Bulk Self-Assembly of Giant, Unilamellar Vesicles

Cyclophospholipids Enable a Protocellular Life Cycle

There is currently no plausible path for the emergence of a self-replicating protocell, because prevalent formulations of model protocells are built with fatty acid vesicles that cannot withstand the concentrations of Mg2+ needed for the function and replication of nucleic acids. Although prebiotic chelates increase the survivability of fatty acid vesicles, the resulting model protocells are incapable of growth and division. Here, we show that protocells made of mixtures of cyclophospholipids and fatty acids can grow and divide in the presence of Mg2+-citrate. Importantly, these protocells retain encapsulated nucleic acids during growth and division, can acquire nucleotides from their surroundings, and are compatible with the nonenzymatic extension of an RNA oligonucleotide, chemistry needed for the replication of a primitive genome. Our work shows that prebiotically plausible mixtures of lipids form protocells that are active under the conditions necessary for the emergence of Darwinian evolution.

Lipid Exchange Promotes Fusion of Model Protocells

Vesicle fusion is an important process underlying cell division, transport, and membrane trafficking. In phospholipid systems, a range of fusogens including divalent cations and depletants have been shown to induce adhesion, hemifusion, and then full content fusion between vesicles. This work shows that these fusogens do not perform the same function for fatty acid vesicles, which are used as model protocells (primitive cells). Even when fatty acid vesicles appear adhered or hemifused to each other, the intervening barriers between vesicles do not rupture. This difference is likely because fatty acids have a single aliphatic tail, and are more dynamic than their phospholipid counterparts. To address this, it is postulated that fusion could instead occur under conditions, such as lipid exchange, that disrupt lipid packing. Using both experiments and molecular dynamics simulations, it is verified that fusion in fatty acid systems can indeed be induced by lipid exchange. These results begin to probe how membrane biophysics could constrain the evolutionary dynamics of protocells.

Passive endocytosis in model protocells

Semipermeable membranes are a key feature of all living organisms. While specialized membrane transporters in cells can import otherwise impermeable nutrients, the earliest cells would have lacked a mechanism to import nutrients rapidly under nutrient-rich circumstances. Using both experiments and simulations, we find that a process akin to passive endocytosis can be recreated in model primitive cells. Molecules that are too impermeable to be absorbed can be taken up in a matter of seconds in an endocytic vesicle. The internalized cargo can then be slowly released over hours, into the main lumen or putative cytoplasm. This work demonstrates a way by which primitive life could have broken the symmetry of passive permeation prior to the evolution of protein transporters.

Passive endocytosis in model protocells

Semipermeable membranes are a key feature of all living organisms. While specialized membrane transporters in cells can import otherwise impermeable nutrients, the earliest cells would have lacked a mechanism to import nutrients rapidly under nutrient-rich circumstances. Using both experiments and simulations, we find that a process akin to passive endocytosis can be recreated in model primitive cells. Molecules that are too impermeable to be absorbed can be taken up in a matter of seconds in an endocytic vesicle. The internalized cargo can then be slowly released over hours, into the main lumen or putative cytoplasm. This work demonstrates a way by which primitive life could have broken the symmetry of passive permeation prior to the evolution of protein transporters.

Recent Advances in Nanoparticle Development for Drug Delivery: A Comprehensive Review of Polycaprolactone-Based Multi-Arm Architectures

Controlled drug delivery is a crucial area of study for improving the targeted availability of drugs; several polymer systems have been applied for the formulation of drug delivery vehicles, including linear amphiphilic block copolymers, but with some limitations manifested in their ability to form only nanoaggregates such as polymersomes or vesicles within a narrow range of hydrophobic/hydrophilic balance, which can be problematic. For this, multi-arm architecture has emerged as an efficient alternative that overcame these challenges, with many interesting advantages such as reducing critical micellar concentrations, producing smaller particles, allowing for various functional compositions, and ensuring prolonged and continuous drug release. This review focuses on examining the key variables that influence the customization of multi-arm architecture assemblies based on polycaprolactone and their impact on drug loading and delivery. Specifically, this study focuses on the investigation of the structure-property relationships in these formulations, including the thermal properties presented by this architecture. Furthermore, this work will emphasize the importance of the type of architecture, chain topology, self-assembly parameters, and comparison between multi-arm structures and linear counterparts in relation to their impact on their performance as nanocarriers. By understanding these relationships, more effective multi-arm polymers can be designed with appropriate characteristics for their intended applications.

