Silvia Milani - Academia.edu (original) (raw)

Papers by Silvia Milani

Research paper thumbnail of Near-Infrared Spectroscopy Investigation of the Water Confined in Tricalcium Silicate Pastes

Journal of Physical Chemistry B, Aug 1, 2006

Near-infrared (NIR) spectroscopy has been employed to investigate the evolution of the vibrationa... more Near-infrared (NIR) spectroscopy has been employed to investigate the evolution of the vibrational spectrum of water entrapped in a tricalcium silicate paste. The overall free water, which decreases as a function of time due to the formation of the hydrated phases (portlandite, Ca(OH)(2), and hydrated calcium silicate, C-S-H) during the hydration reaction, is quantified by the decrease in the area of the NIR band at about 5000 cm(-1). The coexistence of two types of water in the hydrated phases (a "surface-interacting water" (type I) and a "bulklike water" (type II)) during the hydration is obtained by the analysis of the band at about 7000 cm(-1). The deconvolution of this band allows the quantification of the two water types. As the reaction advances, part of the "bulklike water" is converted to "surface-interacting water" in direct agreement with the C-S-H surface development. Finally, the Ca(OH)(2) formation can be concurrently monitored by NIR through the increase of a very sharp peak at 7083 cm(-1). Near-infrared spectroscopy allows determination in a very simple way of the most important features of the tricalcium silicate setting process.

Research paper thumbnail of Hofmeister effects in supramolecular and biological systems

Abstracts of Papers of The American Chemical Society, 2005

Specific ion effects, representative of near-universal Hofmeister phenomena, are illustrated in t... more Specific ion effects, representative of near-universal Hofmeister phenomena, are illustrated in three different systems. These are the formation of supramolecular assemblies from cyclodextrins, the optical rotation of L-serine, and the growth rate of two kinds of microorganisms (Staphylococcus aureus and Pseudomonas aeruginosa). The strong specific ion effects can be correlated with the anion polarizabilities and related physico-chemical parameters. The results show the relevance of dispersion (non-electrostatic) forces in these phenomena.

Research paper thumbnail of Interactions of Nucleolipids with Oligonucleotides

Liposomes as Therapeutic delivery Vehicles 4.1 Classification and Preparation of liposomes 4.2 Ca... more Liposomes as Therapeutic delivery Vehicles 4.1 Classification and Preparation of liposomes 4.2 Cationic Liposomes-DNA Complexes 4.3 Cytotoxicity issues applicable to lipoplexes in gene-therapy 4.4 Other Liposomes Delivery Systems for DNA transfer Anionic Liposomes Zwitterionic Liposomes Stabilized plasmid-lipid particles (SPLP) Bibliography Chapter 5 Hybrid Structures between Nucleolipid liposomes and Oligonucleotides 5.1 Effect of Buffer on Nucleolipids/Polynucleotides interaction TRIS Buffer TRIS/KCl Buffer Phosphate Buffer 5.2 Effect of Oligonucleotides length on POPA liposomes 5.3 A Cryo-TEM investigation on Oligonucleotides and Nucleolipids Mixtures in solution Bibliography Chapter 6 Complexes between Nucleolipid/liposomes and DNA 6.1 Structural and Spectroscopic investigation on Nucleolipids liposomes and ds-DNA 6.1.1 Circular Dichroism on 50dAdT double strand 6.1.2 Detecting ds-DNA with molecular probes 6.2 Nuclolipoplexes by Optical Microscopy Bibliography

Research paper thumbnail of Ternary CdS x Se 1 - x Deposited on Ag(111) by ECALE:  Synthesis and Characterization

Langmuir, 2005

Morphology and electronic properties of CdS, CdSe, and the ternary compounds of formula CdSxSe1-x... more Morphology and electronic properties of CdS, CdSe, and the ternary compounds of formula CdSxSe1-x deposited on Ag(111) by ECALE have been characterized as a function of the composition. The number of the attainable x values is limited by the necessity of using well-defined CdS/CdSe deposition sequences. However, the quantitative analysis carried out by XPS and electrochemical stripping experiments indicates that the ECALE method has a good control on composition. The AFM images together with the electrochemical characterization indicate both two-dimensional and three-dimensional growth contributions. The photospectra recorded at CdS film electrodes in liquid junction with an alkaline (poly)sulfide electrolyte show good efficiency of photoconversion and band gap typical of the single crystal. Lower photoconversion efficiency and the presence of subband gap response are observed for CdSe; a possible reason is some crystalline disorder due to lower control of the layer-by-layer deposition in the case of Se. The dependence of band gap on composition of ternary CdSxSe1-x ECALE films is monotonic and in agreement with literature data reported for bulk materials.

