Influence of surface treatment of carbon fiberson electrochemical crystallization of calcium phosphate

Electrodeposition technique was used to coat calcium phosphate on carbon fiber which can be used to reinforce hydroxyapatite. The differences between fibers treated with and without nitric acid in electrodeposition were evaluated. The X-ray diffractometry results show that CaHPO4·2H2O is obtained as the kind of calcium phosphate coating on carbon fiber. The scanning electron microscopy photographs and deposit kinetic curve indicate that the influences of the functional group attained by nitric acid treatment, the crystal morphology and crystallization of the coating layers on the fiber with and without treatment rate are obviously different. The functional group, especially the acidic group, can act as nucleation centers of electrochemical crystallization.

Synthesis of Crystalline Hydroxyapatite from CaCO_3 and CaHPO_4·2H_2O by Mechanochemical Method

The mixture of CaHPO 4·2H 2O and CaCO 3 was ground in an aqueous system under appropriate conditions to investigate the mechanochemical reaction for the synthesis of crystalline hydroxyapatite (HA) powder. Hydroxyapatite of high crystallinity powder including trace Ca 10 (PO 4) 6CO 3(OH) and Ca 9HPO 4(PO 4) 6OH can be synthesized by mechanical activation without further thermal treatment at a high temperature. The synthesis reaction during the grinding process was almost completed within 1h. The as-ground powder exhibits a particle distribution of 20-100nm in size with a spherical or rodlike morphology. The composition and degree of crystallinity of the mechanochemical synthesized hydroxyapatite powders were coincident with the cement-type hydroxyapatite.

Age and Calcium Sources in Laying Hen Feed Affect Calcium Digestibility

The apparent calcium (Ca) digestibility coefficient (ADC) and true digestibility coefficient (TDC) of different inorganic calcium sources were determined in laying hens of different ages. Three Ca digestibility tests were carried out, each assessing 240 Lohmann Brown lineage laying hens distributed in a completely randomized design. Nine dietary treatments were arranged in a 3 × 3 factorial design consisting of three ages (40, 50 and 70 weeks) × three Ca (dicalcium phosphate (DCP) sources, fine (FL) and coarse (CL)) limestone, comprising eight replicates per treatment of six birds per experimental unit. Regarding the DCP, the ADC was higher (P < 0.05) in 40-week-old birds. The DCP ADC for 40-, 50- and 70-week-old birds was 0.889, 0.613 and 0.712, respectively. No effect (P > 0.05) of age on the ADC was noted for either FL or CL. Comparing Ca sources, DCP exhibited a higher (P < 0.05) ADC (0.889), followed by FL (0.699) and CL (0.515), in 40-week-old birds. DCP (0.712) and FL (0.652) presented (P < 0.05) higher ADC compared to CL (0.482), in 70-week-old birds. No effect of Ca sources at 50 weeks on the ADC was observed (P > 0.05). Endogenous loss values of 790, 860 and 930 mg·kg-1 of consumed dry matter were observed at 40, 50 and 70 weeks, respectively. For the TDC, no interaction (P > 0.05) was observed between Ca sources and bird age. The highest TDC value (P > 0.05) was found in birds fed DCP (0.786) followed by FL (0.637) and CL (0.534). In addition, birds at 40 weeks of age (0.714) exhibited higher TDC values (P < 0.05) compared to animals at 50 weeks of age (0.608). The findings reported herein demonstrate that the true digestibility is greater in the youngest birds and that consumed the DCP and the FL in relation to the birds that consumed the CL.

