OBJECTIVE: Calcifying nanoparticles (CNPs), referred to as nanobacteria (NB), are recognized to be associated with ectopic calcification. This study aims to isolate and culture CNPs from the dental plaque of patients with periodontal disease and investigate their possible role in unravelling the aetiology of periodontal disease.
METHODS: Supragingival and subgingival plaques were sampled from 30 periodontitis patients for CNPs isolation and culture. Alkaline phosphatase (ALP) content changes were tracked over time. Positive samples underwent thorough morphological identification via hematoxylin and eosin (HE) staining, Alizarin red S (ARS), and transmission electron microscopy (TEM). The chemical composition of CNPs analysis involved calcium (Ca) and phosphorus (P) content determination, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD).
RESULTS: The subgingival plaque dental group exhibited a higher CNPs isolation rate at 36.67% (11/30) compared to the supragingival dental plaque group at 66.67% (20/30). ALP activity varied among the positive, negative and control groups. Morphological observation characterized the CNPs as round, oval, and ellipsoid particles with Ca deposits. Chemical analysis revealed the Ca/P ratio was 0.6753. Hydroxyl, methyl, carbonate, phosphate, hydrogen phosphate, and dihydrogen phosphate were detected by FTIR; the main chemical components detected by XRD were hydroxyapatite and tricalcium phosphate.
CONCLUSIONS: CNPs were found in periodontitis-related dental plaque and exhibited the potential to develop calcified structures resembling dental calculus. However, the potential involvement of ALP in CNPs formation requires deeper exploration, as does the precise nature of its role and the interrelation with periodontitis demand a further comprehensive investigation.

OBJECTIVE: In patients with renal failure or chronic inflammation, the accumulation of fetuin-A-containing calciprotein particles (CPP) in the extracellular fluid has been implicated in driving inflammatory pathways and extraosseous mineral deposition. We aimed to discover whether CPP are present in the peritoneal dialysis fluid effluent (PDF) of stable peritoneal dialysis (PD) patients, and if so, how these particles might be formed.
METHODS: Serum and PDF were sampled from 20 stable PD patients. CPP were quantified by the reduction in fetuin-A concentration after high speed centrifugation. 8-iso-PGF2α in PDF was measured as a marker of oxidative stress. Fetuin-A and phosphate were added to commercially available dialysis fluids to assess their ability to support CPP formation ex vivo.
RESULTS: We report that the major protein component of these mineral-containing nanoparticles, fetuin-A, is relatively abundant in PDF and that CPP were present in the PDF of 17/20 PD patients. PDF CPP levels were strongly correlated with 8-iso-PGF2α concentrations. In vitro experiments suggested that commonly used peritoneal dialysate fluids, irrespective of composition, could not sustain appreciable de novo CPP formation ex vivo.
CONCLUSIONS: Fetuin-A is either actively transported or locally produced by the peritoneal membrane in PD patients. The association between fetuin-A-containing CPP and markers of oxidative stress warrants further mechanistic studies.