Photoinduced adsorption of oligonucleotides on polyvinyl chloride films containing malachite green derivative.

DNA adsorption on the micrometer scale in a simple and cost-effective manner has received considerable interest. We prepared a film by casting an organic solvent containing polyvinyl chloride and a malachite green derivative, which can be photoionized to afford a cationic moiety for interaction with DNA. In this article, we report photoinduced oligonucleotide adsorption on a film that offers spatial and temporal control over oligonucleotide adsorption. Fluorescence microscopy was used to observe the oligonucleotide adsorption. Oligonucleotides of various sequences and lengths were also examined. UV irradiation using a photomask having 100 µm-diameter holes promoted the oligonucleotide adsorption on the film, whereas there was hardly any oligonucleotide adsorbed on the non-irradiated area. We found that the nucleobase contributed to the adsorption and part of the anchor in the oligonucleotide chain was responsible for the adsorption on the film.

Photoinduced binding of malachite green copolymer to parallel G-quadruplex DNA.

Designing ligands that selectively target G-quadruplex DNAs has gained attention due to their possible roles in regulation of gene expression and as anti-cancer agents. In this article, we report irradiation-induced ligand binding to G-quadruplex DNAs which offers a novel approach to targeting specific G-quadruplexes. Photoinduced binding to G-quadruplex DNAs was observed for copolymers of poly(vinyl alcohol) carrying a malachite green moiety (PVAMG). This molecule has an aromatic ring with cationic charge, which after irradiation becomes a binding site for G-quadruplex DNA. PVAMGs acted as neutral polymers with no binding affinity under dark conditions. The photoinduced binding was revealed by fluorescence spectroscopy, NMR spectroscopy, UV melting curve, and DNA polymerase stop assay. PVAMGs showed preference to parallel G-quadruplex structures over mixed parallel/antiparallel structures. PVAMGs were found to be noncytotoxic under both dark and irradiated conditions up to a concentration of 20 µM.

Irradiation-induced fusion between giant vesicles and photoresponsive large unilamellar vesicles containing malachite green derivative.

Light-initiated fusion between vesicles has attracted much attention in the research community. In particular, fusion between photoresponsive and non-photoresponsive vesicles has been of much interest in the development of systems for the delivery of therapeutic agents to cells. We have performed fusion between giant vesicles (GVs) and photoresponsive smaller vesicles containing malachite green (MG) derivative, which undergoes ionization to afford a positive charge on the molecule by irradiation. The fusion proceeds as the concentration of GV lipid increases toward equimolarity with the lipid of the smaller vesicle. It is also dependent on the molar percentage of photoionized MG in the lipid of the smaller vesicle. On the other hand, the fusion is hardly affected by the anionic component of the GV. The photoinduced fusion was characterized by two methods, involving the mixing of lipid membranes and of aqueous contents. Fluorescence microscopy revealed that irradiation triggered the fusion of a single GV with the smaller vesicles containing MG.