Highly biocompatible behaviour and slow degradation of a LDH (layered double hydroxide)-coating on implants in the middle ear of rabbits

Chronic inflammation can irreversibly damage components of the ossicular chain which may lead to sound conduction deafness. The replacement of impaired ossicles with prostheses does not reduce the risk of bacterial infections which may lead to loss of function of the implant and consequently to additional damage of the connected structures such as inner ear, meninges and brain. Therefore, implants that could do both, reconstruct the sound conduction and in addition provide antibacterial protection are of high interest for ear surgery. Layered double hydroxides (LDHs) are promising novel biomaterials that have previously been used as an antibiotic-releasing implant coating to curb bacterial infections in the middle ear. However, animal studies of LDHs are scarce and there exist only few additional data on the biocompatibility and hardly any on the biodegradation of these compounds. In this study, middle ear prostheses were coated with an LDH compound, using suspensions of nanoparticles of an LDH containing Mg and Al as well as carbonate ions. These coatings were characterized and implanted into the middle ear of healthy rabbits for 10 days. Analysis of the explanted prostheses showed only little signs of degradation. A stable health constitution was observed throughout the whole experiment in every animal. The results show that LDH-based implant coatings are biocompatible and dissolve only slowly in the middle ear. They, therefore, appear as promising materials for the construction of controlled drug delivery vehicles.