Titanium Surface Properties Influence the Biological Activity and FasL Expression of Craniofacial Stromal Cells.

Mesenchymal stromal cells (MSCs) can be easily isolated form craniofacial bones during routine dentistry procedures. Due to their embryological origin from neural crest, they represent a suitable cell population to study cell-biomaterial interaction in the craniofacial field, including osteoinductive/osteointegrative processes. The biological and immunomodulatory properties of MSCs may be influenced by chemistry and topography of implant surfaces. We investigated if and how three different titanium surfaces, machined (MCH), sandblasted with resorbable blasting medium (RBM), and Ca++-nanostructured (NCA), may affect biological activity, osseointegration, and immunomodulatory properties of craniofacial MSCs. Cell proliferation, morphology, osteogenic markers, and FasL were evaluated on MSCs isolated from the mandibular bone after seeding on these three different surfaces. No statistically significant differences in cell proliferation were observed whereas different morphologies and growth patterns were detected for each type of surface. No difference in the expression of osteogenic markers was revealed. Interestingly, FasL expression, involved in the immunomodulatory activity of stem cells, was influenced by surface properties. Particularly, immunofluorescence analysis indicated that FasL expression increased on MCH surface compared to the others confirming the suggested role of FasL in promoting osteogenic differentiation. Titanium surface treatments and topography might reflect different biological behaviours of craniofacial MSCs and influence their osseointegration/immunomodulation properties.

Flow field-flow fractionation and multi-angle light scattering as a powerful tool for the characterization and stability evaluation of drug-loaded metal-organic framework nanoparticles.

Asymmetric flow field-flow fractionation (AF4) coupled with UV-Vis spectroscopy, multi-angle light scattering (MALS) and refractive index (RI) detection has been applied for the characterization of MIL-100(Fe) nanoMOFs (metal-organic frameworks) loaded with nucleoside reverse transcriptase inhibitor (NRTI) drugs for the first time. Empty nanoMOFs and nanoMOFs loaded with azidothymidine derivatives with three different degrees of phosphorylation were examined: azidothymidine (AZT, native drug), azidothymidine monophosphate (AZT-MP), and azidothymidine triphosphate (AZT-TP). The particle size distribution and the stability of the nanoparticles when interacting with drugs have been determined in a time frame of 24 h. Main achievements include detection of aggregate formation in an early stage and monitoring nanoMOF morphological changes as indicators of their interaction with guest molecules. AF4-MALS proved to be a useful methodology to analyze nanoparticles engineered for drug delivery applications and gave fundamental data on their size distribution and stability. Graphical abstract ᅟ.

Plaque accumulation on titanium disks with different surface treatments: an in vivo investigation.

Implants with rough surfaces are today widely used. It has been speculated that rough surfaces (Ra > 0.2 µm) provide a better "substrate" for retention and accumulation of plaque in terms of area, thickness and colony-forming unit that can eventually lead to peri mucositis and/or peri-implantitis. The aim of this investigation was to evaluate in vivo the plaque accumulation after 48 h on three implant surfaces with different treatments. For this investigation, we used 21 sterilized titanium disks, with a diameter of 8mm and a thickness of 3 mm, provided by the manufacturer: 7 with machined surface, as smooth control, 7 with HA grit sandblasted RBM surface and 7 with Ca++ incorporated in titanium Xpeed surface. One disk for each surface treatment was characterized at time 0 by SEM and AFM to study, respectively, the surface morphology and roughness. The other 18 disks were mounted randomly on three upper acrylic bites in a buccal lateral position, worn for 48 h by three volunteer students for plaque accumulation. After 48 h each disk was removed and analyzed qualitatively and quantitatively by an independent operator, not involved into the study, in order to avoid bias. Data collected were statistically analyzed by one-way ANOVA. The qualitative analysis showed no differences in terms of total plaque accumulation between the surfaces. Data from quantitative analysis using Anova Test showed no significance between all groups. In this in vivo investigation all the surfaces studied promoted plaque formation. The degree of surface roughness seems not to be a critical factor for plaque accumulation.

Hydrodynamic size-based separation and characterization of protein aggregates from total cell lysates.

