Enhanced lubrication on tissue and biomaterial surfaces through peptide-mediated binding of hyaluronic acid.

Lubrication is key for the efficient function of devices and tissues with moving surfaces, such as articulating joints, ocular surfaces and the lungs. Indeed, lubrication dysfunction leads to increased friction and degeneration of these systems. Here, we present a polymer-peptide surface coating platform to non-covalently bind hyaluronic acid (HA), a natural lubricant in the body. Tissue surfaces treated with the HA-binding system exhibited higher lubricity values, and in vivo were able to retain HA in the articular joint and to bind ocular tissue surfaces. Biomaterials-mediated strategies that locally bind and concentrate HA could provide physical and biological benefits when used to treat tissue-lubricating dysfunction and to coat medical devices.

Photochemistry of aqueous C60 clusters: wavelength dependency and product characterization.

To construct accurate risk assessment models for engineered nanomaterials, there is urgent need for information on the reactivity (or conversely, persistence) and transformation pathways of these materials in the natural environment. As an important step toward addressing this issue, we have characterized the products formed when aqueous C(60) clusters (nC(60)) are exposed to natural sunlight and also have assessed the wavelengths primarily responsible for phototransformation. Long-wavelength light (λ ≥ 400 nm) isolated from sunlight, was shown to be important in both the phototransformation of nC(60) and in the production of (1)O(2). The significance of visible light in mediating the phototransformation of nC(60) was supported by additional experiments with monochromatic light in which the apparent quantum yield at 436 nm (Φ(436 nm) = (2.08 ± 0.08) × 10(-5)) was comparable to that at 366 nm (Φ(366 nm) = (2.02 ± 0.07) × 10(-5)). LDI-TOF mass spectrometry indicated that most of the photoproducts formed after 947 h of irradiation in natural sunlight retain a 60 atom carbon structure. A combination of (13)C NMR analysis of (13)C-enriched nC(60), X-ray photoelectron spectroscopy and FTIR indicated that photoproducts have olefinic carbon atoms as well as a variety of oxygen-containing functional groups, including vinyl ether and carbonyl or carboxyl groups, whose presence destroys the native π-electron system of C(60). Thus, the photoreactivity of nC(60) in sunlight leads to the formation of water-soluble C(60) derivatives.

Chemical and structural characterization of carbon nanotube surfaces.

To utilize carbon nanotubes (CNTs) in various commercial and scientific applications, the graphene sheets that comprise CNT surfaces are often modified to tailor properties, such as dispersion. In this article, we provide a critical review of the techniques used to explore the chemical and structural characteristics of CNTs modified by covalent surface modification strategies that involve the direct incorporation of specific elements and inorganic or organic functional groups into the graphene sidewalls. Using examples from the literature, we discuss not only the popular techniques such as TEM, XPS, IR, and Raman spectroscopy but also more specialized techniques such as chemical derivatization, Boehm titrations, EELS, NEXAFS, TPD, and TGA. The chemical or structural information provided by each technique discussed, as well as their strengths and limitations. Particular emphasis is placed on XPS and the application of chemical derivatization in conjunction with XPS to quantify functional groups on CNT surfaces in situations where spectral deconvolution of XPS lineshapes is ambiguous.