Everyone’s Talking About: Hydrogel Eye Patches
- TRI Princeton
- Jan 16
- 5 min read
In recent years, beauty and biology have become increasingly intertwined, with products being developed for the market that contain ingredients specifically intended to have a particular outcome, for example brightening and firming the skin, reducing swelling, increasing hydration, and boosting elasticity. To achieve this, manufacturers often add active ingredients such as short-chain peptides, collagen, caffeine, niacinamide and hyaluronic acid – effectively building upon scientific foundations that have shown the ingredient to have an effect.
Hydrogel eye patches are no exception. These cosmetic items are usually gel-textured masks with active ingredients impregnated within the hydrogel substrate, intended to target skin worries such as tiredness, puffiness or dryness. After placement under the eyes, the active ingredients leave the eye patch and penetrate into the problematic area. They’re short-term items, designed to be worn for between 10 and 20 minutes, after which time they’re removed and any residual oil or product lightly patted into the skin. They often contain several ingredients, including peptides, collagen, caffeine, niacinamide, and hyaluronic acid, that all perform different functions. In this article we will consider each ingredient, its function, the chemical structure, and a possible mode of action.
Peptides
Peptides are small, low molecular-weight compounds usually containing between 2 and 50 amino acids which are joined by peptide (also called amide) bonds. The fact that they’re small means that they can be absorbed through the skin. However, they’re not to be confused with their larger cousins, proteins, which contain hundreds of amino acids and are usually structural components of body tissues, enzymes and antibodies. Both peptides and proteins play key roles within the body with functions including cell signaling, providing structure and transportation of biologically-relevant materials.
When it comes to cosmetic items, peptides are usually added to give a specific effect and, to do this, they’re often intended to target a particular biological process. Inclusion of small peptides into a formulations, such as palmitoyl tripeptide-38 (Matrixyl Synthe'6), can stimulate production of protein components within the extracellular matrix, such as collagen, leading to improved skin characteristics seen by users, Figure 1. Due to this, when peptides are included in a product, claims are often relating to restoring youthful skin or ‘defying the signs of aging’. A comprehensive review by Pintea and co-workers has considered the inclusion of peptides in cosmetic items, including the use of permeation enhancers to ensure they cross the skin barrier and are delivered to the target of interest.
Figure 1: Structure of palmitoyl tripeptide-38 (Matrixyl Synthe'6). CAS: 1101448-24-1
Collagen
Collagen is a structural protein that provides structure, strength, and support for skin, muscles, bones and connective tissue. Within the skin, collagen plays a key role in helping fibroblasts form in the dermis leading to new cell development. It also plays a role in the replacement of old, dead skin cells, as well as giving the skin structure, strength and elasticity.
As the body ages, the production of collagen slows, and breakdown of collagen occurs at a faster rate. This leads to signs of aging that are easily observed in the skin, including wrinkles, loss of elasticity (leading to sagging) and loss of firmness. Including collagen in products could go some way towards replacing collagen that has been lost, however collagen can’t be absorbed through the skin as the molecules are too large; collagen contained in cosmetic items usually sits on the skin’s surface, which can lead to skin looking more plump or more hydrated.
Caffeine
Caffeine is a common active ingredient within cosmetic items due to its ability to boost circulation, increase skin radiance, and its antioxidant and anti-inflammatory effects. These claims have been proven in vitro, with a 2007 study showing that application of a caffeine solution increases dermal blood flow and inhibits 5-α-reductase activity, leading to increased hair follicle growth. In vivo studies by Lademann and co-workers have shown that a contact time of 2 minutes between a caffeinated shampoo and the skin surface is all that’s required for penetration into hair follicles – and that the caffeine is still present after 48 hours, even with washing.
These studies often rely upon analytical chemistry techniques to ‘follow’ the caffeine (or other active) ingredient through the target of interest, for example the hair fiber or skin, Figure 2. At TRI, techniques that we can use to monitor active delivery or penetration include IR or Raman spectroscopy, microscopy and mass spectrometry.
Figure 2: Molecule of caffeine, the penetration of which can be tracked through the skin using spectroscopy. Bonds highlighted in blue are most suited to IR spectroscopy as they have a strong dipole. Bonds highlighted in green (C–H) are most suited to Raman spectroscopy as they are easily polarised. The C=N bond, highlighted in yellow, can be easily monitored by both techniques.
Niacinamide
Niacinamide, also known as nicotinamide, is a form of vitamin B3 used in skincare products to reduce areas of redness, hydrate, brighten and strengthen the skin, Figure 3a. Within the body, niacinamide is known to protect cells from death and inhibit the production of inflammatory mediators in both animal (in vivo) and in vitro models of oxidant-induced cell injury. It has emerged as a useful treatment for inflammatory skin disorders, with its exceptional safety profile meaning it is suitable as a long-term therapy for patients.
Furthermore, a recent publication by Björklund and co-workers probed how niacinamide can impact upon the stratum corneum’s (SC’s) lipid matrix organization, soft keratin structure, and water sorption behavior. They showed that while niacinamide is not hygroscopic, it can enhance water uptake into the SC at high humidity (95%+), but at lower humidity (60%) swells the keratin monomers, causing a plasticizing effect that increased SC flexibility under low humidity conditions. They also found that niacinamide interacts with the lipid matrix, influencing water distribution between the SC’s lipid and protein domains.
Figure 3: (a) Niacinamide, a form of vitamin B3 used in skincare products; (b) hyaluronic acid, a sugar found naturally in the body.
Hyaluronic acid
Hyaluronic acid, first isolated in 1934, is a sugar found within connective, epithelial, and neural tissues in the body, Figure 3b. It plays a role in many biological processes including wound healing, tissue regeneration, and joint lubrication, and has interesting viscoelastic properties and behaviours, as well as moisturizing and anti-inflammatory qualities. It’s these properties that render it attractive for inclusion in cosmetic items. It was first used in the 1970s and 1980s within ophthalmic surgery, due to its hygroscopic, rheological, and viscoelastic properties, and is now being used within dermal fillers and other cosmetic treatments as a means for addressing skin aging. The hygroscopic nature of hyaluronic acid is useful for hydration of the skin barrier – it can bind up to 1000 times its volume in water, meaning it can hydrate both the SC and the dermis, and it also shows promise as a treatment for wound healing.
A review by Bravo and co-workers recently sought to pull together data from several studies to see how hyaluronic acid impacts skin aging, as well as environmental influences on synthesis and degradation. They found that several clinical studies indicate that topical application of hyaluronic acid is a non-invasive and effective solution for improving skin appearance, as well as hydration and elasticity.
Hydrogel Eye Patches
So, going back to the hydrogel eye patches. Assuming that the active ingredients contained within them can cross leave the hydrogel to penetrate the skin, then there is reason to believe that they may work. Each of the active ingredients on their own has been shown – often in clinical trials – to have positive benefit.