[Show abstract][Hide abstract] ABSTRACT: Recent experimental work has described an elegant pattern of branching in the development of the lung. Multiple forms of branching have been identified, including side branching and tip bifurcation. A particularly interesting feature is the phenomenon of 'orthogonal rotation of the branching plane'. The lung must fill 3D space with the essentially 2D phenomenon of branching. It accomplishes this by rotating the branching plane by 90 degrees with each generation. The mechanisms underlying this rotation are not understood. In general, the programs that underlie branching have been hypothetically attributed to genetic 'subroutines' under the control of a 'global master routine' to invoke particular subroutines at the proper time and location, but the mechanisms of these routines are not known. Here, we demonstrate that fundamental mechanisms, the reaction and diffusion of biochemical morphogens, can create these patterns. We used a Partial Differential Equation model that postulates 3 morphogens, which we identify with specific molecules in lung development. We found that cascades of branching events, including side branching, tip splitting and orthogonal rotation of the branching plane, all emerge immediately from the model, without further assumptions. In addition, we found that one branching mode can be easily switched to another, by increasing or decreasing the values of key parameters. This shows how a 'global master routine' could work by the alteration of a single parameter. Being able to simulate cascades of branching events is necessary to understand the critical features of branching, such as orthogonal rotation of the branching plane between successive generations, and branching mode switch during lung development. Thus, our model provides a paradigm for how genes could possibly act to produce spatial structures. Our low-dimensional model gives a qualitative understanding of how generic physiological mechanisms can produce branching phenomena, and how the system can switch from one branching pattern to another using low-dimensional 'control knobs'. The model provides a number of testable predictions, some of which have already been observed (though not explained) in experimental work.
The Journal of Physiology 11/2013; · 4.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The detection of bacterial pathogens plays an important role in many biomedical applications, including clinical diagnostics, food and water safety, and biosecurity. Most current bacterial detection technologies, however, are unsuitable for use in resource-limited settings where the highest disease burdens often exist. Thus, there is an urgent need to develop portable, user-friendly biosensors capable of rapid detection of multiple pathogens in situ. We report a microfluidic chip for multiplexed detection of bacterial cells that uses antimicrobial peptides (AMPs) with species-specific targeting and binding capabilities. The AMPs are immobilized onto an electrical impedance microsensor array and serve as biorecognition elements for bacterial cell detection. Characterization of peptide immobilization on the sensors revealed robust surface binding via cysteine-gold interactions and vertical alignment relative to the sensor surface. Samples containing Streptococcus mutans and Pseudomonas aeruginosa were loaded in the chip, and both microorganisms were detected at minimum concentrations of 10(5) cfu/mL within 25 min. Measurements performed in a variety of solutions revealed that high-conductivity solutions produced the largest impedance values. By integrating a highly specific bacterial cell capture scheme with rapid electrical detection, this device demonstrates great potential as a next-generation, point-of-care diagnostic platform for the detection of disease-causing pathogenic agents.
Journal of the Association for Laboratory Automation 07/2013; · 1.46 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We present a compact mobile phone platform for rapid, quantitative biomolecular detection. This system consists of an embedded circuit for signal processing and data analysis, and disposable microfluidic chips for fluidic handling and biosensing. Capillary flow is employed for sample loading, processing, and pumping to enhance operational portability and simplicity. Graphical step-by-step instructions displayed on the phone assists the operator through the detection process. After the completion of each measurement, the results are displayed on the screen for immediate assessment and the data is automatically saved to the phone's memory for future analysis and transmission. Validation of this device was carried out by detecting Plasmodium falciparum histidine-rich protein 2 (PfHRP2), an important biomarker for malaria, with a lower limit of detection of 16 ng mL(-1) in human serum. The simple detection process can be carried out with two loading steps and takes 15 min to complete each measurement. Due to its compact size and high performance, this device offers immense potential as a widely accessible, point-of-care diagnostic platform, especially in remote and rural areas. In addition to its impact on global healthcare, this technology is relevant to other important applications including food safety, environmental monitoring and biosecurity.
