Disposable Peptidoglycan-Specific Biosensor for Noninvasive Real-Time Detection of Broad-Spectrum Gram-Positive Bacteria in Exhaled Breath Condensates.

Rapidly identifying and quantifying Gram-positive bacteria are crucial to diagnosing and treating bacterial lower respiratory tract infections (LRTIs). This work presents a field-deployable biosensor for detecting Gram-positive bacteria from exhaled breath condensates (EBCs) based on peptidoglycan recognition using an aptamer. Dielectrophoretic force is employed to enrich the bacteria in 10 s without additional equipment or steps. Concurrently, the measurement of the sensor's interfacial capacitance is coupled to quantify the bacteria during the enrichment process. By incorporation of a semiconductor condenser, the whole detection process, including EBC collection, takes about 3 min. This biosensor has a detection limit of 10 CFU/mL, a linear range of up to 105 CFU/mL and a selectivity of 1479:1. It is cost-effective and disposable due to its low cost. The sensor provides a nonstaining, culture-free and PCR-independent solution for noninvasive and real-time diagnosis of Gram-positive bacterial LRTIs.

Facile Synthesis of Iron Carbide via Pyrolysis of Ferrous Fumarate for Catalytic CO2 Hydrogenation to Lower Olefins.

Hydrogenation of CO2 to olefin catalyzed by iron-based catalysts is a sustainable and important way to achieve carbon neutrality. In this study, iron-based catalysts were facilely prepared by direct pyrolysis of ferric fumarate (FF), which are applied to CO2 hydrogenation to olefin reaction to explore the effects of pyrolysis temperature and atmosphere on catalytic performance of the catalysts. Among them, NaFe-Air-400 catalyst exhibits the highest catalytic activity with 33.7 %, and light olefin selectivity reaches as high as 47.1 %. The catalytic performance of pyrolytic catalysts is better than that the impregnated NaFe catalyst on activated carbon (NaFe/AC). A series of XRD, Raman and SEM characterization results show a suitable pyrolysis temperature would promote the balance between amorphous carbon and graphene, which can affect the formation of FexCy phase, leading the distinctive activity and olefin selectivity. Hence, the presented one-step pyrolysis methodology would provide a facile and quick synthesis of highly-active iron-based catalyst design for CO2 conversion.

One-step and real-time detection of Hg2+ in brown rice flour using a biosensor integrated with AC electrothermal enrichment.

Mercury (Hg2+) is one of the most toxic heavy metals in farm products, so rapid detection of trace Hg2+ has always been sought after with high interest. Herein, we report a biosensor to specifically recognize Hg2+ in leaching solutions of brown rice flour. This sensor is simple and of low cost, with a very short assay time of 30 s. Another merit is the ultra-low limit of detection (LOD) at fM level. In addition, the specific aptamer probe realizes a good selectivity above 105: 1 against the interferences. This sensor is developed based on an aptamer-modified gold electrode array (GEA) for capacitive sensing. Alternating current electrothermal (ACET) enrichment is induced during the AC capacitance acquirement. Thus, the enrichment and detection are coupled as a single step, and pre-concentration is needless. Owing to the sensing mechanism of solid-liquid interfacial capacitance and ACET enrichment, Hg2+ level can be sensitively and rapidly reflected. Also, the sensor has a wide linear range from 1 fM to 0.1 nM and a shelf life of 15 days. This biosensor shows advantages on overall performance, enabling easy-to-operate, real-time, and large-scale Hg2+ detection in farm products.

Capacitive Aptasensor Coupled with Microfluidic Enrichment for Real-Time Detection of Trace SARS-CoV-2 Nucleocapsid Protein.

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has lasted for almost 2 years. Stemming its spread has posed severe challenges for clinical virus detection. A long turnaround time, complicated operation, and low accuracy have become bottlenecks in developing detection techniques. Adopting a direct antigen detection strategy, we developed a fast-responding and quantitative capacitive aptasensor for ultratrace nucleocapsid protein detection based on a low-cost microelectrode array (MEA) chip. Employing the solid-liquid interface capacitance with a sensitivity of picofarad level, the tiny change on the MEA surface can be definitively detected. As a result, the limit of detection reaches an ultralow level of femtogram per milliliter in different matrices. Integrated with efficient microfluidic enrichment, the response time of this sensor from the sample to the result is shortened to 15 s, completely meeting the real-time detection demand. Moreover, the wide linear range of the sensor is from 10-5 to 10-2 ng/mL, and a high selectivity of 6369:1 is achieved. After application and evaluation in different environmental and body fluid matrices, this sensor and the detection method have proved to be a label-free, real-time, easy-to-operate, and specific strategy for SARS-CoV-2 screening and diagnosis.

A disposable aptasensor based on a gold-plated coplanar electrode array for on-site and real-time determination of Cu2.

