## 3 Results and Discussion  
### Real-Time Cell Analysis of Proliferation of LoVo Cells Treated with Ru(III) Complexes  
The xCELigence System of Real-Time Cell Analyzer (RTCA) allows label-free and real-time monitoring of cellular processes such as cell proliferation, cytotoxicity, adhesion, viability, invasion, and migration, using electronic cell sensor array technology. Cellularevents are monitored in real time without the incorporation of labels by measuring the electrical impedance across inter-digitated micro-electrodes integrated on the bottom of special tissue culture plates. The actual kinetic response of the cells within an assay provided important information regarding the biological status of the cell. Changes in cell status, such as cell morphology, adhesion, or viability led to a change in cell index (CI), which is a quantitative measure of the cell number present in a well [58]. The capacity of cisplatin (CisPt), a metallic anticancer drug that has been used for many years to treat various human cancers, including colon cancer, and Ru(III) complexes to inhibit cell proliferation was investigated in a LoVo colon cancer cell line in order to modulate the chemosensitivity of colon cancer cells to drug treatments and overcome the chemoresistance. Therefore, we monitored compound-induced cytotoxicity to produce continuous compound- and concentration-dependent cell impedance profiles using the xCELLigence System and LoVo cancer cell line as our in vitro model. To assess the optimal number of cells to be used in further assays, in a first line of experiments, LoVo colon cancer cells were seeded at scalar densities from 10\({}^{3}\) to 10\({}^{6}\)/well in 16-well E-Plates for a dynamic monitoring of adherent cell proliferation. The cell growth curves were automatically recorded on the xCELLigence System in real time. RTCA growth curves of LoVo cells and CI values prompted us to establish the optimal cell density to be used in further experiments and choose the 15 \(\times\) 10\({}^{3}\) cells/well for the Ry(III) compound-mediated cell cytotoxicity assays (data not shown). LoVo cancer cells were seeded in E-plates 16 in complete culture medium (1.5 \(\times\) 10\({}^{4}\) cells/well/100 \(\upmu\)L), plates were put in the xCELLigence DP device and cultured at 37 \({}^{\circ}\)C in a 5% CO\({}_{2}\) humidified atmosphere. After 24 h, cells were added by increasing concentrations of Ru(III) complexes or CisPt (from 12.5 to 200 \(\upmu\)M), and growth curves were registered in real time on a computer by using RTCA 2.1.2. Software. Then, the cell growth, proliferation, and viability of LoVo cells were continuously monitored. Results are expressed as normalized cell index (CI) after automatic comparison between the curves of viability for treated vs. non-treated (NT) cells (Figure 2). Some active ruthenium complexes could manifest cytotoxic action against various cancer cell lines, including colon cancer cell lines [16; 17; 20]. Therefore, we investigated the proliferative vs. cytotoxic action of Ru(III) complexes on the LoVo colon cancer cell line, and results varied depending on the type of compound, concentration, and treatment time. RTCA analysis of the LoVo cell line proliferation curves for cells treated with concentrations between 6.25 and 200 \(\upmu\)M of Ru(III) complexes, and normalized vs. control (the proliferation curve for untreated cells), demonstrated a pronounced cytotoxicity decrease in viability for almost all the concentrations used in the assay, mostly for 25, 50, 100, or 200 \(\upmu\)M (Figure 2). Among the tested Ru(III) complexes, Ru-nf, Ru-oflo, and Ru-levo seem to induce the highest inhibition of LoVo cell proliferation during the first 24 h of treatments with 50, 100, or 200 \(\upmu\)M of drugs. Ru-pip, Ru-enro, and Ru-enoxa showed also inhibitory effects on cell proliferation, the inhibitory effect becoming stronger with increasing treatment time.