A smartphone-integrated aptasensor for pesticide detection using gold-decorated microparticles.

The increasing incidence of environmental concerns related to excessive use of pesticides, such as imidacloprid and carbendazim, poses risks to pollinators, water bodies, and human health, prompting regulatory scrutiny and bans in developed countries. In this study, we propose a portable smartphone-based biosensor for rapid and label-free colorimetric detection by using the gold-decorated polystyrene microparticles (Ps-AuNP) functionalized with specific aptamers to imidacloprid and carbendazim on a microfluidic paper-based analytical device (µ-PAD). Four aptamers were selected for the detection of these pesticides and their sensitivity and selectivity performance was evaluated. The sensitivity results show a detection limit for imidacloprid of 3.12 ppm and 1.56 ppm for carbendazim. The aptamers also exhibited high selectivity performance against other pesticides, such as thiamethoxam, fenamiphos, isoproturon, and atrazine. However, the platform presented cross-selectivity when detecting imidacloprid, carbendazim, and linuron, which is discussed herein. Overall, we present a promising platform for simple, on-site, and rapid colorimetric screening of specific pesticides, while highlighting the challenges of aptasensors in achieving selectivity amidst diverse molecular structures.

Cold Atmospheric Plasma-Assisted Direct Deposition of Polypyrrole-Ag Nanocomposites for Flexible Electronic Sensors.

Conductive polymers and their composite materials have attracted considerable interest due to their potential applications in sensors, actuators, drug delivery systems, and energy storage devices. Despite their wide range of applications, many challenges remain primarily with respect to the complex synthesis and time-consuming manufacturing steps that are often required in the fabrication process of various devices with conductive polymers. Here, we demonstrate the novel use of cold atmospheric plasma (CAP)-assisted deposition technologies as a solvent-free and scalable approach for in situ polymerization and direct deposition of conductive polypyrrole-silver (PPy-Ag) nanocomposites onto the desired substrates under atmospheric conditions. In this study, a systematic approach with different precursor composition mixtures containing pyrrole as the monomer and AgNO3 as the photoinitiator was investigated to assess the effect of precursor composition on the final chemical, electrical, and mechanical properties of the PPy-Ag nanocomposite thin-film coatings which were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and cyclic bending tests. The characterizations indicated the possibility of fabricating PPy-Ag nanocomposite films with tunable degrees of polymerization and Ag nanoparticle loading by simply varying the percentage of AgNO3 in precursor composition mixtures. Finally, as a proof of concept, the potential use of the PPy-Ag nanocomposite films with different Ag nanoparticle loading percentages was assessed for humidity sensing by measuring their level of change in electrical resistance in the relative humidity range of 12-60%. It is envisioned that the developed CAP-assisted deposition technology can provide a new stepping stone toward scalable additive manufacturing of various functional nanocomposite films for different low-cost and flexible electronic applications.

Simultaneous colorimetric and electrochemical detection of trace mercury (Hg2+) using a portable and miniaturized aptasensor.

We report a novel aptasensor for the simultaneous colorimetric and electrochemical detection of mercury (Hg2+). This device consists of a paper-based microfluidic component (µ-PAD) incorporated into a miniaturized three-electrode system fabricated through printed circuit board (PCB) technology. This biosensor is portable, rapid, versatile, and can detect Hg2+ down to 0.01 ppm based on 3σ of the blank/slope criteria. Moreover, it is highly selective against As2+, Cu2+, Zn2+, Pb2+, Cd2+, Mg2+, and Fe2+, reaching up to 13 times more of the input signal than the other heavy metals. The colorimetric detection mechanism uses aptamer functionalized polystyrene (PS)-AgNPs and Ps-AuNPs microparticles' specific aggregation. The Ps-AuNPs-based system allows qualitative detection (LOD 5 ppm) and stability over seven days (up to 97.59% signal retention). For the Ps-AgNPs-based system, the detection limit is 0.5 ppm with a linear range from 0.5 to 20 ppm (adjusted R2= 0.986) and stability over 30 days (up to 94.95% signal retention). The electrochemical component measures changes in charge transfer resistance upon target-aptamer hybridization using a [Ru (NH3)6]3+Cl3] redox probe. The latest component presents a linear range from 0.01 to 1 ppm (adjusted R2= 0.935) with a LOD of 0.01 ppm and performance stability over seven days (up to 102.52 ± 11.7 signal retention). This device offers a universal dual detection platform with multiplexing, multi-replication, quantitative color analysis, and minimization of false results. Furthermore, detection results in river samples showed recoveries up to 91.12% (RSD 0.85) and 105.61% (RSD 1.62) for the electrochemical and colorimetric components, respectively. The proposed system is highly selective with no false-positive or false-negative results in an overall wide linear range and can safeguard the accuracy of detection results in aptasensing platforms in general.

