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A Structurally and Functionally Biomimetic Biphasic Scaffold for Intervertebral Disc Tissue Engineering.

Choy AT, Chan BP - PLoS ONE (2015)

Bottom Line: On mechanical testing, the height of our engineered disc recovered by ~82-89% in an annulus-independent manner, when compared with the 99% recovery exhibited by native disc.Biphasic scaffolds comprised of 10 annulus fibrosus-like lamellae had the best overall mechanical performance among the various designs owing to their similarity to native disc in most aspects, including elastic compliance during creep and recovery, and viscous compliance during recovery.However, the dynamic mechanical performance (including dynamic stiffness and damping factor) of all the biphasic scaffolds was similar to that of the native discs.

View Article: PubMed Central - PubMed

Affiliation: Tissue Engineering Laboratory, Department of Mechanical Engineering, The University of Hong Kong, Hong Kong Special Administrative Region, China.

ABSTRACT
Tissue engineering offers high hopes for the treatment of intervertebral disc (IVD) degeneration. Whereas scaffolds of the disc nucleus and annulus have been extensively studied, a truly biomimetic and mechanically functional biphasic scaffold using naturally occurring extracellular matrix is yet to be developed. Here, a biphasic scaffold was fabricated with collagen and glycosaminoglycans (GAGs), two of the most abundant extracellular matrix components in the IVD. Following fabrication, the scaffold was characterized and benchmarked against native disc. The biphasic scaffold was composed of a collagen-GAG co-precipitate making up the nucleus pulposus-like core, and this was encapsulated in multiple lamellae of photochemically crosslinked collagen membranes comprising the annulus fibrosus-like lamellae. On mechanical testing, the height of our engineered disc recovered by ~82-89% in an annulus-independent manner, when compared with the 99% recovery exhibited by native disc. The annulus-independent nature of disc height recovery suggests that the fluid replacement function of the engineered nucleus pulposus core might mimic this hitherto unique feature of native disc. Biphasic scaffolds comprised of 10 annulus fibrosus-like lamellae had the best overall mechanical performance among the various designs owing to their similarity to native disc in most aspects, including elastic compliance during creep and recovery, and viscous compliance during recovery. However, the dynamic mechanical performance (including dynamic stiffness and damping factor) of all the biphasic scaffolds was similar to that of the native discs. This study contributes to the rationalized design and development of a biomimetic and mechanically viable biphasic scaffold for IVD tissue engineering.

No MeSH data available.


Related in: MedlinePlus

A representative stress-strain curve showing the four stage-loading protocol used for the native discs and biphasic constructs.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.
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pone.0131827.g002: A representative stress-strain curve showing the four stage-loading protocol used for the native discs and biphasic constructs.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.

Mentions: The biphasic scaffold and the disc were studied by unconfined compressive creep, dynamic mechanical analysis (DMA) and recovery (creep under reduced stress), using a bioreactor (ElectroForce 5210, BioDynamic System, Bose, Minnesota, USA) with 0.04 mm porous platens. Samples were immersed in PBS at room temperature overnight prior to the test, and then at 37°C throughout the test. A testing protocol was modified from two previous reports studying native IVD tissues [19,20]. The test in the current study was load-controlled and consisted of four stages, as shown in Fig 2. These are as follows: (A) Pre-load: ramping to and dwelling at 0.6 MPa for 150 sec, then ramping to and dwelling at 0.1 MPa for 600 sec. (B) Creep: ramping to and dwelling at 0.6 MPa for 12,000 sec. (C) Dynamic load: applying sinusoidal stress between 0.3 and 0.9 MPa at 0.1, 0.32, 1, 3.2 and 10 Hz (i.e., a linear log scale). The amplitude of loading used in the DMA corresponded to the normal range measured during daily activities (i.e., between -0.3 and -0.9 MPa) [18]. (D) Recovery: ramping to and dwelling at 0.1 MPa for 12,000 sec. The rate of ramp in Stages A, B and D were 10 N/s. In addition, the data acquisition rate was 20 Hz for the first 300 sec in Stage A, when the displacement changed rapidly, and then 1 Hz for Stages B and D. The acquisition rate was 500 Hz for Stage C, which is the default rate used by the machine software. For Stages B and D, the load-displacement data were split into two parts according to the load change, and fitted to model equations for the least square error using Excel Solver (Microsoft, Washington, USA). Thus, data describing a ramp section with ramped load within the first two sec of a stage, was fitted to Eq 1 for elastic compliance (E, in mm/N), while the remaining data, with steady load, was fitted to Eq 2 for viscous compliance (V, in mm/N), time constant (T, in s) and stretch constant (B, dimensionless), where t is time (in seconds), s(t) is displacement (in mm) at time t and F(t) is load (N) at time t.


