Adolescents High in Callous-Unemotional Traits are Prone to be Bystanders: The Roles of Moral Disengagement, Moral Identity, and Perceived Social Support.

Bystanders are the most common role that adolescents play in bullying episodes, they have considerable influence on the formation of the victim's experience and the perpetrator's behavior. Based on the social-cognitive model, the current study examined the mediating role of moral disengagement in the association between callous-unemotional traits and bystander behavior and the moderating roles of moral identity and perceived social support. Participants included 2,286 Chinese adolescents aged 11-16 years (49.3% boys; Mage = 13.46, SDage = 0.93). The study showed callous-unemotional traits were significantly and positively associated with bystander behavior and this relation was partially mediated by moral disengagement. Moral identity moderated the relation between callous-unemotional traits and moral disengagement as well as callous-unemotional traits and bystander behavior. Perceived social support moderated in the direct and indirect associations between callous-unemotional traits and bystander behavior via moral disengagement. The relation between callous-unemotional traits and moral disengagement and the relation between callous-unemotional traits and bystander behavior became weaker for adolescents with high perceived social support. Surprisingly, the relation between moral disengagement and bystander behavior became stronger for adolescents with a high level of perceived social support. The results supported two specific patterns of perceived social support: stress-buffering and reverse stress-buffering. The present study contributes to our understanding of the key mechanisms underlying the association between callous-unemotional traits and adolescents' bystander behavior.

Imitation of drug metabolism in human liver and cytotoxicity assay using a microfluidic device coupled to mass spectrometric detection.

In this work, we developed a microfluidic device for the imitation of drug metabolism in human liver and its cytotoxicity on cells. The integrated microfluidic device consists of three sections: (1) bioreactors containing poly(ethylene) glycol (PEG) hydrogel encapsulated human liver microsomes (HLMs); (2) cell culture chambers for cytotoxicity assay; and (3) integrated micro solid-phase extraction (SPE) columns to desalt and concentrate the products of enzymatic reaction. To verify the feasibility of the integrated microchip, we studied uridine 5'-diphosphate-glucuronosyltransferase (UGT) metabolism of acetaminophen (AP) and the cytotoxicity of products on HepG2 cells. The products of the reaction in one region of the device were injected into the cell culture chamber for cytotoxicity assay, while those in another region were directly detected online with an electrospray ionization quadrupole time-of-flight mass spectrometer (ESI-Q-TOF MS) after micro-SPE pre-treatment. Semiquantitative analysis achieved in the experiments could be related to the drug-induced HepG2 cell cytotoxicity. Total analysis time for one product was about 30 min and only less than 4 µg HLM protein was required for one reaction region. The results demonstrated that the established platform could be used to imitate drug metabolism occurring in the human liver, thereby replacing animal experiments in the near future. In addition, the integrated microchip will be a useful tool for drug metabolism studies and cytotoxicity assays, which are pivotal in drug development.

Cell signaling analysis by mass spectrometry under coculture conditions on an integrated microfluidic device.

A microfluidic device was integrated in a controlled coculture system, in which the secreted proteins were qualitatively and semiquantitatively determined by a directly coupled mass spectrometer. PC12 cells and GH3 cells were cocultured under various conditions as a model of the regulation of the organism by the nervous system. A micro-solid phase extraction (SPE) column was integrated in order to remove salts from the cells secretion prior to mass spectrometry detection. A three layer polydimethylsiloxane (PDMS) microfluidic device was fabricated to integrate valves for avoiding contamination between the cells coculture zone and the pretreatment zone. Electrospray ionization (ESI)-quadrupole (Q)-time of flight (TOF)-mass spectrometry was employed to realize highly sensitive qualitative analysis and to implement semiquantitative analysis. Furthermore, cell migrations under various coculture conditions were observed and discussed. The inhibition on growth hormone secretion from GH3 cells by dopamine released from PC12 cells was investigated and demonstrated. Thus, the developed platform provides a useful tool on cell to cell signaling studies for disease monitoring and drug delivery control.

On-chip sample pretreatment using a porous polymer monolithic column for solid-phase microextraction and chemiluminescence determination of catechins in green tea.

