Cellulose is one of the most abundant biopolymers, and its many properties make it suitable for application in numerous fields, such as sensor and biosensor fabrication. It is indeed biodegradable and renewable, nontoxic, biocompatible, and widely available at low cost (https://doi.org/10.3390/chemosensors10090352). In addition, cellulose boasts different structural arrangements such as Cellulose Nanocrystals (CNCs), which are among the most promising cellulose-derived nanomaterials for applications in biosensors. In fact, CNCs can be formulated into thin films to be used as support material for the immobilization of proteins (enzymes, antibodies, etc.) (https://doi.org/10.3390/chemosensors10090352, https://doi.org/10.1016/j.sbsr.2020.100368). In this work, we exploited antibody-functionalized CNCs to develop a microfluidic paper-based analytical device (µPAD) for the detection of myeloperoxidase blood levels, which have been shown to be altered in patients with Alzheimer's disease (AD) (https://doi.org/10.5539/gjhs.v6n5p87, https://doi.org/10.1111/j.1471-4159.2004.02527.x, https://doi.org/10.1016/j.arr.2020.101130). In particular, upon their covalent functionalization with anti-myeloperoxidase antibody, CNCs were deposited onto filter paper, thus providing a uniform and stable functionalized layer. Subsequently, employing the origami format, myeloperoxidase contained in the sample was captured by the immobilized antibody and then detected, exploiting its ability to catalyse the luminol/hydrogen peroxide chemiluminescence reaction. Emitted photons were detected by employing a portable highly sensitive charge-coupled device (CCD) camera and analyzed to obtain quantitative information. A limit of detection of 5.8 ng/mL was obtained, which enables clear distinction between healthy and AD patients’ myeloperoxidase blood levels (https://doi.org/10.3233/jad-131469). In addition, the selectivity of the system was evaluated by testing the possible interference of haemoglobin, which is also able to catalyse the chemiluminescence reaction. In the future, the same approach will be used for developing origami µPADs for detecting other AD biomarkers exploiting chemiluminescence sandwich immunoassays.

This research is supported by the PRIN2022 project 2022WN89PC “Biomimetic sensing platforms for the detection of Alzheimer's disease related biomarkers”.

Formaldehyde in exhaled human breath serves as a pivotal biomarker for the detection of nasal cancer. In the context of nasal cancer, the non-invasive detection of formaldehyde, which is a primary biomarker, using a chemiresistive sensor has gained significant attention. However, selectivity and sensitivity are still challenges. This study focuses on a non-invasive Bi₂O₃ porous nanosheet-based chemiresistor for the detection of nasal cancer via exhaled human breadth. Here, a Bi₂O₃ porous nanosheet was synthesized using a one-step hydrothermal approach. Rietveld refinement analysis confirmed its polycrystalline nature. The gas sensing properties of the Bi₂O₃ porous nanosheet towards formaldehyde were studied via a static system in a range of 1-20 ppm at a temperature of 100℃. The Bi₂O₃ chemiresistor showed 8.53 sensor response at 1 ppm, with fast response and recovery times of 2.74 s and 4.64 s, respectively. The enhanced sensor response of Bi₂O₃ was attributed to the formation of a porous nanosheet with higher active sites and a large surface area of 60.95 m²g^-1. The N₂ adsorption–desorption isotherm confirmed that a type-II isotherm exists and the mesoporous structure had a mean pore diameter of 60.73 nm. The Bi₂O₃ chemiresistor is highly selective towards formaldehyde compared to other VOCs. Furthermore, exhaled human breadth was used for the detection of nasal cancer in static conditions. The sensor's response values were higher for the breath of diabetic patients, indicating its potential for use in nasal cancer monitoring and clinical diagnosis.

