Nanofibrous
structures have long been used as scaffolds for tissue
engineering (TE) applications, due to their favorable characteristics,
such as high porosity, flexibility, high cell attachment and enhanced
proliferation, and overall resemblance to native extracellular matrix
(ECM). Such scaffolds can be easily produced at a low cost via electrospinning
(ESP), but generally cannot be fabricated with a regular and/or complex
geometry, characterized by macropores and uniform thickness. We present
here a novel technique for direct writing (DW) with solution ESP to
produce complex three-dimensional (3D) multiscale and ultrathin (∼1
μm) fibrous scaffolds with desirable patterns and geometries.
This technique was simply achieved via manipulating technological
conditions, such as spinning solution, ambient conditions, and processing
parameters. Three different regimes in fiber morphologies were observed,
including bundle with dispersed fibers, bundle with a core of aligned
fibers, and single fibers. The transition between these regimes depended
on tip to collector distance (Wd) and applied voltage (V), which could be simplified as the ratio V/Wd.
Using this technique, a scaffold mimicking the zonal organization
of articular cartilage was further fabricated as a proof of concept,
demonstrating the ability to better mimic native tissue organization.
The DW scaffolds directed tissue organization and fibril matrix orientation
in a zone-dependent way. Comparative expression of chondrogenic markers
revealed a substantial upregulation of Sox9 and aggrecan
(ACAN) on these structures compared to conventional electrospun meshes.
Our novel method provides a simple way to produce customized 3D ultrathin
fibrous scaffolds, with great potential for TE applications, in particular
those for which anisotropy is of importance.