PROJECT SUMMARY
Although tympanostomy tube (TT or ear tube) placement is a simple and common surgery (754,000/year in the
US), complications arise in a subset of patients, particularly post-TT otorrhea (PTTO, 26%) due to bacterial
biofilms and mucus plugging (7-34%). There is an urgent need to reduce these complications and enhance the
functional longevity of TTs. Modification of TT surfaces to prevent bacterial adhesion and to reduce mucus
adhesion could dramatically reduce these complications. We recently developed a novel photochemically
driven process that simultaneously forms and grafts zwitterionic thin films onto polymeric materials used to
fabricate TTs (e.g. PDMS). These thin films are polymerized from either sulfobetaine methacrylate (SBMA) or
carboxybetaine methacrylate (CBMA) monomers. The CBMA/SBMA polymer chains are crosslinked to each
other during polymerization by polyethylene glycol dimethacrylate (PEGDMA). We find that both CBMA and
SBMA thin films prevent adhesion by an order of magnitude from fibrinogen, platelets, macrophages,
fibroblasts, and importantly, Staphylococcus aureus and Staphylococcus epidermidis. We propose to extend
these promising findings into TTs, while determining how changes in crosslinking density affect end properties.
The overall objective of this research is to determine the ability of zwitterionic thin films grafted onto the surface
of TTs to prevent the complex phenomena of bacterial colonization and mucus plugging. We hypothesize that
CBMA and SBMA zwitterionic thin films will prevent bacterial adhesion and reduce mucus plugging on TTs. We
will test this hypothesis by undertaking the following Specific Aims.
1) Determine the effect of CBMA and SBMA thin films on bacteria adhesion from Staphylococcus aureus and
Pseudomonas aeruginosa on TTs. We will test this effect by quantifying bacterial adhesion on PDMS surfaces
using validated in vitro models. We will also expose rats that have been implanted with zwitterionic coated or
bare TTs with either S. aureus or P aeruginosa to induce biofilm formation.
2) Investigate the ability of CBMA and SBMA thin films to reduce mucus adhesion, mucus drying, and mucus
plug formation on TT surfaces. To test this, we will first examine the adhesion and drying of porcine intestinal
mucus on PDMS that have been coated with thin films or remain uncoated. Finally, we will test the mucus
plugging on coated and uncoated TTs inserted into rat tympanic membranes.
When successful, these aims will implicate a novel and highly effective method to prevent common
complications of TTs by preventing biofilm and mucus plug formation. Beyond TTs, the results will be broadly
applicable to devices which suffer from biofouling. This innovation will reduce the PTTO complications currently
suffered by ~50,000 US children per year and thus support the Mission, Goals, and Objectives of the NIDCD.