Microfibers have received much attention due to their promise for creating flexible and highly relevant tissue models for use in biomedical applications such as 3D cell culture, tissue modeling, and clinical treatments. A generated tissue or implanted material should mimic the natural microenvironment in terms of structural and mechanical properties as well as cell adhesion, differentiation, and growth rate. Therefore, the mechanical and biological properties of the fibers are of importance. This paper briefly introduces common fiber fabrication approaches, provides examples of polymers used in biomedical applications, and then reviews the methods applied to modify the mechanical and biological properties of fibers fabricated using different approaches for creating a highly controlled microenvironment for cell culturing. It is shown that microfibers are a highly tunable and versatile tool with great promise for creating 3D cell cultures with specific properties.

Abstract:Graphene is one of the emerging materials in the nanotechnology industry due to its potential applications in diverse areas. We report the fabrication of graphene nanosheets by spontaneous electrochemical reaction using solvated ion intercalation into graphite. The current literature focuses on the fabrication of graphene using lithium metal. Our procedure uses sodium metal, which results in a reduction of costs. Using various characterization techniques, we confirmed the fabrication of graphene nanosheets. We obtained an intensity ratio (I D /I G ) of 0.32 using Raman spectroscopy, interlayer spacing of 0.39 nm and our XPS results indicate that our fabricated compound is relatively oxidation free.

A facile method to produce few-layer graphene (FLG) nanosheets is developed using protein-assisted mechanical exfoliation. The predominant shear forces that are generated in a planetary ball mill facilitate the exfoliation of graphene layers from graphite flakes. The process employs a commonly known protein, bovine serum albumin (BSA), which not only acts as an effective exfoliation agent but also provides stability by preventing restacking of the graphene layers. The latter is demonstrated by the excellent long-term dispersibility of exfoliated graphene in an aqueous BSA solution, which exemplifies a common biological medium. The development of such potentially scalable and toxin-free methods is critical for producing cost-effective biocompatible graphene, enabling numerous possible biomedical and biological applications. A methodical study was performed to identify the effect of time and varying concentrations of BSA towards graphene exfoliation. The fabricated product has been characterized using Raman spectroscopy, powder X-ray diffraction, transmission electron microscopy and scanning electron microscopy. The BSA-FLG dispersion was then placed in media containing Astrocyte cells to check for cytotoxicity. It was found that lower concentrations of BSA-FLG dispersion had only minute cytotoxic effects on the Astrocyte cells.

We report the design of an ultrahigh vacuum compatible vapor dosing system for organometallic compounds. A unique feature of this doser is the elimination of all metallic surfaces in order to reduce the reactivity of the organometallic molecules towards the doser walls. The vapors only come in contact with glass, Teflon, and Kalrez and the doser is heatable to temperatures of 150 °C. A novel modification to a commercial glass stopcock is described. These modified valves are used in the doser to seal the ultrahigh vacuum system from the organometallic sample compartment and have been shown to be able to allow the vacuum system to maintain ultrahigh vacuum conditions even when the sample compartment is vented to atmosphere. Spring-loaded Teflon seals are used to seal the valve shaft against the glass wall thereby maintaining ultrahigh vacuum conditions and a chemically inert surface for the organometallic compounds. A further modification to these commercial valves is described allowing it to function as the sample compartment for the organometallic material. This compartment features a heatable reservoir, vacuum seals to ultrahigh vacuum levels, and a rapid exchange design to permit the interchange of dosing materials.