Sustainable Copper Electrochemical Stripping onto a Paper-Based Substrate for Clinical Application

Electrochemical detection of miRNA using commercial and hand-made screen-printed electrodes: liquid biopsy for cancer management as case of study

The growth of liquid biopsy, i. e., the possibility of obtaining health information by analysing circulating species (nucleic acids, cells, proteins, and vesicles) in peripheric biofluids, is pushing the field of sensors and biosensors beyond the limit to provide decentralised solutions for nonspecialists. In particular, among all the circulating species that can be adopted in managing cancer evolution, both for diagnostic and prognostic applications, microRNAs have been highly studied and detected. The development of electrochemical devices is particularly relevant for liquid biopsy purposes, and the screen-printed electrodes (SPEs) represent one of the building blocks for producing novel portable devices. In this work, we have taken miR-2115-3p as model target (it is related to lung cancer), and we have developed a biosensor by exploiting the use of a complementary DNA probe modified with methylene blue as redox mediator. In particular, the chosen sensing architecture was applied to serum measurements of the selected miRNA, obtaining a detection limit within the low nanomolar range; in addition, various platforms were interrogated, namely commercial and hand-made SPEs, with the aim of providing the reader with some insights about the optimal platform to be used by considering both the cost and the analytical performance.

Calcium-Based Metal-Organic Framework: Detection and Idiosyncratic Removal of Copper by Nano-Particle Deposition

A novel calcium-based metal-organic framework (CaMOF@LSB) was designed and synthesized, exhibiting dual functionality for both selective detection and removal of Cu2+ ions from aqueous solutions. The framework's stability, including solvent and pH variations, was established with notable thermal resilience. Colorimetric Cu2+ detection (≥5 ppm) with a high capture capacity of 484.2 mg g-1 by CaMOF@LSB places this material among the few that ensure efficient colorimetric detection and high removal capabilities of Cu2+ ions. Batch adsorption experiments revealed pH-dependent behavior and competitive interactions. Langmuir and pseudo-second-order kinetics models aptly described adsorption isotherms and kinetics, respectively. Thermodynamic assessments confirmed spontaneous and endothermic adsorption. Mechanistically, nanoparticle deposition contributes to the Cu2+ uptake. CaMOF@LSB also exhibited one of the best removal behaviour of Cu2+ by means of oxide formation on the surface. Regeneration of CaMOF@LSB was achieved by simple sonication in 0.1 M aqueous NaOH solution. The recyclability was also tested up to 5 cycles, and it exhibited a small decrease in adsorption capacity observed across the cycles. This research presents a promising avenue for addressing heavy metal pollution using metal-organic frameworks, thereby offering potential applications in water purification and environmental pollution monitoring and remediation.

3D Paper-Based Origami Device for Programmable Multifold Analyte Preconcentration

In analytical chemistry, preconcentration represents a critical step able to enhance the accuracy of detection; however, the experimental procedures needed to preconcentrate samples might be characterized by drawbacks regarding the whole analytical process, e.g., being complex, invasive, and/or time-consuming. In this study, a novel 3D paper-based origami device is introduced for multifold analyte preconcentration. Leveraging the benefits of paper-based substrates, the proposed architecture boosts sample preconcentration while minimizing time and tasks for measurements, solely by exploiting the porous and versatile nature of paper-based substrates. In comparison with other paper-based approaches reported in the literature for preconcentration, the present architecture offers the ability to be programmed for obtaining the needed sensitivity increase without sacrificing measurement time. To demonstrate the efficacy of the novel approach, the 3D paper-based origami device was deeply characterized, including the most relevant parameters, i.e., disk size and number, unfolding time, and volume, and subsequently applied for the preconcentration and the detection of various analytes in real matrices, namely, mercury in tap water and glucose in sweat, resulting in a 400% and 300% sensitivity enhancement, respectively. This innovative preconcentration tool addresses the limitations of existing conventional methods, providing increased sensitivity without the use of expensive and time-consuming procedures through only exploiting the intrinsic properties of paper-based substrates and a rationale design. The proposed architecture emerges as a universal tool to be adopted and programmed for various analytical systems and fields of application.

Remediate and sense: alginate beads empowered by portable electrochemical strips for copper ion removal and detection at environmental sites

The contamination of environmental sites due to the presence of persistent species represents an important issue to be tackled. In particular, the presence of high levels of metals in soil and surface water is more frequent. One of the metals that sometimes exceeds the permissible limit set by regulatory authorities is copper. For instance, copper-based fungicides are widely used in viticulture. However, copper ions remain in soil and can enter the food chain, posing threats to human health and environmental safety. Although the rapid detection of copper ions using portable sensors is effective in enhancing early warning, it sometimes solves only half of the problem as remediation is not considered. In this paper, we present a novel integrated/portable approach that merges the remediation and sensing of metals by proposing a remediate-and-sense concept. In order to realize this concept, alginate beads were coupled with printed electrochemical strips for on-site copper detection. Within the same architecture, alginate beads were used to remove copper ions from the soil, and printed electrochemical strips were used to evaluate the efficacy of remediation at the point of need. The concept was applied towards soil containing copper ions at the parts per billion level; with few alginate beads and in the absence of additional species, copper ions were quantitatively removed from the matrix; and 3D printing allowed us to combine the printed strips and spheres within a unique tool. The architecture was optimized and the results were compared to inductively coupled plasma-mass spectrometry (ICP-MS) measurements with a recovery percentage of 90%-110%. It should be noted that this novel portable approach may be applied to other pollutants, opening new possibilities for integrated remediation and sensing.

