Synthesis of prolonged-release drugs for osteoplasty that are based on chemically modified calcium phosphates

In order to use hydroxyapatite and other biocompatible calcium phosphates as carriers for local prolonged-release drug, it is necessary to have an active component capable of retaining the preparation deposited onto the carrier surface for a long time (at least, for a few days). The grafting of the layer of active functional groups onto the carrier surface is employed to affect kinetic adsorption-desorption characteristics of calcium phosphates. The method of chemical modification of biocompatible calcium phosphates that uses B(OC₄H₉)₃, SiCl₄, POCl₃, PCl₅, and SnCl₄ is developed. The effect of the modification of calcium phosphate’s surface on the kinetics of hydrolytic desorption of octadecylamine and tetraethylenepentamine modeling the hydrophobic and hydrophilic drugs, respectively, as well as gentamicin, an antibiotic that is widely used in clinical practice to prevent and cure inflammation processes upon the damage of bony tissue, is studied. It is shown that the rate of desorption of these substances from calcium phosphates into the aqueous phase is significantly retarded when the carrier surface is preliminarily modified. By means of ESR and IR Fourier spectroscopy, the interaction of octadecylamine and tetraethylenepentamine with calcium phosphate’s surface is investigated. A conclusion about the existence of two mechanisms of adsorption of amines on modified calcium phosphates is drawn. The procedure for the preparation of biocompatible calcium phosphates with hemisorbed gentamicin is developed.     

磷酸锆催化甘油气相脱水制备丙烯醛

以沉淀法、水热合成法和浸渍法制备了磷酸锆催化剂,通过X射线衍射、热重分析、氮气物理吸附、红外光谱和Hammett指示剂法对催化剂进行了表征,并将该催化剂用于甘油气相脱水反应.研究表明,由沉淀法得到的磷酸锆经过400℃焙烧后能达到最佳催化活性,在温和条件下,甘油可完全转化,丙烯醛选择性为81%,反应24h内催化剂失活不明显.不同方法制备的磷酸锆其结构和表面酸性显著不同,催化剂表面酸性对催化剂活性、丙烯醛选择性和催化剂的寿命均有较大影响.     

Modification and intercalation of layered zirconium phosphates: a solid‐state NMR monitoring

Several layered zirconium phosphates treated with Zr(IV) ions, modified by monomethoxy‐polyethyleneglycol‐monophosphate and intercalated with doxorubicin hydrochloride have been studied by solid‐state MAS NMR techniques. The organic components of the phosphates have been characterized by the ¹³C{¹H} CP MAS NMR spectra compared with those of initial compounds. The multinuclear NMR monitoring has provided to establish structure and covalent attachment of organic/inorganic moieties to the surface and interlayer spaces of the phosphates. The MAS NMR experiments including kinetics of proton‐phosphorus cross polarization have resulted in an unusual structure of zirconium phosphate 6 combining decoration of the phosphate surface by polymer units and their partial intercalation into the interlayer space. Copyright © 2016 John Wiley & Sons, Ltd.     

A comparative study on textural characterization: cation-exchange and sorption properties of crystalline alpha-zirconium(IV), tin(IV), and titanium(IV) phosphates

Tetravalent metal phosphates (M=Zr, Ti, and Sn) were prepared and characterized by XRD, surface properties, and TG-DTA. The cation exchange and sorption behavior of these metal phosphates toward transition metal ions such as Cu(2+), Co(2+), and Ni(2+) have been studied comparatively as a function of temperature and concentration. The adsorption process was found to increases with increase in temperature and concentration. The selectivity order for alpha-titanium and alpha-tin phosphates is Cu(2+)>Co(2+)>Ni(2+), whereas for alpha-zirconium phosphate it is Cu(2+)>Ni(2+)>Co(2+). The ion exchange capacity of alpha-titanium phosphate is greater than those of other phosphates, which is explained on the basis of the surface behavior, disorderness of the system, degree of hydrolysis of incoming guest adsorbate metal ions, and structural steric hindrance of the exchangers during adsorption and sorption. The distribution coefficient, Gibbs free energy, enthalpy, and entropy values indicate that the ion-exchange processes are spontaneous.     

