What are liposomes?

The most impor­tant and inter­est­ing attribute of phos­pho­lipids is their abil­ity to form spe­cial mol­e­c­u­lar struc­tures called lipo­somes. The mol­e­c­u­lar shape of a phos­pho­lipid con­sists of a water-loving head and two oil-loving tails.

Phospholipid

When plac­ing a large num­ber of these mol­e­cules into a lim­ited space they will arrange them­selves spon­ta­neously to match their heads together and also their tails.

Cell Membrane Cross Section

The fig­ure above shows the arrange­ment of a sec­tion of a liv­ing cell mem­brane which con­sists largely of phos­pho­lipids. As you can see, the phos­pho­lipid mol­e­cules have arranged them­selves to form a mem­brane so that oil droplets can­not pen­e­trate the cell mem­brane because they would be repelled by the wall of hydrophilic heads. In like man­ner, no water can pen­e­trate the mem­brane because the lipophilic tails inside will not allow pas­sage. The only access through the mem­brane is by spe­cial pro­tein mol­e­cules that are pro­grammed to let only cer­tain chem­i­cals pass in and out of the cell.

Plant phos­pho­lipids are all very sim­i­lar in struc­ture and com­po­si­tion. Under cer­tain phys­i­cal con­di­tions they will spon­ta­neously form micro­scopic spheres whose walls are very sim­i­lar in con­struc­tion to the actual cell mem­brane shown above.

Liposome Structure

 

The size of these spheres is very small, in the order of a nanome­ter. As illus­trated, the spheres are hol­low inside and enclose some of the liq­uid mate­r­ial in which they were formed (inclu­sion). Because of the small size of the phos­pho­lipid mol­e­cule and micros­pheres, they can pass through the epi­der­mis and act as a car­rier for the enclosed sub­stances. It is pos­tu­lated that when they reach the out­side of a liv­ing cell mem­brane in the der­mis they may become accepted as part of the mem­brane, being of the same com­po­si­tion. This process is as shown.Liposome Inclusion

Thus, they are able to carry with them any enclosed sub­stances into the der­mis and to the indi­vid­ual cells.

The abil­ity of phos­pho­lipids to act as the car­rier mech­a­nism for deliv­er­ing active ingre­di­ents directly to the cell level has exten­sive impli­ca­tions for cos­met­ics. By them­selves they are absolutely non-toxic and cause no skin irri­ta­tions, not even around the eyes. Their dan­ger lies in their abil­ity to carry toxic or con­t­a­m­i­nated sub­stances into the cells. The devel­op­ment of lipo­some tech­nol­ogy offers the poten­tial for many ben­e­fi­cial cos­metic prod­ucts. How­ever, the cos­metic devel­oper has to deal very care­fully with the selec­tion of raw mate­ri­als and the ques­tion of the bio­log­i­cal fate of the prepa­ra­tion. The micros­pheres them­selves are con­stantly under­go­ing changes due to ther­mal activ­ity dur­ing prepa­ra­tion and stor­age. As a result, each ingre­di­ent of the prepa­ra­tion can end up inside the micros­pheres over time.

More than 80 per­cent of the cos­metic prod­ucts on the mar­ket con­tain toxic sub­stances that if used in lipo­some prod­ucts will even­tu­ally become part of the inclu­sion inside lipo­somes that, in turn, will get inside your skin cells. There­fore, beware of prod­ucts with lipo­somes that also con­tain sub­stances caus­ing adverse effects. As an exam­ple, preser­v­a­tives fall into this haz­ardous cat­e­gory since they are all cel­lu­lar toxins.

It has not been decided by the FDA whether lipo­some prod­ucts with inclu­sions should be con­sid­ered a med­i­cine and put under the scrutiny of med­ical doc­tors with the advan­tage of doc­u­ment­ing and track­ing of poten­tial long-term adverse effects. Accord­ing to the Cos­metic Hand­book, pub­lished by the Food and Drug Admin­is­tra­tion, “Prod­ucts that are cos­met­ics but are also intended to treat or pre­vent dis­ease, or affect the struc­ture or func­tions of the human body, are con­sid­ered also drugs and must com­ply with both the drug and cos­metic pro­vi­sions of the law.“1 Some com­bi­na­tions of lipo­somes and active sub­stances cer­tainly qual­ify for this category.

1 U.S. Depart­ment of Health and Human Ser­vices, Cos­metic Hand­book, U.S. Gov­ern­ment Print­ing Office.