25 June 2019
MIT chemical engineers have devised a new way to convert liquid nanoemulsions into gels, offering new ways to deliver drugs through the skin.
Nanoemulsions, which are tiny droplets of one liquid suspended with another liquid, resemble a similar combination of an oil-vinegar salad dressing mixture except the droplets are smaller in size, allowing them to remain stable for long periods of time. These liquid nanoemulsions can be easily converted to a gel at body temperature (37oC).
This novel material has captured the interest of pharmaceutical companies, primarily because it offers a new way to deliver drugs through the skin. Due to their small size of the material, hundreds of nanometers can effectively permeate the skin, allowing for nanoemulsions to be delivered topically, through ingestion or through nasal inhalation.
Researchers demonstrated how they could incorporate ibuprofen into the droplets, proving that this process can be useful as an innovative drug delivery through skin.
Nanoemulsions are desirable because they have a higher ratio of surface area to volume, allowing them to carry larger payloads of active ingredients like drugs.
Patrick Doyle, Professor of Chemical Engineering at MIT and the senior author of the study, and his team have been concentrating on finding lower-energy strategies for making nanoemulsions, to create an easier process for large scale industrial manufacturing.
Although surfactants (detergent-like chemicals) can speed up the formation of emulsions, many are not FDA approved for use in humans. Therefore, researchers chose two surfactants which have been FDA approved and are less likely to irritate the human skin. The researchers added a small amount of polyethylene glycole (PEG) to reduce the solution down to form smaller droplets.
Professor Doyle states that with this approach, little energy is required, and in fact, 'a slow stirring bar almost spontaneously creates these super small emulsions.'
Researchers incorporated heat-sensitive polymers called poloxamers (FDA-approved) which are used in drugs and cosmetics. This eases the process for liquid nanoemulsions to be converted into solid gels, upon reaching room temperature. The hydrophobic regions of polymers attach themselves to the droplets when drops of the liquid emulsion reach room temperature, forcing them to almost instantaneously create a jelly like solid by packing together more tightly.
Researchers discovered they can tune the properties of the gels, by changing the size of the emulsion droplets, the concentration and the structure of the pluronics. As well as this, they can change its elasticity and yield stress which measures how much force is needed to spread the gel.
Professor Doyle is now investigating various methods of incorporating different pharmaceutical ingredients into the gel, making it easier for drugs to be applied through the skin, for different medical purposes.
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