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Functionalization of PU Foams via Inorganic and Organic Coatings to Improve Cell and Tissue Interactions
1 , 2 , 3, 4 , 5 , 2 , * 1, 2
1  Department of Chemistry, Materials and Chemical Engineering “G. Natta”, Politecnico di Milano, Milan, Italy
2  INSTM, National Consortium of Materials Science and Technology, Local Unit Politecnico di Milano, Piazza Leonardo da Vinci 32, Milan, Italy
3  Center for Translational Research on Autoimmune & Allergic Diseases – CAAD, Novara, Italy;
4  Department of Health Sciences, Università del Piemonte Orientale, Via Solaroli 17, Novara, Italy
5  Department of Translational Medicine, Università del Piemonte Orientale, Via Solaroli 17, Novara, Italy

Published: 26 February 2019 by MDPI in 1st Coatings and Interfaces Web Conference session Biomaterial Surfaces & Interfaces

In this work an innovative method to obtain hybrid bio-functional scaffolds has been developed. Polyether urethane (PU) foam scaffolds were synthetized by one-step gas foaming process. PU foams were coated with crosslinked gelatin hydrogel to promote cell adhesion and proliferation for the regeneration of soft tissues (e.g., adipose tissue). PU foams were coated with inorganic coating (i.e., CaPs) to improve the interaction with osteoblasts for bone tissue regeneration. The functionalized 3D PU porous scaffolds have been characterized investigating morphological properties by SEM and microCT, water uptake and coating stability, and compressive mechanical properties. Adipose tissue derived stem cells (ADSCs), endothelial cells (MS1), amnion mesenchymal cells (AMCs) and chorion mesenchymal cells (CMCs) isolated from human placenta were in vitro cultured on the hybrid functionalized 3D scaffolds. Mechanical properties showed elastic modulus ranging between 15.75 ± 2.14 and 22.9 ± 3.1 kPa; in vitro biological studies showed good cell adhesion, proliferation, and differentiation. In particular, compared to the results with uncoated PU, when cells where differentiated into adipocytes, Oil red O staining confirmed a higher presence of lipid droplets; in case of osteoblasts differentiation, inorganic extracellular matrix deposition was evidenced on CaPs coated PU. The obtained results suggest the important role of an adequate coating on the scaffold to stimulate a better interaction with cells, promoting the differentiation into different cells phenotypes.

Keywords: polyurethane foam; 3D scaffold; coating; crosslinked gelatin; CaPs; micro-CT; mechanical characterization; in vitro cytocompatibility
Comments on this paper
Diaa Aref
Very exciting work. I have just one question just for curiosity. The best of my knowladge that currently their is the 3D printers which can be used to build up materials readily to replacing such damaged tisues, which looks promising as well.
What you think about the advantages that could be in your method for regenerating hard or soft tissues over that methods in terms of their applicability and costs, if we can say like that.
MariaCristina Tanzi
Thank you for your appreciation. About your question, I agree with you that by now 3D printing technologies are very promising. However, there are some limitations that include both the solubility and processability of the material used. In our case, the final foam has a crosslinked structure, therefore difficult to be printed in 3D
Furthermore, the foaming strategy we have developed is very simple and allows us to obtain an open-pore morphology (more than 90% when uncoated) and adequate for soft tissues (such as adipose tissue) and, loaded with calcium phosphates, perfect for cancellous bone

Diaa Aref
future perpectives
Many thanks for your adequate answering.

It is very interesting work it looks so promising. Actually, I still have one more question about its future perspectives, if you kindly help me to understand.

The main goal of such researches are surly to make it works in vivo, I understand that will not be as easy as the in vitro studies. but my question is more fundamental and I still curious to know.

How such prepared final foam will be used in vivo to regenerate the damaged tissues, in other words (the best method of implementation).
What you think about the body portability of this foam after implementation. Have you any ideas and plans in terms of its future in vivo works.

Many thanks for your consideration, and with my all best wishes.
Silvia Fare'
thank you for your comments.
We have performed in the past a preliminary in vivo study (subcutaneous implantation of different PU foams) and we observed a good interaction depending on the chemical structures of the considered foams.
In another study we checked PU foam coated with gelatin to investigate possible adipose tissue regeneration in an in vivo animal model. We observed a good interaction of the coated foam with the surrounding tissue compared to the uncoated foam.
Unfortunately, in vivo animal studies are very expensive ...
MariaCristina Tanzi
Again, many thanks for your interest in our work!

I would like to add some practical information.

As shown in slide 4 of the presentation, the method of PU foams' production need an appropriate mold, then the foam is extracted, deprived of the compact outer skins, then samples and shapes can be cut as desired.

At this step the samples are brittle, but when they are soaked in water or wet with physiological solutions, they become malleable and easily shapeable in the desired shapes to fill tissue defects

The strategy could be that to prepare the samples, adequately modify them for the specific tissue (e.g. adipose tissue or bone), then seeding the appropriate cells and allowing them to grow inside the scaffold. The next step will be to implant the construct into the site to be regenerated

Since the time of degradation of this kind of PU foams is expected to be very long, the scaffold should preserve the mechanical support for long time, allowing the tissue to be reconstructed. Finally, the synthetic scaffold should be completely reabsorbed