Cristina Satriano

A multitechnique study of preferential protein adsorption on hydrophobic and hydrophilic plasma-modified polymer surfaces.

The adsorption process of albumin, lysozyme and lactoferrin was investigated onto polymer surfaces, both hydrophobic and hydrophilic treated by oxygen-plasma. In particular thin films of polyhydroxymethylsiloxane (about 90 degrees of static water contact angle) were converted by oxygen plasma treatments at reduced pressure into hydrophilic SiO(x) phases (less than 10 degrees of water contact angle). The protein adsorption process was investigated in situ by quartz crystal microbalance with dissipation monitoring in terms of coverage and kinetics mechanism, while chemical structure and topography of the protein adlayers were studied ex situ by angular-resolved XPS and atomic force microscopy, respectively. The plasma surface modification of the polymer film drastically modified the adsorption process of the three proteins, both in terms of kinetics and coverage.

A Versatile Strategy for Signal Amplification Based on Core/Shell Silica Nanoparticles

The design of fluorescent chemosensors for biologicallyrelevant chemical species has important impacts in many ap-plications, and for this reason it has been the subject ofactive research in many laboratories worldwide. The ach-ievements in this wide research topic have promoted enor-mous steps forwards, for example, in the field of cell biology,thanks to the comprehension of the role of different chemi-cal species in many biological processes. Recently, research-ers have been moving from molecular chemosensors basedon two communicating units, a receptor and a dye, towardmore complex and sophisticated structures, and have triedto push further the limits of sensitivity and selectivity. Manydifferent solutions have been proposed but, among them,sensing systems based on nanoparticles are certainly one ofthe most interesting and promising.

Surface free energy and cell attachment onto ion-beam irradiated polymer surfaces

Abstract The paper reports evidence of the different cytocompatibility towards ion irradiated polymer surfaces. In particular, we studied the cell attachment, adhesion and spreading of normal human dermal fibroblast cells onto poly(hydroxymethylsiloxane) and poly(ethyleneterephthalate) surfaces modified by 50 keV Ar+ beams. The cell response is discussed in connection with the radiation-induced changes of the polymers surface chemical structure and related surface free energy, investigated by means of X-ray photoelectron spectroscopy and static contact angle measurements. The biological response is interpreted in terms of the different modification trends of the Surface Free Energy components, and its relationship to the protein adsorption processes from culture medium or to the direct cell-surface interaction in a protein-free saline solution. The results point towards a critical role of the electron-donor character of the surfaces, which seems able to trigger the optimal cell response to the employed polymeric surfaces.

Reduced Lipid Bilayer Thickness Regulates the Aggregation and Cytotoxicity of Amyloid-β

The aggregation of amyloid-β (Aβ) on lipid bilayers has been implicated as a mechanism by which Aβ exerts its toxicity in Alzheimers disease (AD). Lipid bilayer thinning has been observed during both oxidative stress and protein aggregation in AD, but whether these pathological modifications of the bilayer correlate with Aβ misfolding is unclear. Here, we studied peptide-lipid interactions in synthetic bilayers of the short-chain lipid dilauroyl phosphatidylcholine (DLPC) as a simplified model for diseased bilayers to determine their impact on Aβ aggregate, protofibril, and fibril formation. Aβ aggregation and fibril formation in membranes composed of dioleoyl phosphatidylcholine (DOPC) or 1- palmitoyl-2-oleoyl phosphatidylcholine mimicking normal bilayers served as controls. Differences in aggregate formation and stability were monitored by a combination of thioflavin-T fluorescence, circular dichroism, atomic force microscopy, transmission electron microscopy, and NMR. Despite the ability of all three lipid bilayers to catalyze aggregation, DLPC accelerates aggregation at much lower concentrations and prevents the fibrillation of Aβ at low micromolar concentrations. DLPC stabilized globular, membrane-associated oligomers, which could disrupt the bilayer integrity. DLPC bilayers also remodeled preformed amyloid fibrils into a pseudo-unfolded, molten globule state, which resembled on-pathway, protofibrillar aggregates. Whereas the stabilized, membrane-associated oligomers were found to be nontoxic, the remodeled species displayed toxicity similar to that of conventionally prepared aggregates. These results provide mechanistic insights into the roles that pathologically thin bilayers may play in Aβ aggregation on neuronal bilayers, and pathological lipid oxidation may contribute to Aβ misfolding.

