A novel antibacterial sol-gel coating for prosthetic devices

Mención Internacional en el título de doctorThis Doctoral Thesis deals with the design and development of novel coatings manufactured by sol-gel technology to prevent and treat bacterial infections associated to joint prostheses. The risk of bacterial infections during the implantation of prostheses causes devastating repercussions for the patients. These bacterial infections are commonly treated systemically with the administration of antimicrobials that are somehow inefficient to locally counteract the focus of infection. Instead, local therapies are being studied because they can reach the biomaterial-tissue interface. This research project is addressed to locally overcome the risk of contracting infections by using a biodegrdable sol-gel coating as carrier of an antimicrobial. The multifunctional coating consists of two organopolysiloxanes, as the precursors of the sol-gel network, with the ability to degrade in 24 hours in contact with a physiological solution. The degradation of the coating will allow the release of the pre-loaded antimicrobial. The coating has been bio-functionalized first with an organophosphite in order to enhance the proliferation of cells during the process of implantation. Then, the selected coating has been loaded with an antibiotic of broad spectrum activity against the pathogens that causes these infections. The degradation kinetics of the coatings has been evaluated by means of electrochemical techniques using the averaging Electrochemical Impedance Spectroscopy (EIS) and the spatially highly resolved Scanning Electrochemical Microscopy (SECM). The study revealed that the concentration of antibiotic exerted a strong influence in the degrading process, being the coating with the highest amount of antibiotic the coating that has a faster degrading process. The non-cytotoxicity and the enhancement of the cellular proliferation have been verified with MC3T3-E1 cells. The inhibition of bacterial adhesion (prevention) and mature biofilm growth (treatment) of the main species that causes infection (S. aureus, S. epidermidis and E. coli) have also been confirmed. The release of the antibiotic has been tracked by absorbance spectroscopy and it revealed that the degradation of the coating is non-proportional to the release of antibiotic. Despite the low release of antibiotic to the medium, the quantity has been demonstrated to be enough to inhibit the growth of mature biofilm. Indeed, this research study showed that the degradation kinetics of sol-gel coatings loaded with an antibiotic (moxifloxacin) can be monitored with different electrochemical techniques. Besides, thanks to the in vitro microbiological study and the monitorization of the release of the antibiotic, it has been verified that the quantity of antibiotic in the medium is enough to accomplish the bacterial features of the medical device. Moreover, this study confirmed the potential of the sol-gel technology to fit the release of an antimicrobial to the requirements of the prosthetic devices by modifying the parameters of the sol-gel synthesis.Esta Tesis Doctoral se centra en el diseño y desarrollo de nuevos recubrimientos obtenidos por tecnología sol-gel para prevenir y tratar infecciones bacterianas asociadas a prótesis articulares. La contracción de infecciones bacterianas durante la implantación de prótesis provoca repercusiones devastadoras a los pacientes y son generalmente tratadas mediante la administración sistémica de antimicrobianos. Este tipo de terapia es mejorable ya que no llega a alcanzar su función en el foco de la infección. Por ello, las terapias locales están adquiriendo mayor relevancia ya que alcanzan fácilmente la interfaz biomaterial-tejido. Este proyecto de investigación está orientado a combatir localmente el riesgo de infección mediante el uso de un recubrimiento de tipo sol-gel biodegradable como portador y liberador de un agente antimicrobiano. El recubrimiento tiene carácter multifuncional y está diseñado a partir de dos organopolisiloxanos como precursores de la red sol-gel, la cual tiene la capacidad de degradarse durante las primeras 24 horas en contacto con una solución fisiológica. El recubrimiento se ha biofuncionalizado con un organofosfito para mejorar la proliferación celular durante el proceso de implantación protésica. La siguiente etapa en el diseño de la formulación fue la introducción del antibiótico durante la síntesis. El antibiótico moxifloxacino fue elegido por su amplio espectro de actividad contra los patógenos que causan las infecciones en estudio. La degradación del recubrimiento permite la liberación del antibiótico previamente incorporado a la red. La degradación cinética de los recubrimientos se ha evaluado por medio de técnicas electroquímicas usando Espectroscopia de Impedancia Electroquímica (EIS, Electrochemical Impedance Spectroscopy) y Microscopía Electroquímica de Barrido (SECM, Scanning Electrochemical Microscopy). El estudio reveló que la concentración de antibiótico influye en el proceso de degradación siendo el recubrimiento con mayor cantidad de éste el que presenta un proceso de degradación más rápido. La no citotoxicidad y la proliferación celular fueron verificadas con células MC3T3-E1. La inhibición de la adhesión bacteriana (prevención) y el crecimiento de la biopelícula madura (tratamiento) de las principales especies que causan estas infecciones (S. aureus, S. epidermidis y E. coli) también fueron confirmadas. La liberación del antibiótico se ha estudiado con espectroscopia de absorbancia UV-Vis., observándose que, a pesar de la poca cantidad de antibiótico liberada al medio, la cantidad del mismo es suficiente para inhibir el crecimiento de la biopelícula madura. Con el presente trabajo de investigación se puede concluir que la degradación de los recubrimientos diseñados de tipo sol-gel cargados con moxifloxacino puede monitorizarse con técnicas electroquímicas. Además, gracias al estudio in vitro microbiológico y estudios de absorbancia, se ha comprobado que la liberación del antimicrobiano es adecuada ya que cumple su función bactericida. Este estudio confirma la Idoneidad de la tecnología sol-gel para ajustar la liberación de un antimicrobiano a las necesidades temporales requerido por un sistema dispositivo protésico/medio agresivo, mediante la modulación de la síntesis del recubrimiento.Programa Oficial de Doctorado en Ciencia e Ingeniería de MaterialesPresidente: Sandra Carolina Cifuentes Cuéllar.- Secretario: María Cristina García Alonso.- Vocal: Rafael Leiva Garcí

