Rafaela Cristina de Freitas

The increasing impact of infectious, cardiovascular and neurodegenerative diseases has intensified the demand for early and decentralized diagnostics. Label-free electrochemical biosensors are promising candidates, offering high sensitivity, low reagent consumption and miniaturizable, low-cost architectures for point-of-care (PoC) testing. This review summarizes advances in immobilization strategies, recognition elements such as DNA, antibodies, aptamers, and molecularly imprinted polymers, as well as electrode platforms including glassy carbon, screen-printed, and 3D-printed systems, with an emphasis on DNA biosensors, multiplexed configurations, and applications to disease biomarkers. Beyond analytical performance, we critically examine the barriers that keep most devices at the proof-of-concept stage, including bioreceptor stability and immobilization, limited validation in real samples, reliance on conventional materials, challenges in scalable manufacturing, transport, and storage, and the absence of fully integrated PoC systems. Finally, we discuss significant advances in sensitivity, reproducibility, and application to real samples, but note that translation to real-world use and commercialization remains limited.

Lactic acid is a vital molecule for health and food quality control. Its detection, typically via L-lactate, is a valuable indicator for conditions like disease, product spoilage, and stress. Electrochemical biosensors offer a promising, user-friendly solution for lactate detection. These versatile devices allow for tailored surfaces, adapting to sample characteristics, detection mechanisms, and end-user needs. Despite the variety of existing electrochemical biosensor architectures, including microfluidic, wearable, paper-based, carbon-based, and glassy carbon electrode types, routine lactate analysis with these devices remains a significant challenge. This work will explore diverse electrochemical lactate biosensors, detailing their designs, modifications, common transducers, analyzed samples, and validation. We will also survey commercially available options. Finally, this review assesses the current commercialization status and future perspectives of these biosensors, highlighting their growing importance in clinical and industrial applications.

This study presents an electrochemical sensor developed from a glassy carbon electrode modified with nanodiamond film (ND/GCE). This electrochemical response of the proposed sensor was improved, and it showed excellent analytical performance for the detection of paracetamol (PAR), which was attributed to the high PAR charging capacity on the electrode surface and the excellent electrical conductivity of ND. Morphological and electrochemical characterizations of the sensor were performed via scanning electron microscopy (SEM) and cyclic voltammetry using a redox probe [Fe(CN)₆]³⁻. The sensor was applied for the determination of PAR. Quantification was performed using square-wave voltammetry, and it showed a linear concentration range from 0.79 to 100 µmol L⁻¹, with a limit of detection of 0.18 µmol L⁻¹. The proposed sensor exhibited satisfactory repeatability and high sensitivity in the determination of the analyte of interest. The electrochemical sensor was also employed for the analysis of PAR in real samples, with recovery rates ranging between 96.4 and 98.7%. This sensor was successfully used for the determination of the drug in pharmaceutical samples.