Study Of Indium Phosphide Quantum Dots In Cell Imaging And Bioeffects

The unique optical properties of quantum dots(QDs)make them widely used as biological probes in biomedical imaging in vitro and in vivo.The initial development of QDs is dominated by cadmium-containing QDs,such as CdTe and CdSe.Since the material properties of cadmium-containing QDs determine the risk of cadmium exposure that may cause toxicity,many cadmium-free QDs have been developed in recent years.Indium Phosphide(InP)QDs are the most widely used non-cadmium QDs and have more stable covalent bonds and better biocompatibility than conventional cadmium-containing QDs.They are considered to have greater potential for biomedical applications.The surface functionalization of QDs is one of the important factors affecting their application performance and biological effects.In order to explore the feasibility of biological applications of InP QDs,we have chosen InP QDs modified with carboxyl,amino,and hydroxyl groups,respectively.Both imaging applications and biological effects have been systematically studied.1.InP QDs for Cell LabelingLung cancer cells HCC-15 and alveolar type ? epithelial cells RLE-6TN were co-incubated with InP QDs for 4 hours.Confocal imaging and flow cytometry were used to detect the uptake of QDs by cells.Confocal imaging showed that InP QDs modified with carboxyl,amino,and hydroxyl groups,respectively,could be taken up by HCC-15 and RLE-6TN cells and accumulated in the cytoplasm.Flow cytometry showed that the uptake of QDs by cells is concentration dependent.At low concentrations,there was a significant difference in uptake of the three modified QDs by the cells;at high concentrations,the cell uptake rates for the three QDs were comparable,all higher than 90%.2.InP QDs as traceable nanocarriers for gene deliveryPolyethylenimine(PEI)-modified InP QDs can be used as traceable nanocarriers for gene delivery.InP QDs were modified with PEI and coupled with small interfering RNA(siRNA)to form nanocomplexes.The siRNA transfection effect was detected by confocal imaging and flow cytometry.Confocal imaging showed that InP QDs could successfully deliver siRNA into HCC-15 cells and image in real time.Flow cytometry showed that the transfection rate of siRNA on cells reached 31%,which indicate InP QDs can be used as an effective nanocarriers for siRNA.3.In vitro biological effects of InP QDsHCC-15 and RLE-6TN cells were co-incubated with InP QDs for 24 or 48 hours.The cytotoxicity of QDs was detected by MTT assay and apoptosis assay,and the ROS assay was adopted to explore the damage mechanism of QDs.MTT results demonstrated that InP QDs terminated with carboxyl,hydroxyl or amino groups have no considerable cytotoxicity within 24 hours,but exhibit significant cytotoxicity when treated for 48 hours at higher than 20 ?g/mL.Apoptosis were induced by InP QDs when cells were incubated for 48 hours.ROS experiments show that oxidative stress injury induced by the QDs is one of the causes of cytotoxicity.4.In vivo biological effects of InP QDsAfter intratracheally inhaled with 25 mg/kg InP QDs,BALB/c mice were sacrificed and their blood and organs were collected at different time points.Fluorescence imaging of tissue sections and ICP-MS analysis were used to explore the in vivo biodistribution of InP QDs.The damage effects of the QDs on the organ were detected by H&E staining.The fluorescence imaging of mice tissues indicate that InP QDs can accumulate in the lungs and remain fluorescence ability at 24 h after inhalation.ICP-MS results showed that the QDs can cross through the blood-air barrier and distributed in the major organs of mice.However,the accumulation of QDs in the lungs did not cause morphological changes by H&E staining experiments.In summary,InP QDs can be used as fluorescent probes for cell labeling and traceable nanocarriers for live cell imaging.When the treatment concentration of QDs is higher than 20 ?g/mL,the cell viability is inhibited and cell apoptosis is promoted as a result of oxidative stress injury induced by the QDs.Endotracheal inhalation of InP QDs at the dose of 25 mg/kg did not cause significant damage to the mice organs.The research results provide safety evidence for advancing the application of InP QDs in the biomedical field.