In this study, we synthesized a multifunctional nanoparticulate system with specific

In this study, we synthesized a multifunctional nanoparticulate system with specific targeting, imaging, and drug delivering functionalities by following a three-step protocol that operates at room temperature and solely in aqueous media. using Fourier transform infrared, X-ray diffraction, dynamic light scattering, ultraviolet-visible, and fluorescence spectroscopy. Further characterization was conducted using thermogravimetric analysis, high-resolution transmission electron microscopy, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray fluorescence, and X-ray photoelectron spectroscopy. The cell viability and proliferation studies by means of MTT assay have demonstrated that the as-synthesized composites do not exhibit any toxicity toward the human breast cell line MCF-10 (noncancer) and the breast cancer cell lines (MCF-7 and MDA-MB-231) up to a 500 g/mL concentration. The cellular uptake of the nanocomposites was assayed by confocal laser scanning microscope by taking advantage of 202189-78-4 IC50 the conjugated Mn:ZnS QDs as fluorescence makers. The result showed that the functionalization of the chitosan-encapsulated QDs with folic acid enhanced the internalization and binding affinity of the nanocarrier toward folate receptor-overexpressed cells. Therefore, we hypothesized that due to the nontoxic nature of the composite, the as-synthesized nanoparticulate system can be used as a promising candidate for 202189-78-4 IC50 theranostic applications, especially for a simultaneous targeted drug delivery and cellular imaging. is the absorption coefficient, is the photon energy, is the direct band gap energy, and is a constant. Figure 5 (A) Comparison of the UV-Vis spectra of FA with that of bare Mn:ZnS and FACS-Mn:ZnS GRF55 QDs; (B) Tauc 202189-78-4 IC50 plot obtained from the UV-Vis study with a band gap energy of 5.08 eV for FACS-Mn:ZnS QDs. The Mn:ZnS QDs characteristic fluorescence behavior and its mechanism at various stages is fully demonstrated in Figure 6ACC. The Figure 6A shows the comparison of fluorescence spectra of bare ZnS QDs (without Mn doping) and FACS-Mn:ZnS (with Mn doping). The fluorescence comparison of the two samples provides the information that the doping of ZnS QDs with suitable impurity such as Mn2+ and independent of particle size can significantly enhance its luminescence properties. As seen from the spectra, the doping of ZnS with Mn2+ induces a red shift from the blue region at 450 nm, typical of undoped ZnS to more biofriendly visible region. The characteristic ZnS spectral shifted from the blue region toward the red region on doping with Mn2+ impurities and resulted in the emission of orange fluorescence at 600 nm. Similarly, Figure 6B shows what actually transpired following the doping chemistry, a change in color to orange when viewed under handheld UV lamp. From the Jaboliski diagram shown in Figure 6C, several mechanisms interplay to produce fluorescence emission in QDs following the excitation of ground state electron to the excitonic state. The excited electrons either radiatively or nonradiatively relax and in the process, they recombine with the holes in the ground state with the emission of fluorescence light. In the case of ZnS as diagrammatically represented, the electron in the conduction band (CB) of ZnS lattice radiatively relaxes to the hole in the valence band (VB) passing through interstitial pathways of sulfur (Is) and Zn (Iz). The emission at 470 nm is due to the relaxation that occurs when the excited state electrons are trapped by sulfur vacancy donor levels.49,50 The Mn2+ ion has a d5 configuration, where the d-electron state plays a central role as the luminescence center by interacting strongly with the sCp electronic state of the host ZnS in response to the electronic excitation.10 The resultant transfer of electrons and holes charges into the electronic level of Mn2+ ions allow the emission of characteristic orangeCred fluorescence following 4T1C6A1 transition of the Mn2+ ion.10 To further buttress the phenomenon surrounding the effect of doping of atoms to ZnS, several pathways are reported to take part during the excitation of Mn2+ in the host ZnS and the subsequent orange emission (OE). As can be seen in Figure 6C, three main possible pathways maybe responsible for the electronChole recombination that further leads to OE:50 In the first relaxation pathway, there exists the possibility that the electron in the CB of the ZnS lattice radiatively relaxes to the holes in the VB through Is and Iz (ie, interstitial sites of sulfur and zinc). Due to lattice strain induced by Is and the large ionic radius of sulfur ion as compared with Zn ions, the electrons initiated by Is has small binding energy relative to Zn ion.49 In 202189-78-4 IC50 the second relaxation pathway, it is possible that the blue emission can be observed at 475 nm from the relaxation that occurs when the electrons in the excited state are trapped by the sulfur vacancy donor levels. It is further considered that:.