Light Scattering as Spectroscopic Tool for the Study of Disperse Systems Useful in Pharmaceutical Sciences

Dopamine-Coated Carbon Nanodots: A Supramolecular Approach to Polydopamine Composite

The development of biocompatible composites constituted by polydopamine and fluorescent carbon dots represents a promising way of exploiting the extraordinary adhesive properties of polydopamine for multi-purpose technologies. Here, a supramolecular complex is realized by the assembly of dopamine on the carbon dots surface, and the optical and structural properties are investigated by means of different spectroscopic techniques, from time-resolved fluorescence to Raman and NMR spectroscopies. The results suggest that the catechol unit of dopamine plays the main role in the formation of the supramolecular complex, in which carbon nanodot fluorescence emission is quenched by a photoinduced electron transfer process. The interaction with the nanodots' basic surface sites promotes the oxidation of dopamine and drives to its oligomerization/polymerization on the nanodot surface.

KLVFF oligopeptide-decorated amphiphilic cyclodextrin nanomagnets for selective amyloid beta recognition and fishing

Recognition and capture of amyloid beta (Aβ) is a challenging task for the early diagnosis of neurodegenerative disorders, such as Alzheimer's disease. Here, we report a novel KLVFF-modified nanomagnet based on magnetic nanoparticles (MNP) covered with a non-ionic amphiphilic β-cyclodextrin (SC16OH) and decorated with KLVFF oligopeptide for the self-recognition of the homologous amino-acids sequence of Aβ to collect Aβ (1-42) peptide from aqueous samples. MNP@SC16OH and MNP@SC16OH/Ada-Pep nanoassemblies were fully characterized by complementary techniques both as solid powders and in aqueous dispersions. Single domain MNP@SC16OH/Ada-Pep nanomagnets of 20-40 nm were observed by TEM analysis. DLS and ζ-potential measurements revealed that MNP@SC16OH nanoassemblies owned in aqueous dispersion a hydrodynamic radius of about 150 nm, which was unaffected by Ada-Pep decoration, while the negative ζ-potential of MNP@SC16OH (-40 mV) became less negative (-30 mV) in MNP@SC16OH/Ada-Pep, confirming the exposition of positively charged KLVFF on nanomagnets surface. The ability of MNP@SC16OH/Ada-Pep to recruit Aβ (1-42) in aqueous solution was evaluated by MALDI-TOF and compared with the ineffectiveness of undecorated MNP@SC16OH and VFLKF scrambled peptide-decorated nanoassemblies (MNP@SC16OH/Ada-scPep), pointing out the selectivity of KLVFF-decorated nanohybrid towards Aβ (1-42). Finally, the property of nanomagnets to extract Aβ in conditioned medium of cells over-producing Aβ peptides was investigated as proof of concept of effectiveness of these nanomaterials as potential diagnostic tools.

Characterization of Complex Drug Formulations Using Cryogenic Scanning Electron Microscopy (Cryo-SEM)

The physicochemical properties of complex drug formulations, including liposomes, suspensions, and emulsions, are important for understanding drug release mechanisms, quality control, and regulatory assessment. It is ideal to characterize these complex drug formulations in their native hydrated state. This article describes the characterization of complex drug formulations in a frozen-hydrated state using cryogenic scanning electron microscopy (cryo-SEM). In comparison to other techniques, such as optical microscopy or room-temperature scanning electron microscopy, cryo-SEM combines the advantage of studying hydrated samples with high-resolution imaging capability. Detailed information regarding cryo-fixation, cryo-fracture, freeze-etching, sputter-coating, and cryo-SEM imaging is included in this article. A multivesicular liposomal complex drug formulation is used to illustrate the impact of different cryogenic sample preparation conditions. In addition to drug formulations, this approach can also be applied to biological samples (e.g., cells, bacteria) and soft-matter samples (e.g., hydrogels). © Published 2022. This article is a U.S. Government work and is in the public domain in the USA. Basic Protocol 1: Cryo-fixation to preserve the native structure of samples using planchettes Alternate Protocol: Cryo-fixation to preserve the native structure of biological samples on sapphire disks Basic Protocol 2: Sample preparation for cross-sectional cryo-SEM imaging Basic Protocol 3: Cryo-SEM imaging and microanalysis.

