Pitfalls in using fluorescence tagging of nanomaterials: tecto-dendrimers in skin tissue as investigated by Cluster-FLIM

PIERRE VOLZ; PRISCILA SCHILRREFF; ROBERT BRODWOLF; CHRISTOPHER WOLFF; JOHANNES STELLMACHER; JENS BALKE; MARIA J. MORILLA; CHRISTIAN ZOSCHKE; MONIKA SCHAFER-KORTING; ULRIKE ALEXIEV

ANN. N. Y. ACADEMY SCIEN.

WILEY

Año: 2017 vol. 1405 p. 202 - 214

1749-6632

Targeted topical application promises high drug concentrations in the skin and low systemic adverse effects. To locate drugs and drug-delivery systems like nanocarriers, fluorescent dyes are commonly used as drug surrogatesor nanocarrier labels in micrographs of tissue sections. Here, we investigate how labeling degree, concentration of fluorophore, and nanocarrier may affect the interpretation of these micrographs. False-negative penetration results due to inter- and intramolecular quenching effects are likely. Using tecto-dendrimers as an example, we present adetailed analysis of pitfalls inthe (semi-)quantitative evaluationof skin nanocarrier penetration. Fluorescence lifetime imaging microscopy (FLIM) allows distinguishing the target fluorescence of dye-tagged nanocarriers from skin autofluorescence, providing a highly sensitive tool for clear-cut localization of the nanocarriers. Cluster-FLIM images reveal that FITC-labeled tecto-dendrimers penetrate the stratum corneum of human skin ex vivo and reconstructed human skin but do not cross the tight junction barrier.