Pro-endothelialization of nitinol alloy cardiovascular stents enhanced by the programmed assembly of exosomes and endothelial affinity peptide.

Stent implantation is one of the most effective methods for the treatment of atherosclerosis. Nitinol stent is a type of stent with good biocompatibility and relatively mature development; however, it cannot effectively achieve long-term anticoagulation and early endothelialization. In this study, nitinol surfaces with the programmed assembly of heparin, exosomes from endothelial cells, and endothelial affinity peptide (REDV) were fabricated through layer-by-layer assembly technology and click-chemistry, and then exosomes/REDV-modified nitinol interface (ACC-Exo-REDV) was prepared. ACC-Exo-REDV could promote the rapid proliferation and adhesion of endothelial cells and achieve anticoagulant function in the blood. Besides, ACC-Exo-REDV had excellent anti-inflammatory properties and played a positive role in the transformation of macrophage from the pro-inflammatory to anti-inflammatory phenotype. Ex vivo and in vivo experiments demonstrated the effectiveness of ACC-Exo-REDV in preventing thrombosis and hyperplasia formation. Hence, the programmed assembly of exosome interface could contribute to endothelialization and have potential application on the cardiovascular surface modification to prevent stent thrombosis and restenosis.

Flaw-insensitive fatigue resistance of chemically fixed collagenous soft tissues.

Bovine pericardium (BP) has been used as leaflets of prosthetic heart valves. The leaflets are sutured on metallic stents and can survive 400 million flaps (~10-year life span), unaffected by the suture holes. This flaw-insensitive fatigue resistance is unmatched by synthetic leaflets. We show that the endurance strength of BP under cyclic stretch is insensitive to cuts as long as 1 centimeter, about two orders of magnitude longer than that of a thermoplastic polyurethane (TPU). The flaw-insensitive fatigue resistance of BP results from the high strength of collagen fibers and soft matrix between them. When BP is stretched, the soft matrix enables a collagen fiber to transmit tension over a long length. The energy in the long length dissipates when the fiber breaks. We demonstrate that a BP leaflet greatly outperforms a TPU leaflet. It is hoped that these findings will aid the development of soft materials for flaw-insensitive fatigue resistance.

[In vivo and in vitro studies on anode-oxidized titanium percutaneous implants].

In order to solve the problesm in biological sealing of load-bearing percutaneous implants for a fairly long time, we investigated titanium with bioactivated anodic oxidized surface(group A) through the animal tests in vivo and the epithelium cell culture in vitro. Smooth Ti (group B) was used as control. The animal tests results showed that there was no evident difference in the inflammory reaction between the group A implant tissues and the group B implant/tissues. The bioactivated Ti surface could keep the implant not only bonding with the bone firmly but also adhering to the soft tissue closely, thus contributing to the formation of calcium phosphate layer and its micropores. The cell culture results also demonstrated that the microporous surface of group A could clasp and fix the skin. So, it can be concluded that the surface modified method of anode oxidization may be one of the most effective methods to resolve the problem of durable biological sealing.

An atomistic-based chemophysical environment for evaluating asphalt oxidation and antioxidants.

Asphalt binders in service conditions are subject to oxidative aging that involves the reactions between oxygen molecules and the component species of bulk asphalt. As a result, significant alterations can occur to the desired physical and/or mechanical properties of asphalt. A common practice to alleviate asphalt aging has been to employ different chemical additives or modifiers as antioxidants. The current state of knowledge in asphalt oxidation and antioxidant evaluation is centered on determining the degradation of asphalt physical properties, mainly the viscosity and ductility. Such practices, although meeting direct engineering needs, do not contribute to the fundamental understanding of the aging and anti-oxidation mechanisms, and thereby developing anti-aging strategies. From this standpoint, this study was initiated to study the chemical and physical bases of asphalt oxidation, as well as the anti-oxidation mechanisms of bio-based antioxidants using the coniferyl-alcohol lignin as an example. A quantum chemistry (QC) based chemophysical environment is developed, in which the various chemical reactions between asphalt component species and oxygen, as well as the incurred physical changes are studied. X-ray photoelectron spectroscopy (XPS) was used to validate the modified and unmodified asphalt models.

Preparation and biocompatibility of nanohybrid scaffolds by in situ homogeneous formation of nano hydroxyapatite from biopolymer polyelectrolyte complex for bone repair applications.

The achievement of nano distribution for inorganic reinforced filler is a big challenge to three-dimensional porous composite scaffolds. In this paper, a homogeneous nano hydroxyapatite/polyelectrolyte complex (HAP/PEC) hybrid scaffold was developed and investigated. Based on the enhancing properties of the formation of PEC between chitosan and hyaluronic acid, the introduction of nano HAP via in situ crystallization from the PEC achieved nano distribution in the PEC matrix and supplied nano topographies of extracellular environments for the nanohybrid scaffold. The biocompatibility and bioactivity were evaluated by Human bone mesenchymal stem cells (hBMSCs) proliferation (MTT assay), maturation (alkaline phosphatase (ALP) activity) and histological analysis. The in vitro tests show the scaffold is excellent for cell penetration, growth, and proliferation and it is promising for bone repair application.