Single cell kinase signaling assay using pinched flow coupled droplet microfluidics

Droplet-based microfluidics has shown potential in high throughput single cell assays by encapsulating individual cells in water-in-oil emulsions. Ordering cells in a micro-channel is necessary to encapsulate individual cells into droplets further enhancing the assay efficiency. This is typically limited due to the difficulty of preparing high-density cell solutions and maintaining them without cell aggregation in long channels (>5 cm). In this study, we developed a short pinched flow channel (5 mm) to separate cell aggregates and to form a uniform cell distribution in a droplet-generating platform that encapsulated single cells with >55% encapsulation efficiency beating Poisson encapsulation statistics. Using this platform and commercially available Sox substrates (8-hydroxy-5-(N,N-dimethylsulfonamido)-2-methylquinoline), we have demonstrated a high throughput dynamic single cell signaling assay to measure the activity of receptor tyrosine kinases (RTKs) in lung cancer cells triggered by cell surface ligand binding. The phosphorylation of the substrates resulted in fluorescent emission, showing a sigmoidal increase over a 12 h period. The result exhibited a heterogeneous signaling rate in individual cells and showed various levels of drug resistance when treated with the tyrosine kinase inhibitor, gefitinib.     

A microfluidic co-culture system to monitor tumor-stromal interactions on a chip

The living cells are arranged in a complex natural environment wherein they interact with extracellular matrix and other neighboring cells. Cell-cell interactions, especially those between distinct phenotypes, have attracted particular interest due to the significant physiological relevance they can reveal for both fundamental and applied biomedical research. To study cell-cell interactions, it is necessary to develop co-culture systems, where different cell types can be cultured within the same confined space. Although the current advancement in lab-on-a-chip technology has allowed the creation of in vitro models to mimic the complexity of in vivo environment, it is still rather challenging to create such co-culture systems for easy control of different colonies of cells. In this paper, we have demonstrated a straightforward method for the development of an on-chip co-culture system. It involves a series of steps to selectively change the surface property for discriminative cell seeding and to induce cellular interaction in a co-culture region. Bone marrow stromal cells (HS5) and a liver tumor cell line (HuH7) have been used to demonstrate this co-culture model. The cell migration and cellular interaction have been analyzed using microscopy and biochemical assays. This co-culture system could be used as a disease model to obtain biological insight of pathological progression, as well as a tool to evaluate the efficacy of different drugs for pharmaceutical studies.     

Probing transient protein-mediated DNA linkages using nanoconfinement

We present an analytic technique for probing protein-catalyzed transient DNA loops that is based on nanofluidic channels. In these nanochannels, DNA is forced in a linear configuration that makes loops appear as folds whose size can easily be quantified. Using this technique, we study the interaction between T4 DNA ligase and DNA. We find that T4 DNA ligase binding changes the physical characteristics of the DNA polymer, in particular persistence length and effective width. We find that the rate of DNA fold unrolling is significantly reduced when T4 DNA ligase and ATP are applied to bare DNA. Together with evidence of T4 DNA ligase bridging two different segments of DNA based on AFM imaging, we thus conclude that ligase can transiently stabilize folded DNA configurations by coordinating genetically distant DNA stretches.     

Relative position keeping in satellite formation flying with input saturation

This paper studies a relative position keeping problem in satellite formation flying with input saturation. The relative motion dynamics is designed with polytopic-type uncertainties by considering elliptic and noncoplanar formation, and unknown angular rate and acceleration within some boundary. A composite nonlinear feedback control law is developed by using a low-and-high gain control scheme with an algebraic Riccati inequality (ARI). In the presence of input saturation and disturbances, finite-gain _L∞$L_{\infty }$ stability of the relative motion dynamics is ensured using the proposed control law. Additionally, the domain of attraction for the stability is evaluated by formulating an optimization problem. Through numerical simulations, the validity of the proposed scheme is illustrated.     

