Non-Cytotoxic Quantum Dot–Chitosan Nanogel Biosensing Probe for Potential Cancer Targeting Agent

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 OPEN ACCESS Nanomaterials 2015, 5 2360 ("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.

Multifunctional Polymeric Nanogels for Biomedical Applications

“…The interaction between this QD nanogel and cells that expressed different levels of folic acid was demonstrated along with being nontoxic up to 100 mg/L. [ 56 ]…”

Strategies on Nanodiagnostics and Nanotherapies of the Three Common Cancers

“…Besides this, Yao et al fabricated magnetofluorescent carbon quantum dots (MFCQDs) using a combination of waste crab shell and transition-metal ions Gd 3+ , Mn 2+ , and Eu 3+ as potential diagnostic probes, from which the chitin acted not only as a carbon source but also as a chelating ligand to form complexes with transition-metal ions [ 31 ]. For safety and environmental protection, it is essential to reduce toxic heavy metal use for quantum dots [ 32 ]. When a small part of the quantum dots does not accumulate at the tumor site, the membrane-impermeable etchant can rapidly quench the quantum dots and acquire highly tumor-specific signals through cation exchange in vivo [ 33 ].…”

ZnS Quantum Dots/Gelatin Nanocomposites with a Thermo-Responsive Sol–Gel Transition Property Produced by a Facile and Green One-Pot Method

“…Quantum dots (QDs) have a range of applications in solar cells, light-emitting diodes, biological imaging, and sensors due to their special size-dependent optical, electronic, magnetic, and chemical properties. − The major limitation for the well-established QDs is that they usually contain toxic elements such as cadmium (Cd), plumbum (Pb), and mercury (Hg). − Therefore, the QDs without toxic elements such as ZnS QDs and Mn-doped ZnS QDs have drawn considerable research interest lately. − …”