Metrics details. Aluminum oxyhydroxide alum is a crystalline compound widely used as an immunologic adjuvant of vaccines. Concerns linked to alum particles have emerged following recognition of their causative role in the so-called macrophagic myofasciitis MMF lesion in patients with myalgic encephalomyelitis, revealing an unexpectedly long-lasting biopersistence of alum within immune cells and a fundamental misconception of its biodisposition.
Evidence that aluminum-coated particles phagocytozed in the injected muscle and its draining lymph nodes can disseminate within phagocytes throughout the body and slowly accumulate in the brain further suggested that alum safety should be evaluated in the long term. However, lack of specific staining makes difficult the assessment of low quantities of bona fide alum adjuvant particles in tissues. As the NV center does not bleach, it allows the microspectrometric detection of mfNDs at very low levels and in the long-term.
We thus developed fluorescent nanodiamonds functionalized by hyperbranched polyglycerol mfNDs allowing good coupling and stability of alum:mfNDs AluDia complexes. Specificities of AluDia complexes were comparable to the whole reference vaccine anti-hepatitis B vaccine in terms of particle size and zeta potential.
In vivo , AluDia injection was followed by prompt phagocytosis and AluDia particles remained easily detectable by the specific signal of the fND particles in the injected muscle, draining lymph nodes, spleen, liver and brain. Expectedly, AluDia elicited autophagy, and allowed highly specific detection of small amounts of alum in autophagosomes.
The fluorescent nanodiamond technology is able to overcome the limitations of previously used organic fluorophores, thus appearing as a choice methodology for studying distribution, persistence and long-term neurotoxicity of alum adjuvants and beyond of other types of nanoparticles. Peer Review reports. The understanding of how the body handles small particles in the long-term, especially those which interact with the immune system, is a major objective of recent research [ 1 ].
