Constructing Evidence and Designing Solutions (SEP6) and RST.11-12.7/8- The authors used previously-known concepts of anatomy, biology, and micro devices to design a lung-on-a-chip that is proven to model the alveolar-capillary interface more realistically than any other available technology. http://www.corestandards.org/ELA-Literacy/

Questions: Does the lung-on-a-chip device function like a normal human alveolar interface? Do the cells grown on the PDMS membrane demonstrate the integrity, viability, and permeability of the typical cell layers found in the lungs?

Methods: Proper growth of cell layers on the PDMS membrane is verified with the fluorescent imaging of the red endothelial cells (that line the alveolar-capillary interface) and the green epithelial cells (that line the alveolar-air interface). Cell-cell tethering is a measure of membrane viability, and is demonstrated with imaging of Occludin and VE Cadherin, two proteins responsible for linking cells together. Typical alveolar cell junctions also bind relatively tightly and produce a surfactant that helps keep airways open during breathing, so electrical resistance readings and fluorescent imaging were used to confirm membrane viability. The human alveolar membrane is usually permeable to immune cells and other proteins, so the group measured the migration of fluorescently-labeled proteins across the PDMS barrier.

Conclusions: The lung-on-a-chip device demonstrated the typical behavior of human alveolar cell membranes when slower-than normal "breathing" was simulated.

A series of interconnected protein and carbohydrate networks that surround and support cells in 3 dimensions. The ECM is also a highway of biological signals for cells, often carrying the information needed to begin cell differentiation

In this paper, Pampaloni et. al discuss how the standard growth of cells on 2 dimensional surfaces does not accurately model organ-level functions such as nutrient/waste transportation. Contemporary research has worked on making 3D cell cultures made of cells and connective tissue, but no one has integrated multiple cell types with connective tissue in an "organ on a chip." In the end, the authors discuss the potential for microdevice technology to address the need for physiologically-relevant organ models in drug screening experiments.

Immune response when tissues react to foreign materials (like silica) and become damaged and swollen

Vicki L. Colvin explores the potential environmental impact of engineered nanomaterials. There is a growing debate on whether the environmental and social costs of nanotechnology outweigh its many benefits. Today, very few studies have been done to study the environmental effects of nanomaterials!

"Determine the central ideas or conclusions of a text; summarize complex concepts, processes, or information presented in a text by paraphrasing them in simpler but still accurate terms." RST.11-12.2

The authors summarize their work by stating that the 'basic' functions of the human alveolar-capillary interface are reconstituted in their lung-on-a-chip device. Most importantly, their work demonstrates that mimicking the lungs in this way and improving on their work in the future can lead to even more realistic 3D models for drug testing. http://www.corestandards.org/Math/

The transwell migration assay is a commonly used technique for studying the migration of particles across a membrane (like the alveolar membrane). Unlike the lung-on-a-chip, which simulated particle translocation with mechanical strain experienced during breathing (figure 4), the transwell system only accounted for the movement of particles over time. This means that the transwell assay is limited in its ability to mimic particle uptake in the alveoli, as it does not accurately mimic the mechanical strain observed in human lung tissues.

A./B./C. Ultrafine silica particles are introduced to the lung-on-a-chip while a 10% cyclic strain is applied to the alveolar capillary interface. The authors observed ICAM-1 expression and neutrophil adhesion on the endothelial (capillary) surface, and measured the reactive oxygen species in the absence and presence of applied mechanical strain. The authors found out that applied mechanical strain increases inflammatory response (ICAM-1 expression, neutrophil adhesion, and ROS production) D. The same procedure described above was applied using superparamagnetic nanoparticles, another irritant that can be harmful to the human lung. This led to only a transient increase in ROS production, indicating a less toxic outcome. E./F./G The authors studied uptake of 100nm polystyrene nanoparticles by the lung mimic device compared to a 2D culture. The transwell system is the gold standard in current toxicology studies, where cells are cultured on two sides of a porous, static membrane. The results show that when mechanical strain is added, the lung-on-a-chip culture uptakes much more nanoparticles than the static transwell culture. H./I./J. In these experiments, the authors compare results to a mouse model. The authors observed that whole mouse lung subject to mechanical ventilation shows a 5-fold increase in nanoparticle absorption compared to lungs without ventilation. These results confirm that lung-on-a-chip device subject to mechanical strain is a better replica of the human lung compared to a 2D static culture.

