Calcium carbonate-calcium phosphate mixed cement compositions for bone reconstruction

The feasibility of making calcium carbonate-calcium phosphate (CaCO3-CaP) mixed cements, comprising at least 40 % (w/w) CaCO3 in the dry powder ingredients, has been demonstrated. Several original cement compositions were obtained by mixing metastable crystalline calcium carbonate phases with metastable amorphous or crystalline calcium phosphate powders in aqueous medium. The cements set within at most 1 hour at 37°C in atmosphere saturated with water. The hardened cement is microporous and exhibits weak compressive strength. The setting reaction appeared to be essentially related to the formation of a highly carbonated nanocrystalline apatite phase by reaction of the mestastable CaP phase with part or almost all of the metastable CaCO3 phase. The recrystallization of metastable CaP varieties led to a final cement consisting of a highly carbonated poorly crystalline apatite (PCA) analogous to bone mineral associated with various amounts of vaterite and/or aragonite. The presence of controlled amounts of CaCO3 with a higher solubility than the apatite formed in the well-developed calcium phosphate cements might be of interest to increase resorption rates in biomedical cement and favor its replacement by bone tissue. Cytotoxicity testing revealed excellent cytocompatibility of CaCO3-CaP mixed cement compositions

Treatment of Ligament Constructs with Exercise-conditioned Serum: A Translational Tissue Engineering Model.

In vitro experiments are essential to understand biological mechanisms; however, the gap between monolayer tissue culture and human physiology is large, and translation of findings is often poor. Thus, there is ample opportunity for alternative experimental approaches. Here we present an approach in which human cells are isolated from human anterior cruciate ligament tissue remnants, expanded in culture, and used to form engineered ligaments. Exercise alters the biochemical milieu in the blood such that the function of many tissues, organs and bodily processes are improved. In this experiment, ligament construct culture media was supplemented with experimental human serum that has been 'conditioned' by exercise. Thus the intervention is more biologically relevant since an experimental tissue is exposed to the full endogenous biochemical milieu, including binding proteins and adjunct compounds that may be altered in tandem with the activity of an unknown agent of interest. After treatment, engineered ligaments can be analyzed for mechanical function, collagen content, morphology, and cellular biochemistry. Overall, there are four major advantages versus traditional monolayer culture and animal models, of the physiological model of ligament tissue that is presented here. First, ligament constructs are three-dimensional, allowing for mechanical properties (i.e., function) such as ultimate tensile stress, maximal tensile load, and modulus, to be quantified. Second, the enthesis, the interface between boney and sinew elements, can be examined in detail and within functional context. Third, preparing media with post-exercise serum allows for the effects of the exercise-induced biochemical milieu, which is responsible for the wide range of health benefits of exercise, to be investigated in an unbiased manner. Finally, this experimental model advances scientific research in a humane and ethical manner by replacing the use of animals, a core mandate of the National Institutes of Health, the Center for Disease Control, and the Food and Drug Administration

Structural studies of hydrated samples of amorphous calcium phosphate and phosphoprotein nanoclusters

There are abundant examples of nanoclusters and inorganic microcrystals in biology. Their study under physiologically relevant conditions remains challenging due to their heterogeneity, instability, and the requirements of sample preparation. Advantages of using neutron diffraction and contrast matching to characterize biomaterials are highlighted in this article. We have applied these and complementary techniques to search for nanocrystals within clusters of calcium phosphate sequestered by bovine phosphopeptides, derived from osteopontin or casein. The neutron diffraction patterns show broad features that could be consistent with hexagonal hydroxyapatite crystallites smaller than 18.9 Å. Such nanocrystallites are, however, undetected by the complementary X-ray and FTIR data, collected on the same samples. The absence of a distinct diffraction pattern from the nanoclusters supports the generally accepted amorphous calcium phosphate structure of the mineral core

Biologically induced phosphorus precipitation in aerobic granular sludge process

Aerobic granular sludge is a promising process for nutrient removal in wastewater treatment. In this work, for the first time, biologically induced precipitation of phosphorus as hydroxyl-apatite (Ca5(PO4)3(OH)) in the core of granules is demonstrated by direct spectral and optical analysis: Raman spectroscopy, Energy dispersive X-ray (EDX) coupled with Scanning Electron Microscopy (SEM), and X-ray diffraction analysis are performed simultaneously on aerobic granules cultivated in a batch airlift reactor for 500 days. Results reveal the presence of mineral clusters in the core of granules, concentrating all the calcium and considerable amounts of phosphorus. Hydroxyapatite appears as the major mineral, whereas other minor minerals could be transiently produced but not appreciably accumulated. Biologically induced precipitation was responsible for 45% of the overall P removal in the operating conditions tested, with pH varying from 7.8 to 8.8. Major factors influencing this phenomenon (pH, anaerobic phosphate release, nitrification denitrification) need to be investigated as it is an interesting way to immobilize phosphorus in a stable and valuable product

Hydrochlorothiazide reduces urinary calcium excretion in a child with Lowe syndrome.

