Z-L-glutamic acid g-tert-butyl ester a-N-hydroxysuccinimide ester

Mechanical load influences bone structure and mass. Arguing the importance of load-transduction, we investigated the mechanisms inducing bone formation using an elastomeric substrate. We characterized Poly (glycerol sebacate) (PGS) in vitro for its mechanical properties, compatibility with osteoprogenitor cells regarding adhesion, proliferation, differentiation under compression versus static cultures and in vivo for the regeneration of a rabbit ulna critical size defect. The load-transducing properties of PGS were compared in vitro to a stiffer poly lactic-co-glycolic-acid (PLA/PGA) scaffold of similar porosity and interconnectivity. Under cyclic compression for 7days, we report focal adhesion kinase overexpression on the less stiff PGS and upregulation of the transcription factor Runx2 and late osteogenic markers osteocalcin and bone sialoprotein (1.7, 4.0 and 10.0 folds increase respectively).

Poly(glycerol sebacate) (PGS), a promising scaffold material for soft tissue engineering applications, is a soft, tough elastomer with excellent biocompatibility. However, the rapid in vivo degradation rate of PGS limits its use as a scaffold material. To determine the impact of crosslink density on degradation rate, a family of PGS materials was synthesized by incrementally increasing the curing time from 42 to 144 h, at 120 degrees C and 10 mTorr vacuum. As expected, PGS became a stiffer, tougher, and stronger elastomer with increasing curing time. PGS disks were subcutaneously implanted into rats and periodically harvested; only mild tissue responses were observed and the biocompatibility remained excellent. Regardless of crosslink density, surface erosion degradation was observed. The sample dimensions linearly decreased with implantation time, and the mass loss rates were constant after 1-week implantation. As surface erosion degradation frequently correlates with enzymatic digestion, parallel in vitro digestion studies were conducted in lipase solutions which hydrolyze ester bonds. Enzymatic digestion played a significant role in degrading PGS, and the mass loss rates were not a function of curing time. Alternative chemistry approaches will be required to decrease the enzymatic hydrolysis rate of the ester bonds in PGS polymers.

Poly(glycerol-sebacate) (PGS) is an elastomeric biodegradable polyester. Our previous series of studies have showed that PGS has good biocompatibility. In view of the potential use of PGS in bioengineering, we attempt to characterize the PGS polymer with different ratio of glycerol and sebacic acid, and the cell adhesion and growth on these polymers. PGSs with different proportion of glycerol and sebacic acid were synthesized by polycondensation reaction. The microstructure of the series PGSs were characterized by infrared spectroscopy and X-ray diffraction analysis (XRD). Results showed that, with the increase of the ratio of sebacic acid in PGS from 1:0.8, 1:1, to 1:1.2 (ratio of glycerol to sebacic acid), the main diffraction peak in XRD, the sol content and gel swelling increased but then decreased, suggesting that the degree of crosslinking and the inherent degree of order of the series PGS increased and then decreased. With the increase of sebacic acid proportion, water absorption increased and then decreased, and the water absorption ranged from 9.62% to 10.66%. The mass loss of the series of samples in degradation experiments ranged from 24.63% to 40.06% on the 32nd day of degradation. Cell culture data suggested that the polymer with the ratio of 1:0.8 for glycerol and sebacate was suitable for cell adhesion and growth. In conclusion, PGS can be used as the cell culture matrix by modifying the composition ratio of glycerol and sebacic acid to improve the properties of cell adhesion and growth.