Membrane function, drug release from polym

Highly water soluble drugs, as they are typical for oral administration, can be released from polymer beads with low (< 10%) water- but high ethanolswelling capacity at controlled rates, for up to 8 hours. The release of oxprenolol-HCl (77% water solubility) and diclofenac Na (2.6% water solubility) from drug loaded monoliths is a function of water content and crosslink density. By partial extraction of the drug loaded beads the release can be further slowed down and, in the case of oxprenolol-HCl, delayed for several hours the delay is dependent on water content of the polymer and is the result of the formation of a hydrophobic surface membrane. 

Except from the tuned permeability that concave brushes may present, there are also other interesting possibilities involving (1) the trapping of molecules inside membranes and their controlled release upon collapse of the brush layer, a function of obvious relation to drug delivery (2) the development of size-selective composite membranes for dissolved polymers in solution (nanofiltration) [35] and (3) the fabrication of pore-brush systems that are sensitive to the presence of specific molecules by the appropriate modification/functionalization of the grafted chains [46]. 

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