Study of controlled tetracycline release from porous calcium phosphate/polyhydroxybutyrate composites

Porous calcium phosphate ceramics were prepared by sintering of mixtures of nanocrystalline apatitic calcium phosphate and fibrous natural cotton cellulose after pressing at temperatures of 1150 °C and 1250 °C. Micro-and macropores were present in microstructures of ceramic samples. The microstructures of porous ceramics were similar to those observed in bone tissues and fiber-like randomly oriented texture was observed in ceramics. Polyhydroxybutyrate (PHB) biopolymer layers are distributed homogeneously in the samples after evaporation of the diluent (chloroform) from the PHB vacuum impregnated porous samples. The tetracycline (TTC) release rate decreases with the content of polyhydroxybutyrate in the ceramic samples, which corresponds to the rise in amount of biopolymer displaced in the pores of ceramics. The concentration of TTC in the phosphate buffer saline solution varies almost linearly with time after the first seven hours from the start of the release of the calcium phosphate ceramic samples with 2.4 mass % of polyhydroxybutyrate. The initial burst effect was significantly depressed by the preparation method used.     

Redispersible and stable amorphous calcium phosphate nanoparticles functionalized by an organic bisphosphate

Although much effort has been focused on the preparation of stable amorphous calcium phosphate （ACP） nanoparticles in aqueous solution, the redispersibility and long-term stability of ACP nanoparticles in aqueous solution remains an unresolved problem. In this work, stable colloidal ACPs were prepared by using an organic bisphosphonate （BP） as a sterically hindered agent in aqueous solution. The harvested calcium phosphate nanoparticles were characterized by inductively coupled plasma atomic emission spectrometry （ICP-AES）, Fourier transform infrared （FTIR）, X-ray diffraction （XRD）, dynamic light scattering （DLS） and transmission electron microscopy （TEM）. ICP-AES, FTIR and XRD results suggested the particles were ACP. DLS and TEM results indicated that the size of the ACP nanoparticles were in the range of 60 nm with a spherical morphology. The resulting calcium phosphate nanoparticles retained its amorphous nature in aqueous solution for at least 6 months at room temperature due to the stabilizing effect of the organic bisphosphonate. Moreover, the surface of the ACP nanoparticles adsorbed with the organic bisphosphate used showed good redispersibility and high colloid stability both in organic and aqueous solutions.     

Mechanochemical-hydrothermal synthesis of calcium phosphate powders with coupled magnesium and carbonate substitution

Magnesium- and carbonate-substituted calcium phosphate powders (Mg-, CO₃-CaP) with various crystallinity levels were prepared at room temperature via a heterogeneous reaction between MgCO₃/Ca(OH)₂ powders and an (NH₄)₂HPO₄ solution using the mechanochemical-hydrothermal route. X-ray diffraction, infrared spectroscopy, and thermogravimetric analysis were performed. It was determined that the powders containing both Mg²⁺ and CO₃²⁻ ions were incorporated uniformly into an amorphous calcium phosphate phase while in contrast, the as-prepared powder free of these dopants was crystalline phase-pure, stoichiometric hydroxyapatite. Dynamic light scattering revealed that the average particle size of the room temperature Mg-, CO₃-CaP powders was in the range of 482 nm-700 nm with a specific surface area between 53 and 91 m²/g. Scanning electron microscopy confirmed that the Mg-, CO₃-CaP powders consisted of agglomerates of equiaxed, ≈20-35 nm crystals.     

Association of collagen with calcium phosphate promoted osteogenic responses of osteoblast-like MG63 cells

In this investigation, the effects of the association of the collagen (COLL) molecules with the calcium phosphate (CaP) film were examined with respect to both the physicochemical properties of the CaP films and the osteoblast responses, such as the adhesion, proliferation, differentiation, and mineralization. The COLL pre-adsorbed CaP film (CaPA) exhibited significant changes in the surface morphology compared to the COLL incorporated CaP film (CaPC). The adhesions of the osteoblast-like MG63 cells were similar on the CaPC or CaPA films. However, the proliferation of the MG63 cells on CaPC was comparable to CaP but considerably different than CaPA. The differentiation of the MG63 cells was greatly improved on CaPC and CaPA compared to CaP and more pronounced on CaPA. The presence of COLL within or on the CaP films significantly modulated the expression of the phenotypic genes, including osteopontin (OPN), alkaline phosphatase (ALP), and the transforming growth factor-β (TGF-β). The expression patterns of these genes elucidated that COLL that was present within or on the CaP film supported the osteoblast proliferation and differentiation. These positive effects were stronger for CaPA than CaPC. The bone-like nodules formed on all of the specimens. However, the mineralization of CaPC and CaPA was significantly higher than CaP, indicating that the association of CaP with COLL promoted the mineral deposition. Therefore, the association of the COLL molecules with the CaP film induced positive effects on the biomineralization. Overall, the incorporation of COLL efficiently enhanced the osteoblast responses of CaP. This system can be utilized in a drug delivery system using calcium phosphate. Although the incorporation effects were slightly higher for the osteoblast responses of CaPA than CaPC, CaPC can be used when the longer drug release times are desirable.     

