Now showing 1 - 3 of 3
  • Publication
    Carbon nanohorn modified platinum electrodes for improved immobilisation of enzyme in the design of glutamate biosensors
    (The Royal Society of Chemistry, 2019-07-25) ; ; ;
    Electrochemical enzymatic biosensors are the subject of research due to their potential for in vivo monitoring of glutamate, which is a key neurotransmitter whose concentration is related to healthy brain function. This study reports the use of biocompatible oxidised carbon nanohorns (o-CNH) with a high surface area, to enhance the immobilization of glutamate oxidase (GluOx) for improved biosensor performance. Two families of biosensors were designed to interact with the anionic GluOx. Family-1 consists of covalently functionalised o-CNH possessing hydrazide (HYZ) and amine (PEG-NH2) terminated surfaces and Family-2 comprised non-covalently functionalised o-CNH with different loadings of polyethyleneimine (PEI) to form a cationic hybrid. Amperometric detection of H2O2 formed by enzymatic oxidation of glutamate revealed a good performance from all designs with the most improved performance by the PEI hybrid systems. The best response was from a o-CNH:PEI ratio of 1:10 mg mL-1, which yielded a glutamate calibration plateau, JMAX, of 55 ± 9 μA cm-2 and sensitivity of 111 ± 34 μA mM-1 cm-2. The low KM of 0.31 ± 0.05 mM indicated the retention of the enzyme function, and a limit of detection of 0.02 ± 0.004 μM and a response time of 0.88 ± 0.13 s was determined. The results demonstrate the high sensitivity of these biosensors and their potential for future use for the detection of glutamate in vivo.
      354Scopus© Citations 15
  • Publication
    Long-Lived Excited-State Dynamics of i-Motif Structures Probed by Time-Resolved Infrared Spectroscopy
    UV-generated excited states of cytosine (C) nucleobases are precursors to mutagenic photoproduct formation. The i-motif formed from C-rich sequences is known to exhibit high yields of long-lived excited states following UV absorption. Here the excited states of several i-motif structures have been characterized following 267 nm laser excitation using time-resolved infrared spectroscopy (TRIR). All structures possess a long-lived excited state of ∼300 ps and notably in some cases decays greater than 1 ns are observed. These unusually long-lived lifetimes are attributed to the interdigitated DNA structure which prevents direct base stacking overlap.
      138Scopus© Citations 14
  • Publication
    Multimodal Microscopy Distinguishes Extracellular Aggregation and Cellular Uptake of Single-Walled Carbon Nanohorns
    The low toxicity, high surface area, and ease of functionalisation of carbon nanohorns (CNH) makes them attractive systems for cellular imaging, diagnostics and therapeutics. However, challenges remain for the biomedical translation of these and other nanomaterials. A significant task is tuning the surface chemistry to achieve optimal cellular interactions. Herein, we combine real-time fluorescent imaging of nanoparticle cellular uptake and real-time differential interference contrast (DIC) imaging of extracellular media to monitor a) nanoparticle/nanoparticle and b) nanoparticle/cell interactions for CNHs covalently modified with an OFF/ON near-IR dye, the fluorescence of which is switched OFF in extracellular environments and triggered upon cellular internalisation. CHN samples modified with different loadings of the hydrophobic dye are taken as a simple model of drug-loaded nanoparticle systems. The punctate fluorescence suggests the CNHs are delivered to lysosomes and other vesicles of the endocytic pathway. DIC imaging highlights the competition that exists for many particle types, between extracellular aggregation and cellular internalization, the efficiency of which would be dependent upon the amount of fluorophore loading. The results of this study illustrate how complementary real-time imaging methods together with physicochemical characterisation can be used to address the challenges involved in optimising nanoparticle/cell interactions for biomedical applications.
      407Scopus© Citations 6