A multifunctional cascade bioreactor based on a layered double oxides composite hydrogel for synergetic tumor chemodynamic/starvation/photothermal therapy.

The field of nanomedicine-catalyzed tumor therapy has achieved a lot of progress; however, overcoming the limitations of the tumor microenvironment (TME) to achieve the desired therapeutic effect remains a major challenge. In this study, a nanocomposite hydrogel (GH@LDO) platform combining the nanozyme CoMnFe-layered double oxides (CoMnFe-LDO) and natural enzyme glucose oxidase (GOX) was engineered to remodel the TME to enhance tumor catalytic therapy. The CoMnFe-LDO is a nanozyme that can convert endogenous H2O2 into reactive oxygen species (ROS) and O2 to achieve chemodynamic therapy (CDT) and alleviate the hypoxic microenvironment. Meanwhile, GOX can catalyze the conversion of glucose and O2 to gluconic acid and H2O2, which not only represses the ATP production of tumor cells to achieve starvation therapy (ST), but also decreases the pH value of TME and supplies extra H2O2 to enhance the CDT effect. Furthermore, this well-designed CoMnFe-LDO possessed a high photothermal conversion efficiency of GH@LDO (66.63%), which could promote the generation of ROS to enhance the CDT effect and achieve photothermal therapy (PTT) under near-infrared light irradiation. The GH@LDO hydrogel performes cascade reaction which overcomes the limitation of the TME and achieves satisfactory CDT/ST/PTT synergetic effects in vitro and in vivo. This work provides a new strategy for remodeling the TME using nanomedicine to achieve precise tumor cascaded catalytic therapy. STATEMENT OF SIGNIFICANCE: At present, the focus of tumor therapy has begun to shift from monotherapy to combination therapy for improving the overall therapeutic effect. In this study, we synthesized a CoMnFe-LDO nanozyme composed of multiple transition metal oxides, which demonstrated improved peroxidase and oxidase activities as well as favorable photothermal conversion capability. The CoMnFe-LDO nanozyme was compounded with an injectable GH hydrogel crosslinked by GOX and horseradish peroxidase (HRP). This nanocomposite hydrogel overcame the limitations of weak acidity, H2O2, and O2 levels in the TME and achieved synergetic CDT, ST, and PTT effects based on the cascaded catalytic actions of CoMnFe-LDO and GOX to H2O2 and glucose.

Improved in vitro angiogenic behavior of human umbilical vein endothelial cells with oxidized polydopamine coating.

Mussel inspired polydopamine (PDA) coatings have attracted a great deal of attention for their superior osteogenic property. Furthermore, recent investigations have demonstrated that vessel formation is crucial to bone regeneration. Hence, in the present study, the potential ability of polydopamine coatings with different oxidation degrees were systematically investigated in vitro to improve the angiogenic behavior of human umbilical vein endothelial cells (HUVECs). PDA was first coated on titanium (PDA-1#), and then oxidized by thermal treatment at 150 (PDA-2#) and 300 °C (PDA-3#), respectively. X-ray photoelectron spectroscopy (XPS) results revealed that phenolic hydroxyl (C-OH) and primary amino group (-NH2) on PDA coatings deceased after oxidation, while quinone (C=O) increased. In vitro cell culture experiments suggested that PDA-2# sample was most beneficial for the adhesion, migration, and proliferation of HUVECs. Furthermore, HUVECs cultured on PDA-2# sample also exhibited best tube formation, CD31 expression, vascular endothelial growth factor (VEGF) secretion, as well as angiogenic-associated gene expression abilities. Our study suggests that moderate oxidation of PDA coating with balanced quinone and amino group has excellent potential to enhance bone vascularization, and is thus promising for clinical application in orthopedic implants.

Smart release of doxorubicin loaded on polyetheretherketone (PEEK) surface with 3D porous structure.

It is important to fabricate an implant possessing environment sensitive drug delivery. In this work, the construction of 3D porous structure on polyetheretherketone (PEEK) surface and pH sensitive polymer, chitosan, was introduced. The smart release of doxorubicin can be realized on the 3D porous surface of PEEK loading chitosan. We give a feasible explanation for the effect of chitosan on smart drug release according to Henderson-Hasselbalch equation. Furthermore, the intracellular drug content of the cell cultured on the samples with highest chitosan is significantly higher at pH 4.0, whereas lower at pH 7.4 than other samples. The smart release of doxorubicin via modification with chitosan onto 3D porous PEEK surface paves the way for the application of PEEK in drug loading platform for recovering bone defect caused by malignant bone tumor.

