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The in vitro effects of liposomes on HaCaT human keratinocytes were studied with regard to their uptake, lipid fluidity and proliferation of the cells. Oligolamellar liposomes, prepared from soya bean phospholipids, had a mean size of 150 mm and consisted predominantly of phosphatidylcholine (83%) and phosphatidylethanolamine (10%) and the fatty acids comprised mainly linoleic acid (66%) or other unsaturated fatty acids. After 6 and 24 h of incubation with 1 and 0.1% w/v of liposomal lipids, phase-contrast microscopy revealed marked cytoplasmic vacuolization of the cells. Keratinocytes treated with the liposomes contained aggregations of multilaminated lipid material without delimiting cell membranes. The cellular lipid fluidity (reciprocal of diphenylhexatriene fluorescence polarization P-value) correlated with liposomal concentration and incubation time. A significant elevation of lipid fluidity (P less than 0.05) was observed with 1 and 0.1% liposomes after 1 h of incubation (81.8 +/- 4.7 and 95.7 +/- 1.2% of control P value) and for 0.01% liposomes after 3 h (96.2 +/- 1.5%). Maximum fluidity occurred after 48 h of exposure to 1% liposomes (42.1 +/- 3.1%). Exposure to liposomal lipids for 24 and 48 h resulted in suppressed cell proliferation with 50% inhibition concentrations (IC50), being 0.06% for incorporation of [3H]-thymidine. 0.08% for [14C]-amino-acid incorporation and greater than 1% for protein content per well after 24 h of exposure. The cells were able to proliferate and lipid fluidity returned to normal within 7 days following discontinuation of incubation with liposomal lipids.

The percutaneous absorption of liposomes (prepared from NAT 106) was investigated with radioactively labelled substances in comparison with percutaneous absorption without liposomes (controls) in vivo on the skin of young pigs. Radioactivity was monitored as a function of time in skin tissue, plasma or blood and in urine. Elevated tissue levels, increased absorption and renal elimination of the various liposomal preparations in comparison to the controls were measured.

The influence of three different liposome formulations (NAT 106, NAT 50, NAT 89), as empty liposomes and loaded with 0.05% betamethasone, on blood circulation in the corium was investigated by means of laser Doppler flowmetry. All three empty liposomes brought about a decrease in circulation. The maximum effect was reached 90 min after a 30-min occlusive application of the test preparations. Loading with betamethasone resulted in a significant increase in circulation after only 15 min. This increase in interpreted as a steroid effect. No comparable symptoms appeared with the application of base cream DAC (an O/W emulsion) or of betamethasone in base cream under identical experimental conditions.

The penetration behaviour of liposome (prepared from NAT 106)-incorporated proteins was investigated in vivo by use of monoclonal antibodies (MOAB) as model substances on the skin of young pigs. Within 20 min of topical application, an even distribution of liposome-incorporated antibodies through all skin layers could be shown by means of an immunohistochemical stain.

This is the first report of induction of high titer mouse-antihuman spermatozoal antibodies using a spermatozoal antigen incorporated in liposomes. The peptide antigens that were incorporated into pure phosphatidylcholine liposomes are known to react with the naturally occurring antibodies in sera of sterile patients. Electron microscopy and the complement-dependent glucose release tests indicated that the peptides were entrapped in the aqueous phase between the lipid bilayers in the liposome vehicles. This is in contrast to most other liposomal antigens that are expressed on the outer lipid surface. In view of the nontoxic nature of the liposomes these results could be of some interest in immunological fertility regulation trials with appropriate antigens in an allogeneic system.

The in vitro effects of liposomes on HaCaT humph keratinocytes were studied with regard to their uptake, lipid fluidity and proliferation of the cells. Oligolamellar liposomes, prepared from soya bean phospholipids, had a mean size of 150 nm and consisted predominantly of phosphattdylcholine (83%) and phosphatidylethanolamine (10%) and the fatty acids comprised mainly linoleic acid (66%) or other unsaturated fatty acids. After 6 and 24 h of incubation with I and 0.1% w/v of liposomal lipids, phase-contrast microscopy revealed marked cytoplasmic vacuolization of the cells. Keratinocytes treated with the liposomes contained aggregations of multilaminated lipid material without delimiting cell membranes. The cellular lipid fluidity (reciprocal of diphenylhexatriene fluorescence polarization P-value) correlated with liposomal concentration and incubation time. A significant elevation of lipid fluidity (P < 0.05) was observed with I and 0.1% liposomes after 1 h of incubation (81.84 ± 4:7 and 95.7 ± 1.2% of control P value) and for 0.01% liposomes alter 3 h (96.24 ± 5%). Maximum fluidity occurred alter 48 h of exposure to 1% liposomes (42.1 ± 3.1%). Exposure to liposomal lipids for 24 and 48 h resulted in suppressed cell proliferation with 50% inhibition concentrations (IC50), being 0.06% for incorporation of [³H]-thymidine. 0.08% for [14C]-amino-acid corporation and > 1% for protein content per well after 24 h of exposure. The cells were able to proliferate and lipid fluidity returned to normal within 7 days following discontinuation of incubation with liposomal lipids. [ABSTRACT FROM AUTHOR]