Aggregation of fullerene (C_(60)) nanoparticle:A molecular-dynamic study

We present the results of molecular dynamics simulations of net positively charged fullerene nanoparticles in salt- free and salt-added solution. The aggregation of fullerene （C60）-like nanoparticle and counterion are studied in detail as a function of temperatures and a finite salt concentration. Our simulations show that the strong conformation changes as temperature changes. The net positively-charged nanoparticles do not repel each other but are condensed under proper temperatures. If salts are added, the aggregated nanoparticles will be disaggregated due to the Debye screening effect.

Entropy dominated behaviors of confined polymer-nanoparticle composites

Stretched polymers will lose their possible configurations if they are mixed with nanoparticles or touch a hard wall, which leads to a strong depletion attraction responsible for the enrichment of nanoparticles near substrates. Moreover, it is found that there exists a sacrifice mechanism in confined pure polymer samples or polymer-nanoparticle mixtures, that part of the polymers, in order to reach a minimum free energy for the total system, are adsorbed on hard walls even though they lose their conformation. The current study provides a simple yet effective approach for the design of thin polymer composites.

In vitro Response of Human Mesenchymal Stromal Cells to Titanium Coated Peek Films and Their Suitability for Magnetic Resonance Imaging

Medical imaging is an important tool for the post-operative checkup of an accurate position of an implant as well as for monitoring the integration in the adjacent tissue that may influence the success of a medical device.Unfortunately,the possibility to use imaging methods is associated with the implant material and all the established metallic materials for surgery do not show a proper 'imaging compatibility'.The present study is a combined investigation of the in vitro response to human mesenchymal stromal cells（hMSC） and magnetic resonance imaging（MRI） compatibility of the potential material combination polyetheretherketone/titanium（PEEK/Ti） for medical devices.Because of the advantageous imaging properties and the mechanical and chemical stability,PEEK becomes more and more an alternative to common metallic implant materials like titanium or cobalt-chrome.However,PEEK is a bioinert material having a limited ability for direct bone incorporation.Due to its excellent biocompatibility,Ti was chosen as coating material to enhance the cellular response.The result is a combination with advantageous properties:the magnetic susceptibility and elastic modulus close to bone,corrosion resistance and mechanical flexibility of PEEK and the excellent biocompatibility of titanium.The appearance of metal-related artifact was discussed in electrical resistivity and magnetic susceptibility.Therefore,two titanium coatings have been investigated:a complete coating and a structured surface avoiding surface conductivity.To determine the in vitro biocompatibility,the cell responses were assessed in terms of the overall morphology of the hMSC and their cell area distribution,proliferation,osteogenic differentiation and mineral deposition.The cellular stress was evaluated by the prostaglandin E2level.The bonded materials both produced no disturbing artifacts in magnetic resonance imaging.Compared to the pure PEEK material,the titanium coated specimens showed an enhanced biocompatibility,which is indicated by a higher cell number,larger activity of the enzyme tissue non-specific alkaline phosphatase and therefore a greater amount of deposited calcium and phosphate.The results on bare PEEK are accompanied with a higher cellular stress level,which is indicated by prostaglandin E2.