The preparation of PLL–GRGDS modified PTSG copolymer scaffolds and their effects on manufacturing artificial salivary gland

Abstract

We prepared two-dimentional (2D) and three-dimentional (3D) scaffolds with biodegradable poly(butylene terephthalate)-co-poly(butylene succinate)-b-poly(ethylene glycol) (i.e. PTSG), mainly for the purpose of investigating its cytocompatibility and mechanical property as artificial salivary gland material. The surface of 2D scaffold (i.e. PTSG film) was modified by O₂ plasma treatment and the following coating of Gly–Arg–Gly–Asp–Ser (GRGDS) decorated poly(L-lysine) (i.e. PLL–GRGDS). The obtained film was named PLL–GRGDS/PTSG (O). Its surface properties were characterized using contact angles, surface energies, X-ray photoelectron spectroscopy and Fourier transform infrared; and cytocompatibility tests in vitro including morphology, attachment and proliferation of human salivary gland (HSG) epithelial cells were further performed on PTSG films. Meanwhile, 3D scaffold with the shape of porous tube was constructed using hydrogel-rapid prototyping and the performance of 3D scaffold including mechanical property, pore structure, degradation and water uptake was also evaluated. Results revealed that PLL–GRGDS/PTSG (O) possessed the high surface free energy (63.89 mJ/m²) and could immobilize a great amount of PLL–GRGDS, which attributed to the formation of some polar oxygen-containing groups such as carboxyl and carbonyl ones in the process of O₂ plasma treatment. Cell tests in vitro suggested the efficiency of surface modification in enhancing the cytocompatibility of PTSG. Furthermore, the manufacturing scaffold was proved to possess excellent pore structures (porosity 88.9%, connectivity 97.5% and average pore size 35.4 μm) and good mechanical properties (E-modulus 88.4 ± 4.1 kPa, yield stress 45.7 ± 2.3 kPa, yield strain 56 ± 2%, fracture stress 52.2 ± 3.5 kPa and fracture strain 63 ± 3%). After four weeks hydrolysis reaction, the degradation of the scaffold reached 8% and equilibrium water uptake declined from 51 to 45%. The decline of water uptake was probably caused by the decrease of the hydrophilic units in PTSG copolymer during degradation. These results satisfied the demands for constructing the artificial salivary gland scaffold.

Keywords:

• PTSG
• PLL–GRGDS
• surface modification
• hydrogel-rapid prototyping
• scaffold

Acknowledgements

This work is financially supported by National Natural Science Foundation of China and Natural Science Foundation of Jiangsu Higher Education Institutions (grant no. 12KJB530001). Financial support from Priority Academic Program Development of Jiangsu Higher Education Institutions is also acknowledged.