Organic–inorganic nanocomposite gels as an in situgelation biomaterial for injectable accommodative intraocular lens

Abstract

We focus on the development of a novel injectable accommodative lens for intraocular applications, which is based on a thermosensitive hydrophobically modified poly(ethylene glycol) (HM-PEG) containing hydrophilized silica nanoparticles. We distinguished macroscopically, with changes in the temperature or concentration, two regions in the phase diagram for aqueous solution of HM-PEG: transparent sol and transparent gel. These changes occurred reversibly, without hysteresis, when the temperature was decreased. The temperature and concentration regime in which the gel formed are reduced by adding silica nanoparticles into the gel matrix. Small-angle neutron scattering measurements for nanocomposite gels provide good proof of a gel phase where the high shear-modulus is gained by a high inter-micellar correlation originating in the crystalline order. Under the condition of uniform distribution of silica nanoparticles with small size (2–5 nm) in the gel matrix, an increase in the refractive index up to 0.0667 was obtained for the nanocomposite gel compared with the native gel matrix without an increase in turbidity. This composite system could be formulated to match the modulus and the refractive index of the natural lens (∼1.411), and was easily extruded through a narrow-gauge needle. Rapid endocapsular gelation yielded an optically clear gel within the lens capsular bag. This technique enables us to validate methods to determine the biomechanics of the lens and its role in accommodation. The modification of the mechanical response and stability of the HM-PEG network by addition of silica nanoparticles was also investigated in detail.