The objective of WP1 consisted in the design and optimisation of nanoprobe capable of acting as contrast media for SPCCT and therapeutic agent with X-PDT.
The work initially focused on the design of inorganic scintillator cores. These scintillator cores were developed reproducibly with controlled sizes (10 nm) and crystallinities. Terbium (III) was used as a dopant in a GdF3 matrix, highlighting the significant impact of the Gd/Tb ratio on the luminescent properties of the nanoparticles (NPs). The studies also demonstrated the role of the GdF3 matrix and energy transfer to Tb3+ in inducing its luminescence under both X-ray and UV irradiation. Additionally, imaging studies with SPCCT showed the potential of these systems to act as contrast agents for conventional CT imaging and K-edge imaging. As a result, Gd0.90Tb0.10F3 NPs emerged as promising candidates for applications in XPDT and imaging.
Once the scintillator core was developed, surface modifications were performed using various types of ligands to enable applications in imaging and treatment. These modifications aimed to ensure both the biocompatibility of the systems and the retention of the scintillating properties of the inorganic cores. The work involved studying several types of molecules and macromolecules for surface grafting, including PEG phosphonate, tripolyphosphate, and silica layer (SiO2).
Cellular studies demonstrated that the surface-modified nanoparticles were biocompatible, exhibited high chemical stability, and showed better internalization in tumor cell lines compared to healthy ones.
Additionally, studies on the modified NPs using spectral scanning revealed that they maintained high contrast for both conventional CT imaging and K-edge imaging techniques. At this point a proof of concept was made on the ability of these nanoparticles to act as multimodal contrast agent for in vivo imaging with the SPCCT.
Following these studies on luminescent properties and biocompatibility, the most promising candidates for applications as contrast agents and for XPDT treatment were the systems modified with PEG and Silica.
Once the biocompatible nanoparticles were developed and their contrast agent properties validated, surface modifications were needed to link a photosensitizer for XPDT applications. Rose Bengal (RB) was chosen due to its excellent absorption properties in the wavelength range corresponding to Tb3+ emission. In the case of PEG systems, a two-step approach allowed for the development of biocompatible nanoprobes with up to a hundred molecules of rose bengal per nanoparticle. In the case of silica-based systems, entrapment of rose Bengal within the silica layer was performed.
In vitro studies confirmed the robustness of the surface modification, showing colocalization of the inorganic core elements and the iodine in the rose bengal structure, indicating that rose bengal is not released in a biological environment.
The last step consisted in studying the ability of these systems to generate reactive oxygen species (ROS) via XPDT treatment. Under UV irradiation, the use of probe molecules such as DPBF and ABDA demonstrated the nanoparticles' capacity to generate ROS. The studies revealed that the systems presenting best balance between amount of rose Bengal and colloidal stability were the most promising for generating ROS under UV irradiation. These results were further supported by studies using X-ray irradiation with the SPCCT. Complete degradation of the DPBF molecules were observed only in the presence of the nanoprobes after less that 1 min or irradiation (1,2 Gy).
In WP2, it was shown, using varying approaches described in the different tasks, that nanohybrids make tumor cells more sensitive to irradiation, especially at doses relevant for clinical daily fractionation treatment delivery, without enhancing toxicity to healthy tissue. Currently, results are being prepared as manuscripts for publication.
The Spectral Photon Counting CT scanner, SPCCT, enables the SCANnTREAT concept providing the required imaging, quantification, and activation of the nanoparticles developed in this research program. Using Photon-counting technology enables direct measurement of the absorption of the selected k-edge atoms. Optimized scan and reconstruction parameters are directed to maximize the sensitivity and quantification accuracy of the k-edge component. In WP3, the major results were:
- Enhancing detectability and threshold of gadolinium detection to 0.1 mg/mL
- (denoising algorithm)
- In vitro / In vivo dose effect and luminescence modulation by X ray parameters modulation
- Feasibility and proof of concept: treatment by 2 different types of nanoparticles with different surface functionalization
- Asses local biodistribution of the nanoparticles
- Tolerance of injection and no premature adverse effects after local injection
Trend towards increased efficacy in the Silicat + RB group compared to the control Silicat group, but results need to be tested on a larger number of animals