Research paper thumbnail of See Profile

Bilayers of palmitoyl-oleoylphosphatidylnucleoside derivatives (1-palmitoyl-2-oleoyl-phosphatidyl... more Bilayers of palmitoyl-oleoylphosphatidylnucleoside derivatives (1-palmitoyl-2-oleoyl-phosphatidyl-adenosine and 1-palmitoyl-2-oleoyl-phosphatidyl-uridine) were synthesized and investigated in the low-water content regime by a combination of neutron diffraction and Fourier transform infrared linear dichroism (LD-FTIR). Attention was focused on the modulation of structural properties operated by the presence of nucleic acid bases (either adenosine or uridine, a purine and a pyrimidine that are complementary in RNA). Base substitution causes major differences in phase behavior of the phospholipids, i.e., water sorption from a controlled humidity atmosphere and smectic periodicity. The profile of scattering length density can be inferred from five diffraction orders for 1-palmitoyl-2-oleoyl-phosphatidyl-uridine lamellar phase. 1-Palmitoyl-2-oleoyl-phosphatidyl-adenosine is characterized by lower and less ready hydration, giving rise to a powder-like sample. A linear dichroism FTIR inves...

Research paper thumbnail of Refining in vitro models for nanomaterial exposure to cells and tissues

NanoImpact, 2018

With the increasing use of nanomaterials (NMs) in a variety of commercial and medical application... more With the increasing use of nanomaterials (NMs) in a variety of commercial and medical applications, there is a parallel increase in concern related to unintentional exposure. This leads to a pressing need for appropriate hazard and risk assessment, and subsequent regulation of these new and emerging nanosubstances. Typically, in vitro models are the first point for assessment, and these are often then used to begin to predict and translate the potential effects in vivo. The area of nanotoxicology is therefore critically important, and requires that experimental protocols are clear, defined and standardized within adequate risk assessment frameworks to allow hazard identification and extrapolation to more realistic in

Research paper thumbnail of COLL 141-Nucleolipoplexes: A new paradigm for phospholipid bilayer-nucleic acid interactions

Abstracts of Papers of the American Chemical Society, 2007

Research paper thumbnail of Biocompatible cationic lipids for the formulation of liposomal DNA vectors

Soft Matter, 2014

Liposomes containing ethylphosphocholine lipids for DNA delivery: phase behavior and interaction ... more Liposomes containing ethylphosphocholine lipids for DNA delivery: phase behavior and interaction with model membranes.

Research paper thumbnail of Collective headgroup conformational transition in twisted micellar superstructures

Soft Matter, 2008

Predictions on amphiphilic self-assemblies traditionally rely on considerations on molecular shap... more Predictions on amphiphilic self-assemblies traditionally rely on considerations on molecular shape and charge of the surfactant. In the case of functional surfactants a more sophisticated toolbox becomes necessary to design amphiphiles encoding chemical functionalities that provide additional responsive properties to their self-assemblies. Here we report on a comprehensive and combined structural–spectroscopic characterization of 1, 2-dilauroyl-phosphatidyl-adenosine (DLPA) micelles in phosphate buffer. The temperature ...

Research paper thumbnail of Nucleolipoplexes:  A New Paradigm for Phospholipid Bilayer−Nucleic Acid Interactions

Journal of the American Chemical Society, 2007

Supporting Information Materials: 1-Palmitoyl-2-oleoyl-sn-Glycero-3-Phosphocholine (POPC) was pur... more Supporting Information Materials: 1-Palmitoyl-2-oleoyl-sn-Glycero-3-Phosphocholine (POPC) was purchased from Avanti Polar Lipids (Alabaster, Alabama, USA) and its purity checked by TLC. The lecithin was used as received since no oxidation or lyso products could be detected. Adenosine, HCl, CHCl3, MeOH, and NH3 (33% aqueous solution) used in the synthesis were purchased from Fluka (Switzerland). Phospholipase D from Streptomyces sp AA586 was a generous gift from Asahi Chemical Industry Co., Ltd (Tokyo, Japan). Tris buffer and polyUridylic acid potassium salt were purchased from Sigma-Aldrich. POPA was synthesized starting from the corresponding phosphatidylcholine in a two-phase system according to a modification of the method proposed by Shuto and coworkers, and obtained as an ammonium salt. Separation from the by-products was achieved by silicagel flash chromatography. Purity was checked by TLC,

Research paper thumbnail of Nucleolipid membranes: structure and molecular recognition

Journal of Physics: Condensed Matter, 2008

Nucleolipid bilayers have been investigated through neutron diffraction, DSC and FTIR techniques.... more Nucleolipid bilayers have been investigated through neutron diffraction, DSC and FTIR techniques. Two nucleolipids, bearing complementary RNA bases, have been chosen to highlight in their mixtures non-ideal behaviors ascribable to attractive interactions of the same selectivity and stoichiometry as in nucleic acids.

Research paper thumbnail of Complexes of nucleolipid liposomes with single-stranded and double-stranded nucleic acids

Journal of Colloid and Interface Science, 2012

We report on the association of anionic liposomes from POP-Ade:POPC (1-palmitoyl-2-oleoyl-phospha... more We report on the association of anionic liposomes from POP-Ade:POPC (1-palmitoyl-2-oleoyl-phosphatidyladenosine and 1-palmitoyl-2-oleoyl-phosphatidylcholine, respectively) with single- and double-strand nucleic acids, mediated by Ca(2+) bridging. The structural and dynamical features of such complexes are compared with those displayed when the nucleolipid is replaced by POPG (1-palmitoyl-2-oleoyl-sn-phosphatidyl-glycerol), characterized by the same apolar skeleton and negative charge as POP-Ade, but lacking the nucleic polar head. For single-stranded nucleic acids, we demonstrate that specific interactions drive the formation of complexes with nucleolipid liposomes, while no association is present for POPG-based samples. For double-stranded nucleic acids, Ca(2+) bridging promotes association with both liposomal formulations, but the corresponding complexes have different structural features, in terms of size, overall charge and internal liquid-crystalline structure.

