Injectable porous hydrogels represent an advanced class of biomaterials for minimally invasive surgery, providing a supportive microenvironment for cell encapsulation, proliferation and tissue regeneration.
In this work, we present a fully synthetic and biodegradable hydrogel based on poly(α-amino acid) (PolyAA), a versatile polymeric biomaterial with tunable physicochemical properties and enzymatic degradability [1]. The polymeric precursor was functionalised with biocompatible tyramine groups allowing diphenol bond formation through enzymatic (HRP/H₂O₂, in situ H₂O₂) or photoinitiated (Ru(II) complex/(NH₄)₂S₂O₈, 450 nm light) cross-linking [1, 2]. Porous structures with interconnected pores were formed using an aqueous two-phase system (ATPS) with polyethylene oxide (PEO) as porogen. A novel single-step strategy incorporating a branched dihydroxyphenyl RGD peptide was employed to enhance cell adhesion while maintaining precise control over the peptide concentration.
Physicochemical characterization (NMR, UV-Vis, GPC) confirmed the successful synthesis of the polymer precursor. The gelation time, gel yield, swelling, and mechanical properties of the resulting hydrogels were compared between the different crosslinking methods. The resulting hydrogels exhibited gel yields above 80%, swelling capacities of 10–30 g/g, and tunable gelation times (5–300 s) depending on the cross-linking method. The compressive modulus can be adjusted in the range of 5 to 50 kPa, allowing various applications in tissue engineering. Finally, the hydrogels were found not to be cytotoxic to human mesenchymal stem cells (hMSCs) in in vitro studies. The encapsulated hMSCs exhibited long-term survival, with cell-matrix and cell-cell interactions modulated by RGD concentration and hydrogel stiffness.
These findings establish the PolyAA/ATPS/RGD hydrogel system as a versatile and adaptive platform for next-generation injectable biomaterials in regenerative medicine.
[1] DVORAKOVA, Jana, et al. Enzymatically cross-linked hydrogels based on synthetic poly (α-amino acid) s functionalized with RGD peptide for 3D mesenchymal stem cell culture. Biomacromolecules, 2021, 22.4: 1417-1431.
[2] GOLUNOVA, Anna, et al. Fully synthetic, tunable poly (α-amino acids) as the base of bioinks curable by visible light. Biomedical Materials, 2024, 19.3: 035035.