A Structurally and Functionally Biomimetic Biphasic Scaffold for Intervertebral Disc Tissue Engineering.

Choy AT, Chan BP - PLoS ONE (2015)

A representative stress-strain curve showing the four stage-loading protocol used for the native discs and biphasic constructs.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.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4482706&req=5

pone.0131827.g002: A representative stress-strain curve showing the four stage-loading protocol used for the native discs and biphasic constructs.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.
Mentions: The biphasic scaffold and the disc were studied by unconfined compressive creep, dynamic mechanical analysis (DMA) and recovery (creep under reduced stress), using a bioreactor (ElectroForce 5210, BioDynamic System, Bose, Minnesota, USA) with 0.04 mm porous platens. Samples were immersed in PBS at room temperature overnight prior to the test, and then at 37°C throughout the test. A testing protocol was modified from two previous reports studying native IVD tissues [19,20]. The test in the current study was load-controlled and consisted of four stages, as shown in Fig 2. These are as follows: (A) Pre-load: ramping to and dwelling at 0.6 MPa for 150 sec, then ramping to and dwelling at 0.1 MPa for 600 sec. (B) Creep: ramping to and dwelling at 0.6 MPa for 12,000 sec. (C) Dynamic load: applying sinusoidal stress between 0.3 and 0.9 MPa at 0.1, 0.32, 1, 3.2 and 10 Hz (i.e., a linear log scale). The amplitude of loading used in the DMA corresponded to the normal range measured during daily activities (i.e., between -0.3 and -0.9 MPa) [18]. (D) Recovery: ramping to and dwelling at 0.1 MPa for 12,000 sec. The rate of ramp in Stages A, B and D were 10 N/s. In addition, the data acquisition rate was 20 Hz for the first 300 sec in Stage A, when the displacement changed rapidly, and then 1 Hz for Stages B and D. The acquisition rate was 500 Hz for Stage C, which is the default rate used by the machine software. For Stages B and D, the load-displacement data were split into two parts according to the load change, and fitted to model equations for the least square error using Excel Solver (Microsoft, Washington, USA). Thus, data describing a ramp section with ramped load within the first two sec of a stage, was fitted to Eq 1 for elastic compliance (E, in mm/N), while the remaining data, with steady load, was fitted to Eq 2 for viscous compliance (V, in mm/N), time constant (T, in s) and stretch constant (B, dimensionless), where t is time (in seconds), s(t) is displacement (in mm) at time t and F(t) is load (N) at time t.

Bottom Line: On mechanical testing, the height of our engineered disc recovered by ~82-89% in an annulus-independent manner, when compared with the 99% recovery exhibited by native disc.Biphasic scaffolds comprised of 10 annulus fibrosus-like lamellae had the best overall mechanical performance among the various designs owing to their similarity to native disc in most aspects, including elastic compliance during creep and recovery, and viscous compliance during recovery.However, the dynamic mechanical performance (including dynamic stiffness and damping factor) of all the biphasic scaffolds was similar to that of the native discs.

View Article: PubMed Central - PubMed

Affiliation: Tissue Engineering Laboratory, Department of Mechanical Engineering, The University of Hong Kong, Hong Kong Special Administrative Region, China.

ABSTRACT
Tissue engineering offers high hopes for the treatment of intervertebral disc (IVD) degeneration. Whereas scaffolds of the disc nucleus and annulus have been extensively studied, a truly biomimetic and mechanically functional biphasic scaffold using naturally occurring extracellular matrix is yet to be developed. Here, a biphasic scaffold was fabricated with collagen and glycosaminoglycans (GAGs), two of the most abundant extracellular matrix components in the IVD. Following fabrication, the scaffold was characterized and benchmarked against native disc. The biphasic scaffold was composed of a collagen-GAG co-precipitate making up the nucleus pulposus-like core, and this was encapsulated in multiple lamellae of photochemically crosslinked collagen membranes comprising the annulus fibrosus-like lamellae. On mechanical testing, the height of our engineered disc recovered by ~82-89% in an annulus-independent manner, when compared with the 99% recovery exhibited by native disc. The annulus-independent nature of disc height recovery suggests that the fluid replacement function of the engineered nucleus pulposus core might mimic this hitherto unique feature of native disc. Biphasic scaffolds comprised of 10 annulus fibrosus-like lamellae had the best overall mechanical performance among the various designs owing to their similarity to native disc in most aspects, including elastic compliance during creep and recovery, and viscous compliance during recovery. However, the dynamic mechanical performance (including dynamic stiffness and damping factor) of all the biphasic scaffolds was similar to that of the native discs. This study contributes to the rationalized design and development of a biomimetic and mechanically viable biphasic scaffold for IVD tissue engineering.

No MeSH data available.


Related in: MedlinePlus