Autoclavable highly cross-linked polyurethane networks in ophthalmology

Area of Science:

• Materials Science
• Polymer Chemistry
• Biomedical Engineering

Background:

• Aliphatic polyurethanes are versatile polymers with tunable properties.
• Ophthalmic applications require biocompatible, transparent, and sterilizable materials.
• Existing materials may have limitations in terms of optical clarity, mechanical strength, or biocompatibility.

Purpose of the Study:

• To synthesize and characterize highly cross-linked aliphatic polyurethane networks for ophthalmic applications.
• To evaluate the optical, mechanical, and thermal properties of these polyurethanes.
• To assess the biocompatibility and in vivo performance of the polyurethanes in rabbit eyes.

Main Methods:

• Bulk step polymerization of low molecular weight polyols (TIPA, Quadrol) with hexamethylenediisocyanate (HDI).
• Characterization using FTIR spectroscopy, glass transition temperature (Tg) measurements, and mechanical testing (tensile strength, elongation, modulus).
• In vivo implantation in rabbit eyes as disks and keratoprostheses, followed by 1-year observation.

Main Results:

• Optically transparent, colorless, autoclavable glassy thermosets were successfully prepared.
• Quadrol/HDI-based polyurethane showed a Tg reduction with water uptake and good mechanical properties (80-85 MPa tensile strength, 15% elongation, 1.5 GPa modulus).
• Polyurethanes exhibited no UV transmission up to 400 nm, were biocompatible, and well-tolerated in rabbit eyes without opacification for up to 1 year.

Conclusions:

• Highly cross-linked aliphatic polyurethanes are suitable for ophthalmic applications like intraocular lenses and keratoprostheses.
• The material demonstrates excellent optical clarity, mechanical integrity, UV blocking, and biocompatibility.
• Successful in vivo performance in rabbit eyes indicates potential for clinical translation in artificial cornea applications.