Single-cell experiments represent the next frontier for biochemical and gene expression research. Although bulk-scale methods averaging populations of cells have been traditionally used to investigate cellular behavior, they mask individual cell features and can lead to misleading or insufficient biological results. We report on a single-cell electroporation microarray enabling the transfection of pre-selected individual cells at different sites within the same culture (space-resolved), at arbitrarily chosen time points and even sequentially to the same cells (time-resolved). Delivery of impermeant molecules by single-cell electroporation was first proven to be finely tunable by acting on the electroporation protocol and then optimized for transfection of nucleic acids into Chinese Hamster Ovary (CHO-K1) cells. We focused on DNA oligonucleotides (ODNs), short interfering RNAs (siRNAs), and DNA plasmid vectors, thus providing a versatile and easy-to-use platform for time-resolved gene expression experiments in single mammalian cells.
We have investigated new aspects of the gate leakage current due to radiation-induced soft breakdown (RSB) of thin oxides subjected to heavy-ion irradiation. Temperature and noise characteristics of RSB on MOS capacitors with 3-and 4-nm MOS oxides have been experimentally investigated. We have developed an empirical law to describe quantitatively the temperature dependence of the RSB current. A small activation energy has been found by using an Arrhenius relation, in agreement with the RSB tunneling conduction mechanism. The RSB variation at high temperature has been only estimated, as measurements of RSB oxides easily produced catastrophic breakdown. We have studied the RSB noise and identified different contributions to the characteristic random telegraph noise, correlated with the trapping and conduction characteristics of the RSB spots. An original model has been developed that successfully describes the different probability distributions of the current fluctuations that cannot be simulated by using previous models, such as those based on Lévy or Gaussian distributions. Finally, a correlation was established between the shape of the fluctuation distribution and the degradation level of the oxide.
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