Xanthomonas oryzae pv. oryzae (Xoo) is a pervasive bacterial pathogen with global implications, causing bacterial blight in rice and threatening food security. The effective management of Xoo diseases in field conditions, protected farm operations, and international borders relies heavily on the early detection of Xoo. Traditional detection methods, including immunological assays such as direct tissue blot immunoassays (DTBIA) and enzyme-linked immunosorbent assays (ELISA), as well as molecular techniques like loop-mediated isothermal amplification (LAMP) and polymerase chain reaction (PCR), are commonly employed for pathogen identification. However, these methods often require sophisticated instrumentation and trained personnel, resulting in time-consuming and resource-intensive processes that are unsuitable for on-site analysis. To overcome these challenges, we have developed a sensitive electrochemical biosensor for Xoo detection by exploiting the unique properties of a core nano assembly of gold nanoparticles. The biosensor incorporates a specific DNA probe designed based on the PthXo1 gene, a prominent virulence factor of Xoo. This probe is immobilized on the electrode surface, enabling sequence-specific hybridization and subsequent electrochemical transduction for the sensitive and rapid detection of Xoo up to the 1fg/µl level.¹ This innovative approach holds promise for monitoring Xoo, thereby contributing to the development of effective disease management strategies and the preservation of global food security.

An innovative approach was employed to develop composite membranes conducive to the production of advanced electrodes for electrochemical applications based on laser-induced graphene. This technique is based on the laser synthesis of graphene-based nanomaterials, specifically laser-induced graphene and reduced graphene oxide. The synthesis of these materials was performed using CO2 laser (10 mm). Direct laser writing of graphene is commonly used on solid surfaces based on polyimide, polyether sulfone and polyether ether ketone, which are widely used in many applications, including electrochemical processing , water desalination and fuel cells.

Herein, LIG was successfully synthesized on composite membranes composed of amino-functionalized polyether sulfone and carbon black. Comprehensive characterization of the prepared composite membranes and electrodes was carried out, employing various techniques such as Fourier transform infrared spectroscopy, scanning electron microscopy and thermogravimetric analysis, as well as cyclic voltammetry and Nyquist diagrams, to evaluate their surface morphology and thermal stability. The electrochemical performance of laser-induced graphene electrodes (LIGEs) demonstrated substantial enhancements in comparison to the pristine NH2-PES membrane. After optimizing the laser writing parameters for these novel composite membranes, their performance as electrodes was evaluated. Specifically, gold nanoparticle-modified LIG electrodes (AuNPs/LIG) were successfully employed for the electrochemical detection of dopamine (DA), demonstrating the potential of these materials in sensor applications.

Introduction: The improper use of nitrite ions and the widespread presence of antibiotics like kanamycin in food products pose significant risks to human health. To address these challenges, we developed two advanced electrochemical sensing platforms using laser-induced graphene (LIG) electrodes for sensitive and selective detection of these contaminants.

Methods: For nitrite detection, LIG electrodes were modified with an electrochemically deposited melanin-like film (MeLF), leveraging its redox-active catechol and o-quinone moieties. Redox capacitance spectroscopy was employed as a probe-free detection method. For kanamycin detection, LIG electrodes were functionalized with gold nanoparticles and a kanamycin-specific aptamer. Non-faradaic capacitance measurements were utilized to detect interactions between aptamer and kanamycin. Both sensors were characterized electrochemically and validated in real sample matrices.

Results: The MeLF-modified LIG sensor exhibited enhanced electron transfer kinetics, an increased electroactive surface area, and improved charge capacitance. It detected nitrite ions with a limit of detection of 2.45 μM and a dynamic range of 10 μM to 10 mM, achieving high recovery rates in water and processed meat samples. The aptamer-functionalized LIG sensor demonstrated a proportional increase in non-faradaic capacitance with kanamycin concentration, achieving a linear range from 100 fg/mL to 10 µg/mL, with successful real-time application in milk samples.

Conclusions: These novel sensing platforms demonstrate the versatility of modified LIG electrodes in electrochemical sensing. The combination of redox-active films and aptamer-based recognition elements with capacitive detection offers promising solutions for food safety monitoring and environmental analysis, providing sensitive, reliable, and practical analytical tools for real-world applications.