Colony-like Protocell Superstructures

We report the formation, growth, and dynamics of model protocell superstructures on solid surfaces, resembling single cell colonies. These structures, consisting of several layers of lipidic compartments enveloped in a dome-shaped outer lipid bilayer, emerged as a result of spontaneous shape transformation of lipid agglomerates deposited on thin film aluminum surfaces. Collective protocell structures were observed to be mechanically more stable compared to isolated spherical compartments. We show that the model colonies encapsulate DNA and accommodate nonenzymatic, strand displacement DNA reactions. The membrane envelope is able to disassemble and expose individual daughter protocells, which can migrate and attach via nanotethers to distant surface locations, while maintaining their encapsulated contents. Some colonies feature "exocompartments", which spontaneously extend out of the enveloping bilayer, internalize DNA, and merge again with the superstructure. A continuum elastohydrodynamic theory that we developed suggests that a plausible driving force behind subcompartment formation is attractive van der Waals (vdW) interactions between the membrane and surface. The balance between membrane bending and vdW interactions yields a critical length scale of 236 nm, above which the membrane invaginations can form subcompartments. The findings support our hypotheses that in extension of the "lipid world hypothesis", protocells may have existed in the form of colonies, potentially benefiting from the increased mechanical stability provided by a superstructure.

Preparation of Giant Vesicles with Mixed Single-Tailed and Double-Tailed Lipids

Giant vesicles are model membrane systems that can be characterized with microscopy. Whereas most giant synthetic vesicles are created with a single phospholipid species, vesicles with mixed membrane compositions, including single-tailed and double-tailed lipids, serve as more accurate models of biological membranes and also have applications in the origins of life and drug delivery fields. Here we describe several approaches that can be used to create giant vesicles with mixed lipid compositions.

Self-Assembly of Glycerol-Amphiphilic Janus Dendrimers Amplifies and Indicates Principles for the Selection of Stereochemistry by Biological Membranes

The principles for the selection of the stereochemistry of phospholipids of biological membranes remain unclear and continue to be debated. Therefore, any new experiments on this topic may help progress in this field. To address this question, three libraries of constitutional isomeric glycerol-amphiphilic Janus dendrimers (JDs) with nonsymmetric homochiral, racemic, and symmetric achiral branching points were synthesized by an orthogonal-modular-convergent methodology. These JDs amplify self-assembly, and therefore, monodisperse vesicles known as dendrimersomes (DSs) with predictable dimensions programmed by JD concentration were assembled by rapid injection of their ethanol solution into water. DSs of homochiral JD enantiomers, racemic, including mixtures of different enantiomers, and achiral exhibited similar DS size-concentration dependence. However, the number of bilayers of DSs assembled from homochiral, achiral, and racemic JDs determined by cryo-TEM were different. Statistical analysis of the number of bilayers and coarse-grained molecular dynamics simulations demonstrated that homochiral JDs formed predominantly unilamellar DSs. Symmetric achiral JDs assembled only unilamellar DSs while racemic JDs favored multilamellar DSs. Since cell membranes are unilamellar, these results indicate a new rationale for nonsymmetric homochiral vs racemic selection. Simultaneously, these experiments imply that the symmetric achiral lipids forming more stable membrane, probably had been the preferable assemblies of prebiotic cell membranes.

Model Atmospheric Aerosols Convert to Vesicles upon Entry into Aqueous Solution

Aerosols are abundant on the Earth and likely played a role in prebiotic chemistry. Aerosol particles coagulate, divide, and sample a wide variety of conditions conducive to synthesis. While much work has centered on the generation of aerosols and their chemistry, little effort has been expended on their fate after settling. Here, using a laboratory model, we show that aqueous aerosols transform into cell-sized protocellular structures upon entry into aqueous solution containing lipid. Such processes provide for a heretofore unexplored pathway for the assembly of the building blocks of life from disparate geochemical regions within cell-like vesicles with a lipid bilayer in a manner that does not lead to dilution. The efficiency of aerosol to vesicle transformation is high with prebiotically plausible lipids, such as decanoic acid and decanol, that were previously shown to be capable of forming growing and dividing vesicles. The high transformation efficiency with 10-carbon lipids in landing solutions is consistent with the surface properties and dynamics of short-chain lipids. Similar processes may be operative today as fatty acids are common constituents of both contemporary aerosols and the sea. Our work highlights a new pathway that may have facilitated the emergence of the Earth's first cells.