Layer-Number Dependent Antibacterial and Osteogenic Behaviors of Graphene Oxide Electrophoretic Deposited on Titanium.

Graphene oxide has attracted widespread attention in the biomedical fields due to its excellent biocompatibility. Herein we investigated the layer-number dependent antibacterial and osteogenic behaviors of graphene oxide in biointerfaces. Graphene oxide with different layer numbers was deposited on the titanium surfaces by cathodal electrophoretic deposition with varied deposition voltages. The initial cell adhesion and spreading, cell proliferation, and osteogenic differentiation were observed from all the samples using rat bone mesenchymal stem cells. Both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus were used to investigate the antibacterial effect of the modified titanium surfaces. Cocultures of human gingival fibroblasts (HGF) cells with Escherichia coli and Staphylococcus aureus were conducted to simulate the conditions of the clinical practice. The results show that the titanium surfaces with graphene oxide exhibited excellent antibacterial and osteogenic effects. Increasing the layer-number of graphene oxide resulted in the augment of reactive oxygen species levels and the wrinkling, which led to the antibacterial and osteogenic effects, respectively. Compared to pure titanium surface in the cells-bacteria coculture process, the modified titanium surfaces with graphene oxide exhibited higher surface coverage percentage of cells.

Selective Tumor Cell Inhibition Effect of Ni-Ti Layered Double Hydroxides Thin Films Driven by the Reversed pH Gradients of Tumor Cells.

Nitinol is widely fabricated as stents for the palliation treatment of many kinds of cancers. It is of great importance to develop nitinol stents with selective tumor cell inhibition effects. In this work, a series of pH sensitive films composed of Ni(OH)2 and Ni-Ti layered double hydroxide (Ni-Ti LDH) with different Ni/Ti ratios were prepared on the surface of nitinol via hydrothermal treatment. The films with specific Ni/Ti ratios would release a large amount of nickel ions under acidic environments but were relatively stable in neutral or weak alkaline medium. Cell viability tests showed that the films can effectively inhibit the growth of cancer cells but have little adverse effects to normal cells. Besides, extraordinarily high intracellular nickel content and reactive oxygen species (ROS) level were found in cancer cells, indicating the death of cancer cells may be induced by the excessive intake of nickel ions. Such selective cancer cell inhibition effect of the films is supposed to relate with the reversed pH gradients of tumor cells.

CVD Growth of Graphene on NiTi Alloy for Enhanced Biological Activity.

From the perspective of surface modification of biomaterials, graphene is very promising because of its unique physical and chemical properties. Herein, we report direct in situ fabrication of graphene on nitinol (NiTi) shape memory alloy by chemical vapor deposition (CVD) and investigate both the growth mechanism as well as surface bioactivity of the modified alloy. Growth of the graphene layer is independent of Ni but is rather correlated with the formation of the TiC phase on the surface. Graphene nucleates and grows on this carbide layer during exposure to CH4. The graphene layer is observed to promote the osteogenesis differentiation of mesenchymal stem cells and surface bioactivity. The use of graphene as a bioactive layer is a viable approach to improving the surface properties of NiTi-based dental and orthopedic implants and components.

Antimicrobial activity and cytocompatibility of Ag plasma-modified hierarchical TiO2 film on titanium surface.

To improve the antimicrobial ability and cytocompatibility of biomedical titanium implants, many efforts have been made to modify their surface topography and chemical composition. In this work, Ag plasma-modified hierarchical TiO2 film was fabricated on titanium surface via acid etching to produce micropit, hydrothermal treatment to generate TiO2 nanorod and subsequent plasma immersion ion implantation process to impregnate Ag into TiO2 surface. In view of the potential clinical applications, their antimicrobial activity, bioactivity and cytocompatibility were systematically evaluated. The hierarchical TiO2 film showed enhanced bioactivity and bacteriostatic effect on both microbes due to more negative zeta potential, constructing the first defense line against microbial adhesion by electrostatic repulsion. Addition of embedded Ag remarkably enhanced the antimicrobial efficiency toward both microbes based on Schottky contact without Ag(+) release, establishing the second defense line targeting microbial membrane. Furthermore, the addition of Ag degraded the bioactivity very little and exerted nearly no adverse or even promoted effect on MG63 cell functions, including adhesion, spreading and proliferation. This work illustrates a two-defense-line antimicrobial activity in darkness with both prior electrostatic repulsion to inhibit most microbes adhesion and posterior biocidal action to kill residual ones that luckily infiltrated through the first defense line, and provide proof of concept using both clinically relevant human pathogens. In conclusion, the Ag-embedded hierarchical TiO2 film with excellent antimicrobial activity, bioactivity and cytocompatibility provides a promising candidate for orthopedic and dental implants.

