Keeping up with the science of cosmetic injectables

There’s a good chance that you or someone you know has considered cosmetic injectables; medical procedures that involve injecting a substance under your skin to change some part of your appearance.

Whether you want to reduce the appearance of wrinkles in your forehead, increase the fullness of your lips, or reduce the amount of fat under your chin – there’s a chemical substance that can be injected to do it.

But what exactly are these substances? How do they work? And are there risks associated with going under the needle?

Start with the classic: Botox

Botox is a drug made from botulinum toxin, a neurotoxin protein produced by the bacterium Clostridium botulinum. In large amounts, this neurotoxin can cause botulism, a rare but serious illness that affects the nerves and can even result in death.

Botulinum toxin actually consists of 7 different subtypes of toxins, but only botulinum toxin types A and B are used clinically. Type A is the one approved as a cosmetic injectable and it can be used soften the appearance of facial wrinkles and adjust brow positioning.

But how does it work? Well, it blocks nerve signals from reaching injected muscles, which stops them from being able to contract. The resulting localised muscle weakness or paralysis prevents the muscles from forming lines in the skin.

Botulinum toxin is a type of enzyme called a protease and it cleaves or cuts specific proteins that are essential for the release of neuro-transmitters. These are chemical messengers used by the nervous system to transmit messages between neurons or from neurons to muscles.

Specifically, it blocks the release of the neurotransmitter acetylcholine from presynaptic motor neurons. But the effects of Botox ultimately aren’t permanent, because function is recovered by sprouting new, unaffected nerve terminals, which usually takes three to four months.

Botulinum toxin type a protein structure. Credit 5 ht2ar via wikimedia commons
Botulinum toxin type A protein structure. Credit: 5-HT2AR via Wikimedia Commons

Hyaluronic acid fillers are becoming increasingly popular

Dermal fillers are substances injected into the skin to plump out wrinkles or alter the shape of the face in some way – for instance, adding volume to the lips or cheeks, or altering the shape of the nose or jawline.

One popular substance used in fillers is hyaluronic acid: a long, linear sugar molecule found naturally throughout the body. It’s one of the most hydrophilic, or water-loving, molecules in nature and just one gram of it can bind up to 6 litres of water – kind of like how gelatine binds up water to form jelly.  

Hyaluronic acid gel can be modified to have different physical properties, which then alters the ways in which it can be used. By introducing chemical bonds to crosslink between the hyaluronic acid strands the firmness and stress-resistance of the substance can be increased, which is important when defining or altering the appearance of features like the nose, jawline, or cheekbones.

Hyaluronic acid injections aren’t permanent and are slowly broken down and re-absorbed into the body over time. This is done by an enzyme called hyaluronidase, which is found throughout the body. It cuts up the long hyaluronic acid polymers into smaller fragments that are then further degraded by other enzymes.

Other substances can also be used as dermal fillers

Though less popular than hyaluronic acid, collagen can also be used as a cosmetic injectable filler.

Collagen is the major structural component of the dermis in the skin and provides strength and support to it. As we age, the production of collagen decreases and that results in the reduction in skin volume we see in aged skin.

It was the first material to be approved by the U.S. Food and Drug Administration for injection into facial scars, furrows, and lines. Collagen injections replenish the collagen lost from the face and can be derived from cows (bovine), pigs (porcine), or even human cells.

Scanning electron micrograph sem of collagen bundles. Credit science photo library steve gschmeissner getty images
Scanning electron micrograph (SEM) of collagen bundles. Credit: Science Photo Library/STEVE GSCHMEISSNER/Getty Images

But, what if instead of adding volume, you want to get rid of it? Lipolytic injections are a non-surgical way to reduce localised subcutaneous fat deposits, like the one found under your chin.

The substances phosphatidylcholine (PC) and deoxycholic acid (DC) are used to chemically reduce the number of fat cells around the injection site by causing fat cells to die. DC is a bile salt that induces fat cell death by acting as a detergent to break apart the cell membrane. The exact mechanism of action for PC isn’t well understood, but its thought that it stimulates enzymes called lipases to break down fats.

Before you go out and book an appointment, a quick safety PSA.

With cosmetic injections, like any medical procedure, there are always risks involved and sometimes these risks can be serious and even life threatening.

Anyone that performs a cosmetic injection must have extensive knowledge of facial anatomy, as well as the required training and experience, so that the risk of something adverse happening can be minimised. The Australian Therapeutic Goods Association recommend finding a registered practitioner and making sure that the product used in your procedure is registered by checking the Australian Register of Therapeutic Goods, which lists all of the products that can be legally supplied in Australia.

Please login to favourite this article.