[Show abstract][Hide abstract] ABSTRACT: We introduce a new biosensing platform for rapid protein detection that combines one of the simplest methods for biomolecular concentration, coffee ring formation, with a sensitive aptamer-based optical detection scheme. In this approach, aptamer beacons are utilized for signal transduction where a fluorescence signal is emitted in the presence of the target molecule. Signal amplification is achieved by concentrating aptamer-target complexes within liquid droplets, resulting in the formation of coffee ring "spots". Surfaces with various chemical coatings were utilized to investigate the correlation between surface hydrophobicity, concentration efficiency and signal amplification. Based on our results, we found that the increase in coffee ring diameter with larger droplet volumes is independent of surface hydrophobicity. Furthermore, we show that highly hydrophobic surfaces produce enhanced particle concentration, via coffee ring formation, resulting in signal intensities 6-fold greater than those on hydrophilic surfaces. To validate this biosensing platform for the detection of clinical samples, we detected α-thrombin in human serum and 4x diluted whole blood. Based on our results, coffee ring spots produced detection signals 40x larger than samples in liquid droplets. Additionally, this biosensor exhibits a lower limit of detection of 2 ng/mL (54 pM) in serum, and 4 ng/mL (105 pM) in blood. Based on its simplicity and high performance, this platform demonstrates immense potential as an inexpensive diagnostic tool for the detection of disease biomarkers, particularly for use in developing countries that lack the resources and facilities required for conventional biodetection practices.
[Show abstract][Hide abstract] ABSTRACT: Identifying potent drug combination from a herbal mixture is usually quite challenging, due to a large number of possible trials. Using an engineering approach of the feedback system control (FSC) scheme, we identified the potential best combinations of four flavonoids, including formononetin, ononin, calycosin, and calycosin-7-O- β -D-glucoside deriving from Astragali Radix (AR; Huangqi), which provided the best biological action at minimal doses. Out of more than one thousand possible combinations, only tens of trials were required to optimize the flavonoid combinations that stimulated a maximal transcriptional activity of hypoxia response element (HRE), a critical regulator for erythropoietin (EPO) transcription, in cultured human embryonic kidney fibroblast (HEK293T). By using FSC scheme, 90% of the work and time can be saved, and the optimized flavonoid combinations increased the HRE mediated transcriptional activity by ~3-fold as compared with individual flavonoid, while the amount of flavonoids was reduced by ~10-fold. Our study suggests that the optimized combination of flavonoids may have strong effect in activating the regulatory element of erythropoietin at very low dosage, which may be used as new source of natural hematopoietic agent. The present work also indicates that the FSC scheme is able to serve as an efficient and model-free approach to optimize the drug combination of different ingredients within a herbal decoction.
Evidence-based Complementary and Alternative Medicine 01/2013; 2013:541436. · 1.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Stem cell-based disease modeling presents unique opportunities for mechanistic elucidation and therapeutic targeting. The stable induction of fate-specific differentiation is an essential prerequisite for stem cell-based strategy. Bone morphogenetic protein 2 (BMP-2) initiates receptor-regulated Smad phosphorylation, leading to the osteogenic differentiation of mesenchymal stromal/stem cells (MSC) in vitro; however, it requires supra-physiological concentrations, presenting a bottleneck problem for large-scale drug screening. Here, we report the use of a double-objective feedback system control (FSC) with a differential evolution (DE) algorithm to identify osteogenic cocktails of extrinsic factors. Cocktails containing significantly reduced doses of BMP-2 in combination with physiologically relevant doses of dexamethasone, ascorbic acid, beta-glycerophosphate, heparin, retinoic acid and vitamin D achieved accelerated in vitro mineralization of mouse and human MSC. These results provide insight into constructive approaches of FSC to determine the applicable functional and physiological environment for MSC in disease modeling, drug screening and tissue engineering.
[Show abstract][Hide abstract] ABSTRACT: Flexible integration of a microfluidic system comprising pumps, valves, and microchannels was realized by an optoelectronic reconfigurable microchannels (OERM) technique. Projecting a low light fluidic device pattern—e.g., pumps, valves, and channels—onto an OERM platform generates Joule heating and melts the substrate in the bright area on the platform; thus, the fluidic system can be reconfigured by changing the projected light pattern. Hexadecane was used as the substrate of the microfluidic system. The volume change of hexadecane during the liquid–solid phase transition was utilized to generate pumping pressure. The system can pump nanoliters of water within several seconds.