High surface area Pd, Pt and Ni ion-exchanged Zr, Ti and Sn(IV) phosphates and their application to selective heterogeneous catalytic hydrogenation of alkenes

Amorphous acidic metal(IV) phosphates of zirconium, titanium and tin have been prepared and hydrogen-exchanged for bivalent Pd, Pt and Ni. These bivalent metals were returned to the zero valent state by reducing them with either hydrogen at 400 °C or with sodium tetrahydroborate at room temperature. The resulting Pd⁰, Pt⁰ and Ni⁰ phosphates were investigated as selective catalysts for heterogeneous hydrogenation of alkenes in solution at normal temperatures and pressures and, for Ni, also in the vapour phase. Quantitative studies on rates of hydrogenation are discussed. The usual methods for preparing metal(IV) phosphates give either crystalline or amorphous solids having low specific surfaces areas. A method has been developed, by which metal(IV) phosphates having large surface areas (lsa) may be prepared easily. These lsa supports take up large amounts of transition metal cations by simple exchange. The enhanced incorporation of Pd, Pt or Ni and increases in surface areas of the phosphate supports have provided some active, selective catalysts. Pd/Ti phosphates were the most active and compared well with commercial Pd on carbon. Ni/Ti phosphate is a very selective catalyst for vapour phase hydrogenation of alkenes and, at slightly higher temperatures, it is an efficient hydrocarbon cracking catalyst.     

A radiotracer study of adsorption on activated carbon cloth from aqueous solution

A study has been made on the effect of pH upon the equilibrium adsorption capacity of triethyl phosphate, dimethyl phosphate and orthophosphate on to activated carbon cloth. It is shown that for molecular phosphates no dependence upon pH exists, whilst the adsorption of ionic phosphates exhibit a strong pH dependence. These adsorption trends may be explained in terms of pKa values, ionic strength and the surface charge of the activated carbon cloth is aqueous solution.     

Structure of phosphatidyl serine (PS) involved in interbilayer salt bridging and hydrogen bonding

For understanding the experimental results indicating salt bridging and hydrogen bonding between opposite polar surfaces in planar multibilayer structures of phosphatidyl serine (PS), (1) we carried out molecular modeling of the interacting surface layers. The interacting structures in the planar multibilayers are stabilized by salt bridge arrays of the phosphates with their counterions and by hydrogen bonds of ammonia from one polar surface with carbonyls in the opposite one. In multishell liposomes, where the distances between phosphates on the facing each other surfaces are not equal and they are bound to get out of register, the interbilayer interaction cannot extend over a large enough area to form stable structures, except if the salt bridges are strong enough to break down the curved surfaces and form planar multibilayers.     

Some properties of milled vanadium phosphates

Mechanochemical modification of vanadium phosphates doped with Bi, Zr, Mo has been studied. Milled samples have been investigated by means of XRD, DTA-TG, FTIR, nitrogen adsorption, electrokinetic measurements. It was found that phase composition of the phosphates does not change upon the mechanochemical modification process. Milling in water causes formation of porous materials. Modification of surface results in changes of the electrokinetic and adsorption properties of the milled samples.     

Electrophoretic deposition of calcium phosphates from non-aqueous media

Electrophoretic deposition of ultrafine calcium phosphates from non-aqueous suspensions onto metallic substrates was attempted in order to obtain coatings with varying porosities. Aging effects were studied by measuring changes in the electrophoretic deposition behavior of the calcium phosphate particles in the non-aqueous suspensions. It was observed that the surfaces of the calcium phosphates develop significant electrostatic charge during aging in order to enable the formation of a dense and uniform deposit. The addition of surface charge conditioners such as HCl was found to have a similar effect. Dispersion conditions were varied to obtain coatings of the desired green densities, which were sintered to different microporosities.     

