Dip TIPS as a facile and versatile method for fabrication of polymer foams with controlled shape, size and pore architecture for bioengineering applications.

Naresh Kasoju,Dana Kubies,Marta M Kumorek,Lud'Ka Machová,Jana Kovářová,František Rypáček,Eva Fábryová,Jan Kříž

doi:10.1371/journal.pone.0108792

Abstract

The porous polymer foams act as a template for neotissuegenesis in tissue engineering, and, as a reservoir for cell transplants such as pancreatic islets while simultaneously providing a functional interface with the host body. The fabrication of foams with the controlled shape, size and pore structure is of prime importance in various bioengineering applications. To this end, here we demonstrate a thermally induced phase separation (TIPS) based facile process for the fabrication of polymer foams with a controlled architecture. The setup comprises of a metallic template bar (T), a metallic conducting block (C) and a non-metallic reservoir tube (R), connected in sequence T-C-R. The process hereinafter termed as Dip TIPS, involves the dipping of the T-bar into a polymer solution, followed by filling of the R-tube with a freezing mixture to induce the phase separation of a polymer solution in the immediate vicinity of T-bar; Subsequent free-drying or freeze-extraction steps produced the polymer foams. An easy exchange of the T-bar of a spherical or rectangular shape allowed the fabrication of tubular, open- capsular and flat-sheet shaped foams. A mere change in the quenching time produced the foams with a thickness ranging from hundreds of microns to several millimeters. And, the pore size was conveniently controlled by varying either the polymer concentration or the quenching temperature. Subsequent in vivo studies in brown Norway rats for 4-weeks demonstrated the guided cell infiltration and homogenous cell distribution through the polymer matrix, without any fibrous capsule and necrotic core. In conclusion, the results show the “Dip TIPS” as a facile and adaptable process for the fabrication of anisotropic channeled porous polymer foams of various shapes and sizes for potential applications in tissue engineering, cell transplantation and other related fields.

Highlights

Porous polymer foams are extensively used in various fields of science and technological applications including, but not limited to mechanical, thermal, acoustic and electrical insulations, chemical catalysis, filtration processes and medical devices [1]
The current methodology readily enabled the fabrication of foams in shapes such as openend capsules, tubules and flat 3D sheets, and with variable foam thickness and inner lumen diameters (Figure 2a)
The cross section image (Figure 2c) shows the lengthwise cut pores made by the solvent crystals formed perpendicularly to the lumen

Summary

Introduction

Porous polymer foams are extensively used in various fields of science and technological applications including, but not limited to mechanical, thermal, acoustic and electrical insulations, chemical catalysis, filtration processes and medical devices [1]. A significant academic and commercial interest has been rising in recent years over the use of polymer foams as scaffolds, along with cells and biological factors, to develop biological substitutes that restore, replace or regenerate defective tissues [2]. For consideration in such bioengineering applications, the scaffolds should (a) be biocompatible, (b) be bioresorbable to provide void volume for neotissuegenesis and remodeling, (c) have an appropriate pore structure for efficient nutrient and metabolite exchange, and (e) provide adequate mechanical or structural stability [2,3]. The fabrication of a scaffold with controlled shape, size and pore properties remain a thrust area of research in bioengineering [2]

Methods

Results

Conclusion