Anti-HRP (full length) polyclonal antibody

As non-invasive biomarkers, exosomes are of great significance to diseases diagnosis. However, sensitive and accurate detection of exosomes still remains technical challenges. Herein, inspired by nature's "one-to-many" concept, we design a biosensor mimicking the cactus with numerous thorns to detect exosomes. The biosensor is composed of CD63 antibodies, resembling the roots of cactus, to capture exosomes, and the exosomes resemble the stems. Cholesterol-labeled DNA (DNA anchor) binding to streptavidin modified horseradish peroxidase (HRP) can insert into exosomes membrane, which seems the thorns. The readout signal is produced through HRP-catalyzed hydrogen peroxide (H2O2) mediated oxidation of 1,4-phenylenediamine (PPD) to form 2,5-diamino-NN'-bis-(p-aminophenyl)-1,4-benzoquinone di-imine (PPDox). The PPDox can quench fluorescence of fluorescein through inner filter effect (IFE), which provides fluorescent signal for exosomes detection. Based on this principle, the obtained exosomes solution is qualitatively and quantitatively analyzed by our biosensor, with the comparison to current standard methods by nanoparticle tracking analysis (NTA) and commercial enzymelinked immunosorbent assay (ELISA) kit. The linear range is from 1.0 x 10(4) to 5.0 x 10(5) particles mu L-1 with the limit of detection 3.40 x 10(3) particles mu L-1 and 3.12 x 10(3) particles mu L-1 for colorimetric and fluorescent assays, respectively. Meanwhile, our biosensor exhibits good selectivity, and can eliminate the interference from proteins. This dual-modal biosensor shows favorable performance towards analytical application in clinic samples, pushing one step further towards practical clinical use.

This work reports for the first time a colorimetric based biosensor using nanocellulose (NC) based supports dropdeposited onto a cellulose paper substrate for glucose detection in point-of-care. For this purpose, microcrystalline cellulose (MCC) samples were oxidized with 2,2,6,6-tetramethylpiperidine-N-oxyl radical (TEMPO), sodium hypochlorite, and potassium bromide, to produce carboxylated NC. For the characterization, we used several methods: TEM, FTIR and conductometric titration. In all samples, the primary alcohol groups were selectively oxidized into carboxyl groups, provided the sodium hypochlorite is added dropwise and the reaction is performed at constant pH 10. Carboxyl- NC was further casted on a cellulose substrate and used as support for glucose oxidase (GOx), horseradish peroxidase (HRP) and 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) reactions, aiming to yield a coloured detection system for glucose. The sensing system was generated by integrating GOx on the carboxyl- NC /cellulose substrate. Upon reaction with glucose, the enzyme produced hydrogen peroxide, which was converted into a blue-coloured product by reaction with HRP and the chromogenic reagent ABTS. The test-strip was calibrated by incubating it in different concentrations of glucose. The colours obtained were further analysed by a suitable image analysis software. Linear response for glucose ranged from 1.5 to 13.0 mM. Overall, this new test-strip used renewable material for glucose determination, which is an advantage when compared to other systems that require more complex technological approaches. Moreover, it was found that carboxyl- NC improved the colour homogeneity of the test-strip and the intrinsic linear response of concentration range.