Putative nanobacteria represent physiological remnants and culture by-products of normal calcium homeostasis

A preliminary study on calcifying nanoparticles in dental plaque: Isolation, characterization, and potential mineralization mechanism

OBJECTIVES

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.

MATERIAL AND 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.

CONCLUSION

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.

Tissue chaperoning—the expanded functions of fetuin-A beyond inhibition of systemic calcification

Traditionally, fetuin-A embodies the prototype anti-calcification protein in the blood, preventing cardiovascular calcification. Low serum fetuin-A is generally associated with mineralization dysbalance and enhanced mortality in end stage renal disease. Recent evidence indicates that fetuin-A is a crucial factor moderating tissue inflammation and fibrosis, as well as a systemic indicator of acute inflammatory disease. Here, the expanded function of fetuin-A is discussed in the context of mineralization and inflammation biology. Unbalanced depletion of fetuin-A in this context may be the critical event, triggering a vicious cycle of progressive calcification, inflammation, and tissue injury. Hence, we designate fetuin-A as tissue chaperone and propose the potential use of exogenous fetuin-A as prophylactic agent or emergency treatment in conditions that are associated with acute depletion of endogenous protein.

Physical attributes of salivary calcium particles and their interaction with gingival epithelium

Background

The formation of dental plaque and its involvement in the pathogenesis of periodontitis is a topic of intense interest given the high prevalence of periodontitis in humans. Even though calcium-based particles play an active role in both dental plaque formation and periodontitis, few publications describe the physical-chemical properties of these particles.

Methods

Saliva samples were collected from healthy volunteers. From these samples, saliva-derived particles were isolated and stained for calcium using calcein or Fluo-4. The salivary particles were also subjected to characterization by flow cytometry and immunoblotting. Internalization of calcein-labeled salivary particles by gingival epithelial cells was visualized by confocal microscopy.

Results

We found that calcium-based salivary particles from healthy volunteers varied greatly in size but were enriched in particles of sizes at or greater than 1.5 μm. Immunoblotting analysis of the salivary particles identified several proteins including albumin, fetuin-A, and statherin, which have been found in calcium phosphate particles from other tissues or are known to modulate calcium homeostasis in saliva. In addition, calcium particles were internalized by both gingival epithelial cells and monocyte-derived macrophages.

Conclusion

Salivary calcium particles were enriched in the micrometer range, internalized by gingival epithelial cells, and contain albumin, fetuin-A and statherin, regulators of particle formation. These characteristics of the calcium-based salivary particles and their biological activities provide a basis for further studies to understand the molecular basis for pathogenesis of periodontitis.

Calciprotein particles: mineral behaving badly?

PURPOSE OF REVIEW

Calciprotein particles (CPP) are formed in supersaturated solutions of calcium, phosphate and the mineral-binding protein fetuin-A. CPP have garnered considerable interest as potential mediators of mineral stress, but little consideration has been given to their origin, clearance and role in metabolism.

RECENT FINDINGS

CPP are made whilst buffering the mineral absorbed from the intestine after a meal or during remodelling of bone matrix. The postprandial rise in circulating CPP rise may be sensed by osteoblasts/osteocytes in bone, stimulating the secretion of the master phosphatonin fibroblast growth factor 23. Amorphous calcium phosphate-containing CPP are rapidly cleared by endothelial cells in the liver whereas crystalline apatite-containing CPP are filtered by phagocytic cells of the reticuloendothelial system. Impaired excretory function in kidney disease may lead to accumulation of CPP and its precursors with possible pathological sequalae. Inability to stabilize CPP in fetuin-A-deficiency states can result in intraluminal precipitation and inflammatory cascades if other mineralisation regulatory networks are compromised.

SUMMARY

CPP allow efficient transport and clearance of bulk calcium phosphate as colloids without risk of precipitation. As circulating factors, CPP may couple dietary mineral exposure with endocrine control of mineral metabolism in bone, signalling the need to dispose of excess phosphate from the body.

Mud in the blood: the role of protein-mineral complexes and extracellular vesicles in biomineralisation and calcification

Protein-mineral interaction is known to regulate biomineral stability and morphology. We hypothesise that fluid phases produce highly dynamic protein-mineral complexes involved in physiology and pathology of biomineralisation. Here, we specifically focus on calciprotein particles, complexes of vertebrate mineral-binding proteins and calcium phosphate present in the systemic circulation and abundant in extracellular fluids - hence the designation of the ensuing protein-mineral complexes as "mud in the blood". These complexes exist amongst other extracellular particles that we collectively refer to as "the particle zoo".

Ectopic calcification and formation of mineralo-organic particles in arteries of diabetic subjects

Vascular calcification occurs in various diseases including atherosclerosis, chronic kidney disease and type 2 diabetes but the mechanism underlying mineral deposition remains incompletely understood. Here we examined lower limb arteries of type 2 diabetes subjects for the presence of ectopic calcification and mineral particles using histology, electron microscopy and spectroscopy analyses. While arteries of healthy controls showed no calcification following von Kossa staining, arteries from 83% of diabetic individuals examined (19/23) revealed microscopic mineral deposits, mainly within the tunica media. Mineralo-organic particles containing calcium phosphate and proteins such as albumin, fetuin-A and apolipoprotein-A1 were detected in calcified arteries. Ectopic calcification and mineralo-organic particles were observed in a majority of diabetic patients and predominantly in arteries showing hyperplasia. While a low number of subjects was examined and information about disease severity and patient characteristics is lacking, these calcifications and mineralo-organic particles may represent signs of tissue dysfunction.

Mineral self-organization on a lifeless planet

It has been experimentally demonstrated that, under alkaline conditions, silica is able to induce the formation of mineral self-assembled inorganic-inorganic composite materials similar in morphology, texture and nanostructure to the hybrid biomineral structures that, millions of years later, life was able to self-organize. These mineral self-organized structures (MISOS) have been also shown to work as effective catalysts for prebiotic chemical reactions and to easily create compartmentalization within the solutions where they form. We reason that, during the very earliest history of this planet, there was a geochemical scenario that inevitably led to the existence of a large-scale factory of simple and complex organic compounds, many of which were relevant to prebiotic chemistry. The factory was built on a silica-rich high-pH ocean and powered by two main factors: a) a quasi-infinite source of simple carbon molecules synthesized abiotically from reactions associated with serpentinization, or transported from meteorites and produced from their impact on that alkaline ocean, and b) the formation of self-organized silica-metal mineral composites that catalyze the condensation of simple molecules in a methane-rich reduced atmosphere. We discuss the plausibility of this geochemical scenario, review the details of the formation of MISOS and its catalytic properties and the transition towards a slightly alkaline to neutral ocean.

