Yuancong Zhao

A simple one-step modification of various materials for introducing effective multi-functional groups

Covalent immobilization of various biomolecules is a desired strategy for bio-multifunctional surface modification. Multi-functionalization of a material surface is considered to be the premise of immobilizing a variety of biomolecules. However, currently adopted methods, used to introduce proper reactive functional groups on material surfaces, mostly are hard to be carried out and frequently can only introduce insufficient functional groups. In this work, we successfully develop the films (GAHD films) prepared via the simple copolymerization of gallic acid (GA) and hexamethylenediamine (HD), which can be deposited on different kinds of material surfaces including metals, ceramics and polymers by a one-step dip-coating method. Moreover, these copolymerized GAHD films possess high concentration of multi-functional groups like carboxyl (COOH), primary amine (-NH2) and quinone groups on the surfaces. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) results prove either the occurrence of Michael addition reaction, Schiff base reaction in the film-forming process, or the existence of COOH, NH2 and quinone groups on the surfaces. The maximum contents of carboxyl and amine on the GAHD film are 24.9 nmol/cm(2) and 31.7 nmol/cm(2) respectively. After dynamical immersion for 30 days, slight swellings can be observed, which reveals that the GAHD films possess good stability. Moreover, Heparin (Hep), fibronectin (Fn) and laminin (Ln) are successfully immobilized on the GAHD film surfaces. The results of cell counting kit-8 (CCK-8) and rhodamine fluorescence photograph indicate that the 1:1.62 GAHD film has good cytocompatibility.

Biofunctionalization of titanium with PEG and anti-CD34 for hemocompatibility and stimulated endothelialization

Thrombosis and restenosis are the main causes of failure of cardiovascular and other blood-contacting biomedical devices. It is recognized that rapid endothelialization is a promising method for preventing these complications. Convincing evidence in vivo has further emerged that the vascular homing of endothelial progenitor cells (EPCs) contributes to rapid endothelial regeneration. This study deals with improving the hemocompatibility and enhancing EPC colonization of titanium by covalently bonding PEG(600) or PEG(4000), then end-grafting of an anti-CD34 antibody. For this, a chemically hydroxylated titanium surface was aminosilanized, which was further used for covalent grafting of polyethylene glycol and the antibody. The grafting efficiency was verified in each step. In vitro platelet adhesion analysis confirmed superior hemocompatibility of the modified surface over the control. Affinity of EPC to the surface and inhibition of smooth muscle cell adhesion, two prerequisites for endothelialization, are demonstrated in in vitro cell culture. While the coating selectively stimulates EPC adhesion, its antifouling properties prevent formation of an extracellular matrix and proliferation of the cells. Additional affinity for matrix proteins in the coating is considered for further studies. Potent inhibitory effect on macrophage activation and the relative stability of the coating render this technique applicable.

Guidance of Stem Cells to a Target Destination in Vivo by Magnetic Nanoparticles in a Magnetic Field

Stem cells contribute to physiological processes such as postischemic neovascularization and vascular re-endothelialization, which help regenerate myocardial defects or repair vascular injury. However, therapeutic efficacy of stem cell transplantation is often limited by inefficient homing of systemically administered cells, which results in a low number of cells accumulating at sites of pathology. In this study, anti-CD34 antibody-coated magnetic nanoparticles (Fe3O4@PEG-CD34) are shown to have high affinity to stem cells. The results of hemolysis rate and activated partial thromboplastin time (APTT) tests indicate that such nanoparticle may be used safely in the blood system. In vitro studies showed that a nanoparticle concentration of 100 μg/mL gives rise to a significant increase in cell retention using an applicable permanent magnet, exerting minimal negative effect on cell viability and migration. Subsequent in vivo studies indicate that nanopartical can specifically bind stem cells with good magnetic response. Anti-CD34 antibody coated magnetic nanoparticle may be used to help deliver stem cells to a lesion site in the body for better treatment.

