Pluronic Guide

Introduction

Pluronic is a trade name of tri-block copolymer also knows as poloxamer. This group of materials is characterized by the presence of hydrophobic poly(propylene oxide) (PPO) sandwiched between two blocks of hydrophilic poly(ethylene oxide) (PEO). By altering the length of the particular blocks it is possible to tune the properties of the resulting hydrogel. Its molecular structure also dictates the self-assembly mechanism of pluronic that is temperature-dependent and is based on micelle formation. When the right temperature is reached PPO block becomes less soluble in water creating a dehydrate core surrounded by hydrated PPE shell. Gel formation can be however reversed by lowering the temperature under the threshold level. 

Pluronic and materials based on it, due to its favorable properties are widely used in tissue engineering applications for creating scaffolds, cell, and drug delivery constructs or as a sacrificial material for bioprinting. [1]

Pluronic is a relatively inert material that can be modified to serve different biological purposes by combination with other bionks, cell attachment peptides, or blending with nanoparticles. To improve its mechanical and biological properties Pluronic was used in combination with alginate [2], pectin [3] or acrylate for additional UV crosslinking [4]. By the addition of aniline tetramer/polyethylenimine researchers also obtained conductive ink [5].

The table below  shows physico-chemical features of Pluronic 127 available in our shop.

Name	Molar mass	Avarage no. of PO units	Avarage no. of EO units	hydrophilic-lipophilic balance	hydrophilic- lipophilic balance	Cloud point	Ref.
Pluronic 127	12600	65.1	200.4	22	2.8	>100	[6]

We strongly recommend Pluronic as starter material for your first steps with bioprinting due to the ease of use and well-characterized printing parameters. However, you will find it also useful in vasculature bioprinting, creating organ-on-chip constructs as well as for coaxial extrusion.

Materials and methods

You can purchase Pluronic 127 in our webshop.

Follow our dedicated protocol to bioprint Pluronic 127.

Troubleshooting

I have problems loading a syringe with Pluronic.

Make sure that Pluronic is cooled to 4°C. Follow the instructions in the Pluronic bioprinting protocol and have a look at our more detailed instructions for loading viscous materials.

Vigours pipetting might turn liquid Pluronic into a gel, so try avoiding that and either choose a pipette with a wide nozzle or pour the material directly from the container into the syringe. 

There are a lot of bubbles in the Pluronic loaded into the syringe.

Air bubbles can be easily trapped in the Pluronic during loading. To remove them place a rubber stopper inside of the syringe and flip it with the tip of the syringe facing upwards. Place the syringe at 4°C in this position and wait until Pluronic because liquid again. The material should run down gravitationally leaving the air at the top of the syringe. Next, push the plunger gently to remove the air. Warm up the syringe to room temperature before printing.

Printing Pluronic results in inconsistent lines.

This might be due to low pressure, too small a nozzle, or bubbles trapped in the gel. Make sure you use printing parameters in the Pluronic bioprinting protocol. To remove air bubbles, check the instructions above. Also make sure that your needle is not clogged – dried Pluronic is diffucult to rehydrate and it can block the needle. In such case – replace it with a fresh one. 

I have troubles to evacuate Pluronic from my bioprinted chips.

To effectively remove Pluronic that served as a sacrificial material you need to cool it down to 4°C. You can achieve it by placing the construct in the fridge or over the ice. Immersing the construct in cold water or PBS and constant agitation at 4°C can help as well. To force the liquid Pluronic try using a suction pump or a syringe with a needle inserted into the channel.

It’s difficult to see the construct printed with Pluronic.

As Pluronic is a transparent material it might be difficult to see it. If you are training using Pluronic or use it for demonstration, we recommend adding a dye into the gel (for example food coloring). The addition of fluorescent microspheres will make the material visible under a fluorescent microscope as well. 

The needle used for printing Pluronic is clogged.

Once Pluronic dries, for example in the needle, it is difficult to rehydrate and remove it. We recommend using a fresh needle.

References

• [1] Zarrintaj, P.,et al, Poloxamer: A versatile tri-block copolymer for biomedical applications. In Acta Biomaterialia (2020). Vol. 110, pp. 37–67. https://doi.org/10.1016/j.actbio.2020.04.028
• [2] 331 J.P. Armstrong, et al , 3D Bio- printing using a templated porous Bioink, Adv. Healthc. Mater. 5 (14) (2016) 1724–1730
• [3] 332 A. Banks , et al, Novel bioprinting method using a pectin based bioink, Technol. Health Care 25 (4) (2017) 651–655
• [4] 18 M. Müller, et al, Nanostructured pluronic hydrogels as bioinks for 3D bioprinting, Biofabrication 7 (3) (2015) 035006
• [5] S.L. Dong , et al, 3D printing of aniline tetramer-grafted-polyethylenimine and pluronic f127 composites for electroactive scaffolds, Macromol. Rapid Commun. 38 (4) (2017)6 84 G. Dumortier , et al, A Review of Poloxamer 407 Pharmaceutical and Pharmacological Characteristics, 23, 2006, pp. 2709–2728