How to study active ingredient penetration into skin ?

In cosmetic industry and more generally in chemical formulation, it is important to understand active ingredients effects and how far they penetrate the different skin layers.

To ease skin penetration, some formulations include a liposome, a lipid bilayer vesicle used as a vehicle. The goal of this kind of formulation is to deliver the active ingredient to the targeted area of the skin to enhance its cosmetic effect. But it is difficult to accurately localize the active ingredient into the skin and to know if the correct skin area has been reached.

To track the active ingredient while penetrating the skin, we propose to follow it by including a hydrophilic fluorescent marker in the liposome.

Why epifluorescence microscopy?

Epifluorescence microscopy is an optical microscopy technique that relies on labeling the molecule of interest with a fluorescent probe.

It consists of the excitation of the fluorescent molecule by a laser (excitation wavelength) which will allow it, returning to a stable state, to produce a photon (emission length) which will be captured by a sensor (camera).

This approach allows to visualize labeled molecules or structures in biological samples.

DermoMeca®’s solutions

DermoMeca® shows how epifluorescence microscopy helps to follow up an active ingredient during skin penetration. An excellent tool to screen active ingredients or optimize formulations.

First, we studied product’s formulation to determine which fluorescent marker is the best candidate. Then, this marker is
included to the formulation.

To perform this analysis, we worked on human skin obtained from plastic surgery. The product, or active ingredient solution, has been applied in topic according different exposure periods.

Figure 1: Skin penetration of active ingredient included in a liposome over time.

SC: Stratum Corneum, BL: Basal Layer, D: Dermis. Scale: 100μm.

 

We also quantified the penetration of the product. We measured the fluorescent grey level according to the depth in the skin.

This measure is important to compare simultaneously quantity and penetration of a product.

Various readouts:

  • Optical imaging of the product penetration in skin
  • Quantification of fluorescent signal
  • Correlation of fluorescent intensity and skin depth to trace the product.

Benefits:

  • Visual information about the penetration of the active ingredient into skin
  • Semi-quantitative information concerning position and quantity of the cosmetic product.

CONCLUSION

With this study, we were able to determine if the active ingredient has been delivered to the targeted skin compartment.

Here, we showed that epifluorescence microscopy makes possible to follow up an active ingredient in a delivery system as liposomes.

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