Surface Coating of NiTi Shape Memory Alloys with Calcium Phosphates by Dip-coating or Plasma-spraying-biological Characterization Examined by in vitro Testing Methods

The influence of different surface coatings of NiTi shape memory allays was examined using in vitro testing methods. Plates of superelastic nickel-titanium shape memory allay （ NiTi ） were coated with calcium phosphates （ hydroxyapatite ） by high-temperature plasma-spraying or by dip-coating. The biocompatibility was tested in vitro by cultivation of isolated human granulocytes and whole blood cells. As substrates, pure NiTi, plasma-spray-coated NiTi and dip-coated NiTi were used. Isolated granulocytes showed an increased adhesion to both calcium phosphate-coated NiTi samples. Compared to non-coated NiTi or dip-coated NiTi, the number of dead granulocytes adherent to plasma-sprayed surfaces was significantly increased （ p 〈 0.01 ）. Whether the d/f- ferences in apoptosis of granulocytes on dip-coated vs plasma-sprayed coatings observed are due to differences in material surface morphologies has to be analyzed in further studies. Because of the cellular interactions with the coating layers, h is likely that the results obtained are not caused by the underlying NiTi but due to the coating itself.

Injectable bone cements:What benefits the combination of calcium phosphates and bioactive glasses could bring?

Out of the wide range of calcium phosphate(CaP)biomaterials,calcium phosphate bone cements(CPCs)have attracted increased attention since their discovery in the 1980s due to their valuable properties such as bioactivity,osteoconductivity,injectability,hardening ability through a low-temperature setting reaction and moldability.Thereafter numerous researches have been performed to enhance the properties of CPCs.Nonetheless,low mechanical performance of CPCs limits their clinical application in load bearing regions of bone.Also,the in vivo resorption and replacement of CPC with new bone tissue is still controversial,thus further improvements of high clinical importance are required.Bioactive glasses(BGs)are biocompatible and able to bond to bone,stimulating new bone growth while dissolving over time.In the last decades extensive research has been performed analyzing the role of BGs in combination with different CaPs.Thus,the focal point of this review paper is to summarize the available research data on how injectable CPC properties could be improved or affected by the addition of BG as a secondary powder phase.It was found that despite the variances of setting time and compressive strength results,desirable injectable properties of bone cements can be achieved by the inclusion of BGs into CPCs.The published data also revealed that the degradation rate of CPCs is significantly improved by BG addition.Moreover,the presence of BG in CPCs improves the in vitro osteogenic differentiation and cell response as well as the tissue-material interaction in vivo.

Nanostructured Materials of Calcium Phosphates and Calcium Silicates： Synthesis, Properties and Applications

Calcium phosphates are a family of compounds with different chemical compositions, structures and properties containing calcium ions and functional groups of orthophosphate （ pO34- ）, metaphosphate （ PO3- ） or pyrophosphate （ P2O4-7 ） and sometimes hydrogen or hydroxide ions. Calcium phosphates can be widely found in nature as well as in hard tissues （bone and tooth） of the vertebrate. Owing to similar chemical composition and structure to the main inorganic constituents of bone and tooth, calcium phosphate-based materials are promising biomaterials with high biocompatibility, and have been investigated for applications in various biomedical areas. Calcium silicate-based materials have attracted much attention on their potential applications in various biomedical fields such as bone de- fect repair and drug delivery. In recent years, this research group has been focusing on the research in this exciting and rapidly evolving research field, and has published many papers. This article will provide a brief review on our main research work on the synthesis, characterization, properties and applications of nanostructured materials of calcium phosphates and calcium silicates. Finally, future perspectives and challenges for the research and applica- tions of nanostructured materials of calcium phosphates and calcium silicates are discussed.

