Investigation on the direct and bystander effects in HeLa cells exposed to very low α-radiation using electrical impedance measurement

The impact of radiation-induced bystander effect (RIBE) is still not well understood in radiotherapy. RIBEs are biological effects expressed by nonirradiated cells near or far from the irradiated cells. Most radiological studies on cancer cells have been based on biochemical characterization. However, biophysical investigation with label-free techniques to analyze and compare the direct irradiation effect and RIBE has lagged. In this work, we employed an electrical cell-indium tin oxide (ITO) substrate impedance system (ECIIS) as a bioimpedance sensor to evaluate the HeLa cells’ response. The bioimpedance of untreated/nonirradiated HeLa (N-HeLa) cells, α-particle (Am-241)-irradiated HeLa (I-HeLa) cells, and bystander HeLa (B-HeLa) cells exposed to media from I-HeLa cells was monitored with a sampling interval of 8 s over a period of 24 h. Also, we imaged the cells at times where impedance changes were observed. Different radiation doses (0.5 cGy, 1.2 cGy, and 1.7 cGy) were used to investigate I-HeLa and B-HeLa cells’ radiation-dose-dependence. By analyzing the changes in absolute impedance and cell size/number with time, compared to N-HeLa cells, B-HeLa cells mimicked the I-HeLa cells’ damage and modification of proliferation rate. Contrary to the irradiated cells, the bystander cells’ damage rate and proliferation rate enhancements have an inverse radiation-dose-response. Also, we report multiple RIBEs in HeLa cells in a single measurement and provide crucial insights into the RIBE mechanism without any labeling procedure. Unambiguously, our results have shown that the time-dependent control of RIBE is important during α-radiation-based radiotherapy of HeLa cells

Microdissected "cuboids" for microfluidic drug testing of intact tissues

As preclinical animal tests often do not accurately predict drug effects later observed in humans, most drugs under development fail to reach the market. Thus there is a critical need for functional drug testing platforms that use human, intact tissues to complement animal studies. To enable future multiplexed delivery of many drugs to one small biopsy, we have developed a multi-well microfluidic platform that selectively treats cuboidal-shaped microdissected tissues or “cuboids” with well-preserved tissue microenvironments. We create large numbers of uniformly-sized cuboids by semi-automated sectioning of tissue with a commercially available tissue chopper. Here we demonstrate the microdissection method on normal mouse liver, which we characterize with quantitative 3D imaging, and on human glioma xenograft tumors, which we evaluate after time in culture for viability and preservation of the microenvironment. The benefits of size uniformity include lower heterogeneity in future biological assays as well as facilitation of their physical manipulation by automation. Our prototype platform consists of a microfluidic circuit whose hydrodynamic traps immobilize the live cuboids in arrays at the bottom of a multi-well plate. Fluid dynamics simulations enabled the rapid evaluation of design alternatives and operational parameters. We demonstrate the proof-of-concept application of model soluble compounds such as dyes (CellTracker, Hoechst) and the cancer drug cisplatin. Upscaling of the microfluidic platform and microdissection method to larger arrays and numbers of cuboids could lead to direct testing of human tissues at high throughput, and thus could have a significant impact on drug discovery and personalized medicine.The National Cancer Institute; Juno Therapeutics; CoMotion at the University of Washington; a Hong Kong Research Grant Council; an International Scholars award from the Consejo Nacional de Ciencia y Tecnología of Mexico; a Department of Defense Prostate Cancer Research Program and the National Science Foundation Graduate Research Fellowship Program.http://pubs.rsc.org/en/Journals/JournalIssues/LChj2022Mechanical and Aeronautical Engineerin

A 1.8–2.3 GHz broadband Doherty power amplifier with a minimized impedance transformation ratio

The 2015 Asia-Pacific Microwave Conference (APMC), Nanjing, China, 6-9 December 2015In this paper, the design and measurement results of a 1.8 GHz to 2.3 GHz broadband Doherty power amplifier (DPA) are reported. A modified load modulation network is designed to minimize impedance transformation ratio over the entire dynamic range for the purpose of extending the operating bandwidth. Experimental results show that the drain efficiency of the proposed DPA maintains above 50% and 63% with continuous wave input signal powers of 26 dBm and 34 dBm, respectively, from 1.8 GHz to 2.3 GHz. When stimulated by a 60-MHz, 12- carrier UMTS signal at 2.14 GHz, the proposed DPA achieved an average efficiency of 53% at 7.6 dB back-off, while the corresponding adjacent channel leakage ratio is linearized to -48.4 dBc with digital predistortion.Science Foundation IrelandChina Scholarship Counci

Improved Doherty Amplifier Design with Minimum Phase Delay in Output Matching Network for Wideband Application

This letter presents an improved Doherty power amplifier (DPA) for high-efficiency and wideband operations. To achieve the impedance transformations both in the low power region and at saturation, a design approach is proposed to determine the desired minimum phase delays of the carrier and peaking output matching networks, which can simplify the load modulation network of the DPA and extend the bandwidth. For verification, a 1.6-2.2 GHz asymmetric DPA was designed and measured. The designed DPA can deliver an efficiency of 51%-55% at 10 dB back-off power over the whole band. For a 20 MHz LTE signal, an average efficiency of higher than 50% can be achieved at 36 dBm average output power with the linearity of -48 dBc after linearization across the band.Science Foundation IrelandNatural Science Foundation of Jiangsu Province of Chin

X-ray measurement of intracellular chloride and other ions in mammalian cells

Intracellular chloride ion (Cl−) is known to have various roles in the cellular growth, modulation of cell cycles and volume, and in pathological disorders such as cancers, neurological and cardiovascular disorders. Various methods employed to measure intracellular Cl− requires lengthy procedure and measurement duration, bulky and advanced instruments, or incapable to measure low to single-cell sample quantity. In this study, we report the measurement of intracellular chloride and other ions in mammalian cells using the FROZEN freeze-drying method for preparing adherent cell cultures for analysis. The sample preparation does not require chemical fixation and enables direct measurement by X-Ray analytical methods such as X-Ray Fluorescence (XRF) or Energy Dispersive X-Ray Fluorescence (EDS). Cell staining showed that the cells retained their content and location after preparation, which enables single-cell level analysis. Treatment of Furosemide to the cells disrupted the Cl−, K+ and Na+ transport, causing changes in the intracellular ions. Additionally, the intracellular Cl− of the dried cells was successfully measured, as low as 0.9 mM. The XRF and EDS measurements showed that treated cells displayed a significant reduction of intracellular Cl− on all tested cell lines. However, no significant changes were detected in intracellular K+. Furthermore, EDS analysis on single cells showed a significant decrease in intracellular Na+ in most cell lines. These results demonstrate the efficiency and simplicity of the proposed method in intracellular ion analysis, allowing quick and simple preparation to measure biological samples with high sensitivity for various intracellular ions, which may be applicable in the diagnosis of diseases