Miguel A. González-Fuentes

We present a miniaturized electrochemical immunosensor for the detection of cardiac troponin I (cTnI), fabricated on aluminum foil electrodes modified with carboxylated multi-walled carbon nanotubes (MWCNTs) and poly(amidoamine) (PAMAM) dendrimers. Aluminum was selected as a low-cost and recyclable substrate, offering favorable properties for the development of disposable biosensing platforms. The functionalization strategy enabled efficient covalent immobilization of anti-cTnI antibodies, preserving their biological activity and allowing for sensitive and specific antigen recognition. The immunosensor exhibited dual linear response ranges from 0.001-3 ng/mL⁻¹ and 5-50 ng/mL⁻¹, with a limit of detection down to 0.0016 ng/mL⁻¹. Calibration was validated through both differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS), revealing a shift from active binding to surface saturation. Analytical performance was confirmed in human serum samples, with excellent agreement to electrochemiluminescence immunoassay (ECLIA) values. Notably, the sensor was also evaluated in minimally processed whole blood, achieving accurate detection of cTnI across 0.001-50 ng/mL⁻¹ using only 1 µL of diluted sample, without anticoagulants or separation steps. Despite reduced recovery at 0.001 ng/mL⁻¹ due to matrix interference, a distinguishable signal was obtained, demonstrating trace-level sensitivity in complex biological media. These results establish the platform’s analytical robustness and highlight its strong potential for future integration into portable diagnostic devices for decentralized cardiac monitoring.

Cardiac troponin I (cTnI) is a biomarker widely related to acute myocardial infarction (AMI), one of the leading causes of death around the world. Point-of-care testing (POCT) of cTnI not only demands a short turnaround time for its detection but the highest accuracy levels to set expeditious and adequate clinical decisions. The analytical technique Surface-enhanced Raman spectroscopy (SERS) possesses several properties that tailor to the POCT format, such as its flexibility to couple with rapid assay platforms like microfluidics and paper-based immunoassays. Here, we analyze the strategies used for the detection of cTnI by SERS considering POCT requirements. From the detection ranges reported in the reviewed literature, we suggest the diseases other than AMI that could be diagnosed with this technique. For this, a section with information about cardiac and non-cardiac diseases with cTnI release, including their release kinetics or cut-off values are presented. Likewise, POCT features, the use of SERS as a POCT technique, and the biochemistry of cTnI are discussed. The information provided in this review allowed the identification of strengths and lacks of the available SERS-based point-of-care tests for cTnI and the disclosing of requirements for future assays design.

The diagnosis of respiratory viruses of zoonotic origin (RVsZO) such as influenza and coronaviruses in humans is crucial, because their spread and pandemic threat are the highest. Surface–enhanced Raman spectroscopy (SERS) is an analytical technique with promising impact for the point–of–care diagnosis of viruses. It has been applied to a variety of influenza A virus subtypes, such as the H1N1 and the novel coronavirus SARS−CoV−2. In this work, a review of the strategies used for the detection of RVsZO by SERS is presented. In addition, relevant information about the SERS technique, anthropozoonosis, and RVsZO is provided for a better understanding of the theme. The direct identification is based on trapping the viruses within the interstices of plasmonic nanoparticles and recording the SERS signal from gene fragments or membrane proteins. Quantitative mono- and multiplexed assays have been achieved following an indirect format through a SERS-based sandwich immunoassay. Based on this review, the development of multiplex assays that incorporate the detection of RVsZO together with their specific biomarkers and/or secondary disease biomarkers resulting from the infection progress would be desirable. These configurations could be used as a double confirmation or to evaluate the health condition of the patient.