Fast transport of HCl across a hydrophobic layer over macroscopic distances by using a Pt(II) compound as the transporter: micro- and nanometric aggregates as effective transporters

Bis-(diethyl-dithioxamidate)platinum(ii) is able to transport HCl from the donor aqueous phase to the receiving one over a mean distance of 12 cm in about 3 minutes across an organic membrane in the bulk, without stirring of the organic phase, i.e. at a rate far exceeding the unidirectional macroscopic diffusion coefficient. The way in which this surprising phenomenon can happen is linked to the behaviour of HCl which, because of dynamic interactions with [Pt(HEt2C2N2S2)2] (in which HCl is hosted as a tight ion pair [Pt(H2Et2C2N2S2)2][Cl]2) and chloroform molecules, gives rise to observable nanometric and micrometric domains, more dense than the surrounding bulk, whose formation and disaggregation processes accelerate the unidirectional macroscopic diffusion of HCl. Thermodynamic parameters obtained from the study of acid-base behaviour of the system Pt(ii) species/HCl/CHCl3 also agree with the proposed mechanism of HCl transport.

Alteration of neurotransmission and skeletogenesis in sea urchin Arbacia lixula embryos exposed to copper oxide nanoparticles

The extensive use of copper oxide nanoparticles (CuO NPs) in many applications has raised concerns over their toxicity on environment and human health. Herein, the embryotoxicity of CuO NPs was assessed in the black sea urchin Arbacia lixula, an intertidal species commonly present in the Mediterranean. Fertilized eggs were exposed to 0.7, 10 and 20ppb of CuO NPs, until pluteus stage. Interferences with the normal neurotransmission pathways were observed in sea urchin embryos. In detail, evidence of cholinergic and serotoninergic systems affection was revealed by dose-dependent decreased levels of choline and N-acetyl serotonin, respectively, measured by nuclear magnetic resonance (NMR)-based metabolomics, applied for the first time to our knowledge on sea urchin embryos. The metabolic profile also highlighted a significant CuO NP dose-dependent increase of glycine, a component of matrix proteins involved in the biomineralization process, suggesting perturbed skeletogenesis accordingly to skeletal defects in spicule patterning observed previously in the same sea urchin embryos. However, the expression of skeletogenic genes, i.e. SM30 and msp130, did not differ among groups, and therefore altered primary mesenchyme cell (PMC) migration was hypothesized. Other unknown metabolites were detected from the NMR spectra, and their concentrations found to be reflective of the CuO NP exposure levels. Overall, these findings demonstrate the toxic potential of CuO NPs to interfere with neurotransmission and skeletogenesis of sea urchin embryos. The integrated use of embryotoxicity tests and metabolomics represents a highly sensitive and effective tool for assessing the impact of NPs on aquatic biota.

Particle sizing methods for the detection of protein aggregates in biopharmaceuticals

Protein aggregation is a common biological phenomenon which is responsible for degenerative diseases and is problematic in the pharmaceutical industry. According to the rules provided by regulatory agencies, industry is supposed to assess the product quality regarding the presence of subvisible particles. Also, they should evaluate the technologies that are used to measure these particles. Therefore, US FDA and industry have been looking for methods capable of accurately characterizing the protein products. Four sizing techniques reviewed here are good candidates to be used for characterization of protein and their aggregates: dynamic light scattering, size-exclusion chromatography, electron microscopy and Taylor dispersion analysis. The first three are more established techniques while the last one is a more recent and growing technique.

