Alexander Trifonov

Integrated photosystem II-based photo-bioelectrochemical cells

Photosynthesis is a sustainable process that converts light energy into chemical energy. Substantial research efforts are directed towards the application of the photosynthetic reaction centres, photosystems I and II, as active components for the light-induced generation of electrical power or fuel products. Nonetheless, no integrated photo-bioelectrochemical device that produces electrical power, upon irradiation of an aqueous solution that includes two inter-connected electrodes is known. Here we report the assembly of photobiofuel cells that generate electricity upon irradiation of biomaterial-functionalized electrodes in aqueous solutions. The cells are composed of electrically contacted photosystem II-functionalized photoanodes and an electrically wired bilirubin oxidase/carbon nanotubes-modified cathode. Illumination of the photoanodes yields the oxidation of water to O(2) and the transfer of electrons through the external circuit to the cathode, where O(2) is re-reduced to water.

Integration of Switchable DNA-Based Hydrogels with Surfaces by the Hybridization Chain Reaction.

A novel method to assemble acrylamide/acrydite DNA copolymer hydrogels on surfaces, specifically gold-coated surfaces, is introduced. The method involves the synthesis of two different copolymer chains consisting of hairpin A, HA, modified acrylamide copolymer and hairpin B, HB, acrylamide copolymer. In the presence of a nucleic acid promoter monolayer associated with the surface, the hybridization chain reaction between the two hairpin-modified polymer chains is initiated, giving rise to the cross-opening of hairpins HA and HB and the formation of a cross-linked hydrogel on the surface. By the cofunctionalization of the HA- and HB-modified polymer chains with G-rich DNA tethers that include the G-quadruplex subunits, hydrogels of switchable stiffness are generated. In the presence of K(+)-ions, the hydrogel associated with the surface is cooperatively cross-linked by duplex units of HA and HB, and K(+)-ion-stabilized G-quadruplex units, giving rise to a stiff hydrogel. The 18-crown-6-ether-stimulated elimination of the K(+)-ions dissociates the bridging G-quadruplex units, resulting in a hydrogel of reduced stiffness. The duplex/G-quadruplex cooperatively stabilized hydrogel associated with the surface reveals switchable electrocatalytic properties. The incorporation of hemin into the G-quadruplex units electrocatalyzes the reduction of H2O2. The 18-crown-6-ether stimulated dissociation of the hemin/G-quadruplex bridging units leads to a catalytically inactive hydrogel.

G-Quadruplex-Stimulated Optical and Electrocatalytic DNA Switches

The K(+) /18-crown-6-(or [2.2.2] cryptand)-stimulated formation and dissociation of G-quadruplex nanostructures lead to the cyclic and switchable photonic and electrocatalytic molecular devices.

Gossypol-Capped Mitoxantrone-Loaded Mesoporous SiO2 NPs for the Cooperative Controlled Release of Two Anti-Cancer Drugs

Mesoporous SiO2 nanoparticles, MP-SiO2 NPs, are functionalized with the boronic acid ligand units. The pores of the MP-SiO2 NPs are loaded with the anticancer drug mitoxantrone, and the pores are capped with the anticancer drug gossypol. The resulting two-drug-functionalized MP-SiO2 NPs provide a potential stimuli-responsive anticancer drug carrier for cooperative chemotherapeutic treatment. In vitro experiments reveal that the MP-SiO2 NPs are unlocked under environmental conditions present in cancer cells, e.g., acidic pH and lactic acid overexpressed in cancer cells. The effective unlocking of the capping units under these conditions is attributed to the acidic hydrolysis of the boronate ester capping units and to the cooperative separation of the boronate ester bridges by the lactate ligand. The gossypol-capped mitoxantrone-loaded MP-SiO2 NPs reveals preferential cytotoxicity toward cancer cells and cooperative chemotherapeutic activities toward the cancer cells. The MCF-10A epithelial breast cells and the malignant MDA-MB-231 breast cancer cells treated with the gossypol-capped mitoxantrone-loaded MP-SiO2 NPs revealed after a time-interval of 5 days a cell death of ca. 8% and 60%, respectively. Also, the gossypol-capped mitoxantrone-loaded MP-SiO2 NPs revealed superior cancer-cell death (ca. 60%) as compared to control carriers consisting of β-cyclodextrin-capped mitoxantrone-loaded (ca. 40%) under similar loading of the mitoxantrone drug. The drugs-loaded MP-SiO2 NPs reveal impressive long-term stabilities.