Three-dimensional (3D) cell culture systems have gained increasing interest in drug discovery and tissue engineering due to their evident advantages in providing more physiologically relevant information and more predictive data for in vivo tests. In this review, we discuss the characteristics of 3D cell culture systems in comparison to the two-dimensional (2D) monolayer culture, focusing on cell growth conditions, cell proliferation, population, and gene and protein expression profiles. The innovations and development in 3D culture systems for drug discovery over the past 5 years are also reviewed in the article, emphasizing the cellular response to different classes of anticancer drugs, focusing particularly on similarities and differences between 3D and 2D models across the field. The progression and advancement in the application of 3D cell cultures in cell-based biosensors is another focal point of this review.

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In the study, we explored the antimicrobial activities of single-walled carbon nanotubes (SWNTs) and multiwalled carbon nanotubes (MWNTs) with different surface groups to bacterial pathogens, including Gram-negative vs Gram-positive species and rod-shaped vs round-shaped species. We report here for the first time that SWNTs' antimicrobial activity is buffer and concentration dependent, and the charge effect of functional groups on the surface of carbon nanotubes (CNTs) is not a critical factor. SWNTs with surface groups of -OH and -COOH exhibited extremely strong antimicrobial activity to both Gram-positive and Gram-negative bacterial cells in DI water and 0.9% NaCl solution regardless of cell shape, but they did not exhibit antimicrobial activity in PBS buffer and brain heart infusion broth. The antimicrobial activities of these two SWNTs increased with their concentration and treatment time. In DI water or 0.9% NaCl solution, SWNTs-OH and SWNTs-COOH started to show their antimicrobial activity at approximately 50 microg/mL; when their concentration increased to 200-250 microg/mL, they could inactivate 10(7) cfu/mL Salmonella cells in 15 min. The approximately 7 log reduction in viable cell count achieved by this CNTs-based method exceeded those of many reported antimicrobial methods. SWNTs-NH2 only exhibited antimicrobial activity at higher concentrations. MWNTs with surface groups of -OH, -COOH, and -NH2 did not show any significant antimicrobial activity to all tested bacterial cells in any of the tested buffers at concentrations up to 500-875 microg/mL. Formation of cell-CNTs aggregates were studied using fluorescence and electron scanning microscopes. The possible mechanism of SWNTs' antimicrobial activities was also discussed.

A label-free electrochemical impedance immunosensor for rapid detection of Escherichia coli O157:H7 was developed by immobilizing anti-E. coli antibodies onto an indium-tin oxide interdigitated array (IDA) microelectrode. Based on the general electronic equivalent model of an electrochemical cell and the behavior of the IDA microelectrode, an equivalent circuit, consisting of an ohmic resistor of the electrolyte between two electrodes and a double layer capacitor, an electron-transfer resistor, and a Warburg impedance around each electrode, was introduced for interpretation of the impedance components of the IDA microelectrode system. The results showed that the immobilization of antibodies and the binding of E. coli cells to the IDA microelectrode surface increased the electron-transfer resistance, which was directly measured with electrochemical impedance spectroscopy in the presence of [Fe(CN)(6)](3-/4-) as a redox probe. The electron-transfer resistance was correlated with the concentration of E. coli cells in a range from 4.36 x 10(5) to 4.36 x 10(8) cfu/mL with the detection limit of 10(6) cfu/mL.

Carbon dots (or carbon quantum dots in some literature reports), generally small carbon nanoparticles with various surface passivation effects, have attracted widespread attention in recent years, with a rapidly increasing number of research publications. The reported studies covered many aspects of carbon dots, from the development of many new synthetic methodologies to an improved mechanistic elucidation and to the exploration of application opportunities, especially for those in the fluorescence imaging of cells and tissues. There have also been significant advances in the establishment of a shared mechanistic framework for carbon dots and other carbon-based quantum dots, graphene quantum dots in particular.In this article, representative recent studies for more efficient syntheses of better-performing carbon dots are highlighted along with results from explorations of their various bioimaging applications in vitro and in vivo. Similar fluorescence properties and potential imaging uses of some graphene quantum dots are also discussed, toward a more consistent and uniform understanding of phenomenologically different carbon-based quantum dots. Pengju G. Luo has been a faculty member atSherman College of Chiropractic since 2006. He received his medical degree in Clinical Medicine from Tongji Medical University, Wuhan, China in 1997 and his Ph.D. in Microbiology from Clemson University in 2006. His current research interests are in the interdisciplinary areas of nanotechnology and biological and biomedical sciences, focusing on bioapplications of various nanomaterials such as nanoparticles, nanotubes, and carbon dots. Fan Yang obtained his B.S. degree in Chemistry from Zhejiang University, China in 2010. He is currently pursuing his Ph.D. at Clemson University under the supervision of Prof. Ya-Ping Sun. His research focus is on the synthesis of carbon dots for their applications in bioimaging and energy conversions.