Membrane insertion of sliding anchored polymers

Abstract

We have studied the insertion into lipid bilayers of Sliding Anchored Polymers (SAPs), a new class of macromolecules based on topological complexes between end-capped polyethylene glycol (PEG) polymers and mono-cholesteryl cyclodextrins (CD). By using Infra Red Reflection Absorption Spectroscopy (IRRAS) we demonstrate that these new sliding polymer complexes anchor well in phospholipid model membranes self-assembled from DPPC. The in-plane organization is characterized by Brewster Angle Microscopy (BAM) at the air-water interface and by Atomic Force Microscopy (AFM) for lipid monolayers and for lipid bilayers deposited on mica. Demixing between SAPs and the phospholipids is observed even at low surface pressures. Using neutron reflectivity, we show that for sufficiently high polymer densities the SAPs inserted into lipid monolayers and lipid bilayers form polymer brushes, consistent with theoretical predictions for polymers with a sliding anchor.

Effect of silica coating and further silica surface decoration by phospholipid bilayer on quenching of Tb(III) complexes by adrenochrome

“…The 1/T 2 and 1/T 1 rates are mainly contributed by proton relaxation rates of water molecules in a nearest environment of metal ions [37,39], which explains their sensitivity to ternary complex formation of paramagnetic ions. It is also worth noting that the presence of the bowl-like calix [4]arene and thiacalix [4]arene cavities (Scheme 1c) is the prerequisite for the inclusion complex formation with organic molecules [37,40,41]. The lack of any detectable effect of the catecholamines on the luminescence of [Tb(TCAS)] in buffer solution According to literature data the formation of AD from EP is slow at pH 6, while this process is greatly accelerated under pH increase and complex formation with metal ions [25][26][27].…”

“…Summarizing, it is worth noting that the comparative analysis of the quenching regularities of Tb(III)-p-sulfonatothiacalix [4]arene complexes, those doped into the silica nanoparticles and the latter within the silica supported bilayers in the buffer solutions of the adrenochrome highlights the impact of silica/water and silica/phospholipid/water interfaces in the sensing function of the Tb(III)-doped nanoparticles. The obtained results highlight the shielding effect of the silica coating, which restricts the dynamic quenching of the Tb(III)-centered luminescence resulted from the collision with adrenochrome molecules, while this quenching is the concentration-induced for the Tb(III) complexes in the solutions.…”

“…The synthesis of p-sulfonatothiacalix [4]arene (TCAS) was carried out according to the known procedures [34]. The synthesis of silica coated Tb(III) nanoparticles (42 ± 5 nm) has been performed according to reverse microemulsion procedure presented in the work [35].…”

“…Wide emission band of adrenochrome (AD) with the maximum wavelength at 560 nm reveals the triplet level, which can participate in a quenching of Tb(III)-centered luminescence through an energy transfer mechanism as an energy acceptor. The choice of Tb(III) complexes with p-sulfonatothiacalix [4]arene (TCAS 3 − , Scheme 1) as luminophores is connected with Tb(III) centered emission occurring as four narrow bands: 5 D 4 → 7 F 6 (489 nm), 5 D 4 → 7 F 5 (546 nm), 5 D 4 → 7 F 4 (582 nm), and 5 D 4 → 7 F 3 (620 nm) [1], which in turn is the prerequisite for the quenching by adrenochrome through an energy transfer mechanism.…”

“…Non-covalent silica surface decoration is a convenient tool to vary a sensing function of silica coated luminophores due to an impact of an exterior layer in an interfacial binding of substrates. Phospholipid bilayer deposition onto silica nanoparticles (silica beads) or so-called supported lipid bilayers (SLBs) [4][5][6] is of great importance in growing the blood compatibility of nanomaterial for imaging and drug delivery [7,8]. The binding ability of phospholipid bilayers toward small biorelevant molecules is well known [9,10].…”