Research paper thumbnail of Association of polynucleotides with nucleolipid bilayers driven by molecular recognition

Journal of Colloid and Interface Science, 2011

This contribution reports on the interaction of ss-polynucleotides of various length and sequence... more This contribution reports on the interaction of ss-polynucleotides of various length and sequence with liposomal dispersions of anionic lipids. No appreciable structural and morphological variations were detected for POPG (1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-glycerol) liposomes, as expected from the high negative charge density both of liposomal surface and of the poly or oligonucleotide. Conversely, when similarly charged POPN nucleolipids (1-palmitoyl-2-oleoylphosphatidyl-nucleosides) were used, meaningful differences could be observed both on size and morphology of the mixed aggregates. The comparison with POPG/nucleic acids mixed systems points to the conclusion that the driving force for association of nucleolipid liposomes with nucleic acids can be ascribed to selective interactions at the polar head level which overcome electrostatic repulsion. Dynamic light scattering, Cryo-TEM and circular dichroism provided an ensemble of results where an interesting dependence on the polynucleotide base nature and contour length emerges. The extent of interaction can be modulated, in terms of size of the complexes, by choice of background buffer, ionic strength and polynucleotide length.

Research paper thumbnail of Comparison of four different particle sizing methods for siRNA polyplex characterization

European Journal of Pharmaceutics and Biopharmaceutics, 2013

The ability to reliably determine the size of siRNA polyplexes is the key for the rational design... more The ability to reliably determine the size of siRNA polyplexes is the key for the rational design of particles and their formulation, as well as, their safe application in vivo. At the moment, no standard technique for size measurements is available. Each method has different underlying principles and hence may give different results. Here, four different analytical methods were evaluated for their suitability to analyze the characteristics of homogeneous and heterogeneous siRNA polyplexes: dynamic light scattering (DLS), atomic force microscopy (AFM), nanoparticle trafficking analysis (NTA), and fluorescence correlation spectroscopy (FCS). Three different siRNA polyplex compositions generated with different, precise, and hydrophobically modified oligoaminoamides were used in this study. All of the evaluated methods were suitable for analysis of medium sized, homogeneous siRNA polyplexes ($120 nm). Small particles (<40 nm) could not be tracked with NTA, but with the other three methods. Heterogeneous polyplexes were generally difficult to analyze. Only by visualization with AFM, the heterogeneity of those polyplexes was observable. FCS was the only method suitable for measuring polyplex stability in 90% fetal bovine serum. Physico-chemical characteristics of polyplexes are important quality criterions for successful in vivo application and future formulation development. Therefore, a comprehensive analysis by more than one method is of particular importance.

Research paper thumbnail of Specific anion effects on the optical rotation of glucoseand serine

Biopolymers, 2006

Optical activity is directly related to molecular conformation through the anisotropic polarizabi... more Optical activity is directly related to molecular conformation through the anisotropic polarizabilities of molecules and the refractive index of materials. L-amino acids and D-sugars are characteristic essential bioactive molecules. Since molecular recognition and enzyme activity are related to the conformation of substrates, the relevance of optical activity to biological processes is evident. Specific ion, or Hofmeister, effects that occur with electrolytes at moderately high concentrations modify the behavior of interfaces, molecular forces between membranes, of bulk solutions, of enzymes, and even of DNA. Such effects are universal. Here we report a study on the change in optical rotation induced by some sodium salts for the enantiomers of serine and glucose in water solution. The optical rotation is shown to depend on the kind of anion and on the salt concentration. To obtain further insights into the mechanism behind the phenomenon, Fourier transform infrared (FTIR) spectral studies of serine and glucose solutions in electrolytes were also carried out. The results suggest that it is the differences in interactions of anions at specific chemical sites of the solutes that are responsible for the effects. These forces depend strongly on anion polarizability in water. Such specific ion preferential interactions can affect conformation and internal field, and result in significant changes in optical rotation.

Research paper thumbnail of Structural Investigation of Bilayers Formed by 1-Palmitoyl-2-Oleoylphosphatidylnucleosides

Biophysical Journal, 2006

Bilayers of palmitoyl-oleoylphosphatidylnucleoside derivatives (1-palmitoyl-2-oleoyl-phosphatidyl... more Bilayers of palmitoyl-oleoylphosphatidylnucleoside derivatives (1-palmitoyl-2-oleoyl-phosphatidyl-adenosine and 1-palmitoyl-2-oleoyl-phosphatidyl-uridine) were synthesized and investigated in the low-water content regime by a combination of neutron diffraction and Fourier transform infrared linear dichroism (LD-FTIR). Attention was focused on the modulation of structural properties operated by the presence of nucleic acid bases (either adenosine or uridine, a purine and a pyrimidine that are complementary in RNA). Base substitution causes major differences in phase behavior of the phospholipids, i.e., water sorption from a controlled humidity atmosphere and smectic periodicity. The profile of scattering length density can be inferred from five diffraction orders for 1-palmitoyl-2-oleoyl-phosphatidyl-uridine lamellar phase. 1-Palmitoyl-2-oleoyl-phosphatidyladenosine is characterized by lower and less ready hydration, giving rise to a powder-like sample. A linear dichroism FTIR investigation on the same lamellar phases was undertaken with the purpose of gathering details at the submolecular level on different portions of the molecule. 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayers were also investigated with the same technique for the sake of comparison. Besides a confirmation of the diffraction data interpretation, FTIR has provided evidence that the same chemical groups at the bilayer interface (namely the sugar-phosphate) have a different orientation depending on whether the base is a purine or a pyrimidine. A very simple geometrical optimization agrees with this observation. This indicates that a different pattern of base interaction is operating in the two cases and that base substitution acts as a modulator of the phase properties.

