Abstract
In the last few years, quantum dot (QD) nanoparticles have been employed for bioimaging and sensing due to their excellent optical features. Most studies have used photoluminescence (PL) intensity-based techniques, which have some drawbacks, especially when working with nanoparticles in intracellular media, such as fluctuations in the excitation power, fluorophore concentration dependence, or interference from cell autofluorescence. Some of those limitations can be overcome with the use of time-resolved spectroscopy and fluorescence lifetime imaging microscopy (FLIM) techniques. In this work, CdSe/ZnS QDs with long decay times were modified with aminophenylboronic acid (APBA) to achieve QD-APBA conjugates, which can act as glucose nanosensors. The attachment of the boronic acid moiety on the surface of the nanoparticle quenched the PL average lifetime of the QDs. When glucose bonded to the boronic acid, the PL was recovered and its lifetime was enhanced. The nanosensors were satisfactorily applied to the detection of glucose into MDA-MB-231 cells with FLIM. The long PL lifetimes of the QD nanoparticles made them easily discernible from cell autofluorescence, thereby improving selectivity in their sensing applications. Since the intracellular levels of glucose are related to the metabolic status of cancer cells, the proposed nanosensors could potentially be used in cancer diagnosis.
Highlights
Glucose is the major energy source for the maintenance of cell homeostasis and cell proliferation.Cancer cells primarily rely on glucose and glutamine to supply intermediary metabolism, so the glucose metabolism level reflects the cell’s proliferative status [1]
Since boronic acid has been widely employed in glucose sensors, it was expected that the quantum dot (QD) modified with aminophenylboronic acid (APBA) groups on their surface (QD-APBA conjugates) would act as photoluminescent glucose nanosensors
We have demonstrated that the use of QD-based photoluminescent nanosensors a good alternative to conventional electrochemical glucose probes based on glucose oxidase or other is a good alternative to conventional electrochemical glucose probes based on glucose oxidase or enzymes, which have limited accuracy and reduced responses in vivo, possibly because they suffer other enzymes, which have limited accuracy and reduced responses in vivo, possibly because they from some interference caused by the presence of electroactive substances in the tissues, among others
Summary
Glucose is the major energy source for the maintenance of cell homeostasis and cell proliferation.Cancer cells primarily rely on glucose and glutamine to supply intermediary metabolism, so the glucose metabolism level reflects the cell’s proliferative status [1]. Anomalous glucose levels in the blood or physiological fluids are directly related to some diseases, such as diabetes [2], so the development of new and improved glucose sensors is of high interest for biomedical diagnosis and for applications in healthcare products [3]. Many different glucose sensors have been developed to monitor the changes in glucose concentrations. Enzymatic-based glucose probes have prevailed for decades, being glucose oxidase (GOx) the most commonly used enzyme. The sensing mechanism is based on the oxidation of glucose by molecular oxygen catalyzed by GOx, which generates H2 O2. The first systems were very basic electrochemical sensors [4,5,6] that essentially used amperometric detection, more recently, the combination of GOx with new nanomaterials, such as semiconductor nanoparticles [7,8], carbon nanotubes [9], or graphene [10], has produced more sophisticated and highly sensitive glucose sensors
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