{"id":7659,"date":"2016-02-11T08:12:56","date_gmt":"2016-02-11T08:12:56","guid":{"rendered":"http:\/\/revoscience.com\/en\/?p=7659"},"modified":"2016-02-11T08:12:56","modified_gmt":"2016-02-11T08:12:56","slug":"cotton-candy-machine-may-conceptualize-for-the-creation-of-artificial-organs","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/cotton-candy-machine-may-conceptualize-for-the-creation-of-artificial-organs\/","title":{"rendered":"Cotton Candy Machine may conceptualize for the Creation of Artificial Organs"},"content":{"rendered":"
\"Student<\/a>
Student in the Bellan Lab using a commercial cotton candy machine to spin hydrogel fibers. (Joe Howell \/ Vanderbilt)<\/figcaption><\/figure>\n

An unlikely tool is behind a new technique that could someday lead to the creation of life-sized artificial livers, kidneys and other essential organs: a cotton candy machine.<\/span><\/p>\n

Inspiration struck back when Leon Bellan, assistant professor of mechanical engineering at Vanderbilt University, was just a graduate student studying how nanoscale fibers formed using electrospinning, he tells\u00a0Bioscience Technology<\/em>.\u00a0 The technique uses a very high voltage to produce a fiber-forming jet that deposits nanofibers in a chaotic mat on a surface.<\/span><\/p>\n

\u201cWhen describing this mat, people often use the analogy of silly string, cheese whiz, or cotton candy,\u201d Bellan explained.<\/span><\/p>\n

He soon went to a seminar on the field of tissue engineering, where the speaker mentioned a major hurdle in the field was trouble building a vasculature, particularly capillaries. Capillaries deliver necessary oxygen and nutrients to cells embedded within thick tissue, and without this \u201cinternal plumbing\u201d the cells usually die, Bellan explained.<\/span><\/p>\n

Bellan began thinking about analogies for electrospinning, noticing that his nanofiber-formed nanochannels looked a bit like capillaries but were far too small, and wondered about approaches to make structures larger than the nanochannels.<\/span><\/p>\n

\u201cCotton candy seemed like a promising sacrificial template, and the machine was rather inexpensive and easily obtained,\u201d Bellan said.\u00a0 \u201cPlus how many people get to say they have a cotton candy machine in the lab?\u201d<\/span><\/p>\n

\"Three-dimensional<\/a>
Three-dimensional slab of gelatin that contains a microvascular network. (Bellan Lab \/ Vanderbilt)<\/figcaption><\/figure>\n

So Bellan went to the store and scooped up a machine for about $40 dollars and brought it to his lab, where he was able to make channels that looked a lot like capillaries using spun sugar as a sacrificial template.\u00a0<\/span><\/p>\n

The new technique, described Feb. 4 in theAdvanced Healthcare Materials\u00a0<\/em>journal uses a key material known as PNIPAM, Poly(N-isopropylacrylamide), which is a material that has the unique property of being insoluble in water above 32 degrees Celsius and dissolves in water below 32 degrees Celsius.\u00a0<\/span><\/p>\n

\u201cNow we have figured out a powerful combination of materials that allows this technique to be applied to biomaterials to keep actual living cells alive,\u201d Bellan said.<\/span><\/p>\n

The technique produces a three-dimensional artificial capillary system that keeps cells alive and functional for more than a week, which is much longer than other methods.<\/span><\/p>\n

Important implications for creation of artificial organs<\/span><\/p>\n

Bellan\u2019s \u201ccotton candy\u201d technique helps overcome two challenges in the quest to make artificial organs a reality.\u00a0 One is that the work is done in 3D.\u00a0 He explained that most cell culture work is done in two dimensions, with cells growing on flat surfaces inside of flasks.\u00a0 However, that does not mimic the 3D environment of the body.\u00a0 Those who have moved to 3D cell culture techniques \u201care limited to growing cells in very thin 3D structures because oxygen and nutrients cannot diffuse quickly enough through a thick 3D structure.\u201d\u00a0 Artificial blood vessels are necessary so oxygen and nutrients can flow to the cells and keep them viable.\u00a0<\/span><\/p>\n

\u201cBecause most of the tissues in the body are thicker than a human hair, this is a critical hurdle that must be overcome before we are able to produce full-scale tissues and organs.\u201d<\/span><\/p>\n

In the paper the team demonstrates two new concepts that may help bring the field closer to full-scale artificial organs with functioning cells.<\/span><\/p>\n

Bellan said: \u201cFirst, that we can use the \u201ccotton candy\u201d technique to form capillary-like structures that are able to maintain the viability of cells within very thick artificial tissue (without these structures, the cells end up dying). Second, we demonstrate the use of a thermoresponsive material to form these structures in a \u2018cell friendly\u2019 fashion.\u201d\u00a0<\/span><\/p>\n

He said that this is the first time PNIPAM has been used to pattern fluidic structures, and noted that because the threshold is between body temperature (37 degrees Celsius) and room temperature (25 degrees Celsius) that the process is exceptionally gentle.\u00a0 Previous work has demonstrated PNIPAM\u2019s compatibility with cells.<\/span><\/p>\n

[pullquote]In the paper the team demonstrates two new concepts that may help bring the field closer to full-scale artificial organs with functioning cells.[\/pullquote]<\/p>\n

\u201cUsing the combination of these two concepts, we now have a technique to form complex capillary-like structures in 3D throughout large volumes of artificial organs.\u201d<\/span><\/p>\n

This fiber-based approach enables the formation of capillary-sized vessels, which are much smaller than what can be produced by more traditional techniques using 3D printers.\u00a0 Bellan explained that while microfabrication techniques could create features that are as small as his method \u2013 they could only be made in 2D.<\/span><\/p>\n

\u201cWith the fiber-based approach, we can work in 3D, and at a unique and exciting scale.\u201d<\/span><\/p>\n

How it works<\/span><\/p>\n

Bellan described how the capillaries are created using PNIPM, a polymer which has been used in an array of applications: \u201cWe spin a fibrous mesh of this material using a machine similar to a cotton candy machine.\u00a0 Larger sticks of material are attached to the fibrous mesh to form inlets to which tubing can be attached. We then mix gelatin, cell culture media, cells, and an enzyme called \u2018transglutaminase,\u2019 and pour this mixture over the PNIPAM structure.\u00a0 Everything is then placed in an incubator at 37 degrees Celsius.\u00a0 The enzyme causes bonds to form between the gelatin molecules, and so the gelatin slowly forms an irreversible gel (unlike a typical gelatin dessert mold, which will dissolve again if heated).\u00a0 Once the gel has set, everything is removed from the incubator and allowed to cool to room temperature, at which point the PNIPAM structures dissolve and leave a complex fluidic network behind. This network is within a gelatin gel containing appropriate cells, which are nourished by the vessel system made by the fibers.\u201d\u00a0<\/span><\/p>\n

He said that the team hopes by using PNIPAM it will allow them to work with more fragile types of cells in the future.<\/span><\/p>\n

One area that future work might explore is how to better control the cotton candy technique to optimize the organization of the fibers and resulting channel.\u00a0 As of now scientists do not have exact control over the location of every single channel, but rather the average density and size.<\/span><\/p>\n

Up next, Bellan\u2019s team will look to expand the types of cells used with the technique to form more complex, functional artificial tissues.\u00a0 \u201cFor example, we would like to introduce endothelial cells into the channel network to form a better mimic of a natural capillary.\u201d<\/span><\/p>\n