Templated growth of calcium phosphate on tyrosine derived microtubules and their biocompatibility

Microtubular structures were self-assembled in aqueous media from a newly synthesized bolaamphiphile, bis(N-alpha-amido-tyrosyl-tyrosyl-tyrosine)-1,5-pentane dicarboxylate. In order to increase the biocompatibility of the microtubules, they were functionalized with the peptide sequence GRGDSP. Further, calcium phosphate nanocrystals were grown on the microtubules. In some cases, collagen was added in order to mimic the components of natural bone tissue. The biomaterials obtained were characterized via transmission electron microscopy (TEM), atomic force microscopy (AFM), IR, and energy dispersive X-ray spectroscopy (EDX) analyses. The biocompatibility of the calcium phosphate-coated microtubules was studied by conducting in vitro cell-attachment, cell-proliferation and cytotoxicity studies using mouse embryonic fibroblast (MEF) cells. The studies revealed that the biomaterials were found to be non-toxic and biocompatible. The functionalized tubular assemblies coated with calcium phosphate nanocrystals mimic the nanoscale composition of natural bone and may potentially support bone in-growth and osseointegration when used in orthopaedic or dental applications.     

Preparation and characterization of calcium hydroxyapatite and balloon-like calcium phosphate particles from forced hydrolysis of Ca(OH)2–triphosphate solution

Calcium phosphate particles were prepared by aging a solution of dissolved Ca(OH)₂ and sodium triphosphate (sodium tripolyphosphate, Natpp: Na₅P₃O₁₀) at 100–150 °C for 18 h in a Teflon-lined screw-capped Pyrex test tube. Large spherical and/or small aggregated spherical particles were precipitated with an extremely fast rate of reaction under 100 °C. The large spherical particles were amorphous and the small aggregated ones were α-CaNa₂P₂O₇^.4H₂O. The former amorphous ones crystallized to β-Ca₂P₂O₇ after being calcined above 600 °C. Calcium hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, Hap), with rod-like and ellipsoidal or spherical aggregated shapes, was successfully produced using polyphosphates as a source of orthophosphate ions. Time resolved TEM measurement revealed that the crystallization of Hap particles takes place on the surface of tiny amorphous particles precipitated before aging. The tiny particles played the role of nuclei for Hap crystallization. The aging temperature drastically varied the particle shape under conditions for producing uniform amorphous spherical particles; solid spherical particles were produced with an aging temperature of up to 120 °C, whilst transparent balloon-like hollow spheres were precipitated at 125 °C. Finally, fully transparent balloon-like hollow spheres were produced with mere trace amounts of small rod-like particles after aging the solution above 127 °C. The time resolved TEM observation and ICP-AES measurements revealed that the balloon-like hollow spheres were produced by dissolving the interior of solid spherical particles after reinforcing their shell by the adsorption of unhydrolyzed tpp and/or pyrophosphate (pp) ions, which are the hydrolysis product of tpp. The balloon-like hollow spheres of calcium phosphate may have the potential use as drug delivery vehicles and have biocompatibility advantages.     

Rapid one-pot fabrication of magnetic calcium phosphate nanoparticles immobilizing DNA and iron oxide nanocrystals using injection solutions for magnetofection and magnetic targeting

This is the first report on rapid (5–30 min) one-pot fabrication of magnetic calcium phosphate (CaP) nanoparticles (NPs) co-immobilizing DNA and iron oxide (IO) nanocrystals with high immobilization efficiencies (DNA (～90%) and IO (～70%)). NPs were fabricated via coprecipitation under clean bench in supersaturated CaP solutions using DNA, IO-based MRI contrast agent, and infusion quality source solutions (even the water used was of injectable quality) that ensured high safety level of the fabrication process and product. Prepared DNA-IO-CaP NPs exhibited strong magnetic property allowing their noncontact manipulation by external magnet. These NPs were smaller than 500 nm, had relatively large negative zeta potential showing stable dispersion without any additional surfactant, and exhibited no significant cytotoxicity under the tested transfection conditions. The IO content of these NPs was significantly varied and by adjusting the initial IO concentration, DNA-IO-CaP NPs with gene delivery capability to CHO-K1 cells as high as that of the IO-free DNA-CaP NPs without external magnetic field were prepared. Fabricated DNA-IO-CaP NPs showed significantly improved gene delivery capability under external magnetic field compared to the IO-free DNA-CaP NPs. Thus, the present coprecipitation process can be considered as a novel technique to fabricate multifunctional CaP-based NPs to achieve magnetofection and targeted delivery.     

