Francisco J Rojo

Francisco J Rojo
Universidad Politécnica de Madrid | UPM · Centre for Biomedical Technology

PhD.

About

56
Publications
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Introduction
Biomaterials Mechanical behaviour of biological materials

Publications

Publications (56)
Article
Silk gut fibers were produced from the silkworm Samia cynthia ricini silk glands by the usual procedure of immersion in a mildly acidic solution and subsequent stretching. The morphology of the silk guts was assessed by scanning electron microscopy, and their microstructure was assessed by infrared spectroscopy and X-ray diffraction. It was found t...
Article
Damaged complex modular organs repair is a current clinical challenge in which one of the primary goals is to keep their biological response. An interesting case of study it is the porcine esophagus since it is a tubular muscular tissue selected as raw material for tissue engineering. The design of esophageal constructs can draw on properties of th...
Article
The expression of spidroins in the major ampullate, minor ampullate, flagelliform, and tubuliform silk glands of Trichonephila clavipes spiders was analyzed using proteomics analysis techniques. Spidroin peptides were identified and assigned to different gene products based on sequence concurrence when compared with the whole genome of the spider....
Article
Full-text available
Age-related Macular Degeneration (AMD) is an up-to-date untreatable chronic neurodegenerative eye disease of multifactorial origin, and the main causes of blindness in over 65 y.o. people. It is characterized by a slow progression and the presence of a multitude of factors, highlighting those related to diet, genetic heritage and environmental cond...
Article
Full-text available
Age-related Macular Degeneration (AMD) is an up-to-date untreatable chronic neurodegenerative eye disease of multifactorial origin, and the main causes of blindness in over 65 years old people. It is characterized by a slow progression and the presence of a multitude of factors, highlighting those related to diet, genetic heritage and environmental...
Article
Introduction Rotator cuff disorders present a high retear rate despite advances in surgical treatment. Tissue engineering could therefore be interesting in order to try to enhance a more biological repair. RhBMP-2 is one of the most osteogenic growth factors and it also induces the formation of collagen type I. However, it has a short half-life and...
Article
Full-text available
Age-related macular degeneration is an incurable chronic neurodegenerative disease, causing progressive loss of the central vision and even blindness. Up-to-date therapeutic approaches can only slow down he progression of the disease. Objective: Feasibility study for a multilayered, silk fibroin-based, 3D biohybrid retina. Approach: Fabrication...
Article
This work presents a new family of bio-hybrid light-emitting diodes (Bio-HLEDs) using all-bio color down-converting coatings that combine silk fibroin (SF) as a packaging matrix and fluorescent proteins (FPs) as emitters. The thermal, mechanical, optical, and luminescent features of the FP–SF bio-phosphors were optimized with respect to the blend c...
Article
Current avian migration patterns in temperate regions have been developed during the glacial retreat and subsequent colonization of the ice‐free areas during the Holocene. This process resulted in a geographic gradient of greater seasonality as latitude increased that favoured migration‐related morphological and physiological (co)adaptations. Most...
Article
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Physical and cognitive disabilities are hallmarks of a variety of neurological diseases. Stem cell-based therapies are promising solutions to neuroprotect and repair the injured brain and overcome the limited capacity of the central nervous system to recover from damage. It is widely accepted that most benefits of different exogenously transplanted...
Article
Atomic force microscopy (AFM) is a powerful tool in Biology due to the possibility of identifying and locating single molecules at a subnanometer scale. Performing these experiments requires the usage of functionalized AFM tips to which sensing molecules can be attached. In this work the possibility of functionalizing AFM cantilevers and tips using...
Article
The aim of this study was to evaluate quantitatively the fracture —by tear and delamination— of bovine pericardium tissues which are usually employed for the manufacture of bioprosthetic valves. A large number of samples (77) were tested in root-to-apex and circumferential directions, according to a standardised tear test (ASTM D 1938). Before perf...
Article
To these days, the production of a small diameter vascular graft (< 6 mm) with an appropriate and permanent response is still challenging. The mismatch in the grafts mechanical properties is one of the principal causes of failure, therefore their complete mechanical characterization is fundamental. In this work the mechanical response of electrospu...
Article
The aim of this study was to evaluate the variation of hardness with fatigue in calf pericardium, a biomaterial commonly used in bioprosthetic heart valves, and its relationship with the energy dissipated during the first fatigue cycle that has been shown to be a predictor of fatigue-life (García Páez et al., 2006, 2007; Rojo et al., 2010). Fatigue...
Article
Full-text available
Our main objective was to biologically improve rotator cuff healing in an elderly rat model using mesenchymal stem cells (MSCs) in combination with a collagen membrane and compared against other current techniques. A chronic rotator cuff tear injury model was developed by unilaterally detaching the supraspinatus (SP) tendons of Sprague-Dawley rats....
