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    Engineering gold nanoparticles aggregation in acrylate hydrogel-photopolymers for SERS-based on-site highly sensitive dimethoate detection on olives
    (Elsevier Sci Ltd, 2025) Yilmaz, Deniz; Miranda, Bruno; Nocerino, Valeria; Esposito, Alessandro; Rea, Ilaria; Lonardo, Enza; De Luca, Anna Chiara
    Hydrogel-based flexible plasmonic devices represent a cutting-edge technology for real-time monitoring of food safety, particularly for pesticide detection. This study presents a cost-effective, portable, and sensitive method to detect dimethoate (DMT), a hazardous organophosphorus pesticide, at concentrations below the maximum residue limit (MRL) of 0.01 ppm on olives. By integrating surface-enhanced Raman scattering (SERS) with gold nanoparticles (AuNPs) embedded in polyethylene glycol diacrylate (PEGDA) hydrogels, detection at parts-per-billion (ppb) levels is achieved. The hydrogel matrix enhances sensitivity and reproducibility by forming AuNP dimers, whose concentration increases with DMT levels, boosting signal output. The system uses UV polymerization of a pre-polymer solution, enabling direct application onto olive surfaces and achieving a detection limit of 3 ppb with a signal enhancement of similar to 10(6). Tests with fungicides (RidoMil, Glyphosate) confirmed excellent selectivity for DMT. Validated on-site with a portable Raman spectrometer, this method is adaptable for detecting sulfur-containing pesticides, offering a practical solution for food safety.
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    PNA-SERS biosensor for label-free detection of SARS-CoV-2 genomic sequences in saliva
    (Elsevier, 2025) Esposito, Alessandro; Martino, Sara; Yilmaz, Deniz; Mangini, Maria; De Stefano, Luca; Corteggio, Annunziata; De Luca, Anna Chiara
    The COVID-19 pandemic has emphasized the need for rapid, sensitive, and accessible molecular diagnostics. In this study, we present a label-free Surface-Enhanced Raman Spectroscopy (SERS) biosensor for the direct detection of SARS-CoV-2 RNA in biological fluids. The proposed sensor is based on a thiolated Peptide Nucleic Acid (PNA) probe immobilized on colloidal gold nanoparticles (AuNPs) deposited on functionalized glass substrates. A stable and selective hybridization with target sequences is provided by the intrinsic characteristics of PNA molecules, such as neutral backbone, high sequence affinity and enzymatic resistance. Whereas AuNPs enables strong signal enhancement and excellent reproducibility, without requiring complex nanofabrication techniques. Overall, the biosensor fabrication relies entirely on standard laboratory procedures and commercially available reagents, making it cost-effective and easily scalable. The detection of the target RNA occurs through label-free SERS, responsible for amplifying the vibrational fingerprint of nucleobases. Multivariate analysis through principal component analysis (PCA) and regression (PCR) further enhances spectral discrimination and detection sensitivity. The sensor exhibits a limit of detection of 110 pM, falling within the clinically relevant range of salivary SARS-CoV-2 RNA concentrations. Detection performance was assessed in both buffer and artificial saliva, demonstrating the potential of the platform for use with real biological samples. Moreover, the device demonstrates high selectivity, effectively distinguishing between fully matched, mismatched, and random sequences. This work highlights the potential of PNA-SERS biosensors for rapid, amplification-free viral RNA detection and offers a promising approach for point-of-care diagnostics in infectious diseases.