Nestan Shambetova
Licentiate thesis presentation
Time: Mon 2014-09-29 13.00
Location: Seminarierum Air på ScilifeLab, Tomtebodavägen 23, Solna
Subject area: Biologisk fysik
Doctoral student: Nestan Shambetova , Cellens Fysik
Opponent: Professor Jonas Johansson, AstreZeneca R&D, Mölndal
Supervisor: Ying Fu
Titel
Electrical and optical properties of colloidal quantum dots in cultured human airway epithelial cells
Abstract
Colloidal semiconductor quantum dots (QDs) are synthesized from precursor compounds in solution. Photo-generated excitons are confined inside the QDs in all three spatial dimensions. As a result of the spatial confinement, these excitons create superior optical properties for QD-based biomarkers in comparison to traditional organic dyes, resulting in tremendous progress in synthesization, study, and application of these QD-based biomarkers over the past 30 years.
In this thesis, water-dispersible 3-mercaptopropionic acid (3-MPA) coated CdSe-CdS/ZnS core-multishell QDs were used to further explore the novel optical and electrical properties of these QDs in relation to lung health.
The primary function of the human respiratory system is to exchange CO2 for O2 in the alveoli air sacs in the lung, i.e., to transport O2 to, and CO2 from, the bloodstream. In addition to respiration, the lung also functions to metabolize xenobiotic substances and filter possible toxic materials from inhaled air. In this study, we used cultured human airway epithelial cells (Calu-3) as an in vitro model to examine possible interactions between ultra-fine particulate matters simulated by our QDs and the lung epithelium. The integrity and restrictiveness of the epithelial layer under the influence of QDs and the QD permeability through the epithelial layer were studied by monitoring the trans-epithelial electrical resistance and three-dimensional live imaging of the cell layer under confocal microscopy. We found that the tight junctions constrict when the epithelial layer is briefly exposed to QDs.
In order to elucidate the short-term effects of the QDs on the epithelial layer, we studied the electrical properties of QDs in various ion solutions using electrophoresis. We were thus able to quantify the electric charges carried by our 3-MPA coated QDs. It was found that 3-MPA coated QDs moved towards the positive electrode. Their motion towards the positive electrode was reduced when the concentration of Ca2 ions in the QD solution was increased, indicating that the 3-MPA coated QDs are negatively charged and that they interact and combine with positively charged Ca2 .