Factors Affecting Enzymatic Degradation of Microgel-Bound Peptides

Abstract

Proteolytic degradation and release of microgel-bound peptides was investigated for trypsin, poly(acrylic acid-co-acrylamide) microgels (70-90 μm in diameter), and oppositely charged polylysine, using a method combination of confocal microscopy and micromanipulator-assisted light microscopy. Results show that trypsin-induced release of polylysine increased with increasing trypsin concentration, decreasing microgel charge density and decreasing peptide molecular weight. While the microgel offered good protection against enzymatic degradation at high microgel charge density, it was also observed that the cationic peptide enabled trypsin to bind throughout the peptide-loaded microgels, even when it did not bind to the peptide-void ones. With the exception of highly charged microgels, proteolytic degradation throughout the peptide-loaded microgel resulted in the generation of short and non-adsorbing peptide stretches, giving rise to the concentration and peptide length dependence observed. A simple random scission model was able to qualitatively capture these experimental findings. Collectively, the results demonstrate that microgel charge density, peptide molecular weight, and enzyme concentration greatly influence degradation/release of microgel-bound peptides and need to be considered in the use of microgels, e.g., as carriers for protein and peptide drugs.

Factors Affecting Peptide Interactions with Surface-Bound Microgels

“…9 The controlled use of microgels as delivery systems for peptide and protein drugs requires a basic understanding of the factors determining peptide/protein loading into, distribution within, and release from, microgels, and how these effects can be controlled by various design elements and external conditions. For microgel dispersions, there have been an increasing number of mechanistic studies dedicated to the effect of microgel properties, e.g., charge 10 and cross-linking density 11 , as well as of peptide properties, such as molecular weight 12 , charge (distribution) 10 , secondary structure 13 , and hydrophobicity 14 , including also effects of biodegradation of both the peptide 15 and microgel network 16 . For surface-bound microgels, on the other hand, there is very limited prior work done in this context.…”

Covalent immobilization of trypsin onto thermo‐sensitive poly(N‐isopropylacrylamide‐co‐acrylic acid) microspheres with high activity and stability

“…As seen in Figure (b), the zeta potentials of the microspheres without enzyme increased with pH value until a plateau region was reached around pH 7.0. It was known that the value of pK a for AA was at 4–5, so most of carboxyl groups on the microspheres were dissociated at pH 7.0. The isoelectric point (pI) value of trypsin was 10.8, and the trypsin molecules were positively charged when pH was lower than its pI value.…”

Microgels at fluid-fluid interfaces for food and drinks

“…Similarly, there are many studies investigating microgel absorption into gels or release from them (Yaroslavov et al, 2017), plus adsorption of biopolymers and bioactive compounds onto (Kumar and Singh, 2010), (Kureha et al, 2017), (Liu et al, 2014), (Morisada et al, 2010) and absorption into microgels, such as enzymes (Sigolaeva et al, 2014, Sigolaeva et al, 2015, betacarotene (Tan et al, 2014) and DNA (Ozdemir et al, 2006), including the interaction of microgels and their payloads with membranes (Nordstrom et al, 2018); (Mihut et al, 2013) and cells (Vihola et al, 2007). Of particular importance to foods is the ease of enzymatic digestion of materials encapsulated within the microgel particles (Mansson et al, 2013), (Torres et al, 2016). Such studies are not comprehensively reviewed here, but rather aspects of the direct interaction of microgels with fluid-fluid interfaces in general, principally air-water (A-W), oil-water (O-W) and their effects of bubble(foam) and emulsion stability, respectively.…”