Mechanics Predicts Effective Critical-Size Bone Regeneration Using 3D-Printed Bioceramic Scaffolds

Blázquez-Carmona Pablo,Mora-Macías Juan,Martínez-Vázquez Francisco J.,Morgaz Juan,Domínguez Jaime,Reina-Romo Esther 한국조직공학과 재생의학회 2023 조직공학과 재생의학 Vol.20 No.6

BACKGROUND: 3D-printed bioceramic scaffolds have gained popularity due to their controlled microarchitecture and their proven biocompatibility. However, their high brittleness makes their surgical implementation complex for weightbearing bone treatments. Thus, they would require difficult-to-instrument rigid internal fixations that limit a rigorous evaluation of the regeneration progress through the analysis of mechanic-structural parameters. METHODS: We investigated the compatibility of flexible fixations with fragile ceramic implants, and if mechanical monitoring techniques are applicable to bone tissue engineering applications. Tissue engineering experiments were performed on 8 ovine metatarsi. A 15 mm bone segment was directly replaced with a hydroxyapatite scaffold and stabilized by an instrumented Ilizarov-type external fixator. Several in vivo monitoring techniques were employed to assess the mechanical and structural progress of the tissue. RESULTS: The applied surgical protocol succeeded in combining external fixators and subject-specific bioceramic scaffolds without causing fatal fractures of the implant due to stress concentrator. The bearing capacity of the treated limb was initially altered, quantifying a 28–56% reduction of the ground reaction force, which gradually normalized during the consolidation phase. A faster recovery was reported in the bearing capacity, stiffening and bone mineral density of the callus. It acquired a predominant mechanical role over the fixator in the distribution of internal forces after one postsurgical month. CONCLUSION: The bioceramic scaffold significantly accelerated in vivo the bone formation compared to other traditional alternatives in the literature (e.g., distraction osteogenesis). In addition, the implemented assessment techniques allowed an accurate quantitative evaluation of the bone regeneration through mechanical and imaging parameters.

<i>Hypnea musciformis</i>(Cystocloniaceae) from the Yucatan Peninsula: morphological variability in relation to life-cycle phase

Vá,zquez-Delfí,n, Erika,Boo, Ga Hun,Rodrí,guez, Dení,Boo, Sung Min,Robledo, Daniel Informa UK (Taylor Francis) 2016 Phycologia Vol.55 No.2

A reformulated nonlinear model to solve the facility layout problem

Vá,zquez-Romá,n, Richart,Dí,az-Ovalle, Christian O.,Jung, Seungho,Castillo-Borja, Florianne Informa UK (Taylor Francis) 2019 Chemical engineering communications Vol.206 No.4

Progression of Jackhammer Esophagus to Type III Achalasia and Improvement After Extended Myotomy

( Pablo Vázquez García ),( Constanza Ciriza De Los Ríos ),( Fernando Canga Rodríguez-valcárcel ),( Diego Hernández García-gallardo ) 대한소화기 기능성질환·운동학회 2020 Journal of Neurogastroenterology and Motility (JNM Vol.26 No.1

Microstructural evolution and fracture toughness of Al₂O₃/Ti composites

M. Vázquez-Villar,M. Romero-Romo,A. Altamirano-Torres,E. Rocha-Rangel 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.3

The effect of different additions of a metal (Ti) on the microstructure and fracture toughness of Al2O3-based ceramics, as well as the establishment of a route for their processing was analyzed in this study. The samples were prepared by means of mechanical milling and pressureless sintering in an argon atmosphere. Due to the fact of working with very small sizes of powders of both the metal and ceramic, it was possible to reach in sintered products greater values of densification than 95% of their relative density. Measurements of fracture toughness (KIC) evaluated by the fracture indentation method, indicate that this mechanical property had improved with some additions of Ti in the composite, for example KIC for pure alumina processed under the conditions of this study was 3.0MPa·m1/2, whereas, KIC for the composite with 3 vol % Ti was 4.1MPa·m1/2. The microstructure observed in a scanning electron microscopy shows the formation of small and fine metallic interpenetrating networks in the ceramic matrix, that improve in their formation with an increases of Ti in the composite. The effect of different additions of a metal (Ti) on the microstructure and fracture toughness of Al2O3-based ceramics, as well as the establishment of a route for their processing was analyzed in this study. The samples were prepared by means of mechanical milling and pressureless sintering in an argon atmosphere. Due to the fact of working with very small sizes of powders of both the metal and ceramic, it was possible to reach in sintered products greater values of densification than 95% of their relative density. Measurements of fracture toughness (KIC) evaluated by the fracture indentation method, indicate that this mechanical property had improved with some additions of Ti in the composite, for example KIC for pure alumina processed under the conditions of this study was 3.0MPa·m1/2, whereas, KIC for the composite with 3 vol % Ti was 4.1MPa·m1/2. The microstructure observed in a scanning electron microscopy shows the formation of small and fine metallic interpenetrating networks in the ceramic matrix, that improve in their formation with an increases of Ti in the composite.