Research paper thumbnail of Hofmeister effects in supramolecular and biological systems

Biophysical Chemistry, 2006

Specific ion effects, representative of near-universal Hofmeister phenomena, are illustrated in t... more Specific ion effects, representative of near-universal Hofmeister phenomena, are illustrated in three different systems. These are the formation of supramolecular assemblies from cyclodextrins, the optical rotation of L-serine, and the growth rate of two kinds of microorganisms (Staphylococcus aureus and Pseudomonas aeruginosa). The strong specific ion effects can be correlated with the anion polarizabilities and related physico-chemical parameters. The results show the relevance of dispersion (non-electrostatic) forces in these phenomena.

Research paper thumbnail of Reversible versus Irreversible Binding of Transferrin to Polystyrene Nanoparticles: Soft and Hard Corona

ACS Nano, 2012

Protein adsorption to nanoparticles (NPs) is a key prerequisite to understand NPÀcell interaction... more Protein adsorption to nanoparticles (NPs) is a key prerequisite to understand NPÀcell interactions. While the layer thickness of the protein corona has been well characterized in many cases, the absolute number of bound proteins and their exchange dynamics in body fluids is difficult to assess. Here we measure the number of molecules adsorbed to sulfonate (PSOSO 3 H) and carboxyl-(PSCOOH) polystyrene NPs using fluorescence correlation spectroscopy. We find that the fraction of molecules bound to NPs falls onto a single, universal adsorption curve, if plotted as a function of molar protein-to-NP ratio. The adsorption curve shows the build-up of a strongly bound monolayer up to the point of monolayer saturation (at a geometrically defined protein-to-NP ratio), beyond which a secondary, weakly bound layer is formed. While the first layer is irreversibly bound (hard corona), the secondary layer (soft corona) exhibits dynamic exchange, if competing unlabeled is added. In the presence of plasma proteins, the hard corona is stable, while the soft corona is almost completely removed. The existence of two distinct time scales in the protein off-kinetics, for both NP types studied here, indicates the possibility of an exposure memory effect in the NP corona.

Research paper thumbnail of Improving Quality in Nanoparticle-Induced Cytotoxicity Testing by a Tiered Inter-Laboratory Comparison Study

Nanomaterials, 2020

The quality and relevance of nanosafety studies constitute major challenges to ensure their key r... more The quality and relevance of nanosafety studies constitute major challenges to ensure their key role as a supporting tool in sustainable innovation, and subsequent competitive economic advantage. However, the number of apparently contradictory and inconclusive research results has increased in the past few years, indicating the need to introduce harmonized protocols and good practices in the nanosafety research community. Therefore, we aimed to evaluate if best-practice training and inter-laboratory comparison (ILC) of performance of the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay for the cytotoxicity assessment of nanomaterials among 15 European laboratories can improve quality in nanosafety testing. We used two well-described model nanoparticles, 40-nm carboxylated polystyrene (PS-COOH) and 50-nm amino-modified polystyrene (PS-NH2). We followed a tiered approach using well-developed standard operating procedures (SOPs) and s...

Research paper thumbnail of Intercalation of Single-Strand Oligonucleotides between Nucleolipid Anionic Membranes: A Neutron Diffraction Study †

Langmuir, 2009

This contribution presents a neutron diffraction investigation of anionic lamellar phases compose... more This contribution presents a neutron diffraction investigation of anionic lamellar phases composed of mixtures of 1-palmitoyl, 2-oleoyl phosphatidyl-nucleosides (POPN, where N is either adenosine or uridine), and POPC (1-palmitoyl,2-oleoyl-phosphatidyl-choline). Their behavior is studied for two different mole ratios and in the presence of nucleic acids. The samples are formed by the evaporation of liposomal dispersions prepared in water or in solutions containing single-strand oligonucleotides. Previous small angle X-ray scattering (SAXS) experiments on the system POPA/polyU (polyuridylic acid, high degree of polymerization, synthetic ribonucleic acid) proved that the insertion and ordering of the biopolymer in the phospholipid lamellae were driven by molecular recognition. In the present study, we extend the previous investigation to single-strand monodisperse oligonucleotides (50-mers). Structural details of the membranes were obtained from the analysis of the neutron diffraction scattering length density profiles. The evidence of direct and specific interactions, driven by molecular recognition between the nucleic polar heads of the nucleolipid and the single-strand nucleic acid, is strengthened by the comparison with identically charged bilayers formed by POPG/POPC. These results contribute to the understanding of the parameters governing the interactions between nucleolipid membranes and oligonucleotides, providing a novel strategy for the design of lipid-based vehicles for nucleic acids.