Aggregation behavior of amphiphilic cyclodextrins in a nonpolar solvent: evidence of large-scale structures by atomistic molecular dynamics simulations and solution studies

Chemically modified cyclodextrins carrying both hydrophobic and hydrophilic substituents may form supramolecular aggregates or nanostructures of great interest. These systems have been usually investigated and characterized in water for their potential use as nanocarriers for drug delivery, but they can also aggregate in apolar solvents, as shown in the present paper through atomistic molecular dynamics simulations and dynamic light scattering measurements. The simulations, carried out with a large number of molecules in vacuo adopting an unbiased bottom-up approach, suggest the formation of bidimensional structures with characteristic length scales of the order of 10 nm, although some of these sizes are possibly affected by the assumed periodicity of the simulation cell, in particular at longer lengths. In any case, these nanostructures are stable at least from the kinetic viewpoint for relatively long times thanks to the large number of intermolecular interactions of dipolar and dispersive nature. The dynamic light scattering experiments indicate the presence of aggregates with a hydrodynamic radius of the order of 80 nm and a relatively modest polydispersity, even though smaller nanometer-sized aggregates cannot be fully ruled out. Taken together, these simulation and experimental results indicate that amphiphilically modified cyclodextrins do also form large-scale nanoaggregates even in apolar solvents.

Nanospheres based on PLGA/amphiphilic cyclodextrin assemblies as potential enhancers of Methylene Blue neuroprotective effect

Nanospheres of amphiphilic cyclodextrin and PLGA entrapping Methylene Blue are proposed as potential enhancers of drug neuroprotective effect on neuroblastoma cells.

New Evidence about the Spontaneous Symmetry Breaking: Action of an Asymmetric Weak Heat Source

In the present study, we show how, in a stagnant water solution of uncharged aggregated achiral porphyrin-based molecules, a mirror-symmetry breaking (SB) can be induced and controlled by means of a weak asymmetric thermal gradient. In particular, it is shown that the optical activity of the aggregate porphyrin solution can be generated and reversed, in sign, only acting on the thermal ramp direction (heating or cooling). In order to avoid data misinterpretation, the aggregate structure modifications with the temperature change and the linear dichroism contribution to circular dichroism spectra were evaluated. A model simulation, using a finite element analysis approach describing the thermal flows, shows that small thermal gradients are able to give rise to asymmetric heat flow. The results reported here can be considered new evidence about the spontaneous symmetry breaking phenomenon induced by very weak forces having an important role in the natural chiral selective processes.

Hydrodynamic and Thermophoretic Effects on the Supramolecular Chirality of Pyrene-Derived Nanosheets

Chiroptical properties of two-dimensional (2D) supramolecular assemblies (nanosheets) of achiral, charged pyrene trimers (Py3 ) are rendered chiral by asymmetric physical perturbations. Chiral stimuli in a cuvette can originate either from controlled temperature gradients or by very gentle stirring. The chiroptical activity strongly depends on the degree of supramolecular order of the nanosheets, which is easily controlled by the method of preparation. The high degree of structural order ensures strong cooperative effects within the aggregates, rendering them more susceptible to external stimuli. The samples prepared by using slow thermal annealing protocols are both CD and LD active (in stagnant and stirred solutions), whereas for isothermally aged samples chiroptical activity was in all cases undetectable. In the case of temperature gradients, the optical activity of 2D assemblies could be recorded for a stagnant solution due to migration of the aggregates from the hottest to the coldest regions of the system. However, a considerably stronger exciton coupling, coinciding with the J-band of the interacting pyrenes, is developed upon subtle vortexing (0.5 Hz, 30 rpm) of the aqueous solution of the nanosheets. The sign of the exciton coupling is inverted upon switching between clockwise and counter-clockwise rotation. The supramolecular chirality is evidenced by the appearance of CD activity. To exclude artefacts from proper CD spectra, the contribution from LD to the observed CD was determined. The data suggest that the aggregates experience asymmetrical deformation and alignment effects because of the presence of chiral flows.

Control of the structural stability of α-crystallin under thermal and chemical stress: the role of carnosine

The structural properties of α-crystallin, the major protein of the eye lens of mammals, in aqueous solution are investigated by means of small angle X-ray and dynamic light scattering. The research interest is devoted in particular to the effect of carnosine in protecting the protein under stress conditions, like temperature increase and presence of denaturant (guanidinium-HCl). The results suggest that carnosine interacts, through mechanisms involving hydrophobic interactions, with α-crystallin and avoids the structural changes in the quaternary structure induced by thermal and chemical stress. It is also shown that, if mediated by carnosine, the self-aggregation of α-crystallin induced by the denaturant at higher temperature can be controlled and even partially reversed. Therefore, carnosine is effective in preserving the structural integrity of the protein, suggesting the possibility of new strategies of intervention for preventing or treating pathologies related to protein aggregation, like cataracts.

