Force spectroscopy-based simultaneous topographical and mechanical characterization to study polymer-to-polymer interactions in coated alginate microspheres

Cell-laden hydrogel microspheres have shown encouraging outcomes in the fields of drug delivery, tissue engineering or regenerative medicine. Beyond the classical single coating with polycations, many other different coating designs have been reported with the aim of improving mechanical properties and in vivo performance of the microspheres. Among the most common strategies are the inclusion of additional polycation coatings and the covalent bonding of the semi-permeable membranes with biocompatible crosslinkers such as genipin. However, it remains challenging to characterize the effects of the interactions between the polycations and the hydrogel microspheres over time in vitro. Here we use a force spectroscopy-based simultaneous topographical and mechanical characterization to study polymer-to-polymer interactions in alginate microspheres with different coating designs, maintaining the hydrogels in liquid. In addition to classical topography parameters, we explored, for the first time, the evolution of peak/valley features along the z axis via thresholding analysis and the cross-correlation between topography and stiffness profiles with resolution down to tens of nanometers. Thus, we demonstrated the importance of genipin crosslinking to avoid membrane detachment in alginate microspheres with double polycation coatings. Overall, this methodology could improve hydrogel design rationale and expedite in vitro characterization, therefore facilitating clinical translation of hydrogel-based technologies

In vivo bactericidal efficacy of the Ti6Al4V surface after ultraviolet C treatment

FONDO Las infecciones asociadas con biomateriales son una de las complicaciones más importantes en la cirugía ortopédica. El objetivo principal de este estudio fue demostrar el efecto bactericida in vivo de la radiación ultravioleta (UV) en las superficies de Ti6Al4V. MATERIALES Y MÉTODO Se desarrolló un modelo experimental de infecciones relacionadas con dispositivos mediante la inoculación directa de Staphylococcus aureus en el canal de ambos fémures de 34 ratas. Un pin Ti6Al4V irradiado con radiación UV se ajustó a presión en el canal por inserción retrógrada en un fémur y el pin de control se insertó en el fémur contralateral. Para evaluar la eficacia de la radiación UV, se compararon los recuentos medios de colonias después de la inoculación en los sujetos experimentales y el grupo de control en diferentes momentos de sacrificio y en diferentes dosis de inóculo. RESULTADOS A las 72 h, los recuentos medios de colonias después de la inoculación en fémures experimentales fueron significativamente más bajos que los del grupo de control, con un porcentaje de reducción del 76% (p = 0,041). Una diferencia similar entre los pernos de control y experimentales se observó a las 24 h con una dosis de inóculo <104 unidades formadoras de colonias (UFC), para la cual el porcentaje de reducción fue de 70.48% (p = 0.017). CONCLUSIÓN La superficie irradiada de Ti6Al4V puede reducir la colonización bacteriana temprana de los pines de Ti6AlV ubicados en el canal medular y en el fémur circundante. Las reducciones dependen de los inóculos iniciales utilizados para causar la infección en los animales y los mayores efectos se detectan para los inóculos <104 UFC.BACKGROUND Biomaterial-associated infections are one of the most important complications in orthopedic surgery. The main goal of this study was to demonstrate the in vivo bactericidal effect of ultraviolet (UV) irradiation on Ti6Al4V surfaces. MATERIALS AND METHODS An experimental model of device-related infections was developed by direct inoculation of Staphylococcus aureus into the canal of both femurs of 34 rats. A UV-irradiated Ti6Al4V pin was press-fit into the canal by retrograde insertion in one femur and the control pin was inserted into the contralateral femur. To assess the efficacy of UV radiation, the mean colony counts after inoculation in the experimental subjects and the control group were compared at different times of sacrifice and at different inoculum doses. RESULTS At 72 h, the mean colony counts after inoculation in experimental femurs were significantly lower than those of the control group, with a reduction percentage of 76 % (p = 0.041). A similar difference between control and experimental pins was observed at 24 h using an inoculum dose <104 colony-forming units (CFU), for which the reduction percentage was 70.48 % (p = 0.017). CONCLUSION The irradiated surface of Ti6Al4V is able to reduce early bacterial colonization of Ti6AlV pins located in the medullar channel and in the surrounding femur. The reductions depend on the initial inoculums used to cause infection in the animals and the greatest effects are detected for inoculums <104 CFU.• Ministerio de Ciencia e Innovación. Beca MAT2009-14695-CO4- C01 • Junta de Extremadura. Beca GR10149 • Junta de Extremadura. Beca predoctoral para María Delgado RastrollopeerReviewe

Connected Insulin Pens and Caps : An Expert's Recommendation from the Area of Diabetes of the Spanish Endocrinology and Nutrition Society (SEEN)

