Labeling the Structural Integrity of Nanoparticles for Advanced In Situ Tracking in Bionanotechnology

Abstract

Observing structural integrity of nanoparticles is essential in bionanotechnology but not always straightforward to measure in situ and in real-time. Fluorescent labels used for tracking intrinsically nonfluorescent nanomaterials generally do not allow simultaneous observation of integrity. Consequently, structural changes like degradation and disassembly cannot easily be followed in situ using fluorescence signals. We show that thioflavin T (ThT), a fluorophore and molecular rotor known to tag specific fibril structures in amyloids, can "label" the structural integrity of widely used and intrinsically nonfluorescent, silica nanoparticles (SiNPs). Entrapment of ThT in SiNPs controls the fluorohphore's relaxation pathway and leads to a red-shifted fluorescence spectrum providing real time information on SiNP integrity. The dynamic change of ThT fluorescence during degradation of doped SiNPs is found much higher than that of common labels fluorescein and rhodamine. Degradation kinetics of core-shell structures recorded by ThT fluorescence and light scattering prove the capability to clearly distinguish structural features during SiNPs degradation and allow obtaining degradation kinetics in vitro, in biological media, in serum, and in cells. The effect is transferable to different types of materials, here shown for ThT incorporated SiNPs with tightly tailorable sizes (9-100 nm), poly(lactic-co-glycolic acid) (PLGA) nanoparticles, poly(9-vinylcarbazole) (PVK) nanoparticles, and iron-doped-SiNPs (FeSiNPs). We thus suggest molecular rotors such as ThT as additional labels to effectively and easily sense nanoparticle structural status in situ and to enhance understanding and development of programmed nanoparticle disassembly in bionanotechnology.

Artificial Lysosomal Platform to Study Nanoparticle Long-term Stability

“…Artificial lysosomal fluid (ALF) has emerged as af luid that simulates the environment of lysosomes in terms of pH, ionic strength, multiple components (presence of various inorganic and organic salts) and even the crowdedness of the givenenvironment (increase of viscosity). ALF contains 13 inorganic and organic components and has been previously used to evaluate the bioavailability of metals, [9] silica NP degradation [10] and functionalized gold NP aggregation. [6] ALF has previously been proventobeamore relevant environment for the prediction of intracellular NP behaviour compared to asimple buffer at pH 4.5.…”

Magneto‐Thermal Metrics Can Mirror the Long‐Term Intracellular Fate of Magneto‐Plasmonic Nanohybrids and Reveal the Remarkable Shielding Effect of Gold

“…The ability to detect and quantify the transformations of nanohybrids inside their target cells over the long‐term (at least a month) is essential for all future theranostic applications; yet the study of inorganic nanohybrids biotransformations is still uncharted territory. To date, studies examining the long‐term biological fate of inorganic nanomaterials have evaluated usually biodegradation in aqueous media mimicking biological fluids (cell culture media, artificial lysosome‐like fluid, serum, plasma) or directly in vivo after intravenous injection . The first scenario allows reliable quantitative measurements but is far removed from the cellular environment, while the second integrates biological complexity but precludes quantitative measurements at the (sub)cellular scale.…”

“…Recent approaches have pioneered new and sensitive ways of monitoring intracellular nanoparticles integrity status in vitro or in vivo. They are based on labeling nanoparticles core or shell with fluorescent dyes, radionuclide labels, or smart molecular rotors ultrasensitive to their microenvironment . Supplementing this young nanobiodegradation toolbox with methods allowing the tracking of an inorganic core and/or shell in situ, and on the long‐term, is still needed.…”

Six open questions about the migration of engineered nano-objects from polymer-based food-contact materials: a review

“…The use of fluorescently (Meder et al 2016) or isotopically labelled ENOs (Merrifield & Lead 2016), as in the fields of bionanotechnology and nanotoxicology, could help to study and identify dissolution and agglomeration processes. The behaviour of the relevant ions (e.g., Ag, Zn or Cu) in food and food simulants needs to be studied to evaluate whether or not secondary formation of ENOs after migration of ions is possible.…”