Crosslinked hydrogels for tympanic membrane repair

A Pseudo-Surfactant Chemical Permeation Enhancer to Treat Otitis Media via Sustained Transtympanic Delivery of Antibiotics

Chemical permeation enhancers (CPEs) represent a prevalent and safe strategy to enable noninvasive drug delivery across skin-like biological barriers such as the tympanic membrane (TM). While most existing CPEs interact strongly with the lipid bilayers in the stratum corneum to create defects as diffusion paths, their interactions with the delivery system, such as polymers forming a hydrogel, can compromise gelation, formulation stability, and drug diffusion. To overcome this challenge, differing interactions between CPEs and the hydrogel system are explored, especially those with sodium dodecyl sulfate (SDS), an ionic surfactant and a common CPE, and those with methyl laurate (ML), a nonionic counterpart with a similar length alkyl chain. Notably, the use of ML effectively decouples permeation enhancement from gelation, enabling sustained delivery across TMs to treat acute otitis media (AOM), which is not possible with the use of SDS. Ciprofloxacin and ML are shown to form a pseudo-surfactant that significantly boosts transtympanic permeation. The middle ear ciprofloxacin concentration is increased by 70-fold in vivo in a chinchilla AOM model, yielding superior efficacy and biocompatibility than the previous highest-performing formulation. Beyond improved efficacy and biocompatibility, this single-CPE formulation significantly accelerates its progression toward clinical deployment.

Collagen Matrix to Restore the Tympanic Membrane: Developing a Novel Platform to Treat Perforations

Modern otology faces challenges in treating tympanic membrane (TM) perforations. Instead of surgical intervention, alternative treatments using biomaterials are emerging. Recently, we developed a robust collagen membrane using semipermeable barrier-assisted electrophoretic deposition (SBA-EPD). In this study, a collagen graft shaped like a sponge through SBA-EPD was used to treat acute and chronic TM perforations in a chinchilla model. A total of 24 ears from 12 adult male chinchillas were used in the study. They were organized into four groups. The first two groups had acute TM perforations and the last two had chronic TM perforations. We used the first and third groups as controls, meaning they did not receive the implant treatment. The second and fourth groups, however, were treated with the collagen graft implant. Otoscopic assessments were conducted on days 14 and 35, with histological evaluations and TM vibrational studies performed on day 35. The groups treated with the collagen graft showed fewer inflammatory changes, improved structural recovery, and nearly normal TM vibrational properties compared to the controls. The porous collagen scaffold successfully enhanced TM regeneration, showing high biocompatibility and biodegradation potential. These findings could pave the way for clinical trials and present a new approach for treating TM perforations.

Hybrid Hydrogel Composed of Hyaluronic Acid, Gelatin, and Extracellular Cartilage Matrix for Perforated TM Repair

A novel series of composite hydrogels, built from the three components 1), hyaluronic acid methacryloyl (HAMA); 2), gelatin methacryloyl (GelMA), and 3), extracellular cartilage matrix (ECM), was prepared and studied regarding the possible utility in the surgical repair of damaged (perforated) tympanic membrane (TM). Noteworthy is component 3), which was harvested from the ribs of α-1,3-galactosidyltransferase-knockout (α-1,3 GalT-KO) pigs. The absence of α-1,3-galactosyl glycoprotein is hypothesized to prevent rejection due to foreign-body immunogenicity. The composite hydrogels were characterized by various aspects, using a variety of physicochemical techniques: aqueous swelling, structural degradation, behavior under compression, and morphology, e.g., in vitro biocompatibility was assessed by the CCK-8 and live–dead assays and through cytoskeleton staining/microscopy. Alcian blue staining and real-time PCR (RT-PCR) were performed to examine the chondrogenic induction potential of the hydrogels. Moreover, a rat TM defect model was used to evaluate the in vivo performance of the hydrogels in this particular application. Taken together, the results from this study are surprising and promising. Much further development work will be required to make the material ready for surgical use.

Comparison of hearing outcomes in stapedotomy with fat and Hyaluronic acid gel as a sealing material: a prospective double-blind randomized clinical trial

PURPOSE

In the literature on stapes surgery, various materials have been used to seal the vestibulotomy. To date, there are only a few published randomized clinical trials with focus on hearing outcomes, using different sealing materials. Hence, the aim of this study was to compare hearing outcomes when using fat or Hyaluronic acid gel (HAG) to seal the stapedotomy.

