Polymeric middle ear prosthesis enriched with silver nanoparticles – first clinical results

Nanomaterials for Inner Ear Diseases: Challenges, Limitations and Opportunities

The inner ear is located deep in the temporal bone and has a complex anatomy. It is difficult to observe and obtain pathological tissues directly. Therefore, the diagnosis and treatment of inner ear diseases have always been a major clinical problem. The onset of inner ear disease can be accompanied by symptoms such as hearing loss, dizziness and tinnitus, which seriously affect people's lives. Nanoparticles have the characteristics of small size, high bioavailability and strong plasticity. With the development of related research on nanoparticles in inner ear diseases, nanoparticles have gradually become a research hotspot in inner ear diseases. This review briefly summarizes the research progress, opportunities and challenges of the application of nanoparticles in inner ear diseases.

Wave Propagation and Energy Dissipation in Collagen Molecules

Collagen is the key protein of connective tissue (i.e., skin, tendons and ligaments, and cartilage, among others), accounting for 25-35% of the whole-body protein content and conferring mechanical stability. This protein is also a fundamental building block of bone because of its excellent mechanical properties together with carbonated hydroxyapatite minerals. Although the mechanical resilience and viscoelasticity have been studied both in vitro and in vivo from the molecular to tissue level, wave propagation properties and energy dissipation have not yet been deeply explored, in spite of being crucial to understanding the vibration dynamics of collagenous structures (e.g., eardrum, cochlear membranes) upon impulsive loads. By using a bottom-up atomistic modeling approach, here we study a collagen peptide under two distinct impulsive displacement loads, including longitudinal and transversal inputs. Using a one-dimensional string model as a model system, we investigate the roles of hydration and load direction on wave propagation along the collagen peptide and the related energy dissipation. We find that wave transmission and energy-dissipation strongly depend on the loading direction. Also, the hydrated collagen peptide can dissipate five times more energy than dehydrated one. Our work suggests a distinct role of collagen in term of wave transmission of different tissues such as tendon and eardrum. This study can step toward understanding the mechanical behavior of collagen upon transient loads, impact loading and fatigue, and designing biomimetic and bioinspired materials to replace specific native tissues such as the tympanic membrane.

A Tanshinone IIA loaded hybrid nanocomposite with enhanced therapeutic effect for otitis media

Otitis media, commonly known as middle ear inflammation, is among one of the most common maladies and results in significant morbidity such as loss of hearing. In view of the bacteria invasion such as Staphylococcus aureus causes the majority forms of otitis media, drug treatment generally uses antibacterial by topical or systematic approach. However, the effectiveness of antibacterial is diminishing because of the rapid emergence of antibiotic-resistant bacterial strains. Here, we designed and fabricated a silver nanoparticle (AgNPs)-based multicomponent hybrid nanocomposite termed as TSIIA @ CS/Lys @ AgNPs, which was comprised of a AgNPs core, a chitosan (CS) or lysozyme (Lys) middle layer, and a Tanshinone IIA (TSIIA) inclusion outlayer. Coating of CS or Lys to AgNPs through electrostatic interaction probably produced a core-shell nanocomplex resembling the endocarp of walnut. This design could reduce the dosage of AgNPs while maintaining antibacterial activity possibly due to the favorable interactions between nanocomplex and bacteria. The deposition of Chinese herb active component TSIIA by inclusion complexation formed the out layer of hybrid nanocomposite towards an improved antibacterial performance, which showed a therapeutic effect against acute otitis media of guinea pig comparable to the clinical commercial-used ofloxacin administrated by injection. The hybrid nanocomposite, when dispersed in poly (lactic-co-glycolic acid)/N-methyl-2-pyrrolidone (PLGA/NMP) solution as an in-situ organogel, not only maintained the therapeutic effectiveness, but also possessed the advantage of lower injection frequency compared with solution formulation. In addition, no obvious toxicity to the basilar membrane and epithelia tissue was observed after the healthy guinea pigs were treated with hybrid nanocomposite or organogel. This study provides a promising strategy to develop hybrid nanocomposite with enhanced antibacterial efficacy and also opens a new way for the establishment of efficient therapeutic systems with reduced administration frequency as substitute of antibiotics to treat otitis media.

De novo topology optimization of total ossicular replacement prostheses

Conductive hearing loss, due to middle ear pathologies or traumas, affects more than 5% of the population worldwide. Passive prostheses to replace the ossicular chain mainly rely on piston-like titanium and/or hydroxyapatite devices, which in the long term suffer from extrusion. Although the basic shape of such devices always consists of a base for contact with the eardrum and a stem to have mechanical connection with the residual bony structures, a plethora of topologies have been proposed, mainly to help surgical positioning. In this work, we optimize the topology of a total ossicular replacement prosthesis, by maximizing the global stiffness and under the smallest possible volume constraint that ensures material continuity. This investigation optimizes the prosthesis topology in response to static displacement loads with amplitudes that normally occur during sound stimulation in a frequency range between 100 Hz and 10 kHz. Following earlier studies, we discuss how the presence and arrangement of holes on the surface of the prosthesis plate in contact with the umbo affect the overall geometry. Finally, we validate the designs through a finite-element model, in which we assess the prosthesis performance upon dynamic sound pressure loads by considering four different constitutive materials: titanium, cortical bone, silk, and collagen/hydroxyapatite. The results show that the selected prostheses present, almost independently of their constitutive material, a vibroacustic behavior close to that of the native ossicular chain, with a slight almost constant positive shift that reaches a maximum of ≈5 dB close to 1 kHz. This work represents a reference for the development of a new generation of middle ear prostheses with non-conventional topologies for fabrication via additive manufacturing technologies or ultraprecision machining in order to create patient-specific devices to recover from conductive hearing loss.