From Cotton Candy to Capillaries

March 25, 2009 12:00 am0 comments
Virginia Li

Cotton candy often brings back childhood memories of Ferris wheels, pony rides and failed attempts at winning that obscenely large stuffed flamingo at the fair. But for researchers at Cornell’s Nanobiotechnology Center (NBTC) and Weill Medical College, this delightful carnival treat has inspired a leap forward in the field of tissue engineering.
Leon Bellan, then a graduate student in applied engineering and physics, had his revelation while sitting in on one of the weekly NBTC seminars on campus. The topic of discussion that day was the limitations involved in making artificial organs.
The major challenge in developing artificial organs is overcoming the difficulty of reconstructing the human body’s complex circulatory system, which is essential in providing our tissues with oxygen and nutrients. Currently, these three-dimensional networks are gradually assembled one layer at a time. However, today’s fast-paced society cannot afford to wait an entire generation for a finished product.
Bellan and others hope to create such a system using cotton candy as a model. Despite its inventiveness, the process is relatively low-tech, making it quicker and less expensive than previous methods. “All you need is a cotton candy machine, which can cost as little as $40,” Bellan said.
The sacrificial sugar structure, also known as candy, is placed in a non-stick mold and poured over with polydimethylsiloxane (PDMS), a common organic polymer that takes one day to solidify. The mixture is then soaked in hot water and alcohol for several days, allowing the sugary strands to dissolve away. They leave behind a hollow network of microscopic channels.
Using a scanning electron microscope, the researchers found that the channel dimensions resembled those of natural capillaries, ranging from 1-100 micrometers in diameter. They then pumped fluorescently labeled rat blood into the structure to observe its flow characteristics. Since the PDMS structure and the rat’s blood behave very much like their human counterparts, researchers have a model that closely resembles the human microvascular system.
Bellan’s inspiration stemmed from his previous research with nanofibers, which he often compared to cheese whiz, silly string and cotton candy. While cheese whiz and silly string were too large to be considered, Bellan noticed that cotton candy was similar to a human capillary network in terms of size and structure. Despite his personal aversion to the confection, Bellan saw potential in his observation and teamed up with fellow researchers to construct the three-dimensional capillary system.
The next step is finding a way to apply this technique to synthetic tissue that could eventually be implanted into the body. Currently, researchers are creating systems with a blend of biodegradable material and tissue cells, lining the hollow channels with living blood vessel cells. Ideally, the biodegradable substance would slowly decompose as the cells multiply, leaving behind a living vascular construct.
Another concern is the matter of connecting this man-made capillary system to the body’s pre-existing network. Although there is a long way to go, Bellan’s cotton candy model may open doors for the future of artificial organ development. Other possible applications for this technique include the construction of heating, cooling and even self-healing polymers.

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