Novel Self-Assembled Micelles With Increased Tumor Penetration and Anti-Tumor Efficiency Against Breast Cancer

PURPOSE

Recently, docetaxel (DTX) micelles based on retinoic acid derivative surfactants showed lower systemic toxicity and bioequivalence to polysorbate-solubilized docetaxel (Taxotere®) in a phase II clinical study. However, the poor stability of these surfactants in vitro and in vivo led to extremely harsh storage conditions with methanol, and the formed micelles were quickly disintegrated with rapid drug burst release in vivo. To further enhance the stability and accumulation in tumors of DTX micelles, a novel surfactant based on acitretin (ACMeNa) was synthesized and used to prepare DTX micelles to improve anti-tumor efficiency.

METHODS

Novel micelle-forming excipients were synthesized, and the micelles were prepared using the thin film hydration technique. The targeting effect in vitro, distribution in the tumor, and its mechanism were observed. Pharmacokinetics and anti-tumor effect were further investigated in rats and tumor-bearing female mice, respectively.

RESULTS

The DTX-micelles prepared with ACMeNa (ACM-DTX) exhibited a small size (21.9 ± 0.3 nm), 39% load efficiency, and excellent stability in vitro and in vivo. Long circulation time, sustained and steady accumulation, and strong penetration in the tumor were observed in vivo, contributing to a better anti-tumor effect and lower adverse effects.

CONCLUSIONS

The micelles formed by ACMeNa showed a better balance between anti-tumor and adverse effects. It is a promising system for delivering hydrophobic molecules for cancer therapy.

Enhanced permeation by amphiphilic surfactant is spatially heterogenous at membrane and cell level

In the context of increased interest in permeability enhancement technologies to achieve mucosal delivery of drugs and biologics, we report our study on effects of the amphiphilic surfactant at cell membrane and cell population levels. Our results show that modulation in membrane order and fluidity initially occurs on insertion of individual surfactant molecules into the outer leaflet of membrane lipid bilayer; a process occurring at concentrations below surfactant's critical micellar concentration. The surfactant insertion, and consequent increase in membrane fluidity, are observed to be spatially heterogenous, i.e. manifested as 'patches' of increased membrane fluidity. At the cell population level, spatially heterogeneous activity of surfactant is also manifested, with certain cells displaying high permeability amongst a 'background' population. We propose that this heterogeneity is further manifested in a broad profile of intracellular and nuclear exposure levels to a model drug (doxorubicin) observed in cell population. The study points to heterogeneous nature of surfactant effects at cell membrane and cells in population levels.

Improving enzymatic hydrolysis of acid-pretreated bamboo residues using amphiphilic surfactant derived from dehydroabietic acid

In this work, amphiphilic surfactant was obtained using dehydroabietic acid from pine rosin and then pre-adsorbed with acid-pretreated bamboo residues (AP-BR) to block the residual lignin adsorption site, which is expected to improve its enzymatic digestibility. Results from cryogenic-transmission electron microscopy (Cryo-TEM) indicated amphiphilic surfactant with PEG with polymerization degree of 34 (D-34) aggregated to form worm-like micelles, which improved enzymatic hydrolysis yield of AP-BR from 24.3% to 71.9% by pre-adsorbing with 0.8 g/L. Amphiphilic surfactants pre-adsorbed on AP-BR could reduce hydrophobicity of AP-BR, adsorption affinity and adsorption capacity of lignin for cellulase from 0.51 L/g to 0.48-0.32 L/g, from 2.9 mL/mg to 1.8-1.4 mL/mg, and from 122.3 mg/g to 101.9-21.4 mg/g, respectively. These changed properties showed compelling positive contributions (R² > 0.9) for free enzymes in the supernatants and sequently for final enzymatic hydrolysis yield, which was caused by blocking non-productively hydrophobic adsorption between lignin and cellulase.