Optimization by the Taguchi Method of a Robust Synthesis Protocol of Calcium Carbonate Phosphate

The experimental processes are difficult to model by physical laws, because a multitude of factors can intervene simultaneously and are responsible for their instabilities and their random variations. Two types of factors are to be considered;those that are easy to manipulate according to the objectives, and those that can vary randomly (uncontrollable factors). These could eventually divert the system from the desired target. It is, therefore, important to implement a system that is insensitive to fluctuations in factors that are difficult to control. The aim of this study is to optimize the synthesis of an apatitic calcium carbonate phosphate characterized with a Ca/P ratio equal to 1.61 by using the experimental design method based on the Taguchi method. In this process, five factors are considered and must be configured to achieve the previously defined objective. The temperature is a very important factor in the process, but difficult to control experimentally, so considered to be a problem factor (noise factor), forcing us to build a robust system that is insensitive to the last one. Therefore, a much simpler model to study the robustness of a synthetic solution with respect to temperature is developed. We have tried to parameterize all the factors considered in the process within a wide interval of temperature variation (60˚C - 90˚C). Temperature changes are no longer considered as a problem for apatitic calcium carbonate phosphate synthesis. In this finding, the proposed mathematical model is linear and efficient with very satisfactory statistical indicators. In addition, several simple solutions for the synthesis of carbonate phosphate are proposed with a Ca/P ratio equal to 1.61.

Laparoscopic treatment of a calcium fluorophosphate stone within a seminal vesicle cyst

Stones in the seminal vesicles are extremely rare. We present a 62-year-old patient with a stone within a seminal vesicle cyst, who was cured by laparoscopic treatment. The operative time was 80 rnin, and the estimated blood loss was 90 mL. Scanning electron microscope examination of the stone showed a compact crystal image externally and sparse spherical crystal structure in kernel. Composition of the stone was calcium fluorophosphate on X-ray diffractometer. The follow-up time was 15 months with no recurrence of cyst or stone. To our knowledge, this case is the first to describe laparoscopic removal of a stone within a seminal vesicle cyst, and the first to describe calcium fluorophosphate as the composition of seminal vesicle stones. （Asian JAndro12008 Mar; 10： 337-340）

Calcium Phosphate Biomaterials: An Update

Current calcium phosphate （ CaP ） biomaterials for bone repair, substitution, augmentation and regeneration include hydroxyapatite （ HA ） from synthetic or biologic origin, beta-tricaicium phosphate （ β- TCP ）, biphasic calcium phosphate （BCP）, and are available as granules, porous blocks, components of compashes （CaP/pollymer） cements, and as coatings on orthopedic and dental implants. Experimental calcium phosphate biomaterials include CO3^- and F-substituted apatites, Mg-and Zn-substituted β-TCP, calcium phosphate glasses, This paper is a brief review of the different types of CaP biomaterials and their properties such as bioactivity , osteoconductivity , osteoinductivity.

Augmentation of Pedicle Screw Fixation with Calcium Phosphate Cement

To determine whether a biodegradable calcium phosphate cement(CPC) provides significant augmentation of pedicle screw fixation or not,an in vitro biomechanical study was carried out to evaluate the biomechanical effect of CPC in the restoration and augmentation of pedicle screw fixation.Axial pullout test and cyclic bending resistance test were employed in the experiment,and polymethylmethacrylate (PMMA) was chosen as control.The results demonstrate that the pullout strengths following CPC restoration and augmentation are 74% greater on an average than those of the control group,but less than those of PMMA restoration group and augmentation group respectively (increased by 126% versus control).In cyclic bending resistance test,the CPC augmented screws are found to withstand a greater number of cycles or greater loading with less displacement before loosening,but the augmentation effect of PMMA is greater than that of CPC.

