Next Generation Sunscreens

UV light can severely damage the skin and cause premature aging. Photoaging can be characterized by visible wrinkles, hyperpigmentation and uneven pigmentation of the skin, coarseness, laxity, telangiectasias, lentigines, and atrophy. The UV rays blasting down from the sun do more than burn your skin. They attack you right down to your DNA. That’s why there’s such a strong link between sun exposure and skin cancer. If you could somehow repair the sun-damaged DNA in your skin, you could go a long way toward reducing your risk of skin cancer. As a bonus, your skin would look younger and healthier.

There is increased awareness among people and also promotion of sunscreens by dermatologist in recent times. A recent review examined the association between sunscreen use and sun exposure, concluding that sunscreen use increased the duration of intentional sun exposure between 13% and 39%. Specifically, use of sunscreens with a higher SPF appeared to lengthen exposure times. The anticipated protection from sunscreen likely instills a false sense of safety, but more importantly, higher SPFs raise the threshold for sunburn.

 

In attempt to provide better protection increasing the number of agents or increasing quantity of application can have deleterious effects of contact dermatitis and systemic absorption.

 

” Though the awareness of sunscreen has increased the compliance with application and inadequate quantity of usage coupled with a false sense of safety increases sun exposure times and causes more damage than anticipated “

Typically sunscreens contain both organic and inorganic UV filters that combined are broad-spectrum and protect against the entirety of the UVA and UVB range and exert a “passive photoprotection” . Sunscreens are not effective once damage to skin cells has been generated after sun exposure. Because photoaging is due, at least in part, to UV-induced DNA damage, enhancing cellular DNA repair capacity would likely reduce photodamage. The delivery of substances that increase the repair of damaged DNA is an area of intensive research and may prove to be a valuable means to achieve protection against UV irradiation and decrease the incidence of photoaging. Conversely, “active” photoprotection” is represented by topical sunscreens including also antioxidants and liposome-containing DNA repair enzymes, which may constitute a photostrategy filling the current gap in sun protection.

Future Directions

DNA Repair Enzymes

When the skin is exposed to solar ultraviolet B (290 – 320 nm) radiation, damage to DNA incurs in the form of cyclobutane pyrimidine dimers (CPD) and pyrimidine (6 – 4) photoproducts  these are  repaired through nucleotide excision repair.

Various Topical DNA repair enzymes have been studied like photolyase, T4 endonuclease V and 8-oxoguanine glycosylase which are able to enhance the protective power of traditional sunscreens.

T4 endonuclease V (T4N5) is a DNA repair enzyme in bacteria. It has also been shown to recognize cyclobutane pyrimidine dimers, and to accelerate the repair of DNA in mammalian cells. The topical use of T4N5 liposomes has been investigated in patients with xeroderma pigmentosum, a defect in nucleotide excision repair of DNA, and found to have a protective effect on the appearance of basal cell carcinoma and actinic keratoses. Application of T4N5 liposomes immediately after UV exposure partially protects against sunburn cell formation.

 

Photolyase is naturally found within the skin, but most assuredly deplete with age.  Photolyase reverses DNA damage in cells and prevents cell death caused by UV exposure.  It has been shown in trials to reduce UVB radiation-induced dimers by 45% and to increase UV protection by 300%. Liposome-encapsulated photolyase is delivered to the skin within an hour of application.  It requires light for its activation, though any mild indoor light that passes through sunscreen should be enough for it to work properly.

 

Antioxidants

Ascorbic acid (vitamin C) is a plentiful antioxidant in the skin.It acts by neutralizing reactive oxygen species caused by UV irradiation and as a scavenger of free radicals. It is also reported that ascorbic acid has at least some photoprotective properties. Specifically, topical L-ascorbic acid protected  skin from UVB- and UVA-phototoxic injury as measured by erythema and sunburn cell formation.

 

The major antioxidant function of vitamin E is to prevent lipid peroxidation. It achieves this by scavenging peroxy radicals and thus arresting a chain propagation of new radicals that may threaten the integrity of cellular membranes. The largest body of evidence for a beneficial role of topical vitamin E exists for photoprotection.

Ubiquinone (ubidecarenone; coenzyme Q10) is a lipophilic antioxidant synthesized by all mammalian cells and critical for the protection of mitochondrial membranes. Idebenone is a synthetic derivative of ubiquinone that is more soluble and has potent antioxidant properties. It has been shown to inhibit lipid peroxidation and to maintain mitochondrial electron transport.It has been suggested that by quenching free radicals in the epidermis it has a beneficial effect on preventing and/or reversing photoaging.

Retinoids are the drugs histologically and clinically proven to reverse skin aging. Histologic changes in skin treated with tretinoin include epidermal hyperplasia, compaction of the stratum corneum, thickening of the granular layer, reduced melanocytic hypertrophy, restoration of cell polarity, increased new collagen formation, and normalization of the appearance of elastic tissue. It is likely that tretinoin, in addition to inducing collagen synthesis, also reduces collagen breakdown by inhibiting the UV radiation-induced matrix metalloproteinases.

New UV Filters

Newer products in sunscreen like Tinosorb S is oil soluble and stabilizes avobenzone and octinoxate. Tinosorb M consists of microfine particles (100-200 nm) dispersed within the aqueous phase of sunscreens and can reflect, scatter, and absorb UVR. Because of their relatively large size, Tinosorb filters rarely cause allergic contact dermatitis, systemic absorption, or endocrine-like effects.

A novel technology was developed by Sol-Gel Technologies, Ltd, the microencapsulation approach loads UV filters into 1-um silica shells. By means of this technique, products with sunscreen agents that have traditionally been incompatible can be prepared. Because the active ingredients do not directly contact the skin, microencapsulation may help to lower the incidence of contact allergies and systemic sunscreen absorption.

SUNSPHERES are filled with water and made of styrene/acrylate copolymers that do not absorb UVR. Once these products are applied to the skin, the water escapes the SUNSPHERE, and the remaining hollow capsule scatters incident light, increasing the chance that light will contact the UV filters and improving the product’s effective SPF by 50% to 70%.

 

 “Sunscreens are like fire retardant gels protect from UV rays, Antioxidants are like fire extinguishers. They put out the fires caused by UV light or pollution, which lead to inflammation in the skin and ultimately to DNA damage. And then DNA repair enzymes  are like getting a good contractor in to rebuild any structural harm that still occurs”

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