Mass transfer characteristics of poly-lysine, poly-ornithine and poly-methylene-co-guanidine membrane coated alginate microcapsules

Mass transfer characteristics was estimated for three types of microcapsules with low viscosity high guluronic (LVG) alginate core, coated with three different poly-aminoacid based membranes: poly-lysine (PLL), poly-ornithine (PLO) and poly-methylene-co-guanidine (PMCG), respectively. Molecular probes included Vitamin B12, albumin and two types of polyvinylpyrrolidones (PVP) as mass transport markers. Microcapsule membranes were investigated both in the transient state by determination of mass transfer coefficient h and in the equilibrium state by determination of mass ingress and partition coefficient K. Mass transfer coefficients h were larger for PLL and PLO than for PMCG and were in the range from about 0.008 cm/min for Vitamin B12 to about 0.0003 cm/min for 40 kDa PVP. Vitamin B12 penetrated freely into the investigated microcapsules whereas partition coefficients K for other markers were in the range between 0.91 and 0.13. Inspection of the determined mass transfer coefficient values and, possibly, introduction of “molecular transfer cut-off” (MTCO) curve yields much more clear insight into the differences between poly-aminoacid membranes than the analysis of equilibrium state parameters. It was concluded that the mass transport is faster for PLL and PLO microcapsules than for PMCG formulation whereas the transfer of high molecular mass markers is restricted by all investigated microcapsule membranes.