Ascorbic acid-sensitized Au nanorods-functionalized nanostructured TiO2 transparent electrodes for photoelectrochemical genosensing

Au nanorods (NRs) modified nanostructured TiO2/ITO electrodes have been fabricated and characterized in order to develop a biosensing platform for the photoelectrochemical determination of microRNAs. The proposed method is based on the use of thiolated DNA capture-probes (CPs) immobilized onto Au NR surface. The Au NRs are chemically bound at the surface of TiO2/ITO electrodes by means of the mercaptosuccinic acid linker. Subsequently, the DNA CPs are bound to the Au NR surface through the thiolate group, and reacted with the target RNA sequence. Finally, the obtained biosensing platform is incubated with alkaline phosphatase and l-ascorbic acid 2-phosphate (AAP) enzymatic substrate, for the in situ generation of ascorbic acid (AA). Such AA molecule, coordinating to surface Ti atoms, generates a charge transfer complex, that results in a shift of the UV absorption threshold toward the visible spectral region of the nanostructured TiO2 forming the electrode and, hence, in the occurrence of an absorption band centered at 450\u202fnm. The photoelectrochemical monitoring of the formation of the AA-TiO2 complex, under the visible light of a commercial LED light source, allows the selective and quantitative detection of the target microRNA strands

Photoelectrochemical biosensors for nucleic acid detection

A biosensor for detection of nucleic acids employs, as the sensing element, an oligonucleotide, with a known sequence of bases that can be used to detect specific DNA/RNA sequences through the hybridization reaction (this kind of biosensor is also called a genosensor).Many different transducers can be used in the development of a genosensor. Recently, with the emergence of novel photoelectrochemically active species and new detection schemes, photoelectrochemistry has received increasing attention in the field of biosensors. Advances in the development and applications of photoelectrochemical genosensors are reviewed in this article

Different strategies for the detection of bioagents using electrochemical and photoelectrochemical genosensors

In recent years various kinds of biosensors for the detection of pathogens have been developed. A genosensor consists in the immobilization, onto the surface of a chosen transducer, of an oligonucleotide with a specific base sequence called capture probe. The complementary sequence (the analytical target, i.e. a specific sequence of the DNA/RNA of the pathogen) present in the sample is recognized and captured by the probe through the hybridization reaction. The evaluation of the extent of the hybridization allows one to confirm whether the sample contains the complementary sequence of the probe or not. Electrochemical transducers have received considerable attention in connection with the detection of DNA hybridization. Moreover, recently, with the emergence of novel photoelectrochemically active species and new detection schemes, photoelectrochemistry has resulted in substantial progress in its analytical performance for biosensing applications. In this paper, some examples of electrochemical genosensors for multiplexed pathogen detection are shown. Moreover, the preliminary experiments towards the development of a photoelectrochemical genosensor using a TiO2-nanocrystal-modified ITO electrode are discussed

Alkaline-phosphatase-based nanostructure assemblies for electrochemical detection of microRNAs

Different nanoarchitectures, rich in enzyme labels, are herein investigated for signal amplification in the electrochemical detection of nucleic acids and in particular of microRNAs. Dendritic amplification, accomplished by the use of streptavidin and biotinylated alkaline phosphatase, and enzymedecorated liposomes are used as labels to amplify the microRNA-sensing, by their association to the probe-microRNA hybrid generated onto a gold transducer. Differential pulse voltammetry and faradaic impedance spectroscopy were employed to characterize these different amplification routes

Electrochemical, electrochemiluminescence, and photoelectrochemical aptamer-based nanostructured sensors for biomarker analysis

Aptamer-based sensors have been intensively investigated as potential analytical tools in clinical analysis providing the desired portability, fast response, sensitivity, and specificity, in addition to lower cost and simplicity versus conventional methods. The aim of this review, without pretending to be exhaustive, is to give the readers an overview of recent important achievements about electrochemical, electrochemiluminescence, and photoelectrochemical aptasensors for the protein biomarker determination, mainly cancer related biomarkers, by selected recent publications. Special emphasis is placed on nanostructured-based aptasensors, which show a substantial improvement of the analytical performances

Label-free impedimetric determination of miRNA using biotinylated conducting polymer modified carbon electrodes

Preliminary results are reported on label-free miRNA determination with faradaic electrochemical impedance spectroscopy (EIS) measurements on glassy carbon electrodes (GCEs) and screen-printed carbon electrodes (SPCEs). These electrodes were coated with films of functionalized conducting polymers. For that, bis(2,2\u2032-bithien-5-yl)-(4-hydroxyphenyl)methane biotin ester was used as the functional monomer. This monomer was potentiodynamically electropolymerized to result in deposition of thin polymer films on the electrodes. Next, streptavidin, and then the biotinylated DNA capture probe were immobilized via streptavidin\u2013biotin interactions. Detectability of the resulting biosensor with respect to the complementary miRNA was well below 100 pM

A Mercury-Free Sensor to Control Trace Metal Ionization Used to Treat Pathogens in Water Distribution Systems

The specific aim of this work was the development of an electroanalytical method, based on a mercury-free sensor, for the determination of silver(I) and copper(II) used to treat pathogens in water distribution systems. Analysis of the two metals was performed in 0.1M ammonia solution pH9.0 using Square Wave Anodic Stripping Voltammetry (SWASV). The proposed method is based on the determination of copper, the addition of a masking agent (EDTA) to the solution and afterwards the determination of silver. A detection limit of 23\u3bcg/L and 6\u3bcg/L for 60s of deposition time was obtained for copper and silver, respectively. Analysis of water samples was also reported. \ua9 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Electrochemical and photoelectrochemical biosensors for biomarker detection

A rapid and accurate medical diagnosis is essential in order to determine the health status of a patient. Nowadays, most of the clinical analyses are performed in specialized laboratory, which required specific instrumentation and trained personal, resulting in an increase of analysis costs and time. In this context, biosensors represent ideal tools capable to provide a specific and fast response together with low cost, easy use and portable size features. This work attempts to provide a review of the research progresses of electrochemical and photoelectrochemical biosensor platforms in clinical applications that have been published in recent years. Special emphasis will be devoted to discuss examples for breast cancer biomarker detection, because breast cancer, is considered the leading cause of cancer-related deaths worldwide in women, representing 15% of all cancer related amongst women, with a 6% mortality rate (based on overall cancer deaths). The manuscript is focused on aptamer-based biosensors, because, due to their stability and their relatively low cost, they have been successfully applied in many biosensor formats for breast cancer biomarker detection

Optical and Electrochemical Study of Acridine-Based Polyaza Ligands for Anion Sensing

A variety of transition metal organometallic and coordination receptor systems that can recognize and sense anionic guest species in organic and aqueous media by electrochemical and optical methods have already been reported in literature. In many cases, a redox-active/photo-active transition metal reporter group is used. Here, we describe two novel molecules consisting of a polyaza receptor unit for anion coordination and an acridine moiety as signal generating unit for anion sensing. The optical and electrochemical behavior of the two compounds was investigated in order to define novel detection schemes. In this regard, selenium anionic species selenite (SeO32\u2013) and selenate (SeO42\u2013) were chosen as model system