In vivo biostability of a polymeric hollow fibre membrane for cell encapsulation

The biostability of poly(acrylonitrile-co-vinyl chloride) (P(AN/VC)) hollow fibre membranes was assessed in the rat peritoneal cavity over a 12 month period. The mechanical and chemical stabilities of the hollow fibre membrane (HFM) were characterized by measuring its tensile strength and molecular weight (by gel permeation chromatography) pre-implantation and post-explantation. The stability of the HFM transport properties was determined by molecular weight cut-off (MWCO) and hydraulic permeability (HP). Explanted HFMs were treated with 4M NaOH to remove adsorbed protein before measuring mechanical, chemical and transport properties. The HFM was stable in vivo for at least 12 months: (i) weight average molecular weight (Mw) at t = 0 was 143 000 g mol−1 (with a polydispersity index (PDI) of 2.3) and at t = 12 months it was 128 000 g mol−1 (with a PDI of 2.8); and (ii) tensile strength at t = 0, 52 ± 2 mdyne, did not change significantly over time and was 46 ± 7 mdyne at t = 15 months (P > 0.05 by a two-tailed Studentʹs t-test); and (iii) no significant differences, with respect to standard deviation, were observed in the transport properties: HP was 7.4 ± 1.5 ml min− 1 m−2 mmHg−1 at t = 0 and 7.5 ± 1.5 ml min−1 m−2 mmHg−1 at t = 12 months, while MWCO (at 90% rejection) was initially 40000 ± 8000 g mol−1 and then 54000 ± 10 000 gmol−1 at t = 12 months.