Effect of strontium ions substitution on gene delivery related properties of calcium phosphate nanoparticles

Gene therapy has been considered a strategy for delivery of therapeutic nucleic acids to a specific site. Calcium phosphates are one gene delivery vector group of interest. However, low transfection efficiency has limited the use of calcium phosphate in gene delivery applications. Present work aims at studying the fabrication of strontium substituted calcium phosphate nanoparticles with improved gene delivery related properties. Strontium substituted calcium phosphate was prepared using a simple sol gel method. X-ray diffraction analysis, Fourier transform infrared spectroscopy, transmission electron microscopy, specific surface area analysis, zeta potential measurement and ion release evaluation were used to characterize the samples. This characterization showed strontium and carbonate co-substituted calcium phosphate which resulted in nano size particles with low crystallinity, high specific surface area, positive surface charge, and a high dissolution rate. These improved properties could increase the DNA concentration on the vector as well as the endosomal escape of the complex that leads to higher transfection efficiency of this novel gene delivery vector.     

Studies on calcium deficient apatites structure by means of MAS-NMR spectroscopy

The development of synthetic apatites that replicate the features and properties of the contained in natural tissues will help to diminish the misfit between artificial implants and natural hostesses but the structure of these compounds is still under discussion. The variability in Ca/P ratio of calcium deficient apatites has been explained through different models: surface adsorption, lattice substitution and intercrystalline mixtures of hydroxyapatite and octacalcium phosphate. This work investigates which of the models mentioned suits better in a range of samples. Hydroxyapatites obtained by precipitation, by hydrolysis of dicalcium phosphate and calcined samples with Ca/P ratio between 1.50 and 1.77 and specific surface area between 7 and 108 m²/g have been analysed. OCP and surface adsorption models suit better for great SSA particles and low Ca/P ratio while for smaller SSA particles the lattice substitution model is more accurate. SSA also plays the main role when the capacity to absorb substances is studied though their chemistry can not be explained solely in terms of surface reactivity.     

Time-dependent growth of CaO nano flowers from egg shells exhibit improved adsorption and catalytic activity

Succulent shaped CaO 3D nano flowers have been synthesized by time growth morphological evaluation from bud-to-blossom using dumped egg shells. A comparative study between commercially available calcium oxide and synthesized CaO nano flowers for adsorptive removal of used engine oil and aldol condensation was conducted. The as-synthesized nano particles were characterized by hydrodynamic particle size analyser, surface area by (BET) Brunauer-Emmett-Teller, XRD (X-ray Diffraction) for crystal structural and SEM-EDX (Scanning Electron Microscopy - Energy Dispersive X-ray) and HR-TEM (High-Resolution-Transmission Electron Microscopy) for morphological examinations. The average size distribution calculated using W-H analysis (1.28–1.38 µm) and morphological studies (1.26–1.30 µm) were in good agreement. The CaO_nsf showed higher adsorption activity for spill oil remediation by dispersion-adsorption method with an extent of separation capacity upto 18 times its weight (18.31 gg⁻¹ of CaO_nsf) in comparison to CaO_cm (8.4 gg⁻¹). The as-synthesized nano flowers displayed excellent catalytic activity for aldol condensation between acetophenone and benzaldehyde. The nano flowers comprising of succulent petals, are formed from many irregular elongated nanospheres. Higher surface area availability leads to higher catalytic activity for production of chalcone with a yield of about 76.3%. This study paves a way for development of CaO based 3D nanostructures, possessing higher adsorption efficiency for oil and an efficient catalyst for base catalysed reactions.     

Modulating calcium phosphate formation using CO2 laser engineering of a polymeric material

The use of simulated body fluid (SBF) is widely used as a screening technique to assess the ability of materials to promote calcium phosphate formation. This paper details the use of CO₂ laser surface treatment of nylon® 6,6 to modulate calcium phosphate formation following immersion in SBF for 14 days. Through white light interferometry (WLI) it was determined that the laser surface processing gave rise to maximum Ra and Sa parameters of 1.3 and 4.4 μm, respectively. The use of X-ray photoelectron spectroscopy (XPS) enabled a maximum increase in surface oxygen content of 5.6%at. to be identified. The laser-induced surface modifications gave rise to a modulation in the wettability characteristics such that the contact angle, θ, decreased for the whole area processed samples, as expected, and increased for the patterned samples. The increase in θ can be attributed to a transition in wetting nature to a mixed-state wetting regime. It was seen for all samples that calcium phosphate formed on each surface following 14 days. The largest increase in mass, Δg, owed to calcium phosphate formation, was brought about by the whole area processed sample irradiated with a fluence of 51 J cm^− 2. No correlation between the calcium phosphate formation and the laser patterned surface properties was determined due to the likely affect of the mixed-state wetting regime. Strong correlations between θ, the surface energy parameters and the calcium phosphate formation for the whole area processed samples allow one to realize the potential for this surface treatment technique in predicting the bone forming ability of laser processed materials.     