Smartphone-based colorimetric detection of cardiac troponin T via label-free aptasensing.

We report an aptasensing platform for the detection of cardiac troponin T (cTnT) in the immediate and early phases of acute myocardial infarction (AMI). High-flow filter paper was used to fabricate a microfluidic paper-based analytical device (µ-PAD), which was further modified with gold-decorated polystyrene microparticles functionalized with a highly specific cTnT aptamer. Herein, cTnT detection is presented in two linear ranges (0.01-0.8 µg/ml and 6.25-50 µg/ml) with an LoD of 3.9X10-4 µg/ml, which is in agreement with reference values determined by the American Heart Association. The proposed platform showed remarkable selectivity against AMI-associated cardiac biomarkers such as TNF-alpha, interleukin-6, cardiac troponin I, and reactive protein-C. This aptasensor is a label-free assay that relies only on smartphone-based image analysis and takes less processing time in comparison with traditional methods like ELISA. Furthermore, it exhibits outstanding stability over 23 days when devices are stored at 4 °C. The reported platform is a stable and cost-effective method for the on-site and user-friendly detection of cTnT in normal saline buffer and diluted human serum.

Noble-Nanoparticle-Decorated Ti3C2T x MXenes for Highly Sensitive Volatile Organic Compound Detection.

Two-dimensional transition-metal carbides and nitrides (MXenes) have been regarded as promising sensing materials because of their high surface-to-volume ratios and outstanding electronic, optical, and mechanical properties with versatile transition-metal and surface chemistries. However, weak gas-molecule adsorption of MXenes poses a serious limitation to their sensitivity and selectivity, particularly for trace amounts of volatile organic compounds (VOCs) at room temperature. To deal with these issues, Au-decorated MXenes are synthesized by a facile solution mixing method for room-temperature sensing of a wide variety of oxygen-based and hydrocarbon-based VOCs. Dynamic sensing experiments reveal that optimal decoration of Au nanoparticles (NPs) on Ti3C2T x MXene significantly elevates the response and selectivity of the flexible sensors, especially in detecting formaldehyde. Au-Ti3C2T x gas sensors exhibited an extremely low limit of detection of 92 ppb for formaldehyde at room temperature. Au-Ti3C2T x provides reliable gas response, low noise level, ultrahigh signal-to-noise ratio, high selectivity, as well as parts per billion level of formaldehyde detection. The prominent mechanism for Au-Ti3C2T x in sensing formaldehyde is elucidated theoretically from density functional theory simulations. The results presented here strongly suggest that decorating noble-metal NPs on MXenes is a feasible strategy for the development of next-generation ultrasensitive sensors for Internet of Things.

Microfluidic paper-based aptasensor devices for multiplexed detection of pathogenic bacteria.

Foodborne pathogens are major public health concerns worldwide. Paper-based microfluidic devices are versatile, user friendly and low cost. We report a novel paper-based single input channel microfluidic device that can detect more than one whole-cell foodborne bacteria at the same time, and comes with quantitative reading via image analysis. This microfluidic paper-based multiplexed aptasensor simultaneously detects E. coli O157:H7 and S. Typhimurium. Custom designed particles provide colorimetric signal enhancement and false results prevention. Several aptamers were screened and the highest-affinity aptamers were optimized and employed for detection of these bacteria in solution, both in a buffer as well as pear juice. Image analysis was used to read and quantify the colorimetric signal and measure bacteria concentration, thus rendering this paper based microfluidic device quantitative. The colorimetric results show linearity over a wide concentration range (102CFU/mL to 108CFU/mL) and a limit of detection (LOD) of 103CFU/mL and 102CFU/mL for E. coli O157:H7 and S. Typhimurium, respectively. An insignificant change in colorimetric response for non-target bacteria indicates the aptasesnors are specific. The reported multiplexed colorimetric paper-based microfluidic devices is likely to perform well for on-site rapid screening of pathogenic bacteria in water and food products.