DNA accumulation on single-anode microelectrode structures and its application in active microarray layout design

Javier Vázquez,JoséLuis Sánchez-Rojás 한국물리학회 2009 Current Applied Physics Vol.9 No.3

The present work investigates, using simulation computer tools and fluorescence microscopy experimental assays, the local distribution of short single-stranded oligonucleotide fragments accumulated on a single microelectrode after the switching of an external dc electrical stimulus for some seconds (up to 75 s). It contributes to fill the existing gap in active microelectronic DNA arrays, where due to the large number of microelectrodes contained in the devices, no or little attention has been given to the final coverage of the individual electrodes by the DNA probes transported onto them, and how it is influenced by the device geometry and other variables like the current magnitude and the transport time. All these parameters play a fundamental role in both the accumulation rate of DNA strands on a polarized electrode and the degree of symmetry of their final distribution, which is convenient to know prior to any active microarray layout design in order to optimize the device performance. The present work investigates, using simulation computer tools and fluorescence microscopy experimental assays, the local distribution of short single-stranded oligonucleotide fragments accumulated on a single microelectrode after the switching of an external dc electrical stimulus for some seconds (up to 75 s). It contributes to fill the existing gap in active microelectronic DNA arrays, where due to the large number of microelectrodes contained in the devices, no or little attention has been given to the final coverage of the individual electrodes by the DNA probes transported onto them, and how it is influenced by the device geometry and other variables like the current magnitude and the transport time. All these parameters play a fundamental role in both the accumulation rate of DNA strands on a polarized electrode and the degree of symmetry of their final distribution, which is convenient to know prior to any active microarray layout design in order to optimize the device performance.

A Disrupted-in-Schizophrenia 1 Gene Variant is Associated with Clinical Symptomatology in Patients with First-Episode Psychosis

Javier Vázquez-Bourgon,Ignacio Mata,Roberto Roiz-Santiáñez,Rosa Ayesa-Arriola,Paula Suárez Pinilla,Diana Tordesillas-Gutiérrez,José Luis Vázquez-Barquero,Benedicto Crespo-Facorro 대한신경정신의학회 2014 PSYCHIATRY INVESTIGATION Vol.11 No.2

Objective DISC1 gene is one of the main candidate genes for schizophrenia since it has been associated to the illness in several populations. Moreover, variations in several DISC1 polymorphisms, and in particular Ser704Cys SNP, have been associated in schizophrenic patients to structural and functional modifications in two brain areas (pre-frontal cortex and hippocampus) that play a central role in the genesis of psychotic symptoms. This study tested the association between Ser704Cys DISC1 polymorphism and the clinical onset of psychosis. Methods Two hundred and thirteen Caucasian drug-naïve patients experiencing a first episode of non-affective psychosis were genotyped for rs821616 (Ser704Cys) SNP of the DISC1 gene. The clinical severity of the illness was assessed using SAPS and SANS scales. Other clinical and socio-demographic variables were recorded to rule out possible confounding effects. Results Patients homozygous for the Ser allele of the Ser704Cys DISC1 SNP had significantly (p<0.05) higher rates at the positive symptoms dimension (SAPS-SANS scales) and hallucinations item, compared to Cys carriers. Conclusion DISC1 gene variations may modulate the clinical severity of the psychosis at the onset of the disorder.

