3D-printed carbon black/polylactic acid electrochemical sensor combined with batch injection analysis: A cost-effective and portable tool for naproxen sensing

Exploring the potential of SrTi0.7Fe0.3O3 perovskite/Chitosan nanosheets for the development of a label-free electrochemical sensing assay for determination of naproxen in human plasma samples

Naproxen is a nonsteroidal anti-inflammatory drug used to treat nonrheumatic inflammation, migraine, and gout. Therefore, the determination of naproxen in pharmaceutical and biological samples is of particular importance. In the present work, SrTi0.7Fe0.3O3 perovskite/Chitosan nanosheets were used to modify the surface of a glassy carbon electrode (GCE) for highly sensitive determination of naproxen. To ensure the successful synthesis of the perovskite nanosheets, morphological studies including scanning electron microscopy (SEM), Energy-dispersive X-ray (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) were carried out. The electrochemical investigations of naproxen on the modified surface of GCE were investigated and the limit of detection (LOD) and limit of quantification (LOQ) were acquired 0.50 and 1.67 μM, respectively. Additionally, the linear range (LR) of 1.99-130.84 μM was obtained for the oxidation of naproxen. The obtained results have been proved that the mentioned method is simple, sensitive, and specific with a short analysis time. The dominant analytical features of the designed sensor are possessing a low detection limit, excellent stability, repeatability, and high selectivity in the presence of naproxen. For investigation of the applicability of the designed assay in real sample analysis, human plasma samples have been examined and a recovery index was acquired 95%.

Simultaneous monitoring of amoxicillin and paracetamol in synthetic biological fluids using a 3D printed disposable electrode with a lab-made conductive filament

In this work, we are pleased to present for the first time a 3D-printed electrochemical device using a lab-made conductive filament based on graphite (Gr) and polylactic acid (PLA) polymer matrix for the simultaneous detection of amoxicillin (AMX) and paracetamol (PAR). The sensor was properly characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). Compared to the commercial glassy carbon electrode (GCE), the superior performance of the 3D-Gr/PLA electrode was verified with a 3.8-fold more favored charge transfer. A differential pulse voltammetry (DPV) method was proposed providing a linear working range of 4 to 12 μmol L-1 for both analytes and a limit of detection (LOD) of 0.80 and 0.51 μmol L-1 for AMX and PAR, respectively. Additionally, repeatability studies (n = 5, RSD < 5.7%) indicated excellent precision, and recovery percentages ranging from 89 to 109% when applied to synthetic human urine, saliva, and plasma samples, attested to the accuracy of the method. The studies also indicate that the sensor does not suffer significant interference from common substances (antibiotics and biomarkers) present in the biological fluids, which makes it a promising analytical tool considering its low-cost, ease of manufacturing, robustness, and electrochemical performance.

CO2-plasma surface treatment of graphite sheet electrodes for detection of chloramphenicol, ciprofloxacin and sulphanilamide

Graphite sheet (GS) electrodes are flexible and versatile substrates for sensing electrochemical; however, their use has been limited to incorporate (bio)chemical modifiers. Herein, we demonstrated that a cold (low temperature) CO2 plasma treatment of GS electrodes provides a substantial improvement of the electrochemical activity of these electrodes due to the increased structural defects on the GS surface as revealed by Raman spectroscopy (ID/IG ratio), and scanning electron microscopy images. XPS analyses confirmed the formation of oxygenated functional groups at the GS surface after the plasma treatment that are intrinsically related to the substantial increase in the electron transfer coefficient (K0 values increased from 1.46 × 10-6 to 2.09 × 10-3 cm s-1) and with reduction of the resistance to charge transfer (from 129.8 to 0.251 kΩ). The improved electrochemical activity of CO2-GS electrodes was checked for the detection of emerging contaminant species, such as chloramphenicol (CHL), ciprofloxacin (CIP) and sulphanilamide (SUL) antibiotics, at around + 0.15, + 1.10 and + 0.85 V (versus Ag/AgCl), respectively, by square wave voltammetry. Limit of detection values in the submicromolar range were achieved for CHL (0.08 μmol L-1), CIP (0.01 μmol L-1) and SFL (0.11 μmol L-1), which enabled the sensor to be successfully applied to natural waters and urine samples (recovery values from 85 to 119%). The CO2-GS electrode is highly stable and inexpensive ($0.09 each sensor) and can be easily inserted in portable 3D printed cells for environmental on-site analyses.

