IIT. India: Wouldn’t it be nice to have a transparent sunscreen
lotion and yet protect your skin from harmful UV ? Engineered
nanoparticles can now provide the right kind of mask.
Sunscreen
products work by absorbing or scattering UV radiation. Formulating
superior sunscreen is of utmost importance in protecting our skin from
sunburn, skin cancer and other deleterious effects. This is especially
true for people with light skin due to lower concentration of melanin in
their skin, which is the natural absorber and dissipater of UV
radiation. The normal ZnO used as an active ingredient in sunscreen are
microdimensional and because of this, they scatter light and appear
white when applied on the skin, which is not aesthetically pleasing.
Hence, sunscreen industry is now considering ZnO nanoparticles (NPs) as
an efficient UV blocker, which can reduce the scattering problem faced
by its bulk counterpart, thereby making it appear transparent when
applied to skin surface. However, these transparent ZnO nanoparticles
(NPs) have UVA (~385 nm) emission, which penetrates up to the dermal
layer of skin. This highly penetrating UVA emission from ZnO NPs will
enhance the generation of cancer inducing radicals. Therefore, the
elimination of this harmful UVA emission from ZnO NPs is much sought
after for the development of safer ZnO NPs based sunscreens.
In
an effort to tackle this problem, research scholar Mr. A. Asok, Prof.
A. R. Kulkarni and Dr. M. N. Gandhi have come up with an ingenious
solution that promises to play a significant role in the science of
sunscreen active ingredients. They have engineered a more potent form of
zinc oxide (ZnO), the core ingredient in most conventional sunscreens,
by introducing nonstoichiometric defects in the zinc oxide
nanocrystals. They refer to it as engineered zinc oxide (EZnO)
nanoparticles. These EZnO NPs have characteristic optical transition
profiles which can bypass the harmful UVA emission present in normal ZnO
NPs, at the same time making it a broad band UV absorber and broad band
visible emitter. This visible emission is neither harmful nor dangerous
for the skin when compared to UVA emission from normal ZnO NPs. In
addition to its improved safety, the broad band emission from EZnO NPs
matches well with the in vivo human skin autofluorescence. This property
of EZnO also imparts an illusion of smoothing wrinkled skin and this
camouflaging effect can find its utility in wrinkle free creams. Thus
EZnO clearly stands out as the potential and promising candidate for
one of the major ingredients of sunscreen formulation not only for its
protecting ability from harmful UVA emission but also for its cosmetic
value.