Protein Corona Formation on Magnetite Nanoparticles: Effects of Culture Medium Composition, and Its Consequences on Superparamagnetic Nanoparticle Cytotoxicity.

The physicochemical properties and potential cytotoxicity of nanoparticles (NPs) are significantly influenced by their inter- action with proteins, which results in corona formation. Here, we have determined whether corona formation, resulting from interactions between superparamagnetic iron oxide nanoparticles (SPIONs) and different cell culture media, may have consequences for driving NP toxic effects. To address this issue, complementary methods were used. The deter- mination of the hydrodynamic size distribution by ζ (zeta) potential measurement indicated that SPIONs were negatively charged under all conditions but that the actual charge was differed with the cell culture medium used. In vitro protein adsorption studies were carried out using the Bradford protein assay and Fourier transform infrared spectroscopy (FTIR). The Bradford assay revealed that the concentration of unadsorbed proteins and other biomolecules decreased when the SPION concentration increased. FTIR showed that the proteins were, indeed, adsorbed onto the NP surface. This was followed by matrix-assisted laser desorption/ionization time-of-flight secondary ion mass spectrometry (MALDI TOF-SIMS), to identify the adsorbed proteins. Ultimately, three different cell viability assays led to the conclusion that the SPIONs were not toxic for all the concentrations used here. In summary, we found that corona formation on the SPIONs depends on the composition of the culture media but has no consequence for nanotoxicity. We have shown that the application of complementary methods has provided novel insights into SPION/protein interactions.

Bacteriophages: biosensing tools for multi-drug resistant pathogens.

Pathogen detection is of utmost importance in many sectors, such as in the food industry, environmental quality control, clinical diagnostics, bio-defence and counter-terrorism. Failure to appropriately, and specifically, detect pathogenic bacteria can lead to serious consequences, and may ultimately be lethal. Public safety, new legislation, recent outbreaks in food contamination, and the ever-increasing prevalence of multidrug-resistant infections have fostered a worldwide research effort targeting novel biosensing strategies. This review concerns phage-based analytical and biosensing methods targeted towards theranostic applications. We discuss and review phage-based assays, notably phage amplification, reporter phage, phage lysis, and bioluminescence assays for the detection of bacterial species, as well as phage-based biosensors, including optical (comprising SPR sensors and fiber optic assays), electrochemical (comprising amperometric, potentiometric, and impedimetric sensors), acoustic wave and magnetoelastic sensors.

[Length of hospitalization for inpatient treatment of depression. Results of a multicentre study on the effects of a new treatment model]. / Verweildauer in der stationären Depressionsbehandlung. Ergebnisse einer Multicenterstudie zum Effekt eines neuen Behandlungsmodells.

BACKGROUND: Patients with depression are treated for a relatively long period as inpatients in Germany. A new treatment model with symptom-orientated release management, post-hospitalization treatment and standardized referral to outpatient therapists could be suitable to specifically shorten the hospital stay of patients who have already profited sufficiently from treatment. MATERIALS AND METHODS: The aim of the present study was to investigate the effects of a new treatment method (intervention group) with hospitalized depressive patients in comparison to a standard protocol (treatment-as-usual control group) on the length of stay as part of a pragmatic randomized, controlled multicentre study. The evaluation was made using covariance analysis. RESULTS: Of the 202 randomized patients 184 could be included in the analysis. The estimated marginal mean of the length of stay (n = 83) was 57.3 days (range 1-305 days, SE = 3.8) in the intervention group and (n = 101) 57.6 days (range: 6-196 days, SE = 3.5) in the control group. There were no significant statistical differences between the groups (p = 0.966). CONCLUSIONS: An effect of the new treatment model on the inpatient length of hospital stay in depressive patients could not be demonstrated.

Core-shell nanoparticles as prodrugs: possible cytotoxicological and biomedical impacts of batch-to-batch inconsistencies.

Numerous samples of magnetite@silica and magnetite@silica@silane core-shell nanoparticles, previously used as prodrugs, were prepared by an experienced chemist, using the same identical equipment and the same lots of reagents. Their surface analyses showed batch-to-batch chemical variations: no two batches were found to have the same surface chemistries, showing unexpected Si-O bond scission and amine oxidation. Because the preparations used reactions recognized to be mild, and bond scission and oxidation were never previously reported for similar reactions on larger surfaces, the Fe(3)O(4) nanoparticles that form the nanoparticle core appear to have acted as catalysts for these side reactions. The intended use of these nanoparticles, as drug carriers, is discussed in terms of cytotoxicological and biomedical consequences.

