A low-cost, simple, portable and sensitive paper-based electrochemical sensor was established for the detection of K-562 cell in point-of-care testing. The hybrid material of 3D Au nanoparticles/graphene (3D Au NPs/GN) with high specific surface area and ionic liquid (IL) with widened electrochemical windows improved the good biocompatibility and high conductivity was modified on paper working electrode (PWE) by the classic assembly method and then employed as the sensing surface. IL could not only enhance the electron transfer ability but also provide sensing recognition interface for the conjugation of Con A with cells, with the cell capture efficiency and the sensitivity of biosensor strengthened simultaneously. Concanavalin A (Con A) immobilization matrix was used to capture cells. As proof-of-concept, the paper-based electrochemical sensor for the detection of K-562 cells was developed. With such sandwich-type assay format, K-562 cells as model cells were captured on the surface of Con A/IL/3D AuNPs@GN/PWE. Con A-labeled dendritic PdAg NPs were captured on the surface of K-562 cells. Such dendritic PdAg NPs worked as catalysts promoting the oxidation of thionine (TH) by H 2 O 2 which was released from K-562 cells via the stimulation of phorbol 12-myristate-13-acetate (PMA). Therefore, the current signal response was dependent on the amount of PdAg NPs and the concentration of H 2 O 2 , the latter of which corresponded with the releasing amount from cells. So, the detection method of K-562 cell was also developed. Under optimized experimental conditions, 1.5×10 −14 mol of H 2 O 2 releasing from each cell was calculated. The linear range and the detection limit for K-562 cells were determined to be 1.0×10 3 –5.0×10 6 cells/mL and 200 cells/mL, respectively. Such as-prepared sensor showed excellent analytical performance with good fabrication reproducibility, acceptable precision and satisfied accuracy, providing a novel protocol in point-of-care testing of cells.
A trimetallic dendritic Au@PdPt nanparticles (Au@PdPt NPs) with intrinsic peroxidase-like catalytic activity were fabricated by a facile method. Au@PdPt NPs catalyzed the reduction of H 2 O 2 with the help of the electron mediator (thionine), which produced the electrochemical signals dramatically amplified. A sandwiched sensor was designed and implemented in the paper chip device for the determination of K-562 cells. The surface of dendritic Au@PtPd NPs was linked with folic acid by click chemistry. Folic acid was attached to the folate receptor (FR) of cell surface with high affinity. So, K-562 cells could be assayed based on folic acid-functionalized Au@PtPd NPs. On the other hand, folic acid-functionalized Au-paper working electrode on origami electrochemical device was fabricated, which could be used to capture K-562 cells. The twice utilization of folic acid for the capture of K-562 cells as well as the attachment of dendritic Au@PtPd NPs nanoprobe, which enhanced the selectivity of sensor for the determination of cells. The proposed biosensor exhibited excellent analytical performance toward the cytosensing of K562 cells with a wide detection linear range from 1.0 × 10 2 to 2.0 × 10 7 cells mL −1 and a detection limit of 31 cells mL −1 . Further, the proposed electrochemical sensor was applied to monitor cells. Au@PtPd NPs nonenzymatic catalysts could be used as signal-amplifying nanoprobes for ultrasensitive electrochemical sensing.
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