Design of medical tympanostomy conduits with selective fluid transport properties

Implantable tubes, shunts, and other medical conduits are crucial for treating a wide range of conditions from ears and eyes to brain and liver but often impose serious risks of device infection, obstruction, migration, unreliable function, and tissue damage. Efforts to alleviate these complications remain at an impasse because of fundamentally conflicting design requirements: Millimeter-scale size is required to minimize invasiveness but exacerbates occlusion and malfunction. Here, we present a rational design strategy that reconciles these trade-offs in an implantable tube that is even smaller than the current standard of care. Using tympanostomy tubes (ear tubes) as an exemplary case, we developed an iterative screening algorithm and show how unique curved lumen geometries of the liquid-infused conduit can be designed to co-optimize drug delivery, effusion drainage, water resistance, and biocontamination/ingrowth prevention in a single subcapillary-length-scale device. Through extensive in vitro studies, we demonstrate that the engineered tubes enabled selective uni- and bidirectional fluid transport; nearly eliminated adhesion and growth of common pathogenic bacteria, blood, and cells; and prevented tissue ingrowth. The engineered tubes also enabled complete eardrum healing and hearing preservation and exhibited more efficient and rapid antibiotic delivery to the middle ear in healthy chinchillas compared with current tympanostomy tubes, without resulting in ototoxicity at up to 24 weeks. The design principle and optimization algorithm presented here may enable tubes to be customized for a wide range of patient needs.

Effect of Growth Factor-Loaded Acellular Dermal Matrix/MSCs on Regeneration of Chronic Tympanic Membrane Perforations in Rats

The success rate of grafting using acellular dermal matrix (ADM) for chronic tympanic membrane was reported in previous studies to be lower than fascia or perichondrium. Combining mesenchymal stem cells (MSCs) and growth factor-loaded ADM for the regeneration of chronic TMP has not been reported so far. In this study, we hypothesized that combining growth factor-loaded ADM/MSCs could promote the recruitment of MSCs and assist in TMP regeneration. We evaluated the regeneration and compared the performance of four scaffolds in both in vitro and in vivo studies. MTT, qPCR, and immunoblotting were performed with MSCs. In vivo study was conducted in 4 groups (control; ADM only, ADM/MSC, ADM/MSC/bFGF, ADM/MSC/EGF) of rats and inferences were made by otoendoscopy and histological changes. Attachment of MSCs on ADM was observed by confocal microscopy. Proliferation rate increased with time in all treated cells. Regeneration-related gene expression in the treated groups was higher. Also, graft success rate was significantly higher in ADM/MSC/EGF group than other groups. Significant relationships were disclosed in neodrum thickness between each group. The results suggest, in future, combining EGF with ADM/MSCs could possibly be used as an outpatient treatment, without the need for surgery for eardrum regeneration.

Ciprofloxacin Decreases Collagen in Mouse Tympanic Membrane Fibroblasts

Objectives

To determine how collagen production by tympanic membrane fibroblasts is affected by ciprofloxacin at levels found in eardrops.

Study Design

Prospective, controlled, and blinded cell culture study.

Setting

Academic tertiary medical center.

Subjects

Cell culture of mouse fibroblasts.

Methods

A primary fibroblast culture was established from mouse tympanic membranes. Fibroblasts were cultured until they were 75% confluent, then treated with dilute hydrochloric acid (control) or ciprofloxacin (0.01% or 0.3%) for 24 or 72 hours for Western blotting and for 24 or 48 hours for cytotoxicity assay. Cells were observed with phase-contrast microscope. Western blotting was performed for collagen type 1 α1 (collagen 1A1) and α-tubulin.

Results

Fibroblasts treated with 0.01% and 0.3% ciprofloxacin for 24 hours had lower levels of collagen 1A1 ( P = .0005 and P < .0001, respectively) and α-tubulin (both P < .0001) than control fibroblasts. Collagen 1A1 and α-tubulin levels were lower in fibroblasts treated with 0.3% than with 0.01% ciprofloxacin ( P = .02 and P = .014). After 72 hours, 0.3% ciprofloxacin completely eliminated collagen 1A1 and α-tubulin ( P < .001). Cells treated with 0.01% ciprofloxacin for 72 hours also had lower collagen 1A1 ( P < .0001) and α-tubulin ( P = .005) as compared with the control. Seventy-two-hour incubation in 0.01% or 0.3% ciprofloxacin resulted in lower levels of collagen 1A1 ( P = .009 and P < .0001, respectively) and α-tubulin ( P = .007 and P < .0001, respectively) than 24-hour incubation. Cytotoxicity assay and phase-contrast microscopy mirrored these findings.

Conclusions

Treatment of tympanic membrane fibroblasts with 0.3% ciprofloxacin, as found in eardrops, reduces fibroblast viability and collagen and α-tubulin protein levels. These findings could explain tympanic membrane healing problems associated with quinolone eardrops.

Spontaneous healing of the tympanic membrane after traumatic perforation in rats

The most common etiologies of tympanic membrane perforation are infections and trauma.

Objective

The objective of the present study was to assess the healing of traumatic tympanic membrane perforation in rats.

Methods

The tympanic membrane from male Wistar rats was perforated in the anterior and posterior portions to the handle of the malleus. Five tympanic membranes were evaluated 3 days after tympanic perforation; 5 after 5 days; 5 after 7 days; 3 after 10 days; and 4 after 14 days. The tympanic membranes were submitted to histopathological evaluation after hematoxylin–eosin staining.

Results

Tympanic membrane closure occurred at about 7–10 days after injury and the healing process was complete by day 14. The proliferative activity of the outer epithelial layer was present close to the handle of the malleus and to the tympanic annulus.

Conclusion

The spontaneous healing process of the tympanic membrane starts from the outer epithelial layer, with later healing of the lamina propria and the mucosal layer.