Research paper thumbnail of Near-Infrared Spectroscopy Investigation of the Water Confined in Tricalcium Silicate Pastes

Journal of Physical Chemistry B, Aug 1, 2006

Near-infrared (NIR) spectroscopy has been employed to investigate the evolution of the vibrationa... more Near-infrared (NIR) spectroscopy has been employed to investigate the evolution of the vibrational spectrum of water entrapped in a tricalcium silicate paste. The overall free water, which decreases as a function of time due to the formation of the hydrated phases (portlandite, Ca(OH)(2), and hydrated calcium silicate, C-S-H) during the hydration reaction, is quantified by the decrease in the area of the NIR band at about 5000 cm(-1). The coexistence of two types of water in the hydrated phases (a &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;surface-interacting water&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; (type I) and a &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;bulklike water&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; (type II)) during the hydration is obtained by the analysis of the band at about 7000 cm(-1). The deconvolution of this band allows the quantification of the two water types. As the reaction advances, part of the &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;bulklike water&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; is converted to &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;surface-interacting water&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; in direct agreement with the C-S-H surface development. Finally, the Ca(OH)(2) formation can be concurrently monitored by NIR through the increase of a very sharp peak at 7083 cm(-1). Near-infrared spectroscopy allows determination in a very simple way of the most important features of the tricalcium silicate setting process.

Research paper thumbnail of Hofmeister effects in supramolecular and biological systems

Abstracts of Papers of The American Chemical Society, 2005

Specific ion effects, representative of near-universal Hofmeister phenomena, are illustrated in t... more Specific ion effects, representative of near-universal Hofmeister phenomena, are illustrated in three different systems. These are the formation of supramolecular assemblies from cyclodextrins, the optical rotation of L-serine, and the growth rate of two kinds of microorganisms (Staphylococcus aureus and Pseudomonas aeruginosa). The strong specific ion effects can be correlated with the anion polarizabilities and related physico-chemical parameters. The results show the relevance of dispersion (non-electrostatic) forces in these phenomena.

Research paper thumbnail of Interactions of Nucleolipids with Oligonucleotides

Liposomes as Therapeutic delivery Vehicles 4.1 Classification and Preparation of liposomes 4.2 Ca... more Liposomes as Therapeutic delivery Vehicles 4.1 Classification and Preparation of liposomes 4.2 Cationic Liposomes-DNA Complexes 4.3 Cytotoxicity issues applicable to lipoplexes in gene-therapy 4.4 Other Liposomes Delivery Systems for DNA transfer Anionic Liposomes Zwitterionic Liposomes Stabilized plasmid-lipid particles (SPLP) Bibliography Chapter 5 Hybrid Structures between Nucleolipid liposomes and Oligonucleotides 5.1 Effect of Buffer on Nucleolipids/Polynucleotides interaction TRIS Buffer TRIS/KCl Buffer Phosphate Buffer 5.2 Effect of Oligonucleotides length on POPA liposomes 5.3 A Cryo-TEM investigation on Oligonucleotides and Nucleolipids Mixtures in solution Bibliography Chapter 6 Complexes between Nucleolipid/liposomes and DNA 6.1 Structural and Spectroscopic investigation on Nucleolipids liposomes and ds-DNA 6.1.1 Circular Dichroism on 50dAdT double strand 6.1.2 Detecting ds-DNA with molecular probes 6.2 Nuclolipoplexes by Optical Microscopy Bibliography

Research paper thumbnail of Ternary CdS x Se 1 - x Deposited on Ag(111) by ECALE:  Synthesis and Characterization

Langmuir, 2005

Morphology and electronic properties of CdS, CdSe, and the ternary compounds of formula CdSxSe1-x... more Morphology and electronic properties of CdS, CdSe, and the ternary compounds of formula CdSxSe1-x deposited on Ag(111) by ECALE have been characterized as a function of the composition. The number of the attainable x values is limited by the necessity of using well-defined CdS/CdSe deposition sequences. However, the quantitative analysis carried out by XPS and electrochemical stripping experiments indicates that the ECALE method has a good control on composition. The AFM images together with the electrochemical characterization indicate both two-dimensional and three-dimensional growth contributions. The photospectra recorded at CdS film electrodes in liquid junction with an alkaline (poly)sulfide electrolyte show good efficiency of photoconversion and band gap typical of the single crystal. Lower photoconversion efficiency and the presence of subband gap response are observed for CdSe; a possible reason is some crystalline disorder due to lower control of the layer-by-layer deposition in the case of Se. The dependence of band gap on composition of ternary CdSxSe1-x ECALE films is monotonic and in agreement with literature data reported for bulk materials.

Research paper thumbnail of See Profile

Bilayers of palmitoyl-oleoylphosphatidylnucleoside derivatives (1-palmitoyl-2-oleoyl-phosphatidyl... more Bilayers of palmitoyl-oleoylphosphatidylnucleoside derivatives (1-palmitoyl-2-oleoyl-phosphatidyl-adenosine and 1-palmitoyl-2-oleoyl-phosphatidyl-uridine) were synthesized and investigated in the low-water content regime by a combination of neutron diffraction and Fourier transform infrared linear dichroism (LD-FTIR). Attention was focused on the modulation of structural properties operated by the presence of nucleic acid bases (either adenosine or uridine, a purine and a pyrimidine that are complementary in RNA). Base substitution causes major differences in phase behavior of the phospholipids, i.e., water sorption from a controlled humidity atmosphere and smectic periodicity. The profile of scattering length density can be inferred from five diffraction orders for 1-palmitoyl-2-oleoyl-phosphatidyl-uridine lamellar phase. 1-Palmitoyl-2-oleoyl-phosphatidyl-adenosine is characterized by lower and less ready hydration, giving rise to a powder-like sample. A linear dichroism FTIR inves...

