Peculiarities in sintering behavior of Ca-deficient hydroxyapatite nanopowders

Lukić, Miodrag J.; Veselinović, Ljiljana; Stojanović, Zoran; Kržmanc, Marjeta Maček; Bračko, Ines; Škapin, Srečo D.; Marković, Smilja; Uskoković, Dragan

doi:10.1016/j.matlet.2011.10.085

Cited by 15 publications

(20 citation statements)

References 11 publications

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“…A detailed characterization of SHAp and CDHAp powders was the subject of our previous papers [34][35][36]. Here, we point out the powders' properties: phase composition, degree of crystallinity, particle size distribution, stoichiometry, morphology and specific surface area, which influenced sinterability and consequently the quality of the FGMs.…”

Section: Characteristics Of Starting Powdersmentioning

confidence: 94%

“…The precipitate was washed out to pH 7 with distilled water to remove residual ions. After filtering, the filter cake was dried in an oven at 80 1C during 18 h, and grounded to obtain the powdered materials [34][35][36]. Phase composition of the powders was determined using a powder X-ray diffractometer (Philips PW 1050; Almelo, The Netherlands).…”

Section: Starting Powdersmentioning

confidence: 99%

“…Densification curves for CDHAp exhibit very different behavior than those for SHAp: (1) the densification starts around 800 1C and does not finish at 1200 1C, (2) the beginning of densification is shifted to the lower temperatures with faster heating; also, the faster heating results in higher densification. The unusual behavior that increased heating rate increases densification has been explained by two processes: (1) β-TCP formation kinetics, which occur during heating and hinders densification, and (2) influence of surface diffusion of CDHAp system [36,39,42]. Furthermore, previously it has been found that amount of TCP phase, representing the sum of β-and α-TCP, exponentially increases with the decrease of heating rate [36].…”

Section: Designing Of Fgms and Sinteringmentioning

confidence: 99%

“…The unusual behavior that increased heating rate increases densification has been explained by two processes: (1) β-TCP formation kinetics, which occur during heating and hinders densification, and (2) influence of surface diffusion of CDHAp system [36,39,42]. Furthermore, previously it has been found that amount of TCP phase, representing the sum of β-and α-TCP, exponentially increases with the decrease of heating rate [36]. The von Mises stresses were used as the key indicators to determine stress levels and evaluate the stress distribution in FGM-2.…”

Section: Designing Of Fgms and Sinteringmentioning

confidence: 99%

“…Besides, in the aim to produce nanostructured FGMs, instead of conventional sintering, TSS was applied. The TSS conditions were determined previously [34], while, the heating rate of 2 1C/min was chosen since the fact that yields the largest amount of TCP was produced by CDHAp phase transformation [36].…”

Section: Designing Of Fgms and Sinteringmentioning

confidence: 99%

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Designing, fabrication and characterization of nanostructured functionally graded HAp/BCP ceramics

Marković

Lukić

Škapin

et al. 2015

Ceramics International

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Nanostructured calcium phosphate functionally graded materials (FGMs) with simultaneous gradients of density, phase composition, and mechanical properties were fabricated by consecutive uniaxial pressing of stoichiometric (SHAp) and calcium deficient (CDHAp) hydroxyapatite powders in multilayered samples and reaction sintering. During sintering procedure SHAp composition remained stable (HAp) while CDHAp was phase transformed in biphasic calcium phosphate (BCP, i.e. HAp þβ-TCP) yielding HAp/BCP FGMs. To reduce mismatch stress between adjacent layers, generated during sintering, gradient of phase composition was optimized by introducing intermediate layer(s) made from a mixture of SHAp and CDHAp in an appropriate mass ratio. Optimal processing conditions for preparation of nanostructured ceramics were provided via two-step sintering. High-quality FGMs structure, without delamination, cracks and micro-structural damages was observed by an SEM technique; moreover, a detailed examination by FE-SEM established the unidirectional (perpendicular with respect to the layers) gradual change of microstructure, from fully dense to $40% of porosity. Detailed micro-Raman and FTIR spectroscopy studies showed an increase of β-TCP amount along the FGMs height, confirming gradient of phase composition. Mechanical properties measured by microindentation revealed gradual change of microhardness from 650 to 115 HV, with simultaneous change of Young's modulus from 92 to 24 GPa.

