Synthesis, permeability and biocompatibility of tricomponent membranes containing polyethylene glycol, polydimethylsiloxane and polypentamethylcyclopentasiloxane domains

The synthesis of "smart" tricomponent amphiphilic membranes containing poly(ethylene glycol) (PEG), polydimethylsiloxane (PDMS) and polypentamethylcyclopentasiloxane (PD₅) domains is described. Contact angle hysteresis indicates that in air, the surfaces of such PEG/PD₅/PDMS membranes are enriched by the hydrophobic components, PDMS and PD₅, while in water, the surfaces are rich in the hydrophilic PEG. The oxygen permeability of a series of membranes with varying M_{c,hydrophilic} (M_n,PEG=4600, 10,000 and 20,000g/mol) and varying PEG/PD₅/PDMS compositions was studied. Oxygen permeability increased with the amount of PDMS in the membrane. The molecular weight cut-off (MWCO) ranges and permeability coefficients of insulin through a series of PEG/PD₅/PDMS(=29/14/57) membranes with varying M_{c,hydrophilic} were determined. Insulin permeability is directly related to M_{c,hydrophilic} of the membrane. MWCO studies show that the membranes are semipermeable to, i.e., allow the transport of smaller proteins such as insulin (M_n=5733g/mol, R_s=1.34nm) and cytochrome c (M_n=12,400g/mol, R_s=1.63nm), but are barriers to larger proteins such as albumin (M_n=66,000g/mol, R_s=3.62nm). Implantation of representative membranes in rats showed them to be biocompatible. According to these studies, PEG/PD₅/PDMS membranes may be suitable for biological applications, e.g., immunoisolation of cells.