The Polar Star project was launched in June 2019. Progress of the project has been severely compromised by the COVID-19 pandemics since its outbreak in Italy in February 2020. Access to the lab facilities near the CNR was strongly limited since then. Further, travel restrictions did not allow the IF to make two secondments near CycloLab in Budapest and near the Erasmus Medical Center (EMC) in Rotterdam. Consequently, only a part of the objectives was achieved as we will describe below.
The work was organized into four actions: i) synthesis of the polymeric carriers, ii) Loading of the carriers with multiple therapeutics, iii) Biological assays of the new drug loaded carriers, iv) Study of the drug/carrier systems in PC 3D models. In short, WP1 and WP2 activities have been completed satisfactorily, while the activities of WP3 were initiated in collaboration with the EMC and the University of Bologna, and those of WP4 were not executed due to time shortage. These last activities are currently ongoing near EMC in Rotterdam.
Results:
WP1 Synthesis of CyD polymers: The partner CycloLab Srl prepared new CyD polymers using a consolidated protocol based on polycondensation of natural CyDs in the presence of epichlorohydrin in aqueous alkaline environment. The synthesis has already been reported for polymers of single CyD and they used the same approach to prepare mixed CyD polymers.
WP2 Preparation and characterization of the new drug/carrier assemblies: We used 5 polymers, prepared in WP1, paCyD, pbCyD, pgCyD, pabCyD, and pbgCyD. We focused on drugs proposed for the treatment of CRPC like Cabazitaxel, Bicalutamide and Enzalutamide. These drugs display serious drawbacks related with their low aqueous solubility and with the onset of severe side effects, forcing administration in tolerable doses. As photosensitizer we considered Mitoxantrone, a cancer drug, and Chlorin e6, a well known singlet oxygen sensitizer. Electronic absorption spectroscopy was used to estimate the amount of loaded drug and circular dichroism and fluorescence were further exploited to confirm encapsulation. We obtained the maximum solubility data for cabazitaxel, bicalutamide and enzalutamide or their combinations. We collected the binding constants for the drug/carrier systems displaying the most interesting solubility profile. This WP was completed with a study of the interaction of the polymers with Mitoxantrone and chlorin e6. Only Chlorin e6 exhibits good affinity for the polymers. For the polymers displaying the best profile in solubilizing a drug we assessed the stability of the solution over time. We used DLS to investigate the dimension of the loaded polymers assembling in particles with a size below 20 nm.
WP3 Biological 2D assays: More than one drug/carrier combination emerged from WP2 and in the short time left we performed the first biological tests with the pbCyD solubilizing BIC, CBX and both in collaboration with UNIBO and the EMC where CRPC cell lines are available. The first results obtained with MTT assay on a CRPC cell line show that cell proliferation is similar for the drugs alone and for the drugs loaded by the polymer. Further investigations are required to complete the data with the other dug carrier systems as well as the investigation of the phototoxicity when one of the drugs is coloaded with chlorin e6.
WP4:Biological performance of the new drug/carrier systems in 3D PC models: This WP has not been addressed up to now.