Molecular and cytotoxic properties of hIAPP17-29 and rIAPP17-29 fragments: a comparative study with the respective full-length parent polypeptides

The human islet polypeptide (hIAPP) or amylin is a 37-residue peptide hormone secreted by β-cells of the islet of Langerhans in the pancreas. Unlike the rat variant of IAPP (rIAPP), human amylin is highly amyloidogenic and is found as amyloid deposits in nearly 95% of patients afflicted with type 2 diabetes mellitus (T2DM). Human and rat IAPP have nearly identical primary sequence differing at only six positions which are encompassed within the 17-29 aminoacid region. Using Circular Dichroism (CD), Dynamic Light Scattering (DLS) and ThT-fluorescence (Th-T), we examined the aggregation properties of both full-length hIAPP1-37 and the related peptide fragment hIAPP17-29. For the sake of comparison, similar experiments were carried out on the respective rat variants rIAPP1-37 and rIAPP17-29. These studies were conducted at physiological pH in buffered solution not containing fluorinated co-solvents as well as in the presence of model membranes (LUV). In addition, the cytotoxic activity of the investigated peptides was determined toward different pancreatic β-cell lines. All the peptide studied in this work resulted cytotoxic despite β-sheet structure being observed, in vitro, for the hIAPP1-37 only. This suggests that β-sheet conformational transition that generally precedes the fibril formation, is not a prerequisite for toxicity towards β-cells. Interestingly, confocal microscopy indicated that the IAPP peptides can enter the cell and might exert their toxic action at an intracellular level.

Supramolecular chirality induced by a weak thermal force

We show that the unexpected chirality of aggregated structures based on an uncharged achiral porphyrin system originates from small temperature gradients that act as an asymmetrical physical perturbation; the consequent thermal force gives rise to the thermophoretic motion of the aggregates. We establish that the induced optical activity can be controlled, and even vanished, by minimizing the thermal force.

Structural and spectroscopic features of lutein/butanoyl-β-cyclodextrin nanoassemblies

Lutein, the primary carotenoid present in the central area of the retina of eye appears to be associated with the protection against age-related macular degeneration (the leading cause of blindness in older adults). Its lipophilicity and consequently its scarce water solubility (1.3×10(-9)M) represent a drawback for bioavailability. To circumvent these unfavorable characteristics, in this work lutein (Lut) have been encapsulated in amphiphilic cyclodextrin (ACyD) by following the well-established strategy of entrapping a lipophilic drug in CyD carriers. Primary face butyrate modified β-cyclodextrins (C(4:7)) form in water nanoaggregates with a average size of 250nm and a ζ-potential of about -6mV. They are able to entrap lutein at 1:6 Lut/ACyD molar ratio by yielding nanoassemblies of vesicular aspect (320nm and -8mV) such as observed by static, dynamic and electrophoretic light-scattering. UV-vis measurements revealed that electronic properties of lutein were maintained when interact with ACyD nanoaggregates. The monitoring of the entapped carotenoid leaking from ACyD nanostructures was investigated suggesting the potential of Lut/ACyD nanoassemblies in drug delivery.

Modulated heterodyne light scattering set-up for measuring long relaxation time at small and wide angle

We present a simple, compact, and versatile experimental setup working in the heterodyne detection mode with modulation of the reference beam. The system is implemented with a collection optics based on a unimodal optical fiber coupler. This choice allows the heterodyne to be used in a wide range of scattering angles, even for very small ones, without losing the optical beating. The apparatus can be successfully used to study translational diffusive dynamics of dispersed particles at scattering angles smaller than 5° and it is suitable for exploring slow relaxation processes in sub-Hertz frequency domain, for example, in glass-forming systems. It is also possible to measure the electrophoretic mobility by applying an electric field into a charged particles solution.

