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.

Lab in a Tube: Point-of-Care Detection of Escherichia coli.

Significant levels of infectious diseases caused by pathogenic bacteria are nowadays a worldwide matter, carrying considerable public health care challenges and huge economic concerns. Because of the rapid transmission of these biothreat agents and the outbreak of diseases, a rapid detection of pathogens in early stages is crucial, particularly in low-resources settings. To this aim, we developed for the first time a new sensing approach carried out in a single step for Escherichia coli O157:H7 detection. The detection principle is based on Förster resonance energy transfer using gold nanoclusters as a signal reporter and gold nanoparticles conjugated with antibodies as a quencher. The sensing platform includes an ultraviolet-light-emitting diode to provide the proper excitation and consists of a microtube containing two pieces of fiber glass; one of them is embedded with label-free gold nanoclusters and the other one with gold nanoparticles conjugated with antibodies. Upon the addition of the sample containing bacteria, the florescence of gold nanoclusters is recovered. The assay was evaluated by the naked eye (on/off) and quantitatively with use of a smartphone camera. The biosensor proved to be highly specific and sensitive, achieving a limit of detection as low as 4.0 cfu mL-1. Additionally, recoveries of 110% and 95% were obtained when the platforms in spiked river and tap water, respectively, were evaluated.

Recent Advances of Optical Biosensors in Veterinary Medicine: Moving Towards the Point of Care Applications.

While food safety issues are attracting public concern due to their detrimental effects on human health, monitoring livestock health is urgently needed to diagnose animal diseases at an early stage by applying proper treatments, controlling, and preventing outbreaks, particularly in resource- limited countries. In addition, unhealthy farms are not only a threat to livestock but also to human lives. The available diagnostic techniques for the detection of key health threats within both the food and livestock sectors require labor-intensive and time-consuming experimental procedures and sophisticated and expensive instruments. To tackle this issue, optical biosensing strategies have been incorporated into point-of-care (POC) systems, offering real-time monitoring, field-deployable, and low-cost devices, which help make on-the-spot decisions. This review aims to discuss the recent cutting-edge research on POC optical biosensing platforms for on-farm diagnosis of animal diseases and on-site detection of animal-derived food-borne contaminants, including pathogens, antibiotics, and mycotoxins. Moreover, this review briefly presents the basic knowledge of various types of optical biosensors and their development using various recent strategies, including nanomaterial combinations, to enhance their performance in POC tests. This review is expected to help scientists to understand the evolution and challenges in the development of point-of-care biosensors for the food and livestock industry, benefiting global healthcare.

In Vitro Cytotoxicity and Apoptosis Inducing Evaluation of Novel Halogenated Isatin Derivatives.

BACKGROUND: Isatin (1H-indole-2,3-dione) and its derivatives have been utilized in a variety of biological activities. Anticancer compounds were the most extensively highlighted and explored among the range of beneficial properties. OBJECTIVE: Herein, we report the targeting effect of halogenated isatin derivatives on cancer cell mitochondria and their antiproliferative mechanism. METHODS: A series of novel 5-halo-Isatin derivatives consisting of the 5-Amino-1,3,4-thiadiazole-2-thiol scaffold were synthesized and easily conducted in good yields through a condensation reaction between keto groups of Isatin and primary amine under alcoholic conditions, followed by S-benzylation. The compounds were fully characterized using spectroscopic methods such as 1H-NMR, FTIR, mass spectroscopy and then tested in vitro towards three cancer cell lines HT-29 (colon cancer), MCF-7 (breast cancer), and SKNMC (neuroblastoma). Apoptosis induction was investigated through assessment of caspase 3 and mitochondrial membrane potential. RESULTS: The most potent compounds of 5b, 5r (IC50 = 18,13 µM), and 5n (IC50 = 20,17 µM) were found to show strong anticancer activity, especially for MCF7 cells. Further anticancer mechanism studies indicated that 5b and 5r induced apoptosis through the intrinsic mitochondrial pathway. CONCLUSION: This research demonstrated that 5b and 5r have an anticancer property via the modulation of oxidative stress-mediated mitochondrial apoptosis and immune response, which deserves further studies on their clinical applications.

Flexible electrospun nanofibrous film integrated with fluorescent carbon dots for smartphone-based detection and cellular imaging application.