A facile approach for the synthesis of highly luminescent carbon dots using vitamin-based small organic molecules with benzene ring structure as precursors

In this study, vitamin-based small organic molecules were used as precursors to synthesize carbon dots by means of a hydrothermal approach. The obtained carbon dots presented high luminescence and good cellar-imaging properties when folic acid was used as a precursor and the quantum yield of the carbon dots obtained using the present method was more than 30%. Moreover, green and yellow-green photoluminescence was also successfully achieved by adding the reagents H3PO4 and H2C2O4, respectively. The related formation mechanism and photoluminescence emission mechanism of carbon quantum dots were discussed. The present study will open a new possible route for the synthesis of carbon dots with high quality using small organic molecules as precursors.

A dual-task design of corrosion-controlling and osteo-compatible hexamethylenediaminetetrakis- (methylene phosphonic acid) (HDTMPA) coating on magnesium for biodegradable bone implants application

Magnesium as well as its alloys appears increasingly as a revolutionary bio-metal for biodegradable implants application but the biggest challenges exist in its too fast bio-corrosion/degradation. Both corrosion-controllable and bio-compatible Mg-based bio-metal is highly desirable in clinic. In present work, hexamethylenediaminetetrakis (methylenephosphonic acid) [HDTMPA, (H2 O3 P-CH2 )2 -N-(CH2 )6 -N-(CH2 -PO3 H2 )2 ], as a natural and bioactive organic substance, was covalently immobilized and chelating-deposited onto Mg surface by means of chemical conversion process and dip-coating method, to fullfill dual-task performance of corrosion-protective and osteo-compatible functionalities. The chemical grafting of HDTMPA molecules, by participation of functional groups on pretreated Mg surface, ensured a firmly anchored base layer, and then sub-sequential chelating reactions of HDTMPA molecules guaranteed a homogenous and dense HDTMPA coating deposition on Mg substrate. Electrochemical corrosion and immersion degradation results reveal that the HDTMPA coated Mg provides a significantly better controlled bio-corrosion/degradation behavior in phosphate buffer saline solution as compared with untreated Mg from perspective of clinic requirement. Moreover, the HDTMPA coated Mg exhibits osteo-compatible in that it induces not only bioactivity of bone-like apatite precipitation but also promotes osteoblast cells adhesion and proliferation. Our well-controlled biodegradable and biocompatible HDTMPA modified Mg might bode well for next generation bone implant application.

Fabrication and Superconducting Properties of Rod‐In‐Tube Multifilamentary Nb 3 Al Wire With Rapid Heating and Quenching Heat‐Treatment

In this paper, we reported the recent progress in developing practical kilometer-length rod-in-tube (RIT) multifilamentary Nb₃Al superconducting wires at WST, which included the preparation of Cu/Nb-Al precursor wires, design and manufacture of rapid heating and quenching (RHQ) equipment, and RHQ heat-treatment process of Nb₃Al wires. Superconducting properties and microstructure of the RIT Nb₃Al wires have been discussed. By measuring magnetization and transport critical current properties of Nb₃Al wires, it is found that, for all the samples, the onset superconducting transition temperature T_c reaches 16.8-17.3 K, and at 4.2 K and 15 T, the critical current density J_c of 830 A/mm² at the Nb₃Al wires have been achieved. This paper suggests that it is possible to develop the practical Nb₃Al superconducting wires by using the RIT Nb₃Al precursor wires, in combination with RHQ heat-treatment process.

Controlling the corrosion rate and behavior of biodegradable magnesium by a surface-immobilized ultrathin 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) film

An ultrathin bisphosphonate film, 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), was deposited on magnesium for biodegradable implant applications. The small, bioactive HEDP molecule is supposed to be not only bio-safe, but also favorable for creating a highly protective layer for the control of the corrosion/degradation of Mg. In an in situ chemical sequence, the HEDP molecules were covalently surface-immobilized on the alkaline pretreated Mg and then spontaneously deposited by participation in a chelating reaction with Mg ions. An organometallic-like compound layer was thus formed, which was ascertained to be within the nanoscale and complied well with the substrate. The tape test showed that the HEDP film provides excellent adhesion strength. Electrochemical corrosion and in vitro immersion degradation investigations demonstrated that the HEDP coated Mg exhibited significantly slower corrosion rate than untreated Mg in phosphate buffered saline (PBS) solution. Of particular significance is the observation that HEDP coated Mg presented a remarkably suppressed localized corrosion mode. The meliorated corrosion/degradation behavior is credited to both the nature of the organometallic-like HEDP derivative layer, as well as the high quality of the film, with respect to compactness and homogeneity. Our HEDP modified Mg may bode well for application in biodegradable implants.

