From Cellular Organization to Synthetic Platforms: Liquid–Liquid Phase Separation as a Framework for Functional Biomolecular Condensates

Liquid-liquid phase separation (LLPS) is a fundamental biophysical process driving the formation of dynamic biomolecular condensates, which spatially organize cellular biochemistry without membrane delimitation. These condensates arise from multivalent, weak interactions among intrinsically disordered proteins, modular interaction motifs, and RNA scaffolds, enabling highly tunable and reversible compartmentalization of biomolecules. This phase behavior regulates critical cellular functions such as gene expression, signal transduction, and stress response, while its dysregulation contributes to pathological aggregation and disease. Recent advances leverage LLPS principles to design synthetic condensates with controllable composition, properties, and activities. Combining structural insights, quantitative phase behavior, and synthetic biology tools, engineered condensates have been developed for enhanced catalysis, metabolic control, targeted drug delivery, and biosensing. This review summarizes the molecular mechanisms, design strategies, and translational prospects of LLPS-mediated condensates, thereby paving the way for future exploration at the interface of cellular biophysics and bioengineering.