubeSats and their scientific results. A preview of the next biological CubeSat mission, bound for interplanetary space, along with potential future applications, is included.

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

A method to prepare a highly stable carboxylic acid functional surface on various substrates for use in bioassays is reported. A thin layer of a poly(methylmethacrylate) (PMMA) is achieved by spin coating dissolved PMMA onto a variety of underlying substrates at various thicknesses in a range of c. 5–27 nm. Varying the PMMA concentration, time and spinning speed controls the thickness of the spin coated layer. The root-mean-squared roughness values of the spin coated PMMA are less than 1.5 nm, resulting in smooth and uniform layer. Substrate functionalisation is carried out by either ultraviolet/ozone (UV/O3) or oxygen plasma oxidation. Both techniques result in initially stable, highly functional films as demonstrated by the covalent attachment of amino-modified oligonucleotides, however longevity studies comparing the stability of films attached following oxidative activation show better stability for UV/O3 activated substrates when compared to oxygen plasma activated substrates. PMMA films activated by UV/O3 yield highly stable (for up to 24 days) functional surfaces that retain immobilised biomolecules after several extended wash steps. In contrast, films attached to surfaces pre-treated with oxygen plasma discharge lose their functionality within 5 days of oxidation. Direct DNA and sandwich antibody assays were successfully demonstrated on the UV/O3 functionalised surfaces, showing a low level of non-specific binding. Furthermore, the quenching of fluorescently labelled biomolecules bound to PMMA-coated gold-coated slides is shown to be dependent on the PMMA thickness, indicating potential usage in surface-plasmon resonance-based assays.

We report here complete 6-month results from the orbiting Space Environment Survivability of Living Organisms (SESLO) experiment. The world&rsquo, s first and only long-duration live-biology cubesat experiment, SESLO was executed by one of two 10-cm cube-format payloads aboard the 5.5-kg O/OREOS (Organism/Organic Exposure to Orbital Stresses) free-flying nanosatellite, which launched to a 72&deg, inclination, 650-km Earth orbit in 2010. The SESLO experiment measured the long-term survival, germination, metabolic, and growth responses of Bacillus subtilis spores exposed to microgravity and ionizing radiation including heavy-ion bombardment. A pair of radiation dosimeters (RadFETs, i.e., radiation-sensitive field-effect transistors) within the SESLO payload provided an in-situ dose rate estimate of 6&ndash, 7.6 mGy/day throughout the mission. Microwells containing samples of dried spores of a wild-type B. subtilis strain and a radiation-sensitive mutant deficient in Non-Homologoous End Joining (NHEJ) were rehydrated after 14, 91, and 181 days in space with nutrient medium containing with the redox dye alamarBlue (aB), which changes color upon reaction with cellular metabolites. Three-color transmitted light intensity measurements of all microwells were telemetered to Earth within days of each 24-hour growth experiment. At 14 and 91 days, spaceflight samples germinated, grew, and metabolized significantly more slowly than matching ground-control samples, as measured both by aB reduction and optical density changes, these rate differences notwithstanding, the final optical density attained was the same in both flight and ground samples. After 181 days in space, spore germination and growth appeared hindered and abnormal. We attribute the differences not to an effect of the space environment per se, as both spaceflight and ground-control samples exhibited the same behavior, but to a pair of ~15-day thermal excursions, after the 91-day measurement and before the 181-day experiment, that peaked above 46 &deg, C in the SESLO payload. Because the payload hardware operated nominally at 181 days, the growth issues point to heat damage, most likely to component(s) of the growth medium (RPMI 1640 containing aB) or to biocompatibility issues caused by heat-accelerated outgassing or leaching of harmful compounds from components of the SESLO hardware and electronics.

