Photomanipulation of minimal synthetic cells: area increase, softening and interleaflet coupling of membrane models doped with azobenzene-lipid photoswitches

Abstract

Light can effectively interrogate biological systems providing control over complex cellular processes. Particularly advantageous features of photo-induced processes are reversibility, physiological compatibility, and spatiotemporal precision. Understanding the underlying biophysics of light-triggered changes in bio-systems is crucial for cell viability and optimizing clinical applications of photo-induced processes in biotechnology, optogenetics and photopharmacology. Employing membranes doped with the photolipid azobenzene-phosphatidylcholine (azo-PC), we provide a holistic picture of light-triggered changes in membrane morphology, mechanics and dynamics. We combine microscopy of giant vesicles as minimal cell models, Langmuir monolayers, and molecular dynamics simulations. We employ giant vesicle elelctrodeformation as a facile and accurate approach to quantify the magnitude, reversibility and kinetics of light-induced area expansion/shrinkage as a result of azo-PC photoisomerization and content. Area increase as high as ~25% and a 10-fold decrease in the membrane bending rigidity is observed upon trans-to-cis azo-PC isomerization. These results are in excellent agreement with simulations data and monolayers. Simulations also show that trans-to-cis isomerization of azo-PC decreases the membrane leaflet coupling. We demonstrate that light can be used to finely manipulate the shape and mechanics of photolipid-doped minimal cell models and liposomal drug carriers, thus, presenting a promising therapeutic alternative for the repair of cellular disorders.

Structural and Mechanical Response of Two-Component Photoswitchable Lipid Bilayer Vesicles

“…We did, however, find a modest (∼1%) irreversible volume expansion with UV irradiation with pure azo-PC, which might indicate that a small amount of glucose permeated the membrane. Overall, our results agree with a recent study of azo-PC that found no exchange of sugar across the membrane . By contrast, another recent study reported a higher permeability of a fluorophore when azo-PC was in cis compared to trans state .…”

“…Overall, our results agree with a recent study of azo-PC that found no exchange of sugar across the membrane. 20 By contrast, another recent study reported a higher permeability of a fluorophore when azo-PC was in cis compared to trans state. 11 (The UV intensity at the sample was not reported, but the timescales for the response appear comparable to ours, suggesting that the light intensity was similar.)…”

“…This large enhancement was attributed to enhanced coupling between the two leaflets in the trans state. 20 Anticorrelation across the Membrane and Correlations in the Plane for trans. Our results show several measures by which cis-azo-PC closely resembles DOPC (in k A , P W , and S CD ) and trans-azo-PC differs from DOPC.…”

Exploring Giant Unilamellar Vesicle Production for Artificial Cells — Current Challenges and Future Directions

“…Synthetic lipids can further be functionalized with a variety of synthetic polymers or interacting groups, e.g., poly(ethylene glycol) (PEG) linkers, fluorescent labels, nickel chelating groups, or azobenzene moieties. This functionalization can provide additional properties to the membrane, such as reducing nonspecific interactions, [42] generating photoswitchable lipids, [43] selective anchoring of molecules or proteins to the inner or outer leaflet, and more. In biological membranes, the bilayer is compositionally asymmetric, with the inner leaflet being different in lipid and protein composition from the outer leaflet.…”

Photo‐Lipids: Light‐Sensitive Nano‐Switches to Control Membrane Properties

“…It would be more interesting to see what the impact of the azobenzene lipid is in more complex lipid mixtures resembling the situation found in natural membranes. Following this idea, Aleksanyan et al [26] recently investigated the impact of the isomerization of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) monolayers and GUVs containing different 18 : 0-azoPC concentrations ranging from 5-50 mol %. They showed that the isomerization-induced reversible membrane deformation, as well as membrane thinning, and area increase were a function of the photo-lipid concentration.…”