620 Bull. Korean Chem. Soc. 2011, Vol. 32, No. 2 Liang Wang and Xiao-jun Zhao
Dynamic Research of a Potential Carrier
for Hydrophobic Compound Model Pyrene Using Amphiphilic Peptide EYK
Liang Wang and Xiao-jun Zhao†,*
West China Hospital Nanomedicine Laboratory, Center for Regenerative Medicine and Institute for Nanobiomedical
Technology and Membrane Biology, West China Hospital, Sichuan University, Chengdu 610065, Sichuan, P. R. China
†Center for Biomedical Engineering, NE47-379, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA
Received November 23, 2010, Accepted December 14, 2010
In recent years, the study of self-assembly peptide used in drug delivery system has been attracted great interest from
scientists. In the category are self-assembly peptides in the structure either with one hydrophobic surface and another
hydrophilic or a hydrophobic head and a hydrophilic tail. Here, we focus on a novel designed peptide EYK with double
amphiphilic surfaces, investigating on the capability of peptide as a carrier for hydrophobic compound model pyrene.
The fluorescence data presented the dynamic process of the transfer, showing that the pyrene was in the crystalline
form in peptide solution, and molecularly migrated from its peptide encapsulations into the membrane bilayers when
the peptide-pyrene suspension was mixed with liposome vesicles. The results indicated that the peptide EYK could
stabilize hydrophobic pyrene in aqueous solution and delivered it into EPC liposome as a potential carrier.
Key Words: Amphiphilic peptide EYK, Pyrene, Hydrophobic compound carrier, Fluorescence spectroscopy,
It is crucial in pharmaceutical industry for hydrophobic compoundsto fix out the problem of lower solubility in aqueoussolution and exploit an appropriate vehicle to deliver them tothe target cell or tissue. The discovery of the self-assembly peptide,emerged as a promising nanomaterials, has chart anewdirection for us. This category nanomaterial has been widelyused in the area of nanoscience and biomedical engineeringsuch as cell and tissue cultures,1-4 biologicalsurface engineering,5-6 membrane protein stabilizations.7 In recent years, thesepeptides have also been attracted great interest fromscientistsused for drug delivery system.8-10As we know, the self-assembly peptides lead to a uniqueamphiphilic structure because of numbers of hydrophobic andhydrophilic residues in the amino acid sequence. The propertymade them wide useful for combination with drug moleculesIn order to investigate the drug delivery system of peptide andto improve the compatibility between peptides and hydrophobiccompound, a novel type of peptide need to be designed. In thisresearch, we employed a newly designed lego-type peptide EYKwith double amphiphilic surfaces, different from the classic oneswith one hydrophobic surface and another hydrophilic, for the delivery system.11 It is expected that the peptide EYK could stabilized the hydrophobic drug model pyrene and transfer the
pyrene to EPC vesicle. The steady-state fluorescence spectroscopy could exhibit the dynamic process of transfer. Experimental Part Chemicals. The original peptide (EYK short for sequence:AEAEYAKAK; theoretical mass 980.02) used in our study was commercially synthesized and purified (> 95%) by Shanghai
Bootech Bioscience & Technology Co. Ltd. Egg Phosphatidylcholine(EPC) was purchased from Sinopharm Chemical Reagents
Co., Ltd., Shanghai, China. Pyrene (99%) was purchasedfrom Sigma Aldrich and was recrystallized three times beforeuse. The rest chemicals used in theexperiment were acquiredfrom Chengdu Kelong Chemical Reagents Co., Chengdu, China.EPC liposome was prepared by the film-ultrasonic method.1The size of liposome was monitored by using a Malvern ZetasizerNano ZS analyzer and the lipid concentration was determined.All aqueous solutions were prepared using deionizedwater (Elix Water Purification System, Millipore, MA, U.S.A.).Preparation of Colloidal Suspensions of Pyrene Crystals.Appropriate pyrene was added into freshly prepared peptideEYK solutions in a 10 mL vial. The mixed peptide-pyrene solutionswere prepared to obtain the concentrations of 0.5 mg/mL
for pyrene and peptide. The sample was kept on magnetic stirrersuntil equilibrium was reached in about 72 h. The solution wasdeemed at equilibrium when their fluorescence spectrums didnot change in 24 hours.Steady-state Fluorescence Measurements. Fluorescence spectrameasurements were performed on a Hitachi F-7000 spectrofluorophotometerwith a stir accessory at room temperature.The solutions were operated in a quartz fluorescence cuvetteof 1 cm2 cross-section. The following parameters were used inexperiments except special indication. Excitation and emissionslits were both set to 2.5 nm. The excitation wavelength wasset to 336 nm, and the emission fluorescence spectra were detectedfrom 350 to 600 nm, with scan speed of 240 nm/min;response time, 0.1 s; PMT Voltage = 400 V Excitation spectra
were recorded at selected emission wavelength (373 or 470 nm),with scan speed of 240 nm/min.Pyrene Transfer Experiments. For the experiment of the migration
of pyrene from the EYK-pyrene solution into the EPCDynamic Research of a Carrier for Pyrene Using Peptide EYK Bull. Korean Chem. Soc. 2011, Vol. 32, No. 2 621Figure 1. Pyrene crystals ([pyrene] = 2.5 × 10‒3 M) in water (left) and
with peptide EYK ([pyrene] = 2.5 × 10‒3 M, [EYK] = 5.1×10‒4 M = 0.5mg/mL) in aqueous solution (right) after stirring both solutions for 3 h.
Figure 2. AFM images of pyrene crystals in different aqueous solutions
after stirring for 72 h. (a) with peptide EYK in aqueous solution
([pyrene] = 2.5 × 10‒3 M, [EYK] = 5.1 × 10‒4 M); (b) In water ([pyrene]
= 2.5 × 10‒3 M); Scale of the black bar is 500 nm.