Dual-mode upconversion sensors for detecting differently charged biotargets based on the oxidase-mimicking activity of Ce4+ and electrostatic control.

Heparin is a highly negatively charged sulfated linear polymer glycosaminoglycan that has been widely used as an anticoagulant in medicine. Protamine is a cationic protein rich in arginine that is used to treat the blood-brain barrier during excess heparin surgery. Trypsin is the most important digestive enzyme-encoding generated by the pancreas and can specifically cleave the carboxyl ends of arginine and lysine residues. Heparin, protamine, and trypsin interact and constrain each other, and their fluctuations reflect the body's dysfunction. Therefore, it is necessary to develop a fast, sensitive, and highly selective assay for regularly monitoring the levels of heparin, protamine, and trypsin in serum. Herein, a fluorescent and colorimetric dual-mode upconversion nanoparticle (UCNP) biosensor was used for the determination of heparin, protamine, and trypsin based on the oxidase-mimicking activity of Ce4+ and electrostatic control. The biosensor exhibited sensitive detection of heparin, protamine, and trypsin with low limits of detection (LODs) of 16 ng/mL, 87 ng/mL and 31 ng/mL, respectively. Furthermore, the designed biosensor could eliminate autofluorescence, which not only effectively increased the accuracy of the sensor but also provided a new sensing pathway for the detection of differently charged biotargets.

Sandwich-like voltametric immunosensing of interleukin-8 based on ß-cyclodextrin/carbon nanotubes and methylthionine chloride@UIO-66 framework.

The level of interleukin-8 (IL-8) in the body is an effective factor for the early diagnosis of acute tubular necrosis and oral tumor. In this work, a novel sandwich-like voltametric immunosensor (SVS) of IL-8 was constructed by preparing ß-cyclodextrin/carbon nanotube (CD/CNT) to immobilize primary antibody (PAb) of IL-8 and UIO-66-NH2 MOFs structure to immobilize second antibody (SAb) and methylene blue (Mb) probe. In this designed SVS, the prepared CD/CNT nanohybrid with large surface area and conductivity can immobilize PAb via simple host-guest recognition, and UIO-66-NH2 provided an ideal platform to accommodate SAb and a large number of Mb molecules as signal-amplifier. In the existence of target IL-8, the current peak of Mb from the SVS assay increases with the increasement of IL-8 level. Through optimizing and adjusting various factors, a wide linearity (0.001-2.5 ng mL-1) and low analytical limit (0.2 pg mL-1) of IL-8 were realized, so it's expected the developed SVS strategy has significant applications for the detection of IL-8.