Next-generation resorbable polymer scaffolds with surface-precipitated calcium phosphate coatings

Next-generation synthetic bone graft therapies will most likely be composed of resorbable polymers in combination with bioactive components.In this article,we continue our exploration of E1001(1k),a tyrosine-derived polycarbonate,as an orthopedic implant material.Specifically,we use E1001(1k),which is degradable,nontoxic,and osteoconductive,to fabricate porous bone regeneration scaffolds that were enhanced by two different types of calcium phosphate(CP)coatings:in one case,pure dicalcium phosphate dihydrate was precipitated on the scaffold surface and throughout its porous structure(E1001(1k)+CP).In the other case,bone matrix minerals(BMM)such as zinc,manganese and fluoride were co-precipitated within the dicalcium phosphate dihydrate coating(E1001(1k)+BMM).These scaffold compositions were compared against each other and against ChronOS(Synthes USA,West Chester,PA,USA),a clinically used bone graft substitute(BGS),which served as the positive control in our experimental design.This BGS is composed of poly(lactide co-e-caprolactone)and beta-tricalcium phosphate.We used the established rabbit calvaria critical-sized defect model to determine bone regeneration within the defect for each of the three scaffold compositions.New bone formation was determined after 2,4,6,8 and 12 weeks by micro-computerized tomography(mCT)and histology.The experimental tyrosine-derived polycarbonate,enhanced with dicalcium phosphate dihydrate,E1001(1k)+CP,supported significant bone formation within the defects and was superior to the same scaffold containing a mix of BMM,E1001(1k)+BMM.The comparison with the commercially available BGS was complicated by the large variability in bone formation observed for the laboratory preparations of E1001(1k)scaffolds.At all time points,there was a trend for E1001(1k)+CP to be superior to the commercial BGS.However,only at the 6-week time point did this trend reach statistical significance.Detailed analysis of the μCT data suggested an increase in bone formation from 2 through 12 weeks in implant sites treated with E1001(1k)+CP.At 2 and 4 weeks post-implantation,bone formation occurred at the interface where the E1001(1k)+CP scaffold was in contact with the bone borders of the implant site.Thereafter,during weeks 6,8 and 12 bone formation progressed throughout the E1001(1k)+CP test implants.This trend was not observed with E1001(1k)+BMM scaffolds or the clinically used BGS.Our results suggest that E1001(1k)+CP should be tested further for osteoregenerative applications.

Influences of LaCl3 on the mineral phase transformation during osteoblast mineralization in vitro

Rat calvarial osteoblasts were treated with lanthanum chloride（LaCl3） to explore its effect on the mineral crystalline phase during the process of osteoblast calcification in uitro.The results confirmed that La was readily deposited in the mineral component of the matrix.Employing high-resolution transmission electron microscopy and Fourier transform infrared microspectroscopy techniques,we demonstrated that features comparable to dicalcium phosphate dihydrate（DCPD） and octacalcium phosphate,and hydroxyapatite（HAP） were detected in the mineral phases in uitro.Particularly,LaCl3 treatment retarded conversion from DCPD-like phase into HAP during mineralization.In addition,La was introduced in DCPD powder during wet chemical synthesis.When compared with that of La-free DCPD,the dissolution rate of La-incorporated DCPD was lower,thereby leading to a delayed DCPD-to-HAP phase transformation.Thus,it can be concluded that LaCl3 treatment influences the kinetics of inorganic phase transition by decreasing the dissolution rate of DCPD.

Mineralization of Zein Films by Biomimetic Process

The transparent or opaque zein film was prepared by a phase separation method with a zein ethanol aqueous solution.The circular zein film was self-assembled on the air-water interface.According to the images by scanning electron microscopy,the upper surface of film is flat and smooth and the downward surface presents a complex reticulation structure of corn protein fiber.Zein film as a biomimetic mineralization template is used to synthesize calcium phosphate crystals by a bioinspired mineralization process.Randomly oriented apatite crystals appear on the both surfaces of zein film after immersion in lOxsimulated body fluid,and the phase composition and morphology of the deposited calcium apatite are also distinguished from deposited location and immersion time.The phase transformation process from dicalcium phosphate dihydrate into hydroxyapatite(HAp) phase was investigated by X-ray powder diffraction,transmission electron microscopy and Fourier transform infrared spectroscopy,respectively.Based on the results by energy dispersive X-ray spectroscopy,the Ca/P ratio of the deposited apatite increases with the transformation from DCPD to HAp.The HAp/Zein films possess the excellent biodegradable structural features,and the coating of HAp crystallites has some potential applications for bone repair and regeneration.