Shape-dependent toxicity and mineralization of hydroxyapatite nanoparticles in A7R5 aortic smooth muscle cells

Vascular smooth muscle cell damage is a key step in inducing vascular calcification that yields hydroxyapatite (HAP) as a major product. The effect of the shape of HAP on the damage to vascular smooth muscle cells has yet to be investigated. In this study, we compared the differences in toxicity of four various morphological nano-HAP crystals, namely, H-Rod, H-Needle, H-Sphere, and H-Plate, in rat aortic smooth muscle cells (A7R5). The sizes of these crystals were 39 nm × 115 nm, 41 nm ×189 nm, 56 nm × 56 nm, and 91 nm × 192 nm, respectively. Results showed that all HAPs decreased cell viability, disorganized cell morphology, disrupted cell membranes, increased intracellular reactive oxygen species concentration, decreased mitochondrial membrane potential, decreased lysosome integrity, increased alkaline phosphatase activity, and increased intracellular calcium concentration, resulting in cell necrosis. The cytotoxicity of the four kinds of HAP was ranked as follows: H-Plate > H-Sphere > H-Needle > H-Rod. The cytotoxicity of each crystal was positively correlated with the following factors: large specific surface area, high electrical conductivity and low surface charge. HAP accelerated calcium deposits on the A7R5 cell surface and induced the expression of osteogenic proteins, such as BMP-2, Runx2, OCN, and ALP. The crystals with high cytotoxicity caused more calcium deposits on the cell surface, higher expression levels of osteogenic protein, and stronger osteogenic transformation abilities. These findings elucidated the relationship between crystal shape and cytotoxicity and provided theoretical references for decreasing the risks of vascular calcification.

Waiting for Aπαταω: 250 Years Later

Scientific articles have been traditionally written from single points of view. In contrast, new knowledge is derived strictly from a dialectical process, through interbreeding of partially disparate perspectives. Dialogues, therefore, present a more veritable form for representing the process behind knowledge creation. They are also less prone to dogmatically disseminate ideas than monologues, alongside raising awareness of the necessity for discussion and challenging of differing points of view, through which knowledge evolves. Here we celebrate 250 years since the discovery of the chemical identity of the inorganic component of bone in 1769 by Johan Gottlieb Gahn through one such imaginary dialogue between two seasoned researchers and aficionados of this material. We provide the statistics on ups and downs in the popularity of this material throughout the history and also discuss important achievements and challenges associated with it. The shadow of Samuel Beckett's Waiting for Godot is cast over the dialogue, acting as its frequent reference point and the guide. With this dialogue presented in the format of a play, we provide hope that conversational or dramaturgical compositions of scientific articles - albeit virtually prohibited from the scientific literature of the day - may become more pervasive in the future.

A Brief Review about the Role of Nanomaterials, Mineral-Organic Nanoparticles, and Extra-Bone Calcification in Promoting Carcinogenesis and Tumor Progression

People come in contact with a huge number of nanoparticles (NPs) throughout their lives, which can be of both natural and anthropogenic origin and are capable of entering the body through swallowing, skin penetration, or inhalation. In connection with the expanding use of nanomaterials in various industrial processes, the question of whether there is a need to study the potentially adverse effects of NPs on human health becomes increasingly important. Despite the fact that the nature and the extent of damage caused depends on the chemical and the physical characteristics of individual NPs, there are also general mechanisms related to their toxicity. These mechanisms include the ability of NPs to translocate to various organs through endocytosis, as well as their ability to stimulate the production of reactive oxygen species (ROS), leading to oxidative stress, inflammation, genotoxicity, metabolic changes, and potentially carcinogenesis. In this review, we discuss the main characteristics of NPs and the effects they cause at both cellular and tissue levels. We also focus on possible mechanisms that underlie the relationship of NPs with carcinogenesis. We briefly summarize the main concepts related to the role of endogenous mineral organic NPs in the development of various human diseases and their participation in extra-bone calcification. Considering data from both our studies and those published in scientific literature, we propose the revision of some ideas concerning extra-bone calcification, since it may be one of the factors associated with the initiation of the mechanisms of immunological tolerance.

Investigation of foreign materials in gingival lesions: a clinicopathologic, energy-dispersive microanalysis of the lesions and in vitro confirmation of pro-inflammatory effects of the foreign materials

OBJECTIVES

This study aimed to evaluate the clinical and histopathologic features of gingival lesions containing foreign material (GLFMs). In parallel, the composition of the foreign material and its effects in primary human gingival fibroblasts (HGFs) were investigated.

STUDY DESIGN

Eighty-six GLFMs were retrieved from an oral pathology biopsy service. Clinical and microscopic data were analyzed, and the composition of the particles was identified by using energy-dispersive X-ray spectroscopy (EDX). Furthermore, HGFs were stimulated with silica (SiO₂) microparticles to investigate the production of collagen type 1 (COL-1), matrix metalloproteinase 2 (MMP2), and inflammatory cytokines.

RESULTS

GLFMs were most commonly found in women (60.5%) and most frequently described as white plaques. Histopathologic examination identified verrucous hyperplasia in 59% and epithelial dysplasia in 28% of the cases. EDX microanalysis revealed that Si (94%) was the most frequently detected foreign element. SiO₂ microparticles induced higher COL-1 expression; higher levels of proinflammatory cytokines, such as interleukin-6 (IL-6), IL-8, and transforming growth factor-β, and increased MMP-2 activity in HGFs.

CONCLUSIONS

There was a strong association between the presence of foreign material in the gingiva and white verrucous clinical lesions. In addition, the most common element in the foreign material was Si, and our in vitro findings demonstrate the importance of silica-mediated effects on gingival fibroblasts.

