Enzyme-Induced Transition of the Morphology of Polyelectrolyte Complexes

TL;DR

This paper shows how enzymes can change the structure and properties of solid polyelectrolyte complexes, depending on the length of the polycation used.

Contribution

The study reveals how cellulase enzyme activity and polycation length jointly control structural and mechanical transitions in solid PECs.

Findings

Short PDADMAC/CMC complexes became liquid-like with increased enzyme dose and time.

Long PDADMAC complexes showed a transient turbidity increase and formed droplet-like phases.

Rheology showed dose- and time-dependent softening, with long PDADMAC remaining more elastic.

Abstract

Polyelectrolyte complexes
(PECs) can exist as liquid
coacervates
or solid precipitates with triggers such as salt, pH, or temperature
driving transitions. However, it is unclear how enzymatic chain scission
reorganizes solid PECs and alters their mechanics. We probed cellulase-mediated
remodeling of solid PECs formed from carboxymethyl cellulose (CMC)
and short or long poly­(diallyldimethylammonium chloride) (PDADMAC).
Turbidity and microscopy showed that short PDADMAC/CMC complexes decreased
in turbidity and became liquid-like as enzyme dose and time increased.
In contrast, long PDADMAC complexes exhibited a transient turbidity
increase at high cellulase concentration and formed droplet-like phases
consistent with competing PDADMAC/cellulase coacervation. Zeta potential
supported cellulase binding to PDADMAC, which reduced the positive
charge available for CMC bridging. Rheology showed dose- and time-dependent
softening, while long PDADMAC remained more elastic and relaxed more
slowly. Thus, the enzyme dose and polycation length jointly control
the kinetics of coupled structural and mechanical transitions in solid
PECs.

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