METHODS

The present double-blind, prospective, randomized clinical trial was conducted on ears undergoing stapedotomy in Dasthgheib Hospital, a referral otology center in Southern Iran, and Dena private hospital, Shiraz Iran. A total of 150 primary stapedotomies were evaluated, and sealing material was fat in 77 ears and HAG in 73.

RESULTS

60 (77.9%) of the fat group ears and 63 (86.3%) of the HAG group ears obtained postoperative air-bone gap (ABG) within 20 dB, but the difference was not significant (p = 0.182).

CONCLUSION

As a sealing material in stapedotomy, HAG is comparable with fat in terms of hearing outcomes. Therefore, HAG is recommended as a safe sealing material in stapedotomy.

Evaluating short and long term outcomes following pediatric Myringoplasty with Gelfoam graft for tympanic membrane perforation following ventilation tube insertion

Background

Myringotomy with ventilation tube (VT) insertion to treat recurrent acute otitis media and chronic secretory otitis media has become one of the most common surgical procedures performed in children. Although contemporary literature has detailed the various patient and perioperative factors that affect successful pediatric myringoplasty, there is still limited evidence surrounding the increasing number of graft material options. In particular, gelfoam patching has arisen as a simple and efficient modality for perforation closure, but has a paucity of evidence particularly in pediatric cohorts. Our study aims to evaluate the clinical and audiometric outcomes following gelfoam myringoplasty for TMP following prolonged VT insertion in an urban pediatric population.

Methods

A retrospective review of pediatric patients who underwent myringoplasty between 2013 and 2018 following ventilation tube insertion. Patient demographics, comorbidities, and graft material were correlated with audiometric and clinical outcomes on follow up examination.

Results

One hundred twenty patients underwent myringoplasty, with 61 (50.8%) males with a mean age of 8.9 years old. 101 (84.2%) of patients eventually underwent successful tympanic membrane (TM) closure, with 93 (77.5%) demonstrating closure at initial follow up. In the gelfoam cohort, 77 (90.6%) of patients demonstrated successful TM closure at initial follow up. Overall mean time to closure was 5.6 (standard error (SE) 0.9) months. A multivariate Cox proportional hazards model demonstrated none of the covariates including graft material significantly affected TM closure. Mean change in air conduction threshold were comparable between graft materials.

Conclusions

Pediatric myringoplasty with gelfoam graft material is a safe and viable alternative with favorable short and long term clinical and audiometric outcomes.

Histological Study of The Healing of Traumatic Tympanic Membrane Perforation After Vivosorb and Epifilm Application

BACKGROUND

Untreated traumatic tympanic membrane perforations (TMPs) may lead to permanent perforations and hearing loss. There are many materials that have been previously used for repairing the TMPs.

AIMS AND OBJECTIVES

The purpose of this study is to evaluate the clinical and histological effects of Vivosorb (Vv) and Epifilm on healing of TMPs in a rat model.

MATERIAL AND METHODS

The posterior-inferior quadrant of the tympanic membranes (TMs) in right ears of 14 rats was perforated using a 20-g needle and then the animals were randomly divided into 2 equal groups (n = 7). The perforated right TMs were treated with either Vv (Vv group) or Epifilm (Ep group). The left TMs of 7 rats were perforated in same way and allowed to close spontaneously without any topical material applications (spontaneous closure group as sham control, SC). The left tympanic membranes of the other 7 rats were not perforated and used as normal controls (NC group). On postoperative 15th day, tympanic bullas were extracted from killed rats and examined morphometrically and histopathologically.

RESULTS

Perforation closure rate was 85.7% (6/7) in both Vv and SC groups. Perforations of Ep group closed in 7/7 (100%) ears. The thicknesses of the perforated membranes were increased in SC and especially Vv groups. Also, connective tissue fibrosis, blood clots, and epithelial degenerations were detected in SC and Vv groups. The mean fibroblastic reaction scores of Vv, Ep, and SC groups were 2.14(+), 0.57(+), and 1.71(+) respectively, on comparison with NC group. The mean neovascularization score was 1.42(+) in Vv group, 0.14(+) in Ep group, and 0.57(+) in SC group.