DNA-Functionalized Ti3C2Tx MXenes for Selective and Rapid Detection of SARS-CoV-2 Nucleocapsid Gene.

Coronavirus disease 2019 (COVID-19) is an emerging human infectious disease caused by severe acute respiratory syndrome 2 (SARS-CoV-2, initially called novel coronavirus 2019-nCoV) virus. Thus, an accurate and specific diagnosis of COVID-19 is urgently needed for effective point-of-care detection and disease management. The reported promise of two-dimensional (2D) transition-metal carbides (Ti3C2Tx MXene) for biosensing owing to a very high surface area, high electrical conductivity, and hydrophilicity informed their selection for inclusion in functional electrodes for SARS-CoV-2 detection. Here, we demonstrate a new and facile functionalization strategy for Ti3C2Tx with probe DNA molecules through noncovalent adsorption, which eliminates expensive labeling steps and achieves sequence-specific recognition. The 2D Ti3C2Tx functionalized with complementary DNA probes shows a sensitive and selective detection of nucleocapsid (N) gene from SARS-CoV-2 through nucleic acid hybridization and chemoresistive transduction. The fabricated sensors are able to detect the SARS-CoV-2 N gene with sensitive and rapid response, a detection limit below 105 copies/mL in saliva, and high specificity when tested against SARS-CoV-1 and MERS. We hypothesize that the MXenes' interlayer spacing can serve as molecular sieving channels for hosting organic molecules and ions, which is a key advantage to their use in biomolecular sensing.

Optical Biosensors for Diagnostics of Infectious Viral Disease: A Recent Update.

The design and development of biosensors, analytical devices used to detect various analytes in different matrices, has emerged. Biosensors indicate a biorecognition element with a physicochemical analyzer or detector, i.e., a transducer. In the present scenario, various types of biosensors have been deployed in healthcare and clinical research, for instance, biosensors for blood glucose monitoring. Pathogenic microbes are contributing mediators of numerous infectious diseases that are becoming extremely serious worldwide. The recent outbreak of COVID-19 is one of the most recent examples of such communal and deadly diseases. In efforts to work towards the efficacious treatment of pathogenic viral contagions, a fast and precise detection method is of the utmost importance in biomedical and healthcare sectors for early diagnostics and timely countermeasures. Among various available sensor systems, optical biosensors offer easy-to-use, fast, portable, handy, multiplexed, direct, real-time, and inexpensive diagnosis with the added advantages of specificity and sensitivity. Many progressive concepts and extremely multidisciplinary approaches, including microelectronics, microelectromechanical systems (MEMSs), nanotechnologies, molecular biology, and biotechnology with chemistry, are used to operate optical biosensors. A portable and handheld optical biosensing device would provide fast and reliable results for the identification and quantitation of pathogenic virus particles in each sample. In the modern day, the integration of intelligent nanomaterials in the developed devices provides much more sensitive and highly advanced sensors that may produce the results in no time and eventually help clinicians and doctors enormously. This review accentuates the existing challenges engaged in converting laboratory research to real-world device applications and optical diagnostics methods for virus infections. The review's background and progress are expected to be insightful to the researchers in the sensor field and facilitate the design and fabrication of optical sensors for life-threatening viruses with broader applicability to any desired pathogens.

Roll-to-Roll Manufactured Sensors for Nitroaromatic Organophosphorus Pesticides Detection.

A fully roll-to-roll manufactured electrochemical sensor with high sensing and manufacturing reproducibility has been developed for the detection of nitroaromatic organophosphorus pesticides (NOPPs). This sensor is based on a flexible, screen-printed silver electrode modified with a graphene nanoplatelet (GNP) coating and a zirconia (ZrO2) coating. The combination of the metal oxide and the 2-D material provided advantageous electrocatalytic activity toward NOPPs. Manufacturing, scanning electron microscopy-scanning transmission electron microscopy image analysis, electrochemical surface characterization, and detection studies illustrated high sensitivity, selectivity, and stability (∼89% current signal retention after 30 days) of the platform. The enzymeless sensor enabled rapid response time (10 min) and noncomplex detection of NOPPs through voltammetry methods. Furthermore, the proposed platform was highly group-sensitive toward NOPPs (e.g., methyl parathion (MP) and fenitrothion) with a detection limit as low as 1 µM (0.2 ppm). The sensor exhibited a linear correlation between MP concentration and current response in a range from 1 µM (0.2 ppm) to 20 µM (4.2 ppm) and from 20 to 50 µM with an R2 of 0.992 and 0.991, respectively. Broadly, this work showcases the first application of GNPs/ZrO2 complex on flexible silver screen-printed electrodes fabricated by entirely roll-to-roll manufacturing for the detection of NOPPs.

