Engineering Graded Tissue Interfaces - Structural Interfaces and Attachments in Biology - page 301

Fig. 14.3 ( a ) Schematic of electrospinning apparatus. Gradients were created in the z direction
(scaffold depth) by modulating flow rates of Polymer 1 and Polymer 2, which were mixed prior to
the spinnerette and electrospinning. ( b ) Change in pump flow rate with time for Polymer 1 and
Polymer 2. ( c ) Electrospinning solution (Polymer 1 solution contained a fluorescent dye, whereas
Polymer 2 solution did not) was collected from the spinnerette every hour for 8h, prior to
electrospinning, and the fluorescence was measured as shown. A decrease in fluorescence intensity
with time verifies the potential gradient formation at the spinnerette and therefore potential
gradient formation in the electrospun mat. ( d ) SEM micrographs show similar fiber morphology
on the top and bottom of an electrospun gradient scaffold (scale bar = 10 ) (reproduced, with

m

permission, from [ 103 ])

in finding suitable matrices for the regeneration of bone and its interfaced zone.
Patterned electrospun mats were developed using electro-conducting templates [ 101 ].
A functionally graded nonwoven mesh of polycaprolactone incorporated with
TCP nanoparticles was fabricated using a hybrid twin-screw extrusion/
electrospinning (TSEE) process to engineer the fibrocartilage-bone interface
[ 102 ]. This technology utilized a time-dependent feeding of various solid and liquid
ingredients. Their melting, dispersion, de-aeration, and pressurization together with
electrospinning were confined within a single process. Three distinct yet continuous
phases were fabricated for the ligament, interface, and bone regions. The interface-
relevant cell types fibroblasts, chondrocytes, and osteoblasts were tri-cultured on
this scaffold and implanted subcutaneously in athymic rats. The results indicated
that the multiphase scaffold design and tissue-specific distribution of cells resulted
in the formation of a fibrocartilage-interface like tissue. A phase-specific distribu-
tion of mineralized matrix was observed corresponding to the bone region. In a
recent study, haptotactic and durotactic gradients were introduced in hyaluronic
acid-based electrospun scaffolds by varying the extent of methacrylation units and
the amount of RGD peptide. These gradients were made by modifying