SN-38 loading capacity of hydrophobic polymer blend nanoparticles: formulation, optimization and efficacy evaluation.

One of the most important problems in nanoencapsulation of extremely hydrophobic drugs is poor drug loading due to rapid drug crystallization outside the polymer core. The effort to use nanoprecipitation, as a simple one-step procedure with good reproducibility and FDA approved polymers like Poly(lactic-co-glycolic acid) (PLGA) and Polycaprolactone (PCL), will only potentiate this issue. Considering that drug loading is one of the key defining characteristics, in this study we attempted to examine whether the nanoparticle (NP) core composed of two hydrophobic polymers will provide increased drug loading for 7-Ethyl-10-hydroxy-camptothecin (SN-38), relative to NPs prepared using individual polymers. D-optimal design was applied to optimize PLGA/PCL ratio in the polymer blend and the mode of addition of the amphiphilic copolymer Lutrol®F127 in order to maximize SN-38 loading and obtain NPs with acceptable size for passive tumor targeting. Drug/polymer and polymer/polymer interaction analysis pointed to high degree of compatibility and miscibility among both hydrophobic polymers, providing core configuration with higher drug loading capacity. Toxicity studies outlined the biocompatibility of the blank NPs. Increased in vitro efficacy of drug-loaded NPs compared to the free drug was confirmed by growth inhibition studies using SW-480 cell line. Additionally, the optimized NP formulation showed very promising blood circulation profile with elimination half-time of 7.4 h.

PEO-PPO-PEO/Poly(DL-lactide-co-caprolactone) Nanoparticles as Carriers for SN-38: Design, Optimization and Nano-Bio Interface Interactions.

Encapsulation of extremely hydrophobic substances such as SN-38 into nanoparticles, is a promising approach to solve the solubility issue and enable drug administration. Moreover, nanocarriers' tumor homing behavior, targeted and controlled release at the site of action will optimize therapeutic potency and decrease toxicity of the incorporated drug substance. However, the enormous drug hydrophobicity might limit the capacity for encapsulation as the premature drug precipitation will contribute to fast free drug crystal growth, low drug incorporation and huge waste of the active material. In this article we defined the optimal region for manufacturing of SN-38 loaded PEO-PPO-PEO/P(DL)LCL nanoparticles (NPs) with high efficacy of encapsulation, suitable particle size and different surface properties, using D-optimal design and nanoprecipitation as production method. Further we made an approach to investigate the interactions with macromolecules at the nano-bio interface which are predetermined by the physico-chemical and surface properties of the NPs, and are important determinants for the biological identity of the nanoparticles, the potential for evasion of the physiological barriers and the efficacy of localization at the site of action. Here we present in depth analysis of the behavior of two types of nanoparticles with different surface properties through structured protein interaction and bioreactivity experiments in order to presuppose NP performance and toxicological profile in biological environment.