Vancomycin (VAN) is a glycopeptide antibiotic, active against Gram-positive bacteria resistant to other antibiotics. VAN therefore needs to be monitored for maximum efficacy and minimum toxicity. ...Electrochemical sensors can be used for this purpose, using the direct electrochemical signal of VAN. Due to its molecular complexity and the need for analysis from complex matrices, the electrochemical detection of VAN requires the development of a complex electrochemical fingerprint (CEF), which covers a large variety of possible combinations of samples and interferents at concentrations of interest.
The objective of this study was to develop a CEF for VAN, involving a battery of tests and the elucidation of the mechanism of anodic oxidation of VAN, using high-performance liquid chromatography coupled with mass-spectrometric analysis of the products obtained after small-scale electrolysis.
A CEF for VAN was obtained, describing the electrochemical behavior of VAN at different commercially available screen-printed electrodes, with several electrolytes, considering successive analyses, after simple pretreatments, and examining both anodic and cathodic peaks. The concept was successfully applied to analysis of VAN in real samples and in the presence of some common interferents. Furthermore, a two-step combined electrochemical–chemical mechanism was proposed for the electrooxidation of VAN.
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•Therapeutic drug monitoring of vancomycin is needed for maximum efficacy.•A battery of tests with different commercially available SPEs was performed.•Both anodic and cathodic electrochemical analyses were performed.•A complex 3D electrochemical fingerprint for vancomycin was produced.•A mechanism for anodic oxidation of vancomycin was proposed.
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.
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)64−/Fe(CN)63−. 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).
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
β
-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.
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•Electrodeposition of five new gold platforms at screen printed electrodes.•Morphology and topography are strongly influenced by the deposition procedure.•Ferrocene-Aptamer ...immobilization was investigated at five gold platforms.•The thistle-like structures were optimal for aptasensor development.•The aptasensor displayed good recovery values towards Oxytetracycline in milk samples.
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.
The use of a photocatalyst (photosensitizer) which produces singlet oxygen instead of enzymes for oxidizing analytes creates opportunities for designing cost-efficient and sensitive ...photoelectrochemical sensors. We report that perfluoroisopropyl-substituted zinc phthalocyanine (F
PcZn) interacts specifically with a complex phenolic compound, the antibiotic rifampicin (RIF), but not with hydroquinone or another complex phenolic compound, the antibiotic doxycycline. The specificity is imparted by the selective preconcentration of RIF in the photocatalytic layer, as revealed by electrochemical and optical measurements, complemented by molecular modeling that confirms the important role of a hydrophobic cavity formed by the
-perfluoropropyl groups of the photocatalyst. The preconcentration effect favorably enhances the RIF photoelectrochemical detection limit as well as sensitivity to nanomolar (ppb) concentrations, LOD = 7 nM (6 ppb) and 2.8 A·M
·cm
, respectively. The selectivity to RIF, retained in the photosensitizer layer, is further enhanced by the selective removal of all unretained phenols via simple washing of the electrodes with pure buffer. The utility of the sensor for analyzing municipal wastewater was demonstrated. This first demonstration of enhanced selectivity and sensitivity due to intrinsic interactions of a molecular photocatalyst (photosensitizer) with an analyte, without use of a biorecognition element, may allow the design of related, robust, simple, and viable sensors.
The most important and well-known glycopeptide antibiotic, vancomycin (VAN), is used for the treatment of severe bacterial infections like methicillin-resistant staphylococcal infections and ...endocarditis caused by enterococci and sepsis. Taking into account the problem of the development of antibiotic resistance as well as its toxicity, both correlated with the VAN concentration (CVAN) in biological samples, there is need for better and more accessible quantification methods for this antibiotic. Considering all of the above, herein, we present a simple electrochemical method for VAN sensing based on a hybrid graphene-gold nanostructure nanocomposite electrode, which allows double detection directly in the oxidation domain and also indirectly, in reduction, using the electro-active gold nanostructures as a probe to monitor the current changing due to the interaction between gold and VAN. The developed method was able to successfully detect VAN in the linear range of 1–100 µM with a limit of detection (LOD) of 0.29 µM for the direct approach and 0.5 µM for the indirect one. The selectivity of the method was tested in the presence of other antibiotics and drugs. This method was successfully applied for the detection of VAN from human serum samples.
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