Speakers:

Giulia De Soricellis - Targeted NIR biolabeling via fluorophore confinement in engineered PLGA nanocarrier

Fluorescence-guided imaging is a powerful non-invasive technique for real-time in vivo visualization of biological processes in vivo. However, achieving high imaging performance requires fluorophores that combine deep tissue penetration¹, high brightness and minimal interference from tissue autofluorescence.

Near-infrared (NIR) fluorophores are particularly attractive because biological tissues exhibit reduced absorption and scattering within the NIR optical window. Nevertheless, their poor aqueous solubility and tendency to aggregate often limit their direct biomedical application.

To overcome these limitations, biodegradable poly(lactic-co-glycolic acid) (PLGA) nanoparticles were engineered by nanoprecipitation² to encapsulate hydrophobic NIR fluorophores. The formulation was systematically optimized to obtain monodisperse nanoparticles with controlled physicochemical and photophysical properties, while providing a platform suitable for subsequent surface functionalization toward targeted imaging.

¹ Lei, Z.; Zhang, F., Angew. Chem. Int. Ed , 2021, 60, 16294
² Trofymchuk et al., J. Mater. Chem. B 2019, 7, 5199–5210

Andrea Chimarro Contreras - Towards the molecular design of efficient oxime esters photoinitiators for 3D printing

Oxime esters have arisen as promising photoinitiators for two-photon laser writing, due to its favorable two-photon absorption and to its ability to form highly reactive carbon-centered radicals that can trigger free-radical polymerization. Three new promising oxime esters were synthesized and characterized at the Laboratoire de Chimie de l'ENS Lyon, which proved to be useful photoinitiators, but still show limited two-photon absorption cross-sections and high fluorescence. Motivated by these results, we carried out computational studies on these systems to unveil their photocleavage mechanism in order to understand how photodissociation can be enhanced.

In this work, we modelled the photo induced dissociation of the three oxime esters using static and dynamic approaches. Our results show that photodissociation requires a loss of molecular planarity induced by rotation about a chemical bond. Furthermore, photoisomerization and photodissociation are competitive deactivation pathways. In conclusion, the photodissociation process in these systems is hindered by the need for a previous rotation, pointing out the directions towards a molecular design of more efficient oxime esters for 3D printing applications.