Human immune response is compromised and bacteria can become more antibiotic resistant in space microgravity (MG). We report that under low-shear modeled microgravity (LSMMG), stationary-phase uropathogenic Escherichia coli (UPEC) become more resistant to gentamicin (Gm), and that this increase is dependent on the presence of σs (a transcription regulator encoded by the rpoS gene). UPEC causes urinary tract infections (UTIs), reported to afflict astronauts; Gm is a standard treatment, so these findings could impact astronaut health. Because LSMMG findings can differ from MG, we report preparations to examine UPEC's Gm sensitivity during spaceflight using the E. coli Anti-Microbial Satellite (EcAMSat) as a free-flying "nanosatellite" in low Earth orbit. Within EcAMSat's payload, a 48-microwell fluidic card contains and supports study of bacterial cultures at constant temperature; optical absorbance changes in cell suspensions are made at three wavelengths for each microwell and a fluid-delivery system provides growth medium and predefined Gm concentrations. Performance characterization is reported here for spaceflight prototypes of this payload system. Using conventional microtiter plates, we show that Alamar Blue (AB) absorbance changes can assess the Gm effect on E. coli viability, permitting telemetric transfer of the spaceflight data to Earth. Laboratory results using payload prototypes are consistent with wellplate and flask findings of differential sensitivity of UPEC and its ∆rpoS strain to Gm. if σs plays the same role in space MG as in LSMMG and Earth gravity, countermeasures discovered in recent Earth studies (aimed at weakening the UPEC antioxidant defense) to control UPEC infections would prove useful also in space flights. Further, EcAMSat results should clarify inconsistencies from previous space experiments on bacterial antibiotic sensitivity and other issues.

Platelet function in pregnancy is poorly understood. Previous studies of platelet function in pregnancy have used non-physiological assays of platelet function with conflicting results. This study using a physiological assay of platelet function investigated platelet interactions with von Willebrand Factor (VWF) in blood from healthy pregnant women and healthy non-pregnant controls. Blood samples (200 µl) from third-trimester pregnancies (n = 21) and non-pregnant controls (n = 21) were perfused through custom-made parallel-plate flow chambers coated with VWF under arterial shear (1,500 s−1). Multi-parameter measurements of platelet interactions with the immobilized VWF surface were recorded by digital-image microscopy and analysed using custom-designed platelet-tracking software. Platelet interactions with VWF decreased in healthy third-trimester pregnant participants relative to controls. This effect is most likely due to haemodilution which occurs physiologically during pregnancy. Interestingly, platelets in blood from pregnant participants translocated more slowly on VWF under arterial-shear conditions. These decreases in platelet translocation speed were independent of haemodilution, suggesting intrinsic changes in platelet function with pregnancy.

We report the results of the EcAMSat (Escherichia coli Antimicrobial Satellite) autonomous space flight experiment, investigating the role of σ

The design of new, adaptable chemical sensor coatings using a single polymer-plasticizer pair for detection of single or multiple chemical compounds (e.g. BTEX) in aqueous solutions is presented. By modifying blend mixing ratios, the sensing characteristics of the coatings can be varied. Together with extraction of multiple sensing parameters (i.e. shear modulus, sensitivity, response time constant, etc.), this allows for more accurate analyte identification and quantification. Using a selected single polymer-plasticizer pair, several coatings were designed and used to build a sensor array. Sensing data indicates sufficient selectivity for unique identification of single analyte solutions. For solutions of multiple analytes and interferents, a different approach involving a single coated sensor characterized for all possible target chemicals and estimation theory-based multivariate signal processing was implemented. Results show accurate analyte identification and estimation of concentrations for multi-analyte solutions.

