Phosphonodithioester–Amine Coupling as a Key Reaction Step for the Design of Cationic Amphiphiles Used for Gene Delivery

A convergent synthesis of cationic amphiphilic compounds is reported here with the use of the phosphonodithioester–amine coupling (PAC) reaction. This versatile reaction occurs at room temperature without any catalyst, allowing binding of the lipid moiety to a polar head group. This strategy is illustrated with the use of two lipid units featuring either two oleyl chains or two-branched saturated lipid chains. The final cationic amphiphiles were evaluated as carriers for plasmid DNA delivery in four cell lines (A549, Calu3, CFBE and 16HBE) and were compared to standards (BSV36 and KLN47). These new amphiphilic derivatives, which were formulated with DOPE or DOPE-cholesterol as helper lipids, feature high transfection efficacies when associated with DOPE. The highest transfection efficacies were observed in the four cell lines at low charge ratios (CR = 0.7, 1 or 2). At these CRs, no toxic effects were detected. Altogether, this new synthesis scheme using the PAC reaction opens up new possibilities for investigating the effects of lipid or polar head groups on transfection efficacies.

Assessing Surface Coverage of Aminophenyl Bonding Sites on Diazotised Glassy Carbon Electrodes for Optimised Electrochemical Biosensor Performance

Electrochemical biosensors using carbon-based electrodes are being widely developed for the detection of a range of different diseases. Since their sensitivity depends on the surface coverage of bioreceptor moieties, it necessarily depends on the surface coverage of amine precursors. Electrochemical techniques, using ferrocene carboxylic acid as a rapid and cheap assay, were used to assess the surface coverage of amino-phenyl groups attached to the carbon electrode. While the number of electrons transferred in the first step of diazotisation indicated a surface coverage of 8.02 ± 0.2 × l0−10 (mol/cm2), and those transferred in the second step, a reduction of nitrophenyl to amino-phenyl, indicated an amine surface coverage of 4–5 × l0−10 (mol/cm2), the number of electrons transferred during attachment of the amine coupling assay compound, ferrocene carboxylic acid, indicated a much lower available amine coverage of only 2.2 × l0−11 (mol/cm2). Furthermore, the available amine coverage was critically dependent upon the number of cyclic voltammetry cycles used in the reduction, and thus the procedures used in this step influenced the sensitivity of any subsequent sensor. Amine coupling of a carboxyl terminated anti-beta amyloid antibody specific to Aβ(1-42) peptide, a potential marker for Alzheimer’s disease, followed the same pattern of coverage as that observed with ferrocene carboxylic acid, and at optimum amine coverage, the sensitivity of the differential pulse voltammetry sensor was in the range 0–200 ng/mL with the slope of 5.07 µA/ng·mL−1 and R2 = 0.98.

Efficient O-phthalaldehyde-amine Coupling Reaction for the Synthesis of Bottlebrush Polymer under Physiological Conditions

A new method to prepare bottlebrush polymer poly(2-aminoethyl methacrylate hydrochloride)-graft-poly(N,N-dimethylacrylamide) (PAMA-g-PDMA) by the combination of “grafting onto” and catalyst-free o-phthalaldehyde (OPA)-amine coupling reaction was proposed. The PAMA backbone with primary...