Uptake and intracellular accumulation of diamond nanoparticles - a metabolic and cytotoxic study.

Antonín Brož,Štěpán Potocký,Lucie Bačáková,Pavla Štenclová,Alexander Kromka

doi:10.3762/bjnano.8.165

Abstract

Diamond nanoparticles, known as nanodiamonds (NDs), possess several medically significant properties. Having a tailorable and easily accessible surface gives them great potential for use in sensing and imaging applications and as a component of cell growth scaffolds. In this work we investigate in vitro interactions of human osteoblast-like SAOS-2 cells with four different groups of NDs, namely high-pressure high-temperature (HPHT) NDs (diameter 18–210 nm, oxygen-terminated), photoluminescent HPHT NDs (diameter 40 nm, oxygen-terminated), detonation NDs (diameter 5 nm, H-terminated), and the same detonation NDs further oxidized by annealing at 450 °C. The influence of the NDs on cell viability and cell count was measured by the mitochondrial metabolic activity test and by counting cells with stained nuclei. The interaction of NDs with cells was monitored by phase contrast live-cell imaging in real time. For both types of oxygen-terminated HPHT NDs, the cell viability and the cell number remained almost the same for concentrations up to 100 µg/mL within the whole range of ND diameters tested. The uptake of hydrogen-terminated detonation NDs caused the viability and the cell number to decrease by 80–85%. The oxidation of the NDs hindered the decrease, but on day 7, a further decrease was observed. While the O-terminated NDs showed mechanical obstruction of cells by agglomerates preventing cell adhesion, migration and division, the H-terminated detonation NDs exhibited rapid penetration into the cells from the beginning of the cultivation period, and also rapid cell congestion and a rapid reduction in viability. These findings are discussed with reference to relevant properties of NDs such as surface chemical bonds, zeta potential and nanoparticle types.

Highlights

Carbon-based materials in the form of nanostructures are showing great promise as engineering and biomedical materials [1]
We focus on cytotoxicity studies of NDs as a function of their synthesis route (DNDs versus high-pressure high-temperature (HPHT) NDs), their concentration in the medium (from 10 to 1000 mg/mL, 3 to Figure 2 shows the results of a cell mitochondrial activity test and counting of the cell nuclei after 7 days of cultivation for three different concentrations of 10, 100 and 1000 μg/mL (3, 30, 300 μg/cm2) as a function of HPHT ND particle size
A concentration-dependent toxic effect of HPHT NDs was revealed after 7 days of cultivation, where the viability of the cells cultivated in the 1000 μg/mL (300 μg/cm2) suspension reduced by 25% when evaluated by metabolic activity test (MTS) and by 35% when evaluated by the cell counting experiment

Summary

Introduction

Carbon-based materials in the form of nanostructures are showing great promise as engineering and biomedical materials [1]. Nanodiamond-based drug delivery has been mainly developed for advanced tumour therapies and for localized drug delivery [3,14] Due to their stable and controllable photoluminescence, NDs are highly promising for advanced photonic and bioimaging techniques [15,16] and for nanoscale sensing [17,18]. Oxidation in air at elevated temperature is a good method for effective sp carbon removal [26,27], particle size reduction [22] and surface oxidation (i.e., the surface is covered by defined starting functional groups). The results were evaluated on the basis of particle size, surface potential, surface functional groups, and the concentration of the ND suspension

Results and Discussion

Conclusion

Evaluation of cell viability