Preparation, Characterization Of PAMAM Dendrimers-coated Liposomes And Evaluation For Ophthalmic Drug Delivery

Eye drops was a traditional dosage form of eye treatment. The losses of drug was much, and drug entering eye was only 5% because of blinking eye movement and lacrimonasal duct drainage and so on. Puerarin(PUE), cmmonly ued in treatment of glaucoma, was chosen as the model drug. PAMAM could open intercellular tight junction and enhance the permeability cell membrane. We prepared PAMAM dendrimers-coated liposomes and the in-vitro transcorneal penetration, precorneal residence time, residual amount of puerarin within corneal of they were evaluated. A series of relative studies were carried out.Firstly, the method was developed for the determination of PUE concentration in liposomes and entrapment efficiency by HPLC. We prepared PUE liposomes by film-ultrasonic technique and the formulation and process were investigated and optimized using the single factor research, with encapsulation efficiency as judge index. The results showed that when soybean phospholipids / cholesterol / PUE was 10 / 2 / 1, entrapment efficiency was the maximum.Secondly, PAMAM dendrimers-coated liposomes encapsulated puerarin were prepared and the particle size, zeta potential were investigated compared with uncoated liposome. Fluorescein isothiocyanate (FITC)-labeled PAMAM dendrimers were prepared to study adsorption rate. Transmission electron microscope and laser confocal scanning microscopy were used to explore the morphology and structure of PAMAM-coated liposomes. The results showed that the size of the coated liposomes was little larger than that of the uncoated liposome but no significantly difference and the zeta potential became positive from negative and increased along with ration of PAMAM. The PAMAM coating on the surface of liposomes could be observed by transmission electron microscope and laser confocal scanning microscopy. The clad ratio of PAMAM G2 was bigger than PAMAM G3.Thirdly, the freeze-drying conditions, release behavior and stability of PAMAM dendrimers- coated liposomes encapsulated puerarin were separately investigated. The results showed that the cumulative release of PAMAM coated liposomes was similar to that of uncoatd liposome with slower release property, and the stability was bad at room temperature, but showed high stability under low temperature. Freeze-drying experimental results revealed that mixed stereo protective agent (mannitol, sucrose) showed better protective effect.Fourthly, the invitro transcorneal penetration were evaluated compared with PUE drop solution and uncoated liposome. Investigated the affect of different proportion (PAMAM / phos- pholipids=0.1,0.5,1.0,2.0mol%) on corneal penetration and the penetration parameters were obtained. The results showed that The cumulative penetration, (steady state fluxes) and (permeability coefficients) of PAMAM coated liposomes were greater than PUE drop solution and uncoated liposome(P<0.01), meanwhile the proportion PAMAM G2(1.0mol%) and PAMAM G3(0.5mol%) were the best for improvement of corneal penetration(P<0.01). At the same time, the PAMAM coated liposomes were nonirritant and could remarkably prolong corneal residence time, increase residual amount of PUE within cornea, compared with uncoated liposome and PUE drop solution (P<0.01). The PAMAM coated liposomes was promising as a novel ophthalmic drug delivery system.