Effects of quaternary ammonium chain length on the antibacterial and remineralizing effects of a calcium phosphate nanocomposite

Composites containing nanoparticles of amorphous calcium phosphate （NACP） remineralize tooth lesions and inhibit caries. A recent study synthesized quaternary ammonium methacrylates （QAMs） with chain lengths （CLs） of 3-18 and determined their effects on a bonding agent. This study aimed to incorporate these QAMs into NACP nanocomposites for the first time to simultaneously endow the material with antibacterial and remineralizing capabilities and to investigate the effects of the CL on the mechanical and biofilm properties. Five QAMs were synthesized： DMAPM （CL3）, DMAHM （CL6）, DMADDM （CL12）, DMAHDM （CL16）, and DMAODM （CL18）. Each QAM was incorporated into a composite containing 20% NACP and 50% glass fillers. A dental plaque microcosm biofilm model was used to evaluate the antibacterial activity. The flexural strength and elastic modulus of nanocomposites with QAMs matched those of a commercial control composite （n = 6; P 〉 0.1）. Increasing the CL from 3 to 16 greatly enhanced the antibacterial activity of the NACP nanocomposite （P 〈 0.05）; further increasing the CL to 18 decreased the antibacterial potency. The NACP nanocomposite with a CL of 16 exhibited biofilm metabolic activity and acid production that were 10-fold lesser than those of the control composite. The NACP nanocomposite with a CL of 16 produced 2-log decreases in the colony-forming units （CFU） of total microorganisms, total streptococci, and mutans streptococci. In conclusion, QAMs with CLs of 3-18 were synthesized and incorporated into an NACP nanocomposite for the first time to simultaneously endow the material with antibacterial and remineralization capabilities. Increasing the C/reduced the metabolic activity and acid production of biofilms and caused a 2-log decrease in CFU without compromising the mechanical properties. Nanocomposites exhibiting strong anti-biofilm activity, remineralization effects, and mechanical properties are promising materials for tooth restorations that inhibit caries.

One-year water-ageing of calcium phosphate composite containing nano-silver and quaternary ammonium to inhibit biofilms

Dental composites are commonly used restorative materials; however, secondary caries due to biofilm acids remains a major problem. The objectives of this study were （1） to develop a composite containing quaternary ammonium dimethacrylate （QADM）, nanoparticles of silver （NAg）, and nanoparticles of amorphous calcium phosphate （NACP）, and （2） to conduct the first investigation of the mechanical properties, biofilm response and acid production vs water-ageing time from 1 day to 12 months. A 4 x 5 design was utilized, with four composites （NACP-QADM composite, NACP-NAg composite, NACP-QADM-NAg composite, and a commercial control composite）, and five water-ageing time periods （1 day, and 3, 6, 9, and 12 months）. After each water- ageing period, the mechanical properties of the resins were measured in a three-point flexure, and antibacterial properties were tested via a dental plaque biofilm model using human saliva as an inoculum. After 12 months of water-ageing, NACP-QADM- NAg had a flexural strength and elastic modulus matching those of the commercial control （P〉 0.1）. Incorporation of QADM or NAg into the NACP composite greatly reduced biofilm viability, metabolic activity and acid production. A composite containing both QADM and NAg possessed a stronger antibacterial capability than one with QADM or NAg alone （P〈0.05）. The anti-biofilm activity was maintained after 12 months of water-ageing and showed no significant decrease with increasing time （P〉0.1）. In conclusion, the NACP-QADM-NAg composite decreased biofilm viability and lactic acid production, while matching the load- bearing capability of a commercial composite. There was no decrease in its antibacterial properties after 1 year of water-ageing. The durable antibacterial and mechanical properties indicate that NACP-QADM-NAg composites may be useful in dental restorations to combat caries.

Effect of humic substances on the precipitation of calcium phosphate

For phosphorus （P） recovery from wastewater, the effect of humic substances （HS） on the precipitation of calcium phosphate was studied. Batch experiments of calcium phosphate precipitation were undertaken with synthetic water that contained 20 mg/L phosphate （as P） and 20 mg/L HS （as dissolved organic carbon, DOC） at a constant pH value in the range of 8.0-10.0. The concentration variations of phosphate, calcium （Ca） and HS were measured in the precipitation process; the crystalline state and compositions of the precipitates were analysed by powder X-ray diffraction （XRD） and chemical methods, respectively. It showed that at solution pH 8.0, the precipitation rate and removal efficiency of phosphate were greatly reduced by HS, but at solution pH ≥9.0, the effect of HS was very small. The Ca consumption for the precipitation of phosphate increased when HS was added; HS was also removed from solution with the precipitation of calcium phosphate. At solution pH 8.0 and HS concentrations ≤3.5 mg/L, and at pH ≥ 9.0 and HS concentrations ≤ 10 mg/L, the final precipitates were proved to be hydroxyapatite （HAP） by XRD. The increases of solution pH value and initial Ca/P ratio helped reduce the influence of HS on the precipitation of phosphate.