Liposomes and liposome-like nanoparticles: From anti-fungal infection to the COVID-19 pandemic treatment

The liposome is the first nanomedicine transformed into the market and applied to human patients. Since then, such phospholipid bilayer vesicles have undergone technological advancements in delivering small molecular-weight compounds and biological drugs. Numerous investigations about liposome uses were conducted in different treatment fields, including anti-tumor, anti-fungal, anti-bacterial, and clinical analgesia, owing to liposome's ability to reduce drug cytotoxicity and improve the therapeutic efficacy and combinatorial delivery. In particular, two liposomal vaccines were approved in 2021 to combat COVID-19. Herein, the clinically used liposomes are reviewed by introducing various liposomal preparations in detail that are currently proceeding in the clinic or on the market. Finally, we discuss the challenges of developing liposomes and cutting-edge liposomal delivery for biological drugs and combination therapy.

Fast and Reversible Photoresponsive Self-Assembly Behavior of Rosin-Based Amphiphilic Polymers

Designing stimulus-responsive amphiphilic polymers with a fast photoresponsive self-assembly behavior remains a challenge. Two series of rosin-terminated and azobenzene-terminated amphiphilic polymers (PAM_n and PMA_n) with fast and reversible photoresponsive properties were prepared using rosin-based azobenzene groups and polyethylene glycol, respectively. Under 5-10 s of UV irradiation, the polymers showed trans-to-cis isomerization and reached a photosteady state. For the PAM_n polymer, the absorbance of the absorption peak at 325 nm recovered to more than 95% of the initial value under visible light for 5-10 s, whereas that of the PMA_n polymer recovered completely. Notably, the PAM_n and PMA_n polymers initially self-assembled to vesicles or spherical micelles, and various morphological changes were achieved by manipulating UV irradiation time, with the initial morphology again recovered under dark conditions or visible-light irradiation. Remarkably, vesicles of the PAM₃₄ and PMA₃₄ polymers presented an intermediate open-vesicle state before being completely deformed under UV irradiation because of the existence of a π-π interaction. Finally, the ability of PAM₃₄ and PMA₃₄ polymer vesicles to perform the controlled release and reversible loading of a fluorescent probe was evaluated.

Fatty Acids/Tetraphenylethylene Conjugates: Hybrid AIEgens for the Preparation of Peptide-Based Supramolecular Gels

Aggregation-induced emissive materials are gaining particular attention in the last decades due to their wide application in different fields, from optical devices to biomedicine. In this work, compounds having these kinds of properties, composed of tetraphenylethylene scaffold combined with fatty acids of different lengths, were synthesized and characterized. These molecules were found able to self-assemble into different supramolecular emissive structures depending on the chemical composition and water content. Furthermore, they were used as N-terminus capping agents in the development of peptide-based materials. The functionalization of a 5-mer laminin-derived peptide led to the obtainment of luminescent fibrillary materials that were not cytotoxic and were able to form supramolecular gels in aqueous environment.

Subtle changes in pH affect the packing and robustness of fatty acid bilayers

Connecting molecular interactions to emergent properties is a goal of physical chemistry, self-assembly, and soft matter science. We show that for fatty acid bilayers, vesicle rupture tension, and permeability to water and ions are coupled to pH via alterations to lipid packing. A change in pH of one, for example, can halve the rupture tension of oleic acid membranes, an effect that is comparable to increasing lipid unsaturation in phospholipid systems. We use both experiments and molecular dynamics simulations to reveal that a subtle increase in pH can lead to increased water penetration, ion permeability, pore formation rates, and membrane disorder. For changes in membrane water content, oleic acid membranes appear to be more than a million times more sensitive to protons than to sodium ions. The work has implications for systems in which fatty acids are likely to be found, for example in the primitive cells on early Earth, biological membranes especially during digestion, and other biomaterials.

Protocells: Milestones and Recent Advances

The origin of life is still one of humankind's great mysteries. At the transition between nonliving and living matter, protocells, initially featureless aggregates of abiotic matter, gain the structure and functions necessary to fulfill the criteria of life. Research addressing protocells as a central element in this transition is diverse and increasingly interdisciplinary. The authors review current protocell concepts and research directions, address milestones, challenges and existing hypotheses in the context of conditions on the early Earth, and provide a concise overview of current protocell research methods.

