Liposomes for effective drug delivery to the ocular posterior chamber

Abstract

Background: Age-related macular degeneration (AMD) is a leading cause of severe visual deficits and blindness. Meanwhile, there is convincing evidence implicating oxidative stress, inflammation, and neovascularization in the onset and progression of AMD. Several studies have identified berberine hydrochloride and chrysophanol as potential treatments for ocular diseases based on their antioxidative, antiangiogenic, and anti-inflammatory effects. Unfortunately, their poor stability and bioavailability have limited their application. In order to overcome these disadvantages, we prepared a compound liposome system that can entrap these drugs simultaneously using the third polyamidoamine dendrimer (PAMAM G3.0) as a carrier.

Results: PAMAM G3.0-coated compound liposomes exhibited appreciable cellular permeability in human corneal epithelial cells and enhanced bio-adhesion on rabbit corneal epithelium. Moreover, coated liposomes greatly improved BBH bioavailability. Further, coated liposomes exhibited obviously protective effects in human retinal pigment epithelial cells and rat retinas after photooxidative retinal injury. Finally, administration of P-CBLs showed no sign of side effects on ocular surface structure in rabbits model.

Conclusions: The PAMAM G3.0-liposome system thus displayed a potential use for treating various ocular diseases.

Keywords: Antioxidative retinal damage; Berberine hydrochloride; Chrysophanol; Ocular drug delivery; PAMAM G3.0-coated compound liposomes; Transcorneal permeability.

Fig. 1

Schematic illustration of the design and evaluation of PAMAM G3.0-coated compound liposomes. a Synthesis process of PAMAM coated compound liposomes. Loading BBH and CHR into the different chamber of liposomes by thin film and active load, respectively, and PAMAM G3.0 was loaded into the surface of compound liposomes via electrostatic interaction. b Comprehensive evaluation of PAMAM coated compound liposomes including characterization, in vitro, in vivo transport efficiency, preliminary pharmacodynamics studies and opthalmic irritation studies

Fig. 2

Characterization of FITC-PAMAM coated  liposomes. a Verification of FITC onto PAMAM G3.0 via ¹H-NMR. b SEM image of FITC-PAMAM coated liposomes (scale bar = 1 μm). c The appearance of CBLs and P-CBLs taken with camera. d TEM images of CBLs and P-CBLs, the red arrow indicates the P-CBLs and white indicates CBLs (scale bar = 100 nm)

Fig. 3

Evaluation of the effectiveness of liposomes delivery. a Representative fluorescence images of various formulations containing Cou taken with long-term real-time dynamic live cell imaging analyzer. Following incubated for 24 h and then the cellular uptake of HCECs was captured and analyzed by real-time dynamic monitor (scale bar = 300 μm). b Intake count of various formulations. c Representative images of different formulation distribution in cornea after administration of respective formulation stained with Nile Red; the arrow indicates the corneal endothelium (scale bar = 50 μm). d In vivo pharmacokinetics evaluation following topical administration of various formulations

Fig. 4

Protection against photooxidative retinal damage. a Change of b-wave amplitude following topical administration of respective formulations for consecutive 14 days. b Fundus retinography of various formulations. c The protective efficacy evaluation of various formulations in the retina by staining hematoxylin and eosin (H&E) (scale bar = 20 μm). d Photographs of in vitro anti-ROS efficacy taken with a long-term real-time dynamic live cell imaging analyzer. e ROS level of various formulations. Data were presented as the mean ± SD (n = 3). **P < 0.01, ***P < 0.001

Fig. 5

Ophthalmic irritation studies. a Representative images of the tissue histology after P-CBLs instillation for 14 consecutive days (scale bar = 20 μm). b Observation of ocular surface using a silt lamp and camera, stained with 0.5% sodium fluorescein