Biocompatibility of “On-command” dissolvable tympanostomy tube in the rat model

Abstract

Objectives/Hypothesis A prototype tympanostomy tube, composed of (polybutyl/methyl methacrylate-co-dimethyl amino ethyl methacrylate (PBM)), was tested to (1) evaluate the effect of PBM tubes on rat dermis as a corollary for biocompatibility and (2) to observe the efficacy of dissolution with isopropyl alcohol (iPrOH) and ethanol (EtOH). Subjects and Methods A two-part study was conducted to assess biocompatible substance with inducible dissolvability as a critical characteristic for a newly engineered tympanostomy tube. First, tympanostomy tubes were inserted subcutaneously in 10 rats, which served as an animal model for biosafety and compared to traditional tubes with respect to histologic reaction. Tissue surrounding the PBM prototype tubes was submitted for histopathology and demonstrated no tissue reactivity or signs of major inflammation. In the second part, we evaluated the dissolvability of the tube with either isopropyl alcohol, ethanol, ofloxacin, ciprodex, water, and soapy water. PBM tubes were exposed to decreasing concentrations of iPrOH and EtOH with interval qualitative assessment of dissolution. Results (1) Histologic examination did not reveal pathology with PBM tubes; (2) Concentrations of at least 50% iPrOH and EtOH dissolve PBM tubes within 48 hours while concentrations of at least 75% iPrOH and EtOH were required for dissolution when exposure was limited to four 20-minute intervals. Conclusion PBM is biocompatible in the rat model. Additionally, PBM demonstrates rapid dissolution upon alcohol-based stimuli, validating the proof-of-concept of dissolvable “on-command” or biocommandible ear tubes. Further testing of PBM is needed with a less ototoxic dissolver and in a better simulated middle ear environment, before testing can be performed in humans.

An Overview of the Tympanostomy Tube

“…The most prevalent materials used to make tympanostomy tubes are plastics and metals [ 11 ]. The material should be compatible with the middle ear to work as a tympanostomy tube, as the tube will induce the host patient to have a foreign body reaction [ 12 ]. Using a material with a lesser inflammatory response in tube manufacturing increases biocompatibility and thus will be preferred.…”

Tympanostomy Tube Innovation: Advances in Device Material, Design, and Office-Based Technology

“…8 Biocompatibility in the rat model demonstrated no pathologic or reactive tissue surrounding tube placement. 8,9 The tube material showed resistance to degradation with application of Ciprofloxacin and Ciprodex drops, while both ethanol and hydrogen peroxide successfully degraded the tubes over a period of 48 hours. Given potential ototoxicity associated with ethanol use, further efforts to achieve the ideal degradation agent are ongoing.…”