荧光光谱对自组装多肽作为药物载体的初步研究

为解决疏水性药物普遍存在的因水中溶解度低而给药困难、生物利用度低的问题，采用了新型两亲性自组装多肽RGA16(Ac-RADAGAGARADAGAGS-NH₂)作为载体包裹和释放疏水性模型药物。以芘为模型疏水性药物，以鸡蛋卵磷脂脂质体模拟细胞膜，通过稳态荧光光谱表征和测定芘的存在形式和浓度。两亲性自组装多肽RGA16能够在水溶液中稳定模型疏水性药物芘的晶体。扫描电镜图像显示多肽RGA16与芘晶体相互吸引，两者形成10 μm以上大小的复合体。在机械搅拌下多肽RGA16与水溶液中的芘相互作用5 d左右形成稳定的胶体混悬液(多肽-芘复合体)。被多肽包裹时，芘以晶体的形式存在。而当与EPC脂质体溶液混合时，芘可从多肽的包裹中以分子形式释放到EPC的双层膜中。芘从自组装多肽所稳定的胶态晶体向EPC脂质体释放的过程采用连续时间扫描稳态荧光光谱加以观察。通过将释放过程中芘单体的荧光强度与标准曲线相比较，确定了特定时间点EPC脂质体中芘的转移量。以上结果表明：该两亲性自组装多肽RGA16具有作为小分子量疏水性药物载体的潜力。

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 hydrophobie 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-NHz) 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 theobservation 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 μm, 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.