Piezoelectric Biosensor for a Simple Serological Diagnosis of Tularemia in Infected European Brown Hares (Lepus europaeus)

Use of Cysteamine and Glutaraldehyde Chemicals for Robust Functionalization of Substrates with Protein Biomarkers—An Overview on the Construction of Biosensors with Different Transductions

Currently, several biosensors are reported to confirm the absence/presence of an abnormal level of specific human biomarkers in research laboratories. Unfortunately, public marketing and/or pharmacy accessibility are not yet possible for many bodily fluid biomarkers. The questions are numerous, starting from the preparation of the substrates, the wet/dry form of recognizing the (bio)ligands, the exposure time, and the choice of the running buffers. In this context, for the first time, the present overview summarizes the pre-functionalization of standard and nanostructured solid/flexible supports with cysteamine (Cys) and glutaraldehyde (GA) chemicals for robust protein immobilization and detection of biomarkers in body fluids (serum, saliva, and urine) using three transductions: piezoelectrical, electrochemical, and optical, respectively. Thus, the reader can easily access and compare step-by-step conjugate protocols published over the past 10 years. In conclusion, Cys/GA chemistry seems widely used for electrochemical sensing applications with different types of recorded signals, either current, potential, or impedance. On the other hand, piezoelectric detection via quartz crystal microbalance (QCM) and optical detection by surface plasmon resonance (LSPR)/surface-enhanced Raman spectroscopy (SERS) are ultrasensitive platforms and very good candidates for the miniaturization of medical devices in the near future.

Current Trends in the Biosensors for Biological Warfare Agents Assay

Biosensors are analytical devices combining a physical sensor with a part of biological origin providing sensitivity and selectivity toward analyte. Biological warfare agents are infectious microorganisms or toxins with the capability to harm or kill humans. They can be produced and spread by a military or misused by a terrorist group. For example, Bacillus anthracis, Francisella tularensis, Brucella sp., Yersinia pestis, staphylococcal enterotoxin B, botulinum toxin and orthopoxviruses are typical biological warfare agents. Biosensors for biological warfare agents serve as simple but reliable analytical tools for the both field and laboratory assay. There are examples of commercially available biosensors, but research and development of new types continue and their application in praxis can be expected in the future. This review summarizes the facts and role of biosensors in the biological warfare agents' assay, and shows current commercially available devices and trends in research of the news. Survey of actual literature is provided.

Biochemical responses and oxidative stress in Francisella tularensis infection: a European brown hare model

BACKGROUND

The aim of the present study was to investigate biochemical and oxidative stress responses to experimental F. tularensis infection in European brown hares, an important source of human tularemia infections.

METHODS

For these purposes we compared the development of an array of biochemical parameters measured in blood plasma using standard procedures of dry chemistry as well as electrochemical devices following a subcutaneous infection with a wild Francisella tularensis subsp. holarctica strain (a single dose of 2.6 × 10⁹ CFU pro toto).

RESULTS

Subcutaneous inoculation of a single dose with 2.6 × 10⁹ colony forming units of a wild F. tularensis strain pro toto resulted in the death of two out of five hares. Plasma chemistry profiles were examined on days 2 to 35 post-infection. When compared to controls, the total protein, urea, lactate dehydrogenase, aspartate aminotransferase and alanine aminotransferase were increased, while albumin, glucose and amylase were decreased. Both uric and ascorbic acids and glutathione dropped on day 2 and then increased significantly on days 6 to 12 and 6 to 14 post-inoculation, respectively. There was a two-fold increase in lipid peroxidation on days 4 to 8 post-inoculation.

CONCLUSIONS

Contrary to all expectations, the present study demonstrates that the European brown hare shows relatively low susceptibility to tularemia. Therefore, the circumstances of tularemia in hares under natural conditions should be further studied.

Immobilization, hybridization, and oxidation of synthetic DNA on gold surface: electron transfer investigated by electrochemistry and scanning tunneling microscopy

Fundamental understanding of interfacial electron transfer (ET) among electrolyte/DNA/solid-surface will facilitate the design for electrical detection of DNA molecules. In this report, the electron transfer characteristics of synthetic DNA (sequence from pathogenic Cryptosporidium parvum) self-assembled on a gold surface was electrochemically studied. The effects of immobilization order on the interface ET related parameters such as diffusion coefficient (D0), surface coverage (thetaR), and monolayer thickness (d(i)) were determined by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). DNA surface density (Gamma(DNA)) was determined by the integration of the charge of the electro-oxidation current peaks during the initial cyclic voltammetry scans. It was found that the DNA surface densities at different modifications followed the order: Gamma(DNA) (dsS-DNA/Au) > Gamma(DNA) (MCH/dsS-DNA/Au) > Gamma(DNA) (dsS-DNA/MCH/Au). It was also revealed that the electro-oxidation of the DNA modified gold surface would involve the oxidation of nucleotides (guanine and adenine) with a 5.51 electron transfer mechanism and the oxidative desorption of DNA and MCH molecules by a 3 electron transfer mechanism. STM topography and current image analysis indicated that the surface conductivity after each surface modification followed the order: dsS-DNA/Au < MCH/dsS-DNA/Au < oxidized MCH/dsS-DNA/Au < Hoechst/oxidized MCH/dsS-DNA/Au. The results from this study suggested a combination of variations in immobilization order may provide an alternative approach for the optimization of DNA hybridization and the further development for electrical detection of DNA.

Utilization of Electrochemical Sensors and Biosensors in Biochemistry and Molecular Biology

A special issue of Sensors entitled “Utilization of Electrochemical Sensors and Biosensors in Biochemistry and Molecular Biology” has been prepared over a period of three years. In this Editorial Note we would like to highlight one of the possible directions for electrochemical sensor and biosensor research resulting from the ideas of Czechoslovakian Nobel Prize winner Jaroslav Heyrovsky and his colleague Rudolf Brdicka.

Amperometric Biosensors for Real Time Assays of Organophosphates

An amperometric biosensor based on acetylcholinesterase (AChE) immobilized in gelatin was used to develop an assay for the organophosphate paraoxon. The more traditional manner employing preincubation was used for comparison between measurement procedures, although the aim of the study was to examine the performance of the biosensor for real time monitoring of organophosphates. The biosensor was immersed in a reaction chamber and paraoxon was injected inside. We were able to detect 200 pg of paraoxon within one minute or 2.5 ppb when the biosensor was preincubed in the sample solution for 15 minutes. The practical impact and expectations are discussed.

Diagnosis of Intoxication by the Organophosphate VX: Comparison Between an Electrochemical Sensor and Ellman´s Photometric Method

An electrochemical sensor is introduced as a tool applicable for diagnosis of intoxication by cholinesterase inhibitors caused by the well-known nerve agent VX. The traditional Ellman method was chosen for comparison with the sensor's analytical parameters. Both methods are based on estimation of blood cholinesterase inhibition as a marker of intoxication. While Ellman´s method provided a limit of detection of 5.2´10^-7 M for blood containing VX, the electrochemical sensor was able to detect 4.0´10^-7 M. Good correlation between both methods was observed (R = 0.92). The electrochemical sensor could be considered a convenient tool for a fast yet accurate method, easily available for field as well as laboratory use. Time and cost savings are key features of the sensor-based assay.