Flavin Conjugated Polydopamine Nanoparticles Displaying Light-Driven Monooxygenase Activity

A hybrid of flavin and polydopamine (PDA) has been explored as a photocatalyst, drawing inspiration from natural flavoenzymes. Light-driven monoxygenase activity has been demonstrated through the oxidation of indole under blue light irradiation in ambient conditions, to afford indigo and indirubin dyes. Compared to riboflavin, a flavin-polydopamine hybrid is shown to be more resistant to photobleaching and more selective toward dye production. In addition, it has been demonstrated that it can be recycled from the solution and used for up to four cycles without a marked loss of activity, which is a significant improvement compared to other heterogenous flavin catalysts. The mechanism of action has been explored, indicating that the PDA shell plays an important role in the stabilization of the intermediate flavin-peroxy species, an active component of the catalytic system rather than acting only as a passive nanocarrier of active centers

Flavin Conjugated Polydopamine Nanoparticles Displaying Light-Driven Monooxygenase Activity.

A hybrid of flavin and polydopamine (PDA) has been explored as a photocatalyst, drawing inspiration from natural flavoenzymes. Light-driven monoxygenase activity has been demonstrated through the oxidation of indole under blue light irradiation in ambient conditions, to afford indigo and indirubin dyes. Compared to riboflavin, a flavin-polydopamine hybrid is shown to be more resistant to photobleaching and more selective toward dye production. In addition, it has been demonstrated that it can be recycled from the solution and used for up to four cycles without a marked loss of activity, which is a significant improvement compared to other heterogenous flavin catalysts. The mechanism of action has been explored, indicating that the PDA shell plays an important role in the stabilization of the intermediate flavin-peroxy species, an active component of the catalytic system rather than acting only as a passive nanocarrier of active centers

A self-reporting tetrazole-based linker for the biofunctionalization of gold nanorods.

A photochemical approach based on nitrile imine-mediated tetrazole-ene cycloaddition is introduced to functionalize gold nanorods with biomolecules. For this purpose, a bifunctional, photoreactive linker containing thioctic acid as the Au anchoring group and a tetrazole moiety for the light-induced reaction with maleimide-capped DNA was prepared. The tetrazole-based reaction on the nanoparticles' surface results in a fluorescent pyrazoline product allowing for the spectroscopic monitoring of the reaction. This first example of nitrile imine-mediated tetrazole-ene cycloaddition (NITEC)-mediated biofunctionalization of Au nanorods paves the way for the attachment of sensitive biomolecules, such as antibodies and other proteins, under mild conditions and expands the toolbox for the tailoring of nanomaterials

Fluorescence Excitation by Enhanced Plasmon Upconversion under Continuous Wave Illumination

We demonstrate effective background-free continuous wave nonlinear optical excitation of molecules that are sandwiched between asymmetrically constructed plasmonic gold nanoparticle clusters. We observe that near infrared photons are converted to visible photons through efficient plasmonic second harmonic generation. Our theoretical model and simulations demonstrate that Fano resonances may be responsible for being able to observe nonlinear conversion using a continuous wave light source. We show that nonlinearity enhancement of plasmonic nanostructures via coupled quantum mechanical oscillators such as molecules can be several orders larger as compared to their classical counterparts.Comment: 11 pages, 8 figure

Bimetallic Copper-Heme-Protein-DNA Hybrid Catalyst for Diels Alder Reaction

A bimetallic heme-DNA cofactor, containing an iron and a copper center, was synthesized for the design of novel hybrid catalysts for stereoselective synthesis. The cofactor was used for the reconstitution of apo-myoglobin. Both the cofactor alone and its myoglobin adduct were used to catalyze a model Diels Alder reaction. Stereoselectivity of this conversion was analyzed by chiral HPLC. Reactions carried out in the presence of myoglobin-heme-Cu-DNA catalyst showed greater product conversion and stereoselectivity than those carried out with the heme-Cu-DNA cofactor. This observation suggested that the protein shell plays a significant role in the catalytic conversion.(doi: 10.5562/cca1828

DNA-directed immobilization of horseradish peroxidase onto porous SiO2 optical transducers.