An injectable supramolecular self-healing bio-hydrogel with high stretchability, extensibility and ductility, and a high swelling ratio

Reversible networks are a key factor for designing self-healing hydrogels with high stretching properties. To achieve that, it is often necessary to modify or graft functional groups to the main chains for inducing the formation of reversible covalent-bond-based chemical cross-linking or hydrogen-bond-based physical cross-linking, thus leading to a complicated chemical process and high cost. Here, we proposed a dynamic sliding physical crosslinking mechanism of chains to design and synthesize hydrogels with both good self-healing ability and extensibility by introducing interstitial phases of small organic molecules into the hydrogel networks to enhance hydrogen bonds, which has been proved to be a quite facile and practical approach to achieve stretchable and self-healing properties. Our work might greatly promote our ability to understand the role of hydrogen bonds that are often overlooked in the design of materials. The as-synthesized hydrogels displayed extraordinary swelling properties with a swelling ratio of 2750% in PBS and of nearly 10 000% in stilled water, respectively, and they also showed excellent performance after many stress cycles under 95% compressive deformation. The use of 10% diethylene glycol could allow the elongation to be increased from 238% to 2705%. Our cell and animal experimental studies indicated that the as-synthesized supramolecular hydrogels have good biocompatibility and bioactivity and show potential for clinical application.

Multifunctional coating based on EPC-specific peptide and phospholipid polymers for potential applications in cardiovascular implants fate

Surface biofunctional modification of cardiovascular implants via the conjugation of biomolecules to prevent thrombosis and restenosis formation and to accelerate endothelialization has attracted considerable research interest. In this study, we aimed to develop a multifunctional surface that could exhibit good hemocompatibility and function well in inducing desirable vascular cell-material interactions. The multifunctional coating (PCDLOPTPT@Ti), containing phosphorylcholine groups and endothelial progenitor cell (EPC)-specific peptides (PT), was prepared on titanium (Ti) surfaces via chemical conjugation. The results of platelet adhesion, activation, fibrinogen denaturation, and whole blood dynamic adhesion testing indicated that the PCDLOPTPT@Ti coating presented a better hemocompatibility when compared with bare Ti and other control samples. In vitro EPC and smooth muscle cell (SMC) cultures showed that the PCDLOPTPT@Ti coating significantly promoted the adhesion and proliferation of EPCs and inhibited the attachment and proliferation of SMCs. In vivo animal tests further confirmed that the PCDLOPTPT@Ti coating effectively inhibited thrombus formation and intimal hyperplasia while supporting endothelium regeneration. These results effectively suggest that the PCDLOPTPT@Ti coating may be promising as a coating on cardiovascular implants.

Biocompatibility studies of poly(ethylene glycol)–modified titanium for cardiovascular devices

The rapid protein adsorption on a material surface causes blood coagulation, platelet activation, and complement system activation, which poses a risk for failure of cardiovascular devices. In this study, a chemically hydroxylated titanium surface was aminosilanized and covalently grafted with poly(ethylene glycol). The reaction conditions on the grafted quantity were studied by the respective amine and carboxyl densities. The blood compatibility of the PEGylated surfaces with different poly(ethylene glycol) densities and chain lengths was evaluated; the PEGylated surfaces with higher grafted density and longer chain length had less fibrinogen adsorption, less fibrinogen γ-chain exposed, less adherent platelets, and lower activation of the adherent platelets. In addition to the influence on blood, the longer chain PEGylated surfaces resisted, not only smooth muscle cell attachment and proliferation, but also macrophage attachment and death. This method is a good candidate for improving cardiovascular implant surfaces.