Introduction

Different device technologies (solar cells, capacitors, transistors, etc.) have been thoroughly explored using various inorganic materials (Si, GaAs, metal oxides, etc.). Though these inorganic materials are known for providing efficient performance due to their robust electrical, optical, thermal, and mechanical properties, their high cost, toxicity, biodegradability, and biocompatibility issues have remained a major roadblock for their widespread applications, particularly in biological systems. Thus, there is a need worldwide to search for organic, low-cost, biocompatible, biodegradable, and functional materials which could serve as an alternative to the materials in current use for sustainable applications in the field of materials science. Focusing on the natural resources which are available abundantly and making use of these could offer exciting opportunities for researchers.

Methods

Recently, the isolation of a new humic acid from the soil of Gwal Pahari, Gurgaon, Haryana, India, has been reported from our lab. This water-soluble, fluorescent, and ninhydrin-positive Gwal Pahari Acid (GPA) has been characterized using modern spectroscopic techniques, e.g., UV–visible spectroscopy, Fourier-Transform Infrared Spectroscopy (FT-IR), mass spectrometry, ¹H- NMR and 2D-NMR studies, Scanning Electron Microscopy, and Zeta Potential.

Results and Conclusions

GPA is predicted to form supramolecular self-assemblies which could help in chelating different metal ions (Fe (III), Pb (II), Co (II), Ni (II), Cu (II), etc.) and phosphate ions. Thus, GPA may serve as a potential candidate for sensing metal ions and could facilitate in curbing the toxic heavy metal contamination found in water bodies. Further, its fluorescent nature can be utilized in the fabrication of a fluorescence-based biosensor where the target analyte could be sensed with changes in the fluorescence signal. Newer technologies based on such materials are not only expected to bring down the costs involved with these technologies but will also help in combating the pressing global environmental issues.

Bisphenol A (BPA), a hazardous endocrine disruptor with strong estrogen-like effects, has raised environmental and health concerns. Therefore, it is crucial to develop an approach that is greener, simpler, cost-effective, flexible, environmentally friendly and efficient for detecting BPA. This work introduces a user-friendly electrochemical sensing platform to detect BPA, utilizing hematite nanoparticles (α-Fe₂O₃NPs) combined with reduced graphene oxide (rGO) on a carbon cloth substrate. Green synthesis, facilitated by Cinnamomum tamala leaf extract, produced α-Fe₂O₃NPs, which were subsequently integrated with graphene oxide to form reduced graphene oxide (rGO), which served as a stabilizing as well as a reducing agent for α-Fe₂O₃NPs. The sensing surface was prepared using electrophoretic deposition, resulting in a nanostructure with superior conductivity and a high surface area, enhancing its electrochemical response on carbon cloth (CC) (i.e., α-Fe₂O₃NPs@rGO/CC) owing to the synergistic effect. The α-Fe₂O₃NPs@rGO/CC sensor exhibited remarkable performance, including a wide detection range (from 1.9 × 10⁻¹⁰ to 1.00 μM), high sensitivity (33.04 μA (log μM)⁻¹ cm⁻²), and the lowest detection limit (0.23 μM), alongside excellent reproducibility, stability, as well as selectivity, ultimately providing satisfying outcomes. Moreover, the sensor was validated using real-world samples, i.e., food and environmental samples confirmed its applicability, paving the way for detecting other similar environmental contaminants.