Multifunctional porous Si nanostructure is designed to optically monitor enzymatic activity of horseradish peroxidase. First, an oxidized PSi optical nanostructure, a Fabry-Pérot thin film, is synthesized and is used as the optical transducer element. Immobilization of the enzyme onto the nanostructure is performed through DNA-directed immobilization. Preliminary studies demonstrate high enzymatic activity levels of the immobilized horseradish peroxidase, while maintaining its specificity. The catalytic activity of the enzymes immobilized within the porous nanostructure is monitored in real time by reflective interferometric Fourier transform spectroscopy. We show that we can easily regenerate the surface for consecutive biosensing analysis by mild dehybridization conditions

Activity-enhanced DNAzyme for design of label-free copper( ii ) biosensor

Metal ion-driven, DNA-cleaving DNAzymes are characterised by high selectivity and specificity. However, their use for metal ion sensing remains largely unexplored due to long reaction times and poor reaction yields relative to RNA-cleaving DNAzymes and other sensing strategies. Herein we present a study demonstrating a significant rate enhancement of a copper-selective DNA cleaving DNAzyme by both polydopamine (PDA) and gold (Au) nanoparticles (NPs). PDA NPs enhance the reaction through the production of hydrogen peroxide, while for AuNPs the enhancement is aided by the presence of citrate surface moeities, both of which drive the oxidative cleavage of the substrate. A 50-fold enhancement for PDA NPs makes the combination of PDA and DNAzyme suitable for a practical application as a sensitive biosensor for Cu(II) ions. Using DNAzyme deposition onto a gold electrode followed by Polydopamine Assisted DNA Immobilisation (PADI), we achieve a cost-effective, label-free and fast (within 15 min) electrochemical biosensor with a limit of detection of 180 nmol (11 ppm), thus opening a route for the rational design of a new generation of hybrid DNAzyme-based biosensors

Biopolymer‐based Carriers for DNA Vaccine Design

Abstract: Over the last 30 years, genetically engineered DNA has been tested as novel vaccination strategy against various diseases, including human immunodeficiency virus (HIV), hepatitis B, several parasites, and cancers. However, the clinical breakthrough of the technique is confined by the low transfection efficacy and immunogenicity of the employed vaccines. Therefore, carrier materials were designed to prevent the rapid degradation and systemic clearance of DNA in the body. In this context, biopolymers are a particularly promising DNA vaccine carrier platform due to their beneficial biochemical and physical characteristics, including biocompatibility, stability, and low toxicity. This article reviews the applications, fabrication, and modification of biopolymers as carrier medium for genetic vaccines

Biopolymer‐based Carriers for DNA Vaccine Design

Abstract: Over the last 30 years, genetically engineered DNA has been tested as novel vaccination strategy against various diseases, including human immunodeficiency virus (HIV), hepatitis B, several parasites, and cancers. However, the clinical breakthrough of the technique is confined by the low transfection efficacy and immunogenicity of the employed vaccines. Therefore, carrier materials were designed to prevent the rapid degradation and systemic clearance of DNA in the body. In this context, biopolymers are a particularly promising DNA vaccine carrier platform due to their beneficial biochemical and physical characteristics, including biocompatibility, stability, and low toxicity. This article reviews the applications, fabrication, and modification of biopolymers as carrier medium for genetic vaccines

Biofunctionalised bacterial cellulose scaffold supports the patterning and expansion of human embryonic stem cell-derived dopaminergic progenitor cells.

BACKGROUND: Stem cell-based therapies for neurodegenerative diseases like Parkinson's disease are a promising approach in regenerative medicine and are now moving towards early stage clinical trials. However, a number of challenges remain including the ability to grow stem cells in vitro on a 3-dimensional scaffold, as well as their loss, by leakage or cell death, post-implantation. These issues could, however, be helped through the use of scaffolds that support the growth and differentiation of stem cells both in vitro and in vivo. The present study focuses on the use of bacterial cellulose as an in vitro scaffold to promote the growth of different stem cell-derived cell types. Bacterial cellulose was used because of its remarkable properties such as its wettability, ability to retain water and low stiffness, all of which is similar to that found in brain tissue. METHODS: We cultured human embryonic stem cell-derived progenitor cells on bacterial cellulose with growth factors that were covalently functionalised to the surface via silanisation. Epifluorescence microscopy and immunofluorescence were used to detect the differentiation of stem cells into dopaminergic ventral midbrain progenitor cells. We then quantified the proportion of cells that differentiated into progenitor cells and compared the effect of growing cells on biofunctionalised cellulose versus standard cellulose. RESULTS: We show that the covalent functionalisation of bacterial cellulose sheets with bioactive peptides improves the growth and differentiation of human pluripotent stem cells into dopaminergic neuronal progenitors. CONCLUSIONS: This study suggests that the biocompatible material, bacterial cellulose, has potential applications in cell therapy approaches as a means to repair damage to the central nervous system, such as in Parkinson's disease but also in tissue engineering