Silvia Canepa

Impedimetric Toxicity Assay in Microfluidics Using Free and Liposome-Encapsulated Anticancer Drugs

In this work, we have developed a microfluidic cytotoxicity assay for a cell culture and detection platform, which enables both fluid handling and electrochemical/optical detection. The cytotoxic effect of anticancer drugs doxorubicin (DOX), oxaliplatin (OX) as well as OX-loaded liposomes, developed for targeted drug delivery, was evaluated using real-time impedance monitoring. The time-dependent effect of DOX on HeLa cells was monitored and found to have a delayed onset of cytotoxicity in microfluidics compared with static culture conditions based on data obtained in our previous study. The result of a fluorescent microscopic annexin V/propidium iodide assay, performed in microfluidics, confirmed the outcome of the real-time impedance assay. In addition, the response of HeLa cells to OX-induced cytotoxicity proved to be slower than toxicity induced by DOX. A difference in the time-dependent cytotoxic response of fibrosarcoma cells (HT1080) to free OX and OX-loaded liposomes was observed and attributed to incomplete degradation of the liposomes, which results in lower drug availability. The matrix metalloproteinase (MMP)-dependent release of OX from OX-loaded liposomes was also confirmed using laryngopharynx carcinoma cells (FaDu). The comparison and the observed differences between the cytotoxic effects under microfluidic and static conditions highlight the importance of comparative studies as basis for implementation of microfluidic cytotoxic assays.

Phosphate tuned copper electrodeposition and promoted formic acid selectivity for carbon dioxide reduction

Fabrication of catalytically active electrodes by electrodeposition is attractive due to its in situ nature, easy controllability, and large-scale operation capability. Most recently, modifying the electrodes with phosphate ligands through electrodepositing electrode materials has shown promising results in improving the kinetics of some reactions. However, it is unclear how the presence of phosphate anions affects the electrodeposition process and functions in catalyzing reactions. Here, we report a systematic study on electrodeposition of Cu in the presence of phosphate anions. The phosphate anions form a complex with free Cu(II) cations, competing with the electrodeposition process. The competition between the two processes results in an insufficient supply of free Cu(II) for electrodeposition, especially at the diffusion layer. This is evidenced by the calculation of free Cu(II) concentration and the electrodeposition current at identical applied potentials. We also found that the electrodeposition of Cu in the presence of phosphate generates Cu-oxyo/hydroxyo-phosphate species on the deposited copper surface. The modified electrodes with phosphate species exhibit higher selectivity for HCOOH formation (faradaic efficiency ∼80%) from the electrochemical reduction of CO2 as compared with Cu foil (faradaic efficiency ∼33%). The effect of phosphate ligands promoting HCOOH selectivity is further verified by stripping off the ligands and regenerating the ligands.

Using Microfluidic Chips with Nanochannels for Measuring the Mean Inner Potential of Liquid Water by Off-Axis Electron Holography

Electrons interact with the electric and magnetic fields existing within and around a TEM specimen which leads to changes in the transmitted electron wave function. Electron holography [1] can be used to measure the phase and amplitude changes of the electron wave. Offaxis electron holography[2] requires a coherent and bright beam split into two parts: one passes through sample as object wave; one pass through vacuum as reference wave. A charged biprism wire tilts the reference wave relative to the object wave, so that the two waves interfere and a hologram TEM image can be recorded.

In Situ TEM Electrical Measurements

Transmission electron microscopy (TEM) offers high spatial and temporal resolution that provides unique information for understanding the function and properties of nanostructures on their characteristic length scales. Under controlled environmental conditions and with the ability to dynamically influence the sample by external stimuli, e.g. through electrical connections, the TEM becomes a powerful laboratory for performing quantitative real time in situ experiments. Such TEM setups enable the characterization of nanostructures and nanodevices under working conditions, thereby providing a deeper understanding of complex physical and chemical interactions in the pursuit to optimize nanostructure function and device performance. Recent developments of sample holder technology for TEM have enabled a new field of research in the study of functional nanomaterials and devices via electrical stimulation and measurement of the specimen. Recognizing the benefits of electrical measurements for in situ TEM, many research groups have focused their effort in this field and some of these methods have transferred to ETEM. This chapter will describe recent advances in the in situ TEM investigation of nanostructured materials and devices with the specimen being contacted by electrical, mechanical or other means, with emphasis on in situ electrical measurements performed in a gaseous or liquid environment. We will describe the challenges and prospects of electrical characterization of devices and processes induced by a voltage in gas and liquids. We will also provide a historical perspective of in situ TEM electrical measurements and applications using electrical contacts.