Micrometer-sized TPM emulsion droplets with surface-mobile binding groups

Abstract

Colloids coated with lipid membranes have been widely employed for fundamental studies of lipid membrane processes, biotechnological applications such as drug delivery and biosensing, and more recently, for self-assembly. The latter has been made possible by inserting DNA oligomers with covalently linked hydrophobic anchors into the membrane. The lateral mobility of the DNA linkers on micrometer-sized droplets and solid particles has opened the door to creating structures with unprecedented structural flexibility. Here, we investigate micro-emulsions of TPM (3-(trimethoxysilyl)propyl methacrylate) as a platform for lipid monolayers and further functionalization with proteins and DNA oligonucleotides. TPM droplets can be produced with a narrow size distribution and are polymerizable, thus providing supports for model lipid membranes with controlled size and curvature. With fluorescence recovery after photobleaching, we observed that droplet-attached lipids, NeutrAvidin proteins, as well as DNA oligonucleotides all show mobility on the surface. We explored the assembly of micron-sized particles on TPM-droplets by exploiting either avidin-biotin interactions or double-stranded DNA with complementary single-stranded end groups. While the single molecules are mobile, the particles that are attached to them are not. We propose that this is caused by the heterogeneous nature of emulsified TPM, which forms an oligomer network that limits the collective motion of linkers, but allows the surface mobility of individual molecules.

Colloid supported lipid bilayers for self-assembly

“…After 1 h, the fluorescence intensity of the CSLBs with F-127 was comparable to that of control particles not coated with linker dsDNA (Figure 3 C-F). We therefore conclude that F-127 removed the cholesterol-anchored linker DNA from the bilayer, in line with recent experiments on emulsion droplets coated with mobile DNA linkers [55].…”

“…Note that the slight repulsion at small angles is caused by boundary effects inherent to our analysis method. linkers, the large linker patch that is formed between particles can slow down the motion when the supporting fluid is inhomogeneous [55] and colloidal joints lose their flexibility with an increasing concentration of dsDNA linkers in the bond area [16].…”

Programmable interactions with biomimetic DNA linkers at fluid membranes and interfaces

“…Droplets offer advantages in terms of stability, robustness, and the possibility of easily generating large mono-disperse samples by means of microfluidic devices [101]. Methods for anchoring molecular linkers to oil droplets have often involved the use of phospholipids whose head groups are functionalsied with PEG-biotin anchors [17,95,[97][98][99]102]. Similar to the strategy mentioned above for DNA functionalisation of liposomes, streptavidin is then used to bridge between the lipid anchors and oligonucleotides [17,95,[97][98][99]102] or more complex DNA nanostructures [96], which then mediate multivalent interactions.…”

Contact angle as a powerful tool in anisotropic colloid synthesis

“…Under basic conditions, the methoxy groups of the MPTMS hydrolyze, yielding droplets. [19] While siloxane bonds are also formed at this stage, previous studies suggested that these droplets behave more liquid-like than gel-like, as droplets are able to reach energetically favourable locations. [10] After an initiator is added, the methacrylate groups polymerize -or cross-link -and the droplet solidifies.…”