Herein is described the switchable fluorescence response of poly(methyl methacrylate) (PMMA) brushes. Chain end fluorescein labeled PMMA brushes are prepared by combining surface‐initiated atom transfer radical polymerization (SI‐ATRP) with a copper‐catalyzed alkyne‐azide cycloaddition (CuAAC) click reaction. Successful attachment of fluorescein is confirmed by measuring fluorescence of the as‐prepared films. Utilizing co‐solvency of PMMA in isopropanol‐water mixtures, responsive behavior of the end‐functionalized brushes is demonstrated by measuring the changes in fluorescence intensity between the swollen and collapsed states.
The preparation of patterned ultrathin films (sub-10 nm) composed of end-anchored fluorescently labeled poly(methyl methacrylate) (PMMA) is presented. Telechelic PMMA was synthesized utilizing activator regenerated by electron transfer atom transfer radical polymerization and consecutively end-functionalized with alkynylated fluorescein by Cu-catalyzed azide–alkyne cycloaddition (CuAAC) “click” chemistry. The polymers were grafted via the α-carboxyl groups to silica or glass substrates pretreated with (3-aminopropyl)triethoxysilane (APTES). Patterned surfaces were prepared by inkjet printing of APTES onto glass substrates and selectively grafted with fluorescently end-labeled PMMA to obtain emissive arrays on the surface.
The membrane-protein interface in lipid nanoparticles (LNPs) is important for their in vivo behavior. Better understanding may assist to evolve current drug delivery methods to more precise, cell- or tissue-specific nanomedicine. Previously, we demonstrated how phase separation can drive liposomes to cell specific accumulation in vivo, through the selective recognition of phase-separated liposomes by triacylglycerol lipases (TGLs). This exemplified how liposome morphology can determine the preferential interaction of nanoparticles with biologically relevant proteins. Here, we investigate in detail the lipase-induced morphological changes of phase separated liposomes - which bear a lipid droplet in their bilayer - and unravel how lipase recognizes and binds to the particles at a molecular level. We find that phase separated liposomes undergo selective lipolytic degradation of their lipid droplet while overall nanoparticle integrity remains intact. Next, we combined MD simulations and in vitro experiments to identify the Tryptophan-rich loop of the lipase – a region which is involved endogenously in lipoprotein binding – as the region through which the enzyme binds to the particle. We demonstrate that this preferential binding is due to the lipid packing defects induced on the membrane by phase separation. These findings are a significant example of selective LNP – protein communication and interaction, aspects that may further the control of the in vivo behavior of lipid nanoparticles.
The membrane-protein interface in lipid nanoparticles (LNPs) is important for their in vivo behavior. Better understanding may assist to evolve current drug delivery methods to more precise, cell- or tissue-specific nanomedicine. Previously, we demonstrated how phase separation can drive liposomes to cell specific accumulation in vivo, through the selective recognition of phase-separated liposomes by triacylglycerol lipases (TGLs). This exemplified how liposome morphology can determine the preferential interaction of nanoparticles with biologically relevant proteins. Here, we investigate in detail the lipase-induced morphological changes of phase separated liposomes - which bear a lipid droplet in their bilayer - and unravel how lipase recognizes and binds to the particles at a molecular level. We find that phase separated liposomes undergo selective lipolytic degradation of their lipid droplet while overall nanoparticle integrity remains intact. Next, we combined MD simulations and in vitro experiments to identify the Tryptophan-rich loop of the lipase – a region which is involved endogenously in lipoprotein binding – as the region through which the enzyme binds to the particle. We demonstrate that this preferential binding is due to the lipid packing defects induced on the membrane by phase separation. These findings are a significant example of selective LNP – protein communication and interaction, aspects that may further the control of the in vivo behavior of lipid nanoparticles.
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