CONCLUSION AND SIGNIFICANCE

Vivosorb and especially Epifilm can improve the healing process in traumatic TMPs and additionally, Epifilm might be more preferred for the treatment of TMPs because of causing lesser fibrosis.

Outlook for Tissue Engineering of the Tympanic Membrane

Tympanic membrane perforation is a common problem leading to hearing loss. Despite the autoregenerative activity of the eardrum, chronic perforations require surgery using different materials, from autologous tissue - fascia, cartilage, fat or perichondrium - to paper patch. However, both, surgical procedures (myringoplasty or tympanoplasty) and the materials employed, have a number of limitations. Therefore, the advances in this field are incorporating the principles of tissue engineering, which includes the use of scaffolds, biomolecules and cells. This discipline allows the development of new biocompatible materials that reproduce the structure and mechanical properties of the native tympanic membrane, while it seeks to implement new therapeutic approaches that can be performed in an outpatient setting. Moreover, the creation of an artificial tympanic membrane commercially available would reduce the duration of the surgery and costs. The present review analyzes the current treatment of tympanic perforations and examines the techniques of tissue engineering, either to develop bioartificial constructs, or for tympanic regeneration by using different scaffold materials, bioactive molecules and cells. Finally, it considers the aspects regarding the design of scaffolds, release of biomolecules and use of cells that must be taken into account in the tissue engineering of the eardrum. The possibility of developing new biomaterials, as well as constructs commercially available, makes tissue engineering a discipline with great potential, capable of overcoming the drawbacks of current surgical procedures.

Cross-linked hydrogel and polyester resorbable ventilation tubes in a Chinchilla model

OBJECTIVES/HYPOTHESIS

To determine the resorption rate and biocompatibility characteristics of novel cross-linked hydrogel ventilation tubes and varied formulations of polyester ventilation tubes in a Chinchilla model.

STUDY DESIGN

Animal Study.

METHODS

Three cross-linked glycosaminoglycan hydrogel ventilation tubes fabricated by cross-linking thiol-modified chondroitin sulfate or thiol-modified carboxymethylated hyaluronic acid, four different polyester ventilation tubes (poly L-lactide [PLA], 50/50 poly D,L-lactide-co-glycolide [PLGA], and silver-impregnated versions of PLA and PLGA tubes) were placed into the tympanic membranes of chinchillas. Commercially available fluoroplastic ventilation tubes were placed in the contralateral ear of each animal to serve as a control. Integrity of the tubes was assessed by weekly otoscopy. Biocompatibility was assessed by auditory brainstem response, by otoscopic and histologic examination of the tympanic membrane at the tube site.

RESULTS

The hydrogel tubes had very short resorption times that expanded and enlarged the myringotomy site. PLGA and silver-coated PLGA tubes maintained their integrity in the tympanic membrane for similar durations of 18.9 ± 6.4 days and 21.0 ± 6.0 days, respectively. The silver-coated PLGA tubes had lower neutrophil and fibrosis scores than PLGA tubes. PLA tubes demonstrated equivalent findings to commercially available nonresorbable tubes with respect to otoscopic findings, auditory brainstem response thresholds, and histologic inflammatory scores.

CONCLUSIONS

Resorbable polyester pressure equalization tubes demonstrate predictable resorption behavior and similar biocompatibility characteristics when compared with nonresorbable tubes. Silver modification may confer some stability to PLGA tubes. Hydrogel tubes have very short resorption times, tend to enlarge the myringotomy site, and show greater inflammatory changes.

Repair of tympanic membrane perforation using novel adjuvant therapies: a contemporary review of experimental and tissue engineering studies

OBJECTIVE

To perform a contemporary review of experimental studies to describe the effects of various novel adjuvant therapies in enhancing tympanic membrane (TM) perforation healing.

METHODS

A PubMed search for articles from January 2000 to June 2012 related to TM perforation, along with the references of those articles, was performed. Inclusion and exclusion criteria were applied to all experimental studies assessing adjuvant therapies to TM healing.

