A Stimuli-Responsive Biosensor of Glucose on Layer-by-Layer Films Assembled through Specific Lectin-Glycoenzyme Recognition

Integrating machine learning and electrochemistry to develop a glucose biosensor assembled with Ganoderma applanatum lectin

Fungal lectins have enormous biotechnological potential, but limited knowledge about their biochemical and biophysical features prevents their proper use. Herein, we report an innovative alternative to use Ganoderma applanatum lectin (GAL) as a glucose biorecognition element, after identifying the ideal electroanalytical conditions by machine learning studies performed with a homologous agglutinin from the same macrofungus. The research revealed that GAL has moderate resistance to pH (4-8) and temperature (20-60 °C) variations, but its hemagglutinating activity (376.5 HU mg^-1 GAL at 20 °C) was better conserved under physiological conditions. Integrating electrochemical data and semi-empirical molecular modeling, biocompatible and electrostatically favorable conditions were found to immobilize the lectin on Prussian blue-modified glassy carbon electrode, after thermal activation of the metal-complex film. The glucose dose-response relationship obtained with the developed biosensor, defined as GAL/ta-PB/GCE, showed a typical Hill equation correlation, suggesting electrodic interactions represented by a sigmoidal mathematical function. GAL/ta-PB/GCE achieved remarkable electroanalytical performance, with emphasis on the detection limit (10.2 pM) and sensitivity (0.012 µA µM^-1cm^-2). The biosensor was successfully used to quantify glucose in pharmaceutical formulations, reiterating that the association of theoretical and experimental information drives important advances in bioelectrochemical studies.

Design of Switchable Enzyme Carriers Based on Stimuli-Responsive Porous Polymer Membranes for Bioapplications

Design of efficient enzyme carriers, where enzymes are conjugated to supports, has become an attractive research avenue. Immobilized enzymes are advantageous for practical applications because of their convenience in handling, ease of separation, and good reusability. However, the main challenge is that these traditional enzyme carriers are unable to regulate the enzymolysis efficiency or to protect the enzymes from proteolytic degradation, which restricts their effectiveness of enzymes in bioapplications. Enlightened by the stimuli-responsive channels in the natural cell membranes, conjugation of the enzymes within flat-sheet stimuli-responsive porous polymer membranes (SR-PPMs) as artificial cell membranes is an efficient strategy for circumventing this challenge. Controlled by the external stimuli, the multifunctional polymer chains, which are incorporated within the membranes and attached to the enzyme, change their structures to defend the enzyme from the external environmental disturbances and degradation by proteinases. Specifically, smart SR-PPM enzyme carriers (SR-PPMECs) not only permit convective substrate transfer through the accessible porous network, dramatically improving enzymolysis efficiency due to the adjustable pore sizes and the confinement effect, but they also act as molecular switches for regulating its permeability and selectivity. In this review, the concept of SR-PPMECs is presented. It covers the latest developments in design strategies of flat-sheet SR-PPFMs, fabrication protocols of SR-PPFMECs, strategies for the regulation of enzymolysis efficiency, and their cutting-edge bioapplications.

Lignin nanoparticles are renewable and functional platforms for the concanavalin a oriented immobilization of glucose oxidase-peroxidase in cascade bio-sensing

Lignin nanoparticles (LNPs) acted as a renewable and efficient platform for the immobilization of horseradish peroxidase (HRP) and glucose oxidase (GOX) by a layer by layer procedure. The use of concanavalin A as a molecular spacer ensured the correct orientation and distance between the two enzymes as confirmed by Förster resonance energy transfer measurement. Layers with different chemo–physical properties tuned in a different way the activity and kinetic parameters of the enzymatic cascade, with cationic lignin performing as the best polyelectrolyte in the retention of the optimal Con A aggregation state. Electrochemical properties, temperature and pH stability, and reusability of the novel systems have been studied, as well as their capacity to perform as colorimetric biosensors in the detection of glucose using ABTS and dopamine as chromogenic substrates. A boosting effect of LNPs was observed during cyclovoltammetry analysis. The limit of detection (LOD) was found to be better than, or comparable to, that previously reported for other HRP–GOX immobilized systems, the best results being again obtained in the presence of a cationic lignin polyelectrolyte. Thus renewable lignin platforms worked as smart and functional devices for the preparation of green biosensors in the detection of glucose.

Lignin nanoparticles as functional renewable nanoplatform for the immobilization of cascade process in colorimetric biosensing of β-d-glucose.