Preparation, characterization, and controlled release of novel nanoparticles based on MMA/beta-CD copolymers

A series of random copolymers with different beta-cyclodextrin contents were synthesized by radical copolymerization of MMA with a monovinyl beta-CD monomer. The copolymers were characterized with IR spectroscopy, elemental analysis, DSC, and TGA. Based on these copolymers, their nanoparticles were prepared by using DMF, water, and acetone as solvents. Aqueous dispersions of the nanoparticles were further obtained by dialysis against water. Zetasizer Nano-ZS dynamic light scattering and transmission electron microscopy were employed to characterize the nanoparticles. Using camptothecin as a model drug molecule, the encapsulation efficiency and release behavior of the nanoparticles were investigated.     

Recent developments of metallic nanoparticles and their catalytic activity in organic reactions

During the last two decades, with the development of nanotechnology, various nanomaterials have been designed and generated. Among them, hybrid organic–inorganic nanoparticles as a particular immobilizing carrier of the catalyst active sites have shown an important contribution in the current research studies. This is due to the large area and loads of active sites. This prominent review is focused on the novel various exa about the immobilization of nanoparticles with organic compounds as versatile and efficient catalysts in organic syntheses.     

Inhibition of the crystal growth and aggregation of calcium oxalate by elemental selenium nanoparticles

Chemical modulation of calcium oxalate (CaC₂O₄) crystals morphologies by elemental selenium nanoparticles (nanoSe⁰) was investigated with scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), Fourier transform infrared spectrometry (FTIR), and X-ray diffraction (XRD) analysis. The coordination between nanoSe⁰ and C₂O₄²⁻ had great effect on the formation of CaC₂O₄ crystals. NanoSe⁰ inhibited the growth of calcium oxalate monohydrate (COM) crystals, prevented the aggregation of COM crystals and induced the formation of the spherical calcium oxalate dihydrate (COD) crystals containing selenium, which are the thermodynamically less stable phase and has a weaker affinity to the cell membranes than COM crystals. The inhibition of the crystal growth and aggregation of CaC₂O₄ crystals by nanoSe⁰ displayed concentration effects.     

Direct formation of silver nanoparticles in cuttlebone-derived organic matrix for catalytic applications

Development of biologically derived materials for the construction of materials with new functions is a crucial intersection of materials science and biotechnology, which is currently a topic of research interest. In this paper, we report on the use of cuttlebone-derived organic matrix (CDOM) as scaffold and reducer for the formation of silver nanoparticles (AgNPs). The experiment was carried out by simple immersing of CDOM in tollen’s reagent and incubating at 80 °C. UV–vis spectra and TEM were utilized to characterize the AgNPs and investigate their formation process. Results demonstrate that the size and distribution of AgNPs are influenced by the incubation time and protein component in CDOM. Furthermore, the AgNPs–CDOM composite was applied to catalyze the reduction of 4-nitrophenol in the presence of NaBH₄, and it can be easily separated from the liquid-phase reaction system during the reusing cycles.     

Entrapment and release of sodium polystyrene sulfonate (SPS) from calcium alginate gel beads

The release of sodium polystyrene sulfonate (SPS) from calcium alginate hydrogel beads has been studied. It has been shown that the structure of the cross-linked calcium alginate network is of primary importance in the retention and/or release of the SPS. This has been evidenced by studying the influence of Ca²⁺ concentration, molar masses (M_n) and the ratio of mannuronic acid/guluronic acid components. A minimum in the SPS release is observed in relation with the organization of the network structure. Conditions inducing the organization of a strong gel (e.g. high Ca²⁺ concentration for example) are not always related to a low release. A good control of release is found when a compromise between a well-structured hydrogel and sterical consideration of SPS is reached.     

