Forensic Analysis of Synthetic Cathinones on Nanomaterials-Based Platforms: Chemometric-Assisted Voltametric and UPLC-MS/MS Investigation.

Synthetic cathinones (SCs) are a group of new psychoactive substances often referred to as "legal highs" or "bath salts", being characterized by a dynamic change, new compounds continuously emerging on the market. This creates a lack of fast screening tests, making SCs a constant concern for law enforcement agencies. Herein, we present a fast and simple method for the detection of four SCs (alpha-pyrrolidinovalerophenone, N-ethylhexedrone, 4-chloroethcathinone, and 3-chloromethcathinone) based on their electrochemical profiles in a decentralized manner. In this regard, the voltametric characterization of the SCs was performed by cyclic and square wave voltammetry. The elucidation of the SCs redox pathways was successfully achieved using liquid chromatography coupled to (tandem) mass spectrometry. For the rational identification of the ideal experimental conditions, chemometric data processing was employed, considering two critical qualitative and quantitative variables: the type of the electrochemical platform and the pH of the electrolyte. The analytical figures of merit were determined on standard working solutions using the optimized method, which exhibited wide linear ranges and LODs suitable for confiscated sample screening. Finally, the performance of the method was evaluated on real confiscated samples, the resulting validation parameters being similar to those obtained with another portable device (i.e., Raman spectrometer).

Highly Sensitive Detection of PQS Quorum Sensing in Pseudomonas Aeruginosa Using Screen-Printed Electrodes Modified with Nanomaterials.

The rapid diagnosis of Pseudomonas aeruginosa infection is very important because this bacterium is one of the main sources of healthcare-associated infections. Pseudomonas quinolone signal (PQS) is a specific molecule for quorum sensing (QS) in P. aeruginosa, a form of cell-to-cell bacterial communication and its levels can allow the determination of the bacterial population. In this study, the development of the first electrochemical detection of PQS using screen-printed electrodes modified with carbon nanotubes (CNT-SPE) is reported. The electrochemical fingerprint of PQS was determined using different electrode materials and screen-printed electrodes modified with different nanomaterials. The optimization of the method in terms of electrolyte, pH, and electrochemical technique was achieved. The quantification of PQS was performed using one of the anodic peaks in the electrochemical fingerprint of the PQS on the CNT-SPE. The sensor exhibited a linear range from 0.1 to 15 µM, with a limit of detection of 50 nM. The sensor allowed the selective detection of PQS, with low interference from other QS molecules. The sensor was successfully applied to analysis of real samples (spiked urine and human serum samples, spiked microbiological growth media, and microbiological cultures).

Label-Free Electrochemical Aptasensor for the Detection of the 3-O-C12-HSL Quorum-Sensing Molecule in Pseudomonas aeruginosa.

Pseudomonas aeruginosa, an opportunistic Gram-negative bacterium, is one of the main sources of infections in healthcare environments, making its detection very important. N-3-oxo-dodecanoyl L-homoserine lactone (3-O-C12-HSL) is a characteristic molecule of quorum sensing-a form of cell-to-cell communication between bacteria-in P. aeruginosa. Its detection can allow the determination of the bacterial population. In this study, the development of the first electrochemical aptasensor for the detection of 3-O-C12-HSL is reported. A carbon-based screen-printed electrode modified with gold nanoparticles proved to be the best platform for the aptasensor. Each step in the fabrication of the aptasensor (i.e., gold nanoparticles' deposition, aptamer immobilization, incubation with the analyte) was optimized and characterized using cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. Different redox probes in solution were evaluated, the best results being obtained in the presence of [Fe(CN)6]4-/[Fe(CN)6]3-. The binding affinity of 106.7 nM for the immobilized thiol-terminated aptamer was determined using surface plasmon resonance. The quantification of 3-O-C12-HSL was performed by using the electrochemical signal of the redox probe before and after incubation with the analyte. The aptasensor exhibited a logarithmic range from 0.5 to 30 µM, with a limit of detection of 145 ng mL-1 (0.5 µM). The aptasensor was successfully applied for the analysis of real samples (e.g., spiked urine samples, spiked microbiological growth media, and microbiological cultures).