3D printed graphite-based electrode coupled with batch injection analysis: An affordable high-throughput strategy for atorvastatin determination

This work integrated a lab-made conductive graphite/polylactic acid (Grp/PLA, 40:60% w/w) filament into a 3D pen to print customized electrodes (cylindrical design). Thermogravimetric analysis validated the incorporation of graphite into the PLA matrix, while Raman spectroscopy and scanning electron microscopy images indicated a graphitic structure with the presence of defects and highly porous, respectively. The electrochemical features of the 3D-printed Gpt/PLA electrode were systematically compared to that achieved using commercial carbon black/polylactic acid (CB/PLA, from Protopasta®) filament. The 3D printed Gpt/PLA electrode "in the native form" provided lower charge transfer resistance (Rct = 880 Ω) and a more kinetically favored reaction (K⁰ = 1.48 × 10^-3 cm s^-1) compared to the 3D printed CB/PLA electrode (chemically/electrochemically treated). Moreover, a method by batch injection analysis with amperometric detection (BIA-AD) was developed to determine atorvastatin (ATR) in pharmaceutical and water samples. Using the 3D printed Gpt/PLA electrode, a wider linear range (1-200 μmol L^-1), sensitivity (3-times higher), and lower detection limit (LOD = 0.13 μmol L^-1) were achieved when compared to the CB/PLA electrode. Repeatability studies (n = 15, RSD <7.3%) attested to the precision of the electrochemical measurements, and recovery percentages between 83 and 108% confirmed the accuracy of the method. Remarkably, this is the first time that ATR has been determined by the BIA-AD system and a low-cost 3D-printed device. This approach is promising to be implemented in research laboratories for quality control of pharmaceuticals and can also be useful for on-site environmental analysis.

Nickel Oxy-Hydroxy/Multi-Wall Carbon Nanotubes Film Coupled with a 3D-Printed Device as a Nonenzymatic Glucose Sensor

A rapid and simple method for the amperometric determination of glucose using a nanocomposite film of nickel oxyhydroxide and multi-walled carbon nanotube (MWCNTs) was evaluated. The NiHCF)/MWCNT electrode film was fabricated using the liquid-liquid interface method, and it was used as a precursor for the electrochemical synthesis of nickel oxy-hydroxy (Ni(OH)₂/NiOOH/MWCNT). The interaction between nickel oxy-hydroxy and the MWCNTs provided a film that is stable over the electrode surface, with high surface area and excellent conductivity. The nanocomposite presented an excellent electrocatalytic activity for the oxidation of glucose in an alkaline medium. The sensitivity of the sensor was found to be 0.0561 μA μmol L^-1, and a linear range from 0.1 to 150 μmol L^-1 was obtained, with a good limit of detection (0.030 μmol L^-1). The electrode exhibits a fast response (150 injections h^-1) and a sensitive catalytic performance, which may be due to the high conductivity of MWCNT and the increased active surface area of the electrode. Additionally, a minimal difference in the slopes for ascending (0.0561 µA µmol L^-1) and descending (0.0531 µA µmol L^-1) was observed. Moreover, the sensor was applied to the detection of glucose in artificial plasma blood samples, achieving values of 89 to 98% of recovery.

