Phototriggered DNA Complexation and Compaction Using Poly(vinyl alcohol) Carrying a Malachite Green Moiety

Malachite green-derivatized cationic comb-type copolymer acts as a photoresponsive artificial chaperone

Molecular chaperones play vital roles in various physiological reactions by regulating the folding and assembly of biomacromolecules. We have demonstrated that cationic comb-type copolymers exhibit chaperone activity for anionic biomolecules including DNA and ionic peptide via the formation of soluble interpolyelectrolyte complexes. The development of smart artificial chaperones that can be spatiotemporally controlled by a remotely guided signal would expand the functions of artificial chaperones. Herein, to enable photocontrol of chaperone activity, a cationic comb-type copolymer bearing malachite green as a photoresponsive unit was designed. We first prepared a series of carboxylic acid derivatives of malachite green identified a derivative that could be quickly and quantitatively converted to the cationic form from the nonionic form by photoirradiation. This derivative was conjugated to the cationic comb-type copolymer, poly(allylamine)-graft-poly(ethylene glycol) through a condensation reaction. Upon photoirradiation, the copolymer bearing 9 mol% malachite green enhanced the membrane disruptive activity of acidic peptide E5 and induced morphological changes in liposomes. This demonstration of photoresponsive activation of chaperoning activity of a copolymer suggests that the installation of carboxyl derivatives of malachite green will impart photoresponsiveness to various materials including biopolymers.

Surface Functionalization of Polymer Particles for Cell Targeting by Modifying Emulsifier Chemistry

The oil in water emulsion/solvent extraction method is used to fabricate many FDA approved, polymer particle formulations for drug delivery. However, these formulations do not benefit from surface functionalization that can be achieved through tuning particle surface chemistry. Poly(vinyl alcohol) (PVA) is the emulsifier used for many FDA approved formulations and remains associated with the particle surface after fabrication. We hypothesized that the hydroxyl groups in PVA could be conjugated with biomolecules using isothiocyanate chemistry and that these modifications would endow the particle surface with additional functionality. We demonstrate that fluorescein isothiocyanate and an isothiocyanate derivatized mannose molecule can be covalently attached to PVA in a one-step reaction. The modified PVA polymers perform as well as unmodified PVA in acting as an emulsifier for fabrication of poly(lactide-co-glycolide) particles. Particles made with the fluorescein modified PVA exhibit fluorescence confined to the particle surface, while particles made with mannose modified PVA bind concanavalin A. In addition, mannose modified PVA increases particle association with primary macrophages by three-fold. Taken together, we present a facile method for modifying the surface reactivity of polymer particles widely used for drug delivery in basic research and clinical practice. Given that methods are established for conjugating the isothiocyanate functional group to a wide range of biomolecules, our approach may enable PVA based biomaterials to engage a multitude of biological systems.

pH-triggered solubility and cytotoxicity changes of malachite green derivatives incorporated in liposomes for killing cancer cells

Three different malachite green leuco derivatives (MG-Xs) are incorporated in liposomes. In all three cases, a substituent (X) is covalently linked to the central carbon atom, abbreviated as MG-OH, MG-OCH3, and MG-CN. The three MG-X compounds are solubilized separately in liposome membranes and become cationic (MG+) and water soluble under acidic conditions. MG+ is consequently released from the liposome to the aqueous exterior. Their release behavior corresponds to their ionization ability: MG-OH > MG-OCH3 > MG-CN. The cellular uptake of the liposomes, the cytotoxic effect, and the location of MG+ in cancer cells are investigated using murine cells derived from colon cancer (Colon 26 cells) and human embryonic kidney cells (HEK 293 cells). The toxic effect on cancer cells is correlated to the ionization ability of MG-Xs. The liposomes effectively deliver MG+via the endocytic pathway, resulting in the cytotoxicity of liposomes containing MG-OH which is higher than that of free MG-OH and MG+. The difference in the phospholipids constituting the liposome membranes barely had an effect on the ionization ratio and the cytotoxicity of MG-OH. Confocal fluorescence microscopic observations revealed that MG+ is ultimately transported into the nuclei after being released in acidic cellular compartments.

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.

Photoinduced conformational changes in DNA by poly(vinyl alcohol) carrying a malachite green moiety for protecting DNA against attack by nuclease

Light is a highly advantageous means of specific cell targeting. Though targeted gene delivery is an important characteristic of an ideal delivery vehicle, there has been little effort to develop a photoresponsive vector. Among nonviral vectors, cationic substances interact effectively with negatively charged DNA. With this property in mind, we designed copolymers of poly(vinyl alcohol) carrying a malachite green moiety (PVAMG) with different molecular weights. Though PVAMG has no affinity for DNA in the absence of light, it undergoes photoionization in the presence of light to afford cationic DNA binding sites. The DNA-PVAMG complex was investigated with respect to DNA conformational changes and its protective nature, which are important properties for nonviral vectors. PVAMG irradiation promoted DNA conformational transitions from coils to partial globules to compacted globules. The complex had a protective effect against DNase I after PVAMG irradiation, while DNA was degraded under dark conditions. The effect on DNA transition and the protective nature were sensitive to the molecular weight of PVAMG. The data regarding binding constants and binding mode provided insight into the structure of the DNA-PVAMG complex. To withstand DNase I attacks, complexation results in the compaction of DNA, which is further covered with PVAMG.