A novel nanocomposite matrix based on graphene oxide and ferrocene-branched organically modified sol–gel/chitosan for biosensor application

Extended Release of Metronidazole Drug Using Chitosan/Graphene Oxide Bionanocomposite Beads as the Drug Carrier

This study depicts the facile approach for the synthesis of chitosan/graphene oxide bionanocomposite (Chi/GO) beads via the gelation process. This is the first-ever study in which these Chi/GO beads have been utilized as a drug carrier for the oral drug delivery of metronidazole (MTD) drug, and investigations were made regarding the release pattern of the MTD drug using these Chi/GO beads as a drug carrier for a prolonged period of 84 h. The MTD is loaded on the surface as well as the cavity of the Chi/GO beads to result in MTD-Chi/GO bionanocomposite beads. The MTD drug loading was found to be 683 mg/g. Furthermore, the in vitro release patterns of pure drug and the drug encapsulated with Chi/GO beads are explored in simulated gastric as well as simulated intestinal fluids with phosphate-buffered saline (PBS) of pH 1.2 and 7.4, respectively. As-synthesized bionanocomposite beads have shown excellent stability and capacity for extended release of the MTD drug as compared to the pure drug in terms of bioavailability in both media. The cumulative release data are fitted with the Korsmeyer-Peppas kinetics and first-order reaction kinetics at pH 1.2 and 7.4. The synthesized bionanocomposite beads have good potential to minimize the multiple-dose frequency with the sustained drug release property and can reduce the side effects due to the drug.

Switching the solubility of electroactive ionic liquids for designing high energy supercapacitor and low potential biosensor

Ionic liquids are regarded as one of the most prodigious materials for sustainable technological developments with superior performance and versatility. Hence, in this study, we have reported the design and synthesis of electroactive disubstituted ferrocenyl ionic liquids (Fc-ILs) with two different counter anions and demonstrated the significance of their anion tuneable physicochemical characteristics towards multifunctional electrochemical applications. The Fc-IL synthesized with chloride counter anion (Fc-Cl-IL) displays water-solubility and can be used as a redox additive in the fabrication of supercapacitor. Supercapacitor device with Fc-Cl-IL based redox electrolyte exhibits outstanding energy and power densities of 91 Wh kg^-1 and 20.3 kW kg^-1, respectively. Meanwhile, ferrocenyl IL synthesized with perchlorate anion (Fc-ClO₄-IL) exhibits water-insolubility and can serve as a redox mediator towards construction of a glucose biosensor. The biosensor comprising Fc-ClO₄-IL is able to detect glucose at an exceptionally lower potential of 0.2 V, with remarkable sensitivity and selectivity. This study implies that the introduction of electroactive ILs could afford supercapacitor devices with high energy and power densities and biosensors with less detection potential.

Rheological and Dielectric Behavior of 3D-Printable Chitosan/Graphene Oxide Hydrogels

The effect of concentration, temperature, and the addition of graphene oxide (GO) nanosheets on the rheological and dielectric behavior of chitosan (CS) solutions, which influences the formation of the blend materials for various applications including 3D printing and packaging, was studied. Among tested acid solutions, the rheological behavior of 1% CS in acetic and lactic acid solutions was found to be similar, whereas the hydrochloric acid solution showed an abnormal drop in the dynamic moduli. Oscillatory rheology confirmed a distinct gel point for the CS solutions at below 10 °C. Both the G' and G″ of the solutions increased with the loading concentrations of GO between 0.5 and 1%, and it marginally dropped at the loading concentration of 2%, which is consistent with AFM observation. The steady-shear flow data fitted the Carreau model. Dielectric property measurement further confirmed that both the dielectric constant, ε' and the loss factor, ε″ for the CS in hydrochloric acid solutions behaved differently from others. Addition of GO significantly improved both ε' and ε″, indicating an improvement in the dielectric properties of CS/GO solutions. The dispersion of GO into the CS matrix was assessed by measuring XRD, FTIR, and microscopy of the film prepared from the solutions. Furthermore, the inclusion of GO into CS solution containing pluronic F127 (F127) base for potential 3D printing application showed positive results in terms of the printing accuracy and shape fidelity of the printed objects (films and scaffolds). The optimized composition with homogeneous particle distribution indicated that up to ∼50 mg/mL GO concentration (w/v of F127 base) was suitable to print both films and scaffolds for potential biomedical applications.

