Ya-Jun Guo

Magnetic mesoporous carbonated hydroxyapatite microspheres with hierarchical nanostructure for drug delivery systems

Magnetic mesoporous carbonated hydroxyapatite microspheres have been fabricated hydrothermally by using CaCO(3)/Fe(3)O(4) microspheres as sacrificial templates. The high drug-loading capacity and sustained drug release property suggest that the multifunctional microspheres have great potentials for bone-implantable drug-delivery applications.

Hydrothermal synthesis of hydroxyapatite coatings with oriented nanorod arrays

Hydroxyapatite coatings (HACs) with oriented nanorod arrays have been fabricated according to the following stages: (i) sol–gel preparation of bioglass coatings (BGCs) on Ti6Al4V substrates; and (ii) transformation of the BGCs to the HACs in a simulated body fluid (SBF) under hydrothermal conditions. After soaking the BGCs in SBF for 12 h under hydrothermal conditions, the elongated HA rods deposit on the surfaces via a dissolution–precipitation reaction. The TEM image and corresponding ED pattern indicate that the HA rods in the HACs are single crystals with a preferential (002) orientation. With increasing the reaction time to 2 days, most of the HA rods are converted to HA particles due to Ostwald ripening. If SBF is replaced by deionized water, the obtained coatings are rod-like HA with the poor crystal orientation. Beside the reaction time and reaction medium, the reaction conditions play an important role in the morphologies of the HACs. Although a HA layer deposits also on the BGCs after soaking in SBF at 37 °C, the HA crystals exhibit plate-like structure. SBF immersion tests and biocompatibility tests by using human bone marrow stromal cells (hBMSCs) as cell models indicate that the HACs with oriented nanorod arrays exhibit great in vitro bioactivity and biocompatibility. The oriented HA rods on the coatings can not only promote the formation of bone-like apatite, but also improve the adhesion, spreading and proliferation of hBMSCs. The excellent in vitro bioactivity and biocompatibility suggest that the HACs with oriented nanorod arrays have great potential for bone implants.

Hydrothermal fabrication of magnetic mesoporous carbonated hydroxyapatite microspheres: biocompatibility, osteoinductivity, drug delivery property and bactericidal property

Implant-associated infection is a serious problem in orthopaedic surgery. Ideal bone filling materials should not only possess excellent biocompatibility, but also have good anti-infection property and osteoinductivity. Herein, magnetic mesoporous carbonated hydroxyapatite microspheres (MHMs) have been fabricated according to the following stages: (i) preparation of CaCO3/Fe3O4 microspheres; and (ii) hydrothermal transformation of magnetic calcium carbonate microspheres into MHMs. MHMs possess well-defined 3D nanostructures constructed by nanoplates as building blocks. The mesopores and macropores exist in and among the nanoplates, respectively. The porous structure makes the MHMs possess a great drug loading efficiency of 73-82%. Gentamicin-loaded MHMs display a sustained drug release property, and the controlled release of gentamicin can prevent biofilm formation against S. epidermidis. Moreover, the MHMs possess a magnetic property with a saturation magnetization strength of 3.98 emu g-1 because Fe3O4 nanoparticles are dispersed in the microspheres. The in vitro cell tests indicate that the magnetic nanoparticles in the MHMs not only promote the cell adhesion and proliferation of human bone marrow stromal cells (hBMSCs), but also stimulate the osteogenic differentiation. MHMs exhibit excellent biocompatibility, osteoinductivity, drug delivery property and bactericidal property, so they have great application potential for the treatment of complicated bone defects.

Magnetic hydroxyapatite coatings with oriented nanorod arrays: hydrothermal synthesis, structure and biocompatibility

Ideal biocoatings for bone implants should be similar to the minerals of natural bones in chemical composition, crystallinity, and crystallographic texture. Herein, magnetic hydroxyapatite (HA) coatings (MHACs) with oriented nanorod arrays have been fabricated by using magnetic bioglass coatings (CaO-SiO2-P2O5-Fe3O4, MBGCs) as sacrificial templates. After the hydrothermal reaction for 24 h, the MBGCs are converted to MHACs in a simulated body fluid (SBF) via a dissolution-precipitation reaction. The formed HA nanorods with a preferential (002) orientation are perpendicular to the coating surfaces. The Fe3O4 nanoparticles in the coatings improve the nucleation rate of HA, so the elongated HA nanocrystals are retained even after hydrothermal reaction for 3 days. In contrast, if no magnetic nanoparticles are incorporated into the bioglass coatings (BGCs), the HA nanorods turn into blocky HA particles upon increasing the reaction time from 12 h to 24 h. Moreover, the MHACs possess much better hydrophilicity with a contact angle of 10.8° than the HA coatings because of the presence of Fe3O4 nanoparticles. The biocompatibility tests have been investigated by using human bone marrow stromal cells (hBMSCs) as cell models. The hBMSCs have better cell adhesion, spreading and proliferation on the MHACs than on the BGCs or MBGCs because of the HA phase, good hydrophilicity and oriented nanorod arrays. The excellent biocompatibility of the MHACs suggests that they have great potential for bone implants.

