How do wettability, zeta potential and hydroxylation degree affect the biological response of biomaterials?

It is well known that composition, electric charge, wettability and roughness of implant surfaces have great influence on their interaction with the biological fluids and tissues, but systematic studies of different materials in the same experimental conditions are still lacking in the scientific literature. The aim of this research is to investigate the correlations between some surface characteristics (wettability, zeta potential and hydroxylation degree) and the biological response (protein adsorption, blood wettability, cell and bacterial adhesion) to some model biomaterials. The resulting knowledge can be applied for the development of future innovative surfaces for implantable biomaterials. Roughness was not considered as a variable because it is a widely explored feature: smooth surfaces prepared by a controlled protocol were compared in order to have no roughness effects. Three oxides (ZrO2, Al2O3, SiO2), three metals (316LSS steel, Ti, Nb) and two polymers (corona treated polystyrene for cell culture and untreated polystyrene for bacteria culture), widely used for biomedical applications, were considered. The surfaces were characterized by contact profilometry, SEM-EDS, XPS, FTIR, zeta potential and wettability with different fluids. Protein adsorption, blood wettability, bacterial and cell adhesion were evaluated in order to investigate the correlations between the surface physiochemical properties and biological responses. From a methodological standpoint, XPS and electrokinetic measurements emerged as the more suitable techniques respectively for the evaluation of hydroxylation degree and surface charge/isoelectric point. Moreover, determination of wettability by blood appeared a specific and crucial test, the results of which are not easily predictable by using other type of tests. Hydroxylation degree resulted correlated to the wettability by water, but not directly to surface charge. Wetting tests with different media showed the possibility to highlight some differences among look-alike materials. A dependence of protein absorption on hydroxylation degree, charge and wettability was evidenced and its maximum was registered for surfaces with low wettability in both water based and protein containing media and a moderate surface charge. As far as bacterial adhesion is concerned, no effect of surface charge or protein adsorption was evidenced, while the presence of a high acid component of the surface energy appeared significant. Finally, the combination of hydroxylation degree, wettability, surface charge and energy (polar component) emerged as a key parameter for cell adhesion and viability.

Acid tolerance and fecal recovery following oral administration of Saccharomyces cerevisiae.

Probiotic microorganisms to be used as biotherapeutic agents have to resist the rigors of the upper human gastrointestinal tract. In this study we evaluated the acid tolerance in vitro and the fecal recovery in vivo after oral administration of a Saccharomyces cerevisiae strain to healthy volunteers. At the lowest pH value (pH 1.0) the yeast load in tablets decreased slightly. From pH 1.0 to pH 7.0 the release of S. cerevisiae in buffer solutions increased. The selected yeast strain showed good tolerance to low pH which mimic the gastric environment. After one month of treatment at a dose of 100 million cells per day, S. cerevisiae grew from the feces of 6 (37.5%) of the 16 healthy, treated volunteers. Based on the results of the present experiments the yeast studied can be considered a strain that tolerates adverse conditions comparable to those of the human gastrointestinal tract, and when administered orally may colonize the bowel of healthy volunteers and even replace resident Candida species.

Reversal of cachexia in patients treated with potent antiretroviral therapy.

The introduction of HAART has changed the nutritional status of HIV patients. In the pre-protease inhibitor (PI) era, more than 60% of HIV-positive persons presented with protein energy malnutrition (PEM) and vitamin and mineral deficit. This caused progressive physical-metabolic wasting (wasting syndrome/cachexia) and increased susceptibility to opportunistic infections and drug toxicity. PEM was a concurrent cause in 80% of deaths attributed to AIDS. Since 1996, the year in which PIs were introduced, the number of patients dying as a result of AIDS has decreased by two thirds, and cachexia is no longer the AIDS terminal phase in developed countries. But different patterns of nutritional status changes have appeared in association with the use of newer anti-HIV therapies and with longer survival of HIV-infected patients. A new clinical and laboratory syndrome--lipodystrophy syndrome--now affects patients receiving PI-based therapy. This syndrome consists of changes in body shape that are caused by an abnormal redistribution of fat. Fat accumulates in the abdominal area (truncal and visceral obesity), in the axillary pads (bilateral symmetric lipomatosis), and in the dorsocervical pads ("buffalo hump," "bull neck") but decreases in the legs, arms, and nasolabial and cheek pads (peripheral lipodystrophy). Hyperlipidemia and insulin resistance are also frequently present (metabolic syndrome X). Pathogenic mechanisms of lipid and fat tissue disturbances are discussed in this article, and the clinical approach to patient management and therapeutic options for lipodystrophy and lipid dysmetabolism is evaluated.

Vitamin D protects human endothelial cells from oxidative stress through the autophagic and survival pathways.