Surface energy of hydroxyapatite and β-tricalcium phosphate ceramics driving serum protein adsorption and osteoblast adhesion

The main objective of this work was to evaluate the specific role of calcium phosphates surface energy on serum protein adsorption and human osteoblast adhesion, by isolating chemical effects from those caused by topography. Highly dense phosphate ceramics (single-phase hydroxyapatite HA and β-tricalcium phosphates β-TCP) presenting two distinct nano roughnesses were produced. Some samples were gold-sputter coated in order to conveniently mask the surface chemical effects (without modification of the original roughness) and to study the isolated effect of surface topography on cellular behavior. The results indicated that the nano topography of calcium phosphates strongly affected the protein adsorption process, being more important than surface chemistry. The seeding efficacy of osteoblasts was not affected nor by the topography neither by the calcium phosphate chemistries but the β-TCP chemistry negatively influenced cell spreading. We observed that surface hydrophobicity is another way to change protein adsorption on surfaces. The decrease of the polar component of surface energy on gold-coated samples leaded to a decreased albumin and fibronectin adsorption but to an increased cell adhesion. Overall, this work contributes to better understand the role of topography and surface chemistry of calcium phosphates in serum protein adsorption and osteoblast adhesion.     

The luminescent enhancement of LaPO<Subscript>4</Subscript>:Ce<Superscript>3+</Superscript>,Tb<Superscript>3+</Superscript> nano phosphors by radial aggregation

The rare earth nano phosphors can meet the challenging demand for new functional devices but their luminescence is always poor. Here we report on a simple method to prepare uniform LaPO₄:Ce³⁺,Tb³⁺ sphere-like nano aggregates from the precipitated nano phosphor crystallites without using any additive. The spontaneous aggregation is induced and controlled only by the suspension pH conditions. It is found that the 100 nm spherical aggregates can significantly improve the green emissions of the LaPO₄:Ce³⁺,Tb³⁺ nano particles. The intensity of the aggregates can be about 10 times as that of the 80 nm-sized individual ones. This study may provide a useful yet convenient strategy in the improvement and application of nano phosphors.     

Tricalcium phosphate and tricalcium phosphate/polycaprolactone particulate composite for controlled release of protein

β-Tricalcium phosphate (β-TCP) with three different particle size ranges was used to study the effects of particle size and surface area on protein adsorption and release. Polycaprolactone (PCL) coating was applied on the particle systems to investigate its effect on particulate system properties from both structural and application aspects. The maximum loading of 27 mg/g was achieved for 100 nm particles. Bovine serum albumin (BSA) loading amount was controlled by varying the BSA loading solution concentration, as well as the sample powder's surface area. Increasing the surface area of the delivery powder significantly increased loading and release yield. Unlike the samples with low surface area, the lowest particle size samples showed sigmoidal release profile. This indicated that release was governed by different mechanisms for particles with different sizes. While the majority of samples showed no more than 50% release, the 550 nm particles demonstrated 100% release. PCL coating showed no significant ability to attenuate burst release in PBS. However, it led to a steadier release profile as compared to the bare TCP particles. FTIR analysis also proved that the secondary structure of BSA did not change significantly during the adsorption; however, minor denaturation was found during the release. The same results were found when PCL coating was applied on the TCP particles. We envision potential use of TCP and TCP + PCL systems in bone growth factor or orthopedic drug delivery applications in future bone tissue engineering application.     