Research paper thumbnail of Refining in vitro models for nanomaterial exposure to cells and tissues

NanoImpact, 2018

With the increasing use of nanomaterials (NMs) in a variety of commercial and medical application... more With the increasing use of nanomaterials (NMs) in a variety of commercial and medical applications, there is a parallel increase in concern related to unintentional exposure. This leads to a pressing need for appropriate hazard and risk assessment, and subsequent regulation of these new and emerging nanosubstances. Typically, in vitro models are the first point for assessment, and these are often then used to begin to predict and translate the potential effects in vivo. The area of nanotoxicology is therefore critically important, and requires that experimental protocols are clear, defined and standardized within adequate risk assessment frameworks to allow hazard identification and extrapolation to more realistic in

Research paper thumbnail of COLL 141-Nucleolipoplexes: A new paradigm for phospholipid bilayer-nucleic acid interactions

Abstracts of Papers of the American Chemical Society, 2007

Research paper thumbnail of Biocompatible cationic lipids for the formulation of liposomal DNA vectors

Soft Matter, 2014

Liposomes containing ethylphosphocholine lipids for DNA delivery: phase behavior and interaction ... more Liposomes containing ethylphosphocholine lipids for DNA delivery: phase behavior and interaction with model membranes.

Research paper thumbnail of Collective headgroup conformational transition in twisted micellar superstructures

Soft Matter, 2008

Predictions on amphiphilic self-assemblies traditionally rely on considerations on molecular shap... more Predictions on amphiphilic self-assemblies traditionally rely on considerations on molecular shape and charge of the surfactant. In the case of functional surfactants a more sophisticated toolbox becomes necessary to design amphiphiles encoding chemical functionalities that provide additional responsive properties to their self-assemblies. Here we report on a comprehensive and combined structural–spectroscopic characterization of 1, 2-dilauroyl-phosphatidyl-adenosine (DLPA) micelles in phosphate buffer. The temperature ...

Research paper thumbnail of Nucleolipoplexes:  A New Paradigm for Phospholipid Bilayer−Nucleic Acid Interactions

Journal of the American Chemical Society, 2007

Supporting Information Materials: 1-Palmitoyl-2-oleoyl-sn-Glycero-3-Phosphocholine (POPC) was pur... more Supporting Information Materials: 1-Palmitoyl-2-oleoyl-sn-Glycero-3-Phosphocholine (POPC) was purchased from Avanti Polar Lipids (Alabaster, Alabama, USA) and its purity checked by TLC. The lecithin was used as received since no oxidation or lyso products could be detected. Adenosine, HCl, CHCl3, MeOH, and NH3 (33% aqueous solution) used in the synthesis were purchased from Fluka (Switzerland). Phospholipase D from Streptomyces sp AA586 was a generous gift from Asahi Chemical Industry Co., Ltd (Tokyo, Japan). Tris buffer and polyUridylic acid potassium salt were purchased from Sigma-Aldrich. POPA was synthesized starting from the corresponding phosphatidylcholine in a two-phase system according to a modification of the method proposed by Shuto and coworkers, and obtained as an ammonium salt. Separation from the by-products was achieved by silicagel flash chromatography. Purity was checked by TLC,

Research paper thumbnail of Nucleolipid membranes: structure and molecular recognition

Journal of Physics: Condensed Matter, 2008

Nucleolipid bilayers have been investigated through neutron diffraction, DSC and FTIR techniques.... more Nucleolipid bilayers have been investigated through neutron diffraction, DSC and FTIR techniques. Two nucleolipids, bearing complementary RNA bases, have been chosen to highlight in their mixtures non-ideal behaviors ascribable to attractive interactions of the same selectivity and stoichiometry as in nucleic acids.

Research paper thumbnail of Complexes of nucleolipid liposomes with single-stranded and double-stranded nucleic acids

Journal of Colloid and Interface Science, 2012

We report on the association of anionic liposomes from POP-Ade:POPC (1-palmitoyl-2-oleoyl-phospha... more We report on the association of anionic liposomes from POP-Ade:POPC (1-palmitoyl-2-oleoyl-phosphatidyladenosine and 1-palmitoyl-2-oleoyl-phosphatidylcholine, respectively) with single- and double-strand nucleic acids, mediated by Ca(2+) bridging. The structural and dynamical features of such complexes are compared with those displayed when the nucleolipid is replaced by POPG (1-palmitoyl-2-oleoyl-sn-phosphatidyl-glycerol), characterized by the same apolar skeleton and negative charge as POP-Ade, but lacking the nucleic polar head. For single-stranded nucleic acids, we demonstrate that specific interactions drive the formation of complexes with nucleolipid liposomes, while no association is present for POPG-based samples. For double-stranded nucleic acids, Ca(2+) bridging promotes association with both liposomal formulations, but the corresponding complexes have different structural features, in terms of size, overall charge and internal liquid-crystalline structure.