Recent Advances in Aptamer-Based Biosensors for Global Health Applications.

Since aptamers were first reported in the early 2000s, research on their use for the detection of health-relevant analytical targets has exploded. This review article provides a brief overview of the most recent developments in the field of aptamer-based biosensors for global health applications. The review provides a description of general aptasensing principles and follows up with examples of recent reports of diagnostics-related applications. These applications include detection of proteins and small molecules, circulating cancer cells, whole-cell pathogens, extracellular vesicles, and tissue diagnostics. The review also discusses the main challenges that this growing technology faces in the quest of bringing these new devices from the laboratory to the market.

Antidelaminating, Thermally Stable, and Cost-Effective Flexible Kapton Platforms for Nitrate Sensors, Mercury Aptasensors, Protein Sensors, and p-Type Organic Thin-Film Transistors.

The inkjet printing of metal electrodes on polymer films is a desirable manufacturing process due to its simplicity but is limited by the lack of thermal stability and serious delaminating flaws in various aqueous and organic solutions. Kapton, adopted worldwide due to its superior thermal durability, allows the high-temperature sintering of nanoparticle-based metal inks. By carefully selecting inks (Ag and Au) and Kapton substrates (Kapton HN films with a thickness of 135 µm and a thermal resistance of up to 400 °C) with optimal printing parameters and simplified post-treatments (sintering), outstanding film integrity, thermal stability, and antidelaminating features were obtained in both aqueous and organic solutions without any pretreatment strategy (surface modification). These films were applied in four novel devices: a solid-state ion-selective (IS) nitrate (NO3-) sensor, a single-stranded DNA (ssDNA)-based mercury (Hg2+) aptasensor, a low-cost protein printed circuit board (PCB) sensor, and a long-lasting organic thin-film transistor (OTFT). The IS NO3- sensor displayed a linear sensitivity range between 10-4.5 and 10-1 M (r2 = 0.9912), with a limit of detection of 2 ppm for NO3-. The Hg2+ sensor exhibited a linear correlation (r2 = 0.8806) between the change in the transfer resistance (RCT) and the increasing concentration of Hg2+. The protein PCB sensor provided a label-free method for protein detection. Finally, the OTFT demonstrated stable performance, with mobility values in the linear (µlin) and saturation (µsat) regimes of 0.0083 ± 0.0026 and 0.0237 ± 0.0079 cm2 V-1 S-1, respectively, and a threshold voltage (Vth) of -6.75 ± 3.89 V.

Two C-terminal sequence variations determine differential neurotoxicity between human and mouse α-synuclein.

