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A photocleavable membrane component was introduced into synthetic liposomes to achieve light-triggered pinocytosis-like behavior as a potential solution to the feeding requirement in protocell and bottom-up artificial cell systems. Light-triggered pinocytosis was observed in both elongated liposomes, prepared by lipid film hydration, and osmotically stressed spherical vesicles prepared by the pull-down method. Liposomes formed via lipid film hydration consistently underwent pinocytosis in cases of lobed structures or in prolate ellipsoidal structures with aspect ratios ≥2, suggesting that a critical volume-to-surface-area ratio is necessary to drive pinocytosis. When liposomes formed by the pull-down method were osmotically deformed prior to irradiation, an average of 44% exhibited pinocytosis. This light-driven pinocytosis behavior is hypothesized to be due to an asymmetric distribution of photocleavable lipid between the inner and outer leaflet, consistent with the observation that liposomes assembled a...

Photocleavable liposomes were formed in situ through the coupling of an o-nitrobenzyl-containing azide tail precursor and an alkyne-functionalized lysolipid by the copper-catalyzed azide–alkyne cycloaddition (CuAAC) reaction. Inclusion of the photolabile o-nitrobenzyl-structure enables control over the permeability and morphology of the liposomes. Photolysis of the o-nitrobenzyl group changes the molecular structure of the photolabile phospholipids, inducing phase transitions and permeability increases in the bilayer membrane, ultimately disrupting the liposome entity.

Synthetic vesicles have a wide range of applications from drug and cosmetic delivery to artificial cell and membrane studies, making simple and controlled formation of vesicles a large focus of the field today. Here, we report the use of the photoinitiated copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction using visible light to introduce spatiotemporal control into the formation of vesicles. Upon the establishment of the spatiotemporal control over vesicle formation, it became possible to adjust initiation conditions to modulate vesicle sizes resulting in the formation of controllably small or large vesicles based on light intensity or giant vesicles when the formation was initiated in flow-free conditions. Additionally, this photoinitiated method enables vesicle formation at a density 400-fold higher than initiation using sodium ascorbate as the catalyst. Together, these advances enable the formation of high-density, controlled size vesicles using low-energy wavelengths while producing enhanced control over the formation characteristics of the vesicle.

Polysulfide network oxidative modification is presented. Fundamental differences between the properties of sufide-based and sulfone-based networks are discussed, and a method for producing the sulfone-based materials from thioether-based materials is developed. Oxidation enables significant mechanical property enhancements of polysulfide materials without any deleterious effects that typically accompany cross-linking polymerizations. Various application examples such as sulfide-containing particle modification and hardening of soft lithography or thiol–ene 3D microprinted objects are also shown.

Synthetic unilamellar liposomes, functionalized to enable novel characteristics and behavior, are of great utility to fields such as drug delivery and artificial cell membranes. However, the generation of these liposomes is frequently highly labor-intensive and time consuming whereas in situ liposome formation presents a potential solution to this problem. A novel method for in situ lipid formation is developed here through the covalent addition of a thiol-functionalized lysolipid to an acrylate-functionalized tail via the thiol-Michael addition reaction with potential for inclusion of additional functionality via the tail. Dilute, stoichiometric mixtures of a thiol lysolipid and an acrylate tail reacted in an aqueous media at ambient conditions for 48 hours reached nearly 90% conversion, forming the desired thioether-containing phospholipid product. These lipids assemble into a high density of liposomes with sizes ranging from 20 nm to several microns in diameter and include various structures ranging from spheres to tubular vesicles with structure and lamellarity dependent upon the catalyst concentration used. To demonstrate lipid functionalization, an acrylate tail possessing a terminal alkyne was coupled into the lipid structure. These functionalized liposomes enable photo-induced polymerization of the terminal alkyne upon irradiation.

Thiol lysolipids undergo thiol–thioester exchange with two phenyl thioester-functionalized tails to produce phospholipid structures that assemble into liposomes with differences in exchange rates, temperature sensitivity, permeability, and continued exchange behavior. This in situ formation reaction imparts dynamic characteristics into the membrane for downstream liposome functionalization and mimics native membrane remodeling.

Photocleavable liposomes were formed

As more methodologies for generating and manipulating biomimetic cellular systems are developed, opportunities arise for combining different methods to create more complex synthetic biological constructs. This necessitates an increasing need for tools to selectively trigger individual methodologies. Here we demonstrate ruthenium tris-bipyridine mediated photoredox triggering of the copper catalyzed alkyne azide cycloaddition reaction (CuAAC), resulting in the synthesis of biomimetic phospholipids in situ, and subsequent membrane assembly. The use of a ruthenium–copper electron transport chain to trigger phospholipid assembly opens up future opportunities for spatiotemporal synthesis of membranes.