[Qui trovate la versione italiana di questo articolo]
If you are not new to my blog and especially to the “Potions” sections, you probably know that I am a former researcher and that I used to be a nanocook. That means, I used to do research in the nanomedicine field and specifically I developed nanoparticle-based drug delivery systems. So, to say it in Breaking Bad language, I cooked nanoparticles.
Although I am a pharmaceutical chemist, I am not specialised in cosmetic chemistry. I knew that nanotechnology is a hot topic in cosmetics, too, but I had to search for some papers to understand which kinds of nanomaterials and nanovectors are actually used in cosmetics and why exactly.
In this series of articles I will try to explain you what do we mean by nanotechnology and why is it so interesting in pharmaceutical and cosmetic research, and I will tell you something about the main nanomaterials used in cosmetics and how is it made. Since my blog is mainly about DIY-formulation for hobbyists, I will describe mainly the nanostuff that we can actually use as non-professionals and that we find in the supplier shops.
What is nanotechnology?
Nanotechnology is a field of science that deals with the design, characterization, production and application of objects with sizes ranging from 1 to 100 nm. Actually, the size range that defines what is nanotechnology and what is not is pretty variable: for example, in drug delivery application objects with sizes up to 1000 nm (1 um) are generally considered as nano.
Nanotechnology finds application in many different fields, from the biomedical to the optical, mechanical and pharmaceutical fields, and of course in cosmetics, too (otherwise I wouldn’t be writing this article).
One of the most interesting applications is the pharmaceutical one, which is very close to the cosmetic application. When applied to medicine and drug delivery, nanotechnology is typically referred to as nanomedicine.
Nanomedicine is one of the most researched topics since decades and it involves the application of nanocarriers to the delivery of drugs. These nanocarriers are basically nano-sized objects that encapsulate and host the active drug and transport it within the organism. The administration of nanocarrier-encapsulated drugs provides numerous advantages compared to when the drug is administered in its free form (1, 2), such as:
- Increased stability of the drug molecule: the drug is protected within the nanocarrier’s walls and is not easily subject to degradation during its shelf life and when it comes in contact with the bloodstream of the patient
- Formulation aid: some drugs are insoluble or instable in water or in the formulation environment (the injection solution, the tablet/capsule powder formulation, the topical cream) and the encapsulation into a nanocarrier can improve their formulation stability
- Targeting possibilities: nanocarriers can target organs and districts of the body, either thanks to their intrinsic features or because they can be modified with targeting moieties. This means that they can deliver the drug to specific districts in the body, namely, to the portion that actually needs the treatment. This leads to several advantages, including:
- Decreasing the drug dose required to reach a certain effect, because the administered drug effectively reaches the therapy target in a massive and effective amount, whereas with traditional delivery forms (injection in free form, capsules, tablets) it is subject to distribution to the whole body and extensive metabolism and excretion
- Lowering side effects: if the drug does not reach healthy tissues, it won’t damage them (this is important especially with cancer treatment)
- Allowing the controlled release of the drug over time, which contributes to decreasing the necessary administered dose
- Improving efficacy in districts that are difficult to reach: some districts of our body are very well protected and free drugs cannot reach them on their own, such as the central nervous system and the brain. With targeted nanocarriers, reaching the brain can be possible.
Nanocarriers can be made of many different materials and nowadays there are many types of nano-things that you can read of in research papers: liposomes, solid lipid nanoparticles, polymeric nanoparticles, inorganic nanoparticles, dendrimers, micelles, nanotubes, nanorods… Each type has its own characteristics in terms of size, shape, toxicity profile and drug delivery potential.
Why are nanocarriers used in cosmetics?
But we’re not here to talk about nanomedicine. We’re here to talk about cosmetics. The thing is, that most of the nanomaterials developed for drug delivery purposes have been borrowed also by the cosmetics industry. And since the journey from discovery to the market is definitely shorter for cosmetics, they began to appear on the market already back in the ’90s, whereas for nanomedicine we can only count on few products available nowadays.
The reasons why nanocarriers and nanosized objects have found application also in cosmetics are partially the same as in nanomedicine, but there are in addition some marketing-related reasons.
Nanomaterials can be used in cosmetics mainly with the following purposes (3):
- As active ingredients. This is the case of the UV-filters (zinc and titanium oxides) and of the “appearance enhancers” like arbutin and nanoparticles used in concealer and make-up compositions. Such ingredients simply give better performances in nano form than otherwise.
- As formulation aids. Like in the case of nanomedicine, nanomaterials can improve the formulation stability and performance of certain ingredients that would be otherwise unstable in the rest of the formulation, incompatible with some ingredients, or simply insoluble in the formulation medium.
- As nanocarriers (delivery systems). Also in this case, the idea would be to use nanomaterials as carriers just as in nanomedicine, to improve the effectiveness of functional material in reaching a certain district. While in nanomedicine we can choose among a variety of administration routes and targets for the nanocarriers, in cosmetics we mainly speak of the topical application. Here, the main goal of the nanocarrier would be to enhance the permeation of the encapsulated payload across the skin. But pay attention: we’re still talking about effects on the skin and penetration across the most superficial skin layers, not about reaching the systemic circulation. That would be transdermic administration and hopefully no cosmetic product has such a goal in mind.
When we talk about nanotechnology and nanoparticles, we spontaneously connect these words with the term safety. Indeed, there is a lot of concern about the safety of nanomaterials, mainly because nanoscale objects don’t necessarily behave in the same way as their “bigger” counterparts.
In addition, the safety concerns about nanomaterials are not limited to the human exposure but extend to the environmental safety, including effects on the food chain and fish/animal toxicity (4).
This is why nanomaterials used in cosmetics must be previously authorised by the Scientific Committee on Consumer Safety (SCCS), that reviews the toxicological data available on the nanomaterial for which the autorization is requested (5). In addition, according to the EU Regulation 1223/2009, all ingredients present in the final product in form of nanomaterial must be labelled explicitly, with the word nano in brackets (6).
In the next parts, we will see the types of nanocarriers used in cosmetics and we will focus on the ones that we can find in supplier shops for hobbyist formulators.
(1) Allen and Cullis, Drug Delivery Systems: Entering the Mainstream, Science, 2004, 303 (5665), 1818-1822
(2) Kumari et al., Biodegradable polymeric nanoparticles based drug delivery systems, Colloids and Surfaces B: Biointerfaces, 2010, 75 (1), 1-18
(3) Mihranyan et al., Current status and future prospects of nanotechnology in cosmetics, Progress in Materials Science, 2012, 57 (5), 875-910
(4) Mu and Sprando, Application of Nanotechnology in Cosmetis, Pharmaceutical Research, 2010, 27, 1746-1749
(5) EUON – European Union Observatory for Nanomaterials, https://euon.echa.europa.eu/cosmetics (accessed April 22, 2020)
(6) Regulation (EC) No 1223/2009 of the European Parliament and of the Council of 30 November 2009 on cosmetic products