Synthesis of Phospholipids Under Plausible Prebiotic Conditions and Analogies with Phospholipid Biochemistry for Origin of Life Studies

Phospholipids are essential components of biological membranes and are involved in cell signalization, in several enzymatic reactions, and in energy metabolism. In addition, phospholipids represent an evolutionary and non-negligible step in life emergence. Progress in the past decades has led to a deeper understanding of these unique hydrophobic molecules and their most pertinent functions in cell biology. Today, a growing interest in "prebiotic lipidomics" calls for a new assessment of these relevant biomolecules.

Determining the "Biosignature Threshold" for Life Detection on Biotic, Abiotic, or Prebiotic Worlds

The field of prebiotic chemistry has demonstrated that complex organic chemical systems that exhibit various life-like properties can be produced abiotically in the laboratory. Understanding these chemical systems is important for astrobiology and life detection since we do not know the extent to which prebiotic chemistry might exist or have existed on other worlds. Nor do we know what signatures are diagnostic of an extant or "failed" prebiotic system. On Earth, biology has suppressed most abiotic organic chemistry and overprints geologic records of prebiotic chemistry; therefore, it is difficult to validate whether chemical signatures from future planetary missions are remnant or extant prebiotic systems. The "biosignature threshold" between whether a chemical signature is more likely to be produced by abiotic versus biotic chemistry on a given world could vary significantly, depending on the particular environment, and could change over time, especially if life were to emerge and diversify on that world. To interpret organic signatures detected during a planetary mission, we advocate for (1) gaining a more complete understanding of prebiotic/abiotic chemical possibilities in diverse planetary environments and (2) involving experimental prebiotic samples as analogues when generating comparison libraries for "life-detection" mission instruments.

Fabrication of Biomaterials and Biostructures Based On Microfluidic Manipulation

Biofabrication technologies are of importance for the construction of organ models and functional tissue replacements. Microfluidic manipulation, a promising biofabrication technique with micro-scale resolution, can not only help to realize the fabrication of specific microsized structures but also build biomimetic microenvironments for biofabricated tissues. Therefore, microfluidic manipulation has attracted attention from researchers in the manipulation of particles and cells, biochemical analysis, tissue engineering, disease diagnostics, and drug discovery. Herein, biofabrication based on microfluidic manipulation technology is reviewed. The application of microfluidic manipulation technology in the manufacturing of biomaterials and biostructures with different dimensions and the control of the microenvironment is summarized. Finally, current challenges are discussed and a prospect of microfluidic manipulation technology is given. The authors hope this review can provide an overview of microfluidic manipulation technologies used in biofabrication and thus steer the current efforts in this field.

Fluorescence Recovery after Photobleaching in Colloidal Science: Introduction and Application

FRAP (fluorescence recovery after photo bleaching) is a method for determining diffusion in material science. In industrial applications such as medications, foods, Medtech, hygiene, and textiles, the diffusion process has a substantial influence on the overall qualities of goods. All these complex and heterogeneous systems have diffusion-based processes at the local level. FRAP is a fluorescence-based approach for detecting diffusion; in this method, a high-intensity laser is made for a brief period and then applied to the samples, bleaching the fluorescent chemical inside the region, which is subsequently filled up by natural diffusion. This brief Review will focus on the existing research on employing FRAP to measure colloidal system heterogeneity and explore diffusion into complicated structures. This description of FRAP will be followed by a discussion of how FRAP is intended to be used in colloidal science. When constructing the current Review, the most recent publications were reviewed for this assessment. Because of the large number of FRAP articles in colloidal research, there is currently a dearth of knowledge regarding the growth of FRAP's significance to colloidal science. Colloids make up only 2% of FRAP papers, according to ISI Web of Knowledge.

Triggerable Protocell Capture in Nanoparticle-Caged Coacervate Microdroplets

Controlling the dynamics of mixed communities of cell-like entities (protocells) provides a step toward the development of higher-order cytomimetic behaviors in artificial cell consortia. In this paper, we develop a caged protocell model with a molecularly crowded coacervate interior surrounded by a non-cross-linked gold (Au)/poly(ethylene glycol) (PEG) nanoparticle-jammed stimuli-responsive membrane. The jammed membrane is unlocked by either exogenous light-mediated Au/PEG dissociation at the Au surface or endogenous enzyme-mediated cleavage of a ketal linkage on the PEG backbone. The membrane assembly/disassembly process is used for the controlled and selective uptake of guest protocells into the caged coacervate microdroplets as a path toward an all-water model of triggerable transmembrane uptake in synthetic protocell communities. Active capture of the guest protocells stems from the high sequestration potential of the coacervate interior such that tailoring the surface properties of the guest protocells provides a rudimentary system of protocell sorting. Our results highlight the potential for programming surface-contact interactions between artificial membrane-bounded compartments and could have implications for the development of protocell networks, storage and delivery microsystems, and microreactor technologies.

