RESUMO

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.

Assuntos

RESUMO

A new electrochemical device fabricated by the combination of 3D printing manufacturing and laser-generated graphene sensors is presented. Cell and electrodes were 3D printed by the fused deposition modeling (FDM) technique employing acrylonitrile butadiene styrene filament (insulating material that composes the cell) and conductive filament (lab-made filament based on graphite dispersed into polylactic acid matrix) to obtain reference and auxiliary electrodes. Infrared-laser engraved graphene, also reported as laser-induced graphene (LIG), was produced by laser conversion of a polyimide substrate, which was assembled in the 3D-printed electrochemical cell that enables the analysis of low volumes (50-2000 µL). XPS analysis revealed the formation of nitrogen-doped graphene multilayers that resulted in excellent electrochemical sensing properties toward the detection of atropine (ATR), a substance that was found in beverages to facilitate sexual assault and other criminal acts. Linear range between 5 and 35 µmol L-1, detection limit of 1 µmol L-1, and adequate precision (RSD = 4.7%, n = 10) were achieved using differential-pulse voltammetry. The method was successfully applied to beverage samples with recovery values ranging from 80 to 105%. Interference studies in the presence of species commonly found in beverages confirmed satisfactory selectivity for ATR sensing. The devices proposed are useful portable analytical tools for on-site applications in the forensic scenario.

RESUMO

A novel conductive filament based on graphite (Gr) dispersed in polylactic acid polymer matrix (PLA) is described to produce 3D-electrochemical devices (Gr/PLA). This conductive filament was used to additively manufacture electrochemical sensors using the 3D pen. Thermogravimetric analysis confirmed that Gr was successfully incorporated into PLA, achieving a composite material (40:60% w/w, Gr and PLA, respectively), while Raman and scanning electron microscopy revealed the presence of defects and a high porosity on the electrode surface, which contributes to improved electrochemical performance. The 3D-printed Gr/PLA electrode provided a more favorable charge transfer (335 Ω) than the conventional glassy carbon (1277 Ω) and 3D-printed Proto-pasta® (3750 Ω) electrodes. As a proof of concept, the ciprofloxacin antibiotic, a species of multiple interest, was selected as a model molecule. Thus, a square wave voltammetry (SWV) method was proposed in the potential range + 0.9 to + 1.3 V (vs Ag|AgCl|KCl(sat)), which provided a wide linear working range (2 to 32 µmol L-1), 1.79 µmol L-1 limit of detection (LOD), suitable precision (RSD < 7.9%), and recovery values from 94 to 109% when applied to pharmaceutical and milk samples. Additionally, the sensor is free from the interference of other antibiotics routinely employed in veterinary practices. This device is disposable, cost-effective, feasibly produced in financially limited laboratories, and consequently promising for evaluation of other antibiotic species in routine applications.

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RESUMO

Antibiotics such as tetracycline (TC) are widely prescribed to treat humans or dairy animals. Therefore, it is important to establish affordable devices in laboratories with minimal infrastructure. 3D printing has proven to be a powerful and cost-effective tool that revolutionizes many applications in electrochemical sensing. In this work, we employ a conductive filament based on graphite (Gr) and polylactic acid (PLA) (40:60; w/w; synthesized in our lab) to manufacture 3D-printed electrodes. This electrode was used "as printed" and coupled to batch injection analysis with amperometric detection (BIA-AD) for TC sensing. Preliminary studies by cyclic voltammetry and differential pulse voltammetry revealed a mass transport governed by adsorption of the species and consequent fouling of the redox products on the 3D printed surface. Thus, a simple strategy (solution stirring and application of successive potentials, +0.95 V followed by +1.2 V) was associated with the BIA-AD system to solve this effect. The proposed electrode showed analytical performance comparable to costly conventional electrodes with linear response ranging from 0.5 to 50 µmol L-1 and a detection limit of 0.19 µmol L-1. Additionally, the developed method was applied to pharmaceutical, tap water, and milk samples, which required minimal sample preparation (simple dilution). Recovery values of 92-117% were obtained for tap water and milk samples, while the content found of TC in the capsule was close to the value reported by the manufacturer. These results indicate the feasibility of the method for routine analysis involving environmental, pharmaceutical, and food samples.