Calcium phosphate cements for bone engineering and their biological properties

Calcium phosphate cements （CPCs） are frequently used to repair bone defects. Since their discovery in the 1980s, extensive research has been conducted to improve their properties, and emerging evidence supports their increased application in bone tissue engineering. Much effort has been made to enhance the biological performance of CPCs, including their biocompatibility, osteoconductivity, osteoinductivity, biodegradability, bioactivity, and interactions with cells. This review article focuses on the major recent developments in CPCs, including 3D printing, injectability, stem cell delivery, growth factor and drug delivery, and pre- vascularization of CPC scaffolds via co-culture and tri-culture techniques to enhance angiogenesis and osteogenesis.

Surface characterization and corrosion behavior of calcium phosphate(Ca-P)base composite layer on Mg and its alloys using plasma electrolytic oxidation(PEO):A review

Magnesium has been known as an appropriate biological material on account of its good biocompatibility and biodegradability properties in addition to advantageous mechanical properties.Mg and its alloys are of poor corrosion resistance.Its high corrosion rate leads to its quick decomposition in the corrosive ambiance and as a result weakening its mechanical properties and before it is repaired,it will vanish.The corrosion and degradation rate must be controlled in the body to advance the usage of Mg and its alloys as implants.Different techniques have been utilized to boost biological properties.Plasma electrolytic oxidation(PEO)can provide porous and biocompatible coatings for implants among various techniques.Biodegradable implants are generally supposed to show enough corrosion resistance and mechanical integrity in the body environment.Much research has been carried out in order to produce PEO coatings containing calcium phosphate compounds.Calcium phosphates are really similar to bone mineral composition and present great biocompatibility.The present study deals with the usage of calcium phosphates as biocompatible coatings applied on Mg and its alloys to study the properties and control the corrosion rate.

Bone tissue engineering via nanostructured calcium phosphate biomaterials and stem cells

Tissue engineering is promising to meet the increasing need for bone regeneration. Nanostructured calcium phosphate （CAP） biomaterials/scaffolds are of special interest as they share chemical/crystallographic similarities to inorganic components of bone. Three applications of nano-CaP are discussed in this review： nanostructured calcium phosphate cement （CPC）; nano-CaP composites; and nano-CaP coatings. The interactions between stem cells and nano-CaP are highlighted, including cell attachment, orientation/ morphology, differentiation and in vivo bone regeneration. Several trends can be seen： （i） nano-CaP biomaterials support stem cell attachment/proliferation and induce osteogenic differentiation, in some cases even without osteogenic supplements; （ii） the influence of nano-CaP surface patterns on cell alignment is not prominent due to non-uniform distribution of nano-crystals; （iii） nano-CaP can achieve better bone regeneration than conventional CaP biomaterials; （iv） combining stem cells with nano-CaP accelerates bone regeneration, the effect of which can be further enhanced by growth factors; and （v） cell microencapsulation in nano-CaP scaffolds is promising for bone tissue engineering. These understandings would help researchers to further uncover the underlying mechanisms and interactions in nano-CaP stem cell constructs in vitro and in vivo, tailor nano-CaP composite construct design and stem cell type selection to enhance cell function and bone regeneration, and translate laboratory findings to clinical treatments.