Reinforcement in Al Matrix Composites: A Review of Strengthening Behavior of Nano‐Sized Particles

Aluminum matrix composites (AMCs) reinforced with the nano‐sized particles are very important materials for the applications in industrial fields. These aluminum matrix composites consist of an aluminum matrix and nano‐sized particles, which own very different physical and mechanical properties from those of the matrix. Nano‐sized particles show a more obvious strengthening effect on the matrix than the micro‐sized particles do, because of the high specific surface area which is positive for the pinning effect during the deformation process. Thus, the nano‐sized particle‐reinforced AMCs usually exhibit a good ductility. The main issues of the fabrication methods are the low wettability between the nano‐sized particles and the molten aluminum alloys, which is fatal to the conventional casting methods, and the agglomeration of nano‐sized particles which happened easier than the larger particles. Several alternative processes have been presented in literature for the production of the nano‐sized particle‐reinforced aluminum composites. This paper is aimed at reviewing the feasible manufacturing techniques used for the fabrication of nano‐sized particle‐reinforced aluminum composites. More importantly, the strengthening mechanisms and models which are responsible for the improvement of mechanical properties of the nano‐sized particle‐reinforced aluminum composites have been reviewed.

     

Co‐condensation synthesis of well‐defined mesoporous silica nanoparticles: effect of surface chemical modification on plasmid DNA condensation and transfection

Chemically modified mesoporous silica nanoparticles (MSNs) are of interest due to their chemical and thermal stability with adjustable morphology and porosity; therefore, it was aimed to develop and compare the MCM‐41 MSNs functionalised with imidazole groups (MCM‐41‐Im) to unmodified (MCM‐41‐OH) and primary amine functionalised (MCM‐41‐NH₂) MSNs for experimental gene delivery. The results show efficient transfection of the complexes of the plasmid and either MCM‐41‐NH₂ or MCM‐41‐Im. Furthermore, following transfection of HeLa cells using MCM‐41‐Im, an enhanced GFP expression was achieved consistent with the noticeable DNase1 protection and endosomal escape properties of MCM‐41‐Im using carboxyfluorescein tracer.Inspec keywords: condensation, mesoporous materials, silicon compounds, nanoparticles, DNA, surface chemistry, porosity, gene therapy, cellular biophysics, biomedical materials, nanomedicine, nanofabrication, molecular biophysics, biochemistryOther keywords: co‐condensation synthesis, surface chemical modification, plasmid DNA condensation, plasmid DNA transfection, chemical modified mesoporous silica nanoparticles, chemical stability, thermal stability, adjustable morphology, porosity, MCM‐41 MSN functionalisation, imidazole groups, MCM‐41‐OH, primary amine functionalised MSN, gene delivery, HeLa cell transfection, GFP expression, DNase1 protection, endosomal escape properties, carboxyfluorescein tracer, SiO₂      

磷酸钙纳米粒子的潜在毒性:物理化学性质的影响、评价方法和可能的毒性机制

磷酸钙是骨和牙的主要无机成分,具有良好的生物活性和生物相容性。研究表明,当磷酸钙粒子尺寸降到纳米尺度时具有一些独特的理化性能,如小尺寸效应和表面效应等,有望拓展其在生物医学领域中的应用,如作为治疗肿瘤的靶向药物载体和疾病诊断的基因载体等。但上述应用均需与机体直接接触,因此,评价磷酸钙纳米粒子潜在的毒性风险非常必要。有研究发现磷酸钙纳米粒子的理化性能,包括尺寸、形貌、表面性能和结晶度等均会影响纳米粒子与机体及细胞的相互作用,可能导致纳米粒子产生一定毒性。总结了磷酸钙纳米粒子的物理化学性能对其潜在毒性的影响及可能机制,综述了材料毒性评价的主要方法,希望能为磷酸钙纳米材料的设计及生物相容性评价标准的制定提供一定的理论依据。     

High surface area neodymium phosphate nano particles by modified aqueous sol-gel method

Synthesis of nano rod shaped neodymium phosphate (NdPO₄) particles with specific surface area as high as 107 m²g⁻¹ and an average length of 50 nm with aspect ratio 5 was achieved using modified sol gel method. Crystallite size calculated from the X-ray diffraction data by applying Scherer equation was 5 nm for the precursor gel after calcination at 400 °C. NdPO₄ was first precipitated from neodymium nitrate solution using phosphoric acid followed by peptization using dilute nitric acid and further gelation in ammonia atmosphere. The calcined gel powders were further characterized by surface area (Brunauer-Emmet-Teller nitrogen adsorption analysis), Transmission electron microscopy, scanning electron microscopy, UV-vis and FT-IR analysis. Transmission electron microscopy confirms the formation of rod like morphology from the sol, gel and the calcined particles in nano size range. These particles could be compacted and sintered at as low as 1300 °C to a density of 98.5% (theoretical) with an average grain size of ∼1 μm.     

