Studies on surface coating of phospholipid vesicles with a non-ionic polymer

Liposomes coated with polymers may have a great potential in drug delivery. In this study, adsorption of the non-ionic hydroxyethyl cellulose (HEC) onto non-charged phospholipid vesicles was investigated. Both unmodified and hydrophobically modified (HM) HEC were included in the study. Possible interactions between the liposomes and the polymers were determined by changes in the size and the size distribution. Rheo-SALS measurements were carried out to verify the successfulness of the coating process. The stability was investigated by zeta potential measurements, UV-analysis and HPTLC. Mixing unmodified HEC (Mw 90,000 and 300,000) with the liposomes yielded no increase in the particle size. HM-HEC, however, was adsorbed onto both the fluid phase egg-PC liposomes and the gel phase DPPC liposomes. The Rheo-SALS measurements confirmed the successful coating of the liposomes. Complete coating resulted in increased chemical stability of the dispersion and in addition prevented aggregation. This study has shown that the non-ionic HM-HEC can be used to form polymer coated liposomes with neutral surface charge for enhanced stability.