Programmatically Dynamic Microcompartmentation in Coacervate-in-Pickering Emulsion Protocell

Thermally-resilient, phase-invertible, ultra-stable all-aqueous compartments by pH-modulated protein colloidal particles

The essence of compartmentalization in cells is the inspiration behind the engineering of synthetic counterparts, which has emerged as a significant engineering theme. Here, we report the formation of ultra-stable water-in-water (W/W) emulsion droplets. These W/W droplets demonstrate previously unattained stability across a broad pH spectrum and exhibit resilience at temperatures up to 80℃, overcoming the challenge of insufficient robustness in dispersed droplets of aqueous two-phase systems (ATPS). The exceptional robustness is attributed to the strong anchoring of micelle-like casein colloidal particles at the PEO/DEX interface, which maintains stability under varying environmental conditions. The increased surface hydrophobicity of these particles at high temperatures contributes to the formation of thermally-stable droplets, enduring temperatures as high as 80℃. Furthermore, our study illustrates the adaptable affinity of micelle-like casein colloidal particles towards the PEO/DEX-rich phase, enabling the formation of stable DEX-in-PEO emulsions at lower pH levels, and PEO-in-DEX emulsions as the pH rises above the isoelectric point. The robust nature of these W/W emulsions unlocks new possibilities for exploring various biochemical reactions within synthetic subcellular modules and lays a solid foundation for the development of novel biomimetic materials.

Matching Together Living Cells and Prototissues: Will There Be Chemistry?

Scientific advancements in bottom-up synthetic biology have led to the development of numerous models of synthetic cells, or protocells. To date, research has mainly focused on increasing the (bio)chemical complexity of these bioinspired micro-compartmentalized systems, yet the successful integration of protocells with living cells remains one of the major challenges in bottom-up synthetic biology. In this review, we aim to summarize the current state of the art in hybrid protocell/living cell and prototissue/living cell systems. Inspired by recent breakthroughs in tissue engineering, we review the chemical, bio-chemical, and mechano-chemical aspects that hold promise for achieving an effective integration of non-living and living matter. The future production of fully integrated protocell/living cell systems and increasingly complex prototissue/living tissue systems not only has the potential to revolutionize the field of tissue engineering, but also paves the way for new technologies in (bio)sensing, personalized therapy, and drug delivery.

Hierarchical Structuration in Protocellular System

Spatial control is one of the ubiquitous features in biological systems and the key to the functional complexity of living cells. The strategies to achieve such precise spatial control in protocellular systems are crucial to constructing complex artificial living systems with functional collective behavior. Herein, the authors review recent advances in the spatial control within a single protocell or between different protocells and discuss how such hierarchical structured protocellular system can be used to understand complex living systems or to advance the development of functional microreactors with the programmable release of various biomacromolecular payloads, or smart protocell-biological cell hybrid system.

Coacervate Droplets for Synthetic Cells

The design and construction of synthetic cells - human-made microcompartments that mimic features of living cells - have experienced a real boom in the past decade. While many efforts have been geared toward assembling membrane-bounded compartments, coacervate droplets produced by liquid-liquid phase separation have emerged as an alternative membrane-free compartmentalization paradigm. Here, the dual role of coacervate droplets in synthetic cell research is discussed: encapsulated within membrane-enclosed compartments, coacervates act as surrogates of membraneless organelles ubiquitously found in living cells; alternatively, they can be viewed as crowded cytosol-like chassis for constructing integrated synthetic cells. After introducing key concepts of coacervation and illustrating the chemical diversity of coacervate systems, their physicochemical properties and resulting bioinspired functions are emphasized. Moving from suspensions of free floating coacervates, the two nascent roles of these droplets in synthetic cell research are highlighted: organelle-like modules and cytosol-like templates. Building the discussion on recent studies from the literature, the potential of coacervate droplets to assemble integrated synthetic cells capable of multiple life-inspired functions is showcased. Future challenges that are still to be tackled in the field are finally discussed.