Effects of calcium impurity on phase relationship,ionic conductivity and microstructure of Na<Superscript>+</Superscript>- β / β<Superscript>″</Superscript>-alumina solid electrolyte

Ca-doped Na⁺- β/β^′′-alumina was synthesized using a solid-state reaction. The changes in the properties of Na⁺- β/β^′′-alumina resulting from the presence of Ca impurity were studied. Ca (0–5 wt%) was added to the respective samples, which were then sintered. The specimens were characterized using X-ray diffraction, scanning electron microscopy, densimetry and impedance analysis. In the sintered specimens, the β^′′-alumina phase fraction decreased as Ca content increased, whereas the relative sintered density increased. The surface morphology of Ca-doped Na⁺- β/β^′′-alumina specimens showed a Ca-rich layer, which was the main cause of increase in the specific resistance.     

A novel activated carbon for supercapacitors

A novel activated carbon has been prepared by simple carbonization and activation of phenol–melamine–formaldehyde resin which is synthesized by the condensation polymerization method. The morphology, thermal stability, surface area, elemental composition and surface chemical composition of samples have been investigated by scanning electron microscope, thermogravimetry and differential thermal analysis, Brunauer–Emmett–Teller measurement, elemental analysis and X-ray photoelectron spectroscopy, respectively. Electrochemical properties have been studied by cyclic voltammograms, galvanostatic charge/discharge, and electrochemical impedance spectroscopy measurements in 6 mol L^?1 potassium hydroxide. The activated carbon shows good capacitive behavior and the specific capacitance is up to 210 F g^?1, which indicates that it may be a promising candidate for supercapacitors.     

Study of the influence of the structural grain size on the mechanical properties of technical materials

The mechanical properties of technical materials depend on their structure. They are influenced not only by their chemical composition, but particularly by the structural grain size. Significant changes in the mechanical behaviour of materials are related both to surface and volume properties, and not only in the field of mechanical parameters. A wide range of physical and chemical parameters changes as well. Nano‐materials are the materials, the structural grain size of which is in the dimensional area from 10^?9 to 10^?7 m. Nano‐particles and nanostructures are thus so small that their behaviour is affected by atomic forces, properties of chemical bonding, and quantum phenomena. The wave nature of the very small particles begins to manifest itself. The aim of the authors is to contribute by their paper to the solution of the problems in the field of material engineering. This means to investigate the specifics in the behaviour of technical materials depending on the change in the structural grain size towards the nano‐areas, as well as the design and use of new techniques of mathematical and physical modelling including the operative measurement method.     

磷酸钙微球骨修复材料研究进展

磷酸钙微球具有良好的渗透性、高的比表面积、低致密度和较好的力学性能,在分离、催化、传感、组织工程和药物释放等方面均有应用。本文综述了近年来磷酸钙陶瓷微球在组织工程和药物释放等骨修复相关领域的研究进展, 介绍了实心、多孔、空心和花瓣状等四种不同结构磷酸钙陶瓷微球制备方法以及在骨修复领域中的应用, 并归纳总结了各类微球具有的优缺点和改进的方向, 为骨修复用磷酸钙微球的设计和制备提供较系统的参考。     

Preparation of Bioactive Mesoporous Calcium Phosphate Granules

Mesoporous calcium phosphate granules ranging in mesopore size from 11 to 19 nm have been prepared using cryogenic processing (–18°C) of gels and extrusion of calcium phosphate paste. The granules based on acid calcium phosphates have a relatively small specific surface area (45 m²/g) in comparison with the neutral and basic calcium phosphates (84–155 m²/g). Preclinical in vivo trials on rats show that the presence of calcium phosphate granules in a bone defect considerably accelerates reparative osteogenesis in comparison with a control group of animals.     

