FRET-based nanosensors

Beyond protein-protein interactions—development and use of FRET-based nanosensors... 

FRET-based nanosensors have been successfully used to monitor steady state levels of metabolites, nutrients, and ions in mammalian cells [74, 87], Recently FRET-based glucose, sucrose, and amino acid nanosensors have been developed to study the metabolism of glucose, sucrose, and amino acid uptake and metabolism in plant cells [80,89, 91]. The enormous potential of these nanosensors will be crucial for understanding ion (e.g., calcium), metabolite (e.g., sugars), hormone (e.g., auxins, gibberellins etc.), and nutrient (e.g., nitrogen, potassium, phosphorus) requirements and homeostasis in living plant tissues. 

Figure 14.4 Function and properties of a QD FRET-based nanosensor. Generalized QD bioconjugate nanosensor schematic. Each QD is surrounded by an average of —10—15 protein molecules. Formation of QD-protein-analogue assembly results in quenching of the QD emission. Adding preferred analyte to the solution displaces dye-labeled analogue from the sensor assembly, resulting in an increase in direct QD emission.

In the last years, the number of publications related to QD-FRET-based systems has increased continuously. In 2008, a FRET-based nanosensor was developed for the rapid detection of human cardiac troponin I, which is a key factor for the early detection of myocardial infarction.96 In this system, a donor(QD)-labeled protein A is bound to an acceptor-labeled capture antibody and the presence of troponin I antigen generates a conformational change within the structure of the antibody. This results in a change of the distance between the donor and acceptor and, therefore, a shift in energy transfer is observed. A limit of detection of 55 nM of troponin in human plasma and a very short time of analysis (1 minute) were reported using this biosensor. 

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