Quantification of a cell culture contaminant using 16S rDNA

In this study, we identified a "black dot"-like cell culture contaminant as a species belonging to the genus of Pusillimonas using 16S rDNA sequencing. Among all antibiotics tested, a combinatorial treatment of ampicillin and gentamicin both at 100 µg/mL was able to eliminate this contaminant. The contaminant was then visualized by fluorescence microscopy using propidium iodide staining and was found inside the cytosol of contaminated A549 cells. To characterize the efficacy of antibiotics for contaminant removal, we devised a quantitative method to determine the average number of 16S rDNA copies associated with a single A549 cell, which is directly proportional to the average number of contaminant per A549 cell. By using primers specific to the 16S rDNA sequence of the contaminant, we were able to estimate contaminants per single contaminated cell using both qPCR-based relative and absolute quantification.

Clinical implications of fetuin-A

Fetuin-A, also termed alpha2-Heremans-Schmid glycoprotein, is a 46kDa hepatocyte derived protein (hepatokine) and serves multifaceted functions.

Cryoprotectant-Free Freezing of Cells Using Liquid Marbles Filled with Hydrogel

Cryopreservation without cryoprotectant remains a significant challenge for the re-establishment of cell culture after freeze-thaw. Thus, finding an alternative and a simple cryopreservation method is necessary. Liquid marble (LM)-based digital microfluidics is a promising approach for cryoprotectant-free cryopreservation. However, the use of this platform to efficiently preserve samples with low cell density and well-controlled serum concentrations has not been investigated. We addressed this issue by embedding an agarose-containing fetal bovine serum (FBS) inside the LM. A low density of 500 cells/μL of murine 3T3 cells was selected for evaluating the postcryogenic survivability. The effects on the post-thaw cell viability of the concentration of agarose, the amount of FBS inside the agarose, and the volume of the LM were investigated systematically. This paper also presents an analysis on the changes in shape and crack size of post-thawed agarose. The results revealed that the embedded agarose gel serves as a controlled release mechanism of FBS and significantly improves cell viability. Post-thaw recovery sustains major cellular features, such as viability, cell adhesion, and morphology. The platform technology reported here opens up new possibilities to cryopreserve rare biological samples without the toxicity risk of cryoprotectants.

Comprehensive organic profiling of biological particles derived from blood

Mineral nanoparticles form in physiological and pathological processes occurring in the human body. The calcium phosphate mineral phase of the particles has affinity for proteins and lipids, but the complete profiling of the organic molecules that bind to the particles has not been described in detail. We report here a comprehensive analysis of organic components found in mineralo-organic particles derived from body fluids. Based on biological staining, fluorescent tagging, proteomics and metabolomics, our results indicate that the mineral particles bind to proteins, amino acids, carbohydrates, polysaccharides, phospholipids, fatty acids, DNA and low molecular weight metabolites. These results can be used to study the formation and effects of mineralo-organic particles in biological fluids.

Mineralo-organic nanoparticles in health and disease: an overview of recent findings

We observed earlier that mineralo-organic nanoparticles form in human body fluids when the concentrations of calcium, carbonate and phosphate exceed saturation. The particles have been shown to represent mineral precursors in developing bones and teeth as well as in ectopic calcification and kidney stones. Recent studies suggest that the mineral particles may also be involved in other physiological processes, including immune tolerance against the gut microbiota and food antigens. We review here the involvement of mineralo-organic nanoparticles in physiological and pathological processes and discuss recent findings that reveal novel and unexpected roles for these particles in the human body.

Biochemical transformation of calciprotein particles in uraemia

Calciprotein particles (CPP) have emerged as nanoscale mediators of phosphate-induced toxicity in Chronic Kidney Disease (CKD). Uraemia favors ripening of the particle mineral content from the amorphous (CPP-I) to the crystalline state (CPP-II) but the pathophysiological significance of this transformation is uncertain. Clinical studies suggest an association between CPP ripening and inflammation, vascular dysfunction and mortality. Although ripening has been modelled in vitro, it is unknown whether particles synthesised in serum resemble their in vivo counterparts. Here we show that in vitro formation and ripening of CPP in uraemic serum is characterised by extensive physiochemical rearrangements involving the accretion of mineral, loss of surface charge and transformation of the mineral phase from a spherical arrangement of diffuse domains of amorphous calcium phosphate to densely-packed lamellar aggregates of crystalline hydroxyapatite. These physiochemical changes were paralleled by enrichment with small soluble apolipoproteins, complement factors and the binding of fatty acids. In comparison, endogenous CPP represent a highly heterogeneous mixture of particles with characteristics mostly intermediate to synthetic CPP-I and CPP-II, but are also uniquely enriched for carbonate-substituted apatite, DNA fragments, small RNA and microbe-derived components. Pathway analysis of protein enrichment predicted the activation of cell death and pro-inflammatory processes by endogenous CPP and synthetic CPP-II alike. This comprehensive characterisation validates the use of CPP-II generated in uraemic serum as in vitro equivalents of their endogenous counterparts and provides insight into the nature and pathological significance of CPP in CKD, which may act as vehicles for various bioactive ligands.

Novel assessments of systemic calcification propensity

PURPOSE OF REVIEW

Blood is a biological fluid, which controls the precipitation of calcium and phosphate and transports mineral debris. This review presents and discusses the current concepts and novel assessment methods of systemic calcification propensity in blood.

RECENT FINDINGS

Calcium and phosphate combine with calcification-inhibiting proteins, mainly fetuin-A, to form amorphous calcium phosphate-containing primary calciprotein particles (CPPs). These nanosized mineral-protein clusters undergo spontaneous transformation to secondary CPP, which contain crystalline calcium phosphate. Two recently developed methods assess complementary aspects of the calcification propensity of serum. The CPP-fetuin-A method determines the amount of sedimentable fetuin-A, whereas the T50-Test determines the transformation time point T50 from amorphous to crystalline CPPs in artificially supersaturated serum.Clinical studies in renal patients have already demonstrated close associations of the CPP-fetuin-A method with all-cause mortality, severity of coronary calcification and aortic stiffness, and of the T50-Test with cardiovascular and all-cause mortality, renal graft failure and aortic stiffening.

SUMMARY

Systemic calcification propensity can be assessed by two novel methods providing complementary information about the status and performance of the humoral calcification-regulating system in serum. These tests may help guide better patient care in the future with the use of more individualized therapies.