There is a growing recognition that children with Lowe syndrome are at risk of nephrocalcinosis and nephrolithiasis from hypercalciuria. Increased fluid intake and correction of metabolic acidosis have remained the focus for intervention but are not always successful. Thiazide diuretics, which reduce urinary calcium excretion, have not been used in these children, due to concerns that (i) they may not work as a result of the underlying tubular abnormalities and (ii) their risk may outweigh the potential benefits they have to offer. Herein we report a child with Lowe syndrome who was successfully treated with thiazides in managing his hypercalciuria

Efficacy of the Biomaterials 3 wt%-nanostrontium-hydroxyapatite-enhanced Calcium Phosphate Cement (nanoSr-CPC) and nanoSr-CPC-incorporated Simvastatin-loaded Poly(lactic-co-glycolic-acid) Microspheres in Osteogenesis Improvement

Aims The purpose of this multi-phase explorative in vivo animal/surgical and in vitro multi-test experimental study was to (1) create a 3 wt%-nanostrontium hydroxyapatite-enhanced calcium phosphate cement (Sr-HA/CPC) for increasing bone formation and (2) creating a simvastatin-loaded poly(lactic-co-glycolic acid) (SIM-loaded PLGA) microspheres plus CPC composite (SIM-loaded PLGA + nanostrontium-CPC). The third goal was the extensive assessment of multiple in vitro and in vivo characteristics of the above experimental explorative products in vitro and in vivo (animal and surgical studies). Methods and results pertaining to Sr-HA/CPC Physical and chemical properties of the prepared Sr-HA/CPC were evaluated. MTT assay and alkaline phosphatase activities, and radiological and histological examinations of Sr-HA/CPC, CPC and negative control were compared. X-ray diffraction (XRD) indicated that crystallinity of the prepared cement increased by increasing the powder-to-liquid ratio. Incorporation of Sr-HA into CPC increased MTT assay (biocompatibility) and ALP activity (P \u3c 0.05). Histomorphometry showed greater bone formation after 4 weeks, after implantation of Sr-HA/CPC in 10 rats compared to implantations of CPC or empty defects in the same rats (n = 30, ANOVA P \u3c 0.05). Methods and results pertaining to SIM-loaded PLGA microspheres + nanostrontium-CPC composite After SEM assessment, the produced composite of microspheres and enhanced CPC were implanted for 8 weeks in 10 rabbits, along with positive and negative controls, enhanced CPC, and enhanced CPC plus SIM (n = 50). In the control group, only a small amount of bone had been regenerated (localized at the boundary of the defect); whereas, other groups showed new bone formation within and around the materials. A significant difference was found in the osteogenesis induced by the groups sham control (16.96 ± 1.01), bone materials (32.28 ± 4.03), nanostrontium-CPC (24.84 ± 2.6), nanostrontium-CPC-simvastatin (40.12 ± 3.29), and SIM-loaded PLGA + nanostrontium-CPC (44.8 ± 6.45) (ANOVA P \u3c 0.001). All the pairwise comparisons were significant (Tukey P \u3c 0.01), except that of nanostrontium-CPC-simvastatin and SIM-loaded PLGA + nanostrontium-CPC. This confirmed the efficacy of the SIM-loaded PLGA + nanostrontium-CPC composite, and its superiority over all materials except SIM-containing nanostrontium-CPC

Is non-buffered DMEM solution a suitable medium for in vitro bioactivity tests?

Several laboratories had tested bioactivity of the materials in commercially available solution DMEM (Dulbecco's Modified Eagle's Medium) that is normally used for cultivation of cell cultures. The objective of this work was to find out whether it is possible to replace TRIS-buffered SBF currently used for bioactivity tests with the non-buffered DMEM solution. To understand the role of the organic part of the DMEM solution in the process of crystallization, we have prepared non-buffered solution simulating only its inorganic part (identified as I-solution). It was found that under static-dynamic test conditions calcite (CaCO3) and the amorphous phase of calcium phosphate (ACP) formed on the surface of the glass-ceramic (45S5 bioactive glass based) scaffold exposed to both solutions. Additionally, halite (NaCl) formed at the beginning of exposure to DMEM. Hydroxyapatite phase was not detected on the surface in either non-buffered solution. Organic components contained in the DMEM solution failed to prevent formation of crystalline phases. The present results indicate that it is not recommendable to use DMEM for bioactivity tests of glass-ceramic materials due to its low concentration of Ca2+ ions, high concentration of HCO 3- ions and the necessity to maintain sterile environment during the test. © 2014 the Partner Organisations

