A representative stress-strain curve showing the four stage-loading protocol used for the native discs and biphasic constructs.

<p>Samples were subjected to: pre-load (A) at 0.6 MPa for 150 sec and then 0.1 MPa for 600 sec; creep (B) at 0.6 MPa for 12,000 sec; dynamic load (C) at sine stresses between 0.3 and 0.9 MPa at 0.1, 0.32, 1, 3.2 and 10 Hz (linear log scale); and recovery (D) at 0.1 MPa for 12,000 sec.</p

Histomorphometric and ultrastructural characterization of the fabricated biphasic scaffold and native disc.

<p>(A-D) Fabricated biphasic scaffold and (E-H) native disc; (A&E) Alcian blue staining and (B&F) immunohistochemistry of type I collagen. (C-D & G&H) SEM images. (C) AF-like collagen lamellae; (D) NP-like core with compaction; (D1) NP-like core without compaction; (G) AF lamellae in the native disc; (H) NP core in the native disc. Scale bars are 500 μm (for A-B & E-F); 10 μm (for C&G); 1 μm (for G1) and 500 nm (for D-D1&H).</p

Series of images to show the fabrication of the biphasic scaffold an intervertebral disc.

<p>(A) A CG core was encapsulated in the first collagen layer before crosslinking. (B) Some of the photochemically-crosslinked CG cores were then encapsulated in a further 1 to 9 layers of collagen. (C) Immersion of the CG core with collagen layers in the photosensitizer, rose Bengal. (D) Irradiation of the construct with an argon laser at 514 nm for photochemical crosslinking. (E) Dehydration of the CG containing the 1^st collagen layer by rolling it on absorbent filter paper. (F) Dehydration of the CG core now encapsulated in the 2^nd to 10^th collagen layers. (G) The rehydrated CG core in one of the AF-like collagen lamella (E1). (H) Rehydrated CG core in two to ten collagen lamellae (E2 to E10). (I) Condensed biphasic scaffold in top view. (J) Condensed biphasic scaffold in side view. (K) Rabbit disc harvest. (L) Native rabbit disc in top view. (M) Native rabbit disc in side view.</p

Bar charts showing the mechanical properties of samples during the creep and recovery phases of the mechanical tests.

<p>The mechanical properties of the fabricated biphasic scaffolds and native IVD (A-D) during the creep and (E-H) recovery phases. (A&E) Elastic compliance (E, mm/N); (B&F) Viscous compliance (V, mm/N); (C&G) Time constants (T, seconds) and (D&H) Stretch constants (B). Data are expressed as mean±2SE of n = 2–4 experiments.</p

Gross appearance and dimension analysis of the samples in the different groups before and after biomechanical testing.

<p>(A-D) Gross appearance of the biphasic scaffolds from side (A-B) and top (C-D) views before (A,C) and after (B,D) the mechanical tests. (E-G) Dimension analysis of the biphasic scaffolds (with 1, 2, 4 and 10 layers of collagen lamellae) and the native disc controls at different stages during the mechanical test (i.e., before and after pre-load, after the creep, and after the test). Bar graphs show: (E) disc diameter, (F) disc height, and (G) percentage of disc height recovery. Data are expressed as mean+-2SE of n = 2–4 experiments.</p

Dynamic stiffness and damping factor of samples during the dynamic mechanical analysis (DMA).

<p>(A) Line chart of the dynamic stiffness against the log loading frequency. (B) Bar chart showing the slope values measured for the dynamic stiffness-log loading frequency curves (mean+-2SE, n = 2–4). (C) Line charts of the damping factor (tangent delta) against log loading frequency; D: Bar chart showing the slopes of the tangent delta-log loading frequency curves (mean+-2SE, n = 2–4).</p