Herein we describe a protocol that uses hollow-fiber flow field-flow fractionation (FFF) coupled with multiangle light scattering (MALS) for hydrodynamic size-based separation and characterization of complex protein aggregates. The fractionation method, which requires 1.5 h to run, was successfully modified from the analysis of protein aggregates, as found in simple protein mixtures, to complex aggregates, as found in total cell lysates. In contrast to other related methods (filter assay, analytical ultracentrifugation, gel electrophoresis and size-exclusion chromatography), hollow-fiber flow FFF coupled with MALS allows a flow-based fractionation of highly purified protein aggregates and simultaneous measurement of their molecular weight, r.m.s. radius and molecular conformation (e.g., round, rod-shaped, compact or relaxed). The polyethersulfone hollow fibers used, which have a 0.8-mm inner diameter, allow separation of as little as 20 µg of total cell lysates. In addition, the ability to run the samples in different denaturing and nondenaturing buffer allows defining true aggregates from artifacts, which can form during sample preparation. The protocol was set up using Paraquat-induced carbonylation, a model that induces protein aggregation in cultured cells. This technique will advance the biochemical, proteomic and biophysical characterization of molecular-weight aggregates associated with protein mutations, as found in many CNS degenerative diseases, or chronic oxidative stress, as found in aging, and chronic metabolic and inflammatory conditions.

Host-guest interactions in Fe(III)-trimesate MOF nanoparticles loaded with doxorubicin.

Doxorubicin (DOX) entrapment in porous Fe(III)-trimesate metal organic frameworks (MIL-100(Fe)) nanoparticles was investigated in neutral Tris buffer via UV-vis absorption, circular dichroism (CD), and fluorescence. The binding constants and the absolute spectra of the DOX-MIL-100(Fe) complexes were determined via absorption and fluorescence titrations. A binding model where DOX associates as monomer to the dehydrated Fe3O (OH)(H2O)2 [(C6H3)(CO2)3]2 structural unit in 1:1 stoichiometry, with apparent association constant of (1.1 to 1.8) × 10(4) M(-1), was found to reasonably fit the experimental data. Spectroscopic data indicate that DOX binding occurs via the formation of highly stable coordination bonds between one or both deprotonated hydroxyl groups of the aglycone moiety and coordinatively unsaturated Fe(III) centers. Complete quenching of the DOX fluorescence and remarkable thermal and photochemical stability were observed for DOX incorporated in the MIL-100(Fe) framework.

Flow field-flow fractionation for the analysis of nanoparticles used in drug delivery.

Structured nanoparticles (NPs) with controlled size distribution and novel physicochemical features present fundamental advantages as drug delivery systems with respect to bulk drugs. NPs can transport and release drugs to target sites with high efficiency and limited side effects. Regulatory institutions such as the US Food and Drug Administration (FDA) and the European Commission have pointed out that major limitations to the real application of current nanotechnology lie in the lack of homogeneous, pure and well-characterized NPs, also because of the lack of well-assessed, robust routine methods for their quality control and characterization. Many properties of NPs are size-dependent, thus the particle size distribution (PSD) plays a fundamental role in determining the NP properties. At present, scanning and transmission electron microscopy (SEM, TEM) are among the most used techniques to size characterize NPs. Size-exclusion chromatography (SEC) is also applied to the size separation of complex NP samples. SEC selectivity is, however, quite limited for very large molar mass analytes such as NPs, and interactions with the stationary phase can alter NP morphology. Flow field-flow fractionation (F4) is increasingly used as a mature separation method to size sort and characterize NPs in native conditions. Moreover, the hyphenation with light scattering (LS) methods can enhance the accuracy of size analysis of complex samples. In this paper, the applications of F4-LS to NP analysis used as drug delivery systems for their size analysis, and the study of stability and drug release effects are reviewed.

The role of bystanders in students' perception of bullying and sense of safety.

Two studies employing a mixed experimental design were conducted to determine if perceptions of bullying, attitudes towards victims, and students' sense of safety at school were influenced by bystanders' reactions to different types of bullying. In Study 1, 217 middle-school children were randomly assigned to read a hypothetical scenario describing a direct bullying episode. In Study 2, 376 primary-school children and 390 middle-school children were presented with scenarios describing a direct bullying episode and an indirect bullying episode. In all scenarios, the bystanders' reactions to the bullying and the gender of the victim were manipulated. Participants endorsed the prosocial behavior in favor of the victims and did not endorse pro-bullying behavior. Furthermore, they perceived passive reactions to the bullying as negative behavior. Participants showed positive attitudes towards victims, which were significantly higher at younger grade levels and among girls. Bystanders' behavior influenced both participants' perceptions of the victims and their perceived sense of safety at school. Implications for anti-bullying programs based upon the group ecology are discussed.