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Section: Characteristics Of Starting Powdersmentioning

confidence: 94%

Section: Starting Powdersmentioning

confidence: 99%

Section: Designing Of Fgms and Sinteringmentioning

confidence: 99%

Section: Designing Of Fgms and Sinteringmentioning

confidence: 99%

Section: Designing Of Fgms and Sinteringmentioning

confidence: 99%

See 3 more Smart Citations

Designing, fabrication and characterization of nanostructured functionally graded HAp/BCP ceramics

Marković

Lukić

Škapin

et al. 2015

Ceramics International

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Association of noninvasively measured renal protein biomarkers with histologic features of lupus nephritis

Brunner

Bennett

Mina

et al. 2012

Arthritis & Rheumatism

143

111

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Objective To investigate the relationship of urinary biomarkers (UBM) and established measures of renal function (EMRF) to the histological findings with lupus nephritis (LN); and to test whether certain combinations of the above mentioned laboratory measures are diagnostic of specific histological features of LN. Methods Urine samples of 76 patients were collected within 2 months of a kidney biopsy and assayed for the UBM: lipocalin-like prostaglandin-D synthetase (LPGDS), α1-acid-glycoprotein (AAG), transferrin (TF), ceruloplasmin (CP), neutrophil-gelatinase associated lipocalin (NGAL), and monocyte chemotactic factor 1 (MCP1). Using non-parametric analyses, UBM and EMRF levels were compared to histological features seen with LN: mesangial expansion, capillary proliferation, crescent formation, necrosis, wire loops, fibrosis, tubular atrophy, and epimembranous deposits. The area under the receiver operating characteristic (AUC) curve was calculated to predict LN activity, chronicity or membranous LN. Results There was a differential increase of the UBM that formed a pattern reflective of specific histological features seen with active LN. The combination of MCP1, AAG, CP plus protein:creatinine ratio were excellent in predicting LN activity (AUC=0.85). NGAL together with creatinine clearance plus MCP1 was an excellent (AUC=0.83) and MCP1, AAG, creatinine clearance plus C4 (AUC=0.75) a good diagnostic test of LN chronicity and membranous LN, respectively. Conclusions Select UBM are associated with specific tissue changes observed with LN activity and chronicity. Especially in combination with select EMRF, UBM are well-suited to non-invasively quantify LN activity, LN chronicity, and the presence of membranous LN.

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Phase composition control of calcium phosphate nanoparticles for tunable drug delivery kinetics and treatment of osteomyelitis. I. Preparation and drug release

Uskoković

Desai

2012

J Biomedical Materials Res

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Developed in this study is a multifunctional material for simultaneous osseoinduction and drug delivery, potentially applicable in the treatment of osteomyelitis. It is composed of agglomerates of nanoparticles of calcium phosphate (CAP) with different monophasic contents. The drug loading capacity and the release kinetics were investigated on two model drug compounds with different chemical structures, sizes and adsorption propensities: bovine serum albumin and fluorescein. Loading of CAP powders with small molecule drugs was achieved by physisorption and desiccation-induced agglomeration of nanoparticulate subunits into microscopic blocks. The material dissolution rate and the drug release rate depended on the nature of the CAP phase, decreasing from monocalcium phosphate to monetite to amorphous CAP and calcium pyrophosphate to hydroxyapatite. The sustained release of the two model drugs was shown to be directly relatable to the degradation rate of CAP carriers. It was demonstrated that the degradation rate of the carrier and the drug release kinetics could be made tunable within the time scale of 1–2 h for the most soluble CAP phase, monocalcium phosphate, to 1–2 years for the least soluble one, hydroxyapatite. From the standpoint of antibiotic therapy for osteomyelitis, typically lasting for six weeks, the most prospective CAP powder was amorphous CAP with its release time scale for a small organic molecule, the same category to which antibiotics belong, of 1 – 2 months under the conditions applied in our experiments. By combining these different CAP phases in various proportions, drug release profiles could be tailored to the therapeutic occasion.

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Peculiarities in sintering behavior of Ca-deficient hydroxyapatite nanopowders

Cited by 15 publications

References 11 publications

Designing, fabrication and characterization of nanostructured functionally graded HAp/BCP ceramics

Designing, fabrication and characterization of nanostructured functionally graded HAp/BCP ceramics

Association of noninvasively measured renal protein biomarkers with histologic features of lupus nephritis

Phase composition control of calcium phosphate nanoparticles for tunable drug delivery kinetics and treatment of osteomyelitis. I. Preparation and drug release

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