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Satyanarayana Somavarapu, Zeeneh Elsaid, Mirza Gunic, Naba Elsaid, Timothy L. Jackson; Amphiphilic Chitosan Nanomicelles For The Topical Delivery Of Rapamycin. Invest. Ophthalmol. Vis. Sci. 2012;53(14):315.
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The purpose of this study was to synthesize and characterise a positively charged amphiphlic polymer and to use this for the preparation of nanomicelles for the ocular delivery of rapamycin.
A chemically modified chitosan derivative; octanoyl-g-chitosan-g-PEG was synthesized, purified via dialysis and then lyophilized to produce the final product which was characterised using FT-IR and 1HNMR. This polymer was used to prepare rapamycin-loaded nanomicelles using the thin film method. Nanomicelles were analysed for size and charge (Dynamic Light Scattering- DLS), surface morphology (Transmission Electron Microscopy- TEM) and thermal properties (Differential Scanning calorimetry- DSC). Scleral permeation and retention was analysed by mounting porcine sclera in Ussing chambers and measuring the drug content using High Performance Liquid Chromatography. The limit of quantification (LOQ) for this was 12.5 ng/mL.
The successful synthesis of this amphiphilic chitosan derivative was confirmed using 1HNMR and FT-IR. This polymer can self-assemble into monodisperse nanomicelles in an aqueous environment to encapsulate the hydrophobic drug, rapamycin. The nanomicelles had an average size of 52 nm and were positively charged. The formulation remained stable for up to 3 days. Upon visible inspection, the formulation appeared clear with a low polydispersity index of 0.25. Permeation studies showed tissue retention within 24 hours of exposure.
The synthesis of chemically modified mucoadhesive nanomicelles of small size and positive charge was successfully achieved. These rapamycin-loaded micelles were retained in the porcine sclera and may be considered for future application in the ocular delivery of other hydrophobic and hydrophilic drugs.
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