Biomedical Engineering Reference
In-Depth Information
Fig. 4
(continued)
of nanocrystals. The mechanism will be explained in detail using the example of
rutin and hesperidin (Petersen
2006
).
Delivery of actives to the skin or any other target site can be studied by measuring
concentrations at the target site or ideally by measuring the resulting effect.
Measuring the effect assesses the overall performance of a delivery formulation,
especially being essential when comparing two molecule derivatives (e.g. original
molecule and derivative, e.g. glucoside). Rutin and hesperidin are poorly soluble
antioxidants, the solubility is so low that incorporation as normal micrometer powder
into a cream will lead to no effect. Therefore in the study by Petersen soluble rutin
was made by glucosidation. The rutin-glucoside was compared in its antioxidative
capacity to nanocrystals of the original poorly soluble rutin and in addition to
hesperidin (Petersen
2006
). In addition a formulation with alpha tocopherol acetate
was run, which should make the skin more sensitive. To quantify the activity in the
skin (= effect), the sun protection factor (SPF) was determined in humans under
UV exposure. Antioxidant activity increases the SPF. Measurement of penetrated
concentrations (e.g. tesa stripping test, biopsy) would have been less conclusive,
because it does not consider potential different activities of the molecules in the cell
(original versus glucoside). The overall performance of a formulation is a function
of delivery efficiency and activity of the delivered type of molecule.
The rutin glucoside was dissolved at a concentration of 5.0% in the dermal test
formulation. The nanocrystal formulation contained a depot of nanocrystals and a
dissolved concentration of rutin of about 0.01%, i.e. 500 times less dissolved active.
In vivo the rutin glucoside formulation increased the SPF by 27%, the rutin
nanocrystal dermal formulation by 59%, i.e. two times increase at 500 times less
dissolved molecules. Simplified it could be stated that the nanocrystal formulation
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