The effect of the organosilane content on the barrier features of sol-gel anticorrosive coatings applied on carbon steel

The main objective of this work was to determinate the influence of the molar ratio of two compounds on the structure of the molecular net synthesized by sol-gel technology for the protection corrosion coating on carbon steel. Three different molar ratio were use to prepared the organic–inorganic hybrid materials by hydrolysis and condensation of (3-glycidyloxypropyl)trimethoxysilane (GPTMS) and tetraethylorthosilane (TEOS) in an ethanol/water solution. The behavior of the three different syntheses was evaluated by chemical, physical, and electrochemical methods. The evolution of the synthesis was determinate by FT-IR and viscosity until the optimal moment prior to apply the sol to the metallic substrate. Chemical cross-linking of xerogel was determined by solid state of 29Si-NMR and the behavior on thermal stability is given by TGA analysis. Samples of carbon steel were coated by the synthesis and the coatings were characterized using scanning electrochemical microscopy (SEM) finding considerably differences between the three coatings. Potentiodynamic polarization and impedance measurements were carried out to study the effect of the corrosion resistance of the synthesis in 10 mM NaCl solution.The authors acknowledge the financial support from the Regional Government of Madrid through the program MULTIMAT-CHALLENGE (S2013/MIT-2862). The authors acknowledge the financial support from the European Union and Government of Spain through the program RETOS COLABORACIÓN. RECORD (RTC-2015-3513-S) [i.e. RTC-2015-3513-5

A biodegradable antifungal-loaded sol-gel coating for the prevention and local treatment of yeast prosthetic-joint infections

Fungal prosthetic-joint infections are rare but devastating complications following arthroplasty. These infections are highly recurrent and expose the patient to the development of candidemia, which has high mortality rates. Patients with this condition are often immunocompromised and present several comorbidities, and thus pose a challenge for diagnosis and treatment. The most frequently isolated organisms in these infections are Candida albicans and Candida parapsilosis, pathogens that initiate the infection by developing a biofilm on the implant surface. In this study, a novel hybrid organo-inorganic sol-gel coating was developed from a mixture of organopolysiloxanes and organophosphite, to which different concentrations of fluconazole or anidulafungin were added. Then, the capacity of these coatings to prevent biofilm formation and treat mature biofilms produced by reference and clinical strains of C. albicans and C. Parapsilosis was evaluated. Anidulafungin-loaded sol-gel coatings were more effective in preventing C. albicans biofilm formation, while fluconazole-loaded sol-gel prevented C. parapsilosis biofilm formation more effectively. Treatment with unloaded sol-gel was sufficient to reduce C. albicans biofilms, and the sol-gels loaded with fluconazole or anidulafungin slightly enhanced this effect. In contrast, unloaded coatings stimulated C. parapsilosis biofilm formation, and loading with fluconazole reduced these biofilms by up to 99%. In conclusion, these coatings represent a novel therapeutic approach with potential clinical use to prevent and treat fungal prosthetic-joint infections.This research was funded by MUTUA MADRILEÑA FOUNDATION, grant number 04078/001 and REGIONAL GOVERNMENT OF MADRID through the ADDIMAT PROGRAM, grant number S2018/NMT-441