In vitro analysis of urinary stone composition in dual-energy computed tomography

Purpose: Dual energy computed tomography (DECT) is a new method of computed tomography (CT) imaging, allowing the assessment of not only the object's morphology, but also its composition. The aim of the study was to evaluate the potential of in vitro DECT evaluation of urinary stones' chemical composition. Material and methods: Six samples of surgically removed renal stones were scanned using DECT and analyzed by scanner vendor software. Uric acid stones were marked red and calcium stones white by the software. The real composition of the stones was finally verified using physicochemical laboratory analysis. Results: In 5 out of 6 samples, the composition of stones in DECT (3 samples identified as uric acid and 2 samples as calcium) was consistent with the physicochemical analysis (3 samples identified as uric acid, 1 as calcium phosphate, 1 as calcium oxalate). In DECT it was not possible to determine more precisely the type of calcium compounds (calcium phosphate vs. calcium oxalate) as established in the physicochemical analysis. In one stone identified in physicochemical analysis as uric acid, DECT detected a composite layered structure containing both uric acid and calcium compounds. Conclusions: DECT allows uric acid to be distinguished from calcium urinary tract stones, which is crucial in the choice of appropriate therapy. Using the available hardware and software, it was not possible to more accurately distinguish types of calcified stones. Evaluation of the stone type in DECT may be limited in the case of mixed chemical composition

A Precision Medicine Approach Uncovers a Unique Signature of Neutrophils in Patients With Brushite Kidney Stones

Introduction: We have previously found that papillary histopathology differs greatly between calcium oxalate and brushite stone formers (SF); the latter have much more papillary mineral deposition, tubular cell injury, and tissue fibrosis. Methods: In this study, we applied unbiased orthogonal omics approaches on biopsied renal papillae and extracted stones from patients with brushite or calcium oxalate (CaOx) stones. Our goal was to discover stone type-specific molecular signatures to advance our understanding of the underlying pathogenesis. Results: Brushite SF did not differ from CaOx SF with respect to metabolic risk factors for stones but did exhibit increased tubule plugging in their papillae. Brushite SF had upregulation of inflammatory pathways in papillary tissue and increased neutrophil markers in stone matrix compared with those with CaOx stones. Large-scale 3-dimensional tissue cytometry on renal papillary biopsies showed an increase in the number and density of neutrophils in the papillae of patients with brushite versus CaOx, thereby linking the observed inflammatory signatures to the neutrophils in the tissue. To explain how neutrophil proteins appear in the stone matrix, we measured neutrophil extracellular trap (NET) formation-NETosis-and found it significantly increased in the papillae of patients with brushite stones compared with CaOx stones. Conclusion: We show that increased neutrophil infiltration and NETosis is an unrecognized factor that differentiates brushite and CaOx SF and may explain the markedly increased scarring and inflammation seen in the papillae of patients with brushite stones. Given the increasing prevalence of brushite stones, the role of neutrophil activation in brushite stone formation requires further study

Time-resolved Raman spectroscopy for in situ planetary mineralogy

Planetary mineralogy can be revealed through a variety of remote sensing and in situ investigations that precede any plans for eventual sample return. We briefly review those techniques and focus on the capabilities for on-surface in situ examination of Mars, Venus, the Moon, asteroids, and other bodies. Over the past decade, Raman spectroscopy has continued to develop as a prime candidate for the next generation of in situ planetary instruments, as it provides definitive structural and compositional information of minerals in their natural geological context. Traditional continuous-wave Raman spectroscopy using a green laser suffers from fluorescence interference, which can be large (sometimes saturating the detector), particularly in altered minerals, which are of the greatest geophysical interest. Taking advantage of the fact that fluorescence occurs at a later time than the instantaneous Raman signal, we have developed a time-resolved Raman spectrometer that uses a streak camera and pulsed miniature microchip laser to provide picosecond time resolution. Our ability to observe the complete time evolution of Raman and fluorescence spectra in minerals makes this technique ideal for exploration of diverse planetary environments, some of which are expected to contain strong, if not overwhelming, fluorescence signatures. We discuss performance capability and present time-resolved pulsed Raman spectra collected from several highly fluorescent and Mars-relevant minerals. In particular, we have found that conventional Raman spectra from fine grained clays, sulfates, and phosphates exhibited large fluorescent signatures, but high quality spectra could be obtained using our time-resolved approach