Synthesis, Self-assembly And Biological Evaluation Of PH Responsive Cell Membranes Mimetic Chitosan Derivatives

Novel biomimetic p H-responsive chitosan derivative, N-Acetyl-L-Histidinephosphorylcholine-chitosan conjugate(NAc His-PCCs) was synthesized based on the combination of Atherton-Todd reaction for coupling phosphorylcholine(PC) and carbonyldiinidazole coupling reaction for linking N-Acetyl-L-Histidine(NAc His) to chitosan. NAc His-PCCs with different degrees of substitution(DS, mol%) for PC and NAc His can be achieved by changing the feed rate of related reactants, which was measured by 1H-NMR and element analysis, respectively. The chemical structure of NAc His-PCCs was investigated by NMR and FT-IR, which confirmed the successful conjugation of PC and NAc His to chitosan. p H trivation result revealed the critical point for thoroughly transition of phosphodicholine-chitosan(Pd CCs) to phosphorylcholine-chitosan(PCCs) to be 8.43. The water structure in NAc His-PCCs was investigated by DSC and the appearance of cold crystallization peak proved the existence of freezing bound water which implied good biocompatibility. In order to get a good hydrophilic /hydrophobic balance for self-assembly, NAc His-PCCs with DSs of 42% and 12.4% for PC and NAc His was used for further investigation.Blank NAc His-PCCs nanoparticles were prepared by ultrasonic vibration method in distilled water, the self-assemble ability of NAc His-PCCs was analyzed by pyrene fluorescence probe, dynamic laser light-scattering(DLS) and electron microscopy technologies. The particle size of NAc His-PCCs nanoparticles measured was ~367 nm, with its CMC value to be 6.9 × 10-3 mg/m L which guaranteed a good stability. Blank NAc His-PCCs nanoparticles showed a p H responsive size change with its particle size doubled when its matrix p H bellows 6.0. Hemocompatibility, cytotoxicity together with BSA protein interaction study results showed NAc His-PCCs nanoparticles had good biocompatibility.Potential anti-cancer drug Quercetin(QUE) was loaded into NAc His-PCCs complexes by solvent evaporation method, and its releasing ability under different p H(5.5, 7.4) was investigated, which showed a fast release in acidic matrix while a slow release in neutral matrix. All biocompatibility assays, drug loading and releasing ability showed NAc His-PCCs was a promising p H responsive nano-carrier for drug delivery.