Viscosity and interfacial properties in a mussel-inspired adhesive coacervate

Abstract

The chemistry of mussel adhesion has commanded the focus of much recent research activity on wet adhesion. By comparison, the equally critical adhesive processing by marine organisms has been little examined. Using a mussel-inspired coacervate formed by mixing a recombinant mussel adhesive protein (fp-151-RGD) with hyaluronic acid (HA), we have examined the nanostructure, viscosity, friction, and interfacial energy of fluid-fluid phase-separated coacervates using the surface forces apparatus and microscopic techniques. At mixing ratios of fp-151-RGD:HA resulting in marginal coacervation, the coacervates showed shear-thickening viscosity and no structure by cryo-transmission electron microscopy (cryo-TEM). However, at the mixing ratio producing maximum coacervation, the coacervate showed shear-thinning viscosity and a transition to a bicontinuous phase by cryo-TEM. The shear-thinning viscosity, high friction coefficient (>1.2), and low interfacial energy (<1 mJ m−2) observed at the optimal mixing ratio for coacervation are promising delivery, spreading and adhesion properties for future wet adhesive and coating technologies.

Infiltration of chitin by protein coacervates defines the squid beak mechanical gradient

“…Coacervates are implicated in the processing of other marine biomaterials, for example, mussel threads 27 and sandcastle worm cement 38 . The properties of coacervates 39 include high polymer concentration, relatively low viscosity, very low interfacial energy and shear-thinning behavior 40 . These characteristics make coacervates an ideal modality for spontaneous spreading and wicking of concentrated proteins into a nanoporous network.…”

PRISM-Based Theory of Complex Coacervation: Excluded Volume versus Chain Correlation

“…Experimentalists have begun to systematically explore this space, looking at effects such as chain solubility and length, ion identity, and valency. 1,32,[34][35][36][37][38][47][48][49][50][51] Nevertheless, a comprehensive physical picture of these systems remains to be elucidated.…”

“…[27][28][29][30] This recent activity in the field is concomitant with a desire to emulate the molecular features observed in a number of biological materials, such as underwater adhesives in mussels and the matrix adhesive holding together the dwelling of a sandcastle worm. 2,[31][32][33] The novelty of these materials is their extreme stability (yet responsiveness) with respect to environmental ionic conditions, even at high salt concentrations, as well as their reversible assembly behavior. [34][35][36][37][38] Complex coacervates are used for microencapsulation, drug delivery, 3,19 biomaterials, [39][40][41] and underwater adhesives, 2,31,32 where their self assembly and functionality relies 19,[23][24][25][26] on the relationship between charged species.…”

“…1 Polymeric complex coacervates demonstrate a rich phenomenology that is a function of the presence of salt as well as the nature of the charged polyions, 1,32,[34][35][36][37][38][47][48][49][50] with a vast parameter space that spans the molecular features of all four components. Experimentalists have begun to systematically explore this space, looking at effects such as chain solubility and length, ion identity, and valency.…”

Linear viscoelasticity of complex coacervates

“…Complex coacervates have a long history of use in the food [5][6][7][8][9][10][11][12][13] and personal care [14,15] industries, and have found increasing utility as a platform for drug and gene delivery [1][2][3][4], as well as underwater adhesives [5][6][7][8][9][10][11][12][13][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62]. Coacervation has also recently been implicated in the formation of various biological assemblies [1,[14][15][16]55,[63][64][65][66][67][68][69]…”