Self-Assembly of an Amphiphilic Bile Acid Dimer: A Combined Experimental and Theoretical Study of Its Medium-Responsive Fluorescence

This work describes the synthesis and aggregation behavior of a dimeric bile acid derivative in which two steroid cores are bridged by a p-di(phenylethynyl)phenylene fluorophore. The studied compound contains three key characteristics: (a) restricted conformational equilibrium in solution, (b) efficient fluorescence conferred by the bridge, and (c) medium responsiveness encoded in the steroid fragments. The incorporation of the three components afforded a compound that generates nano- and micrometric spherical particles with aggregation-responsive fluorescence emission. The observed self-assembly process of the featured molecule was induced by the gradual addition of water to the tetrahydrofuran (THF) solution. This aggregation led to significant changes in fluorescence that went from two bands at λ_em values of 370 and 390 nm in pure THF to a new spectrum with two maxima at λ_em values of 395 and 418 nm at high water contents, without a decrease in emission. The observed changes can be ascribed to weakly coupled aggregation, a hypothesis supported by multiscale molecular modeling, which sheds light on the mechanism of the self-assembly of this unconventional amphiphile.

Dehydration Enhances Prebiotic Lipid Remodeling and Vesicle Formation in Acidic Environments

The encapsulation of genetic polymers inside lipid bilayer compartments (vesicles) is a vital step in the emergence of cell-based life. However, even though acidic conditions promote many reactions required for generating prebiotic building blocks, prebiotically relevant lipids tend to form denser aggregates at acidic pHs rather than prebiotically useful vesicles that exhibit sufficient solute encapsulation. Here, we describe how dehydration/rehydration (DR) events, a prebiotically relevant physicochemical process known to promote polymerization reactions, can remodel dense lipid aggregates into thin-walled vesicles capable of RNA encapsulation even at acidic pHs. Furthermore, DR events appear to favor the encapsulation of RNA within thin-walled vesicles over more lipid-rich vesicles, thus conferring such vesicles a selective advantage.

Methods for Forming Giant Unilamellar Fatty Acid Vesicles

Fatty acids readily assemble into bilayer membranes at a pH near their apparent pK_a. Fatty acid vesicles are not only useful for research in the fields of origins of life, soft matter science, biophysics, and drug delivery, but are also cost-effective and easy to manipulate, making them ideal for teaching students about self-assembly and lipid bilayers. Here, we describe simple ways to make giant, unilamellar fatty acid vesicles suitable for microscopy and encapsulation studies.

Photo-controlled self-assembly behavior of novel amphiphilic polymers with a rosin-based azobenzene group

Novel ‘bola’ rosin-based photo-responsive amphiphilic polymers PMPn show an extremely high photoresponsive efficiency and various assembly morphological changes.

Exploring the membrane fluidity of phenyl boronic acid functionalized polymersomes using the FRAP technique and their application in the pH-sensitive release of curcumin

FRAP study to examine alterations in the membrane fluidity of functionalized polymersomes and pH responsive targeted delivery of curcumin.

Multicompartment systems: A putative carrier for combined drug delivery and targeting

In this review, we discuss recent developments in multicompartment systems commonly referred to as vesosomes, as well as their method of preparation, surface modifications, and clinical potential. Vesosomal systems are able to entrap more than one drug moiety and can be customized for site-specific delivery. We focus in particular on the possible reticuloendothelial system (RES) - mediated accumulation of vesosomes, and their application in tumor targeting, as areas for further investigation.

