Peptide-Functionalized Oxime Hydrogels with Tunable Mechanical Properties and Gelation Behavior

Abstract

We demonstrate the formation of polyethylene glycol (PEG) based hydrogels via oxime ligation and the photo-initiated thiol-ene 3D patterning of peptides within the hydrogel matrix post-gelation. The gelation process and final mechanical strength of hydrogels can be tuned using pH and the catalyst concentration. The time scale to reach the gel point and complete gelation can be shortened from hours to seconds using both pH and aniline catalyst, which facilitates the tuning of the storage modulus from 0.3 kPa to over 15 kPa. Azide and alkene functionalized hydrogels were also synthesized and we have shown the post gelation “click” type Husigen 1,3 cycloaddition and thiolene-based radical reactions for spatially defined peptide incorporation. These materials are the initial demonstration for translationally relevant hydrogel materials that possess tunable mechanical regimes attractive to soft tissue engineering and possess atom neutral chemistries attractive for post gelation patterning in the presence or absence of cells.

Dextran-based hydrogel formed by thiol-Michael addition reaction for 3D cell encapsulation

“…Hydrogel, a representative soft and wet biomaterial with tunable properties mimicing native extracellular matrix (ECM), such as high water content, excellent mass transportation and tissue-like elasticity [15,16], is one of the most promising soft biomaterials for 3D cell encapsulation [12,17,18]. Various hydrogels have been used for 3D cell encapsulation, including natural-derived hydrogels (e.g., Matrigel TM [19], collagen [20,21], and fibrin [22]), as well as synthetic hydrogels (e.g., polyethylene glycol (PEG) [23][24][25][26][27], polyvinyl alcohol (PVA) [28], and polyhydroxyethyl methacrylate (PHEMA) [29]).…”

Spatiotemporal Modification of Stimuli-Responsive Hyaluronic Acid/Poly(N-isopropylacrylamide) Hydrogels

“…To spatiotemporally add in functionality, photopatterned thiol-ene reactions are attractive methods as these light induced click chemistries are highly specific and cytocompatible. 17,18,19 Both allylic ethers and norbornene functionalities have been reacted with dithiol terminated crosslinkers to yield spatiotemporally modifiable natural and artificial hydrogel matrices. 8,9,18,20 Spatiotemporal modifiable systems are just one aspect towards creating hydrogels with biologically relevant properties as the materials must also respond to stimuli.…”

“…Many cellular activities such as stem cell spreading, proliferation, and differentiation are influenced by the mechanical properties of the extracellular matrix or substrate. 51,52,53,54,55,56,57 As an example, human mesenchymal stem cells (hMSCs) cultured within an polyethylene glycol (PEG)-Silica 3D hydrogel, differentiated into neurons at lower modulus (7 kPa), while at a higher modulus (25 kPa) underwent myogenic differentiation. 58 Additionally, living tissues have different moduli, due to their different functions, that varies from 0.5-1.5 kPa for fat or bone marrow to several thousand kPa for cartilage and bone.…”

Rationally Designed Dynamic Protein Hydrogels with Reversibly Tunable Mechanical Properties

“…Previous methods of engineering dynamic polymer hydrogels with tunable mechanical properties have focused on varying the crosslinking density of hydrogels via chemical or physical means. [ 6,[11][12][13][14][15][16][17][18][19][20][21]25 ] Here, we engineer dynamic protein hydrogels using protein foldingunfolding in a controlled fashion to control the effective chain length between crosslinks, thus controlling the Young's modulus of these hydrogels. Folding and unfolding is the ultimate conformational change within proteins.…”

“…[ 6 ] Progress in polymer synthesis has led to novel approaches towards engineering polymerbased hydrogels with mechanical properties that are responsive to external stimuli, such as ligand, light, heat and pH. [11][12][13][14][15][16][17][18][19][20][21] For example, engineered polymer hydrogels can increase or decrease their Young's modulus via photo-mediated crosslinking or photolytic reactions. [ 13,22 ] Despite these advances, designing protein-based dynamic hydrogels with tunable mechanical properties have been challenging.…”