scholarly journals Formation and Evolution of Nanoscale Calcium Phosphate Precursors Under Biomimetic Conditions

Author(s):  
ludovica epasto ◽  
tristan georges ◽  
albina selimovic ◽  
Jean-Michel Guigner ◽  
Thierry Azaïs ◽  
...  

Simulated body fluids that mimic human blood plasma are widespread media for in-vitro studies in an extensive array of research fields, from biomineralization to surface and corrosion sciences. We show that these solutions undergo dynamic nanoscopic conformational rearrangements on the timescale of minutes to hours, even though they are commonly considered stable or metastable. In particular, we find and characterize nanoscale inhomogeneities made of calcium phosphate (CaP) aggregates that emerge from homogeneous SBF within a few hours and evolve into prenucleation species (PNS) that act as precursors in CaP crystallization processes. These ionic clusters consist of about 2 nm large spherical building units that can aggregate into supra-structures with sizes of over 200 nm. We show that the residence times of phosphate ions in the PNS depend critically on the total PNS surface. These findings are particularly relevant for understanding non-classical crystallization phenomena, in which PNS are assumed to act as building blocks for the final crystal structure.<br>

2021 ◽  
Author(s):  
ludovica epasto ◽  
tristan georges ◽  
albina selimovic ◽  
Jean-Michel Guigner ◽  
Thierry Azaïs ◽  
...  

Simulated body fluids that mimic human blood plasma are widespread media for in-vitro studies in an extensive array of research fields, from biomineralization to surface and corrosion sciences. We show that these solutions undergo dynamic nanoscopic conformational rearrangements on the timescale of minutes to hours, even though they are commonly considered stable or metastable. In particular, we find and characterize nanoscale inhomogeneities made of calcium phosphate (CaP) aggregates that emerge from homogeneous SBF within a few hours and evolve into prenucleation species (PNS) that act as precursors in CaP crystallization processes. These ionic clusters consist of about 2 nm large spherical building units that can aggregate into supra-structures with sizes of over 200 nm. We show that the residence times of phosphate ions in the PNS depend critically on the total PNS surface. These findings are particularly relevant for understanding non-classical crystallization phenomena, in which PNS are assumed to act as building blocks for the final crystal structure.<br>


2009 ◽  
Vol 610-613 ◽  
pp. 1391-1394
Author(s):  
Hua De Zheng ◽  
Ying Jun Wang ◽  
Qiang Ma ◽  
Cheng Yun Ning ◽  
Xiao Feng Chen

In the present study, an Intelligent Multi-parameter Simulated Evaluation in vitro (IMSE system) was used to study the deposition properties of apatite formation on the surface of biphasic calcium phosphate porous ceramic (BCP) from static and dynamic r-SBF. Results showed that apatite formed on the surface of BCP from static and dynamic r-SBF differed between each other. In static r-SBF, ions were transferred by diffusion, which could not compensate the consuming of calcium ions, and mist apatite layer was formed on the surface of samples. But in the dynamic r-SBF, simulated fluid was adjusted precisely and flowed forcedly, the concentrations of ions were homogeneous; with the compensation of ions, calcium and phosphate were supersaturated, and the free energy of apatite formation was negative, bone-like apatite sheets were formed on the surface of samples.


2021 ◽  
pp. 39-48
Author(s):  
D.R. Khairutdinova ◽  
◽  
M.A. Goldberg ◽  
P.A. Krokhicheva ◽  
O.S. Antonova ◽  
...  

Cement materials have based on calcium sulfate were obtained, which have introduced up to 20 mol. % of phosphate groups to improve their cytocompatibility and solubility. It was found that during exposure of cement materials based on calcium sulfate, containing of 0, 5, 10 and 20 mol. % phosphate - groups, in model solutions SBF (Kokubo solution, simulating the composition of human blood plasma) and DPBS (Dulbecco's phosphate-buffered saline) in dynamics up to 28 days of were formation of a calcium-phosphate layer on the surface of the samples. At the same time, in SBF solution, the process of recrystallization of sulfate and phosphate phases occurs more pronounced than in DPBS solution. In vitro studies on the cell culture of the human osteosarcoma line MG-63, cement samples showed cytocompatibility with the presence of moderate surface matrix properties