Bactericidal property and biocompatibility of gentamicin-loaded mesoporous carbonated hydroxyapatite microspheres

Implant-associated infection is a serious problem in orthopaedic surgery. One of the most effective ways is to introduce a controlled antibiotics delivery system into the bone filling materials, achieving sustained release of antibiotics in the local sites of bone defects. In the present work, mesoporous carbonated hydroxyapatite microspheres (MCHMs) loaded with gentamicin have been fabricated according to the following stages: (i) the preparation of the MCHMs by hydrothermal method using calcium carbonate microspheres as sacrificial templates, and (ii) loading gentamicin into the MCHMs. The MCHMs exhibit the 3D hierarchical nanostructures constructed by nanoplates as building blocks with mesopores and macropores, which make them have the higher drug loading efficiency of 70-75% than the conventional hydroxyapatite particles (HAPs) of 20-25%. The gentamicin-loaded MCHMs display the sustained drug release property, and the controlled release of gentamicin can minimize significantly bacterial adhesion and prevent biofilm formation against S. epidermidis. The biocompatibility tests by using human bone marrow stromal cells (hBMSCs) as cell models indicate that the gentamicin-loaded MCHMs have as excellent biocompatibility as the HAPs, and the dose of the released gentamicin from the MCHMs has no toxic effects on the hBMSCs. Hence, the gentamicin-loaded MCHMs can be served as a simple, non-toxic and controlled drug delivery system to treat bone infections.

Bactericidal properties and biocompatibility of a gentamicin-loaded Fe3O4/carbonated hydroxyapatite coating

Postoperative implant-associated infection remains a serious complication in total joint arthroplasty (TJA) surgery. The addition of antibiotics to bone cement is used as an antimicrobial prophylaxis in cemented joint arthroplasty; however, in cementless arthroplasty, there are no comparable measures for the local delivery of antibiotics. In this study, a gentamicin-loaded Fe3O4/carbonated hydroxyapatite coating (Gent-MCHC) was fabricated according to the following steps: (i) deposition of Fe3O4/CaCO3 particles on Ti6Al4V substrates by electrophoretic deposition; (ii) conversions of MCHC from Fe3O4/CaCO3 coatings by chemical treatment; and (iii) formation of Gent-MCHC by loading gentamicin into MCHC. MCHC possessed mesoporous structure with a pore size of about 3.8 nm and magnetic property with the saturation magnetization strength of about 4.03 emu/g. Gent-MCHC had higher drug loading efficiency and drug release capacity, and superior biocompatibility and mitogenic activity than Ti6Al4V. Moreover, Gent-MCHC deterred bacterial adhesion and prevented biofilm formation. These results demonstrate that Gent-MCHC can be used as a local drug delivery system to prevent implant-associated infection in TJA surgery.

The effects of hydroxyapatite nano whiskers and its synergism with polyvinylpyrrolidone on poly(vinylidene fluoride) hollow fiber ultrafiltration membranes

By introducing hydroxyapatite (HAP) nano whiskers as well as polyvinylpyrrolidone (PVP), poly(vinylidene fluoride) (PVDF)/PVP/HAP hollow fiber membranes were fabricated with the wet spinning method. The aqueous solution containing 90 wt% N-methyl-2-pyrrolidone (NMP) is used as bore liquid. The effects of two additives and the synergism on the morphologies, surface properties, permeation performances, antifouling ability and mechanical properties of the PVDF/PVP/HAP membranes were characterized by numerous state-of-the-art analytical techniques, and reasonably elucidated accompanying with precipitation kinetics and shear viscosity of dopes. The results show that with the addition of HAP, the finger-like structure of PVDF/PVP/HAP membranes is gradually suppressed and replaced by sponge-like structure, and the hydrophilicity is evidently improved. The hydraulic permeability Jw firstly increases from 224.2 of M-1 to 549.1 L M−2 H−1 bar−1 by adding 1.0 wt% HAP nano whiskers of M-2, and then decreases to 425.9 and 316.3 L M−2 H−1 bar−1 for M-3 and M-4. The rejections of three proteins and humic acid range from 31.4% to 98.4%, and slightly decrease as HAP content increases in the membranes. The mechanical properties of the membranes are markedly improved with the addition of HAP nano whiskers. The membranes containing dual additives have higher permeability and mechanical strength than those of the fibers containing either single additive, implying the synergism of them in improving membrane properties.

