Photoelectrochemical aptasensors for detection of viruses.

Photoelectrochemistry (PEC) is a dynamic discipline studying the effect of light on photoelectrode or photosensitive material, and the conversion from solar energy into electrical power. The basic PEC process refers to the oxidation or reduction reactions between electrochemical active species in solution and photoactive materials that occurred at the electrode/electrolyte interface during illumination. In recent years, the PEC biosensing approaches have also been developed by the combination of the PEC technique with bioanalysis, where the interaction between biological recognition element and analyte influences a photocurrent signal. This involves the charge and energy transfer of PEC reaction between electron donor/acceptor and photoactive material upon light irradiation. Coupling the advantages of PEC bioanalysis and aptamers has provided new concepts for highly selective and sensitive biosensors development, applicable in human health monitoring and environmental protection. In a typical assay, a photoactive material converts the affinity binding properties of aptamers into a detectable electrical signal, presenting an innovative method for probing numerous aptamer-analyte interactions. Using different aptamer probes aiming for specific purposes, more sensing strategies with rational design and exquisite signaling mechanisms have been proposed. This review concentrated on the current topic of PEC aptasensors that are used for the detection of viruses. The prospects in this area are also discussed.

Gallic acid-coated silver nanoparticles as perspective drug nanocarriers: bioanalytical study.

The ability of silver nanoparticles (AgNPs) to be used as drug nanocarriers has helped rapidly to invent novel strategies to treat diseases, such as cancer. The nanoparticles may offer a valuable tool to novel pH-sensitive drug delivery systems in the present scenario because of their undergoing mechanisms associated with the regulated dissolution, aggregation, and generation of oxygen radicals as well. These processes could be monitored by electrochemical (bio)sensors that are less money and time-consuming compared to other analytical approaches, however, with comparable analytical performance. In this paper, synthesized and microscopically characterized gallic acid-coated AgNPs (GA-AgNPs) are investigated using spectral and electrochemical methods. To investigate the Ag+ release, a 21-day ageing experiment is performed spectrophotometrically, finding that the peak maximum of GA-AgNPs spectra diminished by 24.5%. The highest Ag+ content was electrochemically determined in the supernatant solution after centrifugation (6.97 µmol·L-1), while no significant concentration of silver ions in solution after redispersion was observed (1.26 µmol·L-1). The interaction experiment indicates a stabilization of GA-AgNPs in the presence of long-chain dsDNA as well as a mutual electrostatic interaction with DNA sugar-phosphate backbone. This interaction mechanism is confirmed by FTIR analysis, showing a shift (1049 to 1061 cm-1 and 913 to 964 cm-1) specific to DNA phosphate bands. Finally, doxorubicin-loaded GA-AgNPs are monitored for the specific drug release in the physiological and more reactive weakly acidic microenvironment. Hereby, electrochemical (bio)sensing of GA-AgNPs undergoing mechanisms shows a huge potential to be used for monitoring of drug delivery systems at cancer therapy.

Application of silver solid amalgam electrodes in electrochemical detection of DNA damage.

In this study, a mercury meniscus-modified silver solid amalgam electrode was used for the first time for the detection of UV-induced DNA damage. The integrity of the double-stranded DNA (dsDNA) layer was detected indirectly using the evaluation of the methylene blue reduction within its accumulation into dsDNA after the UV irradiation of the biosensor surface with two different wavelengths (254 nm and 365 nm), monitored by differential pulse voltammetry. Moreover, a simple electrochemical characterization of the biosensor surface was performed using cyclic voltammetry of the redox indicator hexaammineruthenium chloride (RuHex) present in the solution. Electrochemical impedance spectroscopy (EIS) was used in both cases for the verification of results. Individual electrochemical signals depend on the time of biosensor exposure to UV irradiation as well as on the selected wavelengths and are different for both used types of dsDNA (salmon sperm and calf thymus). The highest degradation degree up to 60% was observed using sensitive EIS of methylene blue after 10 min irradiation of the biosensor at 254 nm. The use of RuHex seems to be less sensitive for the detection of dsDNA structural changes, when the degradation degree up to 40% was observed, using EIS at the same conditions.

Advanced materials-integrated electrochemical sensors as promising medical diagnostics tools: A review.

Electrochemical sensors have increasingly been linked with terms as modern biomedically effective highly selective and sensitive devices, wearable and wireless technology, portable electronics, smart textiles, energy storage, communication and user-friendly operating systems. The work brings the overview of the current advanced materials and their application strategies for improving performance, miniaturization and portability of sensing devices. It provides the extensive information on recently developed (bio)sensing platforms based on voltammetric, amperometric, potentiometric and impedimetric detection modes including portable, non-invasive, wireless, and self-driven miniaturized devices for monitoring human and animal health. Diagnostics of selected free radical precursors, low molecular biomarkers, nucleic acids and protein-based biomarkers, bacteria and viruses of today's interest is demonstrated.

Interaction of DNA and mononucleotides with theophylline investigated using electrochemical biosensors and biosensing.

The understanding of DNA-drug interaction mechanism is among the important aspects of biological studies for drug design, discovery and pharmaceutical development processes. Published rather detailed FTIR and UV-visible spectroscopic studies on the interactions of theophylline, theobromine and caffeine with calf thymus DNA have shown effective binding of these methylxanthine derivatives to DNA and RNA involving H-bonds. However, to our knowledge, there is no such investigation using electrochemical approach. As a novelty of the study, in this paper the bioelectrochemical approach has been chosen for the investigation of an interaction of low molecular salmon sperm dsDNA, ssDNA and mononucleotides with theophylline (TP) in aqueous phosphate buffered medium using DNA-based electrochemical biosensors and biosensing in solution phase. Exploitation of the electrochemical approach via changes in square wave voltammetric responses of deoxyguanosine (dGuo) and deoxyadenosine (dAdo) provided a new indication on preferential association of TP with dGuo in the case of double helical dsDNA structure which was not reported previously. Moreover, an attachment of TP molecules outside DNA was found in the presence of high concentration of 3.3 × 10-4 M TP in solution which diminishes the electron transfer and leads to the difficulties in quantitative evaluation of the TP and dGuo voltammetric responses. The changes in UV-vis and FTIR spectra obtained in the same medium confirmed the association interaction of TP with both nucleobases. Utilizing the model and the published energies of hydrogen bonding stabilization, the formation of a DNA-TP complex was predicted through the intermolecular H-bonds between TP and the NH-CO moiety of guanine and the N-NH2 moiety of adenine.