Rheumatoid arthritis (RA) is a systemic chronic autoimmune inflammatory disease that is characterized by the destruction of bone and production of autoantibodies such as rheumatoid factor (RF) and anticitrullinated protein antibodies (ACPAs). The high prevalence of this disease and the need of affordable tools for its early detection led us to prepare the first electrochemical immunoplatform for the simultaneous determination of four RA biomarkers, the autoantibodies: RF, anti-peptidyl-arginine deiminase enzyme (anti-PAD4), anti-cyclic citrullinated peptide (anti-CCP), and anti-citrullinated vimentin (anti-MCV). Functionalized magnetic beads (MBs) were used to immobilize the specific antigens, and sandwich-type immunoassays were implemented for the amperometric detection of the four autoantibodies, using the horseradish peroxidase (HRP)/H₂O₂/hydroquinone (HQ) system. The immunoplatform was applied to the determination of the biomarkers in human serum of twenty-two patients diagnosed with RA and four healthy individuals, and the results were validated against ELISA tests and the certified values.

Glaucoma is a leading cause of irreversible blindness worldwide, with its asymptomatic progression highlighting the urgent need for early, minimally invasive biomarkers. Exosomes derived from the aqueous humor (AH) have emerged as promising candidates, as they carry proteins, nucleic acids, and lipids that reflect the physiological and pathological state of ocular tissues such as the trabecular meshwork and ciliary body. However, their low abundance, nanoscale size, and the limited volume of AH complicate detection and characterization. Conventional methods, including Western blotting, PCR or mass spectrometry, are labor-intensive, time-consuming, and often incompatible with microliter-scale samples. Electrochemical biosensors offer a highly sensitive, rapid, and low-volume alternative, enabling the detection of exosomal surface markers and internal cargos such as microRNAs, proteins, and lipids. Recent advances in nanomaterial-enhanced electrodes, microfluidic integration, enzyme- and nanozyme-mediated signal amplification, and ratiometric detection strategies have significantly improved sensitivity, selectivity, and multiplexing capabilities. While most studies focus on blood or serum, these platforms hold great potential for AH-derived exosome analysis, supporting early-stage glaucoma diagnosis, monitoring of disease progression, and evaluation of therapeutic responses. Continued development of miniaturized, point-of-care electrochemical biosensors could facilitate clinically viable, noninvasive exosome-based diagnostics for glaucoma.

Circulating tumour cells (CTC) are rare cells shed from primary and metastatic tumours into the bloodstream, representing a minimally invasive source of information on tumour biology, dissemination, and therapeutic resistance. Their detection, isolation, and characterisation have emerged as critical tools for precision oncology, serving as robust prognostic and predictive biomarkers that reflect metastatic potential, treatment response, and overall survival. CTC isolation and analysis are challenging due to their extremely low frequency-often one cell per million blood cells-and their phenotypic heterogeneity. Current strategies include enrichment-based methods, exploiting physical or molecular properties for selective capture, and non-enrichment approaches, which preserve cellular integrity for downstream molecular, functional, and imaging analyses. Key performance metrics for isolation platforms include capture efficiency, enrichment, purity, throughput, recovery, and cell viability. Validation often relies on spiked cell lines, though these models may overestimate performance compared with heterogeneous patient-derived CTCs. Integrative approaches combining multiple methodologies are essential to fully characterize CTC populations and overcome individual limitations. Technological advances, including microfluidics, single-cell sequencing, and artificial intelligence-driven analysis, have enhanced the sensitivity and specificity of CTC detection, enabling comprehensive molecular and functional profiling. The FDA-approved CellSearch® system remains the clinical gold standard, primarily in metastatic disease, but emerging platforms aim to enable early detection, real-time disease monitoring, and the identification of subpopulations with high metastatic potential. Future directions in CTC research focus on early cancer detection, longitudinal monitoring of therapeutic response, and personalized treatment adaptation. Integration with other circulating biomarkers, such as circulating tumour DNA and exosomes, promise enhanced prognostic and diagnostic accuracy. Standardization of protocols and validation in clinical samples will be critical for translating these technologies into routine oncology practice.

