of a photocrosslinked diacrylate-modified peg hydrogel containing the tetra-rhodamine (tritc), labelled fret competitor betacyclodextrin and the quantum dot-labelled apoenzyme concanavalin a. this sensor was tested only in vitro for functionality; however, some tests were done to see the compatibility of the fibre implanted transdermally in mice. in particular, the inflammation was monitored and the energy required to remove it by force was measured proving that the collagen-coated fibre required more force than to remove a hair, which has the same diameter (200μl). another fibre-based sensor was done in singaram lab (santa cruz). this used a 2-hydroxyethyl methacrylate hydrogel as a scaffold onto which two dyes were attached one a fluorescent anionic dye and a cationic quencher (to be specific, a viologen) functionalized with boronic acid, which assumes a negative charge when bound to glucose, making the net charge of the molecule neutral and less attracted to the fluorophore, hence modulating its intensity based on glucose concentration. the majority of hydrogels are attached to the fibre, one exception being the fibre optic-based sensor made by itsubayashi's group to measure glucose in fish (health indicator), which used a dialysis membrane as the support for the hydrogel. to be more specific, it relied on a gox oxygen-ruthenium quenching assay where the protein was mixed with awp (azide-functionalized polyvinyl alcohol, a photocrosslinkable polymer) and cross-linked to a dialysis membrane that was rolled around a premade ruthenium oxygen probe (ocean optics) and inserted into an 18-gauge needle with eight holes on the side (akin to a recorder). in such a set-up, the integrity of the protein has no effect on the sensor, unless below a certain concentration. as a consequence, the destruction or inaccessibility of a fraction of the protein is not problematic, which is in contrast to fret or environmentally sensitive sensing. however, the response speed of this sensor is slow and requires a mathematical prediction to be applied to the measurement. an alternative use of boronic acid in hydrogels is seen in stokke in norway where the swelling of a boronate functionalized acrylamide gel due to charge change upon glucose binding is measured by a fabry–pérot interferometer on the other end of the fibre (note that this a different method than fluorescence and relies on scattering). an exception to the usage of placing the optic fibre transdermally is seen in the previously mentioned fibre from ingo klimant's group (ruthenium-quenching by oxygen released by glucose-catalysed gox): the sensor, in fact, was constructed by functionalizing a premade oxygen sensor with glucose oxydase and inserting it into a glucose-sensing apparatus for amperometric sensors, in particular, a microdialysis catheter cma 60 implanted transdermally and the sensor connected to its tygon tubing. this sensor was tested in a human volunteer and showed results par with current amperometric systems. the usage of a fibre was dictated by the pre-availability of this compared to a ruthenium-coated lens, which would have had achieved the same results, so this approach should be put in a category of its own alongside transdermal fibres and smart tattoos. however, the aim of the group is to create glucose-sensitive nanoparticles to be interrogated with a transdermal optic fibre and controlled magnetically. as a consequence, the group is improving the oxygen sensing probe by investigating novel oxygen sensitive phosphorescent materials, nanoparticle formulation and the creation of magnetic nanoparticles.