Calciprotein particles as potential etiologic agents of idiopathic preterm birth

Preterm birth (PTB) is a leading cause of neonatal morbidity and mortality and is often preceded by preterm premature rupture of the membranes (PPROM) without an identifiable cause. Pathological calcification, the deposition of hydroxyapatite (HA) in nonskeletal tissues, has been implicated in degenerative diseases including atherosclerosis and aneurism rupture. Among pathogenic mechanisms, the aberrant aggregation of HA into calciprotein particles (CPPs) and the HA-induced differentiation of mesenchymal cells into osteoblasts (ectopic osteogenesis) have been implicated. We explored the hypothesis that CPPs form in human amniotic fluid (AF), deposit in fetal membranes, and are linked mechanistically to pathogenic pathways favoring PTB. We demonstrated that fetal membranes from women with idiopathic PPROM frequently show evidence of ectopic calcification and expression of osteoblastic differentiation markers. Concentrations of fetuin-A, an endogenous inhibitor of ectopic calcification, were decreased in AF of idiopathic PPROM cases, which reflected their reduced functional capacity to inhibit calcification. Using long-term cultures of sterile AF, we demonstrated coaggregation of HA with endogenous proteins, including fetuin-A. The fetuin-HA aggregates exhibited progressive growth in vitro in a pattern similar to CPPs. When applied to amniochorion explants, AF-derived CPPs induced structural and functional pathological effects recapitulating those noted for PPROM. Our results demonstrate that disruption of protein-mineral homeostasis in AF stimulates the formation and deposition of CPPs, which may represent etiologic agents of idiopathic PPROM. Therapeutic or dietary interventions aimed at maintaining the balance between endogenous HA formation and fetuin reserve in pregnant women may therefore have a role in preventing PTB.

Mineral particles stimulate innate immunity through neutrophil extracellular traps containing HMGB1

Calcium phosphate-based mineralo-organic particles form spontaneously in the body and may represent precursors of ectopic calcification. We have shown earlier that these particles induce activation of caspase-1 and secretion of IL-1β by macrophages. However, whether the particles may produce other effects on immune cells is unclear. Here, we show that these particles induce the release of neutrophil extracellular traps (NETs) in a size-dependent manner by human neutrophils. Intracellular production of reactive oxygen species is required for particle-induced NET release by neutrophils. NETs contain the high-mobility group protein B1 (HMGB1), a DNA-binding protein capable of inducing secretion of TNF-α by a monocyte/macrophage cell line and primary macrophages. HMGB1 functions as a ligand of Toll-like receptors 2 and 4 on macrophages, leading to activation of the MyD88 pathway and TNF-α production. Furthermore, HMGB1 is critical to activate the particle-induced pro-inflammatory cascade in the peritoneum of mice. These results indicate that mineral particles promote pro-inflammatory responses by engaging neutrophils and macrophages via signaling of danger signals through NETs.

Investigation of uranium interactions with calcium phosphate-binding proteins using ICP/MS and CE-ICP/MS

During long-term exposure, uranium accumulates in bone. Since uranium in U(vi) complexes shares similar coordination properties to calcium, this toxicant is assumed to be exchanged with calcium ions at the surfaces of bone mineral crystals. Recently, two proteins involved in bone turnover, fetuin A and osteopontin, were shown to exhibit a high affinity for U(vi). A common biochemical feature of both fetuin A and osteopontin is their inhibiting role in calcium phosphate precipitation. Therefore it is conceivable that complexation of U(vi) with these proteins may alter their interaction with calcium and/or calcium phosphate. Quantitative analyses of calcium, phosphorus and uranium performed using inductively coupled plasma/mass spectrometry (ICP/MS) demonstrated the inhibition of the precipitation of calcium phosphate by fetuin A and osteopontin for 2 h. In addition, the presence of U(vi) did not seem to alter the duration of this process. However, dynamic light scattering studies revealed that the size of the colloidal particles formed with osteopontin was altered by the presence of U(vi) in a concentration-dependent manner. Finally, using hyphenated capillary electrophoresis-ICP/MS (CE-ICP/MS), we showed that in these systems, at a low concentration of U(vi) (protein : U(vi) 8 : 1), U(vi) might remain in solution by forming a complex with proteins and not by sequestration of a precipitate of either autunite or uranyl orthophosphate.

Pleomorphic bacteria-like structures in human blood represent non-living membrane vesicles and protein particles

Although human blood is believed to be a sterile environment, recent studies suggest that pleomorphic bacteria exist in the blood of healthy humans. These studies have led to the development of "live-blood analysis," a technique used by alternative medicine practitioners to diagnose various human conditions, including allergies, cancer, cardiovascular disease and septicemia. We show here that bacteria-like vesicles and refringent particles form in healthy human blood observed under dark-field microscopy. These structures gradually increase in number during incubation and show morphologies reminiscent of cells undergoing division. Based on lipid analysis and Western blotting, we show that the bacteria-like entities consist of membrane vesicles containing serum and exosome proteins, including albumin, fetuin-A, apolipoprotein-A1, alkaline phosphatase, TNFR1 and CD63. In contrast, the refringent particles represent protein aggregates that contain several blood proteins. 16S rDNA PCR analysis reveals the presence of bacterial DNA in incubated blood samples but also in negative controls, indicating that the amplified sequences represent contaminants. These results suggest that the bacteria-like vesicles and refringent particles observed in human blood represent non-living membrane vesicles and protein aggregates derived from blood. The phenomena observed during live-blood analysis are therefore consistent with time-dependent decay of cells and body fluids during incubation ex vivo.

