We introduce photonic crystal enhanced microscopy (PCEM) as a label-free biosensor imaging technique capable of measuring cell surface attachment and attachment modulation. The approach uses a photonic crystal optical resonator surface incorporated into conventional microplate wells and a microscope-based detection instrument that measures shifts in the resonant coupling conditions caused by localized changes in dielectric permittivity at the cell-sensor interface. Four model systems are demonstrated for studying cancer cells, primary cardiac muscle cells, and stem cells. First, HepG2/C3 hepatic carcinoma cells were cultured and observed via PCEM in order to characterize cell adhesion in the context of growth and locomotion. Second, Panc-1 pancreatic cancer cells were used to verify that cell attachment density decreases in response to staurosporine, a drug that induces apoptosis. Third, we used PCEM to confirm the influence of integrin-mediated signaling on primary neonatal cardiomyocyte growth and development. Rounded cardiomyocytes consistently showed decreased cell attachment density as recorded via PCEM, while spreading cells exhibited greater attachment strength as well as increased contractility. Finally, PCEM was used to monitor the morphological changes and extracellular matrix remodeling of porcine adipose-derived stem cells subjected to a forced differentiation protocol. Each of these experiments yielded information regarding cell attachment density without the use of potentially cytotoxic labels, enabling study of the same cells for up to several days.

No abstract

Toxicity tests evaluated chronic and sublethal effects of fog oil (FO) on a freshwater endangered fish. FO is released during military training as an obscurant smoke that can drift into aquatic habitats. Fountain darters, Etheostoma fonticola, of four distinct life stages were exposed under laboratory conditions to three forms of FO. FO was vaporized into smoke and allowed to settle onto water, violently agitated with water, and dosed onto water followed by photo-oxidization by ultraviolet irradiation. Single smoke exposures of spawning adult fish did not affect egg production, egg viability, or adult fish survival in 21-day tests. Multiple daily smoke exposures induced mortality after 5 days for larvae fish. Larvae and juvenile fish were more sensitive than eggs in 96-h lethal concentration (LC50) tests with FO–water mixtures and photo-oxidized FO. Water-soluble FO components photo-modified by ultraviolet radiation were the most toxic, thus indicating the value of examining weathering and aging of chemicals for the best determination of environmental impact.

Photonic crystal surfaces combined with an imaging detection instrument are used for label-free quantification of cell adhesion with intra-cell spatial resolution. The adhesion response to chemical stimuli of cancer cells, cardiac cells, and stem cells are monitored.Cell-surface interactions play a fundamentally important role in nearly every aspect of cellular function. It is now well understood that cell adhesion is more than just a mechanical anchoring to the substratum. Rather, cells adhere to the extracellular matrix (ECM) through focal adhesions, which are complex organelles with over 50 proteins mediating cell attachment. It is known that cells have the ability to modulate the strength of their focal adhesions in order to respond to changes in the environment, such as stimulants, cell toxins or shear stress and that activation (or inhibition) of membrane-coupled surface receptors are important targets for pharmaceutical development. The anchor points for cell attachment are highly dynamic and are constantly broken down and reformed especially during cell proliferation and locomotion. The strength of cell adhesion influences cell growth, differentiation, apoptosis and motility and therefore factors into cell viability, development, inflammation, wound healing and cancer metastasis.To date, few tools exist for quantification and visualization of live cell adhesion under physiological liquid conditions without adversely affecting cell viability. The ability to measure the spatial distribution of cell-surface interactions occurring within the submicron gap between a cell and a surface with resolution sufficient to observe intra-cell variation of adhesion strength without the use of cytotoxic chemical fluorescent tags will enable biologists to gain a more complete understanding of cell behavior and provide a tool for pharmaceutical scientists to measure the effects of chemical compounds at the individual cell level. Label-free biosensor technologies offer an effective method for measuring cell-surface interactions, but only ellipsometry, surface plasmon resonance (SPR) and photonic crystal (PC) biosensor technology offer a means for imaging detection [1]. Because the device structure of a PC biosensor is designed to strictly limit the lateral propagation of coupled light, it offers an opportunity to perform high resolution imaging detection.The PC surfaces used in this work are 1-dimensional subwavlength grating structures (period = 360 nm, depth = 25 nm) that are replica molded from polymer materials upon flexible plastic substrates. The polymer grating is overcoated with a 70 nm thick layer of high refractive index TiO 2 to create a guided mode resonant reflection filter with a resonant wavelength of 617 nm (at normal incidence) and a peak half-width of ~ 5.5 nm when the PC surface is immersed in aqueous media The devices are inexpensively produced over a large surface area and incorporated into standard 6-well microplates commonly used for cell culture experiments. The resonance manifests itself in the far f...