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J. Zhang, M. A. Reilly, N. Ravi; Designing Lens Refill Materials With Mechanical Property Gradients. Invest. Ophthalmol. Vis. Sci. 2009;50(13):6138.
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Recent experiments have indicated that refilling the lens with a homogeneous polymer may not restore a useful level of accommodation. Materials with elasticity gradients may be required to restore accommodation in lens refilling.The purpose of this work is to develop potential lens refill hydrogels with mechanical property gradients similar to those found in the natural lens.
Solutions of low acyl gellan (Kelcogel CG-LA; CP Kelco, Chicago, IL) concentrations ranging from 0.25-0.70 wt% were pipetted into a cylindrical diffusion chamber. Various concentrations (0.05-0.10 wt%) of calcium chloride solutions were pumped from a large reservoir across dialysis tubing (MWCO 3500 Da) membrane placed at one end of the chamber so that ions diffused into the gellan solution inducing physical gelation. The cylindrical gel made in this way was sliced perpendicular to its top surface, keeping the center piece for measurement. The gel containing the sample was positioned beneath a microindenter on an aluminum plate. Local elastic moduli along the cylindrical axis were measured.
The hydrogels prepared in the experiments showed repeatable and predictable mechanical property gradients (Fig. 1). The elastic modulus gradient was dependent on the concentrations of both gellan solution and calcium chloride.
Hydrogel networks that exhibit an elasticity gradient similar to that of the natural lens have been developed successfully and synthesized repeatably.
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