Electrospun nanofibrous scaffolds for human tympanic membrane repair

Abstract

Human tympanic membrane (TM) perforation is one of the most common problems in otolaryngology leading to middle ear infection, conductive hearing loss and associated speech problems. Current clinical treatment to TM perforations is limited in complex surgical procedures and autologous materials availability. Herein this study, tissue engineering concept was adopted to develop multifunctional nanofibrous poly(lactic-co-glycolic acid)/hyaluronic acid (PLGA/HA) scaffolds via electrospinning. Growth factors and antibiotics were incorporated to enhance the biocompatibility and address infection-related problems.
Firstly, the relationship between the solution properties of PLGA/HA system and its electrospinnability was studied to optimize the polymer composition. The critical PLGA concentration to ensure efficient chain entanglements for successful electrospinning was determined via rheological studies. Blending with HA results in lower concentration dependence and higher solution conductivity (up to three times of pure PLGA solutions). Overall, nanofibres generated from 35% PLGA/1.5% HA and 40% PLGA/1.5% HA (w/v) electrospinning solutions exhibited uniform and beadless morphology.
The electrospun nanofibrous films were then characterised to determine the optimal composition for further functionalization. Higher PLGA content in electrospun films led to thicker nanofibres, lower wettability, better mechanical performance and higher cell viability. Among all studied composition, 40% PLGA/1.5% HA showed comparable mechanical properties to native human TM and optimal biocompatibility. Basic fibroblast growth factors (bFGF) were loaded into as-spun nanofibres to construct bioactive PLGA/HA/bFGF nanofibrous scaffolds. The wettability of scaffolds was significantly improved from 127.3 ± 4.3˚ to 108.3 ± 6.8˚ (pFinally, a “smart” bacteria-responsive nanofibrous scaffold was developed by coaxial electrospinning to address the common infection-related TM perforations. The blending PLGA/HA system from previous study was set as the shell structure with levofloxacin (Lex) loaded in the core of the nanofiber. It was expected that bacteria-secreted hyaluronidase (HAase) would degrade the HA component residing on the sheath leaving a porous outer layer. Inner Lex would release through the pores to exert antibacterial abilities. Results from the in vitro Lex release study showed that Lex could be efficiently released up to 98.3 ± 3.5 % at day 15 under the HAase condition, but only 37.1 ± 2.4 % released under PBS condition. Lex was directly added in blending PLGA/HA as controls that showed comparable accumulative release of Lex under both conditions. Lex-loaded coaxial and blending samples both showed excellent antibacterial performance against S. aureus and P. aeruginosa. However, coaxial PLGA/HA-Lex scaffolds exhibited lower level of Lex releasing compared to blending PLGA/HA/Lex samples in cell culturing, and higher cell viability with better cell morphology. Collectively, the developed PLGA/HA-Lex nanofibrous scaffolds showed an adaptive ability to release antibiotics upon bacterial infection but preserved it in normal physiological environment. It is the first time to realize bacteria-responsive drug releasing via coaxial electrospinning technique and adopt the adaptive concept on human TM repair. Such “smart” antibacterial nanofibrous scaffolds show efficient antibacterial ability while avoid side effects to normal tissue.

Date of Award	Mar 2023
Original language	English
Awarding Institution	University of Nottingham
Supervisor	Xiaoling Liu (Supervisor), Chris Rudd (Supervisor) & Ifty Ahmed (Supervisor)