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Lingyun Cheng, Chengyun Wang, Huiyuan Hou, Kaihui Nan, William R Freeman, Michael J Sailor; Porous Silicon Microparticles Covalently Loaded with Dexamethasone for intravitreal injection. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5260.
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We hypothesize that dexamethasone, a potent steroid frequently used for chorioretinal diseases, could be covalently attached to porous silicon particles and used as a long-lasting intravitreal delivery platform. The current study evaluates the feasibility chemical synthesis and potential application of this platform for treatment of posterior segment of eye diseases.
Porous silicon microparticles were prepared by electrochemical etch of highly doped, (100)-oriented p-type silicon wafers in a 48% aqueous HF:ethanol electrolyte solution. The fresh etched porous silicon was heated at 800C in a furnace chamber for 2 hour in a ceramic boat for complete oxidation (from Si to SiO2). The particles were then functionalized with an amine group and a carboxylic acid group for drug loading (OPS-CO2H). Dexamethasone was covalently loaded to the surface of the porous silicon particles through functional group of COOH.
Dexamethasone loading by covalent attachment was confirmed by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy using a Nicolet 6700 FT-IR spectrometer with Smart-ATR attachment. As determined by thermogravimetric analysis (TGA), the mass loading of dexamethasone by covalent attachment was 134 ± 13 μg per mg of the particles, while only 16 ± 1 μg/mg particles for physical adsorption loading. In an in-vitro release study, porous silicon covalently loaded dexamethasone demonstrated a sustained release course of 90 days (Clast=9ng/mL), but concurrent control of free drug or adsorption loading showed a typical first-order release in a course of 14 days (Clast=9 ng/mL and 5 ng/mL).
Porous silicon particles covalently loaded with dexamethasone may be a promising sustained intravitreal delivery system for dexamethasone and can be implemented for many chorioretinal diseases.
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