BACKGROUND: α-Synuclein (aSyn) aggregation is thought to play a central role in neurodegenerative disorders termed synucleinopathies, including Parkinson's disease (PD). Mouse aSyn contains a threonine residue at position 53 that mimics the human familial PD substitution A53T, yet in contrast to A53T patients, mice show no evidence of aSyn neuropathology even after aging. Here, we studied the neurotoxicity of human A53T, mouse aSyn, and various human-mouse chimeras in cellular and in vivo models, as well as their biochemical properties relevant to aSyn pathobiology. METHODS: Primary midbrain cultures transduced with aSyn-encoding adenoviruses were analyzed immunocytochemically to determine relative dopaminergic neuron viability. Brain sections prepared from rats injected intranigrally with aSyn-encoding adeno-associated viruses were analyzed immunohistochemically to determine nigral dopaminergic neuron viability and striatal dopaminergic terminal density. Recombinant aSyn variants were characterized in terms of fibrillization rates by measuring thioflavin T fluorescence, fibril morphologies via electron microscopy and atomic force microscopy, and protein-lipid interactions by monitoring membrane-induced aSyn aggregation and aSyn-mediated vesicle disruption. Statistical tests consisted of ANOVA followed by Tukey's multiple comparisons post hoc test and the Kruskal-Wallis test followed by a Dunn's multiple comparisons test or a two-tailed Mann-Whitney test. RESULTS: Mouse aSyn was less neurotoxic than human aSyn A53T in cell culture and in rat midbrain, and data obtained for the chimeric variants indicated that the human-to-mouse substitutions D121G and N122S were at least partially responsible for this decrease in neurotoxicity. Human aSyn A53T and a chimeric variant with the human residues D and N at positions 121 and 122 (respectively) showed a greater propensity to undergo membrane-induced aggregation and to elicit vesicle disruption. Differences in neurotoxicity among the human, mouse, and chimeric aSyn variants correlated weakly with differences in fibrillization rate or fibril morphology. CONCLUSIONS: Mouse aSyn is less neurotoxic than the human A53T variant as a result of inhibitory effects of two C-terminal amino acid substitutions on membrane-induced aSyn aggregation and aSyn-mediated vesicle permeabilization. Our findings highlight the importance of membrane-induced self-assembly in aSyn neurotoxicity and suggest that inhibiting this process by targeting the C-terminal domain could slow neurodegeneration in PD and other synucleinopathy disorders.

Surface Functionalization of Ti3C2Tx MXene with Highly Reliable Superhydrophobic Protection for Volatile Organic Compounds Sensing.

Two-dimensional (2D) transition-metal carbides (Ti3C2Tx MXene) have received a great deal of attention for potential use in gas sensing showing the highest sensitivity among 2D materials and good gas selectivity. However, one of the long-standing challenges of the MXenes is their poor stability against hydration and oxidation in a humid environment, limiting their long-term storage and applications. Integration of an effective protection layer with MXenes shows promise for overcoming this major drawback. Herein, we demonstrate a surface functionalization strategy for Ti3C2Tx with fluoroalkylsilane (FOTS) molecules through surface treatment, providing not only a superhydrophobic surface, mechanical/environmental stability but also enhanced sensing performance. The experimental results show that high sensitivity, good repeatability, long-term stability, and selectivity and faster response/recovery property were achieved by the FOTS-functionalized when Ti3C2Tx was integrated into chemoresistive sensors sensitive to oxygen-containing volatile organic compounds (ethanol, acetone). FOTS functionalization provided protection to sensing response when the dynamic response of the Ti3C2Tx-F sensor to 30 ppm of ethanol was measured over in the 5 to 80% relative humidity range. Density functional theory simulations suggested that the strong adsorption energy of ethanol on Ti3C2Tx-F and the local structure deformation induced by ethanol adsorption, contributing to the gas-sensing enhancement. This study offers a facile and practical solution for developing highly reliable MXene based gas-sensing devices with response that is stable in air and in the presence of water.

Sulfur-Doped Titanium Carbide MXenes for Room-Temperature Gas Sensing.

Two-dimensional titanium carbide MXenes, Ti3C2Tx, possess high surface area coupled with metallic conductivity and potential for functionalization. These properties make them especially attractive for the highly sensitive room-temperature electrochemical detection of gas analytes. However, these extraordinary materials have not been thoroughly investigated for the detection of volatile organic compounds (VOCs), many of which hold high relevance for disease diagnostics and environmental protection. Furthermore, the insufficient interlayer spacing between MXene nanoflakes could limit their applicability and the use of heteroatoms as dopants could help overcome this challenge. Here, we report that S-doping of Ti3C2Tx MXene leads to a greater gas-sensing performance to VOCs compared to their undoped counterparts, with unique selectivity to toluene. After S-doped and pristine materials were synthesized, characterized, and used as electrode materials, the as-fabricated sensors were subjected to room-temperature dynamic impedimetric testing in the presence of VOCs with different functional groups (ethanol, hexane, toluene, and hexyl-acetate). Unique selectivity to toluene was obtained by both undoped and doped Ti3C2Tx MXenes, but an enhancement of response in the range of ∼214% at 1 ppm to ∼312% at 50 ppm (3-4 folds increase) was obtained for the sulfur-doped sensing material. A clear notable response to 500 ppb toluene was also obtained with sulfur-doped Ti3C2Tx MXene sensors along with excellent long-term stability. Our experimental measurements and density functional theory analysis offer insight into the mechanisms through which S-doping influences VOC analyte sensing capabilities of Ti3C2Tx MXenes, thus opening up future investigations on the development of high-performance room-temperature gas sensors.

