Degradable and thermal responsive hyperbranched polymers synthesized via one-pot RAFT polymerisation for injectable scaffold applications

In tissue engineering, injectable scaffolds offer the possibility of homogeneously distributing cells and therapeutic molecules throughout the
scaffolds, and can be injected directly into cavities with irregular shapes and sizes. However, the challenge lies in finding suitable materials
which can solidify insitu
to form 3D microenvironments with the desired mechanical and biological properties. Crosslinkable and smart
polymers, which change in response to external stimuli such as temperature, pH and enzyme, have attracted much attention for such
applications. The objective of this work is to develop injectable biodegradable hydrogels from hyperbranched polymers (HBP) with responsive,
crosslinkable and degradable properties. These injectable hydrogels can have tailored mechanical properties and functionalities for cell
adhesion via decorating with peptide motifs and for controlled release of therapeutic drugs. Here, we report the synthesis of new
thermoresponsive HBP via onepot
reversible addition fragmentation chain transfer (RAFT) copolymerization of poly (ethylene glycol) methyl
ether methacrylate (PEGMEMA, Mn = 475), poly (propylene glycol) methacrylate (PPGMA, Mn = 375) and disulphide diacrylate (DSDA) using
2cyanoprop2yl
dithiobenzoate as RAFT agent. Enzymatic degradable DSDA was used as the branching agent; PEGMEMA and PPGMA
were used as macromers to balance hydrophilicity/hydrophobicity thus obtain desired low critical solution temperatures (LCST). The resulted
HBP were characterised by NMR and GPC, and LCSTs were also determined. Moreover, the studies on the degradability and swelling
properties of hydrogels prepared by the resultant HBP were conducted. The experimental results demonstrated that these degradable and
thermoresponsive HBP can be used as tissue engineering injectable scaffolds.