[Show abstract][Hide abstract] ABSTRACT: This paper reports a correlation between cellular morphology and the ability of adapting Vesicular stomatitis virus (VSV) infection. A time-lapse approach was employed to track the individual difference between homologous cells in adopting viral infection. Our single-cell analysis indicates that upon viral infection, mature cells that are in spindle shape are less likely to be infected after 24 hour infection. On the other hand, cells undergoing proliferation, which are in rounder shape, tend to adopt much higher viral infection within the same amount of time. This fact suggests cellular morphology may to be an early bio-sensor for viral infection. The findings in this paper could potentially be applied to other viral infection models.
Nano/Micro Engineered and Molecular Systems (NEMS), 2013 8th IEEE International Conference on; 01/2013
[Show abstract][Hide abstract] ABSTRACT: Creating patterns of constituent ingredients are essential for tissue regeneration. Using vascular mesenchymal cells (VMCs) which spontaneously aggregate into multicellular structure, we demonstrate a MEMS-based method to direct the assembly of VMCs into desired tissue patterns. Incorporating the inherent chirality of VMCs revealed by micro-engineered substrates, differences in initial cell plating can be amplified into the formation of exquisite radial structures resembling the crosssectional structure of liver lobules. Furthermore, when cocultured with VMCs, vascular endothelial cells (ECs) tracked with the VMCs and formed a coherent radial pattern, indicating the applicability to heterotypical cell organization. We envision method has broad implications for building instructive microenvironment for tissue engineering.
Nano/Micro Engineered and Molecular Systems (NEMS), 2013 8th IEEE International Conference on; 01/2013
[Show abstract][Hide abstract] ABSTRACT: Rebuilding injured tissue for regenerative medicine requires technologies to reproduce tissue/biomaterials mimicking the natural morphology. To reconstitute the tissue pattern, current approaches include using scaffolds with specific structure to plate cells, guiding cell spreading, or directly moving cells to desired locations. However, the structural complexity is limited. Also, the artificially-defined patterns are usually disorganized by cellular self-organization in the subsequent tissue development, such as cell migration and cell-cell communication. Here, by working in concert with cellular self-organization rather than against it, we experimentally and mathematically demonstrate a method which directs self-organizing vascular mesenchymal cells (VMCs) to assemble into desired multicellular patterns. Incorporating the inherent chirality of VMCs revealed by interfacing with microengineered substrates and VMCs' spontaneous aggregation, differences in distribution of initial cell plating can be amplified into the formation of striking radial structures or concentric rings, mimicking the cross-sectional structure of liver lobules or osteons, respectively. Furthermore, when co-cultured with VMCs, non-pattern-forming endothelial cells (ECs) tracked along the VMCs and formed a coherent radial or ring pattern in a coordinated manner, indicating that this method is applicable to heterotypical cell organization.
[Show abstract][Hide abstract] ABSTRACT: Kidney transplant recipients who have abnormally high creatinine levels in their blood often have allograft dysfunction secondary to rejection. Creatinine has become the preferred marker for renal dysfunction and is readily available in hospital clinical settings. We developed a rapid and accurate polymer-based electrochemical point-of-care (POC) assay for creatinine detection from whole blood to identify allograft dysfunction. The creatinine concentrations of 19 blood samples from transplant recipients were measured directly from clinical serum samples by the conducting polymer-based electrochemical (EC) sensor arrays. These measurements were compared to the traditional clinical laboratory assay. The time required for detection was <5 min from sample loading. Sensitivity of the detection was found to be 0.46 mg/dL of creatinine with only 40 μL sample in the creatinine concentration range of 0 mg/dL to 11.33 mg/dL. Signal levels that were detected electrochemically correlated closely with the creatinine blood concentration detected by the UCLA Ronald Reagan Medical Center traditional clinical laboratory assay (correlation coefficient = 0.94). This work is encouraging for the development of a rapid and accurate POC device for measuring creatinine levels in whole blood.