Nitric oxide delivery by core/shell superparamagnetic nanoparticle vehicles with enhanced biocompatibility.

We report the synthesis of Fe(3)O(4)/silica core/shell nanoparticles and their functionalization with S-nitrosothiols. These nanoparticles are of immense interest because of their nitric oxide (NO) release capabilities in human alveolar epithelial cells. Moreover, they act as large storage reservoirs of NO that can be targeted magnetically to the specific site with a sustainable release of NO for up to 50 h. Such nanoparticles provide an enhancement of the biocompatibility with released NO while allowing intracellular accumulation ascribed to their small size.

Comment on "The mathematical origins of the kinetic compensation effect" parts 1 and 2 by P. J. Barrie, Phys. Chem. Chem. Phys., 2012, 14, 318 and 327.

The concept of kinetic compensation and the associated isokinetic relation continue to be subject to debate, despite the fact that the conditions under which they are to be expected are now well established, and the criteria for deciding that they have been observed are known. We present these conditions and criteria, and the reality of these relations, and stress their importance for catalysis. We then discuss the fact that statistical arguments against their reality continue to be presented. Recently two articles, based upon the statistical point of view have been published in this Journal. We show that, despite the fact that the mathematics of these articles is error free, they present a distorted image of the present understanding of the subject.

In vitro biocompatibility assessment of functionalized magnetite nanoparticles: biological and cytotoxicological effects.

In the biomedical field, nanomaterials have the potential for use in the targeted delivery of drugs in the human body and in the diagnosis and therapy of certain diseases. In the category of targeted delivery, magnetite (Fe(3)O(4)) nanoparticles have received much attention. As with any similar new therapy, when such nanoparticles are functionalized with chemical groups designed to permit the specific attachment of drugs, cytotoxicological testing is necessary before moving to animal models. Here, we consider several variously functionalized magnetite nanoparticles, including those prepared with (1) a monolayer of oleic acid (Fe(3)O(4)@OA), which is subsequently converted to (2) a shell of amine-containing silane (Fe(3)O(4)@NH(2)), (3) a shell of silica (Fe(3)O(4)@SiO(2)), and (4) a shell of amine-containing silane over a shell of silica (Fe(3)O(4)@SiO(2)@NH(2)). These latter three functionalities were evaluated for biocompatibility, cellular morphology, mitochondrial function (MTT assay), lactate dehydrogenase membrane leakage (LDH assay), and proinflammatory potential through enzyme linked immunosorbent assay (ELISA) for interleukin 6 (IL-6). Controlled tests were performed over a period of 72 h, with results showing LDH leakage and abnormal Il-6 secretion at high concentrations (>50 µg/mL). The tests showed that, in addition to the surface characteristics of the nanoparticles, both the nutrient medium and the time of suspension before exposure to cells also contribute to nanoparticle cytotoxicity.

Asymmetries in transition metal XPS spectra: metal nanoparticle structure, and interaction with the graphene-structured substrate surface.

Transition-metal XPS spectra have traditionally been considered to possess a natural asymmetry, extending to the high-binding-energy side. This is based on the fact that these spectra have generally been found experimentally to have such an asymmetry, as well as on the confirmation of asymmetry offered by the Doniach-Sunjic equation, an equation based on the proposal that the conduction electron scattering amplitude for interband absorption or emission in metals, at the Fermi level, is a singularity. Our discovery that metal nanoparticles, prepared under vacuum and characterized without exposure to air, have symmetric peaks, which become asymmetric with time, informed us that these peak asymmetries have other sources. On the basis of our belief that all metal spectra are composed of symmetric peaks, where the asymmetries are attributed to overlapping minor peaks that are consistent with known physical and chemical phenomena associated with that metal, we have shown that, for the metals that we have studied, these asymmetries contain much information, otherwise unavailable, on the structures, contaminants, oxidation, and interfacial interactions of nanoparticle surfaces. The existence of this information has been demonstrated for several metals, and its value is shown by its use in explaining the strong interfacial bonding of the nanoparticles with substrates having graphene structures. A possible future research direction is offered in the field of metal-metal interactions in nanoparticle alloys.

