High-aspect-ratio gold nanorods: their synthesis and application to image cell-induced strain fields in collagen films.

Gold nanoparticles are receiving considerable attention due to their novel properties and the potential variety of their uses. Long gold nanorods with dimensions of approximately 20 × 400 nm exhibit strong light scattering and can be easily observed under dark-field microscopy. Here we describe the use of this light-scattering property to track micrometer scale strains in collagen gels and thick films, which result from cell traction forces applied by neonatal heart fibroblasts.

Age-dependent expression of collagen receptors and deformation of type I collagen substrates by rat cardiac fibroblasts.

Little is known about how age influences the ways in which cardiac fibroblasts interact with the extracellular matrix. We investigated the deformation of collagen substrates by neonatal and adult rat cardiac fibroblasts in monolayer and three-dimensional (3D) cultures, and quantified the expression of three collagen receptors [discoidin domain receptor (DDR)1, DDR2, and β1 integrin] and the contractile protein alpha smooth muscle actin (α-SMA) in these cells. We report that adult fibroblasts contracted 3D collagen substrates significantly less than their neonate counterparts, whereas no differences were observed in monolayer cultures.

The effect of gold nanorods on cell-mediated collagen remodeling.

Cardiac fibroblasts, the noncontractile cells of the heart, contribute to myocardial maintenance through the deposition, degradation, and organization of collagen. Adding polyelectrolyte-coated gold nanorods to three-dimensional constructs composed of collagen and cardiac fibroblasts reduced contraction and altered the expression of mRNAs encoding beta-actin, alpha-smooth muscle actin, and collagen type I. These data show that nanomaterials can modulate cell-mediated matrix remodeling and suggest that the targeted delivery of nanomaterials can be applied for antifibrotic therapies.

Gold nanoparticles in biology: beyond toxicity to cellular imaging.

Gold, enigmatically represented by the target-like design of its ancient alchemical symbol, has been considered a mystical material of great value for centuries. Nanoscale particles of gold now command a great deal of attention for biomedical applications. Depending on their size, shape, degree of aggregation, and local environment, gold nanoparticles can appear red, blue, or other colors.

Adaptive changes in cardiac fibroblast morphology and collagen organization as a result of mechanical environment.

There is a growing body of work in the literature that demonstrates the significant differences between 2D versus 3D environments in cell morphologies, spatial organization, cell-ECM interactions, and cell signaling. The 3D environments are generally considered more realistic tissue models both because they offer cells a surrounding environment rather than just a planar surface with which to interact, and because they provide the potential for more diverse mechanical environments. Many studies have examined cellular-mediated contraction of 3D matrices; however, because the 3D environment is much more complex and the scale more difficult to study, little is known regarding how mechanical environment, cell and collagen architecture, and collagen remodeling are linked.

Using gold nanorods to probe cell-induced collagen deformation.

In biological tissue, complex mechanisms of cellular response are closely linked to the mechanical environment that cells experience. The key to understanding these mechanisms may lie in measurement of local mechanical fields near living cells and between cells. We have developed a novel optical measurement technique which combines the light elastically scattered from gold nanorods with digital image analysis to track local deformations that occur in vitro between cells, in real time, under darkfield optical microscopy.

Characterization of the heterogeneous binding site affinity distributions in molecularly imprinted polymers.

Molecularly imprinted polymers (MIPs) are polymers that can be tailored with affinity and selectivity for a molecule of interest. Offsetting the low cost and ease of preparation of MIPs is the presence of binding sites that vary widely in affinity and selectivity. Presented is a review of methods that take into account binding site heterogeneity when calculating the binding properties of MIPs.