大比表面负载氧化铁的氧化硅层柱磷酸锆制备和 催化性能研究

提出了一种以氧化硅层柱磷酸锆(SiO~2-ZrP)的前驱体,氨丙基硅酸酯嵌入磷酸锆(APS-ZrP)为载体制备负载氧化铁的氧化硅层术磷酸锆的新方法。与传统方法相比,新方法制得的样品具有较大的比表面和孔容。X射线粉末衍射(XRD)和程序升温还原(TPR)的结果表明采用新方法有利于氧化铁在载体表面的高度分散,分散阈值为0.25gFe~2O~3/g(SiO~2-ZrP),远超过直接以SiO~2-ZrP为载体浸渍草酸铁铵的传统方法得到样品。同时,用新方法制得的氧化铁催化剂表现了较高的乙苯脱氢活性,是一类值得研究的催化材料。     

Surface Acidity of Alumina Aluminum Phosphate

Alumina aluminum phosphates in various aluminum to phosphor ratios were synthesized. The pore size can be easily controlled. The surface is weakly acidic. The number of acid sites per unit surface area shows a maximum at Al/P=1.9. The dehydration activity of tert-butanol correlates with the total acid amount, whereas the dehydration activity of isopropanol is related to both the mumber of acidic and basic sites.     

Methods of production,structure, and physicochemical characteristics of phosphorylated carbon adsorbents

The paper presents a review of methods for the production of phosphorylated carbon adsorbents, their structure, and their physicochemical characteristics. It was shown that the phosphorylated carbons contain phosphoric acid residues (condensed phosphates) attached to the carbon matrix mainly by a C—O—P bond and, to a lesser degree, by a C—P bond. The presence of the condensed phosphates in the structure of the carbon determines the hydrophilicity and the acidic characteristics and also the ability to absorb cations. The acidic characteristics of the surface of the phosphorylated carbons gives rise to their high catalytic activity in acid catalysis. The presence of the phosphates/polyphosphates improves the electrochemical characteristics of carbon materials for use as electrodes in supercapacitors. Potential fields for the practical application of phosphorylated carbons are the purification of water from heavy metal ions, the acceleration of reactions of the acid–base type, and the accumulation and storage of energy in double-layer capacitors.     

Fourier transform infrared investigations of phosphate-silicate coatings on iron

The influence of silica addition and of the annealing on the structure and properties of phosphate coatings are investigated. It has been observed that silica stabilizes phosphates and reduces the transport of iron towards the surface.     

Biological and medical significance of calcium phosphates

The inorganic part of hard tissues (bones and teeth) of mammals consists of calcium phosphate, mainly of apatitic structure. Similarly, most undesired calcifications (i.e. those appearing as a result of various diseases) of mammals also contain calcium phosphate. For example, atherosclerosis results in blood-vessel blockage caused by a solid composite of cholesterol with calcium phosphate. Dental caries result in a replacement of less soluble and hard apatite by more soluble and softer calcium hydrogenphosphates. Osteoporosis is a demineralization of bone. Therefore, from a chemical point of view, processes of normal (bone and teeth formation and growth) and pathological (atherosclerosis and dental calculus) calcifications are just an in vivo crystallization of calcium phosphate. Similarly, dental caries and osteoporosis can be considered to be in vivo dissolution of calcium phosphates. On the other hand, because of the chemical similarity with biological calcified tissues, all calcium phosphates are remarkably biocompatible. This property is widely used in medicine for biomaterials that are either entirely made of or coated with calcium phosphate. For example, self-setting bone cements made of calcium phosphates are helpful in bone repair and titanium substitutes covered with a surface layer of calcium phosphates are used for hip-joint endoprostheses and tooth substitutes, to facilitate the growth of bone and thereby raise the mechanical stability. Calcium phosphates have a great biological and medical significance and in this review we give an overview of the current knowledge in this subject.     

Layered Group(IV) Metal Phosphates as Catalysts for MTBE Synthesis

Layered group(IV) metal phosphates and their phenylsulfonic acid derivatives were used as catalysts for the synthesis of methyl tert-butyl ether (MTBE) from methanol and isobutene. Because zirconium and titanium phosphates have only moderate acidic strength, relatively high temperatures are required to activate their Brønsted acidic sites. The optimal activity was obtained at ca. 443 K. Their phenylsulfonic acid derivatives, however, demonstrated higher acidic strength by giving much higher activity toward MTBE formation at relatively low temperaures. The catalysts were characterized in terms of their structure, thermal stability, surface area and acidic strength.     

