Ciencias Exactas y Ciencias de la Salud

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Design and manufacturing proposal of porous bone scaffolds, based on parametric triply periodic minimal surfaces and 3D hydrogel bioprinting.
(Instituto Tecnológico y de Estudios Superiores de Monterrey) Flores Jiménez, Mariana Sofía; Cárdenas Fuentes, Diego Ernesto; RR; García González, Alejandro; School of Engineering and Sciences; Campus Guadalajara; Fuentes Aguilar, Rita
Tissue engineering is a discipline with the aim of regenerating or replacing organs and tissues affected by degenerative diseases or deep injuries. To achieve this, it combines different biomaterials, manufacturing techniques and biochemical factors. In this sense, the creation of scaffolds as a method of cell guidance, attracts the attention of many studies, since, due to their assistance in the healing process, tissue growth can be faster and with a faithful reproduction of the original organ anatomy. Focusing on a more specific area, it appears the demand to develop porous scaffolds for bone regeneration, which require certain characteristics, such as a minimum pore size of 150µm, a porosity gradient to imitate distinct sections of the bone (10% for the cortex, to 80 90% for the inner part), and interconnectivity to create channels for nutrients and blood vessels. This is how a need arises to design a structure with minimal curvature, using a biomaterial that supports high cell viability (> 90%), and an effective seeding ratio, that allows cells to distribute uniformly throughout the entire scaffold. Hence, this work presents solutions for the limitations involved in the combination of a complex geometry design, and its manufacture with biocompatible materials such as hydrogels. After a review of the literature, a proposal is introduced, covering three major areas; obtaining a parametric model of the periodic minimum triple surfaces (TPMS) to facilitate the simulation of the bone, the delimitation of a protocol for 3D extrusion bioprinting, and finally, the selection and aggregation of biomaterials and methodologies to fabricate the complete scaffold. The results show that the use of the TPMS allows to design a geometry that really resembles the shape of the bone, additionally, its approach with a parametric method (using Weierstrass equation and an integration domain) gives rise to an efficient characterization in terms of computational costs, since it facilitates the use of B-splines and NURBS for isogeometric analysis, making it easier to verify that the designed scaffold meets the required characteristics. On the other hand, the scopes of having a protocol for bioprinting lie in a comprehensive study of the printing variables such as extrusion pressure and speed, together with the intrinsic properties of the material like viscosity and gelation time, ending with a method to quantify the resolution obtained. In that way, having a well characterized geometry and process, allows manufacturing to be manipulated by means of instructions, as Gcodes, and the incorporation of other support materials for rapid extrusion without neglecting viability, and in some way, surpassing the obstacles of generating TPMS with hydrogels
Applying a degradation model to describe corrosive behavior in biodegradable stents to explain its influence in mechanical properties
(Instituto Tecnológico y de Estudios Superiores de Monterrey) Figueroa Ramos, Aura Celina; CARDENAS FUENTES, DIEGO ERNESTO; 40783; Cárdenas Fuentes, Diego Ernesto; hermlugo, emipsanchez; Galaz Méndez, Ramsés; Fuentes Aguilar, Rita Quetziquel; Escuela de Ingeniería y Ciencias; Campus Ciudad de México
Cardiovascular diseases are considered the most common cause of death in the entire world. One of the main pathological processes that lead to coronary heart disease is known as atherosclerosis. It consists of an inflammatory process affecting medium to large blood vessels in the human body. Nowadays, treatment is typically site-specific, and the preferred method depends on the level and extent of the occlusion, also called stenosis. The development of intravascular metal stents in the last decade has increased the quality of life of patients suffering from congenital heart disease and coronary interventions. Stent technology can be classified as permanent or temporary stents. Despite their benefits, permanent metallic stents can cause long-term endothelial dysfunction, delayed reendothelialization, thrombogenicity, mismatch of the stent to the vessel size, artifacts with modern imaging techniques, and permanent physical irritation, which in turn, can cause arterial rupture or the formation of an aneurysm. Thus, research focused on designing temporary scaffolding devices to prevent these adverse effects. The development of biodegradable stents must ensure the stabilization of the vessel wall during the healing process, and, after its dissolution, the vessel must stay intact without a foreign body and with its full capacity of vasodilation. The biggest asset of this type of stents is that they disappear after a defined period of time once the vessel is healed. Depending on the patient, the scaffolding effect is required to last for approximately six to twelve months for the vessel to heal and remodel itself. After this period of time, the stent can be harmful, and it must be removed. Research is focusing on the development of biodegradable stents that must meet three main characteristics: biocompatibility, maintained mechanical properties and scaffolding feature during a period of time and controlled degradation rate. Material characteristics, bulk, and surface properties are all major characteristics to consider in the design of a new stent. These materials must be strong enough, with certain mechanical and chemical properties to guarantee their optimal function. Based on this argument, new stent technology is focused on keeping developing BDS to improve their performance by modifying their degradation rates to ensure their scaffolding feature is maintained for as long as the tissue heals itself. Thus, it is essential to understand how biomaterials behave during a degradation process to describe their corrosion behavior after implantation and maintain their structural properties until the tissue is completely healed.

Ciencias Exactas y Ciencias de la Salud

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