Abstract
Glycosylation is arguably the most important functional post-translational modification in brain cells and abnormal cell surface glycan expression has been associated with neurological diseases and brain cancers. In this study we developed a novel method for uptake of fluorescent nanodiamonds (FND), carbon-based nanoparticles with low toxicity and easily modifiable surfaces, into brain cell subtypes by targeting their glycan receptors with carbohydrate-binding lectins. Lectins facilitated uptake of 120 nm FND with nitrogen-vacancy centers in three types of brain cells – U87-MG astrocytes, PC12 neurons and BV-2 microglia cells. The nanodiamond/lectin complexes used in this study target glycans that have been described to be altered in brain diseases including sialic acid glycans via wheat (Triticum aestivum) germ agglutinin (WGA), high mannose glycans via tomato (Lycopersicon esculentum) lectin (TL) and core fucosylated glycans via Aleuria aurantia lectin (AAL). The lectin conjugated nanodiamonds were taken up differently by the various brain cell types with fucose binding AAL/FNDs taken up preferentially by glioblastoma phenotype astrocyte cells (U87-MG), sialic acid binding WGA/FNDs by neuronal phenotype cells (PC12) and high mannose binding TL/FNDs by microglial cells (BV-2). With increasing recognition of glycans having a role in many diseases, the lectin bioconjugated nanodiamonds developed here are well suited for further investigation into theranostic applications.
Highlights
Fluorescent nanodiamonds (FNDs) are highly biocompatible in vitro and in vivo carbon based nanocarrier tracking agents suitable for drug delivery[1,2] including for anti-cancer therapeutics.[3,4,5,6] They have excellent photostability and show high optical contrast in uorescence microscopy images[1,7,8,9] and the highest cellular uptake among members of the nanocarbon family,[9,10] making them suitable for bioimaging and diagnostics
The uptake of the three types of lectin-conjugated nanodiamonds was evaluated in neuronal cells, microglia cells and astrocyte cells by laser scanning confocal uorescence microscopy and we report on cellular health, active uptake and cell viability of the exposed cell types
Before the bioconjugation of FNDs to lectins (Fig. 1A), raw FNDs were characterized by transmission electron microscopy (TEM), showing a normal size distribution ranging from 25 nm to 225 nm size
Summary
Fluorescent nanodiamonds (FNDs) are highly biocompatible in vitro and in vivo carbon based nanocarrier tracking agents suitable for drug delivery[1,2] including for anti-cancer therapeutics.[3,4,5,6] They have excellent photostability and show high optical contrast in uorescence microscopy images[1,7,8,9] and the highest cellular uptake among members of the nanocarbon family,[9,10] making them suitable for bioimaging and diagnostics. Edu.au; Tel: +61 2 9850 8269 bARC Centre of Excellence for Nanoscale BioPhotonics, School of Science, RMIT University, Melbourne, VIC 3001, Australia cQuantum Beam Science Research Directorate and The Institute for Quantum Life Science, National Institutes for Quantum Science and Technology, Takasaki, Gunma 3701292, Japan dInstitute for Glycomics, Griffith University, Southport, QLD, 4222, Australia † Electronic supplementary information (ESI) available. 500 nm.[12,13] The uorescent diamonds contain defects in their crystal lattice that are key contributors to their luminescence and photostability by trapping photoelectrons and energy in the center of the lattice surrounded by carbons following photoemission.[14,15] Nitrogen-vacancy (NV) center nanodiamonds are most commonly used for research purposes as they show broad uorescence in the spectral range between 600 nm and 800 nm in the rst near-infrared biological window.[16]
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