Background: The pars tensa of the human tympanic membrane (TM) is composed of highly organized fibers, i.e., radial and circular fibers, which are responsible for the vibroacoustic properties of the TM[1]. Locally, the radial and circular fibers are orthogonal to each other. The average fiber diameter is approximately 60 nm. It has been shown that the radial fibers are crucial for hearing at frequencies above 4 kHz[2]. However, all current grafts used in myringoplasty lack the fiber organization of the native TM. The hearing outcomes for patients with TM perforation after surgical treatments could therefore be suboptimal. As a versatile fiber fabrication technique, electrospinning is able to produce fibers with diameters in the nanometer range and fiber alignment can also be achieved[3]. It is therefore possible to fabricate scaffolds with organized fibers to mimic the local structure of the human TM. With scaffolds mimicking the microstructure of the native TM, acoustic properties similar to the TM may be achieved.
Materials and Methods: Polyvinyl alcohol (PVA) was used to demonstrate the capability of making a biomimetic scaffold for TM repair. Both scaffolds with random and organized fibers were prepared using electrospinning. The scaffold with organized fibers consists of two layers of orthogonally oriented fibers. The fiber morphology and alignment was observed using scanning electron microscopy (SEM). The vibroacoustic response of the scaffolds were measured using scanning laser Doppler vibrometry for frequencies from 50 Hz to 10 kHz with an increment of 50 Hz at each measurement.
Results: SEM images show that scaffolds with random and organized PVA fibers were successfully fabricated using electrospinning. The measured vibrations of scaffolds with random and organized fibers showed frequency dependent variations in motion patterns. The motion patterns were similar at frequencies below 1 kHz but differed at frequencies above 1 kHz. It was found that vibration patterns of scaffolds with organized fibers can be tuned to mimic that of the human TM by adjusting fiber diameter and stiffness.
Discussion: The fine fiber organization in the TM is essential for the quality of normal hearing. To improve hearing outcomes after myringoplasty, biomimetic grafts with microstructure similar to that of the native TM should be considered. In this study, it was shown that scaffolds that mimic the local structure of the human TM can be fabricated by electrospinning. The acoustic properties of these scaffolds can be tuned by adjusting the materials and experimental parameters.
Conclusions: In order to match the fiber dimension and organization in the extracellular matrix, electrospinning is a promising technique for fabrication of scaffolds for tissue regeneration applications. Our preliminary study has demonstrated the viability of a biomimetic scaffold for TM repair using electrospinning.
This work was supported by a grant from the Ontario Research Fund – Research Excellence program and Axcelon Biopolymers Corp. J.L. is a recipient of a Mitacs Elevate Fellowship
References:
[1] Funnell WR, Laszlo CA, A critical review of experimental observations on ear-drum structure and function, ORL J. Otorhinolaryngol. Relat. Spec. 44 (1982) 181–205.
[2] Connor KNO, Tam M, Blevins NH, Puria S, Tympanic membrane collagen fibers: a key to high-frequency sound conduction, Laryngoscope 118 (2008) 483–490.
[3] Agarwal S, Wendorff JH, Greiner A, Use of electrospinning technique for biomedical applications, Polymer 49 (2008) 5603–5621.