Glucose oxidase immobilized on magnetic nanoparticles: Nanobiosensors for fluorescent glucose monitoring
The authors describe enzyme based nanobiosensors for continuous monitoring of glucose, with the long term goal of using them as smart diagnostic tattoos. The method is founded on two main features: (1) The fluorescence intensity and decay times of glucose oxidase (GOx) and of GOx labeled with fluorescein (FS) or a ruthenium chelate (Ru) reversibly change during interaction with glucose; (2) The (labeled) enzyme is linked to magnetite magnetic nanoparticles (MNPs) which permits the MNPs to be physically manipulated. It is found that a stable link between MNPs and GOx is only accomplished if the number of amino groups on the GOX is artificially enlarged (to form GOxsam). Fluorescence decay data are best acquired with 8-nm MNPs where scattering is marginal; The activity of GOx is found not to be affected by immobilization on the MNPs. The various immobilized enzymes (GOxsam, GOxsam-FS and GOxsam-Ru; all on MNPs) differ only slightly in terms of linear response to glucose which ranged from 0.5 mM to at least 3.5 mM. The RSDs are about 5% (for n = 5), the detection limits are at ∼50 μM, and the sensor lifetimes are >1 week.
KeywordsBiosensors Fluorescence Nanomaterials Lifetime Labelling Magnetite Ruthenium label Fluorescein label Enzyme activity Smart tattoo
The authors thank the MINECO of Spain (CTQ2012-34774 and CTQ2012-35535), the ERC-starting Grant NANOPUZZLE and DGA-FEDER funding to Research Groups (E74, T08 and E93). M del Barrio thanks the CSIC for the funding for her PhD (JAE-Pre contract).
Compliance with ethical standards
The author(s) declare that they have no competing interests.
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