Abstract
Quantum dot (Qdot) biosensors have consistently provided valuable information to researchers about cellular activity due to their unique fluorescent properties. Many of the most popularly used Qdots contain cadmium, posing the risk of toxicity that could negate their attractive optical properties. The design of a non-cytotoxic probe usually involves multiple components and a complex synthesis process. In this paper, the design and synthesis of a non-cytotoxic Qdot-chitosan nanogel composite using straight-forward cyanogen bromide (CNBr) coupling is reported. The probe was characterized by spectroscopy (UV-Vis, fluorescence), microscopy (Fluorescence, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Dynamic Light Scattering. This activatable (“OFF”/“ON”) probe contains a core–shell Qdot (CdS:Mn/ZnS) capped with dopamine, which acts as a fluorescence quencher and a model drug. Dopamine capped “OFF” Qdots can undergo ligand exchange with intercellular glutathione, which turns the Qdots “ON” to restore fluorescence. These Qdots were then coated with chitosan (natural biocompatible polymer) functionalized with folic acid (targeting motif) and Fluorescein Isothiocyanate (FITC; fluorescent dye). To demonstrate cancer cell targetability, the interaction of the probe with cells that express different folate receptor levels was analyzed, and the cytotoxicity of the probe was evaluated on these cells and was shown to be nontoxic even at concentrations as high as 100 mg/L.
Highlights
Quantum dots (Qdots) are small crystals made of semiconductor material that possess unique size dependent optical properties due to confinement of their electronic states [1,2,3,4]
As shown in Scheme 1, the basic principle behind the activatability of the quantum dots is the quenching of the Qdot due to electron transfer from dopamine bound to the Qdot [19]
An absorption peak was observed at 278 nm that was assigned to dopamine [43]. This peak was found in both spectra of the dopamine–Qdot conjugate and the full probe. These spectra show that dopamine remains on the Qdot surface after rigorous washing
Summary
Quantum dots (Qdots) are small crystals made of semiconductor material that possess unique size dependent optical properties due to confinement of their electronic states [1,2,3,4]. Our previous work has shown that the fluorescence of the dopamine-Qdot conjugate can be restored upon reduction of the disulfide bond by glutathione (GSH) [19] These activatable Qdots are photo-stable in solution but have limited applications for bioimaging and drug delivery unless functionalized further. Qdot–chitosan composite gel probe (full probe) to be used for cell tracking and drug delivery This proof-of-concept study employs Mn2+ doped CdS/ZnS core shell Qdots capped with dopamine. The dopamine acts as a model drug, simulating intercellular drug delivery These Qdots are crosslinked to hydrothermally treated chitosan to create a piggyback style, nontoxic, multifunctional probe in a one-step process by using CNBr chemistry. The multimodal functionality and piggyback structure of this probe will allow it to be used in the future by researchers for targeted drug delivery and cell tracking
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
