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Release of Potassium Ion and Calcium Ion from Phosphorylcholine Group Bearing Hydrogels
Center for Bioelectronics, Biosensors and Biochips (C3B), Clemson University Advanced Materials Center, 100 Technology Drive, Anderson, SC 29625, USA
Department of Chemical and Biomolecular Engineering, 132 Earle Hall, Clemson University, Clemson, SC 29634, USA
Department of Chemistry, University of the West Indies, St. Augustine, Trinidad and Tobago
ABTECH Scientific, Inc., Biotechnology Research Park, 800 East Leigh Street, Richmond, VA 23219, USA
Department of Materials Engineering and Department of Bioengineering, School of Engineering, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
* Author to whom correspondence should be addressed.
Received: 28 September 2013; in revised form: 17 October 2013 / Accepted: 25 October 2013 / Published: 11 November 2013
Abstract: In an attempt to recreate the microenvironment necessary for directed hematopoietic stem cell differentiation, control over the amount of ions available to the cells is necessary. The release of potassium ion and calcium ion via the control of cross-linking density of a poly(2-hydroxyethyl methacrylate) (pHEMA)-based hydrogel containing 1 mol % 2-methacryloyloxyethyl phosphorylcholine (MPC) and 5 mol % oligo(ethylene glycol) (400) monomethacrylate [OEG(400)MA] was investigated. Tetra(ethylene glycol) diacrylate (TEGDA), the cross-linker, was varied over the range of 1–12 mol %. Hydrogel discs (ϕ = 4.5 mm and h = 2.0 mm) were formed by UV polymerization within silicone isolators to contain 1.0 M CaCl2 and 0.1 M KCl, respectively. Isothermal release profiles, were measured at 37 °C in 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid sodium salt (HEPES) buffer using either calcium ion or potassium ion selective electrodes (ISE). The resulting release profiles were found to be independent of cross-linking density. Average (n = 3) release profiles were fit to five different release models with the Korsmeyer-Peppas equation, a porous media transport model, exhibiting the greatest correlation (R2 > 0.95). The diffusion exponent, n was calculated to be 0.24 ± 0.02 and 0.36 ± 0.04 for calcium ion and potassium ion respectively indicating non-Fickian diffusion. The resulting diffusion coefficients were calculated to be 2.6 × 10−6 and 11.2 × 10−6 cm2/s, which compare well to literature values of 2.25 × 10−6 and 19.2 × 10−6 cm2/s for calcium ion and potassium ion, respectively.
Keywords: calcium ion; potassium ion; diffusion; 2-methacryloyloxyethyl phosphorylcholine; poly(2-hydroxyethyl methacrylate); hydrogel matrix; Zwitterionic; HEMA
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Aucoin, H.R.; Wilson, A.N.; Wilson, A.M.; Ishihara, K.; Guiseppi-Elie, A. Release of Potassium Ion and Calcium Ion from Phosphorylcholine Group Bearing Hydrogels. Polymers 2013, 5, 1241-1257.
Aucoin HR, Wilson AN, Wilson AM, Ishihara K, Guiseppi-Elie A. Release of Potassium Ion and Calcium Ion from Phosphorylcholine Group Bearing Hydrogels. Polymers. 2013; 5(4):1241-1257.
Aucoin, Hanna R.; Wilson, A. N.; Wilson, Ann M.; Ishihara, Kazuhiko; Guiseppi-Elie, Anthony. 2013. "Release of Potassium Ion and Calcium Ion from Phosphorylcholine Group Bearing Hydrogels." Polymers 5, no. 4: 1241-1257.