A porous polymer monolithic column for solid-phase microextraction and chemiluminescence detection was integrated into a simple microfluidic chip for the extraction and determination of catechins in green tea. The porous polymer was prepared by poly(glycidyl methacrylate-co-ethylene dimethacrylate) and modified with ethylenediamine. Catechins can be concentrated in the porous polymer monolithic column and react with potassium permanganate to give chemiluminescence. The microfluidic chip is reusable with high sensitivity and very low reagent consumption. The on-line preconcentration and detection can be realized without an elution step. The enrichment factor was calculated to be about 20 for catechins. The relative chemiluminescence intensity increased linearly with concentration of catechin from 5.0 × 10(-9) to 1.0 × 10(-6) M and the limit of detection was 1.0 × 10(-9) M. The proposed method was applied to determine catechin in green tea. The recoveries are from 90% to 110% which benefits the actual application for green tea samples.

Rare cell chemiluminescence detection based on aptamer-specific capture in microfluidic channels.

An aptamer-based "sandwich" approach combined with the chemiluminescence (CL) analysis was developed for the capture and detection of rare cells on a microfluidic chip. Aptamers were immobilized on microfluidic channels to achieve capture and isolation of the specific cells from a cell mixture. The capture efficiency for target cells was more than 70% with the purity greater than 97%, when the content of the target cells was between 0.5% and 10% in the initial cell mixture. Gold nanoparticles (Au NPs) modified with aptamers were then added in to bind on the cells and trigger a CL reaction. A satisfactory linearity of the log/log calibration curve between the CL intensity and the number of target cells was observed with a low detection limit of 30 target cells in a 3 µL cell mixture. Spiked whole blood samples were also used to verify the practicality of the present method. This work demonstrated the potential application of the cheap and rapid CL detection into the early diagnosis of cancers.

Fabrication of a gel particle array in a microfluidic device for bioassays of protein and glucose in human urine samples.

This paper describes a simple method for fabricating a series of poly(ethylene glycol) diacrylate (PEG-DA) hydrogel microstructures inside microfluidic channels as probe for proteins and glucose. In order to demonstrate the feasibility of this newly developed system, bovine serum albumin (BSA) was chosen as a model protein. PEG microcolumns were used for the parallel detection of multiple components. Using tetrabromophenol blue (TBPB) and the horseradish peroxidase/glucose oxidase reaction system, bovine serum albumin (BSA) and glucose in human urine were detected by color changes. The color changes for BSA within a concentration range of 1-150 µM, and glucose within a range of 50 mM-2 M could be directly distinguished by eyes or precisely identified by optical microscope. To show the practicability of the gel particle array, protein and glucose concentrations of real human urine samples were determined, resulting in a good correlation with hospital analysis. Notably, only a 5 µL sample was needed for a parallel measurement of both analytes. Conveniently, no special readout equipment or power source was required during the diagnosis process, which is promising for an application in rapid point-of-care diagnosis.

Whole gene amplification and protein separation from a few cells.

Despite the growing interest to explore untapped microbial gene and protein diversity, no single platform has been able to acquire both gene and protein information from just a few cells. We present a microfluidic system that simultaneously performs on-chip capillary electrophoresis for protein analysis and whole genome amplification (WGA), and we demonstrate this by doing both for the same cohort of cyanobacterial cells. This technology opens avenues for studying protein profiles of precious environmental microbial samples and simultaneously accessing genomic information based on WGA.

Particle sorting using a porous membrane in a microfluidic device.

Porous membranes have been fabricated based on the development of the perforated membrane mold [Y. Luo and R. N. Zare, Lab Chip, 2008, 8, 1688-1694] to create a single filter that contains multiple pore sizes ranging from 6.4 to 16.6 µm inside a monolithic three-dimensional poly(dimethylsiloxane) microfluidic structure. By overlapping two filters we are able to achieve smaller pore size openings (2.5 to 3.3 µm). This filter operates without any detectable irreversible clogging, which is achieved using a cross-flow placed in front of each filtration section. The utility of a particle-sorting device that contains this filter is demonstrated by separating polystyrene beads of different diameters with an efficiency greater than 99.9%. Additionally, we demonstrate the effectiveness of this particle-sorting device by separating whole blood samples into white blood cells and red blood cells with platelets.

Microfluidic cell culture and metabolism detection with electrospray ionization quadrupole time-of-flight mass spectrometer.