Study on the preparation and formation mechanism of barium sulphate nanoparticles modified by different organic acids

This paper reports a simple method to prepare barium sulphate nanoparticles by use of tetradecanoic acid, hexadecanoic acid and stearic acid as modifier. The barium sulphate nanoparticles obtained are characterized by using Fourier transform infra-red spectroscopy (FT-IR), powder X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic laser light scatter (DLLS) and thermogravimetric analysis (TGA), respectively. The results show that the BaSO₄ particles are all spherical and in the nano-scale. Our method has a better dispersion and controllable diameter dependent on the length of the chain of organic acid and the pH value of the system. A possible mechanism is also discussed.     

多贝斯在纳米金修饰玻碳电极上的电化学行为与测定

采用循环伏安法将纳米金电沉积于玻碳电极表面,制备了纳米金修饰玻碳电极(NG/GCE).在0.05 mol/L H2SO4溶液中,用循环伏安法研究了多贝斯在NG/GCE上的电化学行为.结果表明,NG/GCE对多贝斯的氧化还原反应有明显的电催化作用.建立了测定多贝斯的新方法,用方波伏安法测得多贝斯的氧化峰电流与其浓度在4....     

Synthesis and application of silica and calcium carbonate nanoparticles in the reduction of organics from refinery wastewater

Oil refinery is one of the fast growing industries across the globe and it is expected to progress in the near future. The worldwide increase in the generation of refinery wastewater along with strict environmental regulations in the discharge of industrial effluent, persistent efforts have been devoted to recycle and reuse the treated water. The wastewater from the refining operation leads to serious environmental threat to the ecosystem. Therefore, this study aimed to synthesize silica (SiO₂) and calcium carbonate nanoparticles (CaCO₃) in the reduction of organics from refinery wastewater. The synthesized nanoparticles were employed in the reduction of chemical oxygen demand (COD) from refinery wastewater by studying the influence of solution pH, contact time, dosage of nanoparticles and stirring speed on adsorption performance. From the batch experimental studies, the optimized processing conditions for the reduction of COD using SiO₂ nanoparticles are pH 4.0, dosage 0.5 g, stirring speed 125 rpm and 90 min stirring time, and the corresponding values for CaCO₃ nanoparticles are pH 8.0, dosage 0.4 g, stirring speed 100 rpm and 90 min stirring time. The study demonstrates that SiO₂ and CaCO₃ nanoparticles have a promising future in the reduction organics from refinery wastewater in different pH regimes.     

Novel palladium nanoparticles supported on mesoporous natural phosphate: Catalytic ability for the preparation of aromatic hydrocarbons from natural terpenes

Various ratios of palladium nanoparticles supported on mesoporous natural phosphate (Pd@NP) were prepared using the wetness impregnation method. The prepared catalysts were characterized by IR, XRD, CV, SEM, EDX, XRF, TEM and BET analysis. The reduction and preparation of the palladium nanoparticles afford a crystallite size of 10.88 nm. The performance of the synthesized catalyst was investigated in the solvent-free dehydroaromatization of α-, β- and γ-himachalene mixture from Cedrus atlantica oil as a model substrate. In order to achieve an efficient and selective catalysis, the catalytic dehydroaromatization of various terpenes such as limonene, limonaketone, carvone, carveol and perillyl alcohol was studied. The Pd@NP catalyst performed a high catalytic activity, selectivity and recyclability in the terpenes dehydroaromatization reaction.     

Synthesis of organic nanoparticles of naphthalene-thiourea-thiadiazole-linked molecule as highly selective fluorescent and colorimetric sensor for Ag(I)

A novel fluorescent and colorimetric sensor was synthesized by a reprecipitation to probe Ag⁺ ions in water on naphthalene-thiourea-thiadiazole (NTTA) molecular nanocrystals. The fluorescent organic nanoparticles (FONs) allowed a highly sensitive determination of free Ag⁺ ions in aqueous media. The possible mechanism was discussed.     

Facile preparation of water dispersible red fluorescent organic nanoparticles and their cell imaging applications

Red fluorescent organic nanoparticles (FONs) based on a cyano-substituted diarylethylene and tetraphenylethene derivative conjugated molecule (R-TPE) were facilely prepared via surfactant modification with lecithin for the first time. The obtained R-TPE-LEC FONs were characterized by a series of techniques including fluorescence and UV spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. Biocompatibility evaluation and cell uptake behavior of R-TPE-LEC FONs were further investigated to explore their potential biomedical application. We demonstrated that such red FONs exhibit anti-aggregation-caused quenching property, broad excitation wavelength, high water dispersibility, uniform morphology (40–60 nm), and excellent biocompatibility, making them promising for cell imaging application.