Article
Full-text available
The mechanical properties of aortic wall, both healthy and pathological, are needed in order to develop and improve diagnostic and interventional criteria, and for the development of mechanical models to assess arterial integrity. This study focuses on the mechanical behaviour and rupture conditions of the human ascending aorta and its relationship...
Article
Full-text available
This work presents experiments and modelling aimed at characterising the passive mechanical behaviour of the human thoracic descending aorta. To this end, uniaxial tension and pressurisation tests on healthy samples corresponding to newborn, young and adult arteries are performed. Then, the tensile measurements are used to calibrate the material pa...
Article
Bovine pericardium is a collagenous tissue commonly used as a natural biomaterial in the fabrication of cardiovascular devices. For tissue engineering purposes, this xenogeneic biomaterial must be decellularized to remove cellular antigens. With this in mind, three decellularization protocols were compared in terms of their effectiveness to extract...
Article
Calf pericardium, similar to that used in the manufacturing of prosthetic valve cusps, was fatigue tested. After six batches of 100 cycles of 1 MPa of loading pressure, half of the samples broke. The mean energy dissipated in the first cycle by the surviving samples was 0.16 J, which is lower than the 0.28 J dissipated by the specimens that broke (...
Article
Full-text available
In recent times, significant effort has been made to understand the mechanical behaviour of the arterial wall and how it is affected by the different vascular pathologies. However, to be able to interpret the results correctly, it is essential that the influence of other factors, such as aging or anisotropy, be understood. Knowledge of mechanical b...
Article
Full-text available
The lack of reliable mechanical data on coronary arteries and, more specifically, on their wall strength hampers the application of numerical models and simulations to vascular problems, and precludes physicians from knowing in advance the response of coronary arteries to the different interventions. Studies of the mechanical properties of coronary...
Article
Potato crisps were ranked in order of crispness by a taste panel. The crisps were then tested mechanically, using Weibull’s model for the analysis of the data. This showed that a crisper crisp breaks at a higher force. The speed of breakdown of the crisp during chewing is proportional to the Weibull modulus. The Weibull analysis enables the scatter...
Article
Biomechanical and functional properties of tissue engineered vascular grafts must be similar to those observed in native vessels. This supposes a complete mechanical and structural characterization of the blood vessels. To this end, static and dynamic mechanical tests performed in the sheep thoracic and abdominal aorta and the cava vein were contra...
Article
Full-text available
While the situation of tissue donation and transplantation differs between Latin American and European countries, a common problem is tissue deficiency. Hence, at present, there is a pressing need to generate alternatives so as to increase the possibilities of obtaining the requested materials. Consequently, it would be of significant interest to e...
Article
Data from the literature report febrile reactions prior to myocardial infarction in patients with normal coronary arteries and that coronary syndromes seem to be triggered by bacterial and viral infections, being fever the common symptom. The thermo-mechanical behavior of thoracic aortas of New Zealand White rabbits with different degrees of athero...
Article
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Viscoelastic models can be used to better understand arterial wall mechanics in physiological and pathological conditions. The arterial wall reveals very slow time-dependent decays in uniaxial stress-relaxation experiments, coherent with weak power-law functions. Quasi-linear viscoelastic (QLV) theory was successfully applied to modeling such respo...
Article
Full-text available
Arterial viscoelasticity can be described using stress-relaxation experiments. To fit these curves, models with springs and dashpots, based on differential equations, were widely studied. However, uniaxial tests in arteries show particular shapes with an initial steep decay and a slow asymptotic relaxation. Recently, fractional order derivatives we...
Article
Full-text available
There is a pressing need to obtain adequate vascular substitutes for arterial by-pass or reconstruction. Since the performance of venous and commercially prosthetic grafts is not ideal and the availability of autologous arteries is limited, the use of cryopreserved arteries has emerged as a very attractive alternative. In this sense, the developmen...
Article
Full-text available
This work explores for the first time the effects of temperature increments on the development of high shear stresses between plaque and arterial wall due to their different dilatational properties. Data from the literature report febrile reactions prior to myocardial infarction in patients with normal coronary arteries and that coronary syndromes...
Article
Full-text available
Las placas de ateroma de las paredes arteriales son acumulaciones de lípidos y otras sustancias que modifican las propiedades de la pared vascular. El principal problema que presentan estas placas es su rotura y despegue de la pared, con la posibilidad de obstruir la circulación de la sangre. En este trabajo se analiza, mediante un modelo animal en...
Article