Unraveling the early events of amyloid-β protein (Aβ) aggregation: techniques for the determination of Aβ aggregate size

The aggregation of proteins into insoluble amyloid fibrils coincides with the onset of numerous diseases. An array of techniques is available to study the different stages of the amyloid aggregation process. Recently, emphasis has been placed upon the analysis of oligomeric amyloid species, which have been hypothesized to play a key role in disease progression. This paper reviews techniques utilized to study aggregation of the amyloid-β protein (Aβ) associated with Alzheimer's disease. In particular, the review focuses on techniques that provide information about the size or quantity of oligomeric Aβ species formed during the early stages of aggregation, including native-PAGE, SDS-PAGE, Western blotting, capillary electrophoresis, mass spectrometry, fluorescence correlation spectroscopy, light scattering, size exclusion chromatography, centrifugation, enzyme-linked immunosorbent assay, and dot blotting.

Selection of supramolecular chirality by application of rotational and magnetic forces

Many essential biological molecules exist only in one of two possible mirror-image structures, either because they possess a chiral unit or through their structure (helices, for example, are intrinsically chiral), but so far the origin of this homochirality has not been unraveled. Here we demonstrate that the handedness of helical supramolecular aggregates formed by achiral molecules can be directed by applying rotational, gravitational and orienting forces during the self-assembly process. In this system, supramolecular chirality is determined by the relative directions of rotation and magnetically tuned effective gravity, but the magnetic orientation of the aggregates is also essential. Applying these external forces only during the nucleation step of the aggregation is sufficient to achieve chiral selection. This result shows that an almost instantaneous chiral perturbation can be transferred and amplified in growing supramolecular self-assemblies, and provides evidence that a falsely chiral influence is able to induce absolute enantioselection.

Polymeric nanoparticles for the selective therapy of inflammatory bowel disease

The two main forms of inflammatory bowel disease (IBD) are Crohn's disease and ulcerative colitis. Both diseases are chronic relapsing inflammations of the gut. The challenge for drug carrier systems that are used for the therapy of IBD is the delivery of the active ingredient to the site of inflammation. A site-directed targeting should lead to higher local drug concentrations, less systemic absorption, and therewith to less adverse effects. Because nanoparticulate drug carrier systems have the ability to accumulate in the inflamed regions, they offer a new targeting approach in IBD. We describe preparation techniques for polymeric nanoparticles and methods to characterize their physicochemical properties, their behavior in cell culture, and the therapeutic efficiency in murine experimental colitis models.

Sequence, stoichiometry, and dimensionality control in porphyrin/bis-calix[4]arene self-assemblies in aqueous solution

The use of a water-soluble octacationic bis-calix[4]arene with divergent cavities (BC(4)) as a templating agent for the assembly of a tetraanionic porphyrin (CuTPPS) has allowed the noncovalent synthesis of 2D or 3D multiporphyrin assemblies. Self-assembly of CuTPPS and BC(4) molecules proceeded under hierarchical control in a stepwise fashion to yield discrete and isolable supramolecular nanostructures containing up to 33 molecular elements (i.e., the CuTPPS/BC(4) 17:16 assembly, obtained in less than three hours). The formation of these species could be conveniently monitored by means of UV/Vis spectroscopy by following the absorbance of the Soret band at 412 nm. In particular, the attainment of the pivotal CuTPPS/BC(4) 5:4 species with a cruciform structure, as the key fork-point intermediate for the subsequent formation of the higher 2D and 3D assemblies, has been demonstrated by light-scattering studies and by an unequivocal synthesis of mixed-porphyrin/calixarene 5:4 species involving the use of two different types of metallated porphyrins, namely CuTPPS and MnTPPS. The remarkable stability of these assemblies permits a stepwise synthesis that makes it possible to choose the desired porphyrin sequence.

