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Alex Hui, Andrea K. Weeks, Heather Sheardown, Lyndon W. Jones; Novel Silicone Hydrogel Contact Lens Materials For Ciprofloxacin Drug Delivery. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6531.
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While over 90% of drug delivery to the eye is in the form of eye drops, they are far from an efficient means of drug delivery. This inefficiency has caused researchers to look for alternate drug delivery paradigms such as contact lens delivery devices. The introduction of highly oxygen permeable silicone hydrogels contributed to interest in contact lens applications, as safe overnight wear for extended periods was shown to be a clinical possibility. Unfortunately, commercially available, non-customized materials are unsuitable for drug delivery as they are unable to sustain release over extended time periods, necessitating the creation of novel materials. One such strategy to delay the release of drugs from materials is termed "molecular imprinting", in which "cavities" or "molecular memory" are created within a material by incorporating templates during the polymerization process. The interaction between the cavities and the drug of interest serve to slow drug movement through the material, potentially extending release times substantially.
Poly(2-hydroxyethyl methacrylate) (pHEMA)+tris(trimethylsiloxy) silylpropylmethacrylate (TRIS) and pHEMA+TRIS+Hyaluronic Acid (HA) materials were polymerized in the presence of dissolved Ciprofloxacin-HCl as a template for molecular imprinting. Small discs of the material were punched out, and then rinsed over several days in phosphate buffered saline to remove imprinted ciprofloxacin. Uptake of a 0.3% Ciprofloxacin solution into the discs for one week, and subsequent release into a phosphate buffered saline solution for two weeks was monitored using spectrophotometry at an excitation wavelength of 274 nm and an emission wavelength of 419 nm.
Approximately 0.2 mg and 0.1 mg of ciprofloxacin was released from pHEMA+TRIS and pHEMA+TRIS+HA materials respectively. Unlike previous studies, this release was achieved relatively linearly over the course of at least five hours, and followed by a much slower rate of release for the remaining two weeks.
Molecular imprinting techniques can be used successfully to slow and control the amount of drug released from different materials, and remains an area rife with potential for further investigation for drug delivery materials.
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