Copper ion (Cu2+) is an important cofactor for many enzymes in human body. Either excessive or deficient Cu2+ in the body may cause serious dysfunctions and diseases. So sensitive determination of Cu2+ in environmental samples is of more significance for evaluation and control of Cu2+ intake. Based on a low-cost gold-plated coplanar electrode array, a disposable aptasensor is developed with an ultra-sensitive indicator of interfacial capacitance. Modified with a specially isolated DNA aptamer for Cu2+, this sensor achieves a high selectivity of 1207: 1 against non-target ions. To realize real-time response, alternating-current electrothermal effect is integrated into the capacitance measuring process to efficiently enrich the trace Cu2+. This sensor reaches a limit of detection of 2.97 fM, with a linear range from 5.0 fM to 50 pM. The response time is only 15 s, which can meet the real-time detection requirement. On-site test of practical samples is also realized using the disposable sensor combined with a handheld inductance/capacitance/resistance meter. This sensor with its portable test system provides a cost-efficient solution for on-site, real-time and sensitive detection of Cu2+, showing great application value in environment monitoring.

Real-time, selective, and low-cost detection of trace level SARS-CoV-2 spike-protein for cold-chain food quarantine.

Due to the friendly temperature for virus survival, SARS-CoV-2 is frequently found in cold-chain foods, posing a serious threat to public health. Utilizing an interdigitated microelectrode chip modified with an antibody probe and integrating dielectrophoresis enrichment with interfacial capacitance sensing, a strategy is presented for the detection of trace level spike-protein from SARS-CoV-2. It achieves a limit of detection as low as 2.29 × 10-6 ng/mL in 20 s, with a wide linear range of 10-5-10-1 ng/mL and a selectivity of 234:1. The cost for a single test can be controlled to ~1 dollar. This strategy provides a competitive solution for real-time, sensitive, selective, and large-scale application in cold-chain food quarantine.

An on-site, highly specific immunosensor for Escherichia coli detection in field milk samples from mastitis-affected dairy cattle.

Bovine mastitis is the most economically important infectious disease in dairy industry, and Escherichia coli (E. coli) is one of the major causative pathogens. Rapid identification and quantitative detection of E. coli are of great importance for bovine mastitis control and milk quality monitoring. Capitalizing on dielectrophoresis and interphase capacitance sensing, we have developed an immunosensor for E. coli detection by modifying low cost commercial microelectrodes with an E. coli specific antibody. The limit of detection reaches as low as 775 cells/mL within a 15 s' response time, which can satisfy the requirement for on-site detection and field diagnosis of bovine mastitis. To demonstrate the sensor's specificity, tests against Staphylococcus aureus and Streptococcus uberis samples are performed showing negligible responses, and the selectivity is calculated to be 3063: 1. Furthermore, a simple pretreatment protocol is developed for on-site testing of raw milk, which only involves incubation, centrifugation and dilution steps. Then correct detection of E. coli is demonstrated for both artificially inoculated and infected field milk samples. This immunosensor and the corresponding protocol have advantages in speed, sensitivity, specificity, operability, and low cost, which make it highly promising for on-site pathogen detection of bovine mastitis.

An interdigitated microelectrode based aptasensor for real-time and ultratrace detection of four organophosphorus pesticides.

With increasing industrialization of food production, residues of organophosphorus pesticides (OPs) are more frequently found in the environment including rivers, lakes and soils. Extended exposure to OPs, even at a level below 1 nM, may lead to liver and central nervous system damages in humans and animals, while existing detection methods are not sensitive enough to detect OPs at trace levels. We presented a simple-to-use aptasensor to rapidly detect broad-spectrum OPs with high sensitivity. DNA aptamer was modified on the surface of a micro interdigitated electrode chip, and AC electrokinetics was employed to accelerate the binding of OP molecules to the aptamer probe. The sensing strategy directly measured the interfacial capacitance whose change rate was adopted as a quantitative indicator of recognition events, with a sample to result detection time of 30 s. This aptasensor had a wide linear range of (fM ~ nM), and the detection limit reached (0.24-1.67) fM for four highly-toxic OPs, with good specificity. It still showed good activity after being stored in non-refrigerated environment for at least 14 days. This aptasensor as well as the detection method offer a promising solution for on-site and real-time sensitive OP detection.

Rapid detection of trace Cu2+ using an l-cysteine based interdigitated electrode sensor integrated with AC electrokinetic enrichment.

Copper is an indispensable trace element for human health. Too much or too little intake of copper ion (Cu2+ ) can lead to its own adverse health conditions. Therefore, detection of Cu2+ is always of vital importance. In this work, a simple sensor was developed for rapid detection of trace Cu2+ in water, in which L-cysteine (Cys) as a molecular probe was self-assembled on a gold interdigital electrode to form a monolayer for specific capture of Cu2+ . The interfacial capacitance of interdigital electrode was detected to indicate the target adsorption level under an AC signal working as the excitation to induce directed movement and enrichment of Cu2+ to the electrode surface. This sensor reached a limit of detection of 4.14 fM and a satisfactory selectivity against eight other ions (Zn2+ , Hg2+ , Pb2+ , Cd2+ , Mg2+ , Fe2+ , As3+ , and As5+ ). Testing of spiked tap water was also performed, demonstrating the sensor's usability. This sensor as well as the detection method shows a great application potential in fields such as environmental monitoring and medical diagnosis.