An Overview of Healthcare Associated Infections and Their Detection Methods Caused by Pathogen Bacteria in Romania and Europe.

Healthcare-associated infections can occur in different care units and can affect both patients and healthcare professionals. Bacteria represent the most common cause of nosocomial infections and, due to the excessive and irrational use of antibiotics, resistant organisms have appeared. The most important healthcare-associated infections are central line-associated bloodstream infections, catheter-associated urinary tract infections, surgical site, soft tissue infections, ventilator-associated pneumonia, hospital acquired pneumonia, and Clostridioides difficile colitis. In Europe, some hospitalized patients develop nosocomial infections that lead to increased costs and prolonged hospitalizations. Healthcare-associated infection prevalence in developed countries is lower than in low-income and middle-income countries such as Romania, an Eastern European country, where several factors contribute to the occurrence of many nosocomial infections, but official data show a low reporting rate. For the rapid identification of bacteria that can cause these infections, fast, sensitive, and specific methods are needed, and they should be cost-effective. Therefore, this review focuses on the current situation regarding healthcare-associated infections in Europe and Romania, with discussions regarding the causes and possible solutions. As a possible weapon in the fight against the healthcare-associated infections, the diagnosis methods and tests used to determine the bacteria involved in healthcare-associated infections are evaluated.

Analytical methods for the characterization and diagnosis of infection with Pseudomonas aeruginosa: A critical review.

The recent increase in outbreaks of pathogenic bacteria and antimicrobial resistance represent major public health problems. Being the leading cause of death in humans, the bacterial infections need to be accurately and quickly diagnosed. Hence, the development of fast, cost-effective, sensitive and specific strategies for the detection of the targeted bacterium is of utmost importance. This review presents a systematic, critical evaluation of the recent analytical methods for the characterization and diagnosis of infections caused by Pseudomonas aeruginosa. The clinical manifestations, incidence and treatment of the P. aeruginosa infection and the associated quorum sensing, biofilm formation and virulence factors are also discussed. An overview of a variety of analytical methods for the detection of P. aeruginosa is provided, including whole-cell detection (microbiological methods, biosensors), antigens, DNA, and relevant markers (quorum sensing molecules, virulence factors) detection. The latest trends in analytical methods, especially sensors, are the orientation towards portability and on-site detection. The efforts made so far to achieve these goals in the detection of P. aeruginosa and its markers are also presented and discussed in this review. The strengths and weaknesses of the current detection methods are evaluated, while exploring potential routes for further development.

Gold-based nanostructured platforms for oxytetracycline detection from milk by a "signal-on" aptasensing approach.

Several gold platforms of different morphologies were investigated in the elaboration of a new aptasensor for oxytetracycline. Au-nanostructures were electrochemically synthesized from solutions of different concentrations of HAuCl4 in different media by chronoamperometry, multipulse amperometry, and chronopotentiometry, respectively at carbon-based screen-printed electrodes (C-SPE). The nano-/micro-scale morphologies of the patterned surfaces and elemental composition were examined by scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy, respectively. The electrochemical properties of the obtained gold nanostructured platforms (AuNSs|C-SPE) were investigated to achieve optimal aptamer coverage. The results showed that the aptasensor developed using the platform with thistle-like AuNSs exhibited the highest conductivity in terms of ferrocene signal and the largest effective area. Under optimal conditions, a linear range from 5.0 × 10-8 M to 1.2 × 10-6 M, with a limit of detection (LOD) of 8.7 × 10-9 M OXT were obtained, which is about 20 times lower than the EU regulations for OXT residues in milk. The electrochemical aptasensor was able to discriminate other antibacterial agents, such as amoxicillin, ampicillin, gentamicin, tetracycline, and vancomycin and was successfully applied in milk samples. This "signal-on" aptasensing approach provides a simple and cost-effective disposable sensor that could be easily applied for the on-site determination of antibiotics.

Electrochemical Peptide-Based Sensors for Foodborne Pathogens Detection.