Evidence of the interaction of evaporated Pt nanoparticles with variously treated surfaces of highly oriented pyrolytic graphite.

The interactions of Pt nanoparticles, deposited by evaporation onto highly oriented pyrolytic graphite surfaces modified by kiloelectronvolt Ar+ beam treatment, have been studied by X-ray photoelectron spectroscopy core-level line shape analysis. The C1s and Pt4f7/2 peaks were each considered to be composed of one asymmetric peak, and changes in their asymmetry parameters were used to study their interfacial interactions. In addition to these changes, strong signal intensity changes with time were found for both the C1s and Pt4f peaks, indicating an initial crystalline orientational instability of the Pt nanoparticles, which is supported by time-dependent high-resolution electron microscopy studies at elevated temperatures.

A mediatorless biosensor for putrescine using multiwalled carbon nanotubes.

Poly(diallyldimethylammonium) chloride, having a capability of dispersing multiwalled carbon nanotubes (MWCNTs), permits the modification of electrode surfaces. Together with putrescine oxidase, a MWCNT modified glassy carbon electrode was constructed for the development of a mediatorless putrescine biosensor. Nanoscale "dendrites" of MWCNTs were reasoned to form a network, projecting outward from the electrode surface acting like bundled ultra-microelectrodes, thereby permitting access to the active site and facilitating direct electron transfer to the immobilized enzyme. Our biosensor was capable of efficiently monitoring the direct electroactivity of putrescine oxidase at the electrode surface. Direct electron transfer permits the detection of putrescine at negative potentials, circumventing the interference of endogenous ascorbic and uric acids, which often complicate the analysis of important compounds in plasma. Compared with the most common interfering species, such as spermine, spermidine, cadaverine, and histamine, a detection limit of 5 microM and a response 20 times greater were found for putrescine. Tests performed on plasma of cancerous mice demonstrated that the detection of putrescine could be carried out very quickly on mammalian plasma without previous purification.

Surface diffusion and coalescence of mobile metal nanoparticles.

The diffusion and coalescence of metal nanoparticles play important roles in many phenomena. Here, we offer a new integrated overview of the main factors that control the nanoparticle coalescence process. Three factors are considered in our description of the coalescence process: nanoparticle diffusion across the surface, their physical and thermodynamic properties, and the mechanism of coalescence. We demonstrate that the liquid-like properties of the surface layers of the nanoparticles play an essential role in this process. We present experimental evidence for our opinion, based on the high-resolution electron microscopic analysis of several different types of nanoparticles.

Interaction of evaporated nickel nanoparticles with highly oriented pyrolytic graphite: Back-bonding to surface defects, as studied by X-ray photoelectron spectroscopy.

Ni nanoparticle evaporation onto highly oriented pyrolytic graphite (HOPG), with low and high surface defect densities, has been studied in situ by X-ray photoelectron spectroscopic (XPS) techniques, including binding energy shifts, Auger parameters, and Wagner plots. Ni nucleates at defect sites, whether initially present or those introduced by Ar+ bombardment, with the formation of spherical nanoparticles, which adhere strongly through Ni/HOPG back-bonding. The variation of the C 1s peak intensity with Ni coverage suggests that the photoelectron emission yield may be enhanced at lower Ni coverages, due to Ni nanoparticle-induced electron localization and work function reduction at the HOPG surface, which is evidence of such back-bonding.

A tapping mode AFM study of collapse and denaturation in dentinal collagen.

OBJECTIVES: Tapping mode atomic force microscopy (AFM) was used to investigate the surface changes of collagen exposed to phosphoric acid treatment. We focus on denaturation and collapse following demineralization and exposure to air. METHODS: Unpolished dentin disks, obtained from freshly extracted human molars, were etched in 37% phosphoric acid for 15s, rinsed ultrasonically and gently blotted with soft paper; the specimens were then continuously observed using tapping mode AFM. RESULTS: Immediately after the removal of bulk water, the surface consisted of a porous network of banded collagen fibrils, having periodicities of 67nm. After approximately 8min of subsequent air-drying, the spacing between fibrils was lost, and the surface was observed to consist of a dense array of closely spaced fibrils. The banding periodicity was still observable. SIGNIFICANCE: The air drying of etched dentin results in the collapse of the collagen network, but not in the denaturation of the collagen fibrils. This study indicates that collapse and denaturation are separate phenomena. It further shows that water loss occurs rapidly, and disrupts the native conformation of the collagen network. This would have adverse effects on adhesion.

