Novel 3D Bioprinting Method To Create Hydrogel Gradients

The primary objective of this project is to utilize hydrogels which are a gel that is composed of polymer(s) suspended in water to create a gradient (the change from one concentration of hydrogel to another). To address this, I used TEMPO-oxidized cellulose nanofibers (T-cnf), mixed with dye diluted with deionized water. The T-cnf was split into two portions and dyed two different colors and then placed into syringes which were heated to 70 degrees Celsius for at least five minutes to ensure smooth extrusion. By using a specialized nozzle, I could plug two syringes into one nozzle that uses a static mixer at the tip to mix the dyed T-cnf. Depending on how fast one syringe extruded versus the other I could change the color and even mix them. With my hands extruding the two syringes I was able to create gradients with the dyed T-cnf and recreate them with different colors. The results indicate that hydrogels can be manipulated to create gradients. Notably, this project uses a hydrogel and dye with large range of temperature it can be extruded under. When recreating this with different hydrogels and fluorescent dyes that can be used with biological material there is a need for more temperature control. This research draws on 3D printers that can do multicolored printing using multiple materials. Bioprinters are 3D printers that use bioinks which are biologically compatible inks (often hydrogels). This research aims to further explore the potential of creating custom bioinks that can be printed in gradients for use in bioprinters in regenerative medicine.

Hello My name is Elizabeth Clark. I’m a bioengineering student and my research project was about creating a new method to 3D bioprint hydrogel gradients, as many cellular functions and processes rely on gradients within the human body.

So for some background, hydrogels are hydrophilic polymers which are primarily comprised of water. A gradient can be thought of if the change of concentration of a property across a material in this case along a line,
So here as mentioned on the previous slide you can see the change in color from blue pink, which can help us visualize the gradient, which can be seen in this picture
In this project, the hydrogel used was TEMPO-oxidized cellulose nanofibers (I will refer to them as T-CNF). The T-CNF was loaded with printer ink the vials right here to visualize the gradients as you had seen in the previous picture, in this case magenta and and cyan ink was used. 2 syringes pictured here were then filled with the dye loaded T-CNF and heated using this blanket heater to 70 ° Celsius and then plugged into this specialized extruder which allowed me to plug in 2 syringes at once those syringes would then extrude into this small chamber with a static mixer to evenly mix the hydrogel and extruded out of a 22-gauge blunt tip needle.
By changing the syringe’s extrusion rate, the color of the gradients could be changed. The syringes could be guided by hand to create different shapes and designs. Gradients were extruded onto weighing paper or on a glass dish and were approximately 8.5-9 cm long, and the color could be changed multiple times in one gradient line.
Throughout this project, consistent gradients were achieved over several weeks, This means future alterations to the dyes utilized and the hydrogel itself could be done to create more biocompatible gradients. It also means a bioprinter could be used to create 3-dimensional gradients that can be used in biomedical engineering and regenerative medicine.