Colocalization Analysis of Lipo-Deoxyribozyme Consisting of DNA and Protic Catalysts in a Vesicle-Based Protocellular Membrane Investigated by Confocal Microscopy

The linkage between the self-reproduction of compartments and the replication of DNA in a compartment is a crucial requirement for cellular life. In our giant vesicle (GV)-based model protocell, this linkage is achieved through the action of a supramolecular catalyst composed of membrane-intruded DNA and amphiphilic acid catalysts (C@DNA) in a GV membrane. In this study, we examined colocalization analysis for the formation of the supramolecular catalyst using a confocal laser scanning fluorescence microscope with high sensitivity and resolution. Red fluorescence spots emitted from DNA tagged with Texas Red (Texas Red-DNA) were observed in a GV membrane stained with phospholipid tagged with BODIPY (BODIPY-HPC). To our knowledge, this is the first direct observation of DNA embedded in a GV-based model protocellular membrane containing cationic lipids. Colocalization analysis based on a histogram of frequencies of "normalized mean deviation product" revealed that the frequencies of positively correlated [lipophilic catalyst tagged with BODIPY (BODIPY-C) and Texas Red-DNA] were significantly higher than those of [BODIPY-HPC and Texas Red-DNA]. This result demonstrates the spontaneous formation of C@DNA in the GV membrane, which serves as a lipo-deoxyribozyme for producing membrane lipids from its precursor.

Computational Insights into the Aggregation Pathway of Self-Assembled Nanotubules

We performed molecular dynamics simulations of self-assembled supramolecular nanotubules constructed from amphiphiles with bent-shaped rods. By systematically examining the structure from dimeric aggregates to the fully developed nanotubule, we identified the basic building block of the nanotubule and the optimal dimensions of its stable structure which are consistent with experimental findings. Moreover, we demonstrate that the cooperative interplay of different interactions drives aggregation by selecting and stabilizing the optimal self-assembled structures for various intermediates through a complex pathway. Additionally, contraction of the nanotubule, which accompanies the dehydration process, was observed upon heating. It is suggested that the optimal stability of the self-assembled aggregates is achieved by balancing entropic and enthalpic contributions, of which the ratio is a critical factor that drives the aggregation pathway.

Did Solid Surfaces Enable the Origin of Life?

In this perspective article, I discuss whether and how solid surfaces could have played a key role in the formation of membranous primitive cells on the early Earth. I argue why surface energy could have been used by prebiotic amphiphile assemblies for unique morphological transformations, and present recent experimental findings showing the surface-dependent formation and behavior of sophisticated lipid membrane structures. Finally, I discuss the possible unique contributions of such surface-adhered architectures to the transition from prebiotic matter to living systems.

Synthesis of lipid membranes for artificial cells

A major goal of synthetic biology is to understand the transition between non-living matter and life. The bottom-up development of an artificial cell would provide a minimal system with which to study the border between chemistry and biology. So far, a fully synthetic cell has remained elusive, but chemists are progressing towards this goal by reconstructing cellular subsystems. Cell boundaries, likely in the form of lipid membranes, were necessary for the emergence of life. In addition to providing a protective barrier between cellular cargo and the external environment, lipid compartments maintain homeostasis with other subsystems to regulate cellular processes. In this Review, we examine different chemical approaches to making cell-mimetic compartments. Synthetic strategies to drive membrane formation and function, including bioorthogonal ligations, dissipative self-assembly and reconstitution of biochemical pathways, are discussed. Chemical strategies aim to recreate the interactions between lipid membranes, the external environment and internal biomolecules, and will clarify our understanding of life at the interface of chemistry and biology.

Population-Level Membrane Diversity Triggers Growth and Division of Protocells

To date, multiple mechanisms have been described for the growth and division of model protocells, all of which exploit the lipid dynamics of fatty acids. In some examples, the more heterogeneous aggregate consisting of fatty acid and diacyl phospholipid or fatty acid and peptide grows at the expense of the more homogeneous aggregate containing a restricted set of lipids with similar dynamics. Imbalances between surface area and volume during growth can generate filamentous vesicles, which are typically divided by shear forces. Here, we describe another pathway for growth and division that depends simply on differences in the compositions of fatty acid membranes without additional components. Growth is driven by the thermodynamically favorable mixing of lipids between two populations, i.e., the system as a whole proceeds toward equilibrium. Division is the result of growth-induced curvature. Importantly, growth and division do not require a specific composition of lipids. For example, vesicles made from one type of lipid, e.g., short-chain fatty acids, grow and divide when fed with vesicles consisting of another type of lipid, e.g., long-chain fatty acids, and vice versa. After equilibration, additional rounds of growth and division could potentially proceed by the introduction of compositionally distinct aggregates. Since prebiotic synthesis likely gave rise to mixtures of lipids, the data are consistent with the presence of growing and dividing protocells on the prebiotic Earth.