Calcium Phosphate Crystals from Uremic Serum Promote Osteogenic Differentiation in Human Aortic Smooth Muscle Cells

Recent study demonstrated that calcium phosphate (CaP) crystals isolated from high phosphate medium were a key contributor to arterial calcification. The present study further investigated the effects of CaP crystals induced by uremic serum on calcification of human aortic smooth muscle cells. This may provide a new insight for the development of uremic cardiovascular calcification. We tested the effects of uremic serum or normal serum on cell calcification. Calcification was visualized by staining and calcium deposition quantified. Expression of various bone-calcifying genes was detected by real-time PCR, and protein levels were quantified by western blotting or enzyme-linked immunosorbent assays. Pyrophosphate was used to investigate the effects of CaP crystals' inhibition. Finally, CaP crystals were separated from uremic serum to determine its specific pro-calcification effects. Uremic serum incubation resulted in progressively increased calcification staining and increased calcium deposition in HASMCs after 4, 8 and 12 days (P vs 0 day <0.001 for all). Compared to cells incubated in control serum, uremic serum significantly induced the mRNA expression of bone morphogenetic factor-2, osteopontin and RUNX2, and increased their protein levels as well (P < 0.05 for all). Inhibition of CaP crystals with pyrophosphate incubation prevented calcium deposition and bone-calcifying gene over-expression increased by uremic serum. CaP crystals, rather than the rest of uremic serum, were responsible for these effects. Uremic serum accelerates arterial calcification by mediating osteogenic differentiation. This effect might be mainly attributed to the CaP crystal content.

Translocation of mineralo-organic nanoparticles from blood to urine: a new mechanism for the formation of kidney stones?

Recent studies indicate that mineralo-organic nanoparticles form in various human body fluids, including blood and urine. These nanoparticles may form within renal tubules and increase in size in supersaturated urine, eventually leading to the formation of kidney stones. Here, we present observations suggesting that mineralo-organic nanoparticles found in blood may induce kidney stone formation via an alternative mechanism in which the particles translocate through endothelial and renal epithelial cells to reach urine. We propose that this alternative mechanism of kidney stone formation and the study of mineralo-organic nanoparticles in general may provide novel strategies for the early detection and treatment of ectopic calcifications and kidney stones.

Low molecular weight chitosan-coated polymeric nanoparticles for sustained and pH-sensitive delivery of paclitaxel

Low molecular weight chitosan (LMWC) is a promising polymer for surface modification of nanoparticles (NPs), which can impart both stealth effect and electrostatic interaction with cells at mildly acidic pH of tumors. We previously produced LMWC-coated NPs via covalent conjugation to poly(lactic-co-glycolic) acid (PLGA-LMWC NPs). However, this method had several weaknesses including inefficiency and complexity of the production as well as increased hydrophilicity of the polymer matrix, which led to poor drug release control. Here, we used the dopamine polymerization method to produce LMWC-coated NPs (PLGA-pD-LMWC NPs), where the core NPs were prepared with PLGA that served best to load and retain drugs and then functionalized with LMWC via polydopamine layer. The PLGA-pD-LMWC NPs overcame the limitations of PLGA-LMWC NPs while maintaining their advantages. First of all, PLGA-pD-LMWC NPs attenuated the release of paclitaxel to a greater extent than PLGA-LMWC NPs. Moreover, PLGA-pD-LMWC NPs had a pH-dependent surface charge profile and cellular interactions similar to PLGA-LMWC NPs, enabling acid-specific NP-cell interaction and enhanced drug delivery to cells in weakly acidic environment. Although the LMWC layer did not completely prevent protein binding in serum solution, PLGA-pD-LMWC NPs showed less phagocytic uptake than bare PLGA NPs.

Formation and characteristics of biomimetic mineralo-organic particles in natural surface water

Recent studies have shown that nanoparticles exist in environmental water but the formation, characteristics and fate of such particles remain incompletely understood. We show here that surface water obtained from various sources (ocean, hot springs, and soil) produces mineralo-organic particles that gradually increase in size and number during incubation. Seawater produces mineralo-organic particles following several cycles of filtration and incubation, indicating that this water possesses high particle-seeding potential. Electron microscopy observations reveal round, bacteria-like mineral particles with diameters of 20 to 800 nm, which may coalesce and aggregate to form mineralized biofilm-like structures. Chemical analysis of the particles shows the presence of a wide range of chemical elements that form mixed mineral phases dominated by calcium and iron sulfates, silicon and aluminum oxides, sodium carbonate, and iron sulfide. Proteomic analysis indicates that the particles bind to proteins of bacterial, plant and animal origins. When observed under dark-field microscopy, mineral particles derived from soil-water show biomimetic morphologies, including large, round structures similar to cells undergoing division. These findings have important implications not only for the recognition of biosignatures and fossils of small microorganisms in the environment but also for the geochemical cycling of elements, ions and organic matter in surface water.

Apoptosis-mediated endothelial toxicity but not direct calcification or functional changes in anti-calcification proteins defines pathogenic effects of calcium phosphate bions

Calcium phosphate bions (CPB) are biomimetic mineralo-organic nanoparticles which represent a physiological mechanism regulating the function, transport and disposal of calcium and phosphorus in the human body. We hypothesised that CPB may be pathogenic entities and even a cause of cardiovascular calcification. Here we revealed that CPB isolated from calcified atherosclerotic plaques and artificially synthesised CPB are morphologically and chemically indistinguishable entities. Their formation is accelerated along with the increase in calcium salts-phosphates/serum concentration ratio. Experiments in vitro and in vivo showed that pathogenic effects of CPB are defined by apoptosis-mediated endothelial toxicity but not by direct tissue calcification or functional changes in anti-calcification proteins. Since the factors underlying the formation of CPB and their pathogenic mechanism closely resemble those responsible for atherosclerosis development, further research in this direction may help us to uncover triggers of this disease.

Fatty acids and small organic compounds bind to mineralo-organic nanoparticles derived from human body fluids as revealed by metabolomic analysis

Nanoparticles entering the human body instantly become coated with a "protein corona" that influences the effects and distribution of the particles in vivo. Yet, whether nanoparticles may bind to other organic compounds remains unclear. Here we use an untargeted metabolomic approach based on ultra-performance liquid chromatography and quadruple time-of-flight mass spectrometry to identify the organic compounds that bind to mineral nanoparticles formed in human body fluids (serum, plasma, saliva, and urine). A wide range of organic compounds is identified, including fatty acids, glycerophospholipids, amino acids, sugars, and amides. Our results reveal that, in addition to the proteins identified previously, nanoparticles harbor an "organic corona" containing several fatty acids which may affect particle-cell interactions in vivo. This study provides a platform to study the organic corona of biological and synthetic nanoparticles found in the human body.

