A flexible conductive hybrid elastomer for high-precision stress/strain and humidity detection

Flexible and environment-responsive materials are essential for a large number of applications from artificial skin to wearable devices. The present study develops a flexible, ultra-low cost conductive hybrid elastomer(CHE), which possesses high responsive capabilities to stress/strain and humidity. CHE was composed of polydimethylsiloxane(PDMS) and starch hydrogel(SH), enabling great elasticity(56 kPa),high conductivity(10^(-2)S/m) and high sensitivity to external stimuli(gauge factor of CHE under stress and strain are 0.71 and 2.22, respectively, and sensitivity to humidity is 1.2 × 10^(-6)S/m per RH%). These properties render CHE a promising candidate for artificial skin and wearable electronics applications of continuously monitoring environmental information.

Natural diatomite particles： Size-, dose- and shape- dependent cytotoxicity and reinforcing effect on injectable bone cement

Natural diatomite （DT） is the ancient deposit of diatom skeleton with many regular pores of 50-200 nm and also an abundant source of biogenic silica. Although silica is considered biologically safe and there is an increasing interest of using natural diatomite for biomedical applications, the toxicity information about natural diatomite is still missing. Here, cytotoxicity of natural diatomite on osteoblasts and fibroblasts were compared to hydroxyapatite and the relationships between cytotoxicity and diatomite sizes, dose, geometry or impurity were systematically investigated. Cell adhesion and interaction with diatomite particles were also fluorescently observed, The results clearly suggested a size-, dose- and shape-dependent cytotoxicity of natural diatomite. Disk-shaped diatomite particles with average size of 30μm in diameter revealed the least toxicity, while the diatomite particles with irregular shapes and sizes less than 10 μm were remarkably toxic. Diatomite particles with proper sizes were then selected to investigate the reinforcing effect on injectable calcium phosphate bone cement. Results showed that diatomite significantly improved the compressive strength of bone cement but did not alter the injectability of the cement, This work provided important biocompatibility information of natural diatomite and demonstrated the feasibility of using selected diatomite as bone implant material.

Antibacterial behavior and related mechanisms of martensitic Cu-bearing stainless steel evaluated by a mixed infection model of Escherichia coli and Staphylococcus aureus in vitro

Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus)are the most typical pathogenic bacteria with a significantly high risk of bio-contamination,widely existing in hospital and public places.Recent studies on antibacterial materials and the related mechanisms have attracted more interests of researchers.However,the antibacterial behavior of materials is usually evaluated separately on the single bacterial strain,which is far from the practical condition.Actually,the interaction between the polymicrobial communities can promote the growing profile of bacteria,which may weaken the antibacterial effect of materials.In this work,a 420 copper-bearing martensitic stainless steel(420 CuSS)was studied with respect to its antibacterial activity and the underlying mechanism in a co-culturing infection model using both E.coli and S.au reus.Observed via plating and counting colony forming units(CFU),Cu releasing,and material characterization,420 CuSS was proved to present excellent antibacterial performance against the mixed bacteria with an approximately 99.4%of antibacterial rate.In addition,420 CuSS could effectively inhibit the biofilm formation on its surfaces,resulting from a synergistic antibacterial effect of Cu ions,Fe ions,reactive oxygen species(ROS),and proton consumption of bacteria.

Surface energy-mediated fibronectin adsorption and osteoblast responses on nanostructured diamond

Nanostructured diamond have potential applications in many biomedical related fields and demonstrated extraordinary capacity to influence cellular responses. Studying the surface property of nanodiamond and its influence to protein adsorption and subsequent cellular responses along with the mechanism behind such capacity becomes more important. Here the role of surface energy associated with nanostructured diamond in modulating fibronectin and osteoblast(OB, bone forming cells) responses was investigated. Nanocrystalline diamond(NCD) and submicron crystalline diamond(SMCD) films with controllable surface energy were prepared by microwave-enhanced plasma chemical vapor deposition(MPCVD) techniques. Fibronectin adsorption on the diamond films with varied surface energy values was measured via the enzyme-linked immunosorbent assay(ELISA) and the relationship between the surface energy and fibronectin adsorption was studied. The result indicated that fibronectin adsorption on nanostructured surfaces was closely related to both surface energy and material microstructures. The spreading and migration of OB aggregates(each containing 30–50 cells) on the NCD with varied surface energy values were also studied. The result indicates a correlation between the cell spreading and migration on nanodiamond and the surface energy of nanostructured surface.

A Green Biocompatible Fabrication of Highly Porous Functional Ceramics with High Strength and Controllable Pore Structures

A green biocompatible foaming method utilizing natural coconut oil and cornstarch was developed to fabricate highly porous functional ceramics with controllable strengths and pore structures. The poros- ity of A1203 ceramics prepared via this method reached 79.6%-86.9% while these ceramics maintained high compressive strengths of 2.2-5.5 MPa. More importantly, porous A1203 ceramic with a pore size gra- dient was also readily fabricated by casting serial layers of foams that were set for different time periods. The potential applications of porous Al2O3 and HA ceramics fabricated by this green foaming method in- cluding scaffolds for oil cleaning and cell culture, respectively, were also demonstrated.