Hydrogels based on Fmoc-diphenylalanine and Fmoc-diglycine for nucleus pulposus disc tissue engineering

With a view to repair the degenerated nucleus
pulposus (NP) of intervertebral discs, we grew bovine NP cells
on fluorenylmethoxycarbonyl-diphenylalanine (Fmoc-FF)/
Fmoc-diglycine (Fmoc-GG) hydrogels. The gels prepared in
two different molar ratios of Fmoc-FF to Fmoc-GG, 1:0 and
1:1. These gels were characterized in terms of their physical
and biological properties including fibre structure, cell
attachment, collagen and sulphated glycosaminoglycan
(s-GAG) productions.
Fmoc-FF and the composition of 1:1
Fmoc-FF/Fmoc-GG hydrogels (20 mmol/L) were synthesized
by utilizing a sequential change in pH (Jayawarna et al, 2007).
Fibre structure of hydrogels was determined by using CryoSEM. In vitro studies of hydrogels seeded by NP cells were
performed using red fluorescent cell membrane dye PKH-26,
confocal microscopy, Sircol
collagen and DMMBTM assays.
Cryo-SEM showed a dense network of fine fibres in
Fmoc-FF, whereas an overlapping mesh of flat ribbons was
seen in the composition of 1:1 Fmoc-FF/Fmoc-GG. Confocal
microscopy showed the majority of the NP cells stained with
PKH-26 remained in a rounded morphology within both
Fmoc-FF and the composition of 1:1 Fmoc-FF/Fmoc-GG
hydrogels after 5 days of culture. SircolTM and DMMB
assays showed deposition of collagen and sulphate-glycosaminoglycan by NP cells cultured within both Fmoc-FF and
the composition of 1:1 Fmoc-FF/Fmoc-GG over 3 weeks of
culture.
Taken together, the results of present study provide
preliminary evidence for the use of a self-assembling peptide
hydrogel as a scaffold for the synthesis and accumulation of
NP-like extracellular matrix for intervertebral disc tissue
repair.