Optimizing collagen transport through track-etched nanopores

Polymer transport through nanopores is a potentially powerful tool for separation and organization of molecules in biotechnology applications. Our goal is to produce aligned collagen fibrils by mimicking cell-mediated collagen assembly: driving collagen monomers in solution through the aligned nanopores in track-etched membranes followed by fibrillogenesis at the pore exit. We examined type I atelo-collagen monomer transport in neutral, cold solution through polycarbonate track-etched membranes comprising 80-nm diameter, 6-μm long pores at 2% areal fraction. Source concentrations of 1.0, 2.8 and 7.0 mg/ml and pressure differentials of 0, 10 and 20 in H2O were used. Membrane surfaces were hydrophilized via covalent poly(ethylene glycol) binding to limit solute–membrane interaction. Collagen transport through the nanopores was a non-intuitive process due to the complex behavior of this associating molecule in semi-dilute solution. Nonetheless, a modified open pore model provided reasonable predictions of transport parameters. Transport rates were concentration- and pressure-dependent, with diffusivities across the membrane in semi-dilute solution 2-fold those in dilute solution, possibly via cooperative diffusion or polymer entrainment. The most significant enhancement of collagen transport was accomplished by membrane hydrophilization. The highest concentration transported (5.99 ± 2.58 mg/ml) with the highest monomer flux (2.60 ± 0.49 × 103 molecules s−1 pore−1) was observed using 2.8 mg collagen/ml, 10 in H2O and hydrophilic membranes.