Most chemical sensors are only partially selective to any specific target analyte(s), making identification and quantification of analyte mixtures challenging, a problem often addressed using arrays of partially selective sensors. This work presents and experimentally verifies a signal-processing technique based on estimation theory for online identification and quantification of multiple analytes using only the response data collected from a single polymer-coated sensor device. The demonstrated technique, based on multiple stages of exponentially weighted recursive least-squares estimation (EW-RLSE), first determines which of the analytes included in the sensor response model are absent from the mixture being analyzed; these are then eliminated from the model prior to executing the final stage of EW-RLSE, in which the sample's constituent analytes are more accurately quantified. The overall method is based on a sensor response model with specific parameters describing each coating-analyte pair and requires no initial assumptions regarding the concentrations of the analytes in a given sample. The technique was tested using the measured responses of polymer-coated shear-horizontal surface acoustic wave devices to multi-analyte mixtures of benzene, toluene, ethylbenzene, xylenes, and 1,2,4-trimethylbenzene in water. The results demonstrate how this method accurately identifies and quantifies the analytes present in a sample using the measured response of just a single sensor device. This effective, simple, lower-cost alternative to sensor arrays needs no arduous training protocol, just measurement of the response characteristics of each individual target analyte and the likely interferents and/or classes thereof.

Introduction The eight-carbon aromatic isomers ethylbenzene and m-, p-, and o-xylene are difficult to separate from one another due to similarities in molecular structure and physicochemical properties. Separating these isomers is often necessary for industrial chemical synthesis [1]. Additionally, each isomer displays slightly different toxicity [2]. However, in drinking water guidelines, only data for total xylenes is provided because separate quantification of each isomer without the use of sophisticated spectroscopic or chromatographic methods is difficult. Furthermore, for most sensors based on sorption into polymer coatings, polymer/water partition coefficients for these analytes are much lower than polymer/air partition coefficients, resulting in low sensitivity and poor selectivity in their liquid-phase sensing. One method for addressing the above issues is to design multi-component sensor coatings that highlight the small variations in isomer structures. Such coatings can be designed by selecting coating components based on their chemical and physical properties, as well as the properties of the target analytes [3]. Properly designed coatings will show favorable sensing parameters (sensitivity, partial selectivity) in liquid-phase measurements compared to commercially available single-component polymers. Initial results indicate that selectivity of multi-component coatings can be significantly higher, thus enabling identification of chemical isomers, which were previously not (or barely) distinguishable in the liquid phase, with limits of detection in the low parts-per-billion (ppb) by weight. Furthermore, by utilizing advanced sensor signal processing [4] to analyze sensor data, minute response differences between the isomers ethylbenzene and the three xylenes can be uniquely identified, even in solutions of multiple analytes. Sensor Coating Design The design of chemical sensor coatings should select properties of the coating components, in light of the target analytes, that predict and control sensing behavior. The sensing mechanism utilized here relies on bulk absorption of target analytes into polymer coatings. Polarity/dipole moment and polarizability of coating and target isomers affect the absorption process and, as a result, the sensitivity of the coated sensor to the analyte. Multi-component coatings using polymer-plasticizer blends to generate Hansen solubility parameters (HSP) that favor strong coating-analyte interactions, i.e. favorable coating/water analyte partition coefficients, were designed for this work. These coatings exhibit significantly increased sensitivity and partial selectivity to target isomers compared to single-component polymers, such as poly(epichlorohydrin) or poly(isobutylene). As a result, minute variations in analyte properties (polarity/dipole moment, polarizability, etc.) can be detected at lower analyte concentrations. The designed coatings consist of blends of polystyrene (PS) and one of two plasticizers, diisooctyl azelate (DIOA) or ditridecyl phthalate (DTP). Identification of ethylbenzene and xylene is demonstrated for each polymer-plasticizer pair, with sensitivities for ethylbenzene and each xylene isomer in good agreement with trends in dipole moments and polarizabilities. Method Solutions of multi-component coatings were prepared with varying plasticizer-to-polymer weight ratios (given below) and with varying concentrations of polymer-plasticizer blend in the solvent. Coatings were deposited onto SH-SAW sensor devices via spin coating for use in direct liquid-phase measurements. Coating thicknesses were determined by profilometry. Coated sensors were exposed to diluted aqueous solutions of target analytes in flow-through measurements. The concentrations of analyte solutions were independently confirmed using a gas-chromatograph photoionization detector (GC-PID) system. Frequency responses of coated sensors are used to extract sensing parameters such as sensitivity, response time constant, and viscoelastic properties of the coatings. Extracted sensing parameters for each isomer serve as inputs for an advanced estimation-theory-based sensor signal-processing technique that quantifies mixtures. Results and Conclusions Table 1 shows relative energy difference (RED) values for pairs of coatings and analytes calculated using Equation 1, as well as dipole moment, polarizability, and measured sensitivity and response time constant for each isomer. The polymer-plasticizer blend coatings selected are 17.5% DIOA-PS and 30% DTP-PS. RED values for each pair of materials are well below 1.0, indicating excellent miscibility. While differences between isomers are relatively small, the measured variation in responses is highlighted with an appropriate multivariate signal-processing method. The extracted average sensitivity and average response time constant for each coating/analyte pair, shown in Table 1, correlate well with the trends in analytes’ dipole moments and polarizabilities. High sensitivities to ethylbenzene and xylene isomers are observed. Responses of the DIOA-PS coating to ethylbenzene and total xylenes are easily distinguishable from one another. Figure 1 shows single-analyte response curves for the DTP-PS coating for ethylbenzene and m-, p-, and o-xylene. Sensing parameters were extracted from the responses, thus allowing minute differences to be clearly observed. It is demonstrated that DTP-PS coatings show partial selectivity between ethylbenzene, m-, p-, and o-xylene. Figure 2 shows the response curve of a multi-analyte solution of the three xylene isomers, with estimated and measured concentrations for each isomer in the mixture in Table 2. Experimental responses and extracted results strongly support that selectivity to each xylene isomer can be achieved with appropriate sensor coating design. References [1] Y. Yang, P. Bai, X. Guo, Separation of Xylene Isomers: A Review of Recent Advances in Materials, ACS Sens., 56, 14725-14753 2017; doi: 10.1021/acs.iecr.7b03127 [2] Safety Data Sheets for ethylbenzene and m-, p-, and o-xylene, available online: https://hazard.com/msds/ [3] P. Adhikari, L. Alderson, F. Bender, A.J. Ricco, F. Josse, Investigation of Polymer-Plasticizer Blends as SH-SAW Sensor Coatings for Detection of Benzene in Water with High Sensitivity and Long-Term Stability, ACS Sens., 2, 157-164 2017; doi: 10.1021/acssensors.6b00659 [4] K. Sothivelr, F. Bender, F. Josse, E.E. Yaz, A.J. Ricco, Quantitative Detection of Complex Mixtures using a Single Chemical Sensor: Analysis of Response Transients using Multi-Stage Estimation, ACS Sens., 4, 1682-1690, 2019; doi: 10.1021/acssensors.9b00564 Figure 1

