Fluorescence studies on a designed self-assembling peptide of RAD16-II as a potential carrier for hydrophobic drug

The self-assembling peptide, RAD16-II (Ac-RARADADARARADADA-NH2), has been shown to have many great applications in nanotechnology and tissue engineering. But few studies have been carried out to study the application of self-assembling peptides as a drug carrier. We used hydrophobic drug pyrene as a model and liposome vesicles to mimic bilayer membranes to study the ability of RAD16-II in drug encapsulation and transfer to lipid vesicles. It was found that this designed self-assembling peptide was able to stabilize hydrophobic drug in aqueous solution and deliver it into lipophilic environment. Analysis of the fluorescence excitation spectra showed that pyrene was present in the crystalline form when stabilized by RAD16-II and was able to be dispersed in egg phosphatidylcholine vesicles. This suggested that pyrene was completely released from RAD-Py mixture into the bilayer membranes. Furthermore, the concentration of pyrene transferred into the vesicles was quantified and its transfer rate was determined. The scanning electron micrograph image showed that pyrene microcrystals and peptide were absorbed by each other and the size of the pyrene-peptide complexes was larger than 10 microm. These data further demonstrated that this type of ionic complementary oligopeptides was able to significantly encapsulate hydrophobic drug and provide a new type of nanomaterials for delivering drugs.