A versatile 3D printed multi-electrode cell for determination of three COVID-19 biomarkers

3D-printing has shown an outstanding performance for the production of versatile electrochemical devices. However, there is a lack of studies in the field of 3D-printed miniaturized settings for multiplex biosensing. In this work, we propose a fully 3D-printed micro-volume cell containing six working electrodes (WEs) that operates with 250 μL of sample. A polylactic acid/carbon black conductive filament (PLA/CB) was used to print the WEs and subsequently modified with graphene oxide (GO), to support protein binding. Cyclic voltammetry was employed to investigate the electrochemical behaviour of the novel multi-electrode cell. In the presence of K₃[Fe(CN)₆], PLA/CB/GO showed adequate peak resolution for subsequent label-free immunosensing. The innovative 3D-printed cell was applied for multiplex voltammetric detection of three COVID-19 biomarkers as a proof-of-concept. The multiple sensors showed a wide linear range with detection limits of 5, 1 and 1 pg mL^-1 for N-protein, S_RBD-protein, and anti-S_RBD, respectively. The sensor performance enabled the selective sequential detection of N protein, S_RBD protein, and anti-S_RBD at biological levels in saliva and serum. In summary, the miniaturized six-electrode cell presents an alternative for the low-cost and fast production of customizable devices for multi-target sensing with promising application in the development of point-of-care sensors.

Adjusting the Connection Length of Additively Manufactured Electrodes Changes the Electrochemical and Electroanalytical Performance

Changing the connection length of an additively manufactured electrode (AME) has a significant impact on the electrochemical and electroanalytical response of the system. In the literature, many electrochemical platforms have been produced using additive manufacturing with great variations in how the AME itself is described. It is seen that when measuring the near-ideal outer-sphere redox probe hexaamineruthenium (III) chloride (RuHex), decreasing the AME connection length enhances the heterogeneous electrochemical transfer (HET) rate constant (k0) for the system. At slow scan rates, there is a clear change in the peak-to-peak separation (ΔEp) observed in the RuHex voltammograms, with the ΔEp shifting from 118 ± 5 mV to 291 ± 27 mV for the 10 and 100 mm electrodes, respectively. For the electroanalytical determination of dopamine, no significant difference is noticed at low concentrations between 10- and 100-mm connection length AMEs. However, at concentrations of 1 mM dopamine, the peak oxidation is shifted to significantly higher potentials as the AME connection length is increased, with a shift of 150 mV measured. It is recommended that in future work, all AME dimensions, not just the working electrode head size, is reported along with the resistance measured through electrochemical impedance spectroscopy to allow for appropriate comparisons with other reports in the literature. To produce the best additively manufactured electrochemical systems in the future, researchers should endeavor to use the shortest AME connection lengths that are viable for their designs.

Additively manufactured electrodes for the electrochemical detection of hydroxychloroquine

Although studies have demonstrated the inactivity of hydroxychloroquine (HCQ) towards SARS-CoV-2, this compound was one of the most prescribed by medical organizations for the treatment of hospitalized patients during the coronavirus pandemic. As a result of it, HCQ has been considered as a potential emerging contaminant in aquatic environments. In this context, we propose a complete electrochemical device comprising cell and working electrode fabricated by the additive manufacture (3D-printing) technology for HCQ monitoring. For this, a 3D-printed working electrode made of a conductive PLA containing carbon black assembled in a 3D-printed cell was associated with square wave voltammetry (SWV) for the fast and sensitive determination of HCQ. After a simple surface activation procedure, the proposed 3D-printed sensor showed a linear response towards HCQ detection (0.4-7.5 μmol L^-1) with a limit of detection of 0.04 μmol L^-1 and precision of 2.4% (n = 10). The applicability of this device was shown to the analysis of pharmaceutical and water samples. Recovery values between 99 and 112% were achieved for tap water samples and, in addition, the obtained concentration values for pharmaceutical tablets agreed with the values obtained by spectrophotometry (UV region) at a 95% confidence level. The proposed device combined with portable instrumentation is promising for on-site HCQ detection.