1987 ◽  
Vol 110 ◽  
Author(s):  
Lisa M. Morris ◽  
Praphyilla K. Bajpai

AbstractCalcium phosphate collagen composites are currently being used to rebuild bone. Commercial collagen preparations have been claimed to he hvpo-antigenic but none are non-antigenic. The collagen in calcium phosphate collagen composites is eventually degraded to its component amino acids. Two thirds of collagen consists of glvcine, hvdroxvproline, and proline. Since both tricalcium phosphate (TCP) and collagen are resorbable and both can he utilized to form bone, incorporation of amino acids into TCP-amino acid composites should nrovide the building blocks for formation of new bone. Stich composites should also be non-antigenic. Previous work conducted with composites of amino acids with aluminum calcium phosphorous oxide (ALCAP) ceramics, has shown that these composites can be uised to repair traumatized bone in rats. In our study, experiments conducted with TCP cysteine, Ivsine, or proline composites showed that the composites, after setting to hardness, degrade slowly and can he molded into different froms. Dissolution studies were conducted with composites of TCP with each of the above amino acids in Tris-MCl buffer (PH 7.4) at 37°C in vitro. Experiments conducted with antibiotics showed that antibiotics such as penicillin and ervthromvcin can be incorporated into the TCP amino acid composite. Subcutaneous implants of TCP amino acid composites in rats showed that most of the TCP-proline composite was degraded bv day 4, TCP-lvsine composite he day 7, and TCP-cysteine composite by day 21. Our results suggest that TCP amino acid composites are biocomnatible and can he used to repair experimentally traumatized bone.


2004 ◽  
Vol 1 (1) ◽  
pp. 17-22 ◽  
Author(s):  
Hyun-Min Kim ◽  
Teruyuki Himeno ◽  
Masakazu Kawashita ◽  
Tadashi Kokubo ◽  
Takashi Nakamura

The mechanism of biomineralization of bone-like apatite on synthetic hydroxyapatite (HA) has been investigated in vitro , in which the HA surface was surveyed as a function of soaking time in simulated body fluid (SBF). In terms of surface structure by transmission electron microscopy with energy-dispersive X-ray spectrometry, the HA whose Ca/P atomic ratio was 1.67 revealed three different characteristic soaking periods in SBF, i.e. the first soaking period, in which the HA surface increased the Ca/P ratio up to 1.83 to form an amorphous phase of Ca-rich calcium phosphate; the second soaking period, in which the HA surface decreased the Ca/P ratio up to 1.47 to form an amorphous phase of Ca-poor calcium phosphate; and the third soaking period, in which the HA surface gradually increased the Ca/P ratio up to 1.65 to eventually produce the bone-like nano-cerystallites of apatite, which grew forming complex crystal assemblies with a further increase in immersion time. Analysis using electrophoresis spectroscopy indicated that, immediately after immersion in SBF, the HA revealed a highly negative surface potential, which increased to reach a maximum positive value in the first soaking period. The surface potential then decreased to again reach a negative value in the second soaking period and thereafter converge to a constant negative value in the third soaking period. This implies that the HA induces biomineralization of apatite by smartly varying its surface potential to trigger an electrostatic interaction, first with positive calcium ions and second with negative phosphate ions in the SBF.


2017 ◽  
Vol 10 (17) ◽  
pp. 174
Author(s):  
Sri Angky Soekanto ◽  
Gadiacanaparimita Ghrena Duhita ◽  
Endang Winiati Bachtiar ◽  
Muhamad Sahlan

 Objective: The aim of this study is to analyze the amount of calcium and phosphate ion released by casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), which supports the remineralization and the effectiveness of propolis wax in suppressing the mass formation of Streptococcus mutans biofilm on caries-free subjects and to observe if these two active components are effective when combined into one substance and placed inside sugar-free chewing gum.Methods: Twenty-five samples of caries-free saliva before and after the mastication simulation (five concentrations of chewing gum) in vitro were observed to check for release of calcium and phosphate ions along with a biofilm assay. The release of calcium ions was detected using AAS, the release of phosphate ions was detected using spectrophotometry ultraviolet-visible, and the biofilm assay was detected using a crystal violet 96-well plate ELISA and was evaluated with an ELISA reader.Result: Chewing gum with a concentration of 0% prop + 5% CPP-ACP showed the highest release level of calcium ions (p<0.05) and phosphate ions (p>0.05) and is significant in suppressing the mass formation of the S. mutans biofilm (p<0.05).Conclusions: Mastication simulation of CPP-ACP-Propolis chewing gum can increase calcium and phosphate ion levels in caries-free saliva and decrease S. mutans biofilm mass formation; this can support remineralization and becomes a dental caries prevention alternative.


2020 ◽  
Vol 16 ◽  
Author(s):  
Benedetta Bocchini ◽  
Bruna Goldani ◽  
Fernanda S.S. Sousa ◽  
Paloma T. Birmann ◽  
Cesar A. Brüning ◽  
...  