Plasma Oxidized Polyhydroxymethylsiloxane—A New Smooth Surface for Supported Lipid Bilayer Formation

A novel substrate for preparation of supported lipid bilayers (SLBs), smooth at the subnanometer scale and of variable thickness from ten to several hundred nanometers, was developed by surface oxidation of spin-coated poly(hydroxymethylsiloxane) (PHMS) films. The deposited polymeric thin films were modified by a combination of oxygen plasma and thermal treatment (PHMS(ox)), in order to convert the outermost surface layer of the polymer film to a stable SiO(2) film, suitable for SLB formation. The hydrophilic, SiO(2)-like surfaces were characterized by XPS, wetting angle, ellipsometry, and AFM. Lipid bilayers were formed on this surface using the well-known vesicle adsorption-rupture-fusion process, usually performed on glass or vapor-deposited SiO(2). Reproducible formation of homogeneous SLBs of different compositions (POPC, DOEPC, and POPC/DOPS) was demonstrated on the new SiO(2) surface by quartz crystal microbalance with dissipation (QCM-D), surface plasmon resonance (SPR), and optical reflectometry measurements. The SLB formation kinetics on the PHMS(ox)-coated sensors showed very similar characteristics, for all investigated PHMS thicknesses, as on reference sensors coated with vapor-deposited SiO(2). The good adhesive properties of the PHMS to gold allows for the preparation of thin PHMS(ox) layers compatible with SPR. The much smaller roughness at the nanometer scale of the PHMS(ox) surfaces, compared to standard vapor-deposited SiO(2)-coated sensors, makes them advantageous for AFM and optical experiments and promising for patterning. To benefit optical experiments with the PHMS(ox) surfaces, it was also investigated how the PHMS film thickness influences the SPR and reflectometry responses upon SLB formation.

Gold and Silver Nanoparticles for Applications in Theranostics.

Noble metal nanomaterials, such as gold or silver nanoparticles, exhibit unique photonic, electronic, catalytic and therapeutic properties. The high versatility in their synthesis, especially size and shape features, as well as in the surface functionalization by, e.g., physisorption, direct chemisorption of thiol derivatives and covalent binding through bifunctional linkers or specific affinity interactions, prompted their widespread and rising use as multifunctional platforms for theranostic purposes. In this paper, the recent developments of gold and silver nanoparticles for application in biosensing, medical imaging, diagnosis and therapy is reviewed from the following five aspects: (1) the gold and silver nanomaterials intrinsic properties of biomedical interest; (2) the synthesis of noble metal nanoparticles by chemical, physical and biological/green processes; (3) the applications of gold and silver nanoparticles in imaging, diagnostic and therapeutic mode; (4) the surface functionalization processes for targeting, controlled drug loading and release, triggered pathways of cellular uptake and tissue distribution; and (5) nanotoxicity. The historical developments and the most recent applications have been focused on, together with suggested strategies for future more efficacious, targeted delivery.

Copper (II) ions modulate Angiogenin activity in human endothelial cells

Angiogenin (ANG), a member of the secreted ribonuclease family, is a potent angiogenesis stimulator that interacts with endothelial cells inducing a wide range of responses. Metal ions dyshomeostasis play a fundamental role in the onset of neurodegenerative diseases, in particular copper that is also involved in angiogenesis processes. It is known that vascular pathologies are present in neurodegenerative diseases and Angiogenin is down-regulated in Alzheimer and Parkinson diseases, as well as it has been found as one of the mutated genes in amyotrophic lateral sclerosis (ALS). Copper (II) induces an increase of Angiogenin binding to endothelial cells but, so far, the relationship between copper-ANG and angiogenesis induction remain unclear. Herein, the effects of copper (II) ions on Angiogenin activity and expression were evaluated. The binding of copper was demonstrated to affect the intracellular localization of the protein decreasing its nuclear translocation. Moreover, the ANG-copper (II) system negatively affects the protein-induced angiogenesis, as well as endothelial cells migration. Surprisingly, copper also reveals the ability to modulate the Angiogenin transcription. These results highlight the tight relationship between copper and Angiogenin, pointing out the biological relevance of ANG-copper system in the regulation of endothelial cell function, and revealing a possible new mechanism at the basis of vascular pathologies.

Ratiometric fluorescence sensing and cellular imaging of Cu2+ by a new water soluble trehalose-naphthalimide based chemosensor

A new turn-on Cu2+ fluorescent sensor (CST) having a trehalose moiety, which confers a relatively large solubility in water, has been synthesized. The chemosensor is therefore suitable for studies in aqueous solution. Full potentiometric and UV-vis characterization evidence that at physiological pH CST forms with Cu2+ a species with a 1:1 stoichiometry allowing for a straightforward correlation between CST response and copper(II) concentration. The presence of the trehalose unit does not negatively affect the selectivity of CST for Cu2+ over a series of metal ions of interest as proven by fluorescence measurements. The novel chemosensor, tested in differentiated neuroblastoma SH-SY5Y cells, is able to detect Cu2+ in the extracellular region, as well as to track copper transfer processes upon cell stimulation induced by cellular depolarization.

Modeling, design and synthesis of new heteroaryl ethylenes active against the MCF-7 breast cancer cell-line

A dataset of 50 compounds was used to generate a QSAR model and to design 9 new heteroaryl ethylenes. These compounds were synthesized, tested in vitro and a significant agreement with in silico predictions observed. Studies using Laser Scanning Confocal Microscopy pointed out that the compounds may act by different mechanisms.

Well-defined lipid interfaces for protein adsorption studies

The biomolecule-artificial lipid membrane interface has been investigated by QCM-D, SPR, and FRAP techniques, to study the adsorption process of ferritin on supported lipid bilayers (SLBs) of different composition and charge. Results point out to the predominant role of electrostatics in triggering the interaction of ferritin with SLBs.