Detection and characterization of mineralo-organic nanoparticles in human kidneys

Ectopic calcification is associated with various human diseases, including atherosclerosis, cancer, chronic kidney disease, and diabetes mellitus. Although mineral nanoparticles have been detected in calcified blood vessels, the nature and role of these particles in the human body remain unclear. Here we show for the first time that human kidney tissues obtained from end-stage chronic kidney disease or renal cancer patients contain round, multilamellar mineral particles of 50 to 1,500 nm, whereas no particles are observed in healthy controls. The mineral particles are found mainly in the extracellular matrix surrounding the convoluted tubules, collecting ducts and loops of Henle as well as within the cytoplasm of tubule-delineating cells, and consist of polycrystalline calcium phosphate similar to the mineral found in bones and ectopic calcifications. The kidney mineral nanoparticles contain several serum proteins that inhibit ectopic calcification in body fluids, including albumin, fetuin-A, and apolipoprotein A1. Since the mineralo-organic nanoparticles are found not only within calcified deposits but also in areas devoid of microscopic calcifications, our observations indicate that the nanoparticles may represent precursors of calcification and renal stones in humans.

Nanoparticle conversion to biofilms: in vitro demonstration using serum-derived mineralo-organic nanoparticles

AIMS

Mineralo-organic nanoparticles (NPs) detected in biological fluids have been described as precursors of physiological and pathological calcifications in the body. Our main objective was to examine the early stages of mineral NP formation in body fluids.

MATERIALS & METHODS

A nanomaterial approach based on atomic force microscopy, dynamic light scattering, electron microscopy and spectroscopy was used.

RESULTS

The mineral particles, which contain the serum proteins albumin and fetuin-A, initially precipitate in the form of round amorphous NPs that gradually grow in size, aggregate and coalesce to form crystalline mineral films similar to the structures observed in calcified human arteries.

CONCLUSION

Our study reveals the early stages of particle formation and provides a platform to analyze the role(s) of mineralo-organic NPs in human tissues.

A story told by a single nanoparticle in the body fluid: demonstration of dissolution-reprecipitation of nanocrystals in a biological system

AIM

Analysis of the chemical composition of mineral particles found in the body is critical to understand the formation and effects of these entities in vivo. Yet, the possibility that biological fluids may modulate particle composition over time has not been examined. Materials & methods: Mineralo-organic nanoparticles similar to the ones that spontaneously form in human tissues were analyzed using electron microscopy, spectroscopy and proteomic analyses. 

RESULTS

 We show that the mineralo-organic nanoparticles assimilate various ions and minerals during incubation in ionic solutions simulating body fluids. The particles undergo dissolution-reprecipitation reactions that affect the final protein composition of the particles.

CONCLUSION

The reactions occurring at the mineral-water interface therefore modulate the ionic and organic composition of mineral nanoparticles formed in biological fluids, producing changes that may alter the effects of mineral particles and stones in vivo.

Nanobacteria in the pathogenesis of urolithiasis: Myth or reality?

Stone formation in the urinary tract is a common phenomenon with associated morbidity. The exact physicochemical factors responsible for stone formation are not clearly known. Over the past decade considerable interest has been generated in defining the role of nanobacteria in urinary stone formation. A review of the available literature has been carried out to give insights into their nature and outline their role in stone formation. The two aspects of nanobacteria that need to be considered include its biological nature and the other merely as mineralo-protein complexes. Though the current literature favors the concept of mineralo-protein particles, further research is needed to clearly define their nature. Whether living or nonliving, these apatite forming nanoparticles appear to play role in kidney stone formation.

Secondarily infected nonstruvite urolithiasis: a prospective evaluation

OBJECTIVE

To characterize patients who form nonstruvite stones associated with infection (secondarily infected calculi), and to define the bacteria associated with these.

MATERIALS AND METHODS

Patients undergoing percutaneous nephrolithotomy were prospectively recruited. Medical records were reviewed, and stones were analyzed using micro computed tomography and infrared spectroscopy. A fragment of each stone was sent for bacterial culture. Patients were categorized by stone culture results (SC ±) and the presence of struvite (ST ±). The Fisher exact test was used for comparison of proportion. Sterility of intraoperative SC was established with independently collected controls.

RESULTS

In total, 125 patients were enrolled: 24 SC+/ST-, 19 SC+/ST+, and 82 SC-/ST-. Proportions of patients with prior urologic surgery, diabetes, and immunodeficiency were similar between groups. Patients with neurogenic bladder were more likely to have SC+/ST+ stones or SC+/ST- stones than SC-/ST- stones (26% vs 8% vs 0%, respectively; P <.01). Among patients with metabolic evaluations, hypocitraturia was found in 31.6% (6 of 19) SC+/ST- patients, 46.7% (7 of 15) SC+/ST+ patients, and 26.0% (19 of 73) of SC-/ST- patients (P = .28). Approximately 40% of cultured organisms in the secondarily infected calculi possessed urease and another 40% citrate lyase activities.

CONCLUSION

Secondarily infected stones were detected in approximately 20% of this surgical cohort and may be more common than previously appreciated. Neurogenic bladder appeared to predispose patients to either struvite or secondarily infected stones. The role of bacterial infection in stone formation is unclear but may include alteration of urinary components, acting as a nidus for crystallization, or inducing inflammation.

Calcifying nanoparticles promote mineralization in vascular smooth muscle cells: implications for atherosclerosis

Background

Nano-sized complexes of calcium phosphate mineral and proteins (calcifying nanoparticles [CNPs]) serve as mineral chaperones. Thus, CNPs may be both a result and cause of soft tissue calcification processes. This study determined if CNPs could augment calcification of arterial vascular smooth muscle cells in vitro.

Methods

CNPs 210 nm in diameter were propagated in vitro from human serum. Porcine aortic smooth muscle cells were cultured for up to 28 days in medium in the absence (control) or presence of 2 mM phosphate ([P] positive calcification control) or after a single 3-day exposure to CNPs. Transmission electron-microscopy was used to characterize CNPs and to examine their cellular uptake. Calcium deposits were visualized by light microscopy and von Kossa staining and were quantified by colorimetry. Cell viability was quantified by confocal microscopy of live-/dead-stained cells and apoptosis was examined concurrently by fluorescent labeling of exposed phosphatidylserine.