Given their hazardous effects on the environment and human health, the monitoring of pesticide residues is recognized as the most effective means to guard food and public safety. Oxidoreductase-type nanozymes (peroxidase and oxidase) have been widely employed to develop optical methods for pesticide detection, but these methods are susceptible to matrix redox interference and lack detection specificity for intended targets. To overcome the above deficiencies, here we designed a novel organophosphorus hydrolase-mimicking nanozyme, namely, nanosized ceria capped by Ca²⁺-chelated 2-aminoterephthalic acid (Ca-ATPA@CeO₂) featuring stable fluorescence and dual-site-empowered high catalytic activity, to enable the exclusive dual-mode detection of hypertoxic methyl-paraoxon (MP). The synergy of hard Lewis acid Ca²⁺ and nanoceria creates dual active sites that jointly promote the binding and hydrolysis of MP to yellow p-nitrophenol (pNP) specifically. Meanwhile, the generated pNP quenches the intrinsic fluorescence of Ca-ATPA@CeO₂ via the inner filter effect. As a result, dual-mode colorimetric and fluorescence determination of MP was achieved using the designed versatile nanozyme. The alliance of excellent target catalytic specificity and bimodal cross-check characteristic enables accurate quantification of the individual pesticide in complex matrices. Our work introduces a new reliable strategy for MP selective detection that can avoid potential interference from redox substances.

Effective therapeutic drug monitoring (TDM) is crucial for optimizing chemotherapy efficacy and minimizing toxicity, especially with potent anticancer drugs like doxorubicin and cyclophosphamide. Traditional TDM practices often rely on centralized laboratory testing, which can suffer from lengthy turnaround times that delay clinical decision-making. To address these limitations, this study aims to develop and validate a novel electrochemical sensor capable of rapid, onsite TDM at the point of care. We have designed a cutting-edge electrochemical sensor utilizing an MXene-modified glassy carbon electrode (GCE) as the working electrode. The choice of MXene was intended to enhance the electrode's sensitivity and selectivity for the targeted detection of doxorubicin and cyclophosphamide. The preliminary results demonstrate that the sensor can detect these drugs within clinically relevant concentration ranges, with a detection limit ranging from 1.10^-4 to 10.10^-4 M. Furthermore, the sensor's performance has been successfully validated by testing blood samples from patients undergoing chemotherapy, confirming that the measurements are both accurate and reliable. The development of this electrochemical sensor marks a significant advancement in the field of TDM, reducing dependence on centralized laboratories and streamlining the monitoring process. This innovative tool not only holds the potential for improving patient outcomes by ensuring optimal drug dosages but also offers possibilities for expanding its applications to monitor other anticancer drugs and immune biomarkers in the future.

Abstract

Introduction: Non-enzymatic electrochemical sensors are crucial in biomedical applications, especially for the real-time monitoring of lactate concentrations in biological fluids such as saliva. In this work, NiO-coated stacked-cut carbon nanotube (NiO/SCCNT) nanocomposites were fabricated via atomic layer deposition (ALD) to enhance lactate-sensing performance.

Methods: Carbon nanotubes (CNTs) were coated with NiO of varying thicknesses (0, 50, 200, and 700 ALD cycles) to form core–shell nanocomposites. These were then integrated into screen-printed carbon electrodes (SPCEs) for non-enzymatic lactate detection. Electrochemical experiments, i.e., cyclic voltammetry (CV), chronoamperometry, and electrochemical impedance spectroscopy (EIS), were carried out to characterize the sensor properties.

Results: Compared with bare SPCE, the NiO(x)/CNT-modified electrode presented a marked decrease in charge transfer resistance, indicating significantly improved electron transfer. The NiO thickness influenced the electrochemical response, with 200 ALD cycles exhibiting the most favourable characteristics. In the 0–4 mM range, the optimized composite achieved a sensitivity of 138.44 μAmM⁻¹cm⁻² and a limit of detection (LOD) of 0.067 mM (S/N = 3). Excellent sensitivity, selectivity, stability, and reproducibility supported the rapid and accurate detection of lactate in real salivary samples.

Conclusions: NiO-coated CNT nanocomposites demonstrate high potential as non-enzymatic lactate sensors for saliva-based measurements. They deliver strong electrochemical performance, low LOD, and high sensitivity, highlighting their suitability for real-time lactate monitoring in biomedical applications.