Biosensors & Bioelectronics

In this study, anti-Salmonella polyclonal antibodies immobilized on cellulose nitrate membrane were used to capture Salmonella pullorum (S. pullorum) in biological samples. The rapid evaluation of S. pullorum contamination was based on the analysis of the activities of catalase, a biomarker of this bacterium. After a screen printed electrode (SPE) modified with multi-wall carbon nanotubes (MWCN)-chitosan-peroxidase was connected to a portable selfmade amperometric sensor, the determination of S. pullorum contamination was carried out by adding the reaction product, which was obtained from the hydrogen peroxide dismutation catalyzed by the bacterial catalase, to the reacting area of the SPEs. A working potential of 0.55 V was applied in the sensing system and the current value displayed on the amperometric sensor was used as the detection signal. This method allowed the quantification of S. pullorum with the detection limit of 100cfu mL-1 in culture media and chicken samples. The stability, reproducibility and sensitivity of the modified SPE were also investigated. Moreover, successive analysis was conveniently accomplished by replacing the one-off SPE. This portable sensing system is a rapid, cost-effective and straightforward approach for screening S. pullorum contamination in food samples.

Non-invasive and high sensitive electrochemical impedance spectroscopy (EIS) has been used for qualitative characterization of stepwise surface preparation process for constructing an immunosensor, starting from plain silicon substrate, 3-aminopropyltriethoxysilane (APTES) silanization, glutaraldehyde functionalization and analytes (rat immunoglobulin G immobilization, followed by protein G-coated gold nanoparticles), using both the horizontal direction (2 terminal) and vertical direction (3 terminal) characterization setup. The investigation demonstrated that 2-terminal setup is able to review the quality of antibody and antigen molecules bonding and distinguish the effects from the underlayers on the immuosensors; while 3-terminal setup is able to correlate the thickness and dielectric constant of each layers. It correlated well to the incubation time of preparing different sensors as well. The two different EIS measurement setups are able to serve different needs for immunosensor characterization and EIS measurement shows higher sensitivities compared with UV-Vis absorption measurement.

Measurements of parameters of hemostasis like thromboplastine time (PT) have primary significance in many clinical settings including extensive surgery, dialysis or innate disorders of hemostasis. Recently, several reports have documented the principle suitability of Quartz Crystal Microbalances (QCM) for measuring parameters of hemostasis like PT or platelet aggregation. But for the establishment of an exact QCM based method as alternative to standard coagulometer measuring QCM coatings with significantly enhanced robustness and reusability have to be worked out. For this purpose we utilized a new semi-automated equipment qCell T for measuring and compared different coatings consisting of polymer films and absorbed nanoparticles (NPs). We demonstrated that affinity based poly ethylene NPs absorbed to polymer films on the QCM constitute a powerful tool with no need for pretreatment for measuring PT in whole blood samples in real time, while these coatings are reusable up to 10 times. PT measurements in excellent agreement with coagulometer tests pave the way for possible future application of QCM in clinical routine.

A silicon micropillar filter (μPF) chip was fabricated, glass-bonded, coated with 3-aminopropyltriethoxysilane (APTES) then tested for its ability to bind and release pre-purified DNA in continuous flow mode. APTES coated μPF was tested over different DNA initial loading amounts and flow rates. Simple and effective washing and eluting steps were used, which allowed direct detection of obtained DNA using UV Nano-Droplet. Both the capture efficiency and elution % were inversely proportional to flow rate, with such relation being more profound at higher DNA concentration. DNA elution recovery %, as high as 80%, was achieved under flow rate of 5 μl /min and an initial DNA loading of 250 ng. The capture capacity per surface area of the APTES-coated μPFis ~186 ng/cm2, which mounts to ~3.7 times the capacity of an identical uncoated filter. These results demonstrate the potential for integrating such amino-coated μPF in a lab-on-a-chip system for the extraction of nucleic acids directly from clinical samples in a continuous flow mode.

Water utility treatment failure, as well as intentional or accidental water intrusions can introduce biological and/ or chemical contaminants into public drinking water distribution systems. However, recently developed real-time water quality sensors can be implemented to detect such contamination events. The overall objective of this study was to evaluate the potential for real-time monitoring of bacterial spore contamination of potable water using several different water quality sensors including: the HACH Monitoring Platform; the JMAR BioSentry unit; and the S::CAN spectro::lyser technology. For this, Bacillus thuringiensis spores were used as a surrogate for Bacillus anthracis. The minimum threshold response of sensors to the microbial contaminant was determined by injecting B. thuringiensis spores into Deionized (DI), filtered or unfiltered tap water. Out of these three evaluated sensors, the BioSentry sensor was capable of detecting introduced spores and responded to B. thuringiensis spores over a concentration range of 102-105 spores/ml. In contrast, The HACH and S::CAN units were not capable of direct detection of spores. However, these two sensors can detect changes in water quality parameters such as turbidity, pH, temperature, total organic carbon and conductivity, due to media that may be associated with spores. Thus, these sensors can be integrated into a contaminant warning system for monitoring intrusion events in water distribution systems.

Human health protection requires relating the bioaccessible concentration of a mutagen with the corresponding likely harm that could be caused through exposure. This requires designating the target receptor in need of protection, and a quantitative understanding of the likely pathways for mutagen availability. In this study, young children were selected as target receptors because of their tendency to directly ingest soils. Most data used to characterise a chemical mutagenicity has been extrapolated from rat-based assays using chemical ingestion or direct injection procedures. Mitomycin C was selected as a relevant model compound and extracted using an established in vitro digestion technique. A range of mutagenic bioassays (i.e. SOS-lux based microbial biosensors and Salmonella mutagenicity assay) were calibrated and optimised in aqueous samples, before being applied to soil extracts. The biosensors were consistently as sensitive and responsive as the traditional Salmonella assay, however, the use of microbial biosensors offered speed and ease of analysis. The data presented confirm that the in vitro digestion bioassay enabled a rapid and inexpensive technique for deriving critical values for the protection of humans exposed to soil borne mutagenic pollutants.

We report the fabrication of ultrasensitive Graphene Oxide (GO) based electrochemical immunosensor to detect human telomerase reverse transcriptase (hTERT), a lung cancer biomarker. The immuno-electrode-has been fabricated by covalent immobilization of rabbit anti-hTERT antibodies (Ab) onto GO films on ITO coated glass. The Fourier Transform Infrared (FTIR) spectroscopic studies confirms the presence of diverse organic functional groups (-COOH, -CHO, -OH) of GO, and the binding (anti-hTERT) onto GO/ITO electrode. Interestingly, Scanning Electron Micrographs (SEM) also reveals clear visual surface modification of the GO film by anti-hTERT antibodies and hTERT antigen (Ag). The electrochemical Differential Pulse Voltammetry (DPV) results show that the GO based immunosensor exhibits specificity and low detection upto 10 ag mL-1 (10×10-18 g mL-1) in wide detection range (10 ag mL-1-50 ng mL-1) for hTERT. The immunosensor showed ability to detect hTERT in spiked sputum samples upto 100 fg mL-1 in dynamic detection range of 100 fg mL-1-10 ng mL-1. The enhanced performance of Ab/GO/ITO is attributed to fast electron transfer and efficient loading of Ab on large surface area provided by GO network. The low level detection of hTERT warrants the realization of point-of-care device for early detection of lung/oral cancer through oral fluids