A new antibiotic-loaded sol-gel can prevent bacterial prosthetic joint infection: From in vitro studies to an in vivo model

The aim of this study was to evaluate the effect of a moxifloxacin-loaded organicinorganic sol-gel with different antibiotic concentration in the in vitro biofilm development and treatment against Staphylococcus aureus, S. epidermidis, and Escherichia coli, cytotoxicity and cell proliferation of MC3T3-E1 osteoblasts; and its efficacy in preventing the prosthetic joint infection (PJI) caused by clinical strains of S. aureus and E. coli using an in vivo murine model. Three bacterial strains, S. epidermidis ATCC 35984, S. aureus 15981, and, E. coli ATCC 25922, were used for microbiological studies. Biofilm formation was induced using tryptic-soy supplemented with glucose for 24 h, and then, adhered and planktonic bacteria were estimated using drop plate method and absorbance, respectively. A 24-h-mature biofilm of each species growth in a 96- well plate was treated for 24 h using a MBECTM biofilm Incubator lid with pegs coated with the different types of sol-gel, after incubation, biofilm viability was estimated using alamrBlue. MC3T3-E1 cellular cytotoxicity and proliferation were evaluated using CytoTox 96 Non-Radioactive Cytotoxicity Assay and alamarBlue, respectively. The microbiological studies showed that sol-gel coatings inhibited the biofilm development and treated to a mature biofilm of three evaluated bacterial species. The cell studies showed that the sol-gel both with and without moxifloxacin were non-cytotoxic and that cell proliferation was inversely proportional to the antibiotic concentration containing by sol-gel. In the in vivo study, mice weight increased over time, except in the E. coliinfected group without coating. The most frequent symptoms associated with infection were limping and piloerection; these symptoms were more frequent in infected groups with non-coated implants than infected groups with coated implants. The response of moxifloxacin-loaded sol-gel to infection was either total or completely absent. No differences in bone mineral density were observed between groups with coated and non-coated implants and macrophage presence lightly increased in the bone grown directly in contact with the antibiotic-loaded sol-gel. In conclusion, moxifloxacinloaded sol-gel coating is capable of preventing PJI caused by both Gram-positive and Gram-negative speciesThe authors acknowledge the financial support from the Regional Government of Madrid through the program MULTIMAT-CHALLENGE (S2013/MIT-2862), and from the Mutua Madrileña Foundation (04078/001). JA-C was funded by an FPI grant from the Spanish Ministry of Economics and Competitiveness (BES-2014-069007). AM was funded by grants from Instituto de Salud Carlos III through the “Miguel Servet” program (CP15/00053). DR was funded by a grant from the Fundación Conchita Rábag

A new antibiotic-loaded sol-gel can prevent bacterial intravenous catheter-related infections

The aim of this study was to evaluate the effectiveness of a moxifloxacin-loaded organic-inorganic sol-gel (A50) by locally preventing the catheter-related bloodstream infection (CRBSI) provoked by Staphylococcus epidermidis (S. epidermidis) and the effect resulting from its hydrolytic degradation on coagulation by using a rabbit in-vivo model. A50 coating can completely inhibit growth and would locally prevent CRBSI provoked by S. epidermidis. None of the coagulation blood parameters showed a significant difference constant over time between the control catheter group and the A50-coated catheter group, despite the visible silica release resulting from physiological A50 sol-gel degradation detected in serum at least during the first week. At pathological level, foreign body reaction was present in both of types of catheter, and it was characterized by the presence of macrophages and foreign body giant cell. However, this reaction was different in each group: the A50-coated catheter group showed a higher inflammation with histiocytes, which were forming granuloma-like aggregates with an amorphous crystalline material inside, accompanied by other inflammatory cells such as plasma cells, lymphocytes and mast cells. In conclusion, A50 coating a venous catheter showed excellent bactericidal anti-biofilm response since it completely inhibited S. epidermidis biofilm development and, far from showing procoagulant effects, showed slightly anticoagulant effects.This research received financial support from the Mutua Madrileña Foundation (04078/001). J.J.A.-C. was funded by an FPI grant from the Spanish Ministry of Economics and Competitiveness (BES-2014-069007)