Novel rechargeable calcium phosphate nanoparticle-containing orthodontic cement

White spot lesions （WSLs）, due to enamel demineralization, occur frequently in orthodontic treatment. We recently developed a novel rechargeable dental composite containing nanoparticles of amorphous calcium phosphate （NACP） with long-term calcium （Ca） and phosphate （P） ion release and caries-inhibiting capability. The objectives of this study were to develop the first NACP- rechargeable orthodontic cement and investigate the effects of recharge duration and frequency on the efficacy of ion re-release. The rechargeable cement consisted of pyromellitic glycerol dimethacrylate （PMGDM） and ethoxylated bisphenol A dimethacrylate （EBPADMA）. NACP was mixed into the resin at 40% by mass. Specimens were tested for orthodontic bracket shear bond strength （SBS） to enamel, Ca and P ion initial release, recharge and re-release. The new orthodontic cement exhibited an SBS similar to commercial orthodontic cement without CaP release （P〉 0.1）. Specimens after one recharge treatment （e.g., 1 min immersion in recharge solution repeating three times in one day, referred to as ＂1 min 3 times＂） exhibited a substantial and continuous re-release of Ca and P ions for 14 days without further recharge. The ion re-release did not decrease with increasing the number of recharge/re-release cycles （P〉 0.1）. The ion re-release concentrations at 14 days versus various recharge treatments were as follows： 1 min 3 times〉3 min 2 times〉 1 min 2 times〉6 min 1 time〉3 min 1 time〉 1 min 1 time. In conclusion, although previous studies have shown that NACP nanocomposite remineralized tooth lesions and inhibited caries, the present study developed the first orthodontic cement with Ca and P ion recharge and long-term release capability. This NACP-rechargeable orthodontic cement is a promising therapy to inhibit enamel demineralization and WSLs around orthodontic brackets.

Preparation of Laminin-apatite-polymer Composites Using Metastable Calcium Phosphate Solutions

A synthetic polymer with a laminin-apatite composite layer on its surface would be useful as a percutaneous device. The preparation of such a composite was attempted in the present study using poly（ ethylene terephthalate ） （PET） and polyethylene （PE） as the synthetic polymer. PET and PE plates and those pretreated with an oxygen plasma were alternately dipped in calcium and phosphate ion solutions, and then immersed in a metastable calcium phosphate solution supplemented with laminin （ LCP solution ）. The PET and PE plates pretreated with an oxygen plasma formed a uniform and continuous layer of a laminin-apatite composite on their surfaces. In contrast, the PET and PE plates that had not been pretreated with an oxygen plasma did not form a continuous layer of a laminin-apatite composite on their surfaces. The hydrophilic functional groups on the PET and PE surfaces introduced by the plasma treatment were responsible for the successful laminin-apatite coruposite coating.

Microwave assisted synthesis & properties of nano HA-TCP biphasic calcium phosphate

Biphasic calcium phosphate （BCP） nanopowders were synthesized by using microwave and non-microwave irradiation assisted processes. The synthesized powders were pressed under a pressure of 90 MPa, and then were sintered at 1000-1200℃ for 1 h. The mechanical properties of the samples were investigated. The formed phases and microstructures were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results showed that the synthesis time was shorter, along with a more homogeneous microstructure, when the microwave irradiation assisted method was applied. The compression strength and the Young＇s modulus of the samples synthesized with microwave irradiation were about 60 MPa and 3 GPa, but those of the samples synthesized without microwave irradiation were about 30 MPa and 2 GPa, respectively. XRD patterns of the microwave irradiation assisted and non-microwave irradiation assisted nanopowders showed the coexistence of hydroxyapatite （HA） and lricalcium phosphate （TCP） phases in the system.

Porous Calcium Phosphate Ceramic Scaffolds for Tissue Engineering

This study examined the biological response of two porous calcium phosphate ceramics, hydroxyapntite （ HA ） and hydroxyapaptite/β-tricalcium phosphate （ HA/β- TCP ） scaffolds. Three different cell types , a human osteoblastic cell line （ HOS ） , primary human osteoblasts （HOB） and human mesenehymal stem cells （MSCs）, were used to examine biocompatibility and osteoinductive capacity. The experimental results showed both materials were highly biocompatible and proliferation was significantly greater on pure HA （ P 〈 0.01 ）, with a peak in proliferation at day 7. Protein levels were significantly higher （ P 〈 0.05） than the control Thermanox（ TMX （ tm） ） for both test materials. Osteoinduction of MSCs was observed on both test materials, with cells seeded on HA/ β-TCP showing greater alkaline phosphatase activity compared to HA alone, indicating an enhancement in osteoinductive property. Both materials show good potential for use as tissue engineered scaffolds.

