Previous studies have reported a lateral migration in particle electrophoresis through a straight rectangular microchannel. This phenomenon arises from the inherent wall-induced electrical lift that can be exploited to focus and separate particles for microfluidic applications. Such a dielectrophoretic-like force has been recently found to vary with the buffer concentration. We demonstrate in this work that the particle zeta potential also has a significant effect on the wall-induced electrical lift. We perform an experimental study of the lateral migration of equal-sized polystyrene particles with varying surface charges under identical electrokinetic flow conditions. Surprisingly, an enhanced focusing is observed for particles with a faster electrokinetic motion, which indicates a substantially larger electrical lift for particles with a smaller zeta potential. We speculate this phenomenon may be correlated with the particle surface conduction that is a strong function of particle and fluid properties.
Programmed cell death (PCD), an active process that leads to cell suicide, is a critical mechanism in every organism. MazF, a bacterial ribonuclease protein, can trigger PCD in bacterial cells and also induce Bak-dependent apoptosis in mammalian cells. This bacterial ribonuclease cleaves mRNAs at ACA sequences leading to inhibition of protein synthesis in cells. Hence, we hypothesized that the overexpression of MazF proteins in cancer cells could result in the induction of apoptosis. In the present study, the ACA-less mazF gene was inserted downstream of the Internal Ribosome Entry Site (IRES) and under the control of T7 promoter. The plasmid was electroporated into Listeria monocytogenes harboring pCSA1 that encodes T7 RNA polymerase under the control of the listeria actA promoter. Subsequently, the bacteria were functionalized with Trastuzumab (Herceptin®) to deliver the mazF mRNA into HER2/neu breast cancer cells. The results showed that MazF protein has an ability to induce apoptosis in HER2/neu breast cancer cells. This finding is the first report of the application and delivery of MazF as an anti-cancer agent for the induction of apoptosis in HER2/neu breast cancer cell line. This research suggests cancer therapy that targets only cancer cells but not healthy cells and offers more advantages, e.g., inexpensiveness, target tissue specificity, easy and safe delivery, in comparison to other gene therapy vectors or direct protein administration. Citation Format: Maryam Saffarian, Jeremy Tzeng. Exclusive delivery of mazF in cancer cells by Listeria monocytogenes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4314. doi:10.1158/1538-7445.AM2017-4314
Apoptosis is a gene-directed program that could be inhibited by several factors such as the disruption of the balance between pro-apoptotic and anti-apoptotic proteins, the impaired death receptor signalling or the reduced caspase functions. Several studies have shown that ribonucleases or antibiotics can induce apoptosis in mammalian cells through the shutoff of the protein synthesises. MazF produced by E. coli is a ribonuclease protein that cleaves mRNAs at ACA sequence sites and inhibits their translation. Thus, we hypothesized that the overexpression of MazF proteins in cancer cells could lead to the induction of apoptosis. In the present study, the ACA-less mazF gene was inserted into pSF-T7-EMCV T7 IRES expression plasmid. The mRNAs of mazF gene were synthesized in in vitro conditions, and one μg/ml of the mRNA was transferred into AGS (Gastric adenocarcinoma) cell line. The incidence of apoptosis was detected by conducting caspase 3/7 and Annexin-V assays. The results showed that 99.83% of cells were detached after 18 hours, 0.0086% of cells remained attached without apparent apoptosis, but 0.101% of attached cells were under apoptotic conditions. The results suggest that MazF protein has an ability to induce apoptosis in AGS cells. Since this protein can cleave mRNAs at ACA sites, it could inhibit protein synthesis, reduce the growth rate, and induce apoptosis in cancer cells. This finding is the first report of the application of MazF as an anti-cancer agent for the induction of apoptosis in AGS cell line. Citation Format: Maryam Saffarian, Jeremy Tzeng. The effect of MazF, Escherichia coli ribonuclease, on gastric adenocarcinoma (AGS cells). [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3521.
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