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Additive manufacturing (3D printing), particularly fused deposition modeling (FDM), has rapidly advanced, offering customized designs, reduced waste, lower costs, and fast prototyping for electroanalytical applications. Herein, the electrochemical secnidazole (SCZ) behavior was studied using additive manufactured electrodes (AMEs) based on commercial carbon black and polylactic acid (PLA) conductive filament. Before use, AMEs were submitted to electrochemical/chemical activation (+1.4 V and -1.0 V, both for 200 s) in basic medium (0.5 mol L -1 NaOH). Under optimized square wave voltammetry (SWV) conditions and using 0.12 mol L -1 Britton Robinson buffer (pH = 2.0) as supporting electrolyte, SCZ exhibited excellent linearity within the concentration range of 2.5 to 250.0 μmol L -1 ( R 2 = 0.998). The proposed method was successfully applied to detect and quantify SCZ in pharmaceutical and seized samples. The obtained results were statistically similar (95% confidence level) to the values obtained by HPLC. These findings demonstrate that the 3D-printed electrodes developed in this study provide a cost-effective, facile, and highly sensitive platform for on-site SCZ analysis, presenting significant potential for future forensic applications.

Background: Paracetamol or acetaminophen (APAP), or acetaminophen, is a widely used medication for pain relief and fever reduction due to its analgesic and antipyretic properties. However, excessive APAP consumption can lead to severe hepatotoxicity and nephrotoxicity, posing overdose risks. Consequently, the development of analytical methods for an accurate and rapid detection of APAP in biological matrices is of great interest in the health-related fields. Electrochemical methods have emerged as efficient, cost-effective, and sensitive tools for APAP detection in biological samples. In the light of the reported insights, this review examines critically diverse electrochemical methods for PAR detection in different biological matrices, including serum, urine, oral fluid, and sweat., Results: The claimed benefits of chemically-modified electrodes towards the selective determination of paracetamol in such complex sample matrices are discussed. On the other hand, the possible use of unmodified carbon-based electrodes combined with flow methods is highlighted as an alternative that can find relevance in the analysis of biological fluids suspected of PAR overdose occurring in the forensic scenario. Furthermore, the details regarding the distinct techniques and working electrodes for APAP determination are presented, compared and discussed in separate sections for each biological sample (serum, urine, and oral fluid). Another aspect herein debated is the selective determination of APAP in the presence of electroactive drugs naturally found in biological samples, as uric acid, and ascorbic acid, are evaluated. In addition, we have discussed and emphasized the significance of matrix selection to ensure precise results, especially in potential overdose scenarios., Significance: This review article provides a critical discussion on the development of electroanalytical methods for biological fluids, with relevance to the fields of clinical analysis and forensics., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

In response to the growing need for sustainable analytical methods, this study explores the repurposing of screen-printed electrodes (SPEs) that would otherwise be discarded. This involves recoating the working electrode surface with a graphite (Gr) and chitosan (CTS) dispersion, creating a reusable SPE (SPE-Gr/CTS). Demonstrating its utility, SPE-Gr/CTS was employed for the detection of 4-bromo-2,5-dimethoxyphenethylamine (2C-B), a phenylethylamine commonly used for recreational proposes. Identifying 2C-B in fluid oral and seized samples is of great interest for forensic and toxicological applications. The 2C-B detection using SPE-Gr/CTS was optimized in Britton-Robinson buffer solution (0.1 mol L -1 ) at pH 2.0, employing square-wave adsorptive stripping voltammetry. The electrochemical behavior of 2C-B on SPE-Gr/CTS exhibited one irreversible oxidation and a reversible redox process. The proposed method presented a dynamic linear range for 2C-B determination (0.05 to 7.5 μmol L -1 ) with a low LOD (0.015 μmol L -1 ). Moreover, the stability of 2C-B electrochemical responses on SPE-Gr/CTS was confirmed using the same or different electrodes ( N = 3), with a relative standard deviation of less than 5.0%. Interference studies with seventeen other illicit drugs and adulterants demonstrated that the proposed method is selective for 2C-B detection even in the presence of these substances. Real seized and oral fluid samples containing 2C-B were analyzed using this method, and the results were confirmed by LC-MS. The proposed device demonstrates to be an environmentally friendly and selective sensor for 2C-B detection in forensic analysis, offering a rapid and straightforward screening method for seized and biological samples. In addition, a portable and sensitive determination of 2C-B in forensic samples is presented with minimal sample consumption (50 μL).

