Study On PLGA Nanoparticles Modified With A Cell Penetrating Peptide (Penetratin) And A Non-classical Secretory Peptide (Sec)

Protein and peptide drugs often show poor oral bioavailability. This can beattributed to two major barriers which these drugs meet with in humangastrointestinal tract:(1) the large molecular weight and strong polarity of protein andpeptide drugs lead to low partition coefficient and furthermore, poor ability to passthrough the gastrointestinal mucosa, thus, protein and peptide drugs can not beeffectively absorbed;(2) peptide and protein drugs are prone to be degraded bygastric acid and digestive enzyme in the gastrointestinal tract and lose biologicalactivity. In order to solve the above-described problems and to improve the oralbioavailability of peptide and protein drugs, the PLGA nanoparticles modified with acell penetrating peptide (Penetratin) and a non-classical secretory peptide (Sec), andthe fusion peptide of Sec and Penetratin (SecPen) were prepared in present study.PLGA nanoparticles were parapared by a multiple emulsion-solvent evaporationmethod and PEMA was selected as the emulsifier. The influences of preparationformulations and process conditions on particle size and entrapment efficiency ofPLGA nanoparticles were investigated, including the concentrations of PLGA andPEMA, volume ratio of inner aqueous phase to oil phase, volume ratio of oil phase toexternal aqueous phase, and ultrasonic power. The optimum preparation formulationand process condition were1%PEMA,3%PLGA, the volume ratio of inner aqueousphase, oil phase to external aqueous phase1:6:30, and the ultrasonic power of550W.The PLGA nanoparticles obtained from the optimized formulation had spherical andsmooth surface, and uniform size distribution with a mean particle size of303.1nm.Its zeta potential was about-53.1mV and entrapment efficiency was43.8%approximately.On this basis, the freeze-drying process condition of FD4-PLGA-nanoparticlesuspension was investigated by evaluation of nanoparticle appearance, particle size,and entrapment efficiency after lyophilization of nanoparticles. It was found thatFD4-PLGA-nanoparticle could be protected effectively from aggregation during thefreeze-drying process by adding a total concentration of10%, the mass ratio of1:1 sucrose and mannitol as lyophilized protective agent to the nanoparticle suspensionbefore freeze-drying.Finally, the FD4-PLGA-nanoparticle was modified by conjugating the celltransport peptide (Penetratin, Sec, Sec-Pen) to the nanoparticles surface. The resultshowed that all the peptides could be detected respectively in the modifiednanoparticles after coupled reaction. It was evident that the method of modifyingnanoparticle with cell transport peptides, namely，choosing PEMA as the emulsifier toprepare PLGA nanoparticles, then conjugating the peptides to the nanoparticle surface,was feasible.