Green electrochemical sensor for Zn(II) ions detection in human seminal fluid

Blown spun fibers-based colorimetric sensor for detecting trace zinc in seminal fluid

Rapid and accurate analysis of zinc in seminal fluid is an important tool for male infertility diagnosis and forensic investigation of sexual assault. Among the traditional techniques employed for this purpose, colorimetric solid-state sensors offer a simple and efficient alternative for screening this analyte. Herein, we evaluated the feasibility of using solution blow spinning as a fast, simple, and cost-effective method to develop porous membranes that can be manufactured as low-cost colorimetric solid-state sensing materials. Specifically, we report a one-step approach to prepare blown spun polylactic acid (PLA)/poly(ethylene oxide) (PEO) fibrous membranes modified with 1-(2-pyridylazo)-2-naphthol (PAN) for the quantitative and qualitative screening of Zn2+ in human seminal fluid. The fibrous membranes were fully characterized and then used to prepare discs and swabs. By digital image colorimetry, a spot-like assay was established using PLA/PEO@PAN membrane discs, which under optimized conditions, exhibited a linear range of up to 15 mg L-1, a limit of detection of 0.06 mg L-1 and high selectivity in the presence of several interfering species commonly found in seminal fluid. Additionally, the sensor was successfully applied in the detection of Zn2+ in human semen samples, showing no significant differences compared to the standard method. Furthermore, PLA/PEO@PAN swabs were employed in a naked-eye presumptive test to identify semen stains, showing satisfactory visual response even in the presence of only 0.11 μg of zinc. Moreover, the swabs' color changes were highly unambiguous, revealing a concordance rate of almost 90% in a blind study. This outstanding performance can be ascribed to the high porosity and wettability of the fibrous membrane and the PAN's coordination ability towards Zn2+. Overall, the remarkable advantages achieved with our approach lie in the easy production, on-site, and cost-effective analysis of zinc as a biomarker for clinical and forensic applications.

Electrochemically reduced graphene oxide integrated with carboxylated-8-carboxamidoquinoline: A platform for highly sensitive voltammetric detection of Zn(II) ion by screen-printed carbon electrode

Zinc has been demonstrated to boost immune response during SAR-CoV-2 infection, where it prevents coronavirus multiplication. Clinical investigations have testified to its beneficial effects on respiratory health and its deficiency may reduce immune function. A highly sensitive detection of Zn(II) ion via differential pulse voltammetry (DPV) utilizing an environmentally friendly modified screen-printed carbon electrode (SPCE) of electrochemically reduced graphene oxide (ErGO) embedded with carboxylated-8-carboxamidoquinoline (CACQ) as Zn(II) chelating ligand. The green CACQ/ErGO-modified SPCE was characterized by spectroscopy techniques, such as Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, and field-emission scanning electron microscopy with energy dispersive X-ray (FESEM-EDX). The modified electrode-solution interface was studied by electrochemical cyclic voltammetry (CV) and DPV methods. The CACQ-modified wrinkled ErGO electrode conferred a large surface-to-volume ratio with multiple binding sites resulting in greater opportunity for multiple dative covalent binding events with Zn(II) via coordination chemistry, and considerably accelerated the electron transfer rate at the electrode surface. The green Zn(II) sensor demonstrated a quick response time (60 s), broad linear range [1 pM-1 μM Zn(II) ion], a limit of detection (LOD) of 0.53 pM, 35 days of storage period (≥80% of its initial response retained), good reproducibility [relative standard deviation (RSD) = 3.4%], and repeatability (RSD = 4.4%). The developed electrode was applied to determine Zn(II) ion concentration in dietary supplement samples, and the results were in good agreement with those obtained from inductively coupled plasma-mass spectrometry (ICP-MS).

Measurement of Zinc Ions in Seawater Samples Using a Microfluidic System Based on the GR/CeO2/Nafion Material

Considering that heavy-metal contamination of seawater is getting worse, building a quick, accurate and portable device for detecting trace zinc in seawater in real time would be very beneficial. In this work, a microfluidic system was developed that includes a planar disc electrode, a micro-cavity for detection, an electrochemical workstation, a computer, a container for waste liquid reprocessing, an external pipeline and other components as well as a graphene/cerium oxide/nano-cerium oxide/Nafion composite membrane was used to modify the planar disc electrode (GR/CeO2/Nafion/Au) to investigate the electrochemical behaviour of Zn(II) using cyclic voltammetry, square-wave voltammetry and orthogonal test methods. Under optimal experimental conditions, the peak reaction current of Zn(II) showed a good linear relationship with the concentration of Zn(II) in the range of 1-900 μg/L with a correlation coefficient of 0.998, and the detection limit of the method was 0.87 μg/L. In addition, the microfluidic system had good stability, reproducibility and anti-interference. The system was used for determining zinc ions in real seawater samples, and the results were very similar to those of inductively coupled plasma-emission spectrometry, demonstrating the practicality of the system for the detection of trace zinc.

Electropolymerization of poly(phenol red) on laser-induced graphene electrode enhanced adsorption of zinc for electrochemical detection

We present a highly sensitive and selective electrode of laser-induced graphene modified with poly(phenol red) (P(PhR)@LIG) for measuring zinc nutrition in rice grains using square wave anodic stripping voltammetry (SWASV). The physicochemical properties of P(PhR)@LIG were investigated with scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), Fourier infrared spectroscopy (FT-IR) and Raman spectroscopy. The modified electrode demonstrated an amplified anodic stripping response of Zn2+ due to the electropolymerization of P(PhR), which enhanced analyte adsorption during the accumulation step of SWASV. Under optimized parameters, the developed sensor provided a linear range from 30 to 3000 μg L-1 with a detection limit of 14.5 μg L-1. The proposed electrode demonstrated good reproducibility and good anti-interference properties. The sensor detected zinc nutrition in rice grain samples with good accuracy and the results were consistent with the standard ICP-OES method.

