Stimuli-responsive polypeptide nanogels for trypsin inhibition

A new type of hydrophilic, biocompatible, and biodegradable polypeptide nanogel depots loaded with the natural serine protease inhibitor alpha(1)-antitrypsin (AAT) was applied for the inhibition of the inflammatory mediator trypsin. Two types of nanogels were prepared from linear synthetic polypeptides based on biocompatible and biodegradable poly[N-5-(2-hydroxyethyl)-L-glutamine-ran-N-5-propargyl-L-glutamine-ran-N-5-(6-aminohexyl)-L-glutamine]-ran-N-5-[2-(4-hydroxyphenypethyl)-L-glutamine] (PHEG-Tyr) or biocompatible N-alpha-L-lysine-grafted alpha,beta-poly[(2-propyne)-D,L-aspartamide-ran-(2-hydroxyethyl)-DL-aspartamide-ran-(2-(4-hydroxyphenyl)ethyl)-DL-aspartamide] (N-alpha-Lys-NG). Both 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 N-alpha-Lys-NG nanogels and their release profiles were first optimized with bovine serum albumin. The nanogels were then used for loading and release of AAT. PHEG-Tyr and N-alpha-Lys-NG nanogels showed different loading capacities for AAT with the maximum (20%) achieved with N-alpha-Lys-NG nanogel. In both cases, the nanogel depots demonstrated a burst release of AAT during the first 6 h, which could be favorable for quick inhibition of trypsin. A consequent pilot in vitro inhibition study revealed that both PHEG-Tyr and N-alpha-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 only AAT. Interestingly, also non-loaded PHEG-Tyr and N-alpha-Lys-NG nanogels were shown to effectively inhibit trypsin because they contain suitable amino acids in their structures that effectively block the active site of trypsin.

Automated summary

This study presents a new type of polypeptide nanogel depots that are hydrophilic, biocompatible, and biodegradable, and can inhibit the activity of trypsin, which is an inflammatory mediator. The nanogels were successfully loaded with the natural serine protease inhibitor alpha(1)-antitrypsin (AAT) and showed high inhibitory efficiency in vitro.