In this experiment, the authors wanted to put the lung-on-a-chip to the ultimate test: simulating a real toxicology study! The group exposed the 'breathing' lung on chip device to silica nanoparticles. The group quantified the increase in inflammatory response (ICAM-1 expression and ROS production), and the uptake of nanoparticles across the alveolar-capillary interface. They then compared these results with those from a 2D static cell culture study and an animal study (mice). The group found out that the application of mechanical stress results in a drastically higher inflammatory response (increase in ICAM-1 and ROS) and uptake of nanoparticles in the lung-on-chip than the 2D static culture. The results demonstrate the effectiveness of their device in mimicking human lung, which might replace the mice models in the future.

ICAM-1 is a special glycoprotein found on the surface of endothelial cells. ICAM-1 directly contributes to inflammatory responses within the blood vessel wall by increasing endothelial cell activation. ICAM-1 basically calls the immune cells to the rescue!

When a human gets a lung infection, neutrophils are quick to respond to the infected site and ICAM-1 is over-expressed. These previous sources all characterize this aspect of the immune response of a lung infection. The migration of neutrophils and the expression of ICAM-1 inspired the authors as they tested the efficacy of the lung-on-a-chip. For example, the authors use TNF-a to trigger an immune response and measure the expression of ICAM-1 and presence of neutrophils at the exposure site

In the alveolar regions of the human lung, layers of cells coexist and interact to help the body perform gas exchange, maintain tissue structure/function, and keep infections at bay. In this work, the authors account for the distribution of alveolar cell layers by growing two different types of human cells on opposite sides of a membrane: epithelial cells (that line the inner portion of the alveoli and accept fresh air during inhalation) and microvascular endothelial cells (that line the outside of the alveolar space and exchange carbon dioxide waste during exhalation). This membrane is special because it can be stretched out, mimicking the expansion and relaxation of an alveolar sack during breathing! In a variety of tests, the authors confirmed their lung-on-a-chip device to be a viable and reproducible imitation of the human lung.

White blood cells that help you fight infections when exposed to a sickness. Helper T cells that recognize pathogens and help organize the immune response, neutrophils that chew up bacteria, and monocytes (macrophages) that recycle old cells and engulf pathogens are some examples

Pampaloni et. al. discuss the impact that extracellular matrix (ECM) has on cellular growth and development. The three-dimensional distribution of cells in an organ affects how cells--and even other organs--communicate with each other. In this way, "form fits function:" the physical characteristics of a set of tissues can dictate how nutrients and other biomolecules transport between cells. Drug screening is primarily performed on 2D cell cultures, where the functions of human tissues are not accurately represented. This work aims to directly address this issue

Referring to the mimicked inhaling and exhaling of the lungs over long periods of time. The human lungs experience 672,768,000+ breaths in a lifetime and can regenerate themselves as you age. The lung-on-a-chip must be able to handle the tissue stretching associated with normal breathing if it is to be considered a true "biomimicked lung device"

Takayama et. al report a new way of manufacturing microchannels out of PDMS that can be smaller than the width of a human hair! The process involves the controlled washing of a PDMS slab with chemicals. The authors have high hopes for their technology: "We believe that these procedures will enable new types of studies in fundamental cell biology, and that they will also be useful in the microfabrication of devices that require a high-level of control over the behavior of cells"

Small particles of silicon dioxide, which when inhaled can cause pulmonary damage and even lung cancer

The human lung goes through a lot of changes over time! Not only must it handle breathing in and out every minute of every day, but the lungs have to deal with all sorts of infectious pathogens. If scientists are to make human-like 3D cell cultures for drug testing, they must be able to replicate the lungs' day-to-day functions. This work is very special because it represents the culmination of years of research into making a proper artificial lung-on-a-chip. The researchers report that their device not only inhales and exhales like a normal lung, but can also fight infections with an immune response! This means that any drug testing performed on this device has a higher potential to mimic the human lung response than a standard 2D cell culture

The following research papers discuss the potential for microfluidic devices to assess the problems with modern 3D tissue models. For example, Langer et al. discuss how standard cell cultures cannot replicate the repetitive mechanical strain that human organs such as lungs and gut undergo every day. The authors also discuss how oxygen and protein transport through these tissue scaffolds does not accurately mimic human conditions. While attempts have been made to improve cell-cell connectivity and nutrient transport in 3D cultures, microfluidic technology provides a potential pathway to generate accurate and viable organ models.