Scanning Electrochemical Microscopy characterization of sol-gel coatings applied on AA2024-T3 substrate

Scanning electrochemical microscopy was employed to characterize the local surface activity of an AA2024-T3 coated with sol-gel. Corrosion inhibitors were added to the sol-gel either as soluble chemical species, namely 1,2,3-benzotriazole, Na-(diethyl(dithiocarbamate)), and piperazine, or using Ce(III)-montmorillonite containers. The Scanning electrochemical microscopy was operated in the feedback mode by using ferrocene-methanol as redox mediator. This experimental procedure allowed evaluation of the coating behaviour in damaged and non-damaged areas from the analysis of Z-approach curves and 2D maps. The results evidence differences in the local electrochemical activity of the modified coatings that correlate well with averaging electrochemical measurements using electrochemical impedance spectroscop

A feasibility study for implementation 'Health Arcade': a study protocol for prototype of multidomain intervention based on gamification technologies in acutely hospitalized older patients

The aim of this article is to present the research protocol for a study that will evaluate the feasibility of implementation of Health Arcade prototype multidomain intervention based on physical and cognitive training using gamification technologies at improving care for older people hospitalized with an acute illness. A total of 40 older people will be recruited in a tertiary public hospital at Pamplona, Spain. The intervention duration will be four to nine consecutive days. Additionally, the patients will receive encouragement for maintaining active during hospital stay and for reducing sedentary time. Primary implementation-related outcomes will be the adherence to treatment (i.e., number of games and days completed during the intervention period), reaction or response time, and number of success and failures in each game per day. Secondary implementation-related outcomes will be self-perceived grade of difficulty, satisfaction, enjoyment per game and session, and self-perceived difficulties in handling the prototype hardware. Other health-related outcomes will also be assessed such as functional capacity in activities of daily living, mood status, quality of life, handgrip strength, physical activity levels, and mobility. The current study will provide additional evidence to support the implementation of multidomain interventions designed to target older persons with an acute illness based on friendly technology. The proposed intervention will increase accessibility of in-clinical geriatrics services, improve function, promote recovery of the health, and reduce economic costs.This study has been funded by a Gobierno de Navarra project grant (Resolucion 81E/2019, de 19 de junio). Expediente: 0011-1365-2019-000139; Sistema piloto de entrenamiento fisico multicomponente basado en tecnologias de gamificacion para la prevencion del deterioro funcional en ancianos hospitalizados 'HEALTH ARCADE'. N.M.-V. received funding from 'la Caixa' Foundation (ID 100010434), under agreement LCF/PR/PR15/51100006. R.R.-V. is funded in part by a Postdoctotal fellowship grant ID 420/2019 of the Universidad Publica de Navarra, Spain. A.G.-H. is a Miguel Servet Fellow (Instituto de Salud Carlos III -FSE, CP18/0150)

Introducción

La memoria es ese espacio de hilos delgados y gruesos por el que es complejo transitar. Los días, los meses y los años la convierten en un terreno impredecible de zonas fangosas; pero sobre ella, venciendo obstáculos, siempre hay que volver.De eso trata este libro, de volver sobre el pasado de 12 colombianos que hoy superan los 80 años, y que fueron testigos de la época de La Violencia, que se establece desde 1930 y que se complejiza el 9 de abril de 1948, con el asesinato de líder político Jorge Eliecer Gaitán

Spatiotemporal Characteristics of the Largest HIV-1 CRF02_AG Outbreak in Spain: Evidence for Onward Transmissions