Research paper thumbnail of Association of polynucleotides with nucleolipid bilayers driven by molecular recognition

Journal of Colloid and Interface Science, 2011

This contribution reports on the interaction of ss-polynucleotides of various length and sequence... more This contribution reports on the interaction of ss-polynucleotides of various length and sequence with liposomal dispersions of anionic lipids. No appreciable structural and morphological variations were detected for POPG (1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-glycerol) liposomes, as expected from the high negative charge density both of liposomal surface and of the poly or oligonucleotide. Conversely, when similarly charged POPN nucleolipids (1-palmitoyl-2-oleoylphosphatidyl-nucleosides) were used, meaningful differences could be observed both on size and morphology of the mixed aggregates. The comparison with POPG/nucleic acids mixed systems points to the conclusion that the driving force for association of nucleolipid liposomes with nucleic acids can be ascribed to selective interactions at the polar head level which overcome electrostatic repulsion. Dynamic light scattering, Cryo-TEM and circular dichroism provided an ensemble of results where an interesting dependence on the polynucleotide base nature and contour length emerges. The extent of interaction can be modulated, in terms of size of the complexes, by choice of background buffer, ionic strength and polynucleotide length.

Research paper thumbnail of Comparison of four different particle sizing methods for siRNA polyplex characterization

European Journal of Pharmaceutics and Biopharmaceutics, 2013

The ability to reliably determine the size of siRNA polyplexes is the key for the rational design... more The ability to reliably determine the size of siRNA polyplexes is the key for the rational design of particles and their formulation, as well as, their safe application in vivo. At the moment, no standard technique for size measurements is available. Each method has different underlying principles and hence may give different results. Here, four different analytical methods were evaluated for their suitability to analyze the characteristics of homogeneous and heterogeneous siRNA polyplexes: dynamic light scattering (DLS), atomic force microscopy (AFM), nanoparticle trafficking analysis (NTA), and fluorescence correlation spectroscopy (FCS). Three different siRNA polyplex compositions generated with different, precise, and hydrophobically modified oligoaminoamides were used in this study. All of the evaluated methods were suitable for analysis of medium sized, homogeneous siRNA polyplexes ($120 nm). Small particles (<40 nm) could not be tracked with NTA, but with the other three methods. Heterogeneous polyplexes were generally difficult to analyze. Only by visualization with AFM, the heterogeneity of those polyplexes was observable. FCS was the only method suitable for measuring polyplex stability in 90% fetal bovine serum. Physico-chemical characteristics of polyplexes are important quality criterions for successful in vivo application and future formulation development. Therefore, a comprehensive analysis by more than one method is of particular importance.

Research paper thumbnail of Specific anion effects on the optical rotation of glucoseand serine

Biopolymers, 2006

Optical activity is directly related to molecular conformation through the anisotropic polarizabi... more Optical activity is directly related to molecular conformation through the anisotropic polarizabilities of molecules and the refractive index of materials. L-amino acids and D-sugars are characteristic essential bioactive molecules. Since molecular recognition and enzyme activity are related to the conformation of substrates, the relevance of optical activity to biological processes is evident. Specific ion, or Hofmeister, effects that occur with electrolytes at moderately high concentrations modify the behavior of interfaces, molecular forces between membranes, of bulk solutions, of enzymes, and even of DNA. Such effects are universal. Here we report a study on the change in optical rotation induced by some sodium salts for the enantiomers of serine and glucose in water solution. The optical rotation is shown to depend on the kind of anion and on the salt concentration. To obtain further insights into the mechanism behind the phenomenon, Fourier transform infrared (FTIR) spectral studies of serine and glucose solutions in electrolytes were also carried out. The results suggest that it is the differences in interactions of anions at specific chemical sites of the solutes that are responsible for the effects. These forces depend strongly on anion polarizability in water. Such specific ion preferential interactions can affect conformation and internal field, and result in significant changes in optical rotation.

Research paper thumbnail of Structural Investigation of Bilayers Formed by 1-Palmitoyl-2-Oleoylphosphatidylnucleosides

Biophysical Journal, 2006

Bilayers of palmitoyl-oleoylphosphatidylnucleoside derivatives (1-palmitoyl-2-oleoyl-phosphatidyl... more Bilayers of palmitoyl-oleoylphosphatidylnucleoside derivatives (1-palmitoyl-2-oleoyl-phosphatidyl-adenosine and 1-palmitoyl-2-oleoyl-phosphatidyl-uridine) were synthesized and investigated in the low-water content regime by a combination of neutron diffraction and Fourier transform infrared linear dichroism (LD-FTIR). Attention was focused on the modulation of structural properties operated by the presence of nucleic acid bases (either adenosine or uridine, a purine and a pyrimidine that are complementary in RNA). Base substitution causes major differences in phase behavior of the phospholipids, i.e., water sorption from a controlled humidity atmosphere and smectic periodicity. The profile of scattering length density can be inferred from five diffraction orders for 1-palmitoyl-2-oleoyl-phosphatidyl-uridine lamellar phase. 1-Palmitoyl-2-oleoyl-phosphatidyladenosine is characterized by lower and less ready hydration, giving rise to a powder-like sample. A linear dichroism FTIR investigation on the same lamellar phases was undertaken with the purpose of gathering details at the submolecular level on different portions of the molecule. 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayers were also investigated with the same technique for the sake of comparison. Besides a confirmation of the diffraction data interpretation, FTIR has provided evidence that the same chemical groups at the bilayer interface (namely the sugar-phosphate) have a different orientation depending on whether the base is a purine or a pyrimidine. A very simple geometrical optimization agrees with this observation. This indicates that a different pattern of base interaction is operating in the two cases and that base substitution acts as a modulator of the phase properties.

