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Solid Peptide Nanoparticles - Structural Characterization and Quantification of Cargo Encapsulation

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Publication date 2010
Author Dittrich C., Meier W.,
Project Nanostructured Polymers
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Original article (peer-reviewed)

Journal Macromolecular Bioscience
Volume (Issue) 10(12)
Page(s) 1406 - 1415
Title of proceedings Macromolecular Bioscience
DOI 10.1002/mabi.201000221

Open Access


CD3ac, an uncharged and strongly hydrophobic 10 amino acid peptide (Ac-LK(Ac)-LK(Ac)-LK(Ac)-LW-DL-LW-DL-LW-DL-LW-NH2) was synthesized and purified. The peptide readily dissolves in ethanol and - upon solvent exchange to water - assembles into solid spherical particles with diameters of around 500 nm and low size-polydispersity. CD3ac self-assembles in a convenient one-step-process in the absence of a templating two-phase solvent system or any other templating agents. Circular dichroism reveals a gramicidin-like secondary structure, which can be attributed to the presence of D-leucine, whereas LCD3ac, a peptide of identical constitution yet composed entirely of L-amino acids precipitates amorphously. The unacetylated derivative of LCD3ac (LCD3) displays alpha-helical character in circular dichroism. During the process of bead formation, CD3ac can take up and enrich water-soluble and - insoluble cargo compounds, which is exemplified by the encapsulation of rose bengal (RB) and 5-carboxy-fluorescein (CF), two xanthene derivatives. We confirmed their presence in CD3ac beads by confocal fluorescence microscopy and quantified the encapsulation efficiency by absorption measurements of dissolved RB-containing peptide bead suspensions. Loaded CD3ac beads consist of up to 40 mol-% RB, which corresponds to a logarithmic partition coefficient of 2.95. To the best of our knowledge CD3ac is the first peptide synthesized by Fmoc chemistry which forms solid particles in the nano-and micrometer size range and holds promise for drug delivery applications.