Dip TIPS as a Facile and Versatile Method for Fabrication of Polymer Foams with Controlled Shape, Size and Pore Architecture for Bioengineering Applications

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.

In Vivo Vascularization of Anisotropic Channeled Porous Polylactide-Based Capsules for Islet Transplantation: The Effects of Scaffold Architecture and Implantation Site

“…Also, we aim to demonstrate the influence of subcutaneous space on cell infiltration and vascularization in the capsules; and we explored the greater omental pouch for comparison. The polymeric capsules were prepared using the Dip TIPS (dipping followed by thermally-induced phase separation) method recently developed in our lab (Kasoju et al 2014(Kasoju et al , 2015. The capsules were implanted in healthy Brown Norway rats and after 4 weeks, they were excised and analyzed by histochemical and immuno-histochemical stains to assess the biocompatibility and vascular response.…”

Modified porous scaffolds of silk fibroin with mimicked microenvironment based on decellularized pulp/fibronectin for designed performance biomaterials in maxillofacial bone defect

“…The pore sizes of the scaffolds in each group were from randomized areas ( n = 25) to calculate the average pore size. ImageJ software (1.48v, National Institute of Health, Bethesda, MD) was used to measure the pore size in each group …”

“…ImageJ software (1.48v, National Institute of Health, Bethesda, MD) was used to measure the pore size in each group. 27 Weight increase of the scaffolds The coating deposition of the modified scaffolds in all groups was observed by the weights of the scaffolds before and after coating. The percentage of deposition of the components on the scaffolds from the coating solution was calculated from the following formula.…”

Harnessing Hierarchical Nano‐ and Micro‐Fabrication Technologies for Musculoskeletal Tissue Engineering

“…Although freeze‐drying appears to be a rather simple technique, every step of the process should be closely monitored to ensure reproducibility. For example, the solute, the solute concentration, the solute molecular weight, the pH of the solution, the freezing temperature and time, and the freezing rate are critical for pore structure and morphology control. For a more detailed review in the fundamentals of freeze‐drying, see ref.…”

“…Using molds of various configurations, differences in heat transfer rates were achieved during the freeze‐drying process that resulted in scaffolds with complex pore orientations and anisotropic pore size and alignment . Using molds of higher order shapes, the production of macrostructures, such as multichannel conduits or open‐end capsules, tubules and sheets has been reported. Freeze casting has also been used as means to develop metal and ceramic scaffolds with aligned pores and controlled porosity.…”