Fibronectin quantification in plasma and vitreous by a noncompetitive ELISA technique

Ff-nano, short functionalized nanorods derived from Ff (f1, fd, or M13) filamentous bacteriophage

F-specific filamentous phage of Escherichia coli (Ff: f1, M13, or fd) are long thin filaments (860 nm × 6 nm). They have been a major workhorse in display technologies and bionanotechnology; however, some applications are limited by the high length-to-diameter ratio of Ff. Furthermore, use of functionalized Ff outside of laboratory containment is in part hampered by the fact that they are genetically modified viruses. We have now developed a system for production and purification of very short functionalized Ff-phage-derived nanorods, named Ff-nano, that are only 50 nm in length. In contrast to standard Ff-derived vectors that replicate in E. coli and contain antibiotic-resistance genes, Ff-nano are protein-DNA complexes that cannot replicate on their own and do not contain any coding sequences. These nanorods show an increased resistance to heating at 70^∘C in 1% SDS in comparison to the full-length Ff phage of the same coat composition. We demonstrate that functionalized Ff-nano particles are suitable for application as detection particles in sensitive and quantitative “dipstick” lateral flow diagnostic assay for human plasma fibronectin.

Cytokine effect on fibronectin release by retinal pigment epithelial cells

Because fibronectin (FN) is known to be present in membranes in proliferative vitreoretinopathy, we sought to identify cytokines that regulate the release of FN by retinal pigment epithelial cells (RPE). Levels of FN in the supernatant of cultured human RPE cells were quantified with an ELISA, after which the cells were stimulated with human recombinant cytokines, interleukin-1 beta (IL-1 beta), tumor necrosis factor alpha (TNF alpha), interleukin-6 (IL-6), interferon gamma (IFN-gamma), transforming growth factor beta 1 and 2 (TGF-beta), and phorbol myristate acetate (PMA). Protein kinase C (PKC) was blocked by 2 nM calphostin C or 1 mM staurosporine. RPE cells released FN into the supernatant constitutively. TGF-beta 1 and TGF-beta 2 upregulated the FN release in a dose- and time-dependent manner. The other cytokines tested were without effect. In combination, IFN-gamma and IL-1 beta reduced the effect of TGF-beta. PMA, which is a PKC activator, also increased the release of FN in a dose-dependent manner. Blocking of PKC with specific inhibitors abolished the effects of TGF-beta and PMA. The results show that TGF-beta is a potent stimulator of FN release by RPE cells, and exerts its effects via signal transduction involving PKC. Its effect is reduced by IFN-gamma.