Loaded HEMA Hydrogels

Hydrogels loaded with methronidasole, an antibiotic specific for periodontal infections, were prepared according to two strategies, that is either by soaking preformed HEMA hydrogels in methronidasole solutions or by direct polymerization ofmonomers/methronidasole mixtures. 

In the first case preformed HEMA hydrogels were soaked in a methronidasole solution in water (10 g/1) or in DMSO (124 g/1). The amount of absorbed drug from the water solution was rather low (5,5 % by weight) while a 48 % drug absorption was obtained from the DMSO solution. However, when the soaked hydrogel was washed with diethyl ether to remove DMSO, most ofthe absorbed drug was removed as well. 

The release of methronidasole from HEMA hydrogels water solution was monitored by measuring the UV absorption at 320 nm (Fig.7 and 8). 

The linear trend of methronidasole release vs. the square root of time (Fig.8) indicates that this process is diffusion controlled according to a Fickian II mechanism. 

The methronidasole diffusion coefficient, Dm 1.0 10 cm -sec , resulted almost independent of polymer structure (Table 6) and somewhat lower than that of water, very likely due to the larger size of the methronidasole molecule. The much larger Dm value of the uncrosslinked sample can be attributed the synergistic effect of its linear structiue and low molecular weight. 

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Controlled release systems can be obtained by loading HEMA hydrogels with an antibiotic dmg, either by soaking preformed polymers in methronidasole solutions or by direct polymerization of monomer/dmg mixtures. Also the release of methronidasole in water obeyed diffusive type kinetics, albeit at a slower rate than water and it was completed within 10 hours. 

Later, they designed imprinted HEMA-based hydrogel CL using acrylic acid (AA) as a functional monomer to load and to release norfloxacin for several hours or even days in a sustained way. However, the duration of drug release in these imprinted hydrogel CLs using one functional monomer was limited to less than 1 day in vitro and in vivo experiments. 

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