Exploration of Chitinous Scaffold-Based Interfaces for Glucose Sensing Assemblies

: The nanomaterial-integrated chitinous polymers have promoted the technological advancements in personal health care apparatus, particularly for enzyme-based devices like the glucometer. Chitin and chitosan, being natural biopolymers, have attracted great attention in the field of biocatalysts engineering. Their remarkable tunable properties have been explored for enhancing enzyme performance and biosensor advancements. Currently, incorporation of nanomaterials in chitin and chitosan-based biosensors are also widely exploited for enzyme stability and interference-free detection. Therefore, in this review, we focus on various innovative multi-faceted strategies used for the fabrication of biological assemblies using chitinous biomaterial interface. We aim to summarize the current development on chitin/chitosan and their nano-architecture scaffolds for interdisciplinary biosensor research, especially for analytes like glucose. This review article will be useful for understanding the overall multifunctional aspects and progress of chitin and chitosan-based polysaccharides in the food, biomedical, pharmaceutical, environmental, and other diverse applications.

Ferrocene-Modified Polyelectrolyte Film-Coated Electrode and Its Application in Glucose Detection

A polyelectrolyte film-coated electrode for the quantitative detection of glucose was reported. Carbon nanotubes, graphene oxide and polyelectrolyte with a ferrocenyl group were used to modify an enzyme electrode to facilitate the electron transfer between glucose oxidase and the electrode. Cyclic voltammetry and amperometric methods were adopted to investigate the effects of different polyelectrolytes and carbon nanomaterials on the electrochemical properties of enzyme electrodes. The results indicate that the ferrocenyl groups on a polyelectrolyte skeleton act as a mediator between the redox center of glucose oxidase and the electrode, which efficiently enhances the electron transfer between a glassy carbon electrode and glucose oxidase. The calibration curve of the sensor shows a linear range from 0.2 to 5 mM for glucose response. The sensor can achieve 95% of the steady-state current within 10 s. The electrodes also present high operational stability and long-term storage stability.

A sandwich-type electrochemical immunosensor for carcinoembryonic antigen based on signal amplification strategy of optimized ferrocene functionalized Fe₃O₄@SiO₂ as labels

A sandwich-type electrochemical immunosensor was developed for sensitive detection of carcinoembryonic antigen (CEA) by using ferroferric oxide@silica-amino groups (Fe3O4@SiO2-NH2) as carriers and gold nanoparticles-graphene oxide (GO-AuNPs) as platform. The Fe3O4@SiO2-NH2 surface was used as linked reagents for co-immobilization of ferrocenecarboxylic acid (Fc-COOH) and secondary anti-CEA (Ab2) to prepare the signal probe, and it also could hasten the decomposition of hydrogen peroxide (H2O2) to amplify signals. Differential pulse voltammetry (DPV) was successfully used to quantify CEA. Under the optimized conditions, the designed immunosensor shows an excellent analytical performance wide dynamic response range of CEA concentration from 0.001 ng mL(-1) to 80 ng mL(-1) with a relatively low detection limit of 0.0002 ng mL(-1) (S/N=3), and high specificity and good reproducibility. The proposed immunosensor was successfully used to determine CEA in spiked human serum samples.

Optimized design of a nanostructured SPCE-based multipurpose biosensing platform formed by ferrocene-tethered electrochemically-deposited cauliflower-shaped gold nanoparticles

The demand for on-site nanodevices is constantly increasing. The technology development for the design of such devices is highly regarded. In this work, we report the design of a disposable platform that is structured with cauliflower-shaped gold nanoparticles (cfAuNPs) and we show its applications in immunosensing and enzyme-based detection. The electrochemical reduction of Au(III) allows for the electrodeposition of highly dispersed cauliflower-shaped gold nanoparticles on the surface of screen-printed carbon electrodes (SPCEs). The nanostructures were functionalized using ferrocenylmethyl lipoic acid ester which allowed for the tethering of the ferrocene group to gold, which serves as an electrochemical transducer/mediator. The bioconjugation of the surface with anti-human IgG antibody (α-hIgG) or horseradish peroxidase (HRP) enzyme yields biosensors, which have been applied for the selective electrochemical detection of human IgG (hIgG) or H2O2 as model analytes, respectively. Parameters such as the number of sweeps, amount of charge generated from the oxidation of the electrodeposited gold, time of incubation and concentration of the ferrocene derivatives have been studied using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Selectivity and specificity tests have been also performed in the presence of potentially interfering substances to either hIgG or H2O2. Results showed that the devised immunosensor is endowed with good selectivity and specificity in the presence of several folds of competitive analytes. The enzyme-based platform showed a good catalytic activity towards H2O2 oxidation which predestined it to potential applications pertaining to enzymatic kinetics studies. The levels of hIgG in human serum and H2O2 in honey were successfully determined and served as assessment tools of the applicability of the platforms for real samples analysis.