PSI - Issue 82

Tsanka Dikova et al. / Procedia Structural Integrity 82 (2026) 58–64 Dikova et al. / Structural Integrity Procedia 00 (2026) 000–000

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1. Introduction One of the main objectives of the tissue engineering and regenerative medicine is to replace damaged tissues in the human body with morphologically and functionally sound, manufactured replacements (Lanza et al., 2022). To meet this demand, scientific research is increasingly focusing on the development of engineered medical devices, including bioscaffolds, organoids and organ-on-chip devices (Wang et al., 2025). Bioscaffolds are artificial constructions – porous objects, made by tissue-equivalent material, which possess spatial, mechanical and biological properties, mimicking specific type of tissue in the human body. They are complex structures with highly controlled 3D topography, surface topology, biophysical and biochemical properties, which narrowly affect cell adhesion, proliferation, migration, and differentiation of a specific line of cells into desired direction of development (Krishani et al., 2023). The resulting artificial tissue is capable to replace morphologically, functionally and physically damaged structure in the human body and it’s a promising solution for the ever-growing demand for human tissues and organs with multiple scientific, diagnostic or therapeutic applications in biomedicine (Altyar et al., 2023). The bone scaffolds for in-vivo or in-vitro applications can be readily fabricated with additive manufacturing (AM) from various materials, including polymers, clays, metals and their composites (Banga et al., 2022). The physical structure of the scaffold can be manufactured directly as that of the desired product (Vaezi et al., 2018), or indirectly as a template for molding of the object (Lee et al., 2005). In both cases, the AM is a method of choice for accurate and highly controlled fabrication of the desired bone matrix. The internal structure of the bioscaffold is important for its functionality (Hollister et al., 2005). For the effective engineering of a target tissue, it should include interconnecting spaces with specific shape and size of the pores. Those spaces provide the meanings for proper diffusion of cell culturing media within the device and adequate microenvironment for the adhesion, proliferation and differentiation of a cultured population of cells. For every type of tissue, those spaces are in different shape and size, and they are critical for the development and the fate of the engineered tissue (Mukasheva et al., 2024). Without proper internal architecture, the lack of adequate diffusion of nutrients will lead to the development of a necrotic core within the scaffold, rendering it inefficient and limiting its usability in laboratory or therapeutic setup (Kang et al., 2018). As a rule, bone tissue tends to prefer anisotropic structure, similar to the trabecular geometry in the natural bone. The porosity and minimum/maximum pore size are the main parameters for description of the geometry of empty spaces through the scaffold (Law et al., 2024). These parameters can affect the structural integrity of the scaffold, its biological properties and therapeutic implementation, therefore it should be thoroughly tested through all stages of the bioscaffold designing (Khajehmohammadi et al., 2023). Direct manufacturing can be performed with any 3D printing method, including the most common and available Fused Deposition Modeling (FDM) for thermopolymers (Liu et al., 2004), Stereolithography (SLA) for photopolymers and clays (Will et al., 2008) and Direct Syringe Extrusion of Hydrogels (DSEH) for biopolymers (Gogoi et al., 2024). In this method, the structure of the scaffold is fabricated through the deposition of materials in the solid parts of the object, while some parts remain empty, providing intricate internal structure, necessary for the proper diffusion of nutrients and gases through the device and its functionality respectively. The method is simple and straightforward, but the internal structure of the bioscaffold lacks the complexity, needed for the proper functionality of the device. The indirect manufacturing through template molding requires more sophisticated setup. This method utilizes materials, which can be fully eliminated by dissolution (Xu et al., 2025) or heat treatment (Buckley et al. (2025). This includes two options - FDM or SLA 3D printing of: 1) water and solvent soluble polymers, or 2) wax-containing burnable materials, eliminated through sintering. In this method, the materials are deposited in the empty spaces of the object, creating with high fidelity a negative model of the internal structure of the bioscaffold. The material needed for the final object is poured around the 3D printed mold and solidified through crosslinking or freeze drying. The template material is eliminated through dissolution or heat treatment, creating a detailed object, far surpassing the level of complexity, achievable through direct manufacturing (Lee et al., 2005). This is the main idea of our project for development of scaffolds for bone regeneration and present study shows only the results of its initial stage. The aim of the present paper is to investigate the structure and porosity of polymeric tissue-equivalent bone scaffolds produced by laser stereolithography, which could serve as templates in indirect manufacturing.