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RESUMO

The combination of CO2 laser ablation and electrochemical surface treatments is demonstrated to improve the electrochemical performance of carbon black/polylactic acid (CB/PLA) 3D-printed electrodes through the growth of flower-like Na2O nanostructures on their surface. Scanning electron microscopy images revealed that the combination of treatments ablated the electrode's polymeric layer, exposing a porous surface where Na2O flower-like nanostructures were formed. The electrochemical performance of the fabricated electrodes was measured by the reversibility of the ferri/ferrocyanide redox couple presenting a significantly improved performance compared with electrodes treated by only one of the steps. Electrodes treated by the combined method also showed a better electrochemical response for tyrosine oxidation. These electrodes were used as a non-enzymatic tyrosine sensor for quantification in human urine samples. Two fortified urine samples were analyzed, and the recovery values were 106 and 109%. The LOD and LOQ for tyrosine determination were 0.25 and 0.83 µmol L-1, respectively, demonstrating that the proposed devices are suitable sensors for analyses of biological samples, even at low analyte concentrations.

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RESUMO

Sulfanilamide (SFL) is used to prevent infections in honeybees. However, many regulatory agencies prohibit or establish maximum levels of SFL residues in honey samples. Hence, we developed a low-cost and portable electrochemical method for SFL detection using a disposable device produced through 3D printing technology. In the proposed approach, the working electrode was printed using a conductive filament based on carbon black and polylactic acid and it was associated with square wave voltammetry (SWV). Under optimized SWV parameters, linear concentration ranges (1-10 µmol L-1 and 12.5-35.0 µmol L-1), a detection limit of 0.26 µmol L-1 (0.05 mg L-1), and suitable RSD values (2.4% for inter-electrode; n = 3) were achieved. The developed method was selective in relation to other antibiotics applied in honey samples, requiring only dilution in the electrolyte. The recovery values (85-120%) obtained by SWV were statistically similar (95% confidence level) to those obtained by HPLC, attesting to the accuracy of the analysis and the absence of matrix interference.

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RESUMO

Pesticides are heavily employed compounds protecting crops, however, these compounds can be extremely harmful to human health. Once the monitoring of pesticides in foods is of great importance, in this work we propose a ready-to-use electrochemical sensor made with 3D printing technology, capable of detecting paraquat and carbendazim in sequential analysis. The proposed electrodes are lab-made and of easy obtention, composed of graphite on a polylactic acid matrix, and provided great results for the analysis of paraquat and carbendazim in honey, milk, juice, and water samples. The sequential analysis of paraquat and carbendazim was proposed, providing optimal analysis of both compounds individually when both are present in a mixture. Limits of detection of 0.01 and 0.03 µmol/L for paraquat and carbendazim, respectively. Recovery tests attested to the suitability of the method, ranging from 94.5 to 113.7 %, and the suitability of 3D printing for environmental and food samples analysis.

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RESUMO

Simple, low-cost, and sensitive new platforms for electrochemical immunosensors for virus detection have been attracted attention due to the recent pandemic caused by a new type of coronavirus (SARS-CoV-2). In the present work, we report for the first time the construction of an immunosensor using a commercial 3D conductive filament of carbon black and polylactic acid (PLA) to detect Hantavirus Araucaria nucleoprotein (Np) as a proof-of-concept. The recognition biomolecule was anchored directly at the filament surface by using N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and N-Hydroxysuccinimide (EDC/NHS). Conductive and non-conductive composites of PLA were characterized using thermal gravimetric analysis (TGA), revealing around 30% w/w of carbon in the filament. Morphological features of composites were obtained from SEM and TEM measurements. FTIR measurement revealed that crosslinking agents were covalently bonded at the filament surface. Electrochemical techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used for the evaluation of each step involved in the construction of the proposed immunosensor. The results showed the potentiality of the device for the quantitative detection of Hantavirus Araucaria nucleoprotein (Np) from 30 µg mL-1 to 240 µg mL-1 with a limit of detection of 22 µg mL-1. Also, the proposed immunosensor was applied with success for virus detection in 100x diluted human serum samples. Therefore, the PLA conductive filament with carbon black is a simple and excellent platform for immunosensing, which offers naturally carboxylic groups able to anchor covalently biomolecules.

Assuntos