Thermoelectric devices convert thermal energy to electrical energy and are particularly well-suited for energy harvesting from waste heat. Even as the number of electronic devices used in daily life proliferates, technical advances diminish the average power such devices require to perform a given function. Localized thermal gradients that abound in our living environments, despite having modest energy densities, are therefore becoming increasingly viable and attractive to power such devices. With this motivation, we report the design, fabrication, and characterization of single-wall carbon nanotube thermoelectric devices (CNT-TDs) on flexible polyimide substrates as a basis for wearable energy converters. Our aqueous-solution-based film fabrication process could enable readily scalable, low-cost TDs; here, we demonstrate CNT-hydroxypropyl cellulose (HPC) composite thermoelectric films by aerosol jet printing. The electrical conductivity of the composite films is controlled through the number of CNT/HPC layers printed in combination with control of the annealing conditions. The HPC initially disperses the CNTs in deionized water, the greenest of solvents, and is subsequently partially eliminated from the film by annealing, with concomitant morphological changes that we characterized by TEM. HPC removal is key to obtaining good electrical conductivity (0.94 to 1.10 × 105 S/m) and Seebeck coefficients (36 to 43 μV/K). We also report a power factor of 208 μW m−1 K−2 for a CNT-TD composed of 15 layers of CNT/HPC, promising performance for CNT-based flexible TDs that are deposited from aqueous solution, stable in air, and require no additional doping or sorting processes.

