Design and tuning of an in-vitro sound stimulation system in a controlled environment for inner ear tissues

reservedQuesto lavoro di tesi ha come scopo principale la messa a punto di un sistema di induzione del danno da rumore su colture cellulari in vitro mimiche del tessuto neurosensoriale dell’orecchio interno. Un’analisi approfondita della letteratura esistente [Kwak et al., 2022] ha evidenziato una mancanza di omogeneità in termini di modelli biologici e parametri acustici utilizzati da cui è nata la necessità di progettare e realizzare un ambiente sonoro controllato per effettuare i test acustici. A tal fine il sistema è stato realizzato applicando strutture fono assorbenti ad un incubatore per cellule prodotto in plexiglass, due casse acustiche da 45 watt, un microfono da misurazione ed in fine è stato scelto il software REW (Room Eq Wizard by John Mulcahy) di produzione e registrazione del suono controllato. In seguito sono stati eseguiti i test preliminari verificando sia la funzionalità degli strumenti acustici adottati sia l’adeguatezza dell’incubatore insonorizzato. Il collaudo dell’incubatore è stato eseguito analizzando la vitalità cellulare dei modelli in vitro ponendoli all’interno di esso, in assenza di stimolazione sonora, per un periodo da 1 a 3 ore. Nella fase successiva del progetto mediante l’analisi della vitalità e morfologia cellulari è stato possibile validare il setup del sistema di stimolazione sonora: il suono è stato somministrato in range da 1-2kHz, 2-4kHz e 4-8kHz per un tempo pari a 20 minuti ad intensità di 100dBSPL, su 2 linee cellulari, una mimica del tessuto sensoriale ed una del tessuto neuronale. Dai dati preliminari si evince una maggiore sensibilità delle cellule sensoriali evidenziata con una minore vitalità quando esposte alla banda 2-4kHz, mentre per quanto riguarda la linea neuronale è stato riscontrato un aumento della complessità della rete neuritica. Questi ultimi dati permetteranno di quantificare l’entità del danno causato dalle onde sonore. Isolare i tessuti dall’ambiente sistemico permetterà di comprendere quali stimoli possono essere favorevoli e quali nocivi al fine di ottimizzare la pianificazione di conseguenti sperimentazioni in vivo

Role of Kir4.1 Channel in Auditory Function: Impact on Endocochlear Potential and Hearing Loss

Hearing loss can result from impairments in structures that support endocochlear potential, as they play a crucial role in the transduction and transmission of auditory waves. This aspect has been the subject of several studies to date. In our review, the role of ion transport channels and pumps involved in hearing function has been highlighted, emphasizing how important the Kir4.1 channel is in maintaining the endocochlear potential. The Kir4.1 channel, a member of the inwardly rectifying potassium channel (Kir) family, plays a key role in the regulation of cell electrical activity and potassium ion homeostasis. The cochlear expression of these channels is at the level of the intermediate cells of the vascular stria, in the root cells of the outer sulcus, and in the glial cells of the spiral ganglion. In development, its expression demonstrates its involvement in the progression of pathologies related to potassium channel dysfunction, and its activation in the stria vascularis is directly related to the generation of endocochlear potential. Kir4.1 is fundamental in stabilizing the resting membrane potential of cells and modulating their excitability, as it facilitates a greater influx of potassium into cells compared to efflux when the membrane potential is negative. Mutations in the K+ channel gene KCNJ10 (Kir4.1) have been associated with several disorders, with the most significant studies on EAST/SeSAME syndrome and Pendred syndrome. Recent research has explored the metabolic importance of potassium channel changes associated with stria vascularis degeneration in the progression of age-related hearing loss. Furthermore, in ototoxicity studies, the Kir4.1 channel has been shown to have the ability to compensate for the deficiency of other K+ channels, as it maintains the cochlear homeostasis by correcting the imbalanced K+ concentration

Self‐Powered Nanostructured Piezoelectric Filaments as Advanced Transducers for New Cochlear Implants

The conversion of sound vibration into electrical potential is a critical function performed by cochlear hair cells. Unlike the regenerative capacity found in various other cells throughout the body, cochlear sensory cells lack the ability to regenerate once damaged. Furthermore, a decline in the quantity of these cells results in a deterioration of auditory function. Piezoelectric materials can generate electric charge in response to sound wave vibration, making them theoretically suitable for replacing hair cell function. This study explores an innovative approach using piezoelectric nanocomposite filaments, namely poly(vinylidene fluoride), poly(vinylidene fluoride)/barium titanate, and poly(vinylidene fluoride)/reduced graphene oxide, as self-powered acoustic sensors designed to function in place of cochlear hair cells. These flexible filaments demonstrate a unique ability to generate electricity in response to frequency sounds from 50 up to 1000 Hz at moderate sound pressure levels (60-95 dB), approaching the audible range with an overall acoustoelectric energy conversion efficiency of 3.25%. Serving as self-powered acoustic sensors, these flexible filaments hold promise for potential applications in cochlear implants, with a high sensitivity of 117.5 mV (Pacm2)-1. The cytocompatibility of these filaments was assessed through in vitro viability tests conducted on three cell lines, serving as a model for inner ear cells.This article explores new material formulations for treating sensorineural hearing loss, an often-irreversible condition with significant psychosocial impacts. Currently, cochlear implants (CIs) are the only treatment, but they are expensive and require invasive surgery. Our approach involves self-powered acoustic transducer fibers to develop biomaterial-based CIs, eliminating the need for electronics. imag