The current work presents a pivotal study of the nanogelation of the linear poly(N5‐2‐hydroxypropyl‐L‐glutamine) polymer precursor containing tyramine (TYR) units in an inverse miniemulsion by horseradish peroxidase/H2O2‐mediated crosslinking. The effects of various nH2O2/nTYR ratios on the kinetics of nanogelation in the inverse miniemulsion and on the reaction time are investigated by linear sweep voltammetry, while the formation of dityramine crosslinking is explored by fluorescence spectroscopy. The study is completed using dynamic light scattering measurements, nanoparticle tracking analysis, and cryogenic transmission electron microscopy to acquire comprehensive information about the formed nanoparticulate systems. With the optimal ratio nH2O2/nTYR = 2, the strategy yields in the high‐quality ~ 130 nm poly(amino acid)‐based nanogel, which is prepared in 2 h. The nanogel is colloidally stable under different temperature and pH conditions for over 168 h. Moreover, the demonstrated nanogel is noncytotoxic for HeLa cells and human primary fibroblasts and is quickly enzymatically hydrolyzed into small fragments during a biodegradation study in human blood plasma. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48725.

Injectable hydrogel scaffolds combined with stem cell therapy represent a promising approach for minimally invasive surgical tissue repair. In this study, we developed and characterized a fully synthetic, biodegradable poly(N 5 -(2-hydroxyethyl)-L-glutamine)-based injectable hydrogel modified with integrin-binding arginine−glycine−aspartic acid (RGD) peptide (PHEG-Tyr-RGD). The biodegradable hydroxyphenyl polymer precursor derivative of PHEG-Tyr was enzymatically cross-linked to obtain injectable hydrogels with different physicochemical properties. The gelation time, gel yield, swelling behavior, and storage modulus of the PHEG-Tyr hydrogels were tuned by varying the concentrations of the PHEG-Tyr precursors and horseradish peroxidase as well as the n H 2 O 2 /n Tyr ratio. The mechanical properties and gelation time of the PHEG-Tyr hydrogel were optimized for the encapsulation of rat mesenchymal stem cells (rMSCs). We focused on the 2D and 3D spreading and viability of rMSCs within the PHEG-Tyr-RGD hydrogels with different physicochemical microenvironments in vitro. Encapsulation of rMSCs shows long-term survival and exhibits cell−matrix and cell−cell interactions reflective of both the RGD concentration and hydrogel stiffness. The presented biomaterial represents a suitable biological microenvironment to guide 3D spreading and may act as a promising 3D artificial extracellular matrix for stem cell therapy.

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