Cell volume regulation following hypotonic shock in hepatocytes isolated from Sparus aurata

The response of isolated hepatocytes of Sparus aurata to hypotonic shock was studied by the aid of videometric and light scattering methods. The isolated cells exposed to a rapid change (from 370 to 260 mOsm/kg) of the osmolarity of the bathing solution swelled but thereafter underwent a decrease of cell volume tending to recovery the original size. This homeostatic response RVD (regulatory volume decrease) was inhibited in the absence of extracellular Ca²+ and in the presence of TMB8, an inhibitor of Ca²+ release from intracellular stores. It is likely that Ca²+ entry through verapamil sensitive Ca²+-channels, probably leading to a release of Ca²+ from intracellular stores, is responsible for RVD since the blocker impaired the ability of the cell to recover its volume after the hypotonic shock. RVD tests performed in the presence of various inhibitors of different transport mechanisms, such as BaCl₂, quinine, glybenclamide and bumetanide as well as in the presence of a KCl activator, NEM, led us to suggest that the recovery of cell volume in hypotonic solution is accomplished by an efflux of K+ and Cl⁻ through conductive pathways paralleled by the operation of the KCl cotransport, followed by an obliged water efflux from the cells.

Precision patterning with luminescent nanocrystal-functionalized beads

A reliable strategy is presented to combine the preparation of functional building blocks based on polymer beads decorated with luminescent nanocrystals (NCs) and their precise positioning onto suitable patterns by capillary assembly technique. In particular, a layer-by-layer (LbL) polyelectrolyte (PE) deposition procedure has been implemented to provide uniform NC coverage on PS beads, thus conveying the optical properties of luminescent nanocrystals to highly processable PS beads. The latter have then been integrated into patterned stamps by means of template-driven capillary assembly. Their selective positioning has been directed by means of pattern geometry. The use of luminescent (CdSe)ZnS NCs offers a direct optical probe to evaluate the efficiency of the positioning procedure on the substrate, enabling the extension of the method to a wide range of materials, i.e., NCs with different compositions and specific geometry-dependent properties. Moreover, the precise control over the pattern geometry and the micrometer accuracy in positioning achieved by capillary assembly make such functional patterned structures excellent candidates for integration into devices exploiting specific size-dependent NC properties.

Selective death of human breast cancer cells by lytic immunoliposomes: Correlation with their HER2 expression level

Trastuzumab (Herceptin) targets the human epidermal growth factor receptor 2 (HER2), which is overexpressed in 20-30% of breast and ovarian cancers carrying a bad prognosis. Our purpose was to target HER2-overexpressing human breast cancer cells with pegylated immunoliposomes bearing trastuzumab and containing melittin, which has recently shown anticancer properties. Using a panel of human breast cancer cells with different HER2 expression levels, these immunoliposomes decreased cancer cells viability in a dose-response manner and in correlation to their level of HER2 expression. Specific binding of the immunoliposomes to SKBr3 breast cancer cells was shown by ImageStream-based analysis. The morphological changes observed in the treated cells suggested a cytolytic process. This preclinical approach may suppose an effective strategy for the treatment of HER2-overexpressing tumors, and can support the development of an early phases I-II clinical trial. Trastuzumab resistant breast cancer cells (JIMT-1), can also be targeted using this approach.

Surfactant-like behavior of short-chain alcohols in porphyrin aggregation

UV/vis absorption and time-resolved fluorescence measurements on alcoholic solutions of meso-tetrakis(4-sulfonatophenyl)porphyrin (TPPS(4)) in neutral and acid form have been performed as a function of the alcohol polarity. These solutions show a peculiar behavior that mimics porphyrin in confined water solutions. In alcohols, TPPS(4) exhibits a metastable phase showing the formation of new species in analogy with the confined water environment of AOT microemulsions. Various species have been detected at different pH values and on aging the solutions. Under neutral pH conditions, the porphyrin is present as free base monomer (S415) with a small amount of H-dimeric species (S400). On aging, the S415 leads to the formation of a new species (S423), which has been assigned as a J-type dimer of the neutral porphyrin. The species S400 and S423 are not present in bulk water solution but are typical of TPPS(4) in confined water. On decreasing pH, the S415 almost immediately converts into the diacid form (S438), which evolves toward red-shifted J-aggregates (S490) and blue-shifted H-aggregates (S420). On decreasing alcohol polarity, the kinetic evolution from fresh to aged solution and from the monomeric diacid species to H- and J-aggregates speeds up. Exploiting the amphiphilic character of short chain alcohols and widely varying their polarity, we were able to enhance in bulk conditions the peculiar behavior observed in close proximity to the microemulsion wall.