Properties of Nanostructured Hydroxyapatite Prepared by a Spray Drying Technique

In previous studies nano sized hydroxyapatite (HA) particles were prepared by solgel or precipitation methods, in which the products were washed by aqueous or non-aqueous liquids to remove impurities or undesired components. The washing is know to modify the surfaces of the cystalline particles. This study evaluated properties of nano HA materials prepared by a spray drying method in which the HA product was not exposed to any liquid after its formation. The spray drying apparatus consisted of a nozzle that sprayed an acidic calcium phosphate solution in the form of a fine mist into a stream of filtered air flowing through a heated glass column. The water and volatile acid were evaporated by the time the mist reached the end of the column, and the fine particles were collected by an electrostatic precipitator. Powder x ray diffraction patterns suggested the material was amorphous, exhibiting a single broad peak at 30.5° 2θ. However, high resolution transmission electron microscopic analysis showed that the particles, some of which were 5 nm in size, exhibited well ordered HA lattice fringes. Small area diffraction patterns were indicative of HA. Fourier transfer infrared spectroscopy showed patterns of typical of HA with small amounts of HPO₄²⁻. The thermodynamic solubility product of the nano HA was 3.3 × 10⁻⁹⁴ compared to 1 × 10⁻¹¹⁷ for macro scale crystalline HA. These results showed that a spray drying technique can be used to prepare nanometer sized crystalline HA that have significantly different physicochemical properties than those of its bulk-scale counterpart.     

Characterisation of CorGlaes<Superscript>®</Superscript> Pure 107 fibres for biomedical applications

A degradable ultraphosphate (55?mol?% P₂O₅) quinternary phosphate glass composition has been characterised in terms of its chemical, mechanical and degradation properties both as a bulk material and after drawing into fibres. This glass formulation displayed a large processing window simplifying fibre drawing. The fibres displayed stiffness and strength of 65.5?±?20.8?GPa and 426±143 MPa. While amorphous discs of the glass displayed a linear dissolution rate of 0.004?mg cm^?2?h^?1 at 37?°C, in a static solution with a reduction in media pH. Once drawn into fibres, the dissolution process dropped the pH to <2 in distilled water, phosphate buffer saline and corrected-simulated body fluid, displaying an autocatalytic effect with >90?% mass loss in 4 days, about seven times faster than anticipated for this solution rate. Only cell culture media was able to buffer the pH taking over a week for full fibre dissolution, however, still four times faster dissolution rate than as a bulk material. However, at early times the development of a HCA layer was seen indicating potential bioactivity. Thus, although initial analysis indicated potential orthopaedic implant applications, autocatalysis leads to accelerating degradation in vitro.     

Towards understanding biomineralization: calcium phosphate in a biomimetic mineralization process

Abstract Biomineralization processes result in organic/inorganic hybrid materials with complex shapes, hierarchical structures, and superior material properties. Recent developments in biomineralization and biomaterials have demonstrated that calcium phosphate particles play an important role in the formation of hard tissues in nature. In this paper, current concepts in biomineralization, such as nano assembly, biomimetic shell structure, and their applications are introduced. It is confirmed experimentally that enamel- or bone-liked apatite can be achieved by oriented aggregations using nano calcium phosphates as starting materials. The assembly of calcium phosphate can be either promoted or inhibited by different biomolecules so that the kinetics can be regulated biologically. In this paper, the role of nano calcium phosphate in tissue repair is highlighted. Furthermore, a new, interesting result on biomimetic mineralization is introduced, which can offer an artificial shell for living cells via a biomimetic method.     

Corrosion protection of cement-based building materials by surface deposition of CaCO3 by Bacillus pasteurii

Bacterially induced calcium carbonate precipitation was used as a novel and environmentally friendly approach to produce a protective layer on the surface of cement-based materials in the study. The physical and chemical properties of the obtained layer were examined. X-ray diffraction analysis characterized the composition of the deposited layer and scanning electron microscopy displayed the morphology of particles. The results showed that both bacterial activity and the method of adding Ca²⁺ and urea had a profound effect on the properties of the calcium carbonate layer. A capillary water absorption test was carried out to evaluate the ability of the protective layer to improve the resistance to water penetration. Experimental results indicated that the calcium carbonate layer, obtained under the conditions of high bacterial activity, appropriate concentration of Ca²⁺, and adding Ca²⁺ before urea to the reaction mixture, could greatly improve the water penetration resistance of the specimen surface. This type of treatment has the potential to conserve and consolidate cement-based materials.