Qiaoling Huang

Reduced platelet adhesion and improved corrosion resistance of superhydrophobic TiO2-nanotube-coated 316L stainless steel

Superhydrophilic and superhydrophobic TiO2 nanotube (TNT) arrays were fabricated on 316L stainless steel (SS) to improve corrosion resistance and hemocompatibility of SS. Vertically-aligned superhydrophilic amorphous TNTs were fabricated on SS by electrochemical anodization of Ti films deposited on SS. Calcination was carried out to induce anatase phase (superhydrophilic), and fluorosilanization was used to convert superhydrophilicity to superhydrophobicity. The morphology, structure and surface wettability of the samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and contact angle goniometry. The effects of surface wettability on corrosion resistance and platelet adhesion were investigated. The results showed that crystalline phase (anatase vs. amorphous) and wettability strongly affected corrosion resistance and platelet adhesion. The superhydrophilic amorphous TNTs failed to protect SS from corrosion whereas superhydrophobic amorphous TNTs slightly improved corrosion resistance of SS. Both superhydrophilic and superhydrophobic anatase TNTs significantly improved corrosion resistance of SS. The superhydrophilic amorphous TNTs minimized platelet adhesion and activation whereas superhydrophilic anatase TNTs activated the formation of fibrin network. On the contrary, both superhydrophobic TNTs (superhydrophobic amorphous TNTs and superhydrophobic anatase TNTs) reduced platelet adhesion significantly and improved corrosion resistance regardless of crystalline phase. Superhydrophobic anatase TNTs coating on SS surface offers the opportunity for the application of SS as a promising permanent biomaterial in blood contacting biomedical devices, where both reducing platelets adhesion/activation and improving corrosion resistance can be effectively combined.

Effect of construction of TiO2 nanotubes on platelet behaviors: Structure-property relationships

Blood compatibility of TiO2 nanotubes (TNTs) has been assessed in rabbit platelet-rich plasma (PRP), which combines activation of both blood plasma coagulation and platelets. We find that (i) amorphous TiO2 nanotubes (TNTs) with relatively larger outer diameters led to reduced platelet adhesion/activation, (ii) TNTs with relatively smaller outer diameters in a predominately rutile phase also inhibited platelet adhesion and activation, and (iii) a pervasive fibrin network formed on larger outer diameter TNTs in a predominately anatase phase. Thus, this study suggests that combined effect of crystalline phase and surface chemistry controls blood-contact behavior of TNTs. A more comprehensive mechanism is proposed for understanding hemocompatibility of TiO2 which might prove helpful as a guide to prospective design of TiO2-based biomaterials. STATEMENT OF SIGNIFICANCE To realize optimal design and construction of biomaterials with desired properties for blood contact materials, a comprehensive understanding of structure-property relationships is required. In the existing literature, TiO2 nanotube has been reported to be a good candidate for biomedical applications. However, it is noticeable that the blood compatibility of TiO2 nanotubes (TNTs) remains obscure or even inconsistent in the previously published works. The inconsistency could derive from different research protocols, material properties or blood sources. Thus, a thorough investigation of the effect of surface properties on blood compatibility is crucial to the development of titanium based materials. In this paper, we explored the effect of surface properties on the response of platelet-rich plasma, especially surface morphology, chemistry, wettability and crystalline phase. The results indicated that crystalline phase was a dominant factor in platelet behaviors. Reduced adhesion and activation of platelets were observed on amorphous and rutile dominated TNTs, whereas anatase dominated TNTs activated the formation of fibrin network. We further proposed a hypothetical mechanism for better understanding of how surface properties affect the response of platelet-rich plasma. Therefore, this study expands the fundamental understanding of the structure-property relationships of titanium based materials.

Antibacterial and cytocompatible AgNPs constructed with the assistance of Mefp-1 for orthopaedic implants

The increasing threat of orthopedic implant failure caused by infection and loosening intensifies the need for novel surface functional treatment. In this study, a thin mussel adhesive protein (Mefp-1)/silver nanoparticle (AgNP) composite film constructed on titania nanotubes (TNTs) via a simple dip-coating method has been demonstrated. The TNT/Mefp-1/AgNP coating exhibits both high antibacterial activity and adequate cytocompatibility. The adherent Mefp-1 film could promote preosteoblast proliferation and reduce AgNP-induced cytotoxicity. The AgNPs (∼10 nm) constructed with the assistance of Mefp-1 are effective for the elimination of both Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) via a combination of contact-killing and release-killing modes. This facile and mild functionalization strategy exhibits promising applications in surface antibacterial modifications, especially in three-dimensional sophisticated medical devices.

Seeded Mineralization Leads to Hierarchical CaCO3 Thin Coatings on Fibers for Oil/Water Separation Applications

Like their biogenic counterparts, synthetic minerals with hierarchical architectures should exhibit multiple structural functions, which nicely bridge the boundaries between engineering and functional materials. Nevertheless, design of bioinspired mineralization approaches to thin coatings with distinct micro/nanotextures remains challenging in the realm of materials chemistry. Herein, a general morphosynthetic method based on seeded mineralization was extended to achieve prismatic-type thin CaCO3 coatings on fibrous substrates for oil/water separation applications. Distinct micro/nanotextures of the overlayers could be obtained in mineralization processes in the presence of different soluble (bio)macromolecules. These hierarchical thin coatings therefore exhibit multiple structural functions including underwater superoleophobicity, ultralow adhesion force of oil in water, and comparable stiffness/strength to the prismatic-type biominerals found in mollusk shells. Moreover, this controllable approach could proceed on fibrous substrates to obtain robust thin coatings, so that a modified nylon mesh could be employed for oil/water separation driven by gravity. Our bioinspired approach based on seeded mineralization opens the door for the deposition of hierarchical mineralized thin coatings exhibiting multiple structural functions on planar and fibrous substrates. This bottom-up strategy could be readily extended for the syntheses of advanced thin coatings with a broad spectrum of engineering and functional constituents.

Silk/agarose scaffolds with tunable properties via SDS assisted rapid gelation

Scaffolds with appropriate properties and a suitable shape based on the nature of the target tissue are essential in tissue engineering. In the present study, we developed a simple method to fabricate lyophilized silk/agarose scaffolds with tunable features (mechanical properties and pore structure) via controlling the gelation degree of silk fibroin and freeze-drying the gels with different gelation degrees. Sodium dodecyl sulfate (SDS) was utilized to control the gelling process of silk. Agarose helped retain the shape of the scaffolds after hydration and sterilization. Moreover, the scaffolds could be easily realized with the desired shape for specific applications by shaping the corresponding gels. The compressive modulus of the scaffolds was tunable within a range of 18.6–58.8 kPa, and inner pore sizes could be tuned from 52.3 ± 10.4 to 426.5 ± 138.5 μm. In vitro MC3T3-E1 cell proliferation indicated good biocompatibility of the silk/agarose scaffolds. Alkaline phosphatase (ALP) activity assay and mineralization analysis indicated that scaffolds with higher mechanical properties were more beneficial for osteogenic differentiation and mineralization. Thus, silk/agarose scaffolds are promising candidates for tissue engineering.