[Show abstract][Hide abstract] ABSTRACT: The reaction and diffusion of morphogens is a mechanism widely used to explain many spatial patterns in physics, chemistry and developmental biology. However, because experimental control is limited in most biological systems, it is often unclear what mechanisms account for the biological patterns that arise. Here, we study a biological model of cultured vascular mesenchymal cells (VMCs), which normally self-organize into aggregates that form into labyrinthine configurations. We use an experimental control and a mathematical model that includes reacting and diffusing morphogens and a third variable reflecting local cell density. With direct measurements showing that cell motility was increased ninefold and threefold by inhibiting either Rho kinase or non-muscle myosin-II, respectively, our experimental results and mathematical modelling demonstrate that increased motility alters the multicellular pattern of the VMC cultures, from labyrinthine to a pattern of periodic holes. These results suggest implications for the tissue engineering of functional replacements for trabecular or spongy tissue such as endocardium and bone.
Interface focus: a theme supplement of Journal of the Royal Society interface 08/2012; 2(4):457-64. · 2.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Left-right (LR) asymmetry is ubiquitous in animal development. Cytoskeletal chirality was recently reported to specify LR asymmetry in embryogenesis, suggesting that LR asymmetry in tissue morphogenesis is coordinated by single- or multi-cell organizers. Thus, to organize LR asymmetry at multiscale levels of morphogenesis, cells with chirality must also be present in adequate numbers. However, observation of LR asymmetry is rarely reported in cultured cells.
Using cultured vascular mesenchymal cells, we tested whether LR asymmetry occurs at the single cell level and in self-organized multicellular structures.
Using micropatterning, immunofluorescence revealed that adult vascular cells polarized rightward and accumulated stress fibers at an unbiased mechanical interface between adhesive and nonadhesive substrates. Green fluorescent protein transfection revealed that the cells each turned rightward at the interface, aligning into a coherent orientation at 20° relative to the interface axis at confluence. During the subsequent aggregation stage, time-lapse videomicroscopy showed that cells migrated along the same 20° angle into neighboring aggregates, resulting in a macroscale structure with LR asymmetry as parallel, diagonal stripes evenly spaced throughout the culture. Removal of substrate interface by shadow mask-plating, or inhibition of Rho kinase or nonmuscle myosin attenuated stress fiber accumulation and abrogated LR asymmetry of both single-cell polarity and multicellular coherence, suggesting that the interface triggers asymmetry via cytoskeletal mechanics. Examination of other cell types suggests that LR asymmetry is cell-type specific.
Our results show that adult stem cells retain inherent LR asymmetry that elicits de novo macroscale tissue morphogenesis, indicating that mechanical induction is required for cellular LR specification.
Circulation Research 02/2012; 110(4):551-9. · 11.86 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A new bacteria microarray patterning technique is developed by patterning thick polycationic polymers on glass surface, which generates high-coverage and high-precision E. coli cell patterns. Cell immobilization efficiency is greatly improved, compared to conventional monolayer surface patterning approach. Cell viability tests show very low cytotoxicity of polyethyleneimine (PEI). This advancement should further accelerate biomedical and bacteriological researches in the micro scale.
[Show abstract][Hide abstract] ABSTRACT: Infectious diseases cause many molecular assemblies and pathways within cellular signaling networks to function aberrantly. The most effective way to treat complex, diseased cellular networks is to apply multiple drugs that attack the problem from many fronts. However, determining the optimal combination of several drugs at specific dosages to reach an endpoint objective is a daunting task.
In this study, we applied an experimental feedback system control (FSC) method and rapidly identified optimal drug combinations that inhibit herpes simplex virus-1 infection, by only testing less than 0.1% of the total possible drug combinations.
Using antiviral efficacy as the criterion, FSC quickly identified a highly efficacious drug cocktail. This cocktail contained high dose ribavirin. Ribavirin, while being an effective antiviral drug, often induces toxic side effects that are not desirable in a therapeutic drug combination. To screen for less toxic drug combinations, we applied a second FSC search in cascade and used both high antiviral efficacy and low toxicity as criteria. Surprisingly, the new drug combination eliminated the need for ribavirin, but still blocked viral infection in nearly 100% of cases.
This cascade search provides a versatile platform for rapid discovery of new drug combinations that satisfy multiple criteria.
