Selected Publications

Flavin-Conjugated Iron Oxide Nanoparticles as Enzyme-Inspired Photocatalysts for Azo Dye Degradation

In this work, a new photocatalytic system consisting of iron oxide nanoparticles (IONPs), coated with a catechol-flavin conjugate (DAFL), is synthesized and explored for use in water remediation. In order to test the efficiency of the catalyst, the photodegradation of amaranth (AMT), an azo dye water pollutant, was performed under aerobic and anaerobic conditions, using either ethylenediaminetetraacetic acid (EDTA) or 2-(N-morpholino)ethanesulfonic acid (MES) as electron donors. Depending on the conditions, either dye photoreduction or photooxidation were observed, indicating that flavin-coated iron-oxide nanoparticles can be used as a versatile enzyme-inspired photocatalysts.

S. I. Nehme, L. B. Crocker, Lj. Fruk, Flavin-Conjugated Iron Oxide Nanoparticles as Enzyme-Inspired Photocatalysts for Azo Dye Degradation, Catalysts 2020, 10(3), 324. LINK

Enzyme-Inspired Flavin-Polydopamine as a Biocompatible Nanoparticle Photocatalys

A new approach aimed at designing an enzyme-inspired photocatalyst is presented that exploits the inherent photocatalytic activity of flavin and the facile polymerization of dopamine to afford hybrid cofactor-containing nanoparticles. The flavin–polydopamine system benefits from ease of synthesis, tunability in terms of size and activity, and excellent temporal control over the catalyzed reactions. This novel, versatile photocatalyst exhibits both photooxidation and photoreduction of chromogenic enzymatic substrates. In addition, the prepared hybrid nanoparticles are shown to be non-toxic, paving the way to their use in a wider range of applications beyond green catalysis, such as antioxidant adjuvants to various therapeutic approaches.

Lj. Fruk, L. B. Crocker, P. Koehler, P. Bernhard, A. Kerbs, T. G. Euser, Enzyme-Inspired Flavin-Polydopamine as a Biocompatible Nanoparticle Photocatalyst, Nanoscale Horiz. 2019

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.

L. B. Crocker, Lj. Fruk, Flavin Conjugated Polydopamine Nanoparticles Displaying Light-Driven Monooxygenase Activity, Front. Chem. 2019, 7, 278

Iron delivery from liquid-core hydrogels within a therapeutic nipple shield

To aid oral therapeutic administration to infants, a novel delivery technology, referred to as a Therapeutic Nipple Shield (TNS), was previously developed. It consists of a silicone nipple shield device and a dosage form containing a therapeutic (or Active Pharmaceutical Ingredient (API)) to enable delivery during breastfeeding. A range of dosage forms were investigated in past literature, but sufficient API release into human milk had not been achieved. The presented work illustrates the delivery of iron sulphate pentahydrate from liquid-core sodium alginate hydrogels, inserted into a commercially available ultra-thin silicone nipple shield into human milk during in-vitro breastfeeding simulation. Release of iron was quantified employing absorbance measurements of a salicylic assay. An absolute recovery of 44.35 ± 5.43% of loaded iron(III)sulphate pentahydrate was obtained after 10.58 ± 0.09 g of human milk had passed through the nipple shield. This finding is superior to previous investigations involving the delivery of zinc from rapidly disintegrating tablets and non-woven fibres within a TNS. Due to their superior delivery properties, ease of fabrication and cost-efficiency, liquid-core sodium alginate hydrogels consequently represent a promising dosage form for use as part of the TNS. Further improvements can be made to enhance handling stability and shelf-life characteristics.

T. Maier, A. Kerbs, Lj. Fruk, N. K. H. Slater, Iron delivery from liquid-core hydrogels within a therapeutic nipple shield, Eur. J. Pharm. Sci. 2019, 131, 119-126.

Photo‐Induced Click Chemistry for DNA Surface Structuring via Direct Laser Writing

Oligonucleotides containing photo‐caged dienes were prepared and shown to react quantitatively in a light‐induced Diels–Alder cycloaddition with functional maleimides in aqueous solution within minutes. Due to its high yield and fast rate, the reaction was exploited for DNA surface patterning with sub‐micrometer resolution employing direct laser writing (DLW). Functional DNA arrays were written by direct laser writing (DLW) in variable patterns, which were further encoded with fluorophores and proteins through DNA directed immobilization. This mild and efficient light‐driven platform technology holds promise for the fabrication of complex bioarrays with sub‐micron resolution.

A. Kerbs, P. Mueller, M. Kaupp, I. Ahmed, A. S. Quick, D. Abt, M. Wegener, C. M. Niemeyer, C. Barner-Kowollik, Lj. Fruk, Photo‐Induced Click Chemistry for DNA Surface Structuring via Direct Laser Writing, Chemistry-A Eur. J. 2017

Photo Induced Chemistry for Design of Oligonucleotide Conjugates and Surfaces

A photocaged diene is introduced at the 5′-end of oligonucleotides using the H-phosphonate approach. The photoenol-functionalized DNA is subsequently employed for the conjugation to a protein and the spatially controlled immobilization onto surfaces using a light-induced Diels–Alder cycloaddition. Fully functional protein–DNA conjugates and patterned DNA surfaces are obtained under mild irradiation conditions.

