SOBRE MÍ
Apasionada de la Biomedicina, cautivada por el mundo de la Microbiología.
Hace ya más de un decenio que me envolví en un "biofilm", una forma de vida que me ha ido resguardando todos estos años de los ataques del mundo exterior.
Mi actividad investigadora se centra principalmente en infecciones asociadas a biofilms. Concretamente, en buscar las estrategias para detectar y prevenir el desarrollo de biofilms microbianos en biomateriales utilizados cómo dispositivos médicos.
LA UNIÓN HACE LA FUERZA
Las bacterias han crecido en biofilms durante millones de años, como parte de una estrategia exitosa para colonizar el planeta y la mayoría de los seres vivos. Nosotros sólo hemos reconocido esta forma de vida de las bacterias en las últimas dos décadas. Pero ha supuesto una estrategia de supervivencia para las bacterias, pues les confiere capacidad adaptativa, de comunicación y resistencia.
Las bacterias al formar biofilms se protegen de bacteriófagos, predadores protozoarios, surfactantes, anticuerpos, fagocitos, antimicrobianos. El biofilm también permite a las bacterias sobrevivir a otros tipos de estrés, tales como las condiciones de calor y frio. En definitiva, les proporciona vivir bajo unas condiciones ambientales más estables. Cuando el ambiente se vuelve poco hospitalario, pueden entrar en un estado de latencia. Esto les proporciona entre otras cosas, una mayor resistencia a la desecación, biocidas, anticuerpos, macrófagos, etc.
Where? Donde lo forman?
¿Quién no ha observado el material mucoso que recubre un jarrón en el que hemos tenido depositadas flores, el material resbaladizo que recubre las piedras de los lechos de los ríos, los cascos de los barcos o la superficie interna de una tubería? Otro ejemplo cotidiano de biofilm lo constituye la placa dental. Los microorganismos no suelen estar libres en el hábitat. Tienden a crear biofilms (biocapas o tapetes microbianos) sobre cualquier superficie.
When? Cuándo lo forman?
Los biofilms se desarrollan cuando los microorganismos se adhieren a una superficie y continúan formando una monocapa de células (o varias capas).
How? Cómo lo forman?
El esquema secuencial de la formación de biofilm, podría dividirse en dos fases diferentes: En la primera etapa hay una fase de adhesión inespecífica y otra de adhesión específica. Es un proceso rápido y reversible, que se debe a la adhesión directa de la bacteria a la superficie del material, o a la matriz de proteínas derivadas del hospedador, que recubren previamente el material. En la segunda etapa se van formando agregados de células revestidas de una matriz polimérica extracelular sintetizada por ellas mismas, que las mantiene juntas y que une esa masa bacteriana a la superficie subyacente. La matriz proporciona protección y un entorno confinado.
What? Qué es un biofilm bacteriano?; Who? Quien lo forma?
“ Es una comunidad estructurada de células bacterianas incluidas en una matriz polimérica autoproducida y adherida a una superficie viva o inerte ” (Costerton et al,1999).
Why? Porqué lo forman?
Las bacterias existen en la naturaleza bajo dos formas o estados: bacterias planctónicas y bacterias en biofilms. El crecimiento en biofilms representa la forma habitual de crecimiento de las bacterias en la naturaleza. Se postula que el 99% de todas las células bacterianas existen en calidad de biofilms y tan solo 1% en estado planctónico (de libre flotación). Sin embargo la mayoría de las infecciones humanas continúa basada en el estudio de las minoritarias bacterias.
Aquí la famosa frase "la unión hace la fuerza" jamás ha estado mejor aplicada.
LATEST RESEARCH
BIODEGRADABLE MATERIALS.
An important problem associated to the use of permanent but also biodegradable implants is the appearance of infections, which bring about increases in hospital costs, morbidity and mortality. The reason is the fast bacterial colonization of the implant surface by opportunistic microorganisms and the subsequent formation of biofilms. These community-like structures make bacteria highly resistant to the host defense and antibacterial agents because the extracellular biofilm matrix reduces the permeability to antimicrobial compounds, thereby persistent and chronic infections are favoured. Such episodes need long courses of antibiotics (which can last for years) and additional surgeries, which often lead to the removal of the infected device. Therefore, one of the key objectives in the development of the new generation of osteosynthesis implants is the search of biodegradable and biocompatible materials that favour the osseointegration with host tissues while inhibiting bacterial adhesion.