A photoacoustic FTIRS study of the chemical modifications of human dentin surfaces: I. Demineralization.

Acids are used to modify the structure and composition of dentin surfaces to improve bonds formed with resins. The purpose of this work is to investigate such chemical modifications using the surface-sensitive technique photoacoustic Fourier transform infrared spectroscopy (PA-FTIRS). Spectra of acid-treated samples (citric, maleic, nitric, and phosphoric at pH = 1.0) were recorded at various time intervals. Analysis of these spectra indicates a gradual increase in sample surface area with treatment time. A decrease of the bands associated with calcium hydroxyapatite (HAP) and carbonate apatite inherent to the mineral phase of dentin are also observed. A comparison of spectra of samples treated for 2 min with each acid also reveals that maleic and phosphoric acids remove more HAP than citric acid. We conclude that citric acid may cause the formation of precipitates at the etching front which inhibit etching.

A photoacoustic FTIRS study of the chemical modifications of human dentin surfaces: II. Deproteination.

This work focuses on the chemical alterations occurring on the dentin surface on treatment with sodium hypochlorite (NaOCl), a known deproteinating agent. In addition, sequential treatment with both acid and NaOCl are characterized. Modifications are evaluated using photoacoustic FTIR (PA-FTIRS), a surface-sensitive spectroscopy. Spectra of NaOCl-treated dentin samples show a slow and heterogeneous removal of its organic phase, leaving calcium hydroxyapatite and carbonate apatite unchanged. Spectra of this deproteinated surface resemble those of apatites synthesized at low temperatures and having very high-surface areas. A combined sequential 2-min treatment of dentin with both maleic acid and NaOCl indicates that this treatment can produce a surface region which is neither significantly demineralized nor deproteinated. This sequential treatment can be used to remove the smear layer and restore the dentin surface to its natural composition.

Field emission in-lens SEM study of enamel and dentin.

This investigation used field emission in-lens scanning electron microscopy (FEISEM) for the study of tooth surfaces, with particular reference to adhesive bonding and acid conditioning. Dentin wafers with an intact enamel periphery were treated by either ethylenediaminetetraacetic acid (EDTA) (pH 7.4) or phosphoric acid (pH 0.7). The samples were then fixed, sequentially dehydrated in alcohol, and either air- or critical point-dried. After coating, surfaces were examined by FEISEM. For enamel, intraprismatic crystals were clearly recognizable, with the crystals showing both a longitudinal and parallel orientation to the long axis of the prisms. For dentin, the surface ultrastructure (mineral crystals and collagen banding) for the both untreated and treated samples was observed. Fine structures measuring on the order of 6 nm were also observed on samples treated by EDTA. We conclude that FEISEM can routinely provide high-resolution images of enamel and dentin, and that it has the capability of revealing the defined distribution of crystals and collagen fibers in dental tissues.

Moisture-dependent renaturation of collagen in phosphoric acid etched human dentin.

We used atomic force microscopy (AFM) to investigate the effects of acidic and aqueous treatments on human dentin. Two basic points were determined: the first is the ability of AFM to discriminate the effect of phosphoric acid (pH approximately equal to 1) on polished dentin, and the second is the demonstrable effect of moisture on fibrous collagen structure. AFM images confirmed that the polishing process led to the removal of both smear layer and smear plugs. Our AFM study of undried dentin, which was then acid treated and kept moist, revealed substantial morphological changes at the dentin surface. Collagen fibers, having a characteristic periodicity of 67 nm, were imaged in situ for the first time; these structures were absent in dentin treated by phosphoric acid and subsequently vacuum dried, even after prolonged reimmersion in water. The AFM technique permitted us to demonstrate the important roles that moisture and etching play in the determination of the structure of collagen fibrils. Such structure may also play an important role in the diffusibility of subsequently applied dental adhesion systems.