Luminescent probes for the detection of micro- and nanoplastics

Nanomaterial-based probes are promising tools for sensing applications due to their customizable interactions and signal amplification capabilities. Their integration with luminescent transducers can merge the advantages of nanomaterials in terms of selectivity and sensibility with the qualities of luminescence methods, including velocity, simplicity, and cost-effectiveness. Indeed, this PhD thesis describes the synthesis, characterization, and application of luminescent nanostructured probes for environmental and biomedical purposes, particularly for detecting micro- and nanoplastics (MNPs). MNPs pose significant environmental concerns due to their ubiquity and potential harm to ecosystems and human health. Their detection and characterization are challenging; in this context, promising tools are photoluminescence-based techniques, particularly through fluorescence microscopy after the staining with suitable probes. The luminescent probes for MNPs detection presented in this thesis are primarily fluorogenic hyaluronic acid (HA) derivatives. Indeed, through functionalization with different luminescent dyes, hyaluronan derivatives showed an enhanced brightness upon interaction with reference materials presenting a soft polymeric shell – Pluronic Silica (PluS) nanoparticles – and MNPs, facilitating their detection using fluorescence microscopy. Additionally, fluorescence lifetime imaging microscopy (FLIM) enables a discrimination of different types of stained plastics based on their emission lifetimes. The thesis also explores the photophysical features of promising dyes for HA functionalization and investigates co-staining methods for identifying MNPs in complex samples. Furthermore, it describes ratiometric probes for MNPs based on PluS nanoparticles, which can offer the potential for on-site monitoring with integration into a portable platform. Finally, this thesis presents aptasensors based on gold and PluS nanoparticles for biomedical applications. These sensors exhibit fluorescence enhancement or emission colour change upon interaction with target nucleic strands, demonstrating potential in solution and on paper devices. Overall, this thesis represents a promising advancement in luminescent nanomaterial-based sensors, with applications in environmental monitoring and biomedicine, highlighting the potential of biocompatible water-soluble polymers and nanoparticles as sensors.