The indirect determination of the most used herbicide worldwide, glyphosate, was achieved by the SERS technique using hemin chloride as the reporter molecule. An incubation process between hemin and glyphosate solutions was required to obtain a reproducible Raman signal on SERS substrates consisting of silicon decorated with Ag nanoparticles (Si-AgNPs). At 780 nm of excitation wavelength, SERS spectra from hemin solutions do not show extra bands in the presence of glyphosate. However, the hemin bands increase in intensity as a function of glyphosate concentration. This allows the quantification of the herbicide using as marker band the signal associated with the ring breathing mode of pyridine at 745 cm⁻¹. The linear range was from 1 × 10⁻¹⁰ to 1 × 10⁻⁵ M and the limit of detection (LOD) was 9.59 × 10⁻¹² M. This methodology was successfully applied to the quantification of the herbicide in honey. From Raman experiments with and without silver nanoparticles, it was possible to state that the hemin is the species responsible for the absorption in the absence or the presence of the herbicide via vinyl groups. Likewise, when the glyphosate concentration increases, a subtle increase occurs in the planar orientation of the vinyl group at position 2 in the porphyrin ring of hemin over the silver surface, favoring the reduction of the molecule. The total Raman signal of the hemin-glyphosate incubated solutions includes a maximized electromagnetic contribution by the use of the appropriate laser excitation, and chemical contributions related to charge transfer between silver and hemin, and from resonance properties of Raman scattering of hemin. Incubation of the reporter molecule with the analyte before the conjugation with the SERS substrate has not been explored before and could be extrapolated to other reporter-analyte systems that depend on a binding equilibrium process.

Electrochemical oxidation depends enormously on the electrode materials used during electrolysis. Dimensionally Stable Anodes (DSA) represent a good option for electrochemical oxidation applied to wastewater treatment due to the ability of generating hydroxyl radicals. These radicals are strong, non-selective oxidizing agents, which are able to react with organic pollutants and mineralize them. However, this kind of electrodes is commonly synthesized from chloride precursors, which represents an environmental problem, because they can form undesirable chlorinated by-products during the electrolysis. Some DSA electrodes such as PbO₂, SnO₂-Sb₂O₅ and TiO₂ are promising anodes due to their high over-potential for oxygen evolution, which leads to the ability of OH radical production; however, their main drawback is the low chemical stability [1, 2]. This disadvantage prevents their use in environmental applications and causes the search for other materials with better properties. In this work we present the synthesis as well as its electrochemical application of a DSA electrode composed of Ti|IrO₂-SnO₂-Sb₂O₃. The purpose is enhancing the chemical stability and prolonging the electrode lifetime. The Pechini concept was used to this material, but with the advantage that no chloride precursors were employed [3]. Cyclic voltammetry (CV), X-ray diffraction (DRX), Energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) were used to characterize the as-prepared electrode. The electrocatalytic properties were evaluated by electrochemical degradation of tartrazine in aqueous media as well as dibenzothiophene in organic media. Results showed that noncracked oxide layers were obtained and that the electrode has a great capability for the electrochemical degradation of both molecules. Keywords: DSA electrode, Ti|IrO₂-SnO₂-Sb₂O₃, tartrazine, dibenzothiophene X. Chen, G. Chen, Anodic oxidation of dyes at novel Ti/B-diamond electrodes, Chem. Eng. Sci. 58 (2003) 995. X. Chen, G. Chen, F. Gao, P. Yue, High-performance Ti/BDD electrodes for pollutant oxidation, Environ. Sci. Technol. 37 (2003) 5021. M. H. P. Santana, L. M. Da Silva, L. A. De Faria, (2003). Investigation of Surface Properties of Ru-Based Oxide Electrodes Containing Ti, Ce and Nb. Electrochim. Acta, 48 (13), 1885.

Because of the intensive use of pharmaceutical substances in human life, studies on the detection of these chemical compounds and their metabolites as pollutants in water bodies are continuously reported. Some pharmaceutical agents are associated with adverse effects to aquatic life, even at very low concentrations (ng L⁻¹ to μg L⁻¹). For instance, the presence of antibiotics and hormones has been associated with increasing proliferation of antibiotic resistant pathogens and feminization and masculinization of some aquatic organisms. Currently, new attempts are being made to minimize or fully remove these types of pollutants from aquatic systems to protect the environment and human health. In this regard, physicochemical and biological treatments are among the most promising technologies for the treatment of wastewater containing pharmaceutical pollutants. These treatments are green alternatives for the degradation of hazardous organic compounds into nontoxic by-products. Here, we review some of the physicochemical and biological treatment methods used for the removal of the most extensively used antibiotics and hormones. Enzymatic oxidation, photocatalysis and electrochemical oxidation are described in terms of the aforementioned pharmaceutically active compounds (PhACs). The use of membrane technologies to separate different groups of antibiotics and hormones prior to biologic or physicochemical treatment methods is also addressed.