Repository logo

Browsing by Author "Dhanjai"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Disposable capacitive biosensor for dopamine sensing
    (2020) Dhanjai; Yu, Nancy; Mugo, Samuel
    The present paper reports fabrication of a disposable tyrosinase (Tyr) biosensor for rapid detection of dopamine. Tyr immobilized polyaniline/carbon nanotubes/cellulose nanocrystals (Tyr@PANI/CNTs/CNC) conductive film was fabricated on polyvinyl acetate (PVA) transparency and characterized by scanning electron microscopy (SEM) and cyclic voltammetry (CV). Tyr catalyzed dopamine oxidation to o-dopaquinone was analysed by CV and capacitance was recorded. PANI/CNTs/CNC film acted as a suitable enzyme support which also showed its synergistic effect in accelerating the biocatalytic oxidation reaction. Tyr biosensor exhibited excellent reproducibility, and specificity towards dopamine with correlation coefficient (R2) of 0.9508 and limit of detection (LOD) of 1.57 nM within linear concentration range of 7–1000 mM. The study suggested practical utilization of disposable biosensor towards dopamine detection in biological fluids.
  • Thumbnail Image
    Item
    Modified stainless steel microneedle electrode for polyphenolics detection
    (2020) Dhanjai; Mugo, Samuel; Lu, Weihao
    This work outlines a simple fabricated microneedle electrode for sensitive and real sample monitoring of plant polyphenolics. The electrode was fabricated by layer-by-layer assembly (LBL) with nanocomposite of carbon nanotubes (CNT) and cellulose nanocrystals (CNC) as the first layer, followed by polyaniline (PANI), and finally, the 3-(glycidyloxypropyl) trimethoxysilane (GOPS) layer as the binding agent. The microneedle electrodes were characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), Fourier transform infrared (FTIR) spectroscopy, and Raman spectroscopy. The developed microneedle electrodes were successfully applied for the capacitive detection of gallic acid (GA) and chlorogenic acid (CA) as polyphenol model compounds. The microneedle electrode was also used to quantify polyphenols in orange juice. The electrochemical capacitance responses were linearly proportional to the concentrations of GA and CA in the range of 0.1–87.23 μg/mL for GA and 0.1–78.01 μg/mL for CA. The calculated detection limits (LOD) for GA and CA were found to be 0.29 ± 0.2 μg/mL and 0.34 ± 0.2 μg/mL respectively. As minimally invasive technology, microneedle electrodes were found to be promising for successful in situ screening of antioxidants in different fruit matrices. The microneedle electrodes were also applied to the depth profiling of antioxidant content in fruit samples.
  • Thumbnail Image
    Item
    Polymer hydrogel interfaces in electrochemical sensing strategies: a review
    (2019) Dhanjai; Sinha, A.; Kalambate, P. K.; Mugo, Samuel; Kamau, P.; Chen, J.; Jain, R.
    Hydrogels are hydrophilic polymeric networks prepared by physical or chemical cross-linking of gelator molecules under optimum conditions. Being sensitive to external stimuli, hydrogels are integrated into signal transduction systems for generating possible responses upon interaction with target analytes to study various physiochemical/biochemical molecular recognition processes. In recent times, polymer based hydrogel materials have emerged as unique electrode modifying materials providing highly permeable matrix for easy diffusion of analytes and rapid electron transport. Polymeric architectures of hydrogels can accommodate different nanomaterials within its matrix through suitable interactions to form hydrogel nanocomposites. Further, high biocompatibility of hydrogels facilitates facile encapsulation and cross-linking of bioreceptors (eg. nucleic acid, protein) into polymer matrix and helps to retain their bioactivity during practical applications. Polymer hydrogel materials enable easy prototyping of electrodes using novel printing technologies for designing next generation advanced, flexible and portable bioelectronics with excellent sensing performances. The present article focuses on the implication of polymer hydrogels as high performance electrode materials. Taking relevant examples, nanomaterials incorporated polymer hydrogel based chemical sensors and bioreceptors embedded biosensors have been discussed for electrochemical detection of different analytes. Preparation of hydrogel modified electrodes and state-of-the-art sensing mechanisms have been briefly emphasized. Concluding remarks and future prospects regarding fabrication of hydrogel based smart electronics have been provided at the end.