Abstract B46: Surface chemistry governs cellular tropism of nanoparticles in the brain

Abstract

Purpose: Nanoparticles (NPs) carry important promises for the treatment of neurological diseases, such as glioblastoma multiform (GBM) and Parkinson's disease. Several methods have been developed to achieve higher NP concentrations in the brain, including local infusions using convection enhanced delivery (CED), focused ultrasound, and the use of surface targeting moieties specifically designed to increase the passage across the blood brain barrier (BBB). However, even when sufficient NP amounts are delivered to the targeted region, a better understanding of the interactions between the particles and the brain parenchyma will be necessary to reach clinical efficacy. This is particularly true for polymeric NPs, which behavior can be dramatically influenced by multiple factors such as their size and their surface properties. Here, we investigated the cellular fate of PLA-based nanoparticles of similar size, but bearing different surface modifications, following CED in the healthy brain and the tumor bearing brain. Methods: Four PLA-based NP formulations with different surface modifications (PLA, PLA-PEG, PLA-HPG and PLA-HPG-CHO) and similar size were obtained by emulsion or nanoprecipitation. CED of each formulation was performed in healthy or tumor bearing brain, and comparable volumes of distribution were obtained. 4 h and 24 h after infusion, brains were harvested and processed for flow cytometry analysis and immunohistochemical staining, to quantify particle internalization by neurons, astrocytes, microglia and tumor cells, when applicable. In vitro uptake studies were performed using relevant cell lines for neurons (N27 cells), astrocytes (TNC1), microglia (BV2) and tumors (RG2). Rate of association kinetics of different particles with these cells were derived from an uptake study and then correlated with in vivo internalization results. Finally, to evaluate how different NPs surface modifications and their different internalization patterns can influence survival benefits, the different particles were loaded with epothilone B (EB) and infused into rats bearing RG2 tumors via CED. Results: We observed that in the healthy brain, stealth NPs distributed evenly between neurons, astrocytes and microglia, while exhibiting the highest specificity towards tumor cells in the tumor bearing brain. Overall, the functionalization of PLA NPs with aldehyde groups allowed for an increased uptake by all cell types, in both healthy and tumor bearing brain. These NPs also presented an increased relative uptake by microglia cells in both environments, compared to stealth particles, suggesting the induction of an immune response. Rates of association of NPs in vitro varied significantly between particle types. We were then able to correlate the in vivo uptake of each particle and cell type with in vitro particle association rates with neurons, astrocytes and microglia in culture, demonstrating the possibility of predicting in vivo uptake using in vitro association rates. Finally, comparison of particles in a survival efficacy showed significant differences, highlighting the importance of uptake of NPs. Conclusions: This study demonstrates for the first time that NP surface modifications significantly influence the cellular tropism of NPs in the brain in vivo, and that in vitro association rates can be used to anticipate the different internalization patterns. These differences open the possibility of tuning surface properties to optimize cellular delivery and therapeutic outcome. Acknowledgements: This work is supported by a NIH/NCI R01 grant (#5R01CA149128-04). Citation Format: Eric Song, Alice Gaudin, Amanda R. King, Youngeun Seo, Paul Won, Heewon Suh, Yang Deng, Jiajia Cui, Gregory Tietjen, W Mark Saltzman. Surface chemistry governs cellular tropism of nanoparticles in the brain. [abstract]. In: Proceedings of the AACR Special Conference on Engineering and Physical Sciences in Oncology; 2016 Jun 25-28; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2017;77(2 Suppl):Abstract nr B46.

Anti-seed PNAs targeting multiple oncomiRs for brain tumor therapy

“…S5B). These findings confirm the preferential cellular uptake of sgPNA/BNP into glioma cells, which is consistent with our previous studies (26,52).…”

“…NPs formed from PLA-HPG-CHO are bioadhesive nanoparticles, or BNPs (48)(49)(50)(51). We have shown that-compared with several other NPs of similar composition-these BNPs lead to the highest levels of uptake into intracranial tumor cells after CED (52) and they can be loaded with PNAs, which are slowly released after CED in the brain (53). In this work, we loaded the PLA-HPG-CHO BNPs with two sgPNAs-one binding to miR-10b and another binding to miR-21-to test the hypothesis that simultaneous delivery of two anti-miRs in glioma cells can regulate unique molecular pathways leading to improved survival.…”

Local DNA Repair Inhibition for Sustained Radiosensitization of High-Grade Gliomas

“…The period of rapid elimination of VE822 (half-life of 2 hr, more rapid than the clearance rate of free drug) is due to elimination of NPs containing VE822, whereas the sustained levels are the result of a competition between slow VE822 release from the remaining intracellular NPs, elimination of free VE822, and slow elimination/degradation of the remaining NPs. We still have work to do in determining the relative contributions of these multiple routes for elimination in the tumor microenvironment, but recent experiments suggest that some of these mechanisms can be manipulated by changing properties of the NP, such as surface chemistry (59–61). Still, even with our present formulation, NP-VE822 was able to maintain intracranial drug levels above the IC50 of VE822 (0.125uM) for at least 10 d after administration.…”

“…In this context, we selected a molecule with minimal effect on NHEJ in an effort to maximize the therapeutic ratio. Additionally, the passive targeting of NP-formulations that allows enhanced uptake in mitotically active cells such as tumor cells seems to supplement this selective tumor targeting and even further widen the gap of relative toxicity between healthy and tumor cells (59). …”

Improved threshold selection for the determination of volume of distribution of nanoparticles administered by convection-enhanced delivery

“…PLA-HPG NPs loaded with the DiA dye (0.2% w/w) at a final concentration of 100 mg/mL in PLA-HPG were prepared by the emulsion-evaporation technique as previously described [17]. Brain penetrating PLGA NPs loaded with Nile Red (0.2% w/w) at a final concentration of 100 mg/mL in PLGA were prepared by the emulsion-evaporation technique followed by centrifugation steps to recover small particles, as previously described [18].…”