Electrochemical and PEC platforms for miRNA and other epigenetic markers of cancer diseases: Recent updates

Abstract Besides playing significant biological roles, microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) constitute emerging and burgeoning cancer biomarkers collectable from human fluids. Electrochemical and photoelectrochemical biosensors offer great potential for their detection. However, the low abundance of such molecules in biological fluids, especially in early-stage cancer patients, makes it highly necessary to employ signal/sample amplification strategies. Among the variety of these strategies reported in the literature, in this review we summarize the recent advancements in the field, giving an account of the different approaches aimed to overcome this main obstacle. To this end, enzyme-, redox probe- and nanomaterial-based signal amplification strategies, as well as sample-amplification-hyphenated-techniques are assessed, by discussing selected examples. The highlighted approaches demonstrate the use of a variety of specific receptors and (photo)electrochemical assay formats, including the rapid development of novel biology-inspired sensing schemes

Electrochemical sensors based on sewage sludge-derived biochar for the analysis of anthocyanins in berry fruits

The reutilization of waste and the reduction of the general environmental impact of every production are fundamental goals that must be achieved in the framework of a circular economy. Recycled carbon-rich materials may represent a promising alternative to other less-sustainable carbonaceous materials used in the production of electrochemical sensing platforms. Herein, we propose an innovative carbon paste electrode (CPE) composed of biochar derived from biological sludge obtained from municipal and industrial wastewater treatment plants. The physicochemical properties of the biochar after a chemical treatment with an acidic solution obtained from industrial by-products were investigated. The electrode surface characterization was carried out by analyzing common redox probes and multiple phenols bearing varying numbers of –OH and –OCH(3) groups in their structure. Furthermore, the CPE was also tested on the evaluation of the phenolic fingerprints of Vaccinium myrtillus, Vaccinium uliginosum subsp. gaultherioides, and Fragaria × ananassa. Standard anthocyanin mixtures and extracts of the aforementioned fruits were analyzed to provide a phenolic characterization of real samples. The obtained results show that the sewage sludge–derived biochar can be a promising material for the development of electroanalytical sensors. GRAPHICAL ABSTRACT: [Image: see text] SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00216-022-04062-y

Aptasensors for the Detection of Environmental Contaminants of High Concern in Water Bodies: A Systematic Review

With the advancement of technology and increasing industrial activity, anthropogenic contaminants are currently detected where there is no record of their presence or insufficient information about their toxicological impact. Consequently, there are not sufficiently robust local or global regulations, the ecotoxicological and human health risks are critical, and they may not be routinely monitored despite being ubiquitous. The interest in studying environmental contaminants, including micropollutants and emerging contaminants, in complex environmental water samples has grown in the last decade. Due to the concentrations in which they are typically found in the environment and the rapid global dispersion, the detection procedures for these substances must be capable of measuring very low concentrations. Many efforts have been made to improve remediation procedures or develop novel analytical methods for their determination. Although there are several robust and reliable standard analytical techniques for their monitoring, pollutant contamination requires simple and inexpensive methods for massive, in situ monitoring campaigns. In this regard, biosensors have emerged as devices with high selectivity, sensitivity, easy operation, and short analysis times. Aptasensors are biosensors based on a nucleic acid recognition element (aptamer). Due to their synthetic nature, stability, and easy production, aptamers are frequently employed to develop bioassays. This work presents a systematic review of the trends in using aptasensors for detecting environmental contaminants present in environmental water samples, as well as the estimation of the potential technological contribution these devices might give to environmental monitoring

Bicyclic peptide-based assay for uPA cancer biomarker

The use of synthetic bioreceptors to develop biosensing platforms has been recently gaining momentum. This case study compares the performance of a biosensing platform for the human biomarker urokinase-type plasminogen activator (h-uPA) when using two bicyclic peptides (P1 and P2) with different affinities for the target protein. The bioreceptors P1 and P2 were immobilized on magnetic microbeads and tested within a sandwich-type affinity electrochemical assay. Apart from enabling h-uPA quantification at nanomolar levels (105.8 ng/mL for P1 and 32.5 ng/mL for P2), this case study showed the potential of synthetic bicyclic peptides applicability and how bioreceptor affinity can influence the performance of the final sensing platform

Chip-Based and Wearable Tools for Isothermal Amplification and Electrochemical Analysis of Nucleic Acids

