Papers by Author: Josep A. Planell

Abstract: Bone problems affect millions of people across the world. In fact, musculoskeletal conditions such as joint pathologies, fractures related to osteoporosis, back pain, serious injuries and different sorts of bone diseases and disabilities are among the most common causes for hundreds of millions of people worldwide suffering acute and severe long-term pain and becoming physically handicapped. It has been reported that over 100 million Europeans are affected by different bone related problems and suffer chronic musculoskeletal pain, while in the US musculoskeletal problems affect over 40 million people aged 45 years and older. It is expected that the percentage of population affected by musculoskeletal conditions will double by the year 2020. Although morbidity is low, they have a major effect on disability, medical costs and patient quality of life [1,2]. Thus, bone defect treatments represent a significant medical and socioeconomic challenge.

Abstract: In this work we examine the effect of the ionic exchange in cell behaviour of two apatite substrates with the same chemical composition but different microstructures (Coarse and Fine) by culturing cells with their extracts. A higher decrease in Ca and a higher increase in P concentrations were detected in the culture medium extracts from the finer apatite substrate in accordance with its higher specific surface area. A decrease in cell proliferation was observed when cells were cultured with the Fine extract in comparison with cells in contact with the Coarse extract or the control group. Although the higher ionic exchange, this could not explain the drastic decrease in cell proliferation observed on Fine apatite substrates, so a strong interaction with the underlying microstructure that modulates cell behaviour is also present.

Abstract: The design and processing of 3D macroporous bioactive scaffolds is one of the milestones for the progress of bone tissue engineering and bone regeneration. Calcium phosphate based ceramics are among the most suitable materials, due to their similarity to the bone mineral. Specifically, beta-tricalcium phosphate (β-TCP) is known to be a resorbable and bioactive material, with well established applications as bone regeneration material. The aim of this work is to explore a new route to obtain β-TCP macroporous scaffolds starting from calcium phosphate cements. To this end foamed calcium phosphate cement, composed of alpha tricalcium phosphate as starting powder was used as initial material. The set foamed structures, made of calcium deficient hydroxyapatite (CDHA) were sintered to obtain the final β-TCP macroporous architecture. The interconnected macroporosity was maintained, whereas the porosity in the nanometric range was strongly reduced by the sintering process. The sintering produced also an increase in the mechanical properties of the scaffold.

Abstract: As a ceramic, silicon nitride (Si3N4) has been suggested as a biocompatible material in contact with bone. In another configuration, as a low pressure chemically vapor deposited (LPCVD) thin film, Si3N4 can also be used as the sensitive material in certain biosensor applications. With the latter in mind, the biocompatibility of such films was investigated after them being modified with silane based self-assembled monolayers (SAMs) bearing functional end groups of methyl (CH3), primary amine (NH2), and carboxyl (COOH) respectively. The SAM surface modifications provided a wide range of physiochemical properties including hydrophobic (CH3), hydrophilic (bare Si3N4), positively (NH2) and negatively charged (COOH). Specifically the cell adhesion and proliferation, as well as the levels of alkaline phosphatase activity and osteocalcin, have been evaluated using the human osteoblast-like MG-63 cell line. It was observed that attachment and spreading was pronounced on NH2 while suppressed on CH3. With time the cells grew to confluence on all chemistries, and the levels of osteocalcin normalized to total protein content varied as CH3 > Si3N4 > COOH > NH2, but without significant differences. The highest spontaneous alkaline phosphatase activity was observed from cells grown on Si3N4 substrata.

Abstract: Resorbable calcium phosphate glasses offer interesting solutions in the biomedical field, as bone cavity fillers, drug delivery systems, biodegradable reinforcing phase in the case of composites for bone fixation devices and tissue engineering scaffolds. In this work, two different glass formulations in the systems 44.5CaO-44.5P2O5-(11-X)Na2O-XTiO2 (X=0or 5) have been elaborated. It is known that the incorporation or TiO2 into the vitreous system reduces considerably the solubility of the glasses. To study the material solubility effect on the in vivo response, glass particles of the two formulations were implanted in rabbits. Results showed that both glasses elicited a similar biological response and good biocompatibility. The percentage of new bone formation in the glasses was comparable to that obtained for the autologous bone (control) after 12 weeks of implantation. The materials showed to have an osteoconductive potential. Finally, this study showed that in spite of the solubility difference of the studied glasses, there were no significant differences in the in vivo response.

Abstract: In this work an injectable and self setting calcium phosphate/albumen foam is developed. The effect of both the amount of albumen and the particle size of the starting a-tricalcium phosphate (a-TCP) powder on the injectability of the cement paste is studied. X-ray diffraction (XRD) and infrared (IR) analysis of the samples reveal that the hydrolysis of a-TCP to calcium deficient hydroxyapatite (CDHA) is not affected by the addition of albumen. A foamed structure formed by spherical pores with diameters between 100 and 500 µm is observed by SEM. This porous structure is maintained after injection of the paste, although some deformation of the pores is produced due to the extrusion process. The injectability of the cements is increased by the presence of albumen as compared with cements prepared in the same conditions but without foaming agent.

Abstract: Calcium phosphate cements (CPC) are being applied as bone regeneration materials. New methods are being developed to create macroporosity, in order enhance the angiogenesis, bone colonization and biodegradation of the material. In this study the effect of the incorporation of albumen as foaming agent in an a-tricalcium phosphate (a-TCP) cement, in terms of the surface roughness and in vitro cell response, was studied. The addition of albumen to CPC cements increased the surface roughness of the cements. Cell cultures, using MG63 osteoblasts, were performed and showed that cell attachment was not affected by the presence of albumen. However, cell proliferation was significantly increased in the albumen-containing cements.