Optimisation of alendronate conjugation to polyethylene glycol for functionalisation of biopolymers and nanoparticles

Chitosan-Based Nanoparticles for Twist1 Knockdown in 4T1 Cells

Bone metastasized breast cancer reduces the quality of life and median survival. Targeted delivery of twist1-siRNA using nanoparticles (NPs) is a promising strategy to overcome current limitations in treating such metastatic breast cancers. This research evaluates two types of chitosan (CHI)-based NPs for the delivery of twist1-siRNA. Alendronate conjugated PEG functionalized chitosan (ALD-PEG-CHI) NPs are developed for active targeting while PEG functionalized CHI (mPEG-CHI) NPs are fabricated for passive targeting. The size of twist1-siRNA-loaded NPs is below 70 nm and the zeta potential is near neutral for both types of NPs. Based on gel retardation assay, complete encapsulation of twist1-siRNA is achieved in both NP systems. The ALD-PEG-CHI-siRNA and mPEG-CHI-siRNA NPs display serum protection for 6 and 4 h, respectively, compared to the immediate degradation of naked twist1-siRNA. The NPs can knockdown twist1 in 4T1 cells as demonstrated through protein expression as well as by phenotypic change in directional cell migration by wound healing assay. Overall, these in vitro results illustrate the potential of the NPs as an effective therapeutic system for bone metastasized breast cancer.

Targeted Nanoparticles Based on Alendronate Polyethylene Glycol Conjugated Chitosan for the Delivery of siRNA and Curcumin for Bone Metastasized Breast Cancer Applications

Bone metastasized breast cancer reduces the quality of life and median survival. Targeted delivery of small interfering RNA (siRNA) and chemotherapeutic drugs using nanoparticles (NPs) is a promising strategy to overcome current limitations in treating these metastatic breast cancers. This research develops alendronate conjugated polyethylene glycol functionalized chitosan (ALD-PEG-CHI) NP for the delivery of cell death siRNA (CD-siRNA) and curcumin (CUR) and explores its targeting ability and in vitro cell cytotoxicity. Polyethylene glycol functionalized CHI (mPEG-CHI) NPs serve as control. The size of CD-siRNA loaded NPs is below 100 nm while CUR loaded NPs is below 200 nm, with near neutral zeta potential for all NPs. The CUR encapsulation efficiency (EE) is 70% and 88% for targeted and control NPs, respectively, while complete encapsulation of CD-siRNA is achieved in both NP systems. The bone targeting ability of CY5-dsDNA loaded ALD-PEG-CHI NPs using hydroxyapatite discs is fivefold compared to control indicating ALD presentation at the targeting NP surface. Delivery of CD-siRNA loaded NPs and CUR loaded NPs show synergistic and additive growth inhibition effects against MCF-7 cells by mPEG-CHI and ALD-PEG-CHI NPs, respectively. Overall, these in vitro results illustrate the potential of the targeted NPs as an effective therapeutic system toward bone metastasized breast cancer.

Characterisation of products from EDC-mediated PEG substitution of chitosan allows optimisation of reaction conditions

PEGylation is a common method use to modify the physiochemical properties and increase the solubility of chitosan (CHI). Knowledge of optimal reaction conditions for PEGylation of CHI underpins its ongoing use in nanomedicine. This study synthesised methoxy polyethylene glycol grafted CHI (mPEG-CHI) using carbodiimide-mediated coupling. The effect of reagent concentrations and pH on the degree of substitution (DS) and the PEGylation yield (conversion of free PEG to conjugated PEG) was evaluated through detailed chemical characterisation. Within the parameter space investigated, optimised reaction conditions (NH₂: COOH:NHS:EDC of 3.5:1:1:10, pH = 5) resulted in a DS of 24 % and a PEGylation yield of 84 %. An EDC-derived adduct formed at pH ≥ 5.5 and a at 15-fold excess of EDC relative to COOH. The adduct was evaluated to be a guanidine derivative formed by the reaction of the amine group of CHI directly with EDC. DS ≥ 12 imparted water solubility to CHI at physiological pH and mPEG-CHI (0.2-1.0 mg/mL) was not cytotoxic against the breast cancer cell lines MCF-7 and MDA-MB-231, indicating its suitability for medical applications.