Undoubtedly, technological advances have revolutionised diabetes management in recent years. The development of advanced closed hybrid loop insulin pumps or continuous glucose monitoring (CGM) systems, among others, have increased the quality of life and improved glycaemic control of people with diabetes. However, only some patients have access to such technology, and only some want to use it. CGM has become much more widespread, but in terms of insulin delivery, most people with type 1 diabetes (T1D) and almost all people with type 2 diabetes (T2D) on insulin therapy are treated with multiple-dose insulin injections (MDI) rather than an insulin pump. For these patients, using connected insulin pens or caps has shown benefits in reducing missed insulin injections and promoting correct administration over time. In addition, using these devices improves the quality of life and user satisfaction. The integration of insulin injection and CGM data facilitates both users and the healthcare team to analyse glucose control and implement appropriate therapeutic changes, reducing therapeutic inertia. This expert's recommendation reviews the characteristics of the devices marketed or in the process of being marketed and their available scientific evidence. Finally, it suggests the profile of users and professionals who would benefit most, the barriers to its generalisation and the changes in the care model that implementing these devices can bring with it

Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality

Effect of Spontaneous and Water-Based Passivation on Components and Parameters of Ti6Al4V (ELI Grade) Surface Tension and Its Wettability by an Aqueous Solution of Sucrose Ester Surfactants

Solid wettability is especially important for biomaterials and implants in the context of microbial adhesion to their surfaces. This adhesion can be inhibited by changes in biomaterial surface roughness and/or its hydrophilic&ndash;hydrophobic balance. The surface hydrophilic&ndash;hydrophobic balance can be changed by the specifics of the surface treatment (proper conditions of surface preparation) or adsorption of different substances. From the practical point of view, in systems that include biomaterials and implants, the adsorption of compounds characterized by bacteriostatic or bactericidal properties is especially desirable. Substances that are able to change the surface properties of a given solid as a result of their adsorption and possess at least bacteriostatic properties include sucrose ester surfactants. Thus, in our studies the analysis of a specific surface treatment effect (proper passivation conditions) on a biomaterial alloy&rsquo;s (Ti6Al4V ELI, Grade 23) properties was performed based on measurements of the contact angles of water, formamide and diiodomethane. In addition, the changes in the studied solid surface&rsquo;s properties resulting from the sucrose monodecanoate (SMD) and sucrose monolaurate (SML) molecules&rsquo; adsorption at the solid&ndash;water interface were also analyzed. For the analysis, the values of the contact angles of aqueous solutions of SMD and SML were measured at 293 K, and the surface tensions of the aqueous solutions of studied surfactants measured earlier were tested. From the above-mentioned tests, it was found that water environment significantly influences the components and parameters of Ti6Al4V ELI&rsquo;s surface tension. It also occurred that the addition of both SMD and SML to water (separately) caused a drop in the water contact angle on Ti6Al4V ELI&rsquo;s surface. However, the sucrose monolaurate surfactant is characterized by a slightly better tendency towards adsorption at the solid&ndash;water interface in the studied system compared to sucrose monodecanoate. Additionally, based on the components and parameters of Ti6Al4V ELI&rsquo;s surface tension calculated from the proper values of components and parameters of model liquids, it was possible to predict the wettability of Ti6Al4V ELI using the aqueous solutions of SMD and SML at various concentrations in the solution

Comparison of soil water-contents as measured with a neutron probe and time domain reflectometry in a Mediterranean forest (“Sierra de Gata”, Central Western Spain)

The present work compares the results obtained with two indirect techniques (neutron probe and time domain reflectometry, TDR) for measuring soil water contents ($\theta$) at different depths on an experimental plot in the “Sierra de Gata” (Central Western Spain). At the same time, the temporal and spatial evolution of $\theta$ was assessed in the zone studied. Measurements were made over three years (from September 1996 to August 1999). The results point to a good correlation ($r = 0.98$) between q measured with both techniques, although TDR slightly (but significantly; $P < 0.01$) underestimated the q values, but only during the drying periods and with low q values. Non-significant differences between both methods were found for the estimation of soil water contents in the whole soil profile. Accordingly, both techniques are interchangeable and it is thus possible to avoid the potential risk of radioactivity. Considerable inter-annual variability was observed in the soil water content, governed by the annual rainfall distribution. A “flowing-off” effect was observed, followed by a progressive re-wetting of the soil profile from the bottom. Both the temporal and spatial variabilities of soil water content were found to decrease with depth.Comparaison des mesures de teneurs en eau du sol effectuées par sonde à neutrons et TDR dans une forêt méditerranéenne (“ Sierra de Gata ”, Espagne Centre-Ouest). Le présent travail avait pour objectif de comparer deux méthodes indirectes de mesure de la teneur en eau ($\theta$) du sol : sonde à neutrons et TDR (Time Domain Reflectometry) dans le cas d'une parcelle forestière située dans la “ Sierra de Gata ”, région du Centre-Ouest de l'Espagne. Les aspects de variabilités temporelle et spatiale ont été également abordés. Une campagne de mesures s'est poursuivie de septembre 1996 jusqu'à août 1999, soit près de 3 ans. Les résultats obtenus montrent une bonne corrélation ($r = 0,98$) entre $\theta$ mesurées avec les deux techniques. L'estimation de la teneur en eau du sol pour l'ensemble du profil montre des différences non significatives ($P > 0,05$), bien que le TDR sous-estime légèrement (mais de façon significative ; $P < 0.01$) les valeurs de $\theta$ seulement quand le sol s'assèche et pour des valeurs de $\theta$ faibles. Les deux techniques sont donc a-priori interchangeables et il est donc possible d'envisager le remplacement des méthodes nucléaires et d'éviter ainsi les risques correspondants. Sur le plan de l'hydrologie, on a constaté une variabilité, temporelle et spatiale, décroissante avec la profondeur du sol et une considérable variabilité inter-annuelle liée aux fluctuations du régime des pluies. Enfin, un phénomène de transfert rapide vers le bas suivi d'une réhumectation par inhibition vers le haut a été également mis en évidence