The dose of administered chemotherapy drugs is crucial to determine due to the potential for efficient or adverse outcomes for cancer patients. To date, no user-friendly and low-cost method of doxorubicin (DOX) detection using nontoxic and biodegradable materials has been reported. For this reason, in this work, we have developed for the first time a nanofiber-based sensing platform for sensitive and on-site DOX assay in just 10 min. This is obtained thanks to printable, porosity and embeddability features of electrospun nanofibrous films (ENFFs) combined with nitrogen and sulfur co-doped carbon dots (NS-CDs) as sensing probes. The assay was done by just pipetting analyte on the hydrophilic spots of the fabricated photoluminescence water-stable ENFFs where the color intensity was being darkened. DOX quenched NS-CDs fluorescence onto ENFFs through inner filter effect. The developed sensor was either coupled with smartphone technology to provide miniaturized, portable and easy-to-use device or an ordinary spectrofluorimeter for solid-state sensing applications (detection limit of 5.4 nM). Moreover, applicability of the designed sensor was evaluated in human serum with satisfactory recoveries. It is more interesting that the fabricated NS-CDs/ENF scaffolds have a high potential to detect the intracellular DOX to enhance cell proliferation leading to be considered as a multimodal tool in biomedical research and clinical diagnostics.

Ratiometric bioassay and visualization of dopamine ß-hydroxylase in brain cells utilizing a nanohybrid fluorescence probe.

Dopamine ß-hydroxylase (DBH) is involved in various neuronal transmission processes in the brain. Due to the severe diseases caused by abnormity levels of such important enzyme in human serum, sensitive and rapid detection of DBH at early stages is crucial, particularly for clinical analysis. Herein, we developed optical sensors for DBH that include the following: (i) a ratiometric fluorescence sensor that hybridizes the bovine serum albumin (BSA)-gold nanoclusters (BSA-AuNCs) and nitrogen doped carbon dots (N-CDs). The sensor proved to be highly selective and sensitive, achieving a linear range of 0.02-0.16 µg mL-1 and a limit of detection of 4.0 ng mL-1. In the presence of DBH, the fluorescence intensity of BSA-AuNCs (λem = 615 nm) was remarkably quenched by DBH serving as a reporter signal, whereas the N-CDs fluorescence intensity at 440 nm was almost kept unchanged serving as a reference signal. The developed ratiometric sensor is capable of demonstrating a color change from pink to violet and blue with a gradual increase in DBH concentration, which is discernible by the naked-eye. A test strip is prepared for semi-quantitative assay and convenient use. Intriguingly, by taking advantage of the inter-AuNCs aggregation in the presence of DBH, (ii) a resonance light scattering (RLS) sensor was also developed based on the nanohybrid probe (detection limit 95 ng mL-1). Fluorescence imaging in PC12 cell lines demonstrated that the BSA-AuNCs could be utilized in visualization assay towards intracellular DBH. Additionally, the sensors were tested in a real matrix by spiking serum samples with satisfactory recoveries.

Green and cost-effective synthesis of carbon dots from date kernel and their application as a novel switchable fluorescence probe for sensitive assay of Zoledronic acid drug in human serum and cellular imaging.

A new label-free, sensitive and selective off and on signaling fluorescence platform for assay of trace levels of Zoledronic acid (ZA) drug in human biological samples based on nitrogen doped carbon dots (N-CDs) - ferric ions (Fe3+) was designed. The fluorescence probe, N-CDs, was synthesized for the first time through a facile, eco-friendly and one-step hydrothermal treatment using date kernel as the precursor without any need to use chemical reagents. These CDs exhibited excellent water solubility, ionic and photo stability in various circumstances and a highly relative quantum yield of 12.5%. In the presence of Fe3+, the fluorescence intensity (FL) for N-CDs was strongly quenched due to the interaction between ferric ions and the functional groups at the N-CDs (switch off). Afterwards, by the addition of ZA, the fluorescence sensor status turned to "ON" (switch on) due to the dominance of ZA in the competition between functional groups on the surface of N-CDs and phosphate groups in ZA in the interaction with Fe3+ results in removing Fe3+ from the surface of N-CDs. Under the optimized conditions, the proposed fluorescence probe (N-CDs-Fe3+) exhibited good sensing performance for ZA assay with a linearity from 0.1 µM to 10.0 µM, a detection limit of 0.04 µM and the precision of 2.70%. The developed N-CDs-Fe3+ sensor was successfully used for the assay of ZA contents with good recoveries and selectivity in human serum samples. Meanwhile, the in vitro cytotoxic activity and cellular uptake of N-CDs were investigated on human osteosarcoma (MG-63) cell line.