Stable Coacervate Microdroplets as Robust Microreactors for Enhanced Enzymatic Catalysis

Why It Matters

The breakthrough provides a durable, additive‑free platform for high‑efficiency enzymatic reactions, enabling scalable synthetic‑biology applications and reducing costs associated with microreactor stabilization.

Key Takeaways

• PEI/ST coacervates remain stable over 35 days.
• No additives needed for long-term structural integrity.
• Recruit small molecules, polymers, and proteins efficiently.
• Enable up to 53‑fold increase in esterase activity.
• Offer scalable microreactors for synthetic biology applications.

Pulse Analysis

Liquid‑liquid phase separation (LLPS) underpins many cellular processes by forming membraneless organelles that concentrate reactants and accelerate biochemistry. Translating this principle to engineered systems has been hampered by the fleeting nature of synthetic coacervates, which often merge or dissolve within hours. The new PEI‑ST coacervate design tackles this limitation head‑on, leveraging strong electrostatic binding between PEI’s amine groups and ST’s carboxylates, complemented by hydrophobic interactions from ST’s dithiolane ring. This dual‑mode binding generates a positively charged surface that repels neighboring droplets, preventing coalescence and preserving droplet morphology for weeks.

Beyond stability, the PEI‑ST droplets excel at molecular recruitment. Their charged interior and hydrophobic pockets draw in a diverse array of substrates—from low‑molecular‑weight dyes to high‑molecular‑weight polymers and functional proteins—without compromising droplet integrity. This versatility creates a microenvironment where enzymes operate at concentrations far exceeding bulk solution, effectively mimicking natural organelles. In proof‑of‑concept experiments, an esterase housed within the droplets hydrolyzed 4‑nitrophenyl acetate up to 53 times faster than in free solution, illustrating the catalytic boost achievable through spatial confinement.

The implications for industry are substantial. Stable, additive‑free coacervate microreactors can be mass‑produced, integrated into flow‑chemistry platforms, or embedded in biosensors, reducing reliance on costly surfactants or polymer scaffolds. Their ability to accelerate enzymatic pathways opens avenues for greener manufacturing, high‑throughput screening, and synthetic biology circuits that require precise temporal control. As researchers refine droplet composition and explore multi‑enzyme cascades, this technology could redefine how biocatalysis is deployed at scale.