In Situ Laser Coating of Calcium Phosphate on TC4 Surface for Enhancing Bioactivity

Titanium alloy has been a successful implant material owing to its excellent ratio of strength to weight, toughness, and bio-inert oxide surface. Significant progress has been made in improving the bioactivity of titanium alloy by coating its oxide surface with calcium phosphates. In the present study, in situ coating was reported on Ti6Al4V（TC4） surface with calcium phosphate （Ca-P） bioceramics synthesized and synchronously cladded by laser beam. This coating was grown by first preplacing directly the raw powders, which contain 80% of CaHPO4 · 2H2O, 20% of CaCO3, and dram of rare earth （RE）, on the TC4 surfaces, and then exposing the surfaces to the laser beam with a power density of 12. 73-15.27 MW · m^-2 and a scanning velocity of 10.5 m/s. The resultant coating was characterized using scanning electron microscopy （SEM）, X-ray diffraction （XRD）, thermogravimetric analysis and Different-thermal Scanning （TG-DSC）, and Energy Dispersive X-ray Detection （EDX）. The results show that these laser ceramics include hydroxyapatite （HA）, tricalcium phosphate （TCP）, Ca2 P2 O7, and other Ca-P phases, and the interface between the coating and the TC4 substrate has tighter fixation, in which the chemical bonding is approved. These laser hybrid coatings are useful in enhancing the bioactivity of titanium alloy surfaces.

Comparison of the defluoridation efficiency of calcium phosphate and chitin in the exoskeleton of Antarctic krill

Calcium （Ca）, phosphorus （P）, and chitin are the main components of the exoskeleton of krill. Defluoridation of a solution of sodium fluoride （NaF） using calcium phosphate （Ca3（PO4）2） and chitin as defluoridation agents was studied. Orthogonal experiments were designed to find the optimum reaction conditions for defluoridation, to obtain the maximum defluoridation efficiency and fluoride removal capacity of calcium phosphate and chitin. At the same time, a comparison of the capacity of the two defluoridation agents was made. The results suggest that calcium phosphate has a far greater capability than chitin for the removal of fluoride （F） from water under similar reaction conditions. It is also suggested that Antarctic krill is likely to adsorb fluoride via compounds such as calcium phosphate, hydroxyapatite, and other compounds of Ca and P with the general form （Ca, X）x（PO4, HPO4, Y）y（OH, Z）z, in addition to chitin.

Calcium phosphate conversion technique:A versatile route to develop corrosion resistant hydroxyapatite coating over Mg/Mg alloys based implants

Globally,vast research interest is emerging towards the development of biodegradable orthopedic implants as it overcomes the toxicity exerted by non-degradable implants when fixed in the human body for a longer period.In this context,magnesium(Mg)plays a major role in the production of biodegradable implants owing to their characteristic degradation nature under the influence of body fluids.Also,Mg is one of the essential nutrients required to perform various metabolic activities by the human cells,and therefore,the degraded Mg products will be readily absorbed by the nearby tissues.Nevertheless,the higher corrosion rate in the biological environment is the primary downside of using Mg implants that liberate H2gas resulting in the formation of cavities.Further,in certain cases,Mg undergoes complete degradation before the healing of damaged bone tissue and cannot serve the purpose of providing mechanical support.So,many studies have been focused on the development of different strategies to improve the corrosion-resistant behavior of Mg according to the requirement.In this regard,the present review focused on the limitations of using pure Mg and Mg alloys for the fabrication of medical implants and how the calcium phosphate conversion coating alters the corrosive tendency through the formation of hydroxyapatite protective films for enhanced performance in medical implant applications.