We compare immobilization methods for oligonucleotides on carboxylic acid surfaces with the goal of improving hybridization efficiency for single-stranded DNA (ssDNA) bioassays. When immobilized via 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC), ssDNA (either modified with a terminal amine or not) specifically binds to the surface; without EDC, binding is minimal. EDC-activated probes can, however, bind covalently to the surface through nucleobase as well as terminal amino groups. Unmatched base pairs from the former are detected via melting curve analysis: the target begins to unwind at ∼40 °C below the double-strand melting temperature of ∼64 °C. To eliminate such backbone binding, we immobilized azide-functionalized DNA via click chemistry, resulting in hybridization efficiencies 5 times higher than with EDC. This improvement, and the room-temperature hybridization of the click chemistry process, make it an important alternative to EDC for reliable DNA assays with maximum specificity and sensitivity.

The imaging of shear-mediated dynamic platelet behavior interacting with surface-immobilized von Willebrand factor (vWF) has tremendous potential in characterizing changes in platelet function for clinical diagnostics purposes. However, the imaging output, a series of images representing platelets adhering and rolling on the surface, poses unique, non-trivial challenges for software algorithms that reconstruct the positional trajectories of platelets. We report on an algorithm that tracks platelets using the output of such flow run experiments, taking into account common artifacts encountered by previously-published methods, and we derive seven key metrics of platelet dynamics that can be used to characterize platelet function. Extensive testing of our method using simulated platelet flow run data was carried out to validate our tracking method and derived metrics in capturing key platelet-vWF interaction-dynamics properties. Our results show that while the number of platelets present on the imaged area is the leading cause of errors, flow run data from two experiments using whole blood samples showed that our method and metrics can detect platelet property changes/differences that are concordant with the expected biological outcome, such as inhibiting key platelet receptors such as P2Y1, glycoprotein (GP)Ib and GPIIb/IIIa. These findings support the use of our methodologies to characterize platelet function among a wide range of healthy and disease cohorts.

Essentials It is unclear if platelet function differs between preterm and full-term neonates. Platelet behavior was characterized using a flow-based assay on von Willebrand Factor (VWF). Preterms had increased platelet interaction with VWF and glycoprotein Ibα expression. Platelets from preterm neonates behave differently on VWF compared to full-term neonates. SUMMARY Background Very low birth weight (VLBW) preterm neonates have an increased risk of hemorrhage-related morbidity and mortality as compared with their full-term counterparts. It is unclear whether platelet function differs between preterm and full-term neonates. This is partly because of the large volumes of blood required to perform standard platelet function tests, and the difficulty in obtaining such samples in neonates. Objectives This study was designed to characterize platelet behavior in neonates with a physiologic flow-based assay that quantifies platelet function in microliter volumes of blood under arterial shear. Methods Blood from VLBW preterm neonates of ≤ 32 weeks' gestation (n = 15) and full-term neonates (n = 13) was perfused under arterial shear over surface-immobilized von Willebrand factor (VWF). Platelet behavior was recorded by digital-image microscopy and analyzed. Surface expression of platelet glycoprotein (GP) Ibα and GPIIIa of VLBW preterm and full-term neonates was also measured. Results VLBW preterm neonates had increased numbers of platelets interacting with VWF, and increased GPIbα expression on the platelet surface. Despite the increased numbers of VWF interactions as reflected by flow-driven platelet translocation along the protein surface, no significant differences were observed in the numbers of platelets that adhered in a stationary fashion to VWF. Platelets from VLBW preterm neonates and those from full-term neonates behaved differently on VWF. Conclusions These differences in platelet function may contribute to the higher incidence of bleeding observed in VLBW preterm neonatal populations, or may represent a compensatory mechanism to counteract this risk of bleeding.

