Bionic Soft Lens Materials Based on Self-Assembling Amphiphilic Block Copolomer/Nanoparticle Hybrids

In this study, the potentiality to investigate hydrogel which can be injected into crystalline lens is studied. Hydrogel base on thermo-sensitive poloxamer 407 block copolymer is prepared by photo-polymerization. The terminal hydroxyl groups in poloxamer 407 are acrylated to form poloxamer 407 macromer as the reactive polymer, and is confirmed using NMR and FTIR spectrometry. The lower critical sol-gel temperature of poloxamer 407 macromer is higher than poloxamer 407 itself when the concentration is below 20%, but not significant above 22%. The Young’s modulus would be decreased according to the higher ratio of poloxamer 407 that in poloxamer hydrogel or shorter UV irradiation times, but the concentration of photo initiator is not significant.
In order to increase the refractive index of poloxamer hydrogel, titanium dioxide nanoparticle is introduced using the titanium (Ⅳ) chloride as titanium source. Titanium chloride through the process of hydrolysis, adjust pH, precipitate and acid-peptization can get the rutile phase titanium dioxide nanoparticles solution. The refractive index of poloxamer hydrogel can increase from 1.355 to 1.407 according to the concentration of titanium dioxide nanoparticles, and all samples had a good transmission (~90%) comparable to a 5-year-old natural crystalline lens.
Stretch and unstretch experiment shows the PDMS capsule which filled with the highest refractive index poloxamer hydrogel has the largest change of diopter (2.53D), and the lowest refractive index poloxamer hydrogel shows the smallest change (0.87D). The average change ability is 16.57%, better than the human crystalline lens, about 8.37%.
The gradient refractive index structure in the human crystalline lens also reconstruct by using the electric field method. The distribution of titanium dioxide nanoparticles can be controlled by electric field in poloxamer hydrogel, which presents the radial gradient refractive index profiles. Finally we cross-linked poloxamer hydrogel that the gradient refractive index structure can be maintained. The experiment data also show the gradient refractive index does have the ability to increase the image quality. The novel organic/inorganic hybrid materials show the potential to be used for crystalline lens applications.