Cover and uncover : chiral switching exploiting templating and layer-by-layer grafting

Consecutive grafting of crosslinked L-phenylalanine anilide, D-phenylalanine anilide and non-imprinted polymer layers on the surface of wide pore silica resulted in porous composite beads displaying enantiomeric discrimination reflecting the last grafted layer. This no longer holds for beads freed from silica, which instead display enantio-selectivity reflecting the first grafted layer

Insights into the formation, structural properties and performance of RAFT polymerized L-phenylalanine anilide molecularly imprinted polymers

Conventional molecularly imprinted polymers (MIPs) are amorphous materials with a nonuniform microenvironment and a broad distribution of binding sites. Controlled radical polymerization has been demonstrated to improve their properties in this regard. The RAFT method was employed in the present study with the aim of achieving more homogeneous MIP monolithic structures. RAFT control by α-cyanobenzyldithiobenzoate was employed during the synthesis of a poly(methacrylic acid-co-ethylene glycol dimethacrylate) conventional MIP for L-phenylalanine anilide. The influence of the amount of the added RAFT agent on the polymerization as well as on the polymer porous structure and properties was studied. The results demonstrate that the RAFT agent promoted retardation and a more gel-like polymer morphology as reflected in a decrease in pore diameter and an increased swelling factor with the added RAFT agent. This was accompanied by an enhanced thermal stability of up to 100 °C compared to a corresponding MIP prepared by FRP. The RAFT polymers were then tested in the chromatographic mode due to their ability to resolve the racemate D,L-PheNHPh. An optimum RAFT agent level during polymerization was found to result in a markedly enhanced selectivity, column efficiency and resolution accompanied by a considerably higher sample loading capacity when compared to polymers prepared in the absence of the RAFT agent

Recognitive nano-thin-film composite beads for the enantiomeric resolution of the metastatic breast cancer drug aminoglutethimide

Straightforward crushing and sieving bulk polymeric R-aminoglutethimide-imprinted materials were prepared by classical free radical polymerization, whereas nano thin walled grafted imprinted materials were prepared using RAFT mediated control polymerization technique. A stoichiometric non-covalent approach based on a triply hydrogen bonding functional monomer-template 1:1 complex (K=599mol(-1)L(-1)) led to chiral selectors far outperforming previously used selectors for resolving this racemate. The recognitive materials produced here (enantioselectivity factors, α∼10) also have no match within the previously reported enantioselective imprinted polymers (α 1.2-4.5). We here demonstrate a potentially generic solution to produce good quality grafted MIPs for templates interacting by hydrogen bonding alone, relying on solvent polarity tuning, significantly extending the range of templates compatible with this format

Comparison of success and pain levels of supination-flexion and hyperpronation maneuvers in childhood nursemaid's elbow cases

Objective: The aim of this study was to compare the hyperpronation (HP) and the supination-flexion (SF) reduction techniques for reducing nursemaid's elbow in terms of efficacy and pain