Interfacial molecular imprinting of Stöber particle surfaces: a simple approach to targeted saccharide adsorption

Two different states conversion mechanism of the imprinting sites

Bisphenol A molecular imprinted adsorbent (BMIA) was successfully synthesized by a sol-gel process and showed a good specific binding performance in the water. The further studies showed that the mass transfer process was controlled by in-diffusion, and the synthesis conditions would effect on the amount of imprinting sites. Scatchard model analysis evidenced that the high binding affinity sites and the low binding affinity sites were both on BMIA, and the high binding affinity sites played a key role in the specific binding process. Scatchard model analysis of temperature effect experiments and dosage effect experiments proved that the specific binding sites with high binding affinity and the unexpressed specific binding sites with low binding affinity were the two different states of the imprinting binding sites. The conversion between the two different states depended on the reaction driving force, and the increasing reaction driving force would increase the number of specific binding sites. Especially, the temperature showed a linear positive correlation with the amount of specific binding sites. Finally, a possible model was put forward to explain the two different states conversion mechanism of the imprinting sites.

Tuning the position of head groups by surfactant design in mixed micelles of cationic and carbohydrate surfactants

HYPOTHESIS

Emerging applications of carbohydrate/cationic surfactant mixtures require not only synergistic mixing, but also accessible sugar headgroups at the exterior of micelles. A previous study showed that the glucoside headgroups of octyl-β-d-glucopyranoside aggregate at the interior of mixed micelles with equimolar cetyltrimethylammonium bromide rather than mixing with trimethylammonium groups at the corona. The current study tests the hypothesis that structural characteristics of the surfactants (the relative lengths of the alkyl tails and the type of linker) can be tuned to shift the carbohydrate groups to micelle surfaces.

EXPERIMENTS

The structural arrangement of 30 mM equimolar mixed micelle solutions in D₂O is investigated using NMR. The dynamics in different regions are probed using ¹H spin-lattice (T₁) and spin-spin (T₂) relaxation measurements, and relative positioning by nuclear Overhauser effect spectroscopy (NOESY). Additional micellar properties are determined using solvatochromic fluorescent probes.

FINDINGS

Matching surfactant alkyl tail lengths is found ineffective at "pushing out" the carbohydrate headgroups due to a large mismatch in interactions between the headgroups and D₂O. However, inserting a novel polar triazole group between the carbohydrate head group and the hydrophobic tail (e.g. in n-octyl-β-d-xylopyranoside) using click chemistry is able to "pull out" the carbohydrate, thus giving accessible sugar moieties at the surface of mixed micelles.

Imprinting of Stöber particles for chirally-resolved adsorption of target monosaccharides and disaccharides

Soft imprinting of silica particles using sugar surfactants targets chirally resolved binding of saccharides.

Influence of the interface on the optical activity of confined glucose films

We report on the time evolution of the optical activity of a thinning liquid film containing glucose, and confined between two glass slides. This dynamics strongly depends on the presence of surfactant molecules. With sodium dodecyl sulfate (SDS), we evidence favorable interactions of sugar molecules with the sulfate group. As previously observed for a freely suspended soap film in the air (see Emile et al., 2013), this corresponds to an anchoring of glucose molecules at the interface. For glucose alone, we also highlight a molecular rearrangement that is not instantaneous and occurs after several minutes. This interfacial organization leads to an unusual giant optical activity that is different with or without SDS. Molecular simulations confirm the anchoring of the glucose molecules at the glass/liquid interface, and show a different molecular orientation in each case.