State of water in amorphous calcium and calcium-magnesium phosphates

Fourier-transform infrared spectra of three samples of deposited amorphous phosphates, calcium monodiphosphate (orthopyrophosphate) with a molar ratio 2P/(2P + 1P) of ～0.3, calcium magnesium monophosphate with an atomic ratio Mg/(Mg + Ca) of ～0.3, and calcium-magnesium monodiphosphate with a molar ratio 2P/(2P + 1P) of ～0.1 and atomic ratio Mg/(Mg + Ca) of ～0.1, were analyzed. On the basis of the observed similarity between the v(OH), δ(OH) and (δ + ω)(OH) lines in the spectra of these phosphates and liquid water analogous states of water molecules therein were assumed. It was presumed that the formation of amorphous phosphates involves deposition of poorly soluble substances on the surface of water nanoclusters.     

Atomic absorption inhibition titration of orthophosphate and polyphosphates

The atomic absorption inhibition titration of phosphates was studied for two types of burner. Dependence on gas Flow-rates was observed. The method with a pre-mix burner was employed to determine phosphate in surface and waste waters. The results are compared with those by the standard method. The proposed method was found to be rapid, simple and accurate.     

不同结构的磷酸盐对凝胶体系中草酸钙晶体物相和相组成的影响

泌尿系结石的形成是一种病理性生物矿化过程，不同地区的结石发病率在3％～15％之间。且50％(美国)至80％(中国)的人会复发。结石中约70％以上为草酸钙(CaC2O4)结石。CaC2O4结石的形成与其热力学(过饱和度)和动力学(成核、生长和聚集)因素有关。由于结石患者尿液和正常人尿液中     

Surface basicity on bulk modified phosphorus alumina through different synthesis methods

Bulk modified phosphorus alumina samples were prepared by gel method (GPA) and hydrolysis of phosphide aluminum (HPA). The γ-Al(2)O(3) impregnated by phosphates precursor (IPA) was also compared. The basicity of the samples has been investigated through the CO(2) adsorption/desorption processes by in situ DRIFT and temperature programmed desorption experiments. It was found that the surface basicity can be adjusted by different location of phosphates species. For the GPA sample, the phosphates species tends to be located in the grain boundaries as they were not stable enough to overcome the structure rearrangement at high temperatures. In contrast, phosphorus was stably anchored in the crystal lattice of HPA sample. Considering the synthesis process of HPA samples, phosphorus changed its valence state from P(-3) to P(+5) and migrated from anion to cation sites. The anion vacancies left in the lattice facilitated the formation of unsaturated oxygen ions and results in the enhanced basicity.     

Influence of alkyl chain length on phosphate self-assembled monolayers

A series of alkyl phosphates with alkyl chain lengths ranging from C10 to C18 have been synthesized. Self-assembled monolayers (SAMs) of these molecules were prepared on titanium oxide surfaces by immersion of the substrates in alkyl phosphate solutions of 0.5 mM concentration in n-heptane/isopropanol. The SAMs were characterized by means of dynamic water contact angle (dCA) measurements, variable-angle spectroscopic ellipsometry (VASE), X-ray photoelectron spectroscopy (XPS), and polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS). A higher degree of order and packing density within the monolayers was found for alkyl phosphates with alkyl chain lengths exceeding 15 carbon atoms. This is reflected in a lower dCA hysteresis, as well as a film thickness measured by VASE and XPS close to the expected values for SAMs with an average alkyl chain tilt angle of 30 degrees to the surface normal. Additionally a shift of the symmetric and antisymmetric C-H stretching modes in the PM-IRRAS spectra to lower wave numbers was observed. These findings imply a higher two-dimensional crystallinity of the films derived from alkyl phosphates with a longer alkyl chain length.