Results

CNPs, as well as smaller calcium crystals, were observed by transmission electron-microscopy on day 3 in CNP-treated but not P-treated cells. By day 28, calcium deposits were visible in similar amounts within multicellular nodules of both CNP- and P-treated cells. Apoptosis increased with cell density under all treatments. CNP treatment augmented the density of apoptotic bodies and cellular debris in association with mineralized multicellular nodules.

Conclusion

Exogenous CNPs are taken up by aortic smooth muscle cells in vitro and potentiate accumulation of smooth-muscle-derived apoptotic bodies at sites of mineralization. Thus, CNPs may accelerate vascular calcification.

Of nanobacteria, nanoparticles, biofilms and their role in health and disease: facts, fancy and future

Nanobacteria have been at the center of a major scientific controversy in recent years owing to claims that they represent not only the smallest living microorganisms on earth but also new emerging pathogens associated with several human diseases. We and others have carefully examined these claims and concluded that nanobacteria are in fact nonliving mineralo-organic nanoparticles (NPs) that form spontaneously in body fluids. We have shown that these mineral particles possess intriguing biomimetic properties that include the formation of cell- and tissue-like morphologies and the possibility to grow, proliferate and propagate by subculture. Similar mineral NPs (bions) have now been found in both physiological and pathological calcification processes and they appear to represent precursors of physiological calcification cycles, which may at times go awry in disease conditions. Furthermore, by functioning at the nanoscale, these mineralo-organic NPs or bions may shed light on the fate of nanomaterials in the body, from both nanotoxicological and nanopathological perspectives.

Clinical implications of calcifying nanoparticles in dental diseases: a critical review

BACKGROUND

Unknown cell-culture contaminants were described by Kajander and Ciftçioğlu in 1998. These contaminants were called nanobacteria initially and later calcifying nanoparticles (CNPs). Their exact nature is unclear and controversial. CNPs have unique and unusual characteristics, which preclude placing them into any established evolutionary branch of life.

AIM

The aim of this systematic review was to assess published data concerning CNPs since 1998 in general and in relation to dental diseases in particular.

MATERIALS AND METHODS

The National Library of Medicine (PubMed) and Society of Photographic Instrumentation Engineers (SPIE) electronic and manual searches were conducted. Nanobacteria and calcifying nanoparticles were used as keywords. The search yielded 135 full-length papers. Further screening of the titles and abstracts that followed the review criteria resulted in 43 papers that met the study aim.

CONCLUSION

The review showed that the existence of nanobacteria is still controversial. Some investigators have described a possible involvement of CNPs in pulpal and salivary gland calcifications, as well as the possible therapeutic use of CNPs in the treatment of cracked and/or eroded teeth.

A phosphate-centric paradigm for pathophysiology and therapy of chronic kidney disease

Extracellular phosphate is toxic to the cell at high concentrations. When the phosphate level is increased in the blood by impaired urinary phosphate excretion, premature aging ensues. When the phosphate level is increased in the urine by dietary phosphate overload, this may lead to kidney damage (tubular injury and interstitial fibrosis). Extracellular phosphate exerts its cytotoxicity when it forms insoluble nanoparticles with calcium and fetuin-A, referred to as calciprotein particles (CPPs). CPPs are highly bioactive ligands that can induce various cellular responses, including osteogenic transformation of vascular smooth muscle cells and cell death in vascular endothelium and renal tubular epithelium. CPPs are detected in the blood of animal models and patients with chronic kidney disease (CKD) and associated with adaptation of the endocrine axes mediated by fibroblast growth factor-23 (FGF23) and Klotho that regulate mineral metabolism and aging. These observations have raised the possibility that CPPs may contribute to the pathophysiology of CKD. This notion, if validated, is expected to provide new diagnostic and therapeutic targets for CKD.

Bions: a family of biomimetic mineralo-organic complexes derived from biological fluids

Mineralo-organic nanoparticles form spontaneously in human body fluids when the concentrations of calcium and phosphate ions exceed saturation. We have shown previously that these mineralo-organic nanoparticles possess biomimetic properties and can reproduce the whole phenomenology of the so-called nanobacteria-mineralized entities initially described as the smallest microorganisms on earth. Here, we examine the possibility that various charged elements and ions may form mineral nanoparticles with similar properties in biological fluids. Remarkably, all the elements tested, including sodium, magnesium, aluminum, calcium, manganese, iron, cobalt, nickel, copper, zinc, strontium, and barium form mineralo-organic particles with bacteria-like morphologies and other complex shapes following precipitation with phosphate in body fluids. Upon formation, these mineralo-organic particles, which we term bions, invariably accumulate carbonate apatite during incubation in biological fluids; yet, the particles also incorporate additional elements and thus reflect the ionic milieu in which they form. Bions initially harbor an amorphous mineral phase that gradually converts to crystals in culture. Our results show that serum produces a dual inhibition-seeding effect on bion formation. Using a comprehensive proteomic analysis, we identify a wide range of proteins that bind to these mineral particles during incubation in medium containing serum. The two main binding proteins identified, albumin and fetuin-A, act as both inhibitors and seeders of bions in culture. Notably, bions possess several biomimetic properties, including the possibility to increase in size and number and to be sub-cultured in fresh culture medium. Based on these results, we propose that bions represent biological, mineralo-organic particles that may form in the body under both physiological and pathological homeostasis conditions. These mineralo-organic particles may be part of a physiological cycle that regulates the function, transport and disposal of elements and minerals in the human body.