A big goal in biomedical science is to make artificial organs that can be used to save lives. However, generating these new organs as well as integrating them into a human body has remained challenging. The cited articles discuss how hard it is to make organs that accurately mimic their human counterparts. If scientists could fabricate functional tissues and organs with integrated blood vessels to sustain them, artificial organ transplants could become a major therapeutic tool!

Davilla et. al. discuss the advantages and disadvantages of lab-grown cell cultures that can mimic the function of kidneys and livers. While these cultures are inexpensive and can help measure drug-specific tissue interactions at a cellular/molecular level, the models do not accurately account for molecular transport and toxicity interactions between tissues and organs. This is because the cultures are grown on a flat surface, rather than in a 3D organ-like configuration. The authors conclude that cell culture models are a step towards pharmaceutical testing that does not use animal models, but further development is needed to effectively mimic the human body's reactions to various drugs.

A very small device, whose dimensions are on the micro scale (under 1mm). Often referenced in the context of biomechanical-electric system (bioMEM)

The human body has lots of moving internal parts. Repeated and regular contractions caused by the movement of food through the intestines puts pressure on surrounding tissues. Another example is the human lungs expanding and contracting during breathing.

Questions: Can the lung-on-a-chip device produce an immune response like normal immune cells would in the lungs?

Methods: immune cells and proteins that trigger an immune cell response were exposed to the cells on the chip's membrane. The adhesion and migration of the immune cells on the alveolar membrane was shown with microscopic images. The immune response and inflammation of the alveolar cells was shown to occur within 6 minutes. Lastly, the lung-on-a-chip was exposed to a bacterial infection and immune response was measured like before.

results: The immune response of the lung-on-a-chip device mimic the response found in the human lung. When infected with bacteria, the alveolar layers deployed the appropriate immune cells in a timely fashion. This means that the lung-on-a-chip can effectively mimic the immune response of the human lung.

Question(s) - Can we create a chambered device that mimics the small pockets of tissues in the lungs where oxygen diffuses into the blood? Can we fabricate this device so that it reliably and accurately demonstrates the inhaling and exhaling of lungs? Will the device have similar integrity, viability, and permeability to typical alveolar-capillary interfaces found in humans?

Methods: A layer of PDMS is sandwiched between two halves of a molded chamber to make three parallel air pathways on the chip. the same type of epithelial and endothelial cells found in the linings of a human lung are cultured onto opposite sides of the PDMS membrane, and air is pumped in and out of the chambers in the same way that air goes into and out of the lungs during breathing.

results - the "inhaling" and "exhaling" air channels are colored blue and red on a fully-functional lung-on-a-chip device, and cells grown on the PDMS layer actively undergo the same mechanical stresses that their real-life counterparts experience in the human body. The entire lung-on-a-chip system measures roughly 1-2cm long, and external pumping mechanisms drive air in and out of the device.

A molding technique that involves casting materials like PDMS into channels or chambers. This technique is used in microdevice fabrication because it is cost-effective and relatively simple to perform.

Tiny sacs where the lungs and the blood exchange oxygen and carbon dioxide during the process of breathing in and out. Each sac is lined with cells that allow gases to diffuse in and out of the lung.

Blood vessels like veins and arteries

In this review article by famous tissue engineer Donald Ingber, there is great discussion of all the factors that affect cellular growth and development. In particular, the mechanical forces of tension and compression (as we see in the lungs when we inhale and exhale) can play a very important role in how cells divide, grow, and communicate. 3D cell cultures and lung-on-a-chip technology offer the potential to mimic these mechanical forces that we observe in the body. This accounting for human-like biology in drug testing has the potential to make animal studies obsolete!

Having enough cells grown on a surface to cover the entire area. Here, air is introduced to the lung microchip once there is enough cells to cover the entire membrane surface area.