|Ph.D Student||Schlachet Inbar|
|Subject||Innovative Mucoadhesive Nano-Biomaterials for the|
Encapsulation of Anti-Cancer Drug Candidates in
the Treatment of Pediatric Brain Tumors
|Department||Department of Materials Science and Engineering||Supervisor||Professor Alejandro Sosnik|
Tumors of the central nervous system (CNS) are the leading cause of childhood death due to cancer. Around 10-15% of the CNS tumors in children are diffuse intrinsic pontine gliomas (DIPG), the most aggressive and deadly pediatric CNS cancer. DIPG is a tumor with fully conserved blood-brain barrier (BBB), the anatomical barrier that controls the trafficking of molecules from the systemic circulation into the CNS. Two candidate drugs that inhibit different pathways upregulated in DIPG were examined, namely signal transducer and activator of transcription 3 (STAT3) and the activin A receptor type I (ACVR1).
The well-conserved BBB and the extremely low aqueous solubility of these drugs might compromise the bioavailability in the CNS after intravenous (i.v.) administration. The direct nose-to-brain transport pathway that bypasses the BBB is a very promising approach to target nano-encapsulated drugs to the CNS. The implementation of a nanotechnology would be beneficial to improve the state-of-the-art treatment of DIPG. Polymeric micelles and other amphiphilic polymeric nanoparticles emerged as potential nanotechnology platform for drug delivery to the CNS intranasally.
In this Thesis, we investigated and characterized mucoadhesive amphiphilic mixed nanoparticles made of chitosan (CS) and/or poly(vinyl alcohol) (PVA) that were hydrophobized with poly(methyl methacrylate) (PMMA) blocks and used them for the encapsulation of STAT3 and ACVR1 inhibitors agents WP1066 and LDN-212854, respectively. Initially, we evaluated the ability of CS-based nanoparticles to cross a model of epithelium in vitro in the Caco-2 cell monolayer model and found that the nanoparticles cross it by a paracellular pathway. Then, we synthesized and characterized two amphiphilic graft copolymers, CS-g-PMMA and PVA-g-PMMA. The aggregation behavior of CS-g-PMMA was assessed by complementary techniques that included small-angle neutron scattering and light scattering analysis. Our results confirmed that these nanoparticles are formed by the aggregation of small nanoparticles clustered together into larger units. Due to the substantial cell toxicity of CS-based nanoparticles, we produced mixed CS-g-PMMA:PVA-g-PMMA nanoparticles that preserve the encapsulation capacity and show better cell compatibility. These mixed nanoparticles were physically stabilized by the non-covalent crosslinking of CS domains and the size was in good range for intranasal (i.n.) administration (~200 nm). In addition, the cell compatibility and uptake of these nanoparticles was evaluated in patient-derived DIPG cells and different cell types of the CNS. Then, the permeability of these nanoparticles was confirmed in monolayers of a nasal epithelium cell line, RPMI 2650, using two interfaces. The encapsulation of both drugs was achieved by the solution casting method with good drug loading capacity. In addition, the implementation of a microfluidics device increased the stability of the nanoparticles. Then, the anti-cancer activity of both compounds was estimated by measuring the inhibitory concentration 50 (IC50) in DIPG neurospheroid cells. The drugs display high anti-DIPG efficacy in vitro though no synergy. Similar IC50 values were measured after nano-encapsulation. Finally, the biodistribution of the nanoparticles after i.n. and i.v. administration was evaluated in ICR mice. Results suggested that mixed nanoparticles efficiently reach the brain upon i.n. administration as opposed to i.v..