Food safety and quality control pose serious issues to food industry and public health domains, in general, with direct effects on consumers. Any physical, chemical, or biological unexpected or unidentified food constituent may exhibit harmful effects on people and animals from mild to severe reactions. According to the World Health Organization (WHO), unsafe foodstuffs are especially dangerous for infants, young children, elderly, and chronic patients. It is imperative to continuously develop new technologies to detect foodborne pathogens and contaminants in order to aid the strengthening of healthcare and economic systems. In recent years, peptide-based sensors gained much attention in the field of food research as an alternative to immuno-, apta-, or DNA-based sensors. This review presents an overview of the electrochemical biosensors using peptides as molecular bio-recognition elements published mainly in the last decade, highlighting their possible application for rapid, non-destructive, and in situ analysis of food samples. Comparison with peptide-based optical and piezoelectrical sensors in terms of analytical performance is presented. Methods of foodstuffs pretreatment are also discussed.

Electrochemical Fingerprints of Illicit Drugs on Graphene and Multi-Walled Carbon Nanotubes.

Illicit drugs use and abuse remains an increasing challenge for worldwide authorities and, therefore, it is important to have accurate methods to detect them in seized samples, biological fluids and wastewaters. They are recently classified as the latest group of emerging pollutants as their consumption increased tremendously in recent years. Nanomaterials have gained much attention over the last decade in the development of sensors for a myriad of applications. The applicability of these nanomaterials, functionalized or not, significantly increases and it is therefore highly suitable for use in the detection of illicit drugs. We have assessed the suitability of various nanoplatforms, such as graphene (GPH), multi-walled carbon nanotubes (MWCNTs), gold nanoparticles (AuNPs) and platinum nanoparticles (PtNPs) for the electrochemical detection of illicit drugs. GPH and MWCNTs were chosen as the most suitable platforms and cocaine, 3,4-methylendioxymethamfetamine (MDMA), 3-methylmethcathinone (MMC) and α-pyrrolidinovalerophenone (PVP) were tested. Due to the hydrophobicity of the nanomaterials-based platforms which led to low signals, two strategies were followed namely, pretreatment of the electrodes in sulfuric acid by cyclic voltammetry and addition of Tween 20 to the detection buffer. Both strategies led to an increase in the oxidation signal of illicit drugs. Binary mixtures of illicit drugs with common adulterants found in street samples were also investigated. The proposed strategies allowed the sensitive detection of illicit drugs in the presence of most adulterants. The suitability of the proposed sensors for the detection of illicit drugs in spiked wastewaters was finally assessed.

Employment of electrostriction phenomenon for label-free electrochemical immunosensing of tetracycline.

The presented work describes a simple label-free electrochemical immunosensor for the determination of tetracycline (TC). The functioning of the sensor was based on the electrostriction of a antibody-terminated thiol layer self-assembled on a gold electrode surface, serving as a dielectric membrane. The intensity of electrostriction was correlated with the amount of TC captured through an affinity reaction with its specific antibody, and was followed in the form of capacitance-potential curves. The process of the immunosensor construction was optimized using electrochemical impedance spectroscopy (EIS). The chemisorption time of the thiol, the duration of the TCAb immobilization and its concentration were optimized. The developed immunosensor exhibited a linear response in two concentration ranges: from 0.95 to 10 µmol L-1 and from 10 to 140 µmol L-1, with the mean sensitivity of 6.27 nF µmol-1 L (88.67 nF µmol-1 L cm-2) and 0.56 nF µmol-1 L (7.84 nF µmol-1 L cm-2), respectively. The limit of detection was evaluated as 28 nmol L-1. The specificity of the proposed sensor toward other antibiotics, amoxicillin and ciprofloxacin, was examined. The immunosensor was successfully employed to quantify TC in a tablet form and in a matrix of river water.

Electrochemical Sensor Based on Molecularly Imprinted Polymer for the Detection of Cefalexin.

