Karem Noris-Suárez

Caracterización mediante FTIR y DSC de la interacción colágeno — hidroxiapatita

In the present work, we studied the effect of the mineral content (hydroxyapatite), on the thermal stability of the bone collagen matrix. The demineralization process was followed measuring the percentage of remaining mass and characterized by Fourier Transform Infra Red Spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC), using a Calcium chelant agent (EDTA). A 52 % loss of the initial weight was observed after 72 hours of treatment, associated with a decrease of the mineral content, indicated by changes in the intensity of the peaks correspondent to PO4-3 vibrations. The bone collagen’s denaturalization and degradation temperatures was followed by DSC, showing an endotherm in 166° C for the untreated bone and in 113°C for the 72 hours treated bone, correspondent both to the bone collagen denaturalization temperature. The thermogram for the 12 hours demineralized exhibited a small endotherm in 250°C, corresponding to slight degradation, for the 72 hours treated bone the endotherm decreased to 230° C, correspondent to the bone collagen degradation. The above results lead us to conclude that the bone collagen triple helix losses its thermal stability when the interactions with the surrounding hydroxyapatite are eliminated.

Electrochemical Influence of Collagen Piezoelectric Effect in Bone Healing

Bone healing and growth are controlled by the rate of deposition of hidroxiapatite (HA). This process have been so far accredited to the work of osteoblasts, which are attracted by the electrical dipoles produced either by piezoelectricity, due to deformation of the bone, specially the collagen in it, or due to outside electrical stimuli. The present work shows that even without osteoblasts present, the piezoelectric dipoles produced by deformed collagen, can produce the precipitation of HA by electrochemical means, without catalyzer as in biomimetic deposition. These findings could clarify the contribution of osteoblasts in bone growth as compared to the electrochemical action by itself. Further studies ascertaining the osteoblastic activity due to the electric field are being advanced.

A new morphological cell parameter based on optical phase for the evaluation of cell populations

In this work, we introduce an opto-geometric parameter for the morphologic characterization of cell populations during their early adhesion process. Using measurements for a cell population of the maximal optical phase for each cell and its substrate-contact-surface, we show, experimentally, that a relationship exists between these variables. This connection is primarily associated with morphological cell characteristics. It is also shown that using the relationship obtained above, we can derive a morphological parameter, which, for the cell populations studied, results in a monodisperse Gaussiansize distribution, which would allow for the use of regular statistical variables. This result is in total contrast with the polydisperse distribution obtained if only the contact surface area between cell and substrate is used. In addition, optical phase measurements where accomplished by phase shifted interferometry using a Mirau-type interference microscope. The cellular system studied consisted of Osteoblast-like cells, plated on 316VM medical-grade stainless steel polished surfaces. These cell populations were studied within the same culture conditions of cell type, plating time and substrate roughness conditions. The existence of a relationship between maximal optical phase and substrate contact area agrees entirely with the accepted spreading model for cell adhesion; in particular, considering the close link between the optical phase time change and cell thickness reduction.

An unusual casein kinase 1 from Trypanosoma cruzi epimastigotes

Abstract Background: CK1 enzymes are serine/threonine protein kinases that regulate numerous cellular processes. Although seven putative CK1 ortholog genes have been identified in the genome of Trypanosoma

Quantitative phase microscopy for the study of bone cells on multiple roughness surfaces

We present a phase shifting interferometry system for the study of the early adhesion process for osteoblast-like cells, through an interference microscope. Optical phase maps from the cells are obtained experimentally as a function of cell adhesion time. The process is carried out on surfaces of metallic materials relevant to the development of bone implants. The surfaces were subjected to various levels of mechanical polishing and their roughness was measured using the same experimental technique mentioned before. Morphological changes of the cell can be measured over their optical phase maps while the cell adhesion process is accomplished. The experimental technique shows a suitable feature as to the observed time scale, and also shows a high stockiness and precision for the determination of the optical phase.

El grado de glicosilación del colágeno óseo regula la adhesión y la capacidad de biomineralizar de las células óseas

In the bone tissue, collagen is the most abundant protein, conforming 90% of the organic matrix of this mineralized structure. Different works indicate that in postmenopausal osteoporosis, the early degradation of the bone tissue seems to be due to the presence of bone collagen in a condition of overglycosylation, especially in the trabecular bone. To understand the role of the glycosylation of the collagen molecule and how it can regulate functions of the bone cells, such as cellular adhesion and biomineralization, is the main objective of the present work. 8 rats were ovariectomized and another 8 were sham-operated (control group). After 45 days the rats were sacrificed, femurs were extracted and the bones were decalcified in order to obtain the collagen matrix mineral free. Primary cultures of bone cells were obtained from calvaria of neonatal rats. The adhesion and differentiation (alkaline phosphatase activity and biomineralization) of these cells were evaluated on the collagen bone matrix obtained of the ovariectomized and control rats. The results of this work show a greater adhesion of the osteoblastic cells on the bone collagen for the control group in comparison with the adhesion found for the ovariectomized group, in the first two hours. Additionally, cell FA activities and mineralization on material differ between control and ovariectomized animals bone collagen samples. In conclusion, in the present work we present evidence that suggest that bone cells can recognize differences in the degree of glycosylation of the collagen matrix in ovariectomized animals in comparison with the control group, and the cellular response is different as a consequence of these variations of the extracellular material.

Estudio de Mezclas de Polietileno de Alta Densidad (PEAD) con colágeno/acetato de sodio e Hidroxiapatita (HA)

Blends and/or composites of HDPE, type I collagen gel extracted from rat tails and dried in presence of sodium acetate, poly(ethylene -co- acrylic acid) (a compatibilizg agent) and hydroxiapatite were studied. Differential Scanning Calorimetry (DSC) analyses demonstrated that the collagen gel was able to tolerate the processing conditions of HDPE since it kept its characteristic denaturalization temperature. Transmision Electronic Microscopy (TEM) showed that the fibrillar structure of collagen was kept and it finds itself dispersed on the HDPE matrix. Collagen supplies an important reinforcement to HDPE by increasing 2,7 times the HDPE Young’s modulus values. The compatibilizing agent did not show any important contribution to the Young’s modulus of the HDPE/collagen/copolymer blend in comparison with the blend where no compatibilizing was used. On the other hand, the HDPE/HA blends showed a Young’s modulus about two times that of pure HDPE, due to the HA crystals which confer stiffness to the whole system.