International Journal of Nanomedicine 01/2012; 7:2281-92. · 4.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The detection of bacterial pathogens has far-reaching impacts in various applications including food safety, water quality monitoring and clinical diagnosis. Owing to this, ongoing efforts have focused on developing biodetectors that are portable, offer rapid measurements and high specificity. Here, we present a microfluidic biosensor capable of fast, multiplexed detection of bacterial pathogens. This device utilizes a microsensor array patterned with synthetic, antimicrobial peptides that have species-specific targeting and binding capabilities. The peptides utilized in this work target for two species of bacterium; Streptococcus mutans and Pseudomonas aeruginosa, which are major sources of disease and infection in humans. Samples are autonomously driven within the device via a hydrophilic poly(dimethylsiloxane) PDMS surface coating. An electrical impedance sensing scheme is utilized for cell detection where cell binding results in changes of the sensor's impedance. Using this device, S. mutans and P. aeruginosa cells could be simultaneously detected in a polymicrobial sample within 20 min, demonstrating its potential as a rapid, point-of-care diagnostic technology.
Nano/Molecular Medicine and Engineering (NANOMED), 2012 IEEE 6th International Conference on; 01/2012
[Show abstract][Hide abstract] ABSTRACT: The sensitivity and detection time of an aptamer based biosensor for detecting botulinum neurotoxin (BoNT) depend upon the formation of proper tertiary architecture of aptamer, which closely correlates with the combinatorial effects of multiple types of ions and their concentrations presented in the buffer. Finding the optimal conditions for four different ions at 12 different concentrations, 20,736 possible combinations, by brute force is an extremely laborious and time-consuming task. Here, we introduce a feedback system control (FSC) scheme that can rapidly identify the best combination of components to form the optimal aptamer structure binding to a target molecule. In this study, rapid identification of optimized ionic combinations for electrochemical aptasensor of BoNT type A (BoNT/A) detection has been achieved. Only about 10 iterations with about 50 tests in each iteration are needed to identify the optimal ionic concentration out of the 20,736 possibilities. The most exciting finding was that a very short detection time and high sensitivity could be achieved with the optimized combinational ion buffer. Only a 5-min detection time, compared with hours or even days, was needed for aptamer-based BoNT/A detection with a limit of detection of 40 pg/ml. The methodologies described here can be applied to other multi-parameter chemical systems, which should significantly improve the rate of parameter optimization.
[Show abstract][Hide abstract] ABSTRACT: Purpose - The goal of this research is to demonstrate micro-electro-mechanical systems (MEMS)-based transducers for aircraft maneuvering. Research in wind tunnels have shown that micro-actuators can be used to manipulate leading edge vortices found on aerodynamic surfaces with moderate to highly swept leading edges, such as a delta wing. This has been labeled as the MEMS vortex shift control (MEMS-VSC). The work presented in this paper seeks to detail the evolution of real-world flight tests of this research using remotely piloted vehicles (RPVs). Design/methodology/approach - Four different RPVs were constructed and used for flight tests to demonstrate the ability of using MEMS devices to provide flight control, primarily in the rolling axis. Findings - MEMS devices for high angle-of-attack (AOA) turning flights have been demonstrated and the paper finds that the success of a complex project like the MEMS-VSC requires the marriage of basic science expertise found in academia and the technical expertise found in industry. Research limitations/implications - Owing to the need to test fly the RPVs at low altitudes for video documentation while performing high AOA maneuvers, the attrition of the RPVs becomes the dominant factor to the pace of research. Practical implications - MEMS sensors and actuators can be used to augment flight control at high AOA, where conventional control surfaces typically experiences reduced effectiveness. Separately, the lessons learned from the integration efforts of this research provide a potentially near parallel case study to the development of ornithopter-based micro aerial vehicles. Originality/value - This is the only research-to-date involving the demonstration of the MEMS-VSC on real-world flight vehicles.
[Show abstract][Hide abstract] ABSTRACT: Human pluripotent stem cells hold promising potential in many therapeutics applications including regenerative medicine and drug discovery. Over the past three decades, embryonic stem cell research has illustrated that embryonic stem cells possess two important and distinct properties: the ability to continuously self-renew and the ability to differentiate into all specialized cell types. In this article, we will discuss the continuing evolution of human pluripotent stem cell culture by examining requirements needed for the maintenance of self-renewal in vitro. We will also elaborate on the future direction of the field toward generating a robust and completely defined culture system, which has brought forth collaborations amongst biologists and engineers. As human pluripotent stem cell research progresses towards identifying solutions for debilitating diseases, it will be critical to establish a defined, reproducible and scalable culture system to meet the requirements of these clinical applications.
Regenerative Medicine 09/2011; 6(5):623-34. · 3.87 Impact Factor