Ionic Strength Influences on Biofunctional Au-Decorated Microparticles for Enhanced Performance in Multiplexed Colorimetric Sensors.

The rising development of biosensors offers a great potential for health, food, and environmental monitoring. However, in many colorimetric platforms, there is a performance limitation stemming from the tendency of traditional Au nanoparticles toward nonspecific aggregation in response to changing ionic strength (salt concentration). This work puts forward a new type of colorimetric aptamer-functionalized labeling of microparticles, which allows to leverage an increase in ionic strength as a positive driver of enhanced detection performance of analytical targets. The resulting device is a cost-effective, instrument-free, portable, and reliable aptasensor that serves as basis for the fabrication of universal paper-based colorimetric platforms with the capability of multiplex, multireplicates and provides quantitative colorimetric detection. A controlled fabrication process was demonstrated by keeping 90% of the signal obtained from the as-fabricated devices (n = 40) within ± 1 standard deviation (SD) (relative SD = 5.69%) and following a mesokurtic normal-like distribution (p = 0.385). We propose for the first time a salt-induced aggregation mechanism for highly stable multilayered label particles (ssDNA-PEI-Au-PS) as the basis of the detection scheme. The use of DNA aptamers as capture biomolecules and PEI as an encapsulating agent allows for a sensitive and highly specific colorimetric response. As a proof of concept, multiplexed detection of mercury (Hg2+) and arsenic (As3+) was demonstrated. In addition, we introduced a robust image analysis algorithm for testing zone segmentation and color signal quantification that allowed for analytical detection, reaching a limit of detection of 1 ppm for both targeted analytes, with enough evidence (p > 0.05) to prove the high specificity of the fabricated device versus a pool of possible interferent ions.

Selective Detection of Ethylene by MoS2-Carbon Nanotube Networks Coated with Cu(I)-Pincer Complexes.

The plant hormone ethylene (C2) can induce premature fruit ripening and flower senescence at levels below 1 ppm, which has motivated efforts to develop cost-effective methods for C2 monitoring during the transport and storage of climacteric fruits. Here, we describe a nanocomposite film composed of exfoliated MoS2, single-walled carbon nanotubes (SCNTs), and Cu(I)-tris(mercaptoimidazolyl)borate complexes (Cu-Tm) for real-time detection of C2 at levels down to 100 ppb. A copercolation network of MoS2 and SCNTs was deposited onto interdigitated Ag electrodes printed on plastic substrates and then coated with Cu-Tm with a final conductance in the 0.5 mS range. Reversible changes in relative conductance (-ΔG/G0) were measured upon C2 exposure with a linear response at sub-ppm levels. The thin-film sensors were highly selective toward C2, and they responded weakly to other volatile organic compounds or water at similar partial pressures. A mechanism is proposed in which Cu-Tm behaves as a chemically sensitive n-type dopant for MoS2, based on spectroscopic characterization and density functional theory modeling. Cu-Tm-coated MoS2/SCNT sensors were also connected to a battery-powered wireless transmitter and used to monitor C2 production from various fruit samples, validating their utility as practical, field-deployable sensors.

Nanohybrids of a MXene and transition metal dichalcogenide for selective detection of volatile organic compounds.

Two-dimensional transition metal carbides/nitrides, known as MXenes, have been recently receiving attention for gas sensing. However, studies on hybridization of MXenes and 2D transition metal dichalcogenides as gas-sensing materials are relatively rare at this time. Herein, Ti3C2Tx and WSe2 are selected as model materials for hybridization and implemented toward detection of various volatile organic compounds. The Ti3C2Tx/WSe2 hybrid sensor exhibits low noise level, ultrafast response/recovery times, and good flexibility for various volatile organic compounds. The sensitivity of the hybrid sensor to ethanol is improved by over 12-fold in comparison with pristine Ti3C2Tx. Moreover, the hybridization process provides an effective strategy against MXene oxidation by restricting the interaction of water molecules from the edges of Ti3C2Tx. An enhancement mechanism for Ti3C2Tx/WSe2 heterostructured materials is proposed for highly sensitive and selective detection of oxygen-containing volatile organic compounds. The scientific findings of this work could guide future exploration of next-generation field-deployable sensors.

