Archive for category: Bioengineering

Above, Agar plate with growing cells

By Ali Etezadkhah, Project Manager

To grow and take shape, cells need a skeleton or scaffold to attach to.  They also need access to nutrients to survive.  There are many different types of cell growth media and they range from pure liquid to a solid gel.  Most people have had experience with the solid type in their Biology class.  Petrie dishes covered with a thin layer of agar are used for growing cells in biology labs.

 Agar is a combination of the linear polysaccharide agarose and heterogeneous mixture of smaller molecules called agaropectin.  Because it is a mixture of different types of molecules, the gelling point of agar is unpredictable.  Controlling the gelling point is very important for 3D printing.  As such, agar is not a good choice as the “ink” for the printer.

A pure form of agarose is available for a number of manufacturers.  It is usually used to separate DNA fragments based on their size and molecular weight.  The procedure is called electrophoresis and utilizes an electric current and a sieve created by the solid agarose gel.  Because it is a pure molecule, agarose has a very tight gelling point, a very desirable property for 3D printing.  In addition to the narrow gelling temperature range, agarose also provides a sturdy gel when solid.  We chose a formulation with very high gel strength to ensure our printed objects hold their shape.  We chose formula A0169-10G manufactured by Sigma-Aldrich.

This agarose formula melts between 86.5 and 89.5 degrees Celsius and gels between 34.5 and 37.5 degrees Celsius.  This hysteresis is a valuable property because it gives us plenty of time to load the gel into the printer after it has melted.  The published gel strength is 1200 gm/cm2, which is the amount of weight needed to depress the gel a distance of 4mm with a 10mm probe without breaking the gel.

Commercial bioprinters use two extruders, one to print pure agarose gel and one to print a watery solution of cells.  This allows the operator to create intricate tissue or organs.  Our printer only has a single extruder so we are limited to printing with a mixture of agarose and living cells.

By Mevan Fernando

Mendel90 Build Manual:  http://reprap.org/wiki/Mendel90_Build_Manual#Getting_Your_Parts
More info: https://github.com/nophead/Mendel90
http://reprap.org/wiki/Mendel90_Buyers_Guide
http://www.thingiverse.com/tag:mendel90

Advantages

• Designed by Nophead (Good parts/service available from Nophead, very detailed, high quality instruction manual, shared his design through his blog: http://hydraraptor.blogspot.com/2011/12/mendel90.html )
• Sturdy structure means faster speeds in the x and y directions
• Easy to assemble
• Not a lot of calibration is required
• Open frame design, allowing it to be worked on easily and mostly disassembled without falling apart
• Ribbon cables are used to prevent cable tangling and friction
• Less need for adjustment
• Great reviews from Mendel90 owners

 Disadvantages

• Critical hole dimension and spacing
• The platform moves in y as well as z directions
• MDF is the cheapest material that could be used to build the frame but changes in weather may cause it to expand or contract. Aluminum is a better choice but it’s more expensive (Materials that could be used for frame: MDF, polycarbonate, acrylic, Dibond, aluminium).

The budget for this project using Nopheads Mendel90 kit would be around $1100.

If we buy our own parts our budget would range from around $600-$800 depending if we could get some of our parts printed out and the material we use for the frame.

 

 

 

By Omair Tariq, Systems and Test Engineer

How bioprinting works:

In order for cells to survive and grow, they need a certain environment. This environment is provided in gel scaffolds, referred to as biopaper in laymen’s term. There are several ways of 3D bioprinting. One of these ways is to print a layer of gel and then a layer of cell in a repetitive manner until the desired structure is obtained. Another method of 3-D bioprinting is to first print a gel scaffold and then facilitate cell growth in the gel scaffold by injecting in cells.

There are various types of gels that can be used as biopaper to meet this purpose: agar, agarose , polyacrylamide gel etc. Due to a lack of availability of funds and equipment, it will be very difficult for us to verify at the cellular level whether the cells have grown correctly or not. Therefore, this semester, we will concentrate on utilizing the 3D bioprinter for the generation of 3D gel scaffolds. 

 

Organovo NovoGen MMX Bioprinter