Microfluidic size separation of cells and particles using a swinging bucket centrifuge

Biomolecular separation is crucial for downstream analysis. Separation technique mainly relies on centrifugal sedimentation. However, minuscule sample volume separation and extraction is difficult with conventional centrifuge. Furthermore, conventional centrifuge requires density gradient centrifugation which is laborious and time-consuming. To overcome this challenge, we present a novel size-selective bioparticles separation microfluidic chip on a swinging bucket minifuge. Size separation is achieved using passive pressure driven centrifugal fluid flows coupled with centrifugal force acting on the particles within the microfluidic chip. By adopting centrifugal microfluidics on a swinging bucket rotor, we achieved over 95% efficiency in separating mixed 20 μm and 2 μm colloidal dispersions from its liquid medium. Furthermore, by manipulating the hydrodynamic resistance, we performed size separation of mixed microbeads, achieving size efficiency of up to 90%. To further validate our device utility, we loaded spiked whole blood with MCF-7 cells into our microfluidic device and subjected it to centrifugal force for a mere duration of 10 s, thereby achieving a separation efficiency of over 75%. Overall, our centrifugal microfluidic device enables extremely rapid and label-free enrichment of different sized cells and particles with high efficiency.     

Engaging Students with Art-Based S-R-C (Sense of Belonging,Resistance, and Coalition Building) Strategies for Anti-Racism

In this article, we discuss our struggles and efforts to respond to Asian American and Pacific Islander (AAPI) hate crimes and anti-Asian racism, as well as explore ways to address the issues of anti-Asian racism, violence, myths, and stereotypes in the art classroom. We researched and learned from contemporary Asian American artists, attended anti-racism virtual talks, and examined various anti-racism pedagogical approaches. As an outcome of our research to confront anti-racism, we developed S-R-C strategies to engage students with art-based anti-racism, which include facilitating a sense of belonging (S), resisting anti-Asian racism (R), and coalescing with other minority groups and allies (C). These strategies were developed to fully embrace the equity, diversity, and inclusivity of AAPI sequentially and holistically. This article also reports how we use the S-R-C strategies to guide our pre-service art teachers to confront anti-Asian racism and advocate for anti-racism teaching practices.     

Teachers’ and Children’s Differing Views on Relationships and Their Associations with Academic Outcomes

Early Childhood Education Journal - Preschool children’s relationships with their teachers play an important role in their learning and development. Despite this importance, extant research...     

The relationship between university student learning outcomes and participation in social network services,social acceptance and attitude towards school life

Educators try to use social network services (SNSs) in their teaching because they are regarded as beneficial to student learning. However, little research to date has empirically investigated whether the use of an SNS increases university student learning outcomes. A total of 730 university students in the capital area of South Korea participated in the present study. Based on social learning theory, we developed a general structural model that included SNS participation (SP) as an exogenous variable and a range of endogenous variables: cognitive domain learning outcomes, affective domain learning outcomes, social domain learning outcomes, social acceptance (SA) and attitude towards university life (AT). The study results confirmed that the model adequately explained causal relationships between student learning outcomes and SA, AT and SP. SA was identified as a key variable because of its direct effect on learning outcomes. However, SP was considered more important because of its large indirect effects on all learning outcomes through both SA and AT.     

College students’ motivation and learning strategies profiles and academic achievement: a self-determination theory approach

The development of effective self-regulated learning strategies is of interest to educationalists. In this paper, we examine inherent individual difference in self-regulated learning based on Motivated Learning for Learning Questionnaire (MLSQ) using the cluster analytic approach and examine cluster difference in terms of self-determination theory related variables. The sample of the study consisted of 238 junior college students from 12 intact classes. Two adaptive clusters and two maladaptive clusters were uncovered based on the MLSQ, with the adaptive clusters showing better academic grades. Results from the one-way MANOVA showed that the four clusters differed significantly in terms of their needs satisfaction, behavioural regulations, enjoyment, effort and value. The findings supported the importance of needs satisfaction in the development of self-regulated learning behaviour.     

Relationships among organizational commitment, job satisfaction, and learning organization culture in one Korean private organization

The purpose of this study is to identify dynamic relationships among organizational commitment, job satisfaction, and learning organization culture in a Korean private company. Using a sample of 669 employees from five subsidiaries of a Korean conglomerate, this research found that learning organization culture is moderately and positively related to job satisfaction. In addition, organizational commitment, except for continuance commitment, was found to be moderately and positively related to learning organization culture and job satisfaction. This research enables CEOs and HR practitioners to view organizational commitment, learning organization culture, and job satisfaction as important variables that can be applied in their management, interventions, and practices.