Molecular imprinting extends drug release in contacts, modestly affects lens properties

ORLANDO, Fla. – Unmodified contact lenses have been shown to release ciprofloxacin in about an hour; however, the use of a molecular imprinting strategy extends that to 24 hours, according to a researcher who presented his poster here at the Association for Research in Vision and Ophthalmology.

Alex Hui, OD, told Primary Care Optometry News, “If we imprint the lenses, we’re looking at 24 hours or a couple of days, depending on the modification.

“In addition, if we’re going to be pushing contact lenses as drug delivery devices, not only do we have to have good pharmaceutical delivery or good pharmacokinetics, we also need some good contact lens properties,” he continued.

Hui told PCON that the point of this study was to see if the modifications of molecular imprinting changed any of the lens qualities, such as wet weight, dry weight and center thickness.

“None of those are appreciably different for the lenses we’ve created – modified or unmodified,” Hui said.

However, the ciprofloxacin seemed to make the contact angle a bit more wettable.

“I haven’t been able to come up with a reason for why that happens, but the trend seems to be going in that vein,” he said.

“The biggest take-home from this was when we looked at the light transmission of the contact lenses,” Hui said.

Ciprofloxacin is white when it is a powder, but once it is dissolved in solution, the solution turns yellow, he said.

“So, the more that we incorporated the ciprofloxacin into the lenses, the more yellowish tinge we got,” Hui said. “When we look at the light transmission, we get a little bit more absorbance in the blue light type of spectrum. That’s something to consider if we’re ever going to use this in people – you would have to warn them of that. The lenses are yellow and your vision is going to be tinted yellow.”

Hui noted that the use of such lenses would most likely last only a few days, and that the yellowing effect would be purely cosmetic.

“But the key thing is that it’s the property of the drug itself; it’s not about the lens,” he said. “The only way to move away from that would be to choose a different drug that does not tinge things yellow. The majority of the fluoroquinolones within solution tend to be slightly yellowish, so it would have to involve moving into a different class of antibiotics.”

Hui said his group has done some in vivo work involving microbial keratitis.

“Hopefully we’ll have it published soon,” he told PCON. “We have some great results coming out of that.

“So, the real question would be whether or not this would be accepted by practitioners for human patients,” he continued.

Hui said eye care practitioners are trained to think that patients with microbial keratitis should not be wearing contact lenses.

“So, do I have data that is convincing enough to show that it can be beneficial?” he said. “Can I overcome the practitioner and patient nonacceptance with good data to show that it really is superior, or at least noninferior to traditional treatments such as eye drops?”

Hui added that work in this area has moved along quickly, and researchers are learning for which conditions this technique would be more successful. –Nancy Hemphill, ELS

Disclosure: Hui is supported by the Natural Sciences and Engineering Research Council (NSERC), Canada, the Canadian Optometric Education Trust Fund, and an Ezell Fellowship and Vistakon Research Grant, both administered by the American Optometric Foundation. This study is also supported by the NSERC 20/20 Network for the Development of Advanced Ophthalmic Materials.