Stimuli-responsive polypeptide nanogels loaded with α1-antitrypsin for inhibition of inflammatory mediator trypsin

A new type of hydrophilic, biocompatible, and biodegradable polypeptide nanogel depots loaded with natural serine protease inhibitor α1-antitrypsin (AAT) was applied for inhibition of inflammatory mediator trypsin. Further, poly[N5-(2-hydroxyethyl)-L-glutamine-ran-N5-propargyl-L-glutamine-ran-N5-(6-aminohexyl)-L-glutamine]-ran-N5-[2-(4-hydroxyphenyl)ethyl)-L-glutamine] (PHEG-Tyr) and Nα-L-Lysine-grafted α,β-poly[(2-propyne)-D,L-aspartamide-ran-(2-hydroxyethyl)-DL-aspartamide-ran-(2-(4-hydroxyphenyl)ethyl)-DL-aspartamide] (Nα-Lys-NG) nanogels were prepared by HRP/H2O2-mediated crosslinking in inverse miniemulsions with pH and temperature-stimuli responsive behavior confirmed by dynamic light scattering and zeta potential measurements. The loading capacity of PHEG-Tyr and Nα-Lys-NG nanogels and their release profiles were firstly optimized with bovine serum albumin (BSA) and then used for loading and release of AAT. PHEG-Tyr and Nα-Lys-NG nanogels showed different loading capacities for AAT with the maximum (20 %) achieved with Nα-Lys-NG nanogel. In both cases, the nanogels depots demonstrated a burst release of AAT during 6 h, which could be favorable for quick inhibition of trypsin. A consequent pilot in vitro inhibition study revealed that both PHEG-Tyr and Nα-Lys-NG nanogels loaded with AAT successfully inhibited the enzymatic activity of trypsin. Furthermore, the inhibitory efficiency of the AAT-loaded nanogels was higher than that of AAT itself, indicating that the negatively charged polypeptide nanogels enhance the inhibitory function of AAT loaded in the nanogel depots.