In this respect we are researching the potential use of magnesium in biomaterials to prevent bacterial infections.
Antibacterial effect of novel biodegradable and bioresorbable PLDA/Mg composites
Polylactic acid/Mg composites have been recently proposed for biodegradable osteosynthesis devices because, with regards to the neat polymer, they combine an enhanced biocompatibility and bioactivity with better mechanical properties, particularly creep strength. A question still arises about their bacterial behavior. For this purpose, composites of poly-L-D-lactic acid (PLDA) loaded with 1 and 10 wt.% of Mg microparticles were evaluated using Staphylococcus epidermidis, with special emphasis on the study of bacterial adhesion and biofilm formation. During biofilm formation the bacteria viability of the composites decreased up to 65.3% with respect to PLDA. These antibacterial properties do not compromise the cytocompatibility of the material as the composites enhanced the viability of mesenchymal stem cells and their osteogenic commitment. These findings provide an important added value to the biodegradable and biocompatible PLDA/Mg composites for the manufacture of osteosynthesis devices.
Impact of PLA/Mg films degradation on surface physical properties and biofilm survival
New biocompatible and bioabsorbable materials are currently being developed for bone regeneration. These serve as scaffolding for controlled drug release and prevent bacterial infections. Films of polylactic acid (PLA) polymers that are Mg-reinforced have demonstrated they have suitable properties and bioactive behavior for promoting the osseointegration process. However little attention has been paid to studying whether the degradation process can alter the adhesive physical properties of the biodegradable film and whether this can modify the biofilm formation capacity of pathogens. Moreover, considering that the concentration of Mg and other corrosion products may not be constant during the degradation process, the question that arises is whether these changes can have negative consequences in terms of the bacterial colonization of surfaces. Bacteria are able to react differently to the same compound, depending on its concentration in the medium and can even become stronger when threatened.
In this context, physical surface parameters such as hydrophobicity, surface tension and zeta potential of PLA films reinforced with 10% Mg have been determined before and after degradation, as well as the biofilm formation capacity of Staphylococcus epidermidis.
The addition of Mg to the films makes them less hydrophobic and the degradation also reduces the hydrophobicity and increases the negative charge of the surface, especially over long periods of time. Early biofilm formation at 8 h is consistent with the physical properties of the films, where we can observe a reduction in the bacterial biofilm formation. However, after 24 h of incubation, the biofilm formation increases significantly on the PLA/Mg films with respect to PLA control. The explosive release of Mg ions and other corrosion products within the first hours were not enough to prevent a greater biofilm formation after this initial time. Consequently, the Mg addition to the polymer matrix had a bacteriostatic effect but not a bactericidal one. Future works should aim to optimize the design and biofunctionality of these promising bioabsorbable composites for a degradation period suitable for the intended application.
Development of a Ta/TaN/TaNx(Ag)y/TaN nanocomposite coating system and bio-response study for biomedical applications.
TaN(Ag) composited coatings are being investigated to improve biocompatibility of different biomedical devices due to the mechanical and chemical stability of TaN and bactericidal effect of silver nanoparticles. However, controlling the size, density, shape and especially the release of silver ions (Ag) into the surrounding medium becomes a challenge, since elevated levels of Ag could be cytotoxic. The aim of this work is to design and develop a new Ta/TaN/TaNx(Ag)y/TaN coating system, deposited by unbalanced DC magnetron sputtering technique, presenting an adequate balance between biocompatibility and bactericidal effect for potential applications in biomedical field. For this purpose, four different coating systems were deposited on 316 L stainless steel and silicon (100) samples applying a bias voltage of −30, −60, −90 and −120 V during the deposition of the top layer of TaN to vary its density. This manufacturing strategy allowed controlling the diffusion of silver nanoparticles to the coating surface and the release kinetics of silver ions in simulated body fluid (SBF). Biologic characterization has been performed with MC3T3-E1 pre-osteoblastic cells in terms of cell adhesion and long-term differentiation. Additionally, the adhesion and biofilm formation of the bacteria Streptococcus sanguinis strain in the deposited coating systems of Ta/TaN/TaNx(Ag)y/TaN were analyzed. The results indicated an improvement of cell adhesion and differentiation of the composited coating deposited with a bias of −30 V compared to other coatings. Concordantly, this coating showed the lowest bacterial adhesion and biofilm formation, representing an attractive and suitable composited material for biomedical applications.
