Influence of surface composition on the colloidal stability of ultra-small detonation nanodiamonds in biological media

Abstract

Fluorescent nanodiamonds (NDs) are strong contenders as bio-labels for life science imaging, diagnostics and therapeutics. Ultimately, for their use in biomedical applications, their size should ideally be less than 10 nm. Yet, even more critical for their specificity and efficient uptake in cellular systems, is their resilience to aggregation, which is dictated by their colloidal stability in complex, physiological environments. To this end, we characterize ultrasmall detonation NDs (~5 nm) by examining their surface chemical profiles and stability in solutions of varying ionic strength and pH. Using dynamic light scattering measurements, we demonstrate that ultra-small ND particles with chemically homogeneous and negatively charged surface profiles are more stable than positive particles under a broad range of simulated biological environments. We show that the colloidal stability of both positive and negative ultra-small NDs is improved by functionalization with bovine serum albumin. Based on these analyses, we propose and describe strategies for enhancing the overall colloidal stability of ultra-small NDs and their resilience to aggregation. Our findings provide a practical framework towards the reduction in size of the bio-conjugates employed to probe complex biological systems, and the advancement of bio-imaging techniques with minimal perturbation of the molecular trafficking in cellular and organelle systems.

Tailored nanodiamonds for hyperpolarized C13 MRI

“…Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was performed using a Thermo Scientific Nicolet iS10 spectrometer to characterize the functional groups on the LMSY nanodiamond surface. ATR-FTIR showed an increase in the characteristic 1780 cm −1 carbonyl peak associated with carboxylic acid groups, confirming oxidation of the nanodiamond surface [51].…”

A simple and soft chemical deaggregation method producing single-digit detonation nanodiamonds

“…As a result, the negatively-charged DNDs showed good colloidal stability over a wide range of pH values, covering both, alkaline and acidic conditions, in comparison to BASD DNDs (positively-charged DNDs) as reported before. 47 Moreover, negatively-charged DNDs were shown to have a stronger aggregation resistance at higher ionic strength in comparison to positively-charged DNDs. 47 Finally, we observed that the freeze-dried air-oxidized DNDs after boiling acid were redispersed in water down to a singledigit size of 7.1 ± 0.3 nm (Figure 5(b)), sharing similar properties as SAUD DNDs, as well as horn sonication oxidized DNDs, but a remarkable difference to freeze-dried BASD DNDs, which cannot be redispersed in the same way and do show aggregation with two peaks of particle sizes 24.6 ± 2.6 nm and 619.4 ± 2.1 nm (Figure 5(b)).…”

Nanodiamonds as Possible Tools for Improved Management of Bladder Cancer and Bacterial Cystitis

“…These two approaches lead to hydroxylated and carboxylated NDs that are hydrophilic and have high dispersibility in aqueous solution, with typical zeta potentials of −30 to −50 mV and about +40 mV, respectively [ 21 ]. A recent publication on negatively charged NDs has shown that, compared to positively charged NDs of the same size, they are more resistant to aggregation and exhibit high colloidal stability in a wide range of pH values and salt concentrations [ 33 ]. Negatively charged NDs have a more homogeneous surface and their functional groups are mostly carboxy units.…”