Enhanced osteoblast responses to poly ether ether ketone surface modified by water plasma immersion ion implantation.

Poly ether ether ketone (PEEK) offers a set of characteristics superior for human implants; however, its application is limited by the bio-inert surface property. In this work, PEEK surface was modified using single step plasma immersion ion implantation (PIII) treatment with a gas mixture of water vapor as a plasma resource and argon as an ionization assistant. Field emission scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy were used to investigate the microstructure and composition of the modified PEEK surface. The water contact angle and zeta-potential of the surfaces were also measured. Osteoblast precursor cells MC3T3-E1 and rat bone mesenchymal stem cells were cultured on the PEEK samples to evaluate their cytocompatibility. The obtained results show that the hydroxyl groups as well as a "ravined structure" are constructed on water PIII modified PEEK. Compared with pristine PEEK, the water PIII treated PEEK is more favorable for osteoblast adhesion, spreading and proliferation, besides, early osteogenic differentiation indicated by the alkaline phosphatase activity is also up-regulated. Our study illustrates enhanced osteoblast responses to the PEEK surface modified by water PIII, which gives positive information in terms of future biomedical applications.

Osteogenic activity and antibacterial effect of zinc ion implanted titanium.

Titanium (Ti) and its alloys are widely used as orthopedic and dental implants. In this work, zinc (Zn) was implanted into oxalic acid etched titanium using plasma immersion ion implantation technology. Scanning electron microscopy and X-ray photoelectron spectroscopy were used to investigate the surface morphology and composition of Zn-implanted titanium. The results indicate that the depth profile of zinc in Zn-implanted titanium resembles a Gaussian distribution, and zinc exists in the form of ZnO at the surface whereas in the form of metallic Zn in the interior. The Zn-implanted titanium can significantly stimulate proliferation of osteoblastic MC3T3-E1 cells as well as initial adhesion, spreading activity, ALP activity, collagen secretion and extracellular matrix mineralization of the rat mesenchymal stem cells. The Zn-implanted titanium presents partly antibacterial effect on both Escherichia coli and Staphylococcus aureus. The ability of the Zn-implanted titanium to stimulate cell adhesion, proliferation and differentiation as well as the antibacterial effect on E. coli can be improved by increasing implantation time even to 2 h in this work, indicating that the content of zinc implanted in titanium can easily be controlled within the safe concentration using plasma immersion ion implantation technology. The Zn-implanted titanium with excellent osteogenic activity and partly antibacterial effect can serve as useful candidates for orthopedic and dental implants.

Stimulation of bone growth following zinc incorporation into biomaterials.

Rapid development of zinc biology has broadened the applications of Zn-incorporated biomaterials to tissue engineering but also raised concerns about the long-term safety of released Zn(2+) ions. Clinical success hinges on the amount of incorporated zinc and subsequent optimized release sufficient to stimulate osseointegration. In this study, zinc is incorporated into the sub-surface of TiO2 coatings by plasma immersion ion implantation and deposition (PIII&D). The Zn-implanted coatings show significant improvement compared to the "bulk-doped" coatings prepared by plasma electrolyte oxidation in terms of osteogenesis in vitro and in vivo. Molecular and cellular osteogenic activities demonstrate that rBMSCs cultured on the Zn-implanted coatings have higher ALP activity and up-regulated osteogenic-related genes (OCN, Col-I, ALP, Runx2) compared to the bulk-doped Zn coatings and controls. In vivo osseointegration studies conducted for 12 weeks on the rat model show early-stage new bone formation and the bone contact ratio (12 week) on the Zn-implanted coating is larger. The ZnT1 and ZIP1 gene expression studies demonstrate that the Zn-implanted coatings can better stimulate bone growth with reduced Zn release than those doped with zinc throughout the coatings.