Tailoring the structure and self-activated photoluminescence of carbonated amorphous calcium phosphate nanoparticles for bioimaging applications

Self-activated luminescent calcium phosphate (CaP) nanoparticles, including hydroxyapatite (HA) and amorphous calcium phosphate (ACP), are promising for bioimaging and theragnostic applications in nanomedicine, eliminating the need for activator ions or fluorophores. In this study, we developed lumi...

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Bibliographic Details
Published in:Journal of materials chemistry. B, Materials for biology and medicine Materials for biology and medicine, 2024-05, Vol.12 (2), p.4945-4961
Main Authors: Machado, Thales R, Zanardo, Carlos E, Vilela, Raquel R.C, Miranda, Renata R, Moreno, Natália S, Leite, Celisnolia M, Longo, Elson, Zucolotto, Valtencir
Format: Article
Language:English
Subjects:
Activated carbon
Biocompatibility
Calcium carbonate
Calcium phosphates
Calcium Phosphates - chemistry
Carbonates - chemistry
Carbonation
Cell culture
Cell Survival - drug effects
Chemical compounds
Citric acid
Confocal microscopy
Emission
Emissions
Excitation
Fluorophores
Heat treatment
Humans
Hydroxyapatite
Internalization
Luminescence
Medical imaging
Nanoparticles
Nanoparticles - chemistry
Nanotechnology
Optical Imaging
Particle Size
Photoluminescence
Photons
Scanning microscopy
Stability
Wavelengths
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Summary:Self-activated luminescent calcium phosphate (CaP) nanoparticles, including hydroxyapatite (HA) and amorphous calcium phosphate (ACP), are promising for bioimaging and theragnostic applications in nanomedicine, eliminating the need for activator ions or fluorophores. In this study, we developed luminescent and stable citrate-functionalized carbonated ACP nanoparticles for bioimaging purposes. Our findings revealed that both the CO 3 2− content and the posterior heating step at 400 °C significantly influenced the composition and the structural ordering of the chemically precipitated ACP nanoparticles, impacting the intensity, broadness, and position of the defect-related photoluminescence (PL) emission band. The heat-treated samples also exhibited excitation-dependent PL under excitation wavelengths typically used in bioimaging ( λ exc = 405, 488, 561, and 640 nm). Citrate functionalization improved the PL intensity of the nanoparticles by inhibiting non-radiative deactivation mechanisms in solution. Additionally, it resulted in an increased colloidal stability and reduced aggregation, high stability of the metastable amorphous phase and the PL emission for at least 96 h in water and supplemented culture medium. MTT assay of HepaRG cells, incubated for 24 and 48 h with the nanoparticles in concentrations ranging from 10 to 320 μg mL −1 , evidenced their high biocompatibility. Internalization studies using the nanoparticles self-activated luminescence showed that cellular uptake of the nanoparticles is both time (4-24 h) and concentration (160-320 μg mL −1 ) dependent. Experiments using confocal laser scanning microscopy allowed the successful imaging of the nanoparticles inside cells via their intrinsic PL after 4 h of incubation. Our results highlight the potential use of citrate-functionalized carbonated ACP nanoparticles for use in internalization assays and bioimaging procedures. The optimization of carbonates concentration, a posterior heat treatment step, and citrate functionalization yield stable self-activated luminescent amorphous calcium phosphate nanoparticles for bioimaging applications.
ISSN:2050-750X
2050-7518
DOI:10.1039/d3tb02915h