Supramolecular polymer/peptide hybrid hydrogels with tunable stiffness mediated by interchain acid-amide hydrogen bonds

Yu-Shen Liu; Rajan Deepan Chakravarthy; Abdelreheem Abdelfatah Saddik; Mohiuddin Mohammed; Hsin-Chieh Lin

doi:10.1039/d2ra01944b

Supramolecular polymer/peptide hybrid hydrogels with tunable stiffness mediated by interchain acid-amide hydrogen bonds

RSC Adv. 2022 May 11;12(22):14315-14320. doi: 10.1039/d2ra01944b. eCollection 2022 May 5.

Authors

Yu-Shen Liu^{1

2}, Rajan Deepan Chakravarthy^{1

2}, Abdelreheem Abdelfatah Saddik^{1

2

3}, Mohiuddin Mohammed^{1

2}, Hsin-Chieh Lin^{1

2}

Affiliations

¹ Department of Materials Science and Engineering, National Yang Ming Chiao Tung University Hsinchu 300 Taiwan hclin45@nycu.edu.tw.
² Department of Materials Science and Engineering, National Chiao Tung University Hsinchu 300 Taiwan.
³ Materials Science and Engineering Laboratory, Department of Chemistry, Faculty of Science, Assiut University Assiut 71516 Egypt.

Abstract

Hydrogels are a class of biomaterials used in the field of tissue engineering and drug delivery. Many tissue engineering applications depend on the material properties of hydrogel scaffolds, such as mechanical stiffness, pore size, and interconnectivity. In this work, we describe the synthesis of peptide/polymer hybrid double-network (DN) hydrogels composed of supramolecular and covalent polymers. The DN hydrogels were prepared by combining the self-assembled pentafluorobenzyl diphenylalanyl aspartic acid (PFB-FFD) tripeptide for the first network and the polymeric PNIPAM-PEGDA copolymer for the second network. During this process, self-assembled peptide nanostructures are cross-linked to the polyacrylamide group in the polymer network through non-covalent interactions. The PNIPAM-PEGDA:PFB-FFD hydrogel exhibited higher mechanical stiffness (G' ∼2 kPa) than the PNIPAM-PEGDA copolymer. Moreover, PNIPAM-PEGDA:PFB-FFD hydrogel shows a decrease in pore size (∼1.2 μm) compared to the original copolymer (∼5.2 μm), with the structural framework of highly interconnected fibrous peptide network. The mechanical stiffness of hydrogels was systematically investigated by rheological analysis in response to various variables, including UV exposure time, concentration of peptides, and amino acid functionalization. Modulating the time of UV irradiation resulted in PNIPAM-PEGDA:PFB-FFD hydrogels with a four-fold increase in stiffness. The influence of amino acid side chains and terminal charge of peptides on the strength of DN hydrogels was also investigated using pentafluorobenzyl diphenylalanyl lysine (PFB-FFK). Interestingly, PFB-FFK, which has an amine group on the side chain, does not exhibit the DN structures. The mechanical properties and pore sizes of PNIPAM-PEGDA:PFB-FFK hydrogel were very similar to those of the PNIPAM-PEGDA copolymer due to poor cross-linking. The biocompatibility of the hydrogel materials was tested with the hMSC cell line using the MTT method, and the results indicate that the materials are non-toxic and potentially useful for biological applications.