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.

An overview of the detection of serotonin and dopamine with graphene-based sensors.

The development of rapid and sensitive devices for the simultaneous detection of neurotransmitters has critical implications for the clinical field and for the management of several diseases. Parkinson's, Alzheimer's disease, autism, schizophrenia, depression and anxiety are major healthcare challenges for which early diagnostics and personalized therapy are of great concern. Carbon-based nanomaterials and especially graphene-based nanomaterials associated with different architectures have been extensively studied and continue to represent the first line of approach in the development of nanoplatforms for electrochemical sensors. The simultaneous detection of analytes represents a critical point that could be addressed by designing new materials with the capacity to resolve their electrochemical signals. The results can be presented as a matrix that offers a broader viewpoint toward the balance of the neurotransmitter levels that are correlated with clinical symptoms for personalized diagnosis. The goal is to describe and evaluate, in a critical manner, the elaboration of graphene-based sensors that can be included in clinical applications. A major check point discussed throughout the paper is represented by the interference between different neurotransmitters that appear due to their overlapping signals and the strategies to address them to achieve simultaneous detection of as many molecules as possible and to be similar to in vivo experiments.