The use of synthetic cathinones (SCs) has increased in recent years, posing significant public health problems due to their adverse effects and potential for fatal poisonings. The structural diversity and rapid emergence of new SC analogues create challenges for law enforcement and drug screening techniques. This work presents for the first time the electrochemical detection of SCs using differential pulse voltammetry (DPV) on a boron-doped diamond electrode (BDDE). We analyzed 15 SCs, including well-known compounds such as mephedrone, methylone, and ephylone, revealing distinct electrochemical profiles with two characteristic reduction peaks (R 1 and R 2 ). The method was optimized in Britton-Robinson buffer (0.1 mol L -1 , pH 8.0) and demonstrated a high selectivity and sensitivity. Multivariate statistical methods, including principal component analysis and hierarchical cluster analysis, classified SCs into six distinct groups. The DPV optimization and analytical parameter determination, including the limit of detection (LOD), were performed for the least electroactive SC, 4'-methyl-α-pyrrolidinohexanophenone, yielding an LOD of 3.8 μmol L -1 , suitable for screening street samples. Interference studies with common illicit drugs and adulterants confirmed the selectivity of the DPV-BDDE method. Preliminary identification of SCs in 46 real seized samples was successfully performed using this method with results validated by liquid chromatography-mass spectrometry (LC-MS). The method also identified three SCs not included in the original set: bupropion, benzylone, and dipentylone. The DPV-BDDE method offers a rapid, robust, and portable approach for the selective screening of SCs in forensic applications, demonstrating significant advantages over traditional colorimetric tests.

The advent of new psychoactive substances (NPS) has caused enormous difficulty for legal control since they are rapidly commercialized, and their chemical structures are routinely altered. In this aspect, derivatives phenethylamines, such as 25E-NBOH, have received great attention in the forensic scenario. Hence, we propose portable and cost-effective (U$ 5.00) 3D-printed devices for the electrochemical screening of 25E-NBOH for the first time. The cell and all electrodes were printed using acrylonitrile butadiene styrene filament (insulating material) and conductive filament (graphite embedded in a polylactic acid matrix), respectively, both by the fused deposition modeling (FDM) 3D printing technique. The electrochemical apparatus enables micro-volume analysis (50-2000 μL), especially important for low sample volumes. A mechanistic route for the electrochemical oxidation of 25E-NBOH is proposed based on cyclic voltammetric data, which showed two oxidation processes around +0.75 V and +1.00 V and a redox pair between +0.2 and -0.2 V (vs. graphite ink pseudo-reference). A fast and sensitive square-wave voltammetry method was developed, which exhibited a linear working range from 0.85 to 5.1 μmoL -1 , detection limit of 0.2 μmol L -1 , and good intra-electrode precision (n = 10, RSD <5.3 %). Inter-electrode measurements (n = 3, RSD <9.8 %) also attested that the electrode production process is reproducible. Interference tests in the presence of other drugs frequently found in blotting paper indicated high selectivity of the electrochemical method for screening of 25E-NBOH. Screening analysis of blotting paper confirmed the presence of 25E-NBOH in the seized samples. Moreover, a recovery percentage close to 100 % was found for a spiked saliva sample, suggesting the method's usefulness for quantitative purposes aimed at information on recent drug use., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Fused deposition modeling (FDM) 3D printing is a promising additive manufacturing technique to produce low-cost disposable electrochemical devices. However, the print of devices like well-known screen-printed electrodes (all electrodes on the same device) is difficult using the available technology (few materials available for production of working electrodes). In this paper we present a procedure to produce disposable and robust electrochemical devices by FDM 3D printing that allows reproducible analysis of small volumes (50-2000 μL). The device consists of just two printed parts that allow easy coupling of different conductive materials for using as disposable or non-disposable working electrodes with reproducible geometric area. Printed counter and pseudo-reference electrodes can also be easily fitted into the microcell. Moreover, conventional counter (platinum wire) and mini reference electrodes can also be used. As a proof of concept, paracetamol, cocaine and uric acid were used as model analytes using different materials as working electrodes. Linear calibration curves (r > 0.99) with similar slopes (0.29 ± 0.01 μA μmol L -1 ; RSD = 3.4%) were obtained by square wave voltammetry (SWV) using a complete printed system and different volumes of standard solutions of paracetamol (50, 100, and 200 μL). For uric acid, a linear range of 10-125 μmol L -1 (r > 0.99), was obtained using differential pulse voltammetry as the electrochemical technique and a disposable laser-induced graphene base as the working electrode. With the coupling of boron-doped diamond working electrode, screening tests were successfully performed in seized cocaine samples with selective detection of cocaine in the presence of its most common adulterants. The production cost per unit of a complete electrochemical system is around US 5.00. In large-scale production, only the working electrode needs to be replaced while the microcell and counter/pseudo reference electrodes do not need to be discarded., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Red mud (RM) is composed of a waste alkaline solution (pH = 13.3) obtained from the production of alumina. It contains high concentrations of hematite (Fe 2 O 3 ), goethite (FeOOH), gibbsite [Al(OH) 3 ], a boehmite (AlOOH), anatase (Tetragonal-TiO 2 ), rutile (Ditetragonal dipyramidal-TiO 2 ), hydrogarnets [Ca 3 Al 2 (SiO 4 ) 3-x (OH) 4x ], quartz (SiO 2 ), and perovskite (CaTiO 3 ). It was shown to be an excellent catalytic mixture for biodiesel production. To demonstrate the value of RM, an environmentally friendly process of transesterification in aqueous medium using waste cooking oil (WCO), MeOH, and waste alkaline solution (WAS) obtained from aluminum production was proposed. Triglycerides of WCO reacted with MeOH at 60 °C to yield mixtures of fatty acid methyl esters (FAMEs) in the presence of 0.019% ( w / w ) WAS/WCO using the WAS (0.204 mol L -1 , predetermined by potentiometric titration) from aluminum production by the Bayer process. The use of the new catalyst (WAS) resulted in a high yield of the products (greater than 99% yield).