Technical Evaluation of a Paper-Based Electrochemical Strip to Measure Nitrite Ions in the Forensic Field

Nitrite is a compound used as a food additive for its preservative action and coloring capability, as well as an industrial agent for its antifreezing action and for preventing corrosion, and it is also used as a pharmaceutical in cyanide detoxification therapy. However, even recently, because of its high toxicity, it has been used as a murder and suicidal agent due to its affordability and ready availability. In this technical report, we describe an electrochemical paper-based device for selectively determining nitrite in complex biofluids, such as blood, cadaveric blood, vitreous humor, serum, plasma, and urine. The approach was validated in terms of the linearity of response, selectivity, and sensitivity, and the accuracy of the determination was verified by comparing the results with a chromatographic instrumental method. A linear response was observed in the micromolar range; the sensitivity of the method expressed as the limit of detection was 0.4 μM in buffer measurements. The simplicity of use, the portability of the device, and the performance shown make the approach suitable for detecting nitrite in complex biofluids, including contexts of forensic interest, such as murders or suicides in which nitrite is used as a toxic agent. Limits of detection of ca. 1, 2, 4, 5, 3, and 4 μM were obtained in vitreous humor, urine, serum and plasma, blood, and cadaveric blood, also highlighting a satisfactory accuracy comprised between 91 and 112%.

Microfluidic paper-based analytical devices for simultaneous detection of oxidative potential and copper in aerosol samples

The potential reach of point-of-care (POC) diagnostics into daily routines for exposure to reactive oxygen species (ROS) and Cu in aerosolized particulate matter (PM) demands that microfluidic paper-based analytical devices (μPADs) take into consideration the simple detection of these toxic PM components. Here, we propose μPADs with a dual-detection system for simultaneous ROS and Cu(II) detection. For colorimetric ROS detection, the glutathione (GSH) assay with a folding design to delay the reaction yielded complete ROS and GSH oxidation, and improved homogeneity of color development relative to using the lateral flow pattern. For electrochemical Cu(II) determination, 1,10-phenanthroline/Nafion modified graphene screen-printed electrodes showed ability to detect Cu(II) down to pg level being low enough to be applied to PM analysis. No intra- and inter-interference affecting both systems were found. The proposed μPADs obtained LODs for 1,4-naphthoquinone (1,4-NQ), used as the ROS representative, and Cu(II) of 8.3 ng and 3.6 pg, respectively and linear working ranges of 20 to 500 ng for ROS and 1 × 10^-2 to 2 × 10² ng for Cu(II). Recovery of the method was between 81.4 and 108.3% for ROS and 80.5-105.3% for Cu(II). Finally, the sensors were utilized for simultaneous ROS and Cu(II) determination in PM samples and the results statistically agreed with those using the conventional methods at 95% confidence.

Electrochemical nano biosensors for the detection of extracellular vesicles exosomes: From the benchtop to everywhere?

Detection of extracellular vesicles (EVs) exosomes is a challenge to address the need for better diagnostic tests and to create a point-of-care (POC) platform that can detect, monitor and treat health conditions early to allow personalized therapies. A multidisciplinary approach is needed to address these health-related technical issues. Over the past decade, materials scientists and engineers have worked on the same platform to develop flexible, lightweight, miniaturized, and integrated POC devices for exosome detection. Therefore, exosome detection based on various nanomaterials is of particular interest. In this paper, we describe the current state of knowledge on 0D-3D nanostructured materials and present a POC-based technique for exosome detection. Finally, the challenges that need to be solved to expand their clinical application are discussed.

β-Cyclodextrin/CMK-8-Based Electrochemical Sensor for Sensitive Detection of Cu2+

In this work, β-cyclodextrin (β-CD)/mesoporous carbon (CMK-8) nanocomposite was synthesized and used as an electrochemical sensing platform for highly sensitive and selective detection of Cu2+. The morphology and structure of β-CD/CMK-8 were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD). In addition, the dates from electrochemical impedance spectroscopy (EIS) and Cyclic voltammetry (CV) demonstrated that the β-CD/CMK-8 possessed a fast electronic transfer rate and large effective surface area. Besides this, the β-CD/CMK-8 composite displayed high enrichment ability toward Cu2+. As a result of these impressive features, the β-CD/CMK-8 modified electrode provided a wide linear response ranging from 0.1 ng·L−1 to 1.0 mg·L−1 with a low detection limit of 0.3 ng·L−1. Furthermore, the repeatability, reproducibility and selectivity of β-CD/CMK-8 towards Cu2+ were commendable. The sensor could be used to detect Cu2+ in real samples. All in all, this work proposes a simple and sensitive method for Cu2+ detection, which provides a reference for the subsequent detection of HMIs.