טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentImrit Noi
SubjectDesign and Synthesis of Novel Multifunctional Mucoadhesive
and Mucopenetrating Self-Assembly Nanocarriers
for Drug Delivery
DepartmentDepartment of Materials Science and Engineering
Supervisor Professor Sosnik Alejandro
Full Thesis textFull thesis text - English Version


Abstract

Transmucosal delivery emerged as a promising strategy to improve the pharmacokinetics of drugs. However, it remains a big challenge due to the complex structure of the mucus, which might preclude drug permeability. The mucus is a viscoelastic layer formed by crosslinked mucin fibers, that covers all exposed epithelial tissues not covered by skin. The engineering of drug nanocarriers combining fine-tuned mucoadhesive and mucopenetrating is currently being investigated to ensure more efficient mucosal delivery of the active agents. Mucoadhesion is essential to prolong its residence time in mucosa. In this context, thiolated polymers are a relatively new family of biomaterials with thiol pendant chain groups and have emerged as a versatile approaches to confer mucoadhesiveness. Conversely, mucopenetration entails the facilitation of the nanocarrier passage across it. Our research group investigates nanocarriers for mucosal delivery of hydrophobic drugs by different administration routes with special interest in amphiphilic nanomaterials. In this context, we synthesized a thiolated poly(ethylene oxide)-b-poly(propylene oxide) (PEO-PPO) and attempted to use it to produce thiolated polymeric micelles (PMs). The chemical characterization of the modified copolymer revealed very low modification extent. This low thiolation extent precluded the investigation of the influence of thiol modification on the permeability of these PMs.


Further on, aiming to understand the effect of thiolation on the permeability of nanoparticles, Here we report on the synthesis and characterization of amphiphilic nanocarriers produced by the ionotropic crosslinking of chitosan-g-poly(methyl methacrylate) (CS-g-PMMA) that were modified with two types of thiol residues, N-acetyl cysteine (NAC) and 3-mercaptopropionic acid (3MPA). We successfully conjugated 3% and 0.5% w/w of NAC and 3MPA, respectively, determined by the Ellman’s colorimetric assay. The critical micellar concentration (CMC) of these copolymers was in the 0.04-0.05% w/v range, measured by dynamic light scattering (DLS). In addition, size and size distribution measured by the same technique, indicated a range between 100 and 300 nm that would fit the size of the mesh-like structure of the mucus layer. Ionotropically crosslinked nanoparticles showed good cell compatibility in two cell lines (Caco2 and HT29-MTX) that are relevant to oral delivery in a 0.05-0.1% w/v range after 4-48 h; Caco2 cells and HT29-MTX cells together mimic better the intestinal barrier. Finally, studies conducted in both Caco2 and Caco-2/HT29-MTX monolayers in Transwell? systems were used to compare the effect of the crosslinking, the nanoparticle concentration and the thiolation on the permeability in vitro. Results indicated that the ability of the nanoparticles to cross the Caco2 monolayer is affected by the crosslinking. In addition, NAC-modified nanoparticles interact more strongly with the mucus layer, resulting in a decrease of the permeability coefficient (Papp) compared to the pristine copolymer. The performance of nanoparticles modified with 3MPA was similar to that of the pristine copolymer most probably due to a lower modification extent of 0.5% w/w. Moreover, in all PMs, for both Caco2 and co-culture monolayers, 0.05% w/v concentration resulted in a lower Papp than for 0.01% w/v systems, suggesting that the transport pathways are saturated.