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M. P. Schittkowski, R. Wacke, B. Drewelow, R. F. Guthoff; Osmotic Hydrogel Expanders as Drug Delivery System for Antibiotics. Invest. Ophthalmol. Vis. Sci. 2009;50(13):6003.
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High-hydrophilic osmotic self-inflating hydrogel expanders (osmed GmbH Ilmenau, Germany) are well-accepted for implantation to achieve tissue expansion in defined parts of the body like skin, breast and orbital soft tissue. The suitability of this hydrogel consisting of a co-polymer of N-vinyl-pyrolidone and methyl-methacrylate as a drug delivery system for antibiotics was investigated in a laboratory setting.
The dry expanders were incubated in a 0.3% solution of Ofloxacin or Tobramycin for 24 hours. The complete swollen expander had increased in volume from 0.3ml to almost 3ml (adsorbing 2.7 ml of the 0.3% solution, i.e. 8.1 mg Ofloxacin or Tobramycin, respectively). Addressing the elimination of both antibiotics, the concentrations in 15 ml elution medium (simulating the volume of the orbit in a newborn) were measured after 0.25, 1, 2, 6, 24, 48 and 72 hours of eluation. 0.9% sodium chloride (B.Braun Melsungen, Germany) was used as elution medium. To imitate fluid exchange due to blood perfusion in the surrounding tissue the medium was renewed after every sampling. For each substance 10 expanders were tested. Concentrations of antibiotic were determined by HPLC/UV for Ofloxacin and by using a specific Fluorescence-polarisation immunoassay (Abbott TDx) for Tobramycin.
Mean concentration of Ofloxacin 0.25, 1, 2, 6, 24, 48 and 72 hours after beginning of elution were 50.2, 46.8, 41.2, 75.4, 88.2, 46.2 and 19.1 µg/ml, respectively. The cumulative amount of Ofloxacin eluted after 72 hours reached 68% of loading dose. Corresponding mean concentration of Tobramycin were 38.8, 48.5, 40.5, 69.8, 88.7, 119.3 and 71.6 µg/ml. The cumulative eluted amount was 88%.
The investigated hydrogel expanders soaked in 0.3% antibiotic solution can store and further on release sufficient amounts of Ofloxacin or Tobramycin to produce antimicrobial effective concentrations in-vitro in the surrounding environment. This principle, when used in a clinical setting, might help to eliminate post-implantation infection which is one of the major complications in clinical use.
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