A novel method for the characterization of drug metabolites was developed by integrating chip-based solid-phase extraction (SPE) with an online electrospray ionization quadrupole time-of-fight mass spectrometer (ESI-Q-TOF-MS). The integrated microfluidic device was composed of circular chambers for cell culture and straight microchannels with shrink ends to pack the solid-phase material for sample cleanup and concentration prior to mass analysis. By connecting the two separated microchannels with polyethylene tubes, drug metabolism studies related to functional units, including cell culture, metabolism generation, sample pretreatment, and detection, were all integrated into the microfluidic device. To verify the feasibility of a drug metabolism study on the microfluidic device, the metabolism of vitamin E in human lung epithelial A549 cells was studied. The metabolites were successfully detected by online ESI-Q-TOF-MS with high sensitivity and short analysis time (8 min). By integrating several parallel channels, the desalting and concentration process could be simultaneously achieved. The total sample pretreatment time only needed about 15 min, and solvent consumption could be reduced to less than 100 microL. All this demonstrated that the developed microfluidic device could be a potential useful tool for cellular drug metabolism research.

Multi-channel microfluidic devices combined with electrospray ionization quadrupole time-of-flight mass spectrometry applied to the monitoring of glutamate release from neuronal cells.

This paper describes an integrated system combining microfluidic devices with electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-Q-TOF-MS) for monitoring cellular chemical release. To demonstrate the feasibility of this new system, the reported carnosine-protection process against Abeta42-induced glutamate released from PC12 cells, was monitored. Poly-L-lysine coated microchannels were used to culture cells. A multi-channel miniature extraction chip (MEC) was integrated into the design to remove salts and protein interference effects. ESI-Q-TOF-MS was employed to realize semi-quantitative and highly sensitive qualitative analysis. The protective effect of carnosine against Abeta42-induced neurotoxicity was evaluated under different conditions in microchannels in parallel. The secretion product analysis, carried out by ESI-Q-TOF-MS, was accomplished in 5 min using only 2.5 microL of solvent. Furthermore, we show that integrated microfluidic devices have significant potential for the analysis of cellular secretions, as well as for medical screening tests and for the diagnosis of specific diseases.

A microfluidic approach for anticancer drug analysis based on hydrogel encapsulated tumor cells.

A novel method based on fluorescence detection of hydrogel encapsulated cells in microchannels was developed for anticancer drug analysis. In this work, human hepatoma HepG2 cells and human lung epithelial A549 cells were simultaneously immobilized inside two different shapes of three-dimensional hydrogel microstructures using photolithography approach on a same array. Microarrays of living cells offer the potential for parallel detection of many cells and thereby enable high-throughput assays. Using a photolithographic setup, we investigated the prepolymer composition and crosslinking parameters that influenced cell viability inside photocrosslinked hydrogels. The viability of cells encapsulated inside hydrogel microstructures was higher than 90% under optimized photocrosslinking conditions. The cells were further cultured under stable conditions and remained viable for at least three days that were able to carry out cell-based assays. Furthermore, we studied the variation of two intracellular redox parameters (glutathione and reactive oxygen species) in anticancer drug-induced apoptosis in HepG2 and A549 cells. Two anticancer drugs exhibited distinct effects on the levels of intracellular glutathione and reactive oxygen species, indicating the selectivity of these drugs on the disturbance of redox balance within cells. The established platform provides a convenient and fast method for monitoring the effect of anticancer drugs on tumor cells, which is very useful for fundamental biomedical research.

Analysis of herbicides on a single C(30) bead via a microfluidic device combined with electrospray ionization quadrupole time-of-flight mass spectrometer.

An integrated system combining microfluidic device with electrospray ionization quadrupole time-of-flight mass spectrometer (ESI-Q-TOF-MS) was developed for detecting a series of herbicides on a single C(30) bead. We presented single C(30) beads manipulation which had absorbed sequential herbicides, based on the precise control of the concentration and absorption time. The simple microchip consisting of a straight channel and a hole in the middle enabled single C(30) bead introduction, transformation and location. ESI-Q-TOF-MS was employed to realize highly sensitive qualitative analysis and implement semi-quantitative analysis. Once the C(30) bead contacted with eluting solution, the solute transferred into eluting and would be detected by ESI-Q-TOF-MS. Depending on desorption curves obtained, accurate and clear characteristic peaks for each analysts were carried out. Our investigations on single-particle analysis showed that the combination of microfluidic device and mass spectrum could reduce the analysis time to 5min and the solvent consumption to 2.5microL, realize high sensitivity detection, and avoid the complex sample pretreatment. The significant potential on analysis of environmental samples on this combination system by single particle was demonstrated.