Single Molecule Analysis of Self-Assembly Supramolecular Oligomers in Solution

Ultrafast Subcellular Biolabeling and Bioresponsive Real-Time Monitoring for Targeting Cancer Theranostics

Cell heterogeneity poses a formidable challenge for tumor theranostics, requiring high-resolution strategies for intercellular bioanalysis between single cells. Nanoelectrode-based electrochemical analysis has attracted much attention due to its advantages of label-free characteristics, relatively low cost, and ultra-high resolution for single-cell analysis. Here, we have designed and developed a subcellular biolabeling and bioresponsive real-time monitoring strategy for precise bioimaging-guided cancer diagnosis and theranostics. Our observations revealed the apparent intracellular migration of biosynthetic Au nanoclusters (Au NCs) at different subcellular locations, i.e., from the mitochondria to the mitochondrion-free region in the cytoplasm, which may be helpful for controlling over the biosynthesis of Au NCs. Considering the precise biolabeling advantage of the intracellular biosynthetic Au NCs for biomedical imaging of cancers, it is important to realize the biosynthetic Au NC-enabled precise control in real-time theranostics of cancer cells. Therefore, this work raises the possibility to achieve subcellular monitoring of H2O2 for targeting cancer theranostics, thereby providing a new way to explore the underlying mechanism and imaging-guided tumor theranostics.

Current Simultaneous Discrimination of Mismatched MicroRNAs Using Base-Flipping within the α-Hemolysin Latch

The simultaneous discrimination of let-7 microRNAs (miRNAs) would greatly facilitate the early diagnosis and prognosis monitoring of diseases. In this work, a molecular beacon DNA probe was designed to be able to flip out its mismatched cytosine base within the α-hemolysin (α-HL) latch and generate completely separated blocking currents to identify the single-base difference. As a result, the characteristic blocking current of fully matched MB/let-7a and single-base mismatched MB/let-7f was 84.30 ± 0.92 and 87.05 ± 0.86% (confidence level P 95%), respectively. Let-7 miRNA family let-7a and let-7f were completely simultaneously discriminated, which could be attributed to the following strengths. (1) The statistic distribution of blocking current is extremely concentrated with a small relative standard deviation (RSD) of less than 1% and a narrow distribution range. (2) Complete separation is achieved with a high separation resolution of 1.54. (3) The cytosine base flipping out within the α-HL latch provides a universal labeling-free strategy to simultaneously discriminate the single-base mismatch. Overall, the target let-7f sequences were detected with a linear range from 0.001 to 10 pM in human serum samples containing 200 nM let-7a. Great potential has been demonstrated for precise detection, early diagnosis, and prognosis monitoring of diseases related to single-base difference.

Nanopore sensing of γ-cyclodextrin induced host-guest interaction to reverse the binding of perfluorooctanoic acid to human serum albumin

Perfluorooctanoic acid (PFOA) has been one of the most common perfluorochemicals, which are globally pervasive contaminants that are persistent, bioaccumulative, toxic, and have adverse impacts on human health. The highest concentration of PFOA occurs in the blood, where it strongly binds to human serum albumins (HSA). Thus, a method to reverse the HSA-PFOA binding is critical to help facilitate the faster elimination of PFOA from the body to minimize its toxicological effects. Inspired by the remediation effect of cyclodextrin (CD) to PFOA through host-guest interactions, herein, by elucidating inter-molecular interactions using a nanopore sensor, we demonstrated in vitro reversal of the binding of PFOA to HSA using γ-cyclodextrin (γ-CD). The competition behavior for the complexation of PFOA between HSA and γ-CD was discussed in combination with in situ nanopore current recording and nuclear magnetic resonance (NMR) characterization. The present work not only demonstrates the potential therapeutic application of γ-CD for PFOA removal from human blood, but also provides an emerging method for investigating interactions between organic compounds and proteins.

Real-Time Label-Free Kinetics Monitoring of Trypsin-Catalyzed Ester Hydrolysis by a Nanopore Sensor

Trypsin is an important proteolytic enzyme in the digestive system and its activity is a major indicator for evaluating diseases such as chronic pancreatitis. Here, we present a novel label-free method to detect trypsin kinetics using a nanopore technique. A mutant α-hemolysin (M113R)₇ protein nanopore equipped with a polyamine decorated β-cyclodextrin (am₇β-CD) was employed as a sensing platform for the real-time monitoring of the process of trypsin enzymatic cleavage of a substrate Nα-benzoyl-l-arginine ethyl ester (BAEE) at the single molecule level. Significantly, this sensor can exclusively respond to the current modulation caused by the product and prevent interference from the substrate, thus improving detection sensitivity, and it provides a new scheme to detect enzyme activity for cleaving small molecules.

Ultra-low noise measurements of nanopore-based single molecular detection

Nanopore is an ultra-sensitive electrochemical technique for single molecular detection in confined space. To suppress the noise in detection of the weak current of nanopore, we investigated the influence of membrane capacitance and applied voltage on the noise of the current signal by model analysis, simulation and experiment. The obtained results demonstrated that membrane capacitance affects the noise by amplifying the noise of the applied voltage. Therefore, suppression of applied voltage noise is an efficient approach for reducing the noise in nanopore detection. Here, we developed an ultra-low noise instrument system for detecting the single molecule signal in nanopores. As demonstrated by nanopore experiments, the p-p noise of the developed system during the recording is reduced to 3.26pA using the filter of 5kHz. Therefore, the developed system could be applied in highly sensitive nanopore detection.