Background: Quinoline derivatives have been attracted much attention in drug discovery and synthetic derivatives of these scaffolds present a range of pharmacological activities. Therefore, organoselenium compounds are valuable scaffolds in organic synthesis because their pharmacological activities and their use as versatile building blocks for regio-, chemio-and stereoselective reactions. Thus, the synthesis of selenium-containing quinolines has great significance, and their applicability range from simple antioxidant agents, to selective DNA-binding and photocleaving agents. Objective: In the present study we describe the synthesis and antioxidant activity in vitro of new 7-chloroN(arylselanyl)quinolin-4-amines 5 by the reaction of 4,7-dichloroquinoline 4 with (arylselanyl)-amines 3. Methods: For the synthesis of 7-chloro-N(arylselanyl)quinolin-4-amines 5, we performed the reaction of (arylselanyl)- amines 3 with 4,7-dichloroquinoline 4 in the presence of Et3N at 120 °C in a sealed tube. The antioxidant activities of the compounds 5 were evaluated by the following in vitro assays: 2,2- diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, 2,2-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), ferric ion reducing antioxidant power (FRAP), nitric oxide (NO) scavenging and superoxide dismutase-like activity (SOD-Like). Results: 7-Chloro-N(arylselanyl)quinolin-4-amines 5a-d has been synthesized in yields ranging from 68% to 82% by the reaction of 4,7-dichloroquinoline 4 with arylselanyl-amines 3a-d using Et3N as base, at 120 °C, in a sealed tube for 24 hours and tolerates different substituents, such as -OMe and -Cl, in the arylselanyl moiety. The obtained compounds 5a-d presented significant results with respect to the antioxidant potential, which had effect in the tests of inhibition of radical’s DPPH, ABTS+ and NO, as well as in the test that evaluates the capacity (FRAP) and in the superoxide dismutase-like activity assay (SOD-Like). It is worth mentioning that 7-chloro-N(arylselanyl)quinolin-4-amine 5b presented excellent results, demonstrating a better antioxidant capacity when compared to the others. Conclusion: According to the obtained results 7-chloro-N(arylselanyl)quinolin-4-amines 5 were synthesized in good yields by the reaction of 4,7-dichloroquinoline with arylselanyl-amines and tolerates different substituents in the arylselanyl moiety. The tested compounds presented significant antioxidant potential in the tests of inhibition of DPPH, ABTS+ and NO radicals, as well as in the FRAP and superoxide dismutase-like activity assays (SOD-Like).


2019 ◽  
Vol 12 (1) ◽  
pp. 27-49 ◽  
Author(s):  
Shahinda S.R. Alsayed ◽  
Chau C. Beh ◽  
Neil R. Foster ◽  
Alan D. Payne ◽  
Yu Yu ◽  
...  

Background:Mycolic acids (MAs) are the characteristic, integral building blocks for the mycomembrane belonging to the insidious bacterial pathogen Mycobacterium tuberculosis (M.tb). These C60-C90 long α-alkyl-β-hydroxylated fatty acids provide protection to the tubercle bacilli against the outside threats, thus allowing its survival, virulence and resistance to the current antibacterial agents. In the post-genomic era, progress has been made towards understanding the crucial enzymatic machineries involved in the biosynthesis of MAs in M.tb. However, gaps still remain in the exact role of the phosphorylation and dephosphorylation of regulatory mechanisms within these systems. To date, a total of 11 serine-threonine protein kinases (STPKs) are found in M.tb. Most enzymes implicated in the MAs synthesis were found to be phosphorylated in vitro and/or in vivo. For instance, phosphorylation of KasA, KasB, mtFabH, InhA, MabA, and FadD32 downregulated their enzymatic activity, while phosphorylation of VirS increased its enzymatic activity. These observations suggest that the kinases and phosphatases system could play a role in M.tb adaptive responses and survival mechanisms in the human host. As the mycobacterial STPKs do not share a high sequence homology to the human’s, there have been some early drug discovery efforts towards developing potent and selective inhibitors.Objective:Recent updates to the kinases and phosphatases involved in the regulation of MAs biosynthesis will be presented in this mini-review, including their known small molecule inhibitors.Conclusion:Mycobacterial kinases and phosphatases involved in the MAs regulation may serve as a useful avenue for antitubercular therapy.


2015 ◽  
Vol 23 (1) ◽  
pp. 1-14
Author(s):  
Sudirman Sahid ◽  
◽  
Nor Shahida Kader Bashah ◽  
Salina Sabudin ◽  
◽  
...  

2006 ◽  
Vol 69 (12) ◽  
pp. 976-982 ◽  
Author(s):  
Nenad Ignjatović ◽  
Petar Ninkov ◽  
Vesna Kojić ◽  
Miloš Bokurov ◽  
Vladimir Srdić ◽  
...  

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