Coacervate protein carriers with application-dependent stability and delivery properties 

Complex coacervate core micelles (C3Ms) is a simple method to encapsulate protein: only by mixing the protein solution with an oppositely charged neutral-ionic diblock copolymer solution at stoichiometric charge ratio. However, protein-containing C3Ms has low salt stability and high exchange dynamics that limit its applications. This project investigates some strategies address these challenges. The obtained results will contribute to the design of C3M protein carriers of which the stability and dynamics can be tuned to specific applications.


Protein encapsulation using complex coacervate core micelles (C3Ms) method is easy to prepare and has high encapsulation efficiency. This protein encapsulation is generated by mixing the protein solution with an oppositely charged neutral-ionic diblock copolymer solution at stoichiometric charge ratio. Despite the many advantages of C3Ms to encapsulate protein, it has significant drawbacks that the micelles is easy disintegrate at high salt concentration and has high dynamics between micelles and solution that relate to packing stability of the protein and the level of protection offered by C3Ms as carriers for protein encapsulation.

Aim of the project

This project investigates some strategies to improve salt stability and decrease the exchange dynamics of protein-containing C3Ms. The strategies that we investigate on this project are three-component C3Ms, add extra charge to the enzyme by genetic engineering and by bioconjugation, and covalent crosslinking of the core of the C3Ms. We observed the formation and salt stability of enzyme-containing C3Ms by using fluorescence correlation spectroscopy (FCS) and dynamic light scattering (DLS). We observed the dynamic exchange using Förster Resonance Energy Transfer (FRET).


We report on the encapsulation of our protein model, the spore coat protein A (CotA) laccase,  into complex coacervate core micelles (C3Ms) using positive diblock copolymer, poly(N-methyl-2-vinyl-pyridinium iodide)-block-poly(ethylene oxide) (P2MVP128-b-PEO477) 

For three-component C3Ms we added the negatively charged homopolymer poly(4-styrene sulfonate) (PSS215). In the three components C3M, DLS showed improved stability of the three-component C3M system against salt addition compared to the two-component system. However, FCS showed that CotA is excluded from the C3Ms already at lower ionic strengths. We observed more stable protein-containing C3Ms using bioconjugation, genetic engineering, and crosslink strategies. 


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