Nanotechnology in cosmetics as seen by a “nanocook” (part III)

[Qui trovate la versione italiana di questo articolo]

In the previous articles we learned something about nanotechnology in the pharmaceutical and cosmetic field, and about which kinds of nanomaterials are applied in cosmetic products and why.

At the end of Part II of this long journey, we learned that if we are non-professional home-formulators, our possibilities to use nanotechnology in creams is basically limited to liposomes.

Now it’s time to understand which kinds of liposomes we can get as hobbyists and if it’s really worth the effort.

As already mentioned, liposomes are small spherical vesicles made of phospholipids. During their synthesis, the phospholipids arrange in a very similar way as they do in cellular membranes, forming a bilayer with the hydrophilic heads facing the external aqueous environment (and the inner aqueous compartment) and the hydrophobic tails packed within the bilayer. So in theory, these vesicles can host hydrophylic active ingredients in the inner aqueous core and hydrophobic molecules across the bilayer (1).

Liposomes are known in pharmaceutical technology since decades (2). They were one of the pioneers of nano-sized drug delivery systems and they’re still pretty strong in research. They’re also one of the few nano-sized drug delivery systems who made it to the market.

But as we have seen, they find application also in cosmetic science (3). The idea behind the use of liposomes in topical preparations is that the active ingredient would penetrate the skin deeper when encapsulated into a vehicle like a liposomes, rather than when it is free in a solution (4). Which is a nice concept, but can we control it and exploit it also when making creams at home in our hobby lab?

I thought about it and my short answer to this is: we can use them (because we can buy them), but they might not have the effect that we expect.

First of all, let’s see what can we get. My favorite supplier is the Italian shop Glamour Cosmetics, that offers a relatively wide choice of liposomes encapsulating several active ingredients: hyaluronic acid, peptides, functional ingredients against cellulite, kogic acid, panax ginseng extract, antioxidants, vitamines… So basically, anti-aging functional ingredients and anti-cellulite. I haven’t checked all liposomal formulations that they offer, but all those I’ve seen are the simplest liposomes ever: they’re based on lecithin, the most obvious phospholipid.

Now it’s time for my unsolicited opinion.

I believe that using them in a homemade cream is probably not harmful (they’re made of lecithin, as said, which is not evil, on the contrary, it’s wonderful on the skin), but it might disappoint our expectations.

The problem is not that the liposome cannot penetrate the skin barrier. As we mentioned in the previous articles, they do (but for the billionth time: we’re still speaking about stratum corneum, not about systemic circulation).

The problem relies in the fact that when we make creams at home, we don’t have much control on the parameters that influence the skin permeation of these vesicles and the delivery effectiveness. Among the thousands of parameters we should take care of (including the rest of the cream formulation!), for example we have:

The liposome loading. We don’t know the functional ingredient concentration in the liposome formulation (the description provided by the supplier does not mention it). My experience tells me that encapsulation efficiency is extremely low for liposomes (that’s why I used polymeric nanoparticles), therefore I expect that in the batch of hyaluronic acid liposomes that I buy there will be very VERY few hyaluronic acid. And since the providers don’t tell us the concentration of the active ingredient, we just have to trust them that there is some.

The size of the carrier. We don’t know the size of the liposomes. The fact that they could penetrate the skin barrier is dependent on the size. We don’t have this data and we don’t have an instrument at home that allows us to check.

The stability of the carrier. Even if we knew the size, we don’t know if it stays like this over time. And we don’t know if the active principle gets released from the liposomes. In other terms: we don’t know the shelf stability of the liposomes. Liposomes and similar drug delivery systems share one big goal: releasing the payload. They’re not meant to keep it indefinitely inside them. The liposomes we buy for cosmetic purposes are in a solution, which means that eventually the payload will be released and will be in solution. So in the end, what we put in our cream might be just a mixture of phospholipids and free hyaluronic acid. Which is good for our skin anyway, but it’s not as drug delivery system with enhanced permeation.

The actual delivered dose. Now, let’s assume that we have the loading, the size and the stability under control and we formulate our cream with X% of liposomes. This means we have Y% of active ingredients (=the loading% of the liposomes, which is lower than X%, meaning that if we use 5% of hyaluronic acid liposomes it doesn’t mean 5% hyaluronic acid). Now, we apply the cream on the skin. How much of this 5% liposomes (containing Y% active ingredient) make it through the skin? I fear: not so much, and probably not in the way we think (5).

So in the end, I bought them once (because I was curious) and I still have them, but I would not buy them again. If you don’t have them, don’t worry and just use hyaluronic acid.

Of course, my opinion here is limited to the use of liposomes to enhance the penetration of active ingredients through the skin. The story is completely different if we want to use liposomes in order to facilitate the formulation of some compounds that would not be stable in water or in the formulation (6). You still have the intrinsic liposome shelf stability problem, but if they are stable, they can represent a nice tool to formulate some active ingredients that you couldn’t use otherwise.

To conclude this journey through nanotechnology, I will give you a little tip in case you still want to give liposomes a try and want to include them in a lotion or in a cream:

  • Storage: I suggest to store them in the fridge. Even if the formulation includes preservatives and stabilizers, the lower the temperature, the slower the payload release from the drug delivery system.
  • Addition to your formula: add them in the cool down phase only once you already added all the rest and you are done with the high speed homogenisation. In other words: after you add them, don’t mix again with the handblender.

I hope this series of article was somehow useful or at least interesting to you. If there are other aspects of nanotechnology that you would like me to discuss, just let me know!

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