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Foams in Tissue Engineering
Published in S. T. Lee, Polymeric Foams, 2022
Chenglong Yu, Zhutong Li, Leah K. Gause, Huaguang Yang, Lih-Sheng Turng
Solvent casting and particulate leaching allow for the preparation of scaffolds with controlled porosity up to 93%, but with limited thickness (<2 mm) [80,81]. The preparation process usually includes: (1) dissolving the polymer into a suitable organic solvent; (2) casting the solution into a mold filled with porogen particles. Such porogen particles could be an inorganic salt (sodium chloride, sodium tartrate, and/or sodium citrate), crystals of saccharose, gelatin spheres, paraffin spheres, or ice particles; (3) waiting for the full evaporation of the solvent; (4) immersing the polymer/porogen composite structure in a bath of a liquid suitable for dissolving the porogen, like the water for dissolving sodium chloride, saccharose and gelatin, or an aliphatic solvent like hexane for dissolving paraffin [81,82]. After the porogen particles are fully dissolved, a porous structure is obtained which could be applied as a tissue engineering scaffold. This relatively simple method is applied widely because of its wide applicability and independently controllable porosity and pore size. The size of the porogen particles will affect the size of the scaffold pores, while the polymer to porogen ratio is directly correlated to the porosity. However, only small thickness ranges could be obtained, and the organic solvents must be fully removed to avoid any possible negative effects to the cells [83,84].
Bionanocomposites
Published in Satya Eswari Jujjavarapu, Krishna Mohan Poluri, Green Polymeric Nanocomposites, 2020
Archita Gupta, Padmini Padmanabhan, Sneha Singh
Solvent-casting with particulate-leaching is the one most widely used for the fabrication of three-dimensional porous scaffolds. In this technique, a particulate/porogen is used primarily for generating pores in the scaffolds. Salt is the most commonly used porogen due to its easy availability and cost-effectiveness. The salt is sieved or milled into fine particles of micron sizes and cast into the mold. Then the required polymer is suspended in the suitable solvent and transferred into the salt-containing mold. Later, the solvent is allowed to evaporate under air and/or in a vacuum and the salt is leached in the presence of water-generating pores of the required size depending upon the size of the salt crystals. Porosity can also be controlled by varying the ratio of salt to polymer. Researchers have reported the use of gelatin and waxy hydrocarbons as porogen during scaffold synthesis. Using them instead of salt has proved to provide better porosity, pore size, cell attachment, and proliferation (Suh et al. 2002 and Shastri et al. 2000). Through this method, thick samples with interconnected pores can be synthesized with increased strength and electrical conductivity by adding the second phase to the casting mold. This technique is easy, inexpensive, simple, and can be efficiently combined with other methods to form BnCs but the use of organic solvents becomes a great disadvantage due to the cytotoxicity they pose.
Mechanical behaviour and vascularisation analysis of tissue engineering scaffolds
Published in Paulo Jorge Bártolo, Artur Jorge Mateus, Fernando da Conceição Batista, Henrique Amorim Almeida, João Manuel Matias, Joel Correia Vasco, Jorge Brites Gaspar, Mário António Correia, Nuno Carpinteiro André, Nuno Fernandes Alves, Paulo Parente Novo, Pedro Gonçalves Martinho, Rui Adriano Carvalho, Virtual and Rapid Manufacturing, 2007
H.A. Almeida, P.J. Bártolo, J.C. Ferreira
Scaffolding materials used in conventional processing techniques are mainly collagens or synthetic biopolymers in the form of fibres and fibrils, gels, foams and membranes. Polymer scaffolds must possess several key characteristics in order to be useful for Tissue Engineering applications. These characteristics are determined by the scaffold fabrication techniques, which have been tailored to create scaffolds that will satisfy the requirements of specific tissues and are not usually generic. Traditional fabrication techniques to produce scaffolds include fibre bonding, solvent casting and particulate leaching, melt moulding and gas foaming (Gomes et al, 2004; (Bártolo et al, 2007 and Reignier et al, 2006). However, the drawbacks of these techniques include the extensive use of highly toxic organic solvents, long fabrication periods, labour-intensive processes, incomplete removal of residual particulates within the polymer matrix, poor repeatability, irregularly shaped pores, insufficient pore interconnectivity and thin structures. Thus, rapid prototyping technology is considered a viable alternative to fabricate scaffolds for tissue engineering, representing a new group of non-conventional fabrication techniques recently introduced in the medical field. The main advantages of rapid prototyping technologies are both the capacity to rapidly produce very complex 3D models and the ability to use various raw materials. In the tissue engineering field, rapid prototyping technologies have been used to produce scaffolds with customised external shape and predefined internal morphology, allowing good control of pore size and distribution (Bártolo, 2006).
Influence of pore sizes in 3D-scaffolds on mechanical properties of scaffolds and survival, distribution, and proliferation of human chondrocytes
Published in Mechanics of Advanced Materials and Structures, 2022
Zahra Abpeikar, Peiman Brouki Milan, Lida Moradi, Maryam Anjomshoa, Shiva Asadpour
In this research, we evaluated the optimum pore size of the PCL scaffold required for cartilage tissue engineering. The PCL scaffolds with various pore sizes (i.e., less than 100 µm, 100 to 150 µm, and greater than 400 µm) were fabricated through the solvent casting and particulate leaching technique. Then prepared constructs were characterized via scanning electron microscopy (SEM), mechanical tests, permeability measurement and scaffold toxicity assays. Finally, the proliferation, and distribution of chondrocytes on the surface of the scaffold were evaluated by H&E staining of cell-loaded scaffolds. Therefore, the aim of this research is to designate the suitable pore sizes for survival, proliferation, and distribution of chondrocytes on the PCL scaffolds along with the evaluation of mechanical features.
Development of biomimetic electrospun polymeric biomaterials for bone tissue engineering. A review
Published in Journal of Biomaterials Science, Polymer Edition, 2019
Sugandha Chahal, Anuj Kumar, Fathima Shahitha Jahir Hussian
In solvent casting and particulate leaching (SCPL), the polymer is dissolved in an organic solvent. Particles, mainly salts, with specific dimensions are then added to the solution. When the solvent evaporates it creates a structure of composite material consisting of the particles together with the polymer as shown in Figure 6. The composite material is then placed in a bath which dissolves the particles, leaving behind a porous structure [74,75]. One of the disadvantages of this technique is the use of organic solvents, which makes it impossible to add pharmacological agents to the membrane during production.