Gray matter volume abnormalities in depressive patients with and without anxiety disorders.

Comorbidity with anxiety disorder is a relatively common occurrence in major depressive disorder. However, the unique and shared neuroanatomical characteristics of depression and anxiety disorders have not been fully identified. The aim of this study was to identify gray matter abnormalities and their clinical correlates in depressive patients with and without anxiety disorders. We applied voxel-based morphometry and region-of-interest analyses of gray matter volume (GMV) in normal controls (NC group, n = 28), depressive patients without anxiety disorder (DP group, n = 18), and depressive patients with anxiety disorder (DPA group, n = 20). The correlations between regional GMV and clinical data were analyzed. The DP group showed decreased GMV in the left insula (INS) and left triangular part of the inferior frontal gyrus when compared to the NC group. The DPA group showed greater GMV in the midbrain, medial prefrontal cortex, and primary motor/somatosensory cortex when compared to the NC group. Moreover, the DPA group showed greater GMV than the DP group in the frontal, INS, and temporal lobes. Most gray matter anomalies were significantly correlated with depression severity or anxiety symptoms. These correlations were categorized into 4 trend models, of which 3 trend models (ie, Models I, II, and IV) revealed the direction of the correlation between regional GMV and depression severity to be the opposite of that between regional GMV and anxiety symptoms. Importantly, the left INS showed a trend Model I, which might be critically important for distinguishing depressive patients with and without anxiety disorder. Our findings of gray matter abnormalities, their correlations with clinical data, and the trend models showing opposite direction may reflect disorder-specific symptom characteristics and help explain the neurobiological differences between depression and anxiety disorder.

Increased suicide attempts in young depressed patients with abnormal temporal-parietal-limbic gray matter volume.

BACKGROUND: Suicide is a major cause of death throughout the world. Approximately 60% of all suicides have a history of depression. Previous studies of structural brain imaging have shown that suicide is often associated with abnormal fronto-limbic networks. However, the mechanism underlying suicide in depression remains poorly understood. METHOD: Twenty sex- and age-matched suicidal unipolar patients were compared with 18 non-suicidal unipolar patients and 28 healthy controls. High-resolution T1-weighted 3T magnetic resonance imaging (MRI) scans were acquired. Hamilton Depressive Rating Scale (HAMD) and Self-Rating Depression scale (SDS) were evaluated. The criterion for suicidality was one or more documented lifetime suicide attempts. A whole-brain optimized voxel-based morphometry (VBM) approach was applied. The Dysfunctional Attitude Scale (DAS) was used to measure cognitive scheme in depressive patients. RESULTS: Compared with controls, patients without suicide history showed significant decreased gray matter volume in the left insula lobe [-35 18 9], whereas patients with suicide history showed significantly decreased gray matter volume in the right middle temporal gyrus [60 -53 -8] and increased gray matter volume in the right parietal lobe [39 -39 60]. Compared with the non-suicidal depressed patient group, the suicidal group showed significant decreased gray matter volume in left limbic cingulated gyrus [-2 -21 28]. Moreover, the gray matter volume values in this significantly different brain region were negatively correlated with dysfunctional attitude scores in suicidal depressed patients. LIMITATIONS: This study needs replication and further clarification in a larger patient population. CONCLUSIONS: Suicide attempts in young depressed patients may be related to abnormal gray matter volumes in temporal-parietal-limbic networks. Specifically, small left limbic cingulate gyrus volumes may be a candidate for the prediction of suicide in young depressed patients.

A longitudinal study of structural brain network changes with normal aging.

The aim of this study was to investigate age-related changes in the topological organization of structural brain networks by applying a longitudinal design over 6 years. Structural brain networks were derived from measurements of regional gray matter volume and were constructed in age-specific groups from baseline and follow-up scans. The structural brain networks showed economical small-world properties, providing high global and local efficiency for parallel information processing at low connection costs. In the analysis of the global network properties, the local and global efficiency of the baseline scan were significantly lower compared to the follow-up scan. Moreover, the annual rate of change in local and global efficiency showed a positive and negative quadratic correlation with the baseline age, respectively; both curvilinear correlations peaked at approximately the age of 50. In the analysis of the regional nodal properties, significant negative correlations between the annual rate of change in nodal strength and the baseline age were found in the brain regions primarily involved in the visual and motor/control systems, whereas significant positive quadratic correlations were found in the brain regions predominately associated with the default-mode, attention, and memory systems. The results of the longitudinal study are consistent with the findings of our previous cross-sectional study: the structural brain networks develop into a fast distribution from young to middle age (approximately 50 years old) and eventually became a fast localization in the old age. Our findings elucidate the network topology of structural brain networks and its longitudinal changes, thus enhancing the understanding of the underlying physiology of normal aging in the human brain.