In this study, a new electrochemical sensor was developed for the detection of cefalexin (CFX), based on the use of a molecularly imprinted polymer (MIP) obtained by electro‒polymerization in an aqueous medium of indole-3-acetic acid (I3AA) on a glassy carbon electrode (GCE) and on boron-doped diamond electrode (BDDE). The two different electrodes were used in order to assess how their structural differences and the difference in the potential applied during electrogeneration of the MIP translate to the performances of the MIP sensor. The quantification of CFX was performed by using the electrochemical signal of a redox probe before and after the rebinding of the template. The modified electrode was characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The influence of different parameters on the fabrication of the sensor was tested, and the optimized method presented high selectivity and sensitivity. The MIP-based electrode presented a linear response for CFX concentration range of 10 to 1000 nM, and a limit of detection of 3.2 nM and 4.9 nM was obtained for the BDDE and the GCE, respectively. The activity of the sensor was successfully tested in the presence of some other cephalosporins and of other pharmaceutical compounds. The developed method was successfully applied to the detection of cefalexin from real environmental and pharmaceutical samples.

Electrochemical surface plasmon resonance (EC-SPR) aptasensor for ampicillin detection.

Surface plasmon resonance technique is highly sensitive to various processes taking place on a metal film and it has emerged as a powerful label-free method to study molecular binding processes taking place on a surface. Another important but less explored area of applications is the use of hybrid methods which combine electrochemistry with optical methods for better monitoring and understanding of biochemical processes. A detection method based on surface plasmon resonance was developed for ampicillin, applying electrochemical techniques for the elaboration and characterization of the aptasensing platform used in this study. Ampicillin is a broad-spectrum ß-lactam antibiotic, used both in human and veterinary medicine for the treatment and prevention of primary respiratory, gastrointestinal, urogenital, and skin bacterial infections. It is widely used because of its broad spectrum and low cost. This widespread use can result in the presence of residues in the environment and in food leading to health problems for individuals who are hypersensitive to penicillins. The gold chip was functionalized through potential-assisted immobilization, using multipulse amperometry, first with a thiol-terminated aptamer, as a specific ligand and secondly, using the same procedure, with mercaptohexanol, used to cover the unoccupied binding sites on the gold surface in order to prevent the nonspecific adsorption of ampicillin molecules. After establishing the optimal conditions for the chip functionalization, different concentrations of ampicillin were detected in real time, in the range of 2.5-1000 µmol L-1, with a limit of detection of 1 µmol L-1, monitoring the surface plasmon resonance response. The selectivity of the aptasensor was proven in the presence of other antibiotics and drugs, and the method was successfully applied for the detection of ampicillin from river water. Graphical abstract ᅟ.

Electrochemical determination of cephalosporins using a bare boron-doped diamond electrode.

The electrochemical oxidation of seven cephalosporins (ceftriaxone, cefotaxime, ceftazidime, cefadroxil, cefuroxime, cefaclor, cefalexin) was evaluated at high potential, using a bare boron-doped diamond electrode and the influence on the analytical response of the side chains was investigated. Based on the anodic oxidation of the cephalosporin nucleus, a simple and sensitive method was developed for the electrochemical detection of cefalexin by differential pulse voltammetry. After the optimization of the experimental conditions, a linear correlation was obtained between the peak height and the molar concentration of cefalexin in the range of 0.5 µM-700 µM, with a limit of detection of 34.74 ng mL-1. The anodic peak for cefalexin was evaluated in the presence of other cephalosporin molecules and of other common interferents. The developed method was applied to detection of cefalexin from real environmental, biomedical and pharmaceutical samples, with good results. The electrochemical oxidation of cephalosporins was successfully adapted for flow injection analyses, with sensitive and reproducible successive analyses of cefalexin, in different concentrations. The flow analyses allowed also the determination of the total amount of cephalosporins found in the sample.

Electrochemical Impedance Studies on Single and Multi-Walled Carbon Nanotubes--Polymer Nanocomposites for Biosensors Development.

Advances in nanoscience have allowed scientists to incorporate new nanomaterials in biosensing platforms. Carbon nanotubes are nanomaterials that facilitate the charge transfer between the bioelement and the transducer. Electrochemical impedance spectroscopy is a useful technique for the modified surface characterization. In the present approach electrochemical impedance spectroscopy was used to characterize the electrodes modified with different types of carbon nanotubes (single and multi-wall) according to their morphology and electrochemical behavior. By using Nyquist and Bode diagrams it was possible to assign the appropriate circuit considering all possible contributors. The charge transfer resistances as well as the time constants were calculated for all five types of investigated carbon nanotubes.