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Anna Mackin, Jeffrey Olson; Adsorption of Complement Factor D by polyacrylonitrile hollow fiber membrane. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5730.
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© ARVO (1962-2015); The Authors (2016-present)
Complement Factor D (CFD) is a serine protease component of alternative complement pathway implicated in pathogenesis of age-related macular degeneration (AMD). Polyacrylonitrile (PAN) hollow fiber membranes previously utilized in hemodialysis are known to have CFD absorption properties. We performed an in-vitro study of CFD adsorption by polyacrylonitrile (PAN) hollow fiber membranes.
Experimental samples (N=2) (33 mg dry weight) of PAN hollow fibers <200um inner diameter cut in <4mm long fragments, hydrated and equilibrated in ELISA buffer, were incubated at 37°C for 1 hour with recombinant human CFD samples of 20 ng/ml concentration and analyzed with ELISA to determine CFD concentration after incubation. Samples with polypropylene hollow fiber membranes of equal dimensions and weight (N=2), and samples of CFD alone (N=3) were used as sham control and negative control, respectively. Subsequently, experimental samples of PAN hollow fibers (15 mg dry weight, in <10mm long fragments) were incubated with CFD of increasing concentration (up to 1400 ng/ml) to study saturation properties of PAN. Finally, PAN membrane fragments were visualized under confocal fluorescent microscopy to determine excitation/emission behavior.
Incubation of CFD solution with PAN hollow fibers led to significantly lower CFD concentration (mean 2.22 +/- 0.052 ng/ml) as compared to incubation with polypropylene (mean 4.10 +/- 0.20 ng/ml) or negative control (mean 5.04 +/- 0.32 ng/ml) (p<0.001) (Figure 1). Amount of CFD adsorbed appeared to increase with increasing initial CFD concentration, approaching a plateau of 80% adsorption, not exhibiting an expected point of saturation (Figure 1). Visualized under confocal fluorescent microscopy, PAN membrane fragments exhibited green spectrum fluorescence when excited at 488 nm and 640 nm wavelengths (Figure 2).
Incubation with PAN hollow fibers significantly reduces concentration of CFD, allowing increasing portions of original CFD to be adsorbed in solutions of increasing CFD concentration. This makes PAN an attractive candidate for future application as an intra-ocular CFD trap. Adsorption properties of PAN can be further studied by conjugating CFD with a fluorescent marker exhibiting excitation properties distinct from those of PAN.
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