Collagen Coating Effects on Fe-Mn Bioresorbable Alloys.

Bioresorbable iron-manganese alloys (Fe-30%Mn) are considered as one of the next-generation resorbable materials for orthopedic applications. Previous in vitro study showed that Fe30Mn scaffolds with 10% porosity displayed strong mechanical properties and adequate degradation rate without severe cytotoxicity effect. However, the cellular compatibility of these alloys in terms of cell-to-cell and alloy-to-cell interactions is not ideal. Collagen is the most abundant protein in human bone, providing structural support beneficial to bone healing. We hypothesized that coating collagen on Fe30Mn can improve osteointegration or activities promoting cell adhesion, migration, and proliferation, as the alloy degrades. After preparing collagen coating on Fe-30Mn via spin coating, we conducted a corrosion test and a direct cytotoxicity test on four Fe30Mn groups: non-porous and 10% porosity, with and without collagen coating. Furthermore, we evaluated and compared the morphologies of cells over a period of 7 days. Results showed that there was no significant difference between the collagen-coated and non-coated groups in corrosion rates, yet a significant decrease from the porous non-coated group to the porous collagen-coated group in cytotoxicity level was found. Cell morphology on the porous non-coated group displayed round shape, whereas that on the porous collagen-coated group displayed flattened spreading. The study showed that the collagen coating significantly increased the initial cell viability and adhesion for both the porous and non-porous groups without impeding their degradation rates. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:523-535, 2020.

Competitive heavy metal adsorption onto new and aged polyethylene under various drinking water conditions.

The study goal was to identify factors that influence copper (Cu), iron (Fe), lead (Pb), manganese (Mn), and zinc (Zn) loading on new and aged low-density polyethylene (LDPE) under various drinking water conditions. The applied aging procedure increased LDPE surface area, hydrophilicity and the number of oxygen containing functional groups. Aged LDPE adsorbed up to a 5 fold greater metals than the new LDPE: Cu > Pb, Zn > Mn. Water pH (5.5 to 10.5) significantly altered LDPE surface metal loading. The organic carbon leached from plastic pipes inhibited Cu adsorption (-43.8%), but other metals were less impacted (-5.7% to -9.1%). The addition of free chlorine and corrosion inhibitor retarded metal adsorption to suspended LDPE materials. Overall, by changing water conditions total metal loadings (i.e., Cu, Mn, Pb and Zn) were altered 20.1 to 35.4%. When Fe was present, Cu (-4.0%) and Pb (-4.5%) loadings were reduced, while lesser impacts were found for Mn and Zn. Cu2+, Pb2+ and Zn2+ hydroxides and oxides were identified as the major metal deposit forms on the LDPE surface by XPS. To better predict metal fate in plastic piping systems, plastic surface characteristics, dissolved organics, water pH, hydraulic conditions and microbial growth should be considered.

Versatile printed microheaters to enable low-power thermal control in paper diagnostics.

As the capabilities of low-resource field testing have begun to expand to incorporate more complex diagnostic technologies, many of these devices remain tethered to large heaters requiring relatively high-power inputs. Highly efficient microheaters would enable miniaturization of devices for more economic and effective heating with high temperatures and sustained incubation. This work reports the development and application of resistive microheaters printed with nanosilver ink for improved methods of automated sample heating in paper-based point-of-care (POC) and in-field diagnostics. Resistance is easily predicted, and shapes can be altered to fit space and heat-transfer needs, sustained and discrete heating of precise regions are possible. Here, we demonstrate both isothermal nucleic acid amplification at 65 °C and bacterial culture at 37 °C using our microheaters. Printed nanosilver microheaters are easily integrated into reactions that require low-power battery heating, can sustain heating for 16-hour incubations, and cost between 0.17 and 0.58 US dollars each. Further, the microheaters are reusable, stable over 6 months, and can be wetted without degradation or reduction in conductivity. These versatile printed microheaters enable thermal control for a variety of low power heating applications.