All-Optical Detection of Neuronal Membrane Depolarization in Live Cells Using Colloidal Quantum Dots.

Luminescent semiconductor quantum dots (QDs) have recently been suggested as novel probes for imaging and sensing cell membrane voltages. However, a key bottleneck for their development is a lack of techniques to assess QD responses to voltages generated in the aqueous electrolytic environments typical of biological systems. Even more generally, there have been relatively few efforts to assess the response of QDs to voltage changes in live cells. Here, we develop a platform for monitoring the photoluminescence (PL) response of QDs under AC and DC voltage changes within aqueous ionic environments. We evaluate both traditional CdSe/CdS and more biologically compatible InP/ZnS QDs at a range of ion concentrations to establish their PL/voltage characteristics on chip. Wide-field, few-particle PL measurements with neuronal cells show the QDs can be used to track local voltage changes with greater sensitivity (ΔPL up to twice as large) than state-of-the-art calcium imaging dyes, making them particularly appealing for tracking subthreshold events. Additional physiological observation studies showed that while CdSe/CdS dots have greater PL responses on membrane depolarization, their lower cytotoxicity makes InP/ZnS far more suitable for voltage sensing in living systems. Our results provide a methodology for the rational development of QD voltage sensors and highlight their potential for imaging changes in cell membrane voltage.

Radiation interaction parameters for blood samples of breast cancer patients: an MCNP study.

The main goal of this study was to determine radiation interaction parameters such as mass attenuation coefficients, effective atomic numbers, and effective electron densities depending on element concentrations (Na, K, Cu, Zn, Al, Ca, Mg Cr, Fe, Se) in blood samples of patients with breast cancer. Eighty blood samples were collected and analyzed in this study (40 from breast cancer patients and 40 from healthy patients). The determination of element concentrations of the samples was performed with inductively coupled plasma-mass spectrometry (ICP-MS) and inductively coupled plasma-optical emission spectrometry (ICP-OES) after which the element concentrations were normalized to percentage. Mass attenuation coefficients were calculated by Monte Carlo simulation method. In addition, effective atomic numbers and effective electron density values of the blood samples were calculated with the ZXCOM program. One of the most important results of this study is that differences in radiation interaction parameters between the two groups were observed. More specifically, the mass attenuation coefficients of the healthy group's blood samples were higher than those of the cancerous group at photon energies of 50 keV, 100 keV, 250 keV and 500 keV, while they were lower at 1 MeV. All the MCNP results were consistent with the results obtained from ZXCOM. As the main result of this study it is concluded that photon atomic parameters such as mass attenuation coefficient, effective atomic number and electron density may be considered in cancer diagnosis or treatment modalities.

The Effect of Dose Enhancement in Tumor With Silver Nanoparticles on Surrounding Healthy Tissues: A Monte Carlo Study.

Objectives: Cancer-related death rates account for approximately one-third of all deaths, and this rate is increasing remarkably every year. In this study, we examined the dose enhancement factor (DEF) in the tumor and surrounding tissues by adding different concentrations of silver nanoparticles (AgNPs) to the brain tumor using the Monte Carlo (MC) technique. Methods: This study used MCNP6.2 simulation software. A Planning Target Volume (PTV) of 1 × 1 × 1 cm3 was placed in the center of a cubic cranial model with dimensions of 5 × 5 × 5 cm3. Five different simulations were initially generated using the simple method. These simulations included pure PTV and PTV consisting of 4 different silver concentrations (5, 10, 20, and 30 mg/g). Additionally, a model was created using the nanolattice method, considering the size, position, and distribution of the AgNPs. Irradiation was performed using a source with a 6 MV linac photon spectrum. Measurements were performed using the *f8 tally, and DEF values were calculated. Results: In the simulation study using the simple method, the DEF value of PTV increased linearly with concentration, whereas the DEF values were lower than the simulation results with the nanolattice model (1.9 vs 1.4 for 30 mg/g NP concentration). Performing the simple method, we observed no remarkable dose increase in lateral OARs surrounding PTV. While a remarkable dose decrease was observed in distal OARs, a dose increase in the proximal OAR was observed, which was consistent with that of PTV. However, according to the results obtained by performing the nanolattice method, the dose increase was observed in both the proximal OAR and the distal OAR and was similar to that of PTV. Conclusion: While enhancing the dose in the tumor by adding NPs into the tumor, it is essential to consider whether it also increases the OAR dose. In addition, simulation studies on NPs showed that the dose increase varied significantly with particle size, position, and distribution. Hence, these factors should be considered carefully.

Tunable Anion-Selective Transport through Monolayer Graphene and Hexagonal Boron Nitride.

Membranes that selectively filter for both anions and cations are central to technological applications from clean energy generation to desalination devices. 2D materials have immense potential as these ion-selective membranes due to their thinness, mechanical strength, and tunable surface chemistry; however, currently, only cation-selective membranes have been reported. Here we demonstrate the controllable cation and anion selectivity of both monolayer graphene and hexagonal boron nitride. In particular, we measure the ionic current through membranes grown by chemical vapor deposition containing well-known defects inherent to scalably produced and wet-transferred 2D materials. We observe a striking change from cation selectivity with monovalent ions to anion selectivity by controlling the concentration of multivalent ions and inducing charge inversion on the 2D membrane. Furthermore, we find good agreement between our experimental data and theoretical predictions from the Goldman-Hodgkin-Katz equation and use this model to extract selectivity ratios. These tunable selective membranes conduct up to 500 anions for each cation and thus show potential for osmotic power generation.

Dosimetric evaluation of right coronary artery in radiotherapy for breast cancer.

Comparison with control groups of untreated patients suggests that right-breast-cancer patients who receive radiotherapy have a higher rate of heart disease. Dose constraint for heart has been established to minimize radiotherapy-induced cardiotoxicity during left breast cancer treatment. Additionally, it is suggested to minimize the dosage on left anterior descending (LAD) artery. Right coronary artery (RCA), is the second largest artery, after left main coronary artery, supplying the heart. A dose evaluation study is not present for RCA; the proximal part of which is included in the irradiation field during breast cancer treatment of right breast. To investigate the presence of a correlation, doses resulting from right and left breast radiotherapy on proximal RCA (pRCA), LAD, and heart are evaluated in this study. Forty breast cancer patients who went under breast-conserving surgery are the subject of this study. Four groups were established; right breast, right breast and internal mammary (IM), left breast and left breast, and IM. pRCA, LAD, and heart volumes were contoured for each group on the planning tomographies. Resultant doses of tangential fields planning on these volumes were compared using dose-volume histograms. Mean and maximum doses of pRCA were statistically compared between groups. The highest mean and maximum point doses (192 to 284 cGy) were found in the right breast + IM group (p < 0.05). The mean and maximum doses only in the right breast and left breast + IM group did not differ statistically. However, the mean and maximum pRCA doses in these 2 groups were higher than only the left breast group (p < 0.05). pRCA receives high doses during radiotherapy of right and left breast especially if IM is included. This may predispose to coronary artery disease.