Teacher stress factors and performance in high schools in Ecuador

Esteban Vázquez-Cano,Ana Isabel Holgueras-González 한국교육개발원 2019 KEDI Journal of Educational Policy Vol.16 No.2

The government of Ecuador has invested heavily in education in recent years, and this has affected the socio-educational context and professional role of teachers in that country. This study aims to determine the main factors that can cause stress among teaching professionals in Ecuador, by means of a quantitative methodology, and factor and regression analyses. The results show that the main stress factors affecting teachers relate to poor working conditions (20.3%), a negative professional environment (13.7%), excessive workload (12.5%), assaults and lack of appreciation (9.4%), and performance assessment (3.9%). Thus, the determination of the main stress factors in a specific socio-educational context contributes to the international understanding of the socio-professional profile of the teacher and could favour the measures to minimize teachers’ stress.

Antibiotic resistance and tolerance to simulated gastrointestinal conditions of eight hemolytic Bacillus pumilus isolated from pulque, a traditional Mexican beverage

Raquel González-Vázquez,Lino Mayorga-Reyes,Armando Monroy-López,Luis A. Reyes-Nava,Yadira Rivera-Espinoza,Alejandro Azaola-Espinosa 한국식품과학회 2017 Food Science and Biotechnology Vol.26 No.2

Traditional fermented sap beverages from two provinces of Mexico were studied for the isolation of pathogenic bacteria from these beverages. Eight strains of hemolytic Gram positive bacteria, identified as Bacillus pumilus (B. pumilus), were isolated. They showed different antibiotic resistance profiles and tolerances to the simulated gastrointestinal conditions. All the B. pumilus isolated were resistant to at least one antibiotic tested. Regarding the simulated gastrointestinal conditions, strains S1 and S3 were able to tolerate all the conditions. Hemolytic activity has been associated with a health risk and is often considered as a virulence determinant associated with pathogenicity. Therefore, the hemolytic activity along with the ability to tolerate gastrointestinal conditions and the resistance to antibiotics exhibited by B. pumilus strains S1 and S3 could be associated with a health risk for pulque consumers.

Chitosan-Hydroxyapatite Scaffold for Tissue Engineering in Experimental Lumbar Laminectomy and Posterolateral Spinal Fusion in Wistar Rats

Martin Rodríguez-Vázquez,Rodrigo Ramos-Zúñiga 대한척추외과학회 2020 Asian Spine Journal Vol.14 No.2

Study Design: Experimental study with an animal model. Purpose: To evaluate the role of a chitosan and hydroxyapatite composite for spinal fusion in a lumbar experimental model based on regenerative tissue engineering principles. Overview of Literature: Chitosan and hydroxyapatite represent an alternative biodegradable implant material for tissue engineering and regeneration. The combination of chitosan and hydroxyapatite in a 20:80 ratio could potentiate their individual properties as an implantable composite for experimental laminectomy. Methods: Phase I: design and synthesis of a porous composite scaffold composed of chitosan-hydroxyapatite using a freeze drying technique. Phase II: experimental microsurgical lumbar laminectomy at L5. A total of 35 Wistar rats were categorized into three experimental groups: control (laminectomy alone), experimental (laminectomy with implant), and reference (intact spine) (n=5 per group). Postoperative structural and functional evaluations were performed using computed tomography scans. In addition, radiologic, clinical, histological, and immunohistochemical microstructures were evaluated. Results: At the laminectomy site, the composite implant induced bone regeneration, which was observed in the axial reconstruction of the rat lumbar spine in all cases. Biomechanical changes in the lumbar spine were observed by radiology in both groups after the surgery. The posterolateral space was covered by a bone structure in the treated spine, a condition not seen in the control group. The range of motion was 7.662°±0.81° in the scaffold group versus 20.72°±3.47° in the control group. Histological findings revealed qualitatively more bone tissue formation in the implant group. Conclusions: A composite of chitosan-hydroxyapatite at a 20:80 ratio induced bone formation after experimental laminectomy in rats and led to spinal fusion, which was assessed by radiology and biomechanical tests. No functional complications in posture or walking were observed at 90 days post-surgery, despite biomechanical changes in the spine.