The Weibull modulus of potato crisps is about 4, comparable with ceramic materials, with a characteristic strength of about 1.5 MPa. This combination of brittleness and weakness gives crispness. The critical stress intensity factor (KIC) and the energy of fracture (R) are around 0.12 MPa and 45 J m–2, respectively. There was no significant differen...
Conference Paper
Full-text available
En este trabajo se caracteriza el comportamiento mecánico y la rotura de la pared de la aorta ascendente humana y su dependencia de distintas patologías. Para tal fin se realiza un análisis histológico y ensayos de tracción in-vitro sobre tejido aórtico de tres grupos de pacientes: Sanos (grupo de control), con válvula aórtica bicúspide y con el sí...
Article
Introduction and objectives The thermomechanical behavior of human arteries is still not well characterized despite its importance for understanding arterial physiology, and for evaluating and improving surgical procedures. The aim of this study was to provide, for the first time, experimental data illustrating how the mechanical responses of two t...
Article
The thermomechanical behavior of human arteries is still not well characterized despite its importance for understanding arterial physiology, and for evaluating and improving surgical procedures. The aim of this study was to provide, for the first time, experimental data illustrating how the mechanical responses of two types of human artery-the car...
Article
The thermomechanical behavior of human arteries is still not well characterized despite its importance for understanding arterial physiology, and for evaluating and improving surgical procedures. The aim of this study was to provide, for the first time, experimental data illustrating how the mechanical responses of two types of human artery -the ca...
Article
Background This work explores for the first time the effects of temperature increments on the development of high shear stresses between plaque and arterial wall due to their different dilatational properties. Data from the literature report febrile reactions prior to myocardial infarction in patients with normal coronary arteries and that coronary...
Article
This paper investigates the tensile properties and brittle fracture of dry durum semolina fibers (spaghetti), and provides quantitative values for the strength and toughness of this material. Tensile tests on spaghetti of different lengths were performed, and the results correlated with the micrographic observation of fracture surfaces and flaw dis...
Article
Stress intensity factors for inner circular cracks placed eccentrically in a fiber with round cross section were computed and are presented in this paper in both analytical and graphical form. The crack plane was perpendicular to the fiber axis and remote tensile loading was assumed. The stress intensity factors were numerically computed using the...
Article
Full-text available
The scope of this paper is the study of the size effect in multilayered composite materials. These kinds of materials are made of two components alternating in consecutive layers, and the good performances achieved with the combination makes its study very interesting. Said study is carried out using the cohesive crack's model, and calculations are...
Article
La rotura por tracción de fibras frágiles ha sido estudiada tradicionalmente por métodos estadísticos, entre los que destaca el Modelo de Weibull. En este trabajo se estudia la aplicabilidad de este modelo y de la Mecánica de la Fractura Elástica Lineal a la rotura por tracción de fibras frágiles, empleándolos para analizar la rotura de fibras de s...
Article
Full-text available
This paper analyzes the tensile properties and brittle fracture of dry semolina fibers, and provides -for the first time- quantitative values for the strength and toughness of this material. Tensile tests on spaghetti with different lengths are performed and the results are correlated with the micrographic observation of fracture surfaces and the d...
Article
Full-text available
Resumen. Este trabajo presenta una primera aproximación a las propiedades mecánicas de las patatas fritas de bolsa. Este estudio se enmarca en el desarrollo de un método para medir de forma objetiva lo crujiente que es dicho material. En primer lugar se comenta el principal ensayo mecánico empleado actualmente en la industria alimentaria con este o...
Article
Full-text available
RESUMEN El síndrome de Marfan es una patología hereditaria del tejido conectivo que afecta, entre otros, al sistema cardiovascular y al musculoesquelético. En los vasos sanguíneos el síndrome de Marfan hace que la pared de la aorta se debilite y se dilate, pudiendo provocar su rotura. Con el fin de mejorar el conocimiento de la respuesta de la pare...
Article
Full-text available
RESUMEN En este artículo se resumen los principales resultados obtenidos por los autores en una colaboración reciente con los hospitales Clínico y Puerta de Hierro de Madrid sobre el comportamiento termomecánico de dos clases de arterias humanas: carótida y aorta. Se han realizado ensayos de presurización interior a diferentes temperaturas, lo cual...
Article
Full-text available
Heart valve prostheses are used to replace native heart valves which that are damaged because of congenital diseases or due to ageing. Biological prostheses made of bovine pericardium are similar to native valves and do not require any anticoagulation treatment, but are less durable than mechanical prostheses and usually fail by tearing. Researches...
Article
Full-text available
La técnica del bypass coronario consiste en evitar una arteria coronaria obstruida utilizando un injerto vascular. Su éxito depende del buen funcionamiento de la zona de unión, o anastomosis, entre la aorta y el injerto, y entre el injerto y la arteria coronaria. Las tensiones generadas en la discontinuidad pueden producir problemas de desgarro o r...

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