Ball pen writing-without-ink: a truly simple and accessible method for sensitivity enhancement in lateral flow assays

A ball pen writing-without-ink method was developed to amplify the detection signal of LFAs through controlling fluid flow rate.

The Effect of Object Geometric Features on Frequency Inflection Point of Underwater Active Electrolocation System

Biologists have discovered a kind of weakly electric fish that identifies its prey by using active electrolocation in virtual darkness. In this study, we built an underwater active electrolocation system platform designed to investigate the biological mechanism allowing these fish to distinguish objects and determine how the amplitude information-frequency characteristic (AIFC) response are affected by the geometric characteristics of target objects in the active electrolocation system. We used a single-frequency sinusoidal signal to scan metal objects in different orientations and observed the amplitude information response variation of the disturbed detection signal. The detection frequency dead zone (DFDZ) and the frequency inflection point (FIP) were used to characterize the variation. In addition, we repeated the experiments after replacing the metal objects with objects of different materials and geometric characteristics to summarize the general laws. Our results showed that the FIP value of the detection signal was lowest when the object was detected in the orientation of its corner and highest when the object was detected in the orientation of its surface. The geometrical characteristics of metal objects in different orientations have a certain influence on the amplitude of the detection signal. Article Highlights: (1) The general law between the shape of metal probed objects, and electric field detection signal was found and summarized. (2) We used a single-frequency sinusoidal signal to scan regular metal probed objects, and it was found that the frequency inflection point (FIP) of the metal probed objects edge was the highest, whereas that of the corner was the lowest. (3) The shape of a metal object can be recognized by scanning regular metal objects with an electric field signal.

Multi-carbon dots and aptamer based signal amplification ratiometric fluorescence probe for protein tyrosine kinase 7 detection

Background Protein tyrosine kinase 7 (PTK 7) is a membrane receptor, which can be found in various kinds of cancers. In view of this, detection of PTK 7 in the peripheral circulation would be an effective way for the early diagnosis of cancer. Results In this work, a multi-carbon dots and aptamer-based signal amplification ratiometric fluorescence probe was developed. The fluorescence of the aptamer-modified y-CDs and b-CDs were respectively chosen as the detection signal and interior label. The fluorescence of y-CDs was quenched by Fe3O4 and cDNA (complement to aptamer) compound without PTK 7, but recovered by the addition of PTK 7. Then, the free aptamer was cut by DNase I, which amplified the detection signal. The ratiometric fluorescence sensor for PTK 7 was established with the LOD of 0.016 ng mL−1. Conclusions Summary, a multi-carbon dots and aptamer-based signal amplification ratiometric fluorescence probe was developed for the detection of protein tyrosine kinase 7. The developed probe was applied to PTK 7 detection in MCF-7 cells and human serum with satisfying results, thus indicating that this probe has huge potential in clinical practice.

Enzyme Linked Immunosorbent Assay (ELISA) Technique Guideline

ELISA (Enzyme-linked immunosorbent assay) is a technique used to assess the quantification of peptide, protein, antibody and hormone levels, based on the principle of antigen-antibody binding. In the ELISA technique, antigen immobilization will be carried out on a solid surface, then bound with antibodies to form an antigen-antibody bond complex, where the antigen-antibody complex is bound to the enzyme. The detection signal in the form of a color change will be formed due to the reaction between the enzyme and the substrate.