The determination of nucleic acids has become an analytical diagnostic method with many applications in fields such as biomedical sciences, environmental monitoring, forensic identification, and food safety. Among the different methods for nucleic acid analysis, those based on the polymerase chain reaction (PCR) are nowadays considered the gold standards. Isothermal amplification methods are an interesting alternative, especially in the design of chip-based architectures. Biosensing platforms hold great promise for the simple and rapid detection of nucleic acids since they can be embedded in lab-on-a-chip tools to perform nucleic acid extraction, amplification, and detection steps. Electrochemical transduction schemes are particularly interesting in the design of small and portable devices due to miniaturization, low-energy consumption, and multianalyte detection capability. The aim of this review is to summarize the different applications of isothermal amplification methods combined with electrochemical biosensing techniques in the development of lab-on-a-chip tools and wearable sensors. Different isothermal amplification methods are revised, and examples of different applications are discussed. Finally, a discussion on patented devices is also included

Chip-Based and Wearable Tools for Isothermal Amplification and Electrochemical Analysis of Nucleic Acids

The determination of nucleic acids has become an analytical diagnostic method with many applications in fields such as biomedical sciences, environmental monitoring, forensic identification, and food safety. Among the different methods for nucleic acid analysis, those based on the polymerase chain reaction (PCR) are nowadays considered the gold standards. Isothermal amplification methods are an interesting alternative, especially in the design of chip-based architectures. Biosensing platforms hold great promise for the simple and rapid detection of nucleic acids since they can be embedded in lab-on-a-chip tools to perform nucleic acid extraction, amplification, and detection steps. Electrochemical transduction schemes are particularly interesting in the design of small and portable devices due to miniaturization, low-energy consumption, and multianalyte detection capability. The aim of this review is to summarize the different applications of isothermal amplification methods combined with electrochemical biosensing techniques in the development of lab-on-a-chip tools and wearable sensors. Different isothermal amplification methods are revised, and examples of different applications are discussed. Finally, a discussion on patented devices is also included

Characterization of a Ruthenium(II) Complex in Singlet Oxygen-Mediated Photoelectrochemical Sensing

[Image: see text] A water-soluble ruthenium(II) complex (L), capable of producing singlet oxygen ((1)O(2)) when irradiated with visible light, was used to modify the surface of an indium–tin oxide (ITO) electrode decorated with a nanostructured layer of TiO(2) (TiO(2)/ITO). Singlet oxygen triggers the appearance of a cathodic photocurrent when the electrode is illuminated and biased at a proper reduction potential value. The L/TiO(2)/ITO electrode was first characterized with cyclic voltammetry, impedance spectroscopy, NMR, and Raman spectroscopy. The rate constant of singlet oxygen production was evaluated by spectrophotometric measurements. Taking advantage of the oxidative process initiated by (1)O(2), the analysis of phenolic compounds was accomplished. Particularly, the (1)O(2)-driven oxidation of hydroquinone (HQ) produced quinone moieties, which could be reduced back at the electrode surface, biased at −0.3 V vs Ag/AgCl. Such a light-actuated redox cycle produced a photocurrent dependent on the concentration of HQ in solution, exhibiting a limit of detection (LOD) of 0.3 μmol dm(–3). The L/TiO(2)/ITO platform was also evaluated for the analysis of p-aminophenol, a commonly used reagent in affinity sensing based on alkaline phosphatase

Highly Charged Ru(II) Polypyridyl Complexes as Photosensitizer Agents in Photodynamic Therapy of Epithelial Ovarian Cancer Cells

Ovarian cancer recurrence is frequent and associated with chemoresistance, leading to extremely poor prognosis. Herein, we explored the potential anti-cancer effect of a series of highly charged Ru(II)-polypyridyl complexes as photosensitizers in photodynamic therapy (PDT), which were able to efficiently sensitize the formation of singlet oxygen upon irradiation (Ru12+ and Ru22+) and to produce reactive oxygen species (ROS) in their corresponding dinuclear metal complexes with the Fenton active Cu(II) ion/s ([CuRu1]4+ and [Cu2Ru2]6+). Their cytotoxic and anti-tumor effects were evaluated on human ovarian cancer A2780 cells both in the absence or presence of photoirradiation, respectively. All the compounds tested were well tolerated under dark conditions, whereas they switched to exert anti-tumor activity following photoirradiation. The specific effect was mediated by the onset of programed cell death, but only in the case of Ru12+ and Ru22+ was preceded by the loss of mitochondrial membrane potential soon after photoactivation and ROS production, thus supporting the occurrence of apoptosis via type II photochemical reactions. Thus, Ru(II)-polypyridyl-based photosensitizers represent challenging tools to be further investigated in the identification of new therapeutic approaches to overcome the innate chemoresistance to platinum derivatives of some ovarian epithelial cancers and to find innovative drugs for recurrent ovarian cancer