Protonation-induced pH increase at the triblock copolymer micelle interface for transient membrane permeability at neutral pH.

Achieving controlled membrane permeability using pH-responsive block copolymers is crucial for selective intercellular uptake. We have shown that the pH at the triblock-copolymer micelle interface as compared to its bulk pH can help regulate membrane permeability. The pH-dependent acid/base equilibriums of two different interface-interacting pH probes were determined in order to measure the interfacial pH for a pH-responsive triblock copolymer (TBP) micelle under a wide range of bulk pH (4.

Detection of Curvature-Radius-Dependent Interfacial pH/Polarity for Amphiphilic Self-Assemblies: Positive versus Negative Curvature.

It is possible that a defined curvature at the membrane interface controls its pH/polarity to exhibit specific bioactivity. By utilizing an interface-interacting spiro-rhodamine pH probe and the Schiff base polarity probe, we have shown that the pH deviation from the bulk phase to the interface (ΔpH)/interfacial dielectric constant (κ(i)) for amphiphilic self-assemblies can be regulated by the curvature geometry (positive/negative) and its radius. According to H NMR and fluorescence anisotropy investigations, the probes selectively interact with an anionic interfacial Stern layer.

A ratiometric solvent polarity sensing Schiff base molecule for estimating the interfacial polarity of versatile amphiphilic self-assemblies.

A newly synthesised Schiff base molecule (PMP) existing in equilibrium between non-ionic and zwitterionic forms displays solvent polarity induced ratiometric interconversion from one form to another, such novelty being useful to detect the medium polarity. The specific interface localisation of PMP in versatile amphiphilic self-assembled systems has been exploited to monitor their interfacial polarity by evaluating such interconversion equilibrium with simple UV-Vis spectroscopy. In spite of the large differences in pH and/or viscosity between the bulk and interface, the unchanged equilibrium between the two molecular forms on varying the medium pH or viscosity provides a huge advantage for the exclusive detection of interfacial polarity.

A simple interfacial pH detection method for cationic amphiphilic self-assemblies utilizing a Schiff-base molecule.

A simple pH-sensing method for cationic micelle and vesicle interfaces is introduced, utilizing a Schiff-base molecule, 2-((4H-1,2,4-triazol-4-ylimino)methyl)-6-(hydroxymethyl)-4-methylphenol (AH). AH containing a phenolic moiety was obtained by the reaction between 4-amino-4H-1,2,4-triazole containing polar O- and N-centres with opposite polarity to the cationic interface and 2-hydroxy-3-(hydroxymethyl)-5-methylbenzaldehyde. The acid/base equilibrium of AH was investigated at the interfaces of cetrimonium bromide (CTAB) micelles, tri-block-copolymeric micelles (TBPs) and large unilamellar vesicles (LUVs) of different lipid compositions using steady state UV-Vis absorption spectroscopy.