Advanced cell-laden nanofibrous scaffolds for the regeneration of complex human tissues

Abstract

Scaffolds produced by electrospinning possess great potential for tissue engineering owing to their biomimetic nanofibrous structures and their ability to deliver growth factors for directing cell behavior. However, scaffolds made by conventional electrospinning have limitations for tissue engineering of complex human body tissues, including small interconnected pores, undesirable release behavior of bio-signals in local delivery, and 2D cell-scaffold organization. Electrospray emerged in recent years as an attractive technology for making particular delivery vehicles for drugs and biomolecules. This project aimed to design, fabricate and investigate novel scaffolds with superior properties, which would be made by novel electrospinning and/or electrospray techniques, for the regeneration of complex human tissues. Major efforts were made to improve the properties of electrospun scaffolds in different areas, including enlarging the pores in scaffolds, modifying and controlling the release behaviour of growth factors, developing scaffolds with potential antibacterial property or scaffolds with anticancer property, and constructing and studying growth factor-incorporated and cell-laden nanofibrous scaffolds with biomimetic three-dimensional cell-scaffold organization.

First, a sacrificial strategy and a charge-neutralization strategy were investigated for enhancing the pore size and porosity of electrospun scaffolds without significantly affecting their nanofibrous structure. Using the sacrificial strategy, electrospun nanofibrous scaffolds with enlarged pores were formed through the removal of sacrificial electrospun fibers from intermeshed bicomponent scaffolds made by dual-source dual-power electrospinning. Using the charge-neutralization strategy, electrospun nanofibrous scaffolds with enlarged pores were also formed by concurrent positive voltage electrospinning and negative voltage electrospinning. Results showed that the scaffolds formed by using the charge-neutralization strategy possessed superior mechanical properties and structural stability.

Second, novel emulsion electrospinning techniques including polyelectrolyte-incorporated emulsion electrospinning and negative voltage emulsion electrospinning were developed for modulating the release behavior of growth factors from nanofibers. Steady and sustained release of growth factors could be achieved by using nanofibrous delivery vehicles made by these novel emulsion electrospinning techniques. Furthermore, controlled release of growth factors (either sustained release or burst release) could be achieved by using microspherical delivery vehicles made by different electrospray techniques. The effectiveness and efficiency of growth factors delivery for tissue engineering were enhanced.

Third, functional nanoparticles such as functionalized silver nanoparticle (AgNP) or novel gold nanoparticle (AuNP)-based theranostics were synthesized and then incorporated into electrospun nanofibrous scaffolds through either emulsion electrospinning or concurrent electrospinning and coaxial electrospray. Fibrous scaffolds with the incorporation and controlled release of functional nanoparticles would provide antibacterial or anticancer function for specific tissue engineering applications.

Finally, live cell microencapsulation and controlled cell delivery were investigated and achieved by using cell-encapsulated hydrogel microspheres formed by coaxial cell electrospray. On basis of this cell electrospray technology, a novel concurrent emulsion electrospinning and coaxial cell electrospray technique was developed to directly place cells into the nanofibrous matrix of growth factor-incorporated emulsion electrospun scaffolds. Endothelial cells in these scaffolds exhibited high cell viability and showed enhanced cell-cell and cell-scaffold interactions. The growth factor-incorporated and cell-laden nanofibrous scaffolds resemble native extracellular matrix and are promising for improving vascularization in scaffolds and for the regeneration of specific tissue layer of complex human tissues.