Multiwalled Carbon Nanotubes-CeO2 Nanorods: A "Nanonetwork" Modified Electrode for Detecting Trace Rifampicin

Chemically engineered unzipped multiwalled carbon nanotube and rGO nanohybrid for ultrasensitive picloram detection in rice water and soil samples

Picloram (4-Amino-3,5,6-trichloro pyridine-2-carboxylic acid) is a chlorinated herbicide that has been discovered to be tenacious and relatively durable in both soil and water. It is known to have adverse and unpleasant effects on humans causing several health complications. Therefore, the determination of picloram is profoundly effective because of its bio-accumulative and persistent nature. Because of this, a sensitive, rapid, and robust detection system is essential to detect traces of this molecule. In this study, we have constructed a novel nanohybrid system comprising of an UZMWCNT and rGO decorated on AuNPs modified glassy carbon electrode (UZMWCNT + rGO/AuNPs/GCE). The synthesized nanomaterials and the developed system were characterized using techniques such as SEM, XRD, SWV, LSV, EIS, and chronoamperometry. The engineered sensor surface showed a broad linear range of 5 × 10^-2 nM to 6 × 10⁵ nM , a low limit of detection (LOD) of 2.31 ± 0.02 (RSD < 4.1%) pM and a limit of quantification (LOQ) of 7.63 ± 0.03 pM. The response time was recorded to be 0.2 s, and the efficacy of the proposed sensor system was studied using rice water and soil samples collected from the agricultural field post filtration. The calculated recovery % for picloram in rice water was found to be 88.58%-96.70% (RSD < 3.5%, n = 3) and for soil it was found to be 89.57%-93.24% (RSD < 3.5%, n = 3). In addition, the SWV responses of both the real samples have been performed and a linear plot have been obtained with a correlation coefficient of 0.97 and 0.96 for rice and soil samples, respectively. The interference studies due to the coexisting molecules that may be present in the samples have been found to be negligible. Also, the designed sensor has been evaluated for stability and found to be highly reproducible and stable towards picloram detection.

State of the Art on Developments of (Bio)Sensors and Analytical Methods for Rifamycin Antibiotics Determination

This review summarizes the literature data reported from 2000 up to the present on the development of various electrochemical (voltammetric, amperometric, potentiometric and photoelectrochemical), optical (UV-Vis and IR) and luminescence (chemiluminescence and fluorescence) methods and the corresponding sensors for rifamycin antibiotics analysis. The discussion is focused mainly on the foremost compound of this class of macrocyclic drugs, namely rifampicin (RIF), which is a first-line antituberculosis agent derived from rifampicin SV (RSV). RIF and RSV also have excellent therapeutic action in the treatment of other bacterial infectious diseases. Due to the side-effects (e.g., prevalence of drug-resistant bacteria, hepatotoxicity) of long-term RIF intake, drug monitoring in patients is of real importance in establishing the optimum RIF dose, and therefore, reliable, rapid and simple methods of analysis are required. Based on the studies published on this topic in the last two decades, the sensing principles, some examples of sensors preparation procedures, as well as the performance characteristics (linear range, limits of detection and quantification) of analytical methods for RIF determination, are compared and correlated, critically emphasizing their benefits and limitations. Examples of spectrometric and electrochemical investigations of RIF interaction with biologically important molecules are also presented.

Strategic orchestration of MoSe2 microspheres on β-cd functionalized rGO: A sustainable electrocatalyst for detection of rifampicin in real samples

The ill effects of prolonged use of rifamycin antibiotics such as rifampicin accentuates its need for detection in the environment as well as in biological fluids. Antibiotics in water and soil are long-lasting, bio-accumulative, and hazardous to aquatic species as well as human health. To address this issue, a sensing platform has been developed using Molybdenum diselenide (MoSe₂) embedded on reduced graphene oxide (rGO) functionalized with β-cyclodextrin (β-cd) polymer. The formation of hybrid composite was validated with X-ray diffraction analysis (XRD), Raman spectroscopy, fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (FE-SEM) with EDX analysis. The formation of microspheres were observed with hexagonal crystal system and P63/mmc space group. Furthermore, the composite was employed to fabricate an efficient electrochemical sensor for detecting the widely used antibiotic, rifampicin (RIF). The results reveal excellent activity of the sensor with a limit of detection (LOD) of 28 nM in a linear working range from 0.019 to 374.5 μM. The sensor also exhibited a high sensitivity of 11.64 μA μM^-1 cm^-2. Additionally, the sensor showed appreciable recovery range when monitored in real-samples such as human serum and urine, and industrial water, and fish samples.

Three-dimensional porous reduced graphene oxide modified electrode for highly sensitive detection of trace rifampicin in milk

Antibiotic overuse poses a serious food safety problem. Therefore, it is of great importance to develop efficient assays that respond to antibiotics to establish early-warning mechanisms. Here, we prepared a three-dimensional (3D) porous reduced graphene oxide (pRGO) modified electrode, which was characterized by scanning electron microscopy and transmission electron microscopy. As a result of the introduction of the 3D pRGO film, the electrocatalytic activity was considerably improved, which could efficiently trigger the redox reaction of rifampicin (RIF). By employing differential pulse voltammetry, the reduction peak current of RIF showed a good linear relationship with the logarithm of the RIF concentration in the range 1.0 × 10^-9 to 1.0 × 10^-7 mol L^-1. The linear equation was i_p (-10^-6 A) = 3.11 + 0.28 log c_RIF (R² = 0.9908) with a detection limit of 2.7 × 10^-10 mol L^-1 (S/N = 3). Additionally, the final electrode displayed long stability, good reproducibility and high selectivity, and could detect trace RIF in milk with satisfactory results. This study reveals the great potential in utilizing 3D pRGO to develop efficient electrochemical sensors for safeguarding food safety.

First Screen-Printed Sensor (Electrochemically Activated Screen-Printed Boron-Doped Diamond Electrode) for Quantitative Determination of Rifampicin by Adsorptive Stripping Voltammetry

In this paper, a screen-printed boron-doped electrode (aSPBDDE) was subjected to electrochemical activation by cyclic voltammetry (CV) in 0.1 M NaOH and the response to rifampicin (RIF) oxidation was used as a testing probe. Changes in surface morphology and electrochemical behaviour of RIF before and after the electrochemical activation of SPBDDE were studied by scanning electron microscopy (SEM), CV and electrochemical impedance spectroscopy (EIS). The increase in number and size of pores in the modifier layer and reduction of charge transfer residence were likely responsible for electrochemical improvement of the analytical signal from RIF at the SPBDDE. Quantitative analysis of RIF by using differential pulse adsorptive stripping voltammetry in 0.1 mol L⁻¹ solution of PBS of pH 3.0 ± 0.1 at the aSPBDDE was carried out. Using optimized conditions (E_acc of −0.45 V, t_acc of 120 s, ΔE_A of 150 mV, ν of 100 mV s⁻¹ and t_m of 5 ms), the RIF peak current increased linearly with the concentration in the four ranges: 0.002–0.02, 0.02–0.2, 0.2–2.0, and 2.0–20.0 nM. The limits of detection and quantification were calculated at 0.22 and 0.73 pM. The aSPBDDE showed satisfactory repeatability, reproducibility, and selectivity towards potential interferences. The applicability of the aSPBDDE for control analysis of RIF was demonstrated using river water samples and certified reference material of bovine urine.