Stable Coacervate Microdroplets as Robust Microreactors for Enhanced Enzymatic Catalysis

Membraneless organelles formed through liquid-liquid phase separation (LLPS) regulate cellular functions by creating dynamic compartments that enhance rates of biochemical reactions. Inspired by these natural systems, coacervate microdroplets serve as biomimetic platforms to study LLPS mechanisms and develop functional materials. However, the inherent instability of coacervate microdroplets limits their long-term applications. Herein, we develop highly stable coacervate microdroplets with dynamic molecular recruitment capabilities, serving as efficient enzymatic microreactors. Coacervate microdroplets are constructed from polyethyleneimine (PEI) and sodium thioctate (ST), driven by electrostatic interactions between amino groups of PEI and carboxyl groups of ST, along with hydrophobic interaction from the dithiolane ring of ST. Charge repulsion between positively charged coacervate microdroplets prevents their coalescence and fusion, ensuring their structural integrity for over 35 days without additional stabilizers. These exhibit exceptional recruitment efficiency of small molecules, polymers, and proteins. Their good stability and molecular recruitment capabilities highlight their general applicability as robust and versatile microreactors for a broad range of enzymatic reactions with up to a 53-fold acceleration in esterase-catalyzed hydrolysis of 4-nitrophenyl acetate (NPA). Our findings provide new insights into stabilization mechanisms of coacervate microdroplets and offer a stable and scalable platform for biomimetic catalysis and synthetic biology.