Zinc oxide nanoparticles inhibit Ca2+-ATPase expression in human lens epithelial cells under UVB irradiation

Epidemiological and experimental studies have revealed that lens epithelial cells exposed to ultraviolet B (UVB) light could be induced apoptosis, and lens epithelial cell apoptosis can initiate cataractogenesis. Posterior capsular opacification (PCO), the most frequent complication after cataract surgery, is induced by the proliferation, differentiation, migration of lens epithelial cells. Thus, inhibiting the proliferation of lens epithelial cells could reduce the occurrence of PCO. It is reported that zinc oxide (ZnO) nanoparticles have great potential for the application of biomedical field including cancer treatment. In the present study, we investigated the cytotoxic effect of ZnO nanoparticles on human lens epithelial cell (HLEC) viability. In addition, changes in cell nuclei, apoptosis, reactive oxygen species and intracellular calcium ion levels were also investigated after cells treated with ZnO nanoparticles in the presence and absence of UVB irradiation. Meanwhile, the expression of plasma membrane calcium ATPase 1 (PMCA1) was also determined at gene and protein levels. The results indicate that ZnO nanoparticles and UVB irradiation have synergistic inhibitory effect on HLEC proliferation in a concentration-dependent manner. ZnO nanoparticles can increase the intracellular calcium ion level, disrupt the intracellular calcium homeostasis, and decrease the expression level of PMCA1. UVB irradiation can strengthen the effect of reduced expression of PMCA1, suggesting that both UVB irradiation and ZnO nanoparticles could exert inhibitory effect on HLECs via calcium-mediated signaling pathway. ZnO nanoparticles have great potential for the treatment of PCO under UVB irradiation.

Ectopic calcification: importance of common nanoparticle scaffolds containing oxidized acidic lipids

The term nanobacteria, sometimes referred to as nanobacteria-like particles (NLPs), is presently recognized as a misnomer for inert calcified nanoparticles. However, misinterpretation of its propagation as a living organism still continues. Ultrastructural and elemental analyses, combining immuno-electron microscopy with an original NLP isolate (P-17) derived from urinary stones, and an IgM monoclonal antibody (CL-15) raised against P-17 have now revealed that, oxidized lipids with acidified functional groups were key elements in NLP propagation. Lamellar structures composed of acidic/oxidized lipids provided structural scaffolds for carbonate apatite crystals. During in vitro culture, lipid peroxidation induced by γ-irradiation of FBS was a major cause of accelerated NLP propagation. In pathological tissue samples from hyperlipidemic atherosclerosis-prone mice, CL-15 co-localized with fatty plaques, macrophage infiltrates and osteocalcin staining of aortic valve lesions. These observations indicate that naturally occurring NLP composed of mineralo-oxidized lipids complexes are generated as by-products rather than etiological agents of chronic inflammation.

FROM THE CLINICAL EDITOR

The term "nanobacteria-like particles (NLPs)" is presently recognized as a misnomer for inert calcified nanoparticles as opposed to living organisms. This study convincingly demonstrates that naturally occurring NLPs composed of mineralo-oxidized lipid complexes are generated as by-products rather than etiological agents of chronic inflammation.

Membrane vesicles nucleate mineralo-organic nanoparticles and induce carbonate apatite precipitation in human body fluids

Recent studies indicate that membrane vesicles (MVs) secreted by various cells are associated with human diseases, including arthritis, atherosclerosis, cancer, and chronic kidney disease. The possibility that MVs may induce the formation of mineralo-organic nanoparticles (NPs) and ectopic calcification has not been investigated so far. Here, we isolated MVs ranging in size between 20 and 400 nm from human serum and FBS using ultracentrifugation and sucrose gradient centrifugation. The MV preparations consisted of phospholipid-bound vesicles containing the serum proteins albumin, fetuin-A, and apolipoprotein A1; the mineralization-associated enzyme alkaline phosphatase; and the exosome proteins TNFR1 and CD63. Notably, we observed that MVs induced mineral precipitation following inoculation and incubation in cell culture medium. The mineral precipitates consisted of round, mineralo-organic NPs containing carbonate hydroxyapatite, similar to previous descriptions of the so-called nanobacteria. Annexin V-immunogold staining revealed that the calcium-binding lipid phosphatidylserine (PS) was exposed on the external surface of serum MVs. Treatment of MVs with an anti-PS antibody significantly decreased their mineral seeding activity, suggesting that PS may provide nucleating sites for calcium phosphate deposition on the vesicles. These results indicate that MVs may represent nucleating agents that induce the formation of mineral NPs in body fluids. Given that mineralo-organic NPs represent precursors of calcification in vivo, our results suggest that MVs may initiate ectopic calcification in the human body.

Physicochemical and biological properties of biomimetic mineralo-protein nanoparticles formed spontaneously in biological fluids

Recent studies indicate that mineral nanoparticles (NPs) form spontaneously in human body fluids. These biological NPs represent mineral precursors that are associated with ectopic calcifications seen in various human diseases. However, the parameters that control the formation of mineral NPs and their possible effects on human cells remain poorly understood. Here a nanomaterial approach to study the formation of biomimetic calcium phosphate NPs comparable to their physiological counterparts is described. Particle sizing using dynamic light scattering reveals that serum and ion concentrations within the physiological range yield NPs below 100 nm in diameter. While the particles are phagocytosed by macrophages in a size-independent manner, only large particles or NP aggregates in the micrometer range induce cellular responses that include production of mitochondrial reactive oxygen species, caspase-1 activation, and secretion of interleukin-1β (IL-1β). A comprehensive proteomic analysis reveals that the particle-bound proteins are similar in terms of their identity and number, regardless of particle size, suggesting that protein adsorption is independent of particle size and curvature. In conclusion, the conditions underlying the formation of mineralo-protein particles are similar to the ones that form in vivo. While mineral NPs do not activate immune cells, they may become pro-inflammatory and contribute to pathological processes once they aggregate and form larger mineral particles.

Nanoparticle-based test measures overall propensity for calcification in serum

Vascular and soft tissue calcification contributes to cardiovascular morbidity and mortality in both the general population and CKD. Because calcium and phosphate serum concentrations are near supersaturation, the balance of inhibitors and promoters critically influences the development of calcification. An assay that measures the overall propensity for calcification to occur in serum may have clinical use. Here, we describe a nanoparticle-based assay that detects, in the presence of artificially elevated calcium and phosphate concentrations, the spontaneous transformation of spherical colloidal primary calciprotein particles (CPPs) to elongate crystalline secondary CPPs. We used characteristics of this transition to describe the intrinsic capacity of serum to inhibit the precipitation of calcium and phosphate. Using this assay, we found that both the sera of mice deficient in fetuin-A, a serum protein that inhibits calcification, and the sera of patients on hemodialysis have reduced intrinsic properties to inhibit calcification. In summary, we developed a nanoparticle-based test that measures the overall propensity for calcification in serum. The clinical use of the test requires evaluation in a prospective study.