Covalent Attachment of Enzymes to Paper Fibers for Paper-Based Analytical Devices

Due to its unique material properties, paper offers many practical advantages as a viable platform for sensing devices. In view of paper-based microfluidic biosensing applications, the covalent immobilization of enzymes with preserved functional activity is highly desirable and ultimately challenging. In the present manuscript, we report an efficient approach to achieving the covalent attachment of certain enzymes on paper fibers via a surface-bound network of hydrophilic polymers bearing protein-modifiable sites. This tailor-made macromolecular system consisting of polar, highly swellable copolymers is anchored to the paper exterior upon light-induced crosslinking of engineered benzophenone motifs. On the other hand, this framework contains active esters that can be efficiently modified by the nucleophiles of biomolecules. This strategy allowed the covalent immobilization of glucose oxidase and horseradish peroxidase onto cotton linters without sacrificing their bioactivities and performance upon surface binding. As a proof-of-concept application, a microfluidic chromatic paper-based glucose sensor was developed and achieved successful glucose detection in a simple yet efficient cascade reaction

Covalent Attachment of Enzymes to Paper Fibers for Paper-Based Analytical Devices

Due to its unique material properties, paper offers many practical advantages as a viable platform for sensing devices. In view of paper-based microfluidic biosensing applications, the covalent immobilization of enzymes with preserved functional activity is highly desirable and ultimately challenging. In the present manuscript, we report an efficient approach to achieving the covalent attachment of certain enzymes on paper fibers via a surface-bound network of hydrophilic polymers bearing protein-modifiable sites. This tailor-made macromolecular system consisting of polar, highly swellable copolymers is anchored to the paper exterior upon light-induced crosslinking of engineered benzophenone motifs. On the other hand, this framework contains active esters that can be efficiently modified by the nucleophiles of biomolecules. This strategy allowed the covalent immobilization of glucose oxidase and horseradish peroxidase onto cotton linters without sacrificing their bioactivities and performance upon surface binding. As a proof-of-concept application, a microfluidic chromatic paper-based glucose sensor was developed and achieved successful glucose detection in a simple yet efficient cascade reaction

Reactivity of Isocyanate-Functionalized Lignins: A Key Factor for the Preparation of Lignin-Based Polyurethanes

Using isocyanate-functionalized Kraft lignin as a reactive macromonomer for the preparation of polyurethane foams by a prepolymer technique is a well-known strategy to incorporate the biomacromolecule into a higher value polymer material. However, as of today the mechanical properties of the resulting materials are still insufficient for a number of possible applications. One reason for this limitation is that the reaction pathway and the morphological arrangement of such foams is of uttermost complexity and depends on a large number of influencing material-intrinsic factors. One important parameter is the reactivity of the functionalized lignin, which has a great impact on the interphase reaction kinetics and thus, on the geometry and mechanical properties of the resulting polyurethane foams. The reactivity is implied, amongst others, by the electron affinity of the isocyanate moiety. Herein, we investigate the reactivity of Kraft lignin modified with different commercially used isocyanates in the reaction with conventional polyols. Therefore, differently reactive prepolymers were synthesized, characterized and polyurethane foams were prepared thereof by using these compounds and the foam formation kinetics, morphological as well as mechanical properties were investigated. Finally, the results were supported by quantum mechanical calculations of the electron affinities of representative model compounds for the lignin-based prepolymers. This work gives rise to a better understanding of the effect of the reactivity and isocyanate structure linked to Kraft lignin on the polyurethane formation and enables rational choice of the isocyanate for pre-functionalization of lignin to prepare materials with better mechanical performance

Synthesis of Highly Functionalized 9,10-Phenanthrenequinones by Oxidative Coupling Using MoCl₅

The strong oxidative power of molybdenum pentachloride gives rise to an efficient oxidative C–C bond formation of benzil derivatives to the corresponding 9,10-phenanthrenequinones. A highly complementary method to previous approaches was developed. The required derivatives are accessible in a modular fashion and in excellent yields. By this approach the orchid-derived natural product cypripediquinone A was synthesized for the first time

Synthesis of Highly Functionalized 9,10-Phenanthrenequinones by Oxidative Coupling Using MoCl₅

The strong oxidative power of molybdenum pentachloride gives rise to an efficient oxidative C–C bond formation of benzil derivatives to the corresponding 9,10-phenanthrenequinones. A highly complementary method to previous approaches was developed. The required derivatives are accessible in a modular fashion and in excellent yields. By this approach the orchid-derived natural product cypripediquinone A was synthesized for the first time

Spatially Resolved Crosslinking of Hydroxypropyl Cellulose Esters for the Generation of Functional Surface-Attached Organogels

Chemistry, geometric shape and swelling behavior are the key parameters that determine any successful use of man-made polymeric networks (gels). While understanding of the swelling behavior of both water-swellable hydrogels and organogels that swell in organic solvents can be considered well-advanced with respect to fossil fuel-based polymer networks, the understanding, in particular, of wood-derived polymers in such a network architecture is still lacking. In this work, we focus on organogels derived from hydroxypropyl cellulose (HPC) ester. The latter polymer was functionalized with saturated and unsaturated fatty acids, respectively. Due to their tailored chemical constitution, we demonstrated that such polysaccharide can be crosslinked and simultaneously surface-bound by using a photo-induced radical reaction using a photo-initiator. Based on the choice of fatty acid used in the design of the HPC ester, and by controlling the degree of substitution (DS) obtained during the esterification of the polysaccharide, modular manipulation of the physical properties (e.g., polarity) of the resulting gel is possible. Depending on the initiator employed, different wavelengths of light, from UV to visible, can be utilized for the crosslinking reaction, which facilitates the deployment of a range of light sources and different lithographic methods. Additionally, we showed that altering of the illumination time allows to tailor the netpoint density, and thus, the degree of linear deformation in equilibrium and the swelling kinetics. Finally, we performed a proof-of-principle experiment to demonstrate the application of our material for the generation of spatially resolved polymer patches to enrich organic molecules from a solution within a microfluidic channel