CONTEXT: Recently, vitamin D (VitD) has been recognized as increasingly importance in many cellular functions of several tissues and organs other than bone. In particular, VitD showed important beneficial effects in the cardiovascular system. Although the relationship among VitD, endothelium, and cardiovascular disease is well established, little is known about the antioxidant effect of VitD. OBJECTIVE: Our objective was to study the intracellular pathways activated by VitD in cultured human umbilical vein endothelial cells undergoing oxidative stress. DESIGN: Nitric oxide production, cell viability, reactive oxygen species, the mitochondrial permeability transition pore, membrane potential, and caspase-3 activity were measured during oxidative stress induced by administration of 200 µM hydrogen peroxide for 20 minutes. Experiments were repeated in the presence of specific vitamin D receptor ligand ZK191784. RESULTS: Pretreatment with VitD alone or in combination with ZK191784 is able to reduce the apoptosis-related gene expression, involving both intrinsic and extrinsic pathways. At the same time, it has been shown the activation of pro-autophagic beclin 1 and the phosphorylation of ERK1/2 and Akt, indicating a modulation between apoptosis and autophagy. Moreover, VitD alone or in combination with ZK191784 is able to prevent the loss of mitochondrial potential and the consequent cytochrome C release and caspase activation. CONCLUSIONS: The present study shows that VitD may prevent endothelial cell death through modulation of the interplay between apoptosis and autophagy. This effect is obtained by inhibiting superoxide anion generation, maintaining mitochondria function and cell viability, activating survival kinases, and inducing NO production.

Ocular manifestations of congenital toxoplasmosis.

PURPOSE: To evaluate the ocular manifestations of congenital toxoplasmosis at the first ophthalmological examination of children up to the age of 12 months. METHODS: Cross-sectional study of 44 children with a confirmed diagnosis of congenital toxoplasmosis. In all patients, complete ophthalmological examinations were performed under sedation. The patients underwent biomicroscopy of the anterior segment, skiascopy under cyclopegia, and indirect binocular ophthalmoscopy with maximum mydriasis. RESULTS: The mean age of patients was 4.2 months. Of the 44 children evaluated, 31 (70.4%) presented ocular involvement and 29 (65.9%) of them had retinochoroiditis lesions. The retinochoroiditis lesions were bilateral in 22 (75.8%) patients and unilateral in 7 (24.2%). The retinochoroiditis lesions were active in 8 (15.7%) eyes and had healed in 43 (84.3%). Most of the lesions were concentrated in the papillomacular area (76.3%). Other associated ocular alterations were present in 22 children, the most prevalent being cataract, microphthalmia, and strabismus. CONCLUSION: Ocular involvement in congenital toxoplasmosis might be much more frequent and occurs earlier than previously described.

Levosimendan induces NO production through p38 MAPK, ERK and Akt in porcine coronary endothelial cells: role for mitochondrial K(ATP) channel.

BACKGROUND AND PURPOSE: Levosimendan acts as a vasodilator through the opening of ATP-sensitive K(+) channels (K(ATP)) channels. Moreover, the coronary vasodilatation caused by levosimendan in anaesthetized pigs has recently been found to be abolished by the nitric oxide synthase (NOS) inhibitor N(omega)-nitro-L-arginine methyl ester, indicating that nitric oxide (NO) has a role in the vascular effects of levosimendan. However, the intracellular pathway leading to NO production caused by levosimendan has not yet been investigated. Thus, the purpose of the present study was to examine the effects of levosimendan on NO production and to evaluate the intracellular signalling pathway involved. EXPERIMENTAL APPROACH: In porcine coronary endothelial cells (CEC), the release of NO in response to levosimendan was examined in the presence and absence of N(omega)-nitro-L-arginine methyl ester, an adenylyl cyclase inhibitor, K(ATP) channel agonists and antagonists, and inhibitors of intracellular protein kinases. In addition, the role of Akt, ERK, p38 and eNOS was investigated through Western blot analysis. KEY RESULTS: Levosimendan caused a concentration-dependent and K(+)-related increase of NO production. This effect was amplified by the mitochondrial K(ATP) channel agonist, but not by the selective plasma membrane K(ATP) channel agonist. The response of CEC to levosimendan was prevented by the K(ATP) channel blockers, the adenylyl cyclase inhibitor and the Akt, ERK, p38 inhibitors. Western blot analysis showed that phosphorylation of the above kinases lead to eNOS activation. CONCLUSIONS AND IMPLICATIONS: In CEC levosimendan induced eNOS-dependent NO production through Akt, ERK and p38. This intracellular pathway is associated with the opening of mitochondrial K(ATP) channels and involves cAMP.

Allergy to all mammalian Bovidae proteins but cow's milk in a child

No disponible