The poly(ethylene glycol) – Ficoll aqueous phase system has been found to show promise for use in the microencapsulation of mammalian cells in immunoprotective alginate membranes. This project was concerned with the characterisation of the PEG 10,000 – Ficoll 400,000 system in 0.14M NaCl, 5mM KCl, and 1mM TRIS buffer.
Standard curves were developed for the determination of concentrations using polarimetry and measurement of refractive index. These were found to be accurate to within 0.02% w/w. Standard curves were also developed for the density of pure PEG and Ficoll solutions.
Linear correlations for specific refractive index increment and specific optical rotation were compared to correlations reported by Bamberger et al (1985). Specific refractive index increment was found to be slightly, but statistically significantly, smaller than the values reported for PEG and Ficoll. Specific optical rotation was found to be in almost perfect agreement to the value measured by Albertsson (1971) and reported by Bamberger et al (1985).
Turbidometric titration was used to determine a preliminary estimate of the binodial of the PEG-Ficoll system. Nine phase systems were then generated and characterised. Concentrations in each phase were determined to an average error of approxim ately 0.1% w/w for Ficoll, and about 0.15% w/w for PEG. A disparity between the results from turbidometric titration and tieline analysis was noted, and an explanation put forward, supported in part by analysis using gel permeation chromatography. A correlation based on the Flory-Huggins theory for polymer solutions, developed by Diamond and Hsu (1992) was used to model the phase diagram. This was found to give a less-than-perfect fit to the data, and so a modification was made which allowed a much closer fit. This modification was further tested using data for nine phase systems collected by Diamond and Hsu (1989).