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.

Compact sensor systems for on-site monitoring of groundwater for trace organic compounds in the liquid phase are currently under development in our laboratories. Potential challenges include sensor baseline drift and the presence of outliers in the data, along with difficulties extracting the contribution of individual BTEX compound (benzene, toluene, ethylbenzene, and xylenes) from the sensor response to mixtures containing multiple chemically similar compounds. As a first step, the approach presented here permits online estimation of analyte concentrations in binary mixtures of BTEX compounds in the presence of linear baseline drift and outliers. This paper investigates a sensor signal-processing approach based on estimation theory, specifically, Kalman filter (KF), extended KF, and discrete low-pass filter. The approach permits online linear baseline drift correction, filtering of outlier points, and estimation of analyte concentration(s) in binary mixtures and single analyte samples, before the sensor response reaches steady state. Sensor signals from mixtures of BTEX compounds were analyzed because these compounds are good indicators of accidental releases of fuel and oil into groundwater. Models were first developed for the sensor response so that estimation theory can be used to obtain the sensor parameters. The baseline-drift correction technique uses KF to perform online linear extrapolation or interpolation. The presented combination of sensor signal-processing techniques was simultaneously tested using actual measured data. Unknown sensor parameters and identification of analytes in samples were obtained within a relatively short period of time (8 min or less for the present sensor system), well before the sensor response reaches equilibrium.

A 3D-printed microfluidic device coupled with a fluidic processing system was developed to enable autonomous end-to-end sample handling and electrochemical characterization of an ocean world analogue solution – synthetic seawater (SW). This dual-channel microfluidic cell was populated with 14 electrodes and performed electrochemical measurements similar to those used in the MECA Wet Chemistry Laboratory on board NASA’s Phoenix Lander that landed on Mars in 2008. Biological and metallic redox events were evaluated using cyclic voltammetry with Au, Pt, and glassy carbon electrodes, with the latter displaying superior sensitivity and selectivity. Conductivity and pH were measured using Pt and iridium oxide electrodes respectively, and SW anions such as chloride were quantified using chronopotentiometry with a Ag electrode. The fluidic handling system demonstrated sample transportation to the microfluidic device for electrochemical measurements, and could be readily adapted to accommodate different pre-processing steps. Overall, this study demonstrates the use of electrochemical sensors as part of an autonomous microfluidic handling system that would be functionally analogous to an electrochemical instrument designed for Ocean World exploration.

One of the highest science risks during NASA missions involving living organisms, including the search for them and/or their biomarkers or signatures, is the quality and reliability of sample preparation and handling prior to in-situ analysis (1; 2). Afluidic instrument is being developed, Charged Info-storage Polymer Prep System (ChIPPS), that will enable automated preparation of an environmental sample by extracting, concentrating, and desalting information-storage polymers. Linear charged polymers with multiple functional block types—typified by, though not limited to, the nucleic acids DNA and RNA— are a class of molecules understood to be necessary for life’s function and replication (3). The capability to characterize charged polymers for detecting biosignatures is driven by the emergence of nanopore technology. ChIPPS will prepare environmental samples for downstream delivery to biosignatures detection instruments, such as those being developed using nanopore technologies. References: (1) La Duc, M.T.et al."Comparative analysis of methods for the purification of DNA from low‐bio-mass samples based on total yield and conserved microbial diversity," JRapid Methods & Automation Microbio17.3(2009): 350-68. (2) Salmon, K.et al."Global gene expression profiling in Escherichia coliK12 the effects of oxy-gen availability and FNR," J.BioChem278.32(2003): 29837-55. (3) Benner, Steven A., and Daniel Hutter. "Phosphates, DNA, and the search for nonterrean life: A second generation model for genetic molecules," BioorgChem30.1(2002): 62-80