Fibromyalgia (FM) is a complex chronic syndrome marked by widespread musculoskeletal pain, neurocognitive dysfunction (“fibro-fog”), and autonomic disturbances. Clinical management remains challenging due to subjective symptom reporting and the lack of definitive diagnostics. Emerging evidence points to a multifactorial origin involving central sensitization, neuroendocrine imbalance, and systemic immune-inflammatory alterations. A wide array of candidate biomarkers has been reported in FM, encompassing neurotransmitters (serotonin, norepinephrine), excitatory and inhibitory amino acids, metabolic and glycolytic enzymes, stress-related proteins, autoantibodies, oxidative stress markers and pro-inflammatory cytokines. This molecular heterogeneity reflects the systemic and multidimensional nature of FM. However, most of these biomarkers have been primarily investigated in serum or plasma, where analytical validation and reference ranges are more established. In contrast, the exploration of salivary biomarkers—although highly attractive due to its non-invasive, stress-free, and repeatable collection—remains comparatively limited. Saliva contains a reduced concentration range of many systemic markers and is strongly influenced by circadian rhythms, stress, flow rate, and oral health conditions. While promising candidates such as α-amylase, cortisol, calgranulins, and selected metabolic enzymes have shown potential in saliva, many proposed FM-related biomarkers lack full analytical validation, standardized protocols, and clinically defined reference intervals in this matrix. In this context, non-invasive electrochemical biosensors represent a transformative technological approach. Advanced electrode architectures incorporating nucleic acid probes, redox reporters, and nanostructured materials offer high sensitivity in low-volume and low-concentration biofluids such as saliva. The integration of multiplexed biomarker panels into portable platforms could enable real-time, longitudinal monitoring of FM pathophysiology, supporting phenotype stratification, personalized therapeutic adjustment, and objective disease activity tracking.

Alterations in the expression of the Klotho gene have been associated with chronic kidney disease (CKD), and its potential as an early diagnostic biomarker is currently under active investigation. In this work, we report the development of a highly sensitive, label-free electrochemical DNA-based biosensor for the detection of a 100 mer DNA fragment corresponding to a partial region of Klotho mRNA. The proposed bioplatform integrates mixed self-assembled monolayers (SAMs) and gold nanoparticles for efficient DNA immobilization within a sandwich-type configuration, coupled with impedimetric detection. Different SAM architectures were evaluated by cyclic voltammetry and electrochemical impedance spectroscopy, with the binary monolayer composed of 1-hexadecanethiol (HDT) and the capture probe (CP) exhibiting the best analytical performance. The use of gold nanoparticle-modified screen-printed carbon electrodes (AuNPs–SPCEs) resulted in a 1.4-fold increase in the signal-to-noise ratio compared to screen-printed gold electrodes. Additionally, the incorporation of a blocking step using bovine serum albumin (BSA–HDT–CP–AuNPs–SPCE) enhanced the sensitivity by 1.6-fold compared to the unblocked system. The genosensor displayed a linear response in the concentration range of 3 × 10⁻¹⁰ to 7.5 × 10⁻⁸ M, achieving a detection limit of 0.09 nM. Relative standard deviations below 7.5% were obtained for different Klotho concentrations, confirming high intra-assay and intermediary precision. Selectivity assays demonstrated negligible signals for non-complementary sequences, while recovery experiments in spiked human serum samples yielded satisfactory values between 96.5% and 103.4%.

The reliable detection of the peanut allergen Ara h2 in processed foods remains a major challenge, since thermal and high-pressure treatments can alter protein structure and limit the performance of immunoassays. DNA-based methods provide a robust alternative to this approach. In this work, a highly sensitive label-free electrochemical genoassay for Ara h2 DNA detection was developed using streptavidin-coated magnetic beads (MBs). A biotinylated capture probe (CP) immobilized on the MBs’ surface enabled specific target recognition through a sandwich hybridization strategy with a secondary probe, allowing for direct electrochemical detection without enzymatic labels. Two transduction strategies were evaluated: (i) electrochemical impedance spectroscopy (EIS) with ferri/ferrocyanide as a redox probe, and (ii) differential pulse voltammetry (DPV) using methylene blue. The ferri/ferrocyanide-based EIS approach showed the best sensitivity and discrimination between hybridized and non-hybridized states. A linear dependence was observed with the concentration of the synthetic Ara h2 target over the 0.05 to 20 nM range, with a detection limit of 0.025 nM. CP-MBs showed good stability for at least 20 days. Applicability was demonstrated in soy beverages, rice beverages, and low-fat cow’s milk, with recoveries close to 100% and negligible matrix effects.