Mephedrone (MEP) is an illicit stimulant drug that belongs to the synthetic cathinone (SC) class, which has been widely used for recreational purposes and reported in forensic analysis. The preliminary identification of MEP and other SCs in seized samples is of great interest for forensic investigation and a fast and simple screening test for these drugs would be useful for on-site and in-house analyses. In this study, we present the electrochemical detection of MEP in forensic samples using, for the first time, independent redox processes of SCs on a graphene screen-printed electrode (SPE-GP). The proposed method for MEP detection on the SPE-GP was optimized in Britton-Robinson buffer solution (0.1 mol L -1 ) at pH 10.0 with adsorptive stripping differential pulse voltammetry (AdSDPV). The use of the SPE-GP with AdSDPV provides a wide linear range for MEP determination (2.6 to 112 μmol L -1 ) with a low limit of detection (LOD) (0.3 μmol L -1 ). The real surface area available for adsorption on the SPE-GP was estimated to be between 3.80 and 5.70 cm 2 , which provided high sensitivity for the proposed method. Furthermore, good stability of MEP electrochemical responses on the SPE-GP was obtained using the same or different electrodes ( N = 3), with relative standard deviation (RSD) < 5.0% for both redox processes. Interference studies for a common adulterant (caffeine) and twelve other illicit drugs (phenethylamines, amphetamines, and other SCs) were performed with a highly selective response for MEP detection. Therefore, the SPE-GP with AdSDPV is demonstrated to be a selective and sensitive screening method to detect MEP and other SCs in forensic analysis, providing a fast and simple preliminary identification of these drugs in seized samples.

SiO 2 -SO 3 H, with a surface area of 115 m 2 /g and pore volume of 0.38 cm 3 g -1 , and 1.32 mmol H + /g was used as a 20% w / w catalyst for the preparation of methyl salicylate (wintergreen oil or MS) from acetylsalicylic acid (ASA). A 94% conversion was achieved in a microwave reactor over 40 min at 120 °C in MeOH. The resulting crude product was purified by flash chromatography. The catalyst could be reused three times.

1-(3-chlorophenyl) piperazine (mCPP) is a synthetic drug with hallucinogenic effects that has often been found in seized samples. In this context, easy to use point-of-care tests can be of great value in preliminary forensic analysis. Herein, we proposed a simple, fast, and portable electrochemical method for the detection of mCPP in seized samples. The method is based on the use of disposable screen-printed carbon electrodes (SPCE) and rapid screening procedures by square-wave voltammetry using minimal sample sizes (100 μL). mCPP showed an irreversible electrochemical oxidation process at +0.65 V on SPCE (vs Ag) using 0.04 mol L -1 Britton Robinson (BR) buffer solution (pH 7) as the supporting electrolyte. The proposed method exhibited a linear correlation (r = 0.998) between peak current and mCPP concentration in the range of 1-30 μmol L -1 (LOD = 0.1 μmol L -1 ). Interference studies were performed for adulterants and other classes of drugs of abuse, which can also be found in seized samples containing mCPP, such as caffeine, amphetamine, methamphetamine, 1-benzylpiperazine, 3,4-methylenedioxymethamphetamine, methylone, mephedrone, ethylone and 3, 4-methylenedioxypyrovalerone. The developed method presents great potential as a rapid and simple screening tool to detect mCPP in forensic samples., (Copyright © 2021 Elsevier B.V. All rights reserved.)