Influence of Solvent and Substrate on Hydrophobicity of PLA Films

The study of the surface properties of materials is key in determining whether the material will be suitable for medical purposes. One of these properties is hydrophobicity, which is important when assessing its behavior against bacterial adhesion. In this work, we have studied the influence of the solvent (chloroform, acetone, and tetrahydrofuran) and the substrate (glass, PTFE, silicone, and Ti6Al4V) on which polylactic acid is deposited in solution to manufacture films by solvent-casting. Thus, it has been found that there are no significant differences in hydrophobicity and surface tension among the solvents evaluated, but there are significant differences with respect to the substrates: PLA films casted on silicone are hydrophobic, while those casted on the rest of the substrates are hydrophilic. This is related to the fact that the silicone interacts with the polymer modifying its spatial arrangement, exposing its methyl groups towards the interface with the air. In this way, it has been shown that, when manufacturing PLA films, it is important to choose the right surface on which to deposit them, depending on their desired function

Surface Characterisation of Human Serum Albumin Layers on Activated Ti6Al4V

Adpsortion of protein layers on biomaterials plays an important role in the interactions between implants and the bio-environment. In this context, human serum albumin (HSA) layers have been deposited on modified Ti6Al4V surfaces at different ultraviolet (UV-C) irradiation times to observe possible changes in the adsorbed protein layer. Protein adsorption was done from solutions at concentraions lower than the serum protein concentration, to follow the surface modifications at the beginning of the albumin adhesion process. For this purpose, the surface of the protein-coated samples has been characterized by time of flight secondary ion mass spectrometry (ToF-SIMS), contact angle and zeta potential measurements. The results obtained show a reduction in the total surface tension and zeta potential of samples treated with UV-C light when coated with a protein layer. Furthermore, the UV-C light treatment applied to titanium alloy surfaces is able to modify the conformation, orientation and packing of the proteins arranged in the adsorbed layer. Low irradiation time generates an unstable surface with the lowest protein adsorption and the highest hydrophobic/hydrophilic protein ratio, indicating a possible denaturalization of the protein on these surfaces. However, surface changes are stabilized after 15 h or UV-C irradiation, favoring the protein adsorption through electrical interactions

Bacterial Response to the Surface Aging of PLA Matrices Loaded with Active Compounds

The use of active components in biomaterials improves the properties of existing ones and makes it possible to obtain new devices with antibacterial properties that prevent infections after implantation, thus guaranteeing the success of the implant. In this work, cetyltrimethylammonium bromide (CTAB) and magnesium particles were incorporated into polylactic acid (PLA) films to assess the extent to which progressive aging of the new surfaces resists bacterial colonization processes. For this purpose, the films&rsquo; surface was characterized by contact angle measurements, ToF-SIMS and AFM, and adhesion, viability and biofilm growth of Staphylococcus epidermidis bacteria on these films were also evaluated. The results show that the inclusion of Mg and CTAB in PLA films changes their surface properties both before and after aging and also modifies bacterial adhesion on the polymer. Complete bactericidal activity is exhibited on non-degraded films and films with CTAB. This antibacterial behavior is maintained after degradation for three months in the case of films containing a higher amount of CTAB

Dynamic Adhesive Behavior and Biofilm Formation of <i>Staphylococcus aureus</i> on Polylactic Acid Surfaces in Diabetic Environments

Interest in biodegradable implants has focused attention on the resorbable polymer polylactic acid. However, the risk of these materials promoting infection, especially in patients with existing pathologies, needs to be monitored. The enrichment of a bacterial adhesion medium with compounds that are associated with human pathologies can help in understanding how these components affect the development of infectious processes. Specifically, this work evaluates the influence of glucose and ketone bodies (in a diabetic context) on the adhesion dynamics of S. aureus to the biomaterial polylactic acid, employing different approaches and discussing the results based on the physical properties of the bacterial surface and its metabolic activity. The combination of ketoacidosis and hyperglycemia (GK2) appears to be the worst scenario: this system promotes a state of continuous bacterial colonization over time, suppressing the stationary phase of adhesion and strengthening the attachment of bacteria to the surface. In addition, these supplements cause a significant increase in the metabolic activity of the bacteria. Compared to non-enriched media, biofilm formation doubles under ketoacidosis conditions, while in the planktonic state, it is glucose that triggers metabolic activity, which is practically suppressed when only ketone components are present. Both information must be complementary to understand what can happen in a real system, where planktonic bacteria are the ones that initially colonize a surface, and, subsequently, these attached bacteria end up forming a biofilm. This information highlights the need for good monitoring of diabetic patients, especially if they use an implanted device made of PLA