Figure 1. Nanoparticle size distribution and permeability across sclera and sclera-choroid-RPE. A: Particle size distribution after 24 h storage in assay buffer used for transport studies. Majority of the particles are distributed around the 50 nm particle size with another small group of particles of higher size distribution. B: Particle size distribution after 24 h storage in assay buffer containing 0.1% tween-20. In the presence of the surfactant, the particle size distribution shifts towards greater particle size indicating probable particle aggregation. C: Transport of nanoparticles (20 nm; 100 µg/ml) across isolated bovine sclera and sclera-choroid-RPE. The 20 nm particles can cross the sclera but not the sclera-choroid-RPE combination to any quantifiable extent. D: Transport of nanoparticles (20 nm; 100 µg/ml) across isolated bovine sclera and sclera-choroid-RPE in the presence of 0.1% tween-20. The particle transport across sclera is reduced in the presence of surfactant probably due to the shift in particle size distribution. Data are expressed as mean ± s.d. for n = 5-6. No quantifiable transport was observed either across the sclera or the sclera-choroid-RPE with the 200 nm particles.