3,4-methylenedioxypyrovalerone (MDPV) is a harmful and controlled synthetic cathinone used as a psychostimulant drug and as sport-enhancing substance. A sensor was developed for the direct analysis of MDPV by transducing its oxidation signal by means of an electropolymerized molecularly imprinted polymer (e-MIP) built in-situ on the screen-printed carbon electrode's (SPCE) surface previously covered with multi-walled carbon nanotubes (MWCNTs) and silver nanoparticles (AgNPs). Benzene-1,2-diamine was used as the functional monomer while the analyte was used as the template monomer. Each step of the sensor's development was studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in a solution containing ferricyanide, however no redox probe was required for the actual MDPV measurements. The interaction between the poly( o -phenylenediamine) imprinted polymer and MDPV was studied by density-functional theory (DFT) methods. The SPCE-MWCNT-AgNP-MIP sensor responded adequately to the variation of MDPV concentration. It was shown that AgNPs enhanced the electrochemical signal by around a 3-fold factor. Making use of square-wave voltammetry (SWV) the developed sensor provided a limit of detection (LOD) of 1.8 μmol L -1 . The analytical performance of the proposed sensor paves the way to the development of a portable device for MDPV on-site sensing to be applied in forensic and doping analysis.

SiO 2 -SO 3 H, with a surface area of 115 m 2 /g, pore volumes of 0.38 cm 3 g -1 and 1.32 mmol H + /g, was used as a 10% w/w catalyst for the preparation of 5-hydroxymethyl-2-furfural (HMF) from fructose. A conversion of 100% was achieved in a microwave reactor during 10 min at 150 °C in DMSO, with 100% selectivity for HMF, at a molar ratio of fructose: DMSO equal to 1:56. The catalyst could be re-used three times.

Due to the its physical-chemical properties, alumina nanoparticles have potential applications in several areas, such as nanobiomaterials for medicinal or orthodontic implants, although the introduction of these devices poses a serious risk of microbial infection. One convenient strategy to circumvent this problem is to associate the nanomaterials to antimicrobial peptides with broad-spectrum of activities. In this study we present two novel synthesis approaches to obtain fibrous type alumina nanoparticles covalently bound to antimicrobial peptides. In the first strategy, thiol functionalized alumina nanoparticles were linked via disulfide bond formation to a cysteine residue of an analog of the peptide BP100 containing a four amino acid spacer (Cys-Ala-Ala-Ala). In the second strategy, alumina nanoparticles were functionalized with azide groups and then bound to alkyne-decorated analogs of the peptides BP100 and DD K through a triazole linkage obtained via a copper(I)-catalyzed cycloaddition reaction. The complete physical-chemical characterization of the intermediates and final materials is presented along with in vitro biological assays and membrane interaction studies, which confirmed the activity of the obtained nanobiostructures against both bacteria and fungi. To our knowledge, this is the first report of aluminum nanoparticles covalently bound to triazole-peptides and to a disulfide bound antimicrobial peptide with high potential for biotechnological applications., (Copyright © 2019. Published by Elsevier B.V.)

The functionalization of alumina nanoparticles of specific morphology with antimicrobial peptides (AMP) can be a promising strategy for modeling medical devices and packaging materials for cosmetics, medicines or food, since the contamination by pathogens could be reduced. In this paper, we show the synthesis of a fibrous-like alumina nanobiostructure, as well as its functionalization with the peptide EAAA-BP100, an analog of the antimicrobial peptide BP100. The antibacterial activity of the obtained material against some bacterial strains is also investigated. The covalent binding of the peptide to the nanoparticles was promoted by a reaction between the carboxyl group of the glutamate side chain (E1) of the peptide and the amino groups of the alumina nanoparticles, previously modified by reaction with 3-aminopropyltrietoxysilane (APTES). The functionalized nanoparticles were characterized by zeta potential measurements, Fourier transform infrared spectroscopy, and other physicochemical techniques. Although the obtained alumina nanobiostructure shows a relatively low degree of substitution with EAAA-BP100, antibacterial activities against Escherichia coli and Salmonella typhimurium strains are appreciably higher than the activities of the free peptide. The obtained results can affect the design of new hybrid nanobiomaterials based on nanoparticles functionalized with AMP., (Copyright © 2018. Published by Elsevier B.V.)