RESULTS

Many studies have assessed the efficacy of biomolecules or growth factors, such as epidermal growth factors and basic fibroblast growth factors, in TM regeneration with significant success. More recent strategies in TM tissue engineering have involved utilizing bioengineered scaffold materials, such as silk fibroin, chitosan, calcium alginate, and decellularized extracellular matrices. Most scaffold materials demonstrated biocompatibility and faster TM perforation healing rates.

CONCLUSION

Although several studies have demonstrated promising results, many questions still remain, such as the adequacy of animal models and long-term biocompatibility of adjuvant materials. As well, further studies comparing various adjuvant substances and bioscaffolds are required prior to clinical application.

Tissue engineering of the tympanic membrane

Tympanic membrane (TM) perforations are common, with current treatments for chronic perforations involving surgery, using various graft materials, from autologous cartilage or fascia through to paper patch. Recent research developments in this field have begun applying the principles of tissue engineering, with appropriate scaffolds, cells, and bioactive molecules (BMs). This has revolutionized the therapeutic approach due to the availability of a wide range of materials with appropriate compatibility and mechanical properties to regenerate the membrane acoustics and may also represent a paradigm shift in the management of TM perforations in an outpatient setting without surgery. However, many factors need to be considered in the fabrication of a bioengineered TM. This review discusses the issues associated with current treatment and examines TM wound healing relevant to the construction of a bioengineered TM. It also describes the tissue-engineering approach to TM regeneration by summarizing currently used scaffolds, BMs, and cells in TM wound healing. Finally, it considers the design of scaffolds, delivery of BMs, and cell engraftment toward potential clinical application.

A randomised controlled trial comparing spontaneous healing, gelfoam patching and edge-approximation plus gelfoam patching in traumatic tympanic membrane perforation with inverted or everted edges

OBJECTIVE

To compare the outcome of patients with dry traumatic tympanic membrane perforation after spontaneous healing and gelfoam patching with or without perforation edge approximation.

DESIGN

Prospective clinical study.

SETTING

University-affiliated teaching hospital.

PARTICIPANTS

Ninety-one patients with acute dry traumatic tympanic membrane perforation inverted or everted edges were recruited. They were randomly allocated to three groups: spontaneous healing (n=31), gelfoam patching (n=30) and edge-approximation plus gelfoam patching (n=30). Otoscopy and tympanometry were performed before the treatment and at follow-up visits.

MAIN OUTCOME MEASURES

  Healing rate, healing time, ear infection rate and morphological changes during healing process.

RESULTS

The overall healing rate was 85% in the spontaneous healing group, lower than that in the two gelfoam patching groups (97%), but the difference failed to reach a statistical significance (P>0.05). The average healing time was 30 ± 10.1 days in the spontaneous healing group, significantly longer (P<0.01) than that in the other two groups (16 ± 5.6 and 18 ± 4.7 days, respectively). Middle ear infection rate did not differ significantly (7%, 3% and 3%, respectively). Spontaneous healing resulted in formation of scabs at the perforation edges, which was effectively prevented by gelfoam patching.

CONCLUSIONS

Gelfoam patching may facilitate healing of traumatically perforated tympanic membrane. Approximation of folded perforation edges is not necessary in gelfoam patching.

Development of water-insoluble chitosan patch scaffold to repair traumatic tympanic membrane perforations

Perforated tympanic membranes (TM) and otitis media can be managed with a paper patch or tympanoplasty. However, a paper patch is not biocompatible and tympanoplasty requires complex aseptic surgical procedures. A novel biocompatible patch with a water-insoluble chitosan as the main component was prepared. Optimal mechanical characteristics of a water-insoluble chitosan patch scaffold (CPS) was approximately 40 microm in thickness, 7 MPa in tensile strength, and 107% in percent elongation, even though the characteristics varied significantly depending on the concentrations of chitosan and glycerol. SEM of the CPSs showed a very smooth surface as compared with that of the paper patches. These CPSs showed no cytotoxicity and had a stimulating effect on the proliferation of TM cells in in vitro study. In in vivo study, 4 (21.1%) and 17 (89.5%) TMs out of 19 adult rats with CPSs showed no perforations at 1 and 2 weeks, respectively. However, left control TMs showed healing of 0 (0%) at 1 week and 18 (94.7%) at 2 weeks. TEM findings of regenerated eardrums using CPSs showed thinner, smoother, and more compact tissues than spontaneously healed eardrums. A CPS was more effective than spontaneous healing to repair traumatic TM perforations.

