Different silicon-based xero-gel molecularly imprinted spheres in the nano boundary range with
recognition capabilities for nafcillin have been synthesised, using tetraethylorthosilicate (TEOS) and (3-
aminopropyl) triethoxysilane (APTEOS) as precursors. Imprinting has been achieved using both nafcillin
(NAF) or structural analogous ‘dummies’ such as (+)-6-aminopenicillenic acid (APA), or ampicillin ((+)-6-
aminobenzylpenicillin)sodium salt (AMP). Materials were fully characterized using ATR-FTIR, 29Si solidstate
NMR, TGA, TEM and BET. Adsorption isotherms for all the materials fit with a continuous Freundlich model with
correlation coefficients better than 0.988 and mean affinity constants between 105 and 106 L·mol-1. The use of ‘dummies’
as well as the template itself in the imprinting process resulted in materials with different release speed. Combinations of
these materials allow designing mixtures with a continuous, controlled and constant release longer than four days. Thus,
the non-imprinted and the AMP-imprinted material have a rapid release during the first five hours, nafcillin and APA imprinted
ones release antibiotic mainly after a latency-period of 24 hours.
Keywords: Adsorption, Drug Delivery, Isotherms, Molecularly imprinted silica, Nafcillin, Nanospheres.
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