Research paper thumbnail of Hofmeister effects in supramolecular and biological systems

Biophysical Chemistry, 2006

Specific ion effects, representative of near-universal Hofmeister phenomena, are illustrated in t... more Specific ion effects, representative of near-universal Hofmeister phenomena, are illustrated in three different systems. These are the formation of supramolecular assemblies from cyclodextrins, the optical rotation of L-serine, and the growth rate of two kinds of microorganisms (Staphylococcus aureus and Pseudomonas aeruginosa). The strong specific ion effects can be correlated with the anion polarizabilities and related physico-chemical parameters. The results show the relevance of dispersion (non-electrostatic) forces in these phenomena.

Research paper thumbnail of Reversible versus Irreversible Binding of Transferrin to Polystyrene Nanoparticles: Soft and Hard Corona

ACS Nano, 2012

Protein adsorption to nanoparticles (NPs) is a key prerequisite to understand NPÀcell interaction... more Protein adsorption to nanoparticles (NPs) is a key prerequisite to understand NPÀcell interactions. While the layer thickness of the protein corona has been well characterized in many cases, the absolute number of bound proteins and their exchange dynamics in body fluids is difficult to assess. Here we measure the number of molecules adsorbed to sulfonate (PSOSO 3 H) and carboxyl-(PSCOOH) polystyrene NPs using fluorescence correlation spectroscopy. We find that the fraction of molecules bound to NPs falls onto a single, universal adsorption curve, if plotted as a function of molar protein-to-NP ratio. The adsorption curve shows the build-up of a strongly bound monolayer up to the point of monolayer saturation (at a geometrically defined protein-to-NP ratio), beyond which a secondary, weakly bound layer is formed. While the first layer is irreversibly bound (hard corona), the secondary layer (soft corona) exhibits dynamic exchange, if competing unlabeled is added. In the presence of plasma proteins, the hard corona is stable, while the soft corona is almost completely removed. The existence of two distinct time scales in the protein off-kinetics, for both NP types studied here, indicates the possibility of an exposure memory effect in the NP corona.

Research paper thumbnail of Improving Quality in Nanoparticle-Induced Cytotoxicity Testing by a Tiered Inter-Laboratory Comparison Study

Nanomaterials, 2020

The quality and relevance of nanosafety studies constitute major challenges to ensure their key r... more The quality and relevance of nanosafety studies constitute major challenges to ensure their key role as a supporting tool in sustainable innovation, and subsequent competitive economic advantage. However, the number of apparently contradictory and inconclusive research results has increased in the past few years, indicating the need to introduce harmonized protocols and good practices in the nanosafety research community. Therefore, we aimed to evaluate if best-practice training and inter-laboratory comparison (ILC) of performance of the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay for the cytotoxicity assessment of nanomaterials among 15 European laboratories can improve quality in nanosafety testing. We used two well-described model nanoparticles, 40-nm carboxylated polystyrene (PS-COOH) and 50-nm amino-modified polystyrene (PS-NH2). We followed a tiered approach using well-developed standard operating procedures (SOPs) and s...

Research paper thumbnail of Intercalation of Single-Strand Oligonucleotides between Nucleolipid Anionic Membranes: A Neutron Diffraction Study †

Langmuir, 2009

This contribution presents a neutron diffraction investigation of anionic lamellar phases compose... more This contribution presents a neutron diffraction investigation of anionic lamellar phases composed of mixtures of 1-palmitoyl, 2-oleoyl phosphatidyl-nucleosides (POPN, where N is either adenosine or uridine), and POPC (1-palmitoyl,2-oleoyl-phosphatidyl-choline). Their behavior is studied for two different mole ratios and in the presence of nucleic acids. The samples are formed by the evaporation of liposomal dispersions prepared in water or in solutions containing single-strand oligonucleotides. Previous small angle X-ray scattering (SAXS) experiments on the system POPA/polyU (polyuridylic acid, high degree of polymerization, synthetic ribonucleic acid) proved that the insertion and ordering of the biopolymer in the phospholipid lamellae were driven by molecular recognition. In the present study, we extend the previous investigation to single-strand monodisperse oligonucleotides (50-mers). Structural details of the membranes were obtained from the analysis of the neutron diffraction scattering length density profiles. The evidence of direct and specific interactions, driven by molecular recognition between the nucleic polar heads of the nucleolipid and the single-strand nucleic acid, is strengthened by the comparison with identically charged bilayers formed by POPG/POPC. These results contribute to the understanding of the parameters governing the interactions between nucleolipid membranes and oligonucleotides, providing a novel strategy for the design of lipid-based vehicles for nucleic acids.