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Imidacloprid is the most widely used insecticide in agriculture and its intensive use over the last 30 years has caused a global concern due to its potentially toxic effects on the ecosystem. Considering the recent scientific interest in novel simple methods for imidacloprid analysis, we propose a label-free sensitive and specific localised surface plasmon resonance system for the detection of the insecticide based on 2D nanostructured metasurfaces with highly performing plasmonic properties. The specificity of the sensor proposed was achieved by covalent bio-functionalization of the metasurface using a smart and easy one-step procedure mediated by carbon disulphide. The biosensor produced was tested using a set of imidacloprid standard solutions showing a competitive limit of detection, lower than 1 ng mL -1 . Our novel nanosensing configuration represents a valid and reliable solution to realize low-cost portable POC tests as an alternative to the laborious and expensive methods traditionally used for insecticide detection.

Background: Molecularly imprinted polymer (MIP) technique is a powerful mean to produce tailor made synthetic recognition sites. Here precipitation polymerization was exploited to produce a library of MIP nanoparticles (NPs) targeting the N terminus of the hormone Hepcidin-25, whose serum levels correlate with iron dis-metabolisms and doping. Biotinylated MIP NPs were immobilized to NeutrAvidin™ SPR sensor chip. The response of the MIP NP sensor to Hepcidin-25 was studied., Findings: Morphological analysis showed MIP NPs of 20-50 nm; MIP NP exhibited high affinity and selectivity for the target analyte: low nanomolar Kds for the interaction NP/Hepcidin-25, but none for the NP/non regulative Hepcidin-20. The MIP NP were integrated as recognition element in SPR allowing the detection of Hepcidin-25 in 3 min. Linearity was observed with the logarithm of Hepcidin-25 concentration in the range 7.2-720 pM. LOD was 5 pM. The response for Hepcidin-20 was limited. Hepcidin-25 determination in real serum samples spiked with known analyte concentrations was also attempted., Conclusion: The integration of MIP NP to SPR allowed the determination of Hepcidin-25 at picomolar concentrations in short times outperforming the actual state of art. Optimization is still needed for real sample measurements in view of future clinical applications.

In recent decades, there has been a strong and growing interest in developing strategies to engineer materials with tailored optical and plasmonic properties. In the plethora of geometries studied and proposed in the literature, nanostructures based on cluster arrangements known as "plasmonic molecules" (PMs) have shown several interesting properties and represent potential candidates to implement different types of opto-plasmonic applications. In this paper, we examine a fractal PM (FPM), analyzing its properties by numerical simulations based on the finite element method (FEM). Next, periodic arrangements of the FPM in two different configurations were fabricated by an electron beam lithography (EBL) process, and their plasmonic features were experimentally characterized. Our numerical simulations are in good agreement with the experimental results. Our study highlights noticeable features of the analyzed PM, such as multi-resonant and anisotropic properties, which can be exploited to design plasmonic devices with customized optical characteristics also compatible with multiple sensing applications. We tested the performance of our FPM for surface-enhanced Raman spectroscopy (SERS) sensing, realizing a functionalized system for the specific detection of the SARS-CoV-2. We tested different concentrations of the virus, obtaining a limit of detection (LOD) of 88 PFU/mL, lower than that of commercial rapid kits. Our results demonstrate that the proposed plasmonic nanopatterns are promising to develop integrable devices for a sensitive SERS detection in a portable point-of-care (POC) platform. [ABSTRACT FROM AUTHOR]