Modular extracellular matrices: solutions for the puzzle

The common technique of growing cells in two-dimensions (2-D) is gradually being replaced by culturing cells on matrices with more appropriate composition and stiffness, or by encapsulation of cells in three-dimensions (3-D). The universal acceptance of the new 3-D paradigm has been constrained by the absence of a commercially available, biocompatible material that offers ease of use, experimental flexibility, and a seamless transition from in vitro to in vivo applications. The challenge-the puzzle that needs a solution-is to replicate the complexity of the native extracellular matrix (ECM) environment with the minimum number of components necessary to allow cells to rebuild and replicate a given tissue. For use in drug discovery, toxicology, cell banking, and ultimately in reparative medicine, the ideal matrix would therefore need to be highly reproducible, manufacturable, approvable, and affordable. Herein we describe the development of a set of modular components that can be assembled into biomimetic materials that meet these requirements. These semi-synthetic ECMs, or sECMs, are based on hyaluronan derivatives that form covalently crosslinked, biodegradable hydrogels suitable for 3-D culture of primary and stem cells in vitro, and for tissue formation in vivo. The sECMs can be engineered to provide appropriate biological cues needed to recapitulate the complexity of a given ECM environment. Specific applications for different sECM compositions include stem cell expansion with control of differentiation, scar-free wound healing, growth factor delivery, cell delivery for osteochondral defect and liver repair, and development of vascularized tumor xenografts for personalized chemotherapy.

Bioreactor-free tissue engineering: directed tissue assembly by centrifugal casting

Casting is a process by which a material is introduced into a mold while it is liquid, allowed to solidify in a predefined shape inside the mold, and then removed to give a fabricated object, part or casing. Centrifugal casting could be defined as a process of molding using centrifugal forces. Although the centrifugal casting technology has a long history in metal manufacturing and in the plastics industry, only recently has this technology attracted the attention of tissue engineers. Initially, centrifugation was used to optimize cell seeding on a solid scaffold. More recently, centrifugal casting has been used to create tubular scaffolds and both tubular and flat multilayered, living tissue constructs. These newer applications were enabled by a new class of biocompatible in situ crosslinkable hydrogels that mimic the extracellular matrix. Herein the authors summarize the state of the art of centrifugal casting technology in tissue engineering, they outline associated technological challenges, and they discuss the potential future for clinical applications.

Healing time, long-term result and effects of stem cell treatment in acute tympanic membrane perforation

OBJECTIVE

The incidence of otitis media in children between the age of 2 and 6 years is well documented. Repeated attacks may cause acute and chronic perforations. The surgical treatment for repairing chronic perforation is quite uncomfortable for the patients of this age group because of the invasiveness of this treatment. The aim of this study was to determine the long-term influence of embryonic stem cells on acute perforations and the effect of gelatin as a vehicle for applied stem cells. The possibility of teratogenic effects of the stem cells was also observed.

METHODS

Bilateral laser myringotomy was performed in 17 adult Sprague-Dawley rats, divided into two groups. Gelatin, a substance suitable as vehicle for bioactive material was used bilaterally around the perforation in group A, to serve as a scaffold for repairing tissue. The stem cells were used in the right tympanic membrane perforation leaving the left tympanic membrane as a control. The animals in group B received the same treatment except for the use of gelatin and in addition received an immuno-suppressive agent. After half a year of observation the mechanical stiffness of the tympanic membrane was measured by moiré interferometry for group B and the morphological study was performed by light microscopy for both groups A and B and electron microscopy for group A.

RESULTS

Stem cell treated ears did not show any enhanced healing of the perforation although a marked thickening of the lamina propria was observed compared with control group. After half a year the strength and the stiffness of the tympanic membrane was almost the same for both treated and untreated ears. No evidence of teratoma was found after half a year.

CONCLUSION

This study suggests that the stem cells stimulate the proliferation of connective tissue and fibers in the lamina propria, possibly mediated by secreted substances, although the stiffness properties do not seem to be altered. The use of gelatin does not seem to enhance the healing process of the tympanic membrane perforation.