Background and Aim: The circulating recombinant form 02_AG (CRF02_AG) is the predominant clade among the human immunodeficiency virus type-1 (HIV-1) non-Bs with a prevalence of 5.97% (95% Confidence Interval-CI: 5.41–6.57%) across Spain. Our aim was to estimate the levels of regional clustering for CRF02_AG and the spatiotemporal characteristics of the largest CRF02_AG subepidemic in Spain.Methods: We studied 396 CRF02_AG sequences obtained from HIV-1 diagnosed patients during 2000–2014 from 10 autonomous communities of Spain. Phylogenetic analysis was performed on the 391 CRF02_AG sequences along with all globally sampled CRF02_AG sequences (N = 3,302) as references. Phylodynamic and phylogeographic analysis was performed to the largest CRF02_AG monophyletic cluster by a Bayesian method in BEAST v1.8.0 and by reconstructing ancestral states using the criterion of parsimony in Mesquite v3.4, respectively.Results: The HIV-1 CRF02_AG prevalence differed across Spanish autonomous communities we sampled from (p < 0.001). Phylogenetic analysis revealed that 52.7% of the CRF02_AG sequences formed 56 monophyletic clusters, with a range of 2–79 sequences. The CRF02_AG regional dispersal differed across Spain (p = 0.003), as suggested by monophyletic clustering. For the largest monophyletic cluster (subepidemic) (N = 79), 49.4% of the clustered sequences originated from Madrid, while most sequences (51.9%) had been obtained from men having sex with men (MSM). Molecular clock analysis suggested that the origin (tMRCA) of the CRF02_AG subepidemic was in 2002 (median estimate; 95% Highest Posterior Density-HPD interval: 1999–2004). Additionally, we found significant clustering within the CRF02_AG subepidemic according to the ethnic origin.Conclusion: CRF02_AG has been introduced as a result of multiple introductions in Spain, following regional dispersal in several cases. We showed that CRF02_AG transmissions were mostly due to regional dispersal in Spain. The hot-spot for the largest CRF02_AG regional subepidemic in Spain was in Madrid associated with MSM transmission risk group. The existence of subepidemics suggest that several spillovers occurred from Madrid to other areas. CRF02_AG sequences from Hispanics were clustered in a separate subclade suggesting no linkage between the local and Hispanic subepidemics

Electrochemical study of the synergic effect of phosphorus and cerium additions on a sol-gel coating for Titanium manufactured by powder metallurgy

The goal of this work was to combine the physical barrier properties provided by the sol-gel network with an active-chemistry protection against corrosion provided by corrosion inhibitors and cross-linking agents. Sol-gel coatings, organic&#-inorganic hybrid materials were prepared by hydrolysis and condensation of (3-glycidyloxypropyl)trimethoxysilane (GPTMS) and tetraethylorthosilane (TEOS) in an ethanol/water solution. This coatings were satisfactorily modified by adding an inhibitor of the corrosion, namely hexahydrate cerium nitrate, and a cross-linking agent, namely tris(trimethylsilyl)phosphite (TMSP). The synergetic effect of these two compounds was evaluated by means of electrochemical characterization. The evolution rate of the hydrolysis-polycondensation reaction was monitored by Fourier-transform infrared spectroscopy and viscosity. Once the hydrolysis-polycondensation rate was reached, sols were deposited on titanium fabricated by powder metallurgy. The morphological characteristics and elemental distribution of the coatings were studied using scanning electrochemical microscopy (SEM). The solid-state of Si-NMR spectroscopy and thermogravimetric analysis (TGA) was employed in order to identify the cross-linking state of the coating by ensuring the creation of enough siloxane bonds. Impedance measurements were carried out to study the effect of cerium and TMSP on the corrosion resistance. It was observed that the coating with additions of cerium presented stable and good barrier features against 5&;8239#mM NaCl solution. The synergy between the cerium inhibitor and the TMSP cross-linking agent was found not to exert a positive effect because the electrochemical behaviour was dominated by the phosphorus compound over the cerium.The authors acknowledge the financial support from the Regional Government of Madrid through the program MULTIMAT-CHALLENGE (S2013/MIT-2862). The authors acknowledge the financial support from the European Union and Government of Spain through the program RETOSCOLABORACIÓN. RECORD (RTC-2015-3513-S