Hydrophilic modification of polyvinyl chloride hollow fiber membranes by silica with a weak in situ sol–gel method

A weak in situ sol–gel method is proposed for the hydrophilic modification of polyvinyl chloride (PVC) hollow fiber membranes by silica, which is generated by the soft hydrolysis of tetraethoxysilane (TEOS) in a deionized water bath. The silica is uniformly distributed on the membrane surface. The sponge-like structure of the modified PVC membranes becomes thicker with the addition of TEOS. The surface hydrophilicity of the membranes gradually increases due to the introduction of silica. The hydraulic permeability increases from 34.8 L M−2 H−1 bar−1 to 89.1 L M−2 H−1 bar−1, and then decreases to 45.3 L M−2 H−1 bar−1 for the membranes of M0(1,3,5)E50 with the addition of TEOS from 0 to 5 wt% in dope content when 50 wt% ethanol aqueous solution is used as the bore liquid. A similar tendency is found for the membranes M0(1,3,5)D95 with 95 wt% DMAc aqueous solution as the bore liquid. The anti-fouling experiments illustrate that the membranes with the addition of TEOS show higher anti-fouling ability. Moreover, the mechanical properties of PVC membranes are also enhanced with the introduction of silica. This work demonstrates that PVC inorganic–organic composite hollow fiber membranes are prepared by a weak in situ sol–gel method, which avoids the use of corrosive substances during membrane preparation.

Catalytic performance of gallium oxide based-catalysts for the propane dehydrogenation reaction: effects of support and loading amount

The different materials (ZSM-5, SBA-15, γ-Al2O3 and SiO2) were used as supports for Ga2O3-based catalysts for the propane dehydrogenation reaction, and the effect of Ga2O3 content (1–9 wt%) for xGa2O3/SBA-15 catalysts on the catalytic activity was discussed. It is found that the supports determine the porous features, the state and dispersion of Ga species, and the acid–base properties of the corresponding catalysts. The existence of strong acid sites in catalyst can lead to more well-dispersed Ga species. The satisfied catalytic performances are obtained over 5Ga2O3/ZSM-5 and 5Ga2O3/SBA-15 catalysts. Among the Ga2O3-based catalysts with different supports, the 5Ga2O3/ZSM-5 sample exhibits the highest catalytic activity, which possesses the maximum well-dispersed gallium species and high dehydrogenation efficiency gallium ions (Gaδ+ cations, δ < 2), and the 5Ga2O3/SBA-15 catalyst exhibits the highest catalytic stability. Furthermore, as for the xGa2O3/SBA-15 samples, the 5Ga2O3/SBA-15 sample exhibits the best catalytic performance. The initial propane conversion and propylene selectivity are above 32.0% and 90.0% respectively, and a final propane conversion of 17.0% is obtained after 30 h reaction. With the increase of Ga loading, the Ga species are easily agglomerated and destroy the structural integrity of the SBA-15 support, which is unfavorable to the propane dehydrogenation reaction.

Emulsion fabrication of magnetic mesoporous carbonated hydroxyapatite microspheres for treatment of bone infection

Hydroxyapatite is widely used for bone filling materials because of its compositional similarities to bone mineral and excellent biocompatibility, but it does not possess good osteoinductivity and bactericidal properties. Herein, magnetic mesoporous carbonated hydroxyapatite microspheres (MEHMs) have been fabricated using CaCO3/Fe3O4 microspheres as sacrificial templates. The cetyltrimethylammonium bromide/Na2HPO4 solution/cyclohexane/n-butanol emulsion system serves as a microreactor, in which the CaCO3/Fe3O4 microspheres are converted to MEHMs via a dissolution–precipitation reaction. MEHMs with low crystallinity exhibit the hierarchical nanostructures constructed by nanoplates as building blocks with mesopores and macropores, which give them high drug loading–release properties. The controlled release of gentamicin significantly minimizes bacterial adhesion and prevents biofilm formation against S. epidermidis. The Fe3O4 nanoparticles are dispersed within the microspheres, which makes the MEHMs magnetic. The biocompatibility and osteoinductivity of the MEHMs have been investigated using human bone marrow stromal cells (hBMSCs) as cell models. The Fe3O4 nanoparticles in the MEHMs not only stimulate cell adhesion and proliferation, but also promote the osteogenic differentiation of hBMSCs. The excellent biocompatibility, osteoinductivity, drug loading–release properties and bactericidal properties give the MEHMs great potential as bone filling materials to treat bone infection.