[Study on the designed self-assembling peptide as potential drug carrier by fluorescence spectra].

Amphiphilic peptide is becoming attractive as a potential drug carrier to improve the dissolvability of hydrophobic drugs in aqueous system thus facilitating the drug undertaken by target cells. Here, we reported the ability of a novel designed self-assembling peptide RGA16 (Ac-RADAGAGARADAGAGS-NH2) in drug encapsulation and transfer into lipid vesicles. Pyrene was used as a model hydrophobic drug, and egg phosphatidylcholine (EPC) vesicles were used as plasma membranes mimic. It was found that the pyrene and peptide formed complex in water with mechanical stirring, and the time duration over which the complex formed was about 5 days. Initial evidence of the association between RGA16 and pyrene was the observation of a clouding phenomenon. Further investigation on the interaction between RGA16 and pyrene was carried out using fluorescence spectra and scanning electron microscopy (SEM). SEM micrographs showed that pyrene crystals and peptide were absorbed by each other and the size of the pyrene-peptide complexes was larger than 10 microm, which provided an evidence for the encapsulation of pyrene molecule by the amphiphilic peptide. The steady-fluorescence excitation profiles showed that the pyrene was presented in the crystalline form when stabilized by RGA16 and molecularly migrated from its peptide coating into the membrane bilayers of EPC vesicles when the suspension was mixed with EPC vesicles. The release behavior of pyrene into EPC vesicles was investigated by steady-fluorescence emission spectra, and a calibration curve for the amount of pyrene released into the EPC vesicles at a given time was used to determine the final concentration of pyrene released into lipid vesicles from peptide-pyrene complex. It was found that the pyrene concentration in EPC vesicles was displayed as a function of time. The data presented in the present work suggested that the novel designed amphiphilic peptide could stabilize the hydropholic drug in aqueous solution and deliver it into the membrane bilayers of EPC vesicles.