Electrochemical Tracing of Butein Using Carbon Nanoparticles Interfaced Electrode Processed from Biowaste

β-Cyclodextrin-Tethered Butein, a Greener Redox-Active Biomaterial for Electrochemical Enzymatic Sensing of Sialic Acid

Biocompatible, industrially scalable, and opto/electrochemically active biomaterials are promising for biosensor platform design and application. Herein, cyclic oligosaccharide, β-cyclodextrin (BCD), is conjugated with Butein, a chalcone-type polyphenol, via dehydration reaction of the hydroxyl groups of BCD and the benzoyl ring of Butein. Functional group changes in the conjugated BCD-Butein were comprehensively studied using UV-visible absorbance, Fourier transform-infrared, and X-ray photoelectron spectroscopic techniques. The electrochemical characteristics of BCD-Butein were explored using cyclic voltammetry, showing the reversible redox behavior (2e-/2H+) attributed to the catecholic OH group of Butein. The BCD-Butein-modified electrode exhibits a surface-confined redox process (R2 = 0.99, Ipa and Ipc) at the interface, suitable for external mediatorless sensor studies. An enzymatic biomolecular sensor has been constructed using BCD-Butein-modified glassy carbon and a screen-printed electrode targeting sialic acid as the model clinical biomarker. With the enzyme sialic acid aldolase, BCD-Butein-modified substrate exhibited a selective conversion of sialic acid to N-acetyl-d-mannosamine and pyruvate, with a wide linear detection range (1-100 nM), the lowest detection limit of 0.2 nM, and a quantification limit of 0.69 nM, convenient for clinical threshold diagnosis.

Bioadhesive Gauze Embedded with Chitosan-Butein Bioconjugate: A Redox-Active pH Sensor Platform

With the ever-growing global wound care market, demand for robust redox-active healthcare material is obvious for the construction of wearable sensor platforms. Surface reactive functional group-rich material like chitosan holds huge potential for electrochemical biosensor application. Herein, a metal-free redox-active chitosan-butein (CSB) bioconjugate is processed into epidermal bioadhesive electrode material useful for pH sensors promising toward wound site analysis. A two-electrode system devised for conducting carbon-reinforced silver chloride paste and CSB-modified carbon/silver chloride matrix was used as a reference and working electrodes, respectively. Dimensions of working and reference electrodes (4 mm) were designed by 2D cutter plotter-assisted stenciling. The cross-sectional topology of the constructed adhesive CSB-sensor platform exhibits an average surface thickness of 183 ± 2 μm. Cyclic voltammetric analysis revealed the inherent 2e^-/2H⁺ transfer attributed to the catechol OH groups of graft polymerized CSB modified on adhesive gauze. As-fabricated modified electrode substrates exhibit distinguishable potential differences with respect to electrolytes of varied pH (between 5 to 9), promising for wound site analysis.

Comparative investigation of bioflavonoid electrocatalysis in 1D, 2D, and 3D carbon nanomaterials for simultaneous detection of naringin and hesperidin in fruits

Electrocatalysis of bioflavonoids in carbon nanomaterials plays an important role in electrochemical sensors for the detection of their content in fruits. In this study, three types of carbon nanomaterials with 1D, 2D, and 3D structures, namely carbon nanotubes (CNTs), graphene oxide (GO), and Ketjen black (KB), were modified onto glassy carbon electrodes for the electrocatalysis of hesperidin and naringin, which are two important bioflavonoids in fruits. As a result, the CNT-modified electrodes showed the highest electrocatalytic activity for both hesperidin and naringin compared to GO and KB. The morphology and surface chemistry of the carbon nanomaterials were characterized. The structural defects and carbon status of carbon nanomaterials are proposed to be the most important factors affecting the electrocatalysis of hesperidin and naringin. Finally, a CNT-based electrochemical sensor was fabricated to simultaneously detect hesperidin and naringin. Real sample tests on the fruit extract of Citrus grandis "Tomentosa" show that the proposed electrochemical sensors with high recovery thus could be employed in practical applications.

Chitosan grafted butein: A metal-free transducer for electrochemical genosensing of exosomal CD24

Metal-free cost-efficient biocompatible molecules are beneficial for opto-electrochemical bioassays. Herein, chitosan (CS) conjugated butein is prepared via graft polymerization. Structural integrity between radical active sites of CS and its probable conjugation routes with reactive OH group of butein during grafting were comprehensively studied using optical absorbance/emission property, NMR, FT-IR and XPS analysis. Fluorescence emission of CS-conjugated butein (CSB) was studied in dried flaky state as well as in drop casted form. Cyclic voltammetric study of CSB modified glassy carbon electrode exhibits 2e^-/2H⁺ transfer reaction in phosphate buffered saline electrolyte following a surface-confined process with a correlation coefficient of 0.99. Unlike pristine butein, CSB modified electrode display a highly reversible redox behavior under various pH ranging from 4 to 9. For the proof-of-concept CSB-modified flexible screen printed electrodes were processed for electrochemical biosensing of exosomal CD24 specific nucleic acid at an ultralow sample concentration, promising for ovarian cancer diagnosis.

Mesoporous carbon nanospheres derived from agro-waste as novel antimicrobial agents against gram-negative bacteria

Porous carbon nanospheres were synthesized from agro-waste garlic peels by a one-pot facile and easy to scale-up pyrolysis method. Surface morphology and structural features of the nanospheres have been studied by field emission scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, and Raman spectroscopy. Fourier transform infrared spectroscopy (FTIR) and N₂ adsorption desorption experiments were explored to detect surface functionality, surface area, and porosity. Average particle diameter of the synthesized nanospheres was 31 ± 6.3 nm and zeta potential of - 25.2 mV ± 1.75 mV. Nanoscale carbon was mesoporous in nature with type IV isotherms, mean pore diameter of 15.2 nm, and total pore volume of 0.032 cm³/g. Minimum inhibitory concentration and minimum bactericidal concentration values of carbon nanospheres against Escherichia coli are 480 ± 0.5 μg/ml and 495 ± 0.5 μg/ml, respectively. Synthesized nanospheres exhibited gram-selective antimicrobial action against Escherichia coli probably linked to membrane deformity due to interaction of nanocarbon with the bacterial membrane. Carbon nanospheres resulting from waste to wealth transformation emerged as promising candidates for antibacterial application. Graphical abstract.

Unique Host Matrix to Disperse Pd Nanoparticles for Electrochemical Sensing of Morin: Sustainable Engineering Approach

Biomass-based carbon nanospheres derived from Mimosa pudica (commonly called "Touch-me-not") smeared on carbon fiber paper have been used as a host matrix for electrochemical deposition of palladium nanoparticles. The physicochemical characterization of modified electrodes was performed by field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy techniques. Cyclic voltammetry and electrochemical impedance spectroscopy were used to study the electroanalytical properties of the electrodes. The modified electrode demostrated an excellent electrocatalytic activity for the oxidation of a flavonoid, morin, which gave a sensitive anodic peak at -0.30 V (vs SCE). An ultralow-level detection limit of 572 fM with a linear dynamic range of 37.50-130 pM was achieved. The proposed electrochemical sensor was successfully employed for the analysis of morin in mulberry and guava leaves. This is a sustainable engineering approach where a perfect unique host matrix is created using carbon nanospheres from biomass.