Rapid Near-Patient Impedimetric Sensing Platform for Prostate Cancer Diagnosis

With the global escalation of concerns surrounding prostate cancer (PCa) diagnosis, reliance on the serologic prostate-specific antigen (PSA) test remains the primary approach. However, the imperative for early PCa diagnosis necessitates more effective, accurate, and rapid diagnostic point-of-care (POC) devices to enhance the result reliability and minimize disease-related complications. Among POC approaches, electrochemical biosensors, known for their amenability and miniaturization capabilities, have emerged as promising candidates. In this study, we developed an impedimetric sensing platform to detect urinary zinc (UZn) in both artificial and clinical urine samples. Our approach lies in integrating label-free impedimetric sensing and the introduction of porosity through surface modification techniques. Leveraging a cellulose acetate/reduced graphene oxide composite, our sensor's recognition layer is engineered to exhibit enhanced porosity, critical for improving the sensitivity, capture, and interaction with UZn. The sensitivity is further amplified by incorporating zincon as an external dopant, establishing highly effective recognition sites. Our sensor demonstrates a limit of detection of 7.33 ng/mL in the 0.1-1000 ng/mL dynamic range, which aligns with the reference benchmark samples from clinical biochemistry. Our sensor results are comparable with the results of inductively coupled plasma mass spectrometry (ICP-MS) where a notable correlation of 0.991 is achieved. To validate our sensor in a real-life scenario, tests were performed on human urine samples from patients being investigated for prostate cancer. Testing clinical urine samples using our sensing platform and ICP-MS produced highly comparable results. A linear correlation with R2 = 0.964 with no significant difference between two groups (p-value = 0.936) was found, thus confirming the reliability of our sensing platform.

Recent advances in the modification of electrodes for trace metal analysis: a review

This review paper summarizes the research published in the last five years on using different compounds and/or materials as modifiers for electrodes employed in trace heavy metal analysis. The main groups of modifiers are identified, and their single or combined application on the surface of the electrodes is discussed. Nanomaterials, film-forming substances, and polymers are among the most used compounds employed mainly in the modification of glassy carbon, screen-printed, and carbon paste electrodes. Composites composed of several compounds and/or materials have also found growing interest in the development of modified electrodes. Environmentally friendly substances and natural products (mainly biopolymers and plant extracts) have continued to be included in the modification of electrodes for trace heavy metal analysis. The main analytical performance parameters of the modified electrodes as well as possible interferences affecting the determination of the target analytes, are discussed. Finally, a critical evaluation of the main findings from these studies and an outlook discussing possible improvements in this area of research are presented.

Ultra-sensitive detection of multiplexed heavy metal ions by MOF-derived carbon film encapsulating BiCu alloy nanoparticles in potable electrochemical sensing system

In this work, we report the development of a new type of highly active and stable Bi-based electrode material, i.e., BiCu metal-organic frames (MOF) derived carbon film (CF) encapsulating BiCu alloy nanoparticles (BiCu-ANPs) for electrochemical sensing. The integration of Bi with Cu to form BiCu-ANPs can improve their electrocatalytic activity as well as the acid resistance. Meanwhile, the carbon film that encapsulates BiCu-ANPs not only guarantees the BiCu-ANPs with high electrical conductivity and fast electrochemical kinetics but also effectively alleviates the volume change during the adsorption and desorption of heavy metal (HM) ions. Therefore, the as-obtained CF encapsulating BiCu-ANPs (BiCu-ANPs@CF) exhibits fully exposed active sites, facile charge transfer, high stability and conductivity, which gives rise to enhanced sensitivity and stability for the electrochemical detection of HM ions. When integrated into a potable electrochemical sensing system for simultaneous detection of Pb²⁺, Cd²⁺ and Zn²⁺, the BiCu-ANPs@CF modified electrode exhibits low detection limit (i.e., 0.081 ppb for Pb²⁺, 0.95 ppb for Cd²⁺, 35 ppb for Zn²⁺), wide detection range (i.e., 0.5-700 ppb for Pb²⁺, 5-900 ppb for Cd²⁺, 150-600 ppb for Zn²⁺) and good anti-interference. Finally, the system has been used for on-site detection of multiplexed HM ions in human biological liquids and environmental water with a good spiked recovery rate, which demanstrates its promise application in the future for on-site monitoring of human health and pollutants in water quality.

Zincon-Modified CNTs Electrochemical Tool for Salivary and Urinary Zinc Detection

Recently, the abnormal level of zinc emerged as a powerful indicator or risk factor for metabolic, endocrine, neurodegenerative and cardiovascular diseases, including cancer. Electrochemical detection has been explored to quantify zinc in a precise, rapid, and non-expensive way; however, most of the current electrochemical systems lack in specificity. In this work we studied a highly selective and sensitive electrochemical method to detect quickly and reliably free zinc ions (Zn²⁺). The surface of the working electrode was modified with zincon electropolymerized on carbon nanotube (CNT) to enable the binding of zinc in complex body fluids. After being physicochemically characterized, the performances of the zincon-CNT complex was electrochemically assessed. Square Wave Voltammetry (SWV) was used to determine the calibration curve and the linear range of zinc quantification in artificial saliva and urine. This zincon- CNT system could specifically quantify mobile Zn²⁺ in salivary and urinary matrices with a sensitivity of ~100 ng·mL^-1 and a limit of detection (LOD) of ~20 ng·mL^-1. Zincon-modified CNT presented as a desirable candidate for the detection and quantification of free zinc in easily body fluids that potentially can become a diagnostic non-invasive testing platform.