Near-Infrared Imaging of Serotonin Release from Cells with Fluorescent Nanosensors

Abstract

Serotonin is an important neurotransmitter involved in various functions of the nervous, blood, and immune system. In general, detection of small biomolecules such as serotonin in real time with high spatial and temporal resolution remains challenging with conventional sensors and methods. In this work, we designed a near-infrared (nIR) fluorescent nanosensor (NIRSer) based on fluorescent singlewalled carbon nanotubes (SWCNTs) to image the release of serotonin from human blood platelets in real time. The nanosensor consists of a nonbleaching SWCNT backbone, which is fluorescent in the beneficial nIR tissue transparency window (800−1700 nm) and a serotonin binding DNA aptamer. The fluorescence of the NIRSer sensor (995 nm emission wavelength for (6,5)-SWCNTs) increases in response to serotonin by a factor up to 1.8. It detects serotonin reversibly with a dissociation constant of 301 nM ± 138 nM and a dynamic linear range in the physiologically relevant region from 100 nM to 1 μM. As a proof of principle, we detected serotonin release patterns from activated platelets on the single-cell level. Imaging of the nanosensors around and under the platelets enabled us to locate hot spots of serotonin release and quantify the time delay (≈ 21−30 s) between stimulation and release in a population of platelets, highlighting the spatiotemporal resolution of this nanosensor approach. In summary, we report a nIR fluorescent nanosensor for the neurotransmitter serotonin and show its potential for imaging of chemical communication between cells.

Fluorescent Single-Walled Carbon Nanotubes for Protein Detection

“…This review provides an overview and a comprehensive survey of the utilization of SWCNTs for biosensing applications. The non-photobleaching, non-blinking fluorescent emission of SWCNTs plays a key role in rendering them optical sensors, enabling in situ, label-free, real-time detection with both spatial and temporal resolution [89,113,115]. Recent studies have demonstrated the detection of proteins using various approaches for surface functionalization, including natural substrates [53,121,125] and synthetic polymers [89,129,145], with the potential to enable long-term continuous monitoring of important biomarkers or to replace costly and time-consuming laboratory testing [173].…”

“…A recent study has demonstrated the recognition of the neurotransmitter serotonin using SWCNTs wrapped with a serotonin-aptamer. This nanosensor was immobilized on a glass surface, on which human blood platelets were cultured, and were shown to detect serotonin release patterns from the cells in real time [115]. Additionally, DNA-wrapped SWCNTs were utilized for the detection of a single-stranded RNA genome of an intact HIV particle [116] and of doxorubicin, a chemotherapy drug effective against dividing cells due to its affinity to DNA [117].…”

Transport and programmed release of nanoscale cargo from cells by using NETosis

“…11,12,[15][16][17][18]62 For example, recently, a SWCNT-based sensor for another important neurotransmitter (serotonin) has been introduced. 13 Another application is to use SWCNTs as mechanical sensors. In this context, SWCNTs have been used to study movements in cells and the extracellular space in brain tissue.…”

“…[7][8][9][10] Their surface can be chemically tailored with DNA, peptides, lipids, nanobodies or viruses to sense biologically relevant signaling molecules with high spatiotemporal resolution. [11][12][13][14][15][16][17][18] Thus, such nanomaterials are attractive candidates for biomedical applications. It is also known that nanomaterials such as SWCNTs can be taken up by living cells depending on their size.…”

Rationally Design of Near Infrared Light Responsive Micro‐Photoelectrodes for In Vivo Sensing of Neurotransmitter Molecules in Mouse Brain†

“…More intractably, the UV/Vis light presents poor penetration depth in biological tissues, that is, the PEC sensors worked under UV/Vis light illumination will not work anymore for in vivo detection in the living body due to the lacking of effective light illumination. Inspired from the photothermal therapy strategy for in vivo cancer treatment under near‐infrared (NIR) light irradiation, and NIR fluorescent biosensor for detection of neurotransmitters, we hypothesize that the NIR responsive PEC sensors will be a highly promising option for implementation of un‐biased PEC in vivo detection as the NIR light owns much deeper tissue penetration and better biocompatibility than the UV/Vis light. However, very surprisingly, after carefully searching the reported literatures, the NIR responsive PEC sensors have been rarely reported, and no any practical in vivo PEC detection has been conducted.…”