Long-Term Monitoring of the Physicochemical Properties of Silica-Based Nanoparticles on the Rate of Endocytosis and Exocytosis and Consequences of Cell Division

Abstract

Nanomaterials are diverse in size, shape, and charge and these differences likely alter their physicochemical properties in biological systems. We have investigated how these properties alter the initial and long-term dynamics of endocytosis, cell viability, cell division, exocytosis, and interaction with a collagen extracellular matrix using silica-based fluorescent nanoparticles and the murine pre-osteoblast cell line, MC3T3-E1. Three surface modified nanoparticles were analyzed: positively charged (PTMA), negatively charged (OH), and neutrally charged polyethylene glycol (PEG). Positively charged PTMA-modified nanoparticles demonstrated the most rapid uptake, within 2 hours, while PEG modified and negatively charged OH nanoparticles demonstrated slower uptake. Cell viability was >80% irrespective of nanoparticle surface charge suggesting a general lack of toxicity. Long-term monitoring of fluorescent intensity revealed that nanoparticles were passed to daughter cells during mitotic cell division with a corresponding decrease in fluorescent intensity. These data suggest that irrespective of surface charge silica nanoparticles have the potential to internalize into pre-osteoblasts, albeit with different kinetics. Furthermore, long lived nanoparticles have the potential to be transferred to daughter cells during mitosis and can be maintained for weeks intracellularly or within a collagen matrix without toxicity and limited exocytosis.

Keywords:

• Cell division
• Endocytosis
• Extracellular matrix
• Fluorescence
• Osteoblast
• Silica-based nanoparticles

Acknowledgment

This research was supported by Nano R&D Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2009-0082736). S.-W. Ha is grateful for the award of a BK21 fellowship. G. R. Beck Jr., M. N. Weitzmann, and C. E. Camalier are supported in part by a grant from NIH/NIAMS (AR056090), Georgia Research alliance grant (GRA.VL12.C2 A/B), and a Center for Pediatric NanoMedicine grant (Emory University). M. N. Weitzmann is also supported by a grant from the Biomedical Laboratory Research & Development Service of the VA Office of Research and Development (5I01BX000105). G.R. Beck is also supported by a grant from the NIH (CA136716).