Quantitative measurement of nanoparticle release from rubber composites during fabrication and testing

Carbon black has been a key ingredient in high-performance composites, such as tire rubber, for over a hundred years. This reinforcing filler increases rubber rigidity and reduces tire wear, among many other useful effects. New nanomaterials, such as graphene and carbon nanotubes, may bring new performance improvements. However, their usefulness cannot be evaluated unless worker safety is assured by demonstrating that the nanoparticles are not released at harmful concentrations during manufacture and testing. Here, we present a flexible, general method for the quantitative evaluation of nanoparticle release from rubber nanocomposites. We evaluate manufacturing steps such as powder handling, uncured rubber milling, and curing. We also evaluate particle emission during cured rubber abrasion as an aggressive example of the testing rubber goods are subjected to. We quantify released nanoparticle concentrations for clay nanoparticles, graphene-like materials, and carbon nanotubes. We also describe a mechanistic framework based on the balance of adhesive and kinetic energies, which helps understand when nanoparticles are or are not released. This method contributes to the assessment of workers’ exposure to nanoparticles during the various stages of the industrial process, which is an essential step in managing the risk associated with the use of nanomaterials in manufacturing.

Oriented Cell Alignment Induced by a Nanostructured Titanium Surface Enhances Expression of Cell Differentiation Markers

A key factor for dental implant success is a good sealing between the implant surface and both soft (gum) and hard (bone) tissues. Surface nanotopography can modulate cell response through mechanotransduction. The main objective of this research was the development of nanostructured titanium (Ti) surfaces that promote both soft and hard tissue integration with potential application in dental implants. Nanostructured Ti surfaces were developed by electrochemical anodization—nanopores (NPs) and nanonets (NNs)—and characterized by atomic force microscopy, scanning electronic microscopy, and contact angle analysis. In addition, nanoparticle release and apoptosis activation were analyzed on cell culture. NP surfaces showed nanoparticle release, which increased in vitro cell apoptosis. Primary human gingival fibroblasts (hGFs) and human bone marrow mesenchymal stem cells (hBM-MSCs) were used to test cell adhesion, cytotoxicity, metabolic activity, and differentiation markers. Finally, cell orientation on the different surfaces was analyzed using a phalloidin staining. NN surfaces induced an oriented alignment of both cell types, leading in turn to an improved expression of differentiation markers. Our results suggest that NN structuration of Ti surfaces has great potential to be used for dental implant abutments to improve both soft and hard tissue integration.