Measurements of scattered light on a microchip flow cytometer with integrated polymer based optical elements.

Flow cytometry is widely used for analyzing microparticles, such as cells and bacteria. In this paper, we report an innovative microsystem, in which several different optical elements (waveguides, lens and fiber-to-waveguide couplers) are integrated with microfluidic channels to form a complete microchip flow cytometer. All the optical elements, the microfluidic system, and the fiber-to-waveguide couplers were defined in one layer of polymer (SU-8, negative photoresist) by standard photolithography. With only a single mask procedure required, all the fabrication and packaging processes can be finished in one day. Polystyrene beads were measured in the microchip flow cytometer, and three signals (forward scattering, large angle scattering and extinction) were measured simultaneously for each bead. To our knowledge this is the first time forward scattered light and incident light extinction were measured in a microsystem using integrated optics. The microsystem can be applied for analyzing different kinds of particles and cells, and can easily be integrated with other microfluidic components.

Removal of PCR inhibitors using dielectrophoresis as a selective filter in a microsystem.

Diagnostic PCR has been used to analyse a wide range of biological materials. Conventional PCR consists of several steps such as sample preparation, template purification, and PCR amplification. PCR is often inhibited by contamination of DNA templates. To increase the sensitivity of the PCR, the removal of PCR inhibitors in sample preparation steps is essential and several methods have been published. The methods are either chemical or based on filtering. Conventional ways of filtering include mechanical filters or washing e.g. by centrifugation. Another way of filtering is the use of electric fields. It has been shown that a cell will experience a force when an inhomogeneous electric field is applied. The effect is called dielectrophoresis (DEP). The resulting force depends on the difference between the internal properties of the cell and the surrounding fluid. DEP has been applied to manipulate cells in many microstructures. In this study, we used DEP as a selective filter for holding cells in a microsystem while the PCR inhibitors were flushed out of the system. Haemoglobin and heparin - natural components of blood - were selected as PCR inhibitors, since the inhibitory effects of these components to PCR have been well documented. The usefulness of DEP in a microsystem to withhold baker's yeast (Saccharomyces cerevisiae) cells while the PCR inhibitors haemoglobin and heparin are removed will be presented and factors that influence the effect of DEP in the microsystem will be discussed. This is the first time dielectrophoresis has been used as a selective filter for removing PCR inhibitors in a microsystem.

Integrating advanced functionality in a microfabricated high-throughput fluorescent-activated cell sorter.

The integration of complete analyses systems "on chip" is one of the great potentials of microfabricated devices. In this study we present a new pressure-driven microfabricated fluorescent-activated cell sorter chip with advanced functional integration. Using this sorter, fluorescent latex beads are sorted from chicken red blood cells, achieving substantial enrichments at a sample throughput of 12000 cells s(-1). As a part of the sorter chip, we have developed a monolithically integrated single step coaxial flow compound for hydrodynamic focusing of samples in flow cytometry and cell sorting. The structure is simple, and can easily be microfabricated and integrated with other microfluidic components. We have designed an integrated chamber on the chip for holding and culturing of the sorted cells. By integrating this chamber, the risk of losing cells during cell handling processes is eliminated. Furthermore, we have also developed integrated optics for cell detection. Our new design contributes to the ongoing efforts for building a fully integrated micro cell sorting and analysing system.

Smoking withdrawal and relapse in head and neck cancer patients.

BACKGROUND: Smoking withdrawal and relapse were characterized among newly diagnosed head and neck cancer patients participating in a physician-delivered smoking cessation intervention. METHODS: Patients completed questionnaires at baseline, 1, 6, and 12 months following intervention delivery. RESULTS: Significant baseline predictors of smoking relapse included medical treatment (XRT versus surgical treatment), stage of change/readiness to quit (precontemplators), age of initiation (younger), and greater addiction (smoking

Gender differences among smokers and quitters in the Working Well Trial.

BACKGROUND: Gender differences in smoking and smoking cessation among participants in the Working Well Trial are characterized. METHODS: A prospective randomized matched-pair evaluation was conducted among 90 predominantly blue-collar worksites. Cross-sectional surveys of employees' tobacco use behaviors were conducted at baseline and after a 2.5-year smoking cessation intervention. Respondents included 5,523 females and 12,313 males at baseline and 4,663 females and 10,919 males at follow-up. The main outcome measures included self-reported continuous smoking abstinence rates for 7 days and for 6 months. RESULTS: Smoking prevalence was significantly higher for women than for men at baseline, but not at follow-up. Variables believed to influence smoking cessation were compared at baseline. Significant gender differences were found for number of cigarettes smoked/day, number of previous quit attempts, job strain, stage of change, and behavioral processes of change. At follow-up, no gender differences in quit rates were observed; however, women in the intervention condition were more likely to quit than women in the control condition, whereas no differences were seen among men by treatment condition. CONCLUSIONS: Gender is not a strong predictor of smoking cessation in this population; however, women were more likely to quit with an intervention than without one.

Smoking cessation and gender: the influence of physiological, psychological, and behavioral factors.

While gender differences in smoking cessation do exist, it is unclear whether these differences affect smoking cessation outcomes. Large population-based surveys have shown few gender differences in the ability to quit or to stay quit; conflicting reports continue to emerge from individual studies, however. Existing evidence evaluating possible gender differences related to physiological, psychological, and behavioral factors is reviewed in this paper. Physiological factors affecting women include: differential sensitivity and tolerance to nicotine, greater withdrawal symptoms, and the importance of timing quit attempts in relation to the menstrual cycle. Behavioral and psychological factors include the following: fear of weight gain, need for social support, depression and negative affect smoking, self-efficacy (confidence in ability to quit), and stage of change (readiness to quit smoking). The majority of studies report gender-pooled data and lack the power to identify differential trends. Gender should be used as a stratification variable in the design of smoking cessation studies whenever feasible. To justify gender-specific interventions, more prospective, randomized studies need to be undertaken.