A. Vigovskaya, D.Abt, I. Ahmed, C. M. Niemeyer, C. Barner-Kowollik, Lj. Fruk, Photo Induced Chemistry for Design of Oligonucleotide Conjugates and Surfaces, J. Mater. Chem. B 2016, 4, 442.

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.

L. Stolzer, A. Vigovskaya, C. Barner-Kowollik, Lj. Fruk, A Self Reporting Tetrazole Based Linker for the Biofunctionalization of Gold Nanorods, Chemistry-A Eur. J. 2015.

BiocompatibleHydrogel Nanocomposite with Covalently Embedded Silver Nanoparticles

Bionanocomposite materials, combining the properties of biopolymers and nanostructured materials, are attracting interest of the wider scientific community due to their potential application in design of implants, drug delivery systems, and tissue design platforms. Herein, we report on the use of maleimide-coated silver nanoparticles (Ag NPs) as cocross-linkers for the preparation of a bionanocomposite gelatin based hydrogel. Diels–Alder cycloaddition of benzotriazole maleimide (BTM) functionalized Ag NPs and furan containing gelatin in combination with additional amide coupling resulted in stable and biocompatible hybrid nanocomposite. The storage moduli values for the hydrogel are nearly three times higher than that of control hydrogel without NPs indicating a stabilizing role of the covalently bound NPs. Finally, the swelling and drug release properties of the materials as well as the biocompatibility and toxicity tests indicate the biomedical potential of this type of material.

C. Garcia-Astrain, C. Chen, M. Buron, T. Palomares, A. Eceiza, Lj. Fruk, M. Angeles Corcuera, N. Gabilondo, Biocompatibl Hydrogel Nanocomposite with Covalently Embedded Silver Nanoparticles, Biomacromolecules 2015, 16(4), 1301

Enhanced Photocatalytic Activity of Au/TiO2 Nanocomposite Prepared Using Bifunctional Bridging Linker

Using a simple bifunctional bridging linker, nanosized gold and titanium dioxide composites are prepared containing different Au loadings. Linker is synthesized to contain both catechol and thiol moieties to enable binding to the TiO2 and Au surface respectively. Au/TiO2 nanocomposites are prepared using simple synthetic route that allows the control over the amount of Au nanoparticles, a property which plays a significant role in the catalytic activity of hybrid materials. Photocatalytic activity of materials prepared using different TiO2 precursors is investigated using reactive oxygen species sensitive assay based on activation of horseradish peroxidase (HRP) enzyme. Significant increase in catalytic activity is observed for all Au/TiO2 nanocomposites with Au/TiO2 prepared by use of the bridging linker being up to 5.5 times more active than bare commercial TiO2 nanoparticles. In addition to 365 nm light excitation, less energetic 470 nm light, which is more suitable for the use with biological systems, is used to induce photocatalytic activity. Finally, prepared photocatalytic materials are successfully used to exert temporal control over enzymatic activity, a feature which is important for the study of both enzymatic activity and design of novel bio‐sensing platforms.

M. Miljevic, B. Geiseler, T. Bergfeldt, P. Brockstaller, Lj. Fruk, Enhanced Photocatalytic Activity of Au/TiO2 Nanocomposite Prepared Using Bifunctional Bridging Linker, Adv. Funct. Mater. 2014, 24(7), 1028.

Reactive Oxygen Species Production by Catechol Stabilized Copper Nanoparticles

Stable Cu nanoparticles (NPs) prepared using catechol containing dopamine-based linkers could generate reactive oxygen species (ROS) that can activate peroxidase enzymes and catalyze the degradation of fluorescent dye pollutants.

C. Cheng, I. Ahmed, Lj. Fruk, Reactive Oxygen Species Production by Catechol Stabilized Copper Nanoparticles, Nanoscale 2013, 11610

Bifunctional Catechol Based Linkers for Modification of TiO2 Surfaces

Bifunctional linkers for modification of TiO2 nanoparticles were prepared containing a catechol group for TiO2 surface attachment and a maleimide and alkyne group for Michael addition and Cu catalysed Huisgen cycloaddition respectively. Peptide and fluorophore functionalised TiO2 NPs were prepared, different purification methodologies were explored and conjugates were characterized using a range of methods.

B. Geiseler, Lj. Fruk, Bifunctional Catechol Based Linkers for Modification of TiO2 Surfaces, J. Mater. Chem. 2012, 22, 735-741

Photoinduced write- once read-many-times memory device based on DNA biopolymer composite

We demonstrate a photoinduced write-once read-many-times (WORM) organic memory device based on DNA biopolymer nanocomposite. The device consists of a single biopolymer layer sandwiched between electrodes, in which electrical bistability is activated by in situ formation of silver nanoparticles embedded in biopolymer upon light irradiation. The device exhibits a switching effect to high conductivity above a threshold of 2.6 V and a good retention property. This facile technique, taking advantage of DNA’s affinity for metals and solution processing, can optically manipulate the properties of DNA nanocomposite thin films, which holds promise for optical storage and plasmonic applications.

Yu-Chueh Hung, Wei-Ting Hsu, Ting-Yu Lin, Lj. Fruk, Photoinduced write- once read-many-times memory device based on DNA biopolymer composite, Appl. Phys. Lett. 2011, 253301

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