Embedding of Active Proteins and Living Cells in Redox‐Sensitive Hydrogels and Nanogels through Enzymatic Cross‐Linking

Abstract

Horseradish peroxidase (HRP) can be used for the enzymatic cross‐linking of thiol‐functionalized polymers under mild conditions to form hydrogels and nanogels without the need for added H2O2. Cells can be embedded in the hydrogels and proteins can be entrapped and released from the nanogels. These gels are fully degradable under mild and cytocompatible reductive conditions.

Enhanced tissue adhesiveness of injectable gelatin hydrogels through dual catalytic activity of horseradish peroxidase

“…[6] The conformation of the disulfide bonds in GH/GS hydrogels was determined using FTIR spectroscopy; the appearance of a peak m 5 500-540 (w) showed the S-S stretching vibrations ( Figure 3B). …”

“…Thus, this enhancement was due to the addition of thiol groups, which can form disulfide bonds in the presence of H 2 O 2 or under aerobic conditions with the catalysis of HRP. [6] Furthermore, the additional formation of disulfide bonds alternating with phenol-phenol in the GH/ GS hydrogel system was demonstrated obviously by the fact that amount of H 2 O 2 consumed by the GH/GS hydrogels was directly proportional to the thiol content. When the H 2 O 2 concentration was increased from 0.015% to 0.045%, the elastic modulus of GH5/GS1 hydrogels containing 1 wt% thiolated gelatin increased to maximum value of 6.5 kPa and then decreased to 5.7 kPa ( Figure 6B).…”

“…However, the velocity of the reactions is too slow, from several hours to days, and this restricts the application of thiomers in processes such as inhomogeneous cell/drug/protein/growth factor distribution. [6] study on the enhancement of HRP-catalyzed thiomer hydrogelation using phenolic compounds. [8] They hypothesized that phenol radical polymerization could decrease the gelation time of HRP-catalyzed thiol oxidation.…”

Enzymatically Cross-Linked Hyperbranched Polyglycerol Hydrogels as Scaffolds for Living Cells

“…Although the round-shaped cell morphology (Figure 3b) indicates that L929 cells could not adhere to the surface due to the nonfouling characteristics of the gels, 54−61 cellular viability was not affected during the time of observation, which is in good accord with the published data of other polyglycerol gels. 8,57 The mechanism of protein/cell nonfouling effect has not been fully understood until now, but some empiric data indicate that the surface hydrophilicity plays an important role. 58−61 Interestingly, the Cooper-White group recently invented a simple method to enhance cell adhesion on the cell nonfouling PEG gels by incorporating a peptide fragment of fibronectin (Fn), a protein known to enhance cell adhesion.…”

Introduction to In Situ Forming Hydrogels for Biomedical Applications

“…1 There has been an increased interest in the enzymatically crosslinked hydrogels that shows few side reactions since their high specificity for substrates. Horseradish peroxidase (HRP)/hydrogen peroxide (H 2 O 2 ), transglutaminase (TG), phosphatase (PP), tyrosinase, or thermolysin catalyzed crosslinking provides in situ hydrogel formation of hydroxyphenyl propionic acid (HPA) functionalized 8-arm PEG [42], thiol functionalized poly(glycidol) [43], Tetronic-tyramine (Tet-TA)/gelatin-HPA (GFPA) [44], dextran-tyramine (Dex-TA) [45], alginate-g-pyrrole [46], or protein polymers containing either lysine or glutamine [47]. These enzymatic crosslinks provide fast gelation.…”