Nanoparticle-supported temperature responsive polymer brushes for affinity separation of histidine-tagged recombinant proteins

We developed a modular approach for the preparation of nanoparticle-supported polymer brushes carrying repeating iminodiacetate units for affinity separation of histidine-tagged recombinant proteins. The nanoparticle-supported polymer brushes were prepared via the combination of surface-initiated atom transfer radical polymerization with Cu(I)-catalyzed azide-alkyne cycloaddition reaction. The nanocomposite materials were characterized to determine the particle size, morphology, organic content, densities of polymer chains and the affinity ligand. Protein binding assay illustrated that the iminodiacetate-rich polymer brushes enable to selectively bind histidine-tagged recombinant proteins in the presence of abundant interfering proteins. More importantly, the protein binding capacity can be tuned by adjusting the environmental temperature. STATEMENT OF SIGNIFICANCE: The nanoparticle core-polymer brush structure enables selective binding of histidine-tagged recombinant proteins via multiple metal-coordination interactions. The soft and flexible structure of the polymer brushes was found beneficial for lowering the steric hindrance in protein binding. Taking advantage of the conformational changes of the polymer brushes at different temperatures, it is possible to modulate the protein binding on the nanocomposite by adjusting the environmental temperature. In general, the iminodiacetate-rich core-brush nano adsorbents are attractive for purifying histidine-tagged recombinant proteins practically. The synthetic approach reported here may be expanded to develop other advanced functional materials for applications in various biomedical fields ranging from biosensors to drug delivery.

Coupling Self-Assembly Mechanisms to Fabricate Molecularly and Electrically Responsive Films

Biomacromolecules often possess information to self-assemble through low energy competing interactions which can make self-assembly responsive to environmental cues and can also confer dynamic properties. Here, we coupled self-assembling systems to create biofunctional multilayer films that can be cued to disassemble through either molecular or electrical signals. To create functional multilayers, we: (i) electrodeposited the pH-responsive self-assembling aminopolysaccharide chitosan, (ii) allowed the lectin Concanavalin A (ConA) to bind to the chitosan-coated electrode (presumably through electrostatic interactions), (iii) performed layer-by-layer self-assembly by sequential contacting with glycogen and ConA, and (iv) conferred biological (i.e., enzymatic) function by assembling glycoprotein (i.e., enzymes) to the ConA-terminated multilayer. Because the ConA tetramer dissociates at low pH, this multilayer can be triggered to disassemble by acidification. We demonstrate two approaches to induce acidification: (i) glucose oxidase can induce multilayer disassembly in response to molecular cues, and (ii) anodic reactions can induce multilayer disassembly in response to electrical cues.

Hydrolyzed hexagonal boron nitride/polymer nanocomposites for transparent gas barrier film

A flexible thin gas barrier film formed by layer-by-layer (LBL) assembly has been studied. We propose for the first time that hexagonal boron nitride (h-BN) can be used in LBL assembly. When dispersed in water through sonication-assisted hydrolysis, h-BN develops hydroxyl groups that electrostatically couple with the cationic polymer polydiallyldimethylammonium chloride (PDDA). This process produces hydroxyl-functional h-BN/PDDA nanocomposites. The nanocomposites exhibit well exfoliated and highly ordered h-BN nanosheets, which results in an extremely high visual clarity, with an average transmittance of 99% in the visible spectrum. Moreover, well aligned nanocomposites extend gas diffusion path that reduce water vapor transmission rate to 1.3 × 10^-2 g m^-2 d^-1. The simple and fast LBL process demonstrated here can be applied in many gas barrier applications.

Recent Progress in Electrochemical Biosensors for Glycoproteins

This review provides an overview of recent progress in the development of electrochemical biosensors for glycoproteins. Electrochemical glycoprotein sensors are constructed by combining metal and carbon electrodes with glycoprotein-selective binding elements including antibodies, lectin, phenylboronic acid and molecularly imprinted polymers. A recent trend in the preparation of glycoprotein sensors is the successful use of nanomaterials such as graphene, carbon nanotube, and metal nanoparticles. These nanomaterials are extremely useful for improving the sensitivity of glycoprotein sensors. This review focuses mainly on the protocols for the preparation of glycoprotein sensors and the materials used. Recent improvements in glycoprotein sensors are discussed by grouping the sensors into several categories based on the materials used as recognition elements.