Nanoencapsulation of Anthocyanins from Red Cabbage (Brassica oleracea L. var. Capitata f. rubra) through Coacervation of Whey Protein Isolate and Apple High Methoxyl Pectin.

Encapsulation is a valuable strategy to protect and deliver anthocyanins (ACNs), phenolic compounds with outstanding antioxidant capacity but limited stability. In this study, coacervation was used to encapsulate an ACN-rich red cabbage extract (RCE). Two agri-food by-product polymers, whey protein isolate (WPI) and apple high-methoxyl pectin (HMP), were blended at pH 4.0 in a specific ratio to induce the formation of nanoparticles (NPs). The process optimisation yielded a monodispersed population (PDI < 0.200) of negatively charged (-17 mV) NPs with an average diameter of 380 nm. RCE concentration influenced size, charge, and antioxidant capacity in a dose-dependent manner. NPs were also sensitive to pH increases from 4 to 7, showing a progressive breakdown. The encapsulation efficiency was 30%, with the retention of ACNs within the polymeric matrix being influenced by their chemical structure: diacylated and/or C3-triglucoside forms were more efficiently encapsulated than monoacylated C3-diglucosides. In conclusion, we report a promising, simple, and sustainable method to produce monodispersed NPs for ACN encapsulation and delivery. Evidence of differential binding of ACNs to NPs, dependent on specific acylation/glycosylation patterns, indicates that care must be taken in the choice of the appropriate NP formulation for the encapsulation of phenolic compounds.

Ln(III) Complexes Embedded in Biocompatible PLGA Nanoparticles as Potential Vis-to-NIR Optical Probes.

In this contribution, we present the spectroscopic study of two NIR emitting hydrophobic heteroleptic (R,R)-YbL1(tta) and (R,R)-NdL1(tta) complexes (with tta = 2-thenoyltrifluoroacetonate and L1 = N,N'-bis(2-(8-hydroxyquinolinate)methylidene)-1,2-(R,R or S,S)-cyclohexanediamine), both in methanol solution and embedded in water dispersible and biocompatible poly lactic-co-glycolic acid (PLGA) nanoparticles. Thanks to their absorption properties in a wide range of wavelengths extending from the UV up to the blue and green visible regions, the emission of these complexes can be effectively sensitized using visible radiation, which is much less harmful to tissues and skin than the UV one. The encapsulation of the two Ln(III)-based complexes in PLGA allows us to preserve their nature, making them stable in water and to test their cytotoxicity on two different cell lines, with the aim of using them in the future as potential bioimaging optical probes.

Near Infared Circularly Polarized Luminescence From Water Stable Organic Nanoparticles Containing a Chiral Yb(III) Complex.

We report the first example of very efficient NIR Circularly Polarized Luminescence (CPL) (around 970 nm) in water, obtained thanks to the combined use of a chiral Yb complex and of poly lactic-co-glycolic acid (PLGA) nanoparticles. [YbL(tta)2 ]CH3 COO (L=N, N'-bis(2-pyridylmethylidene)-1,2-(R,R+S,S) cyclohexanediamine and tta=2-thenoyltrifluoroacetonate) shows good CPL in organic solvents, because the tta ligands efficiently sensitize Yb NIR luminescence and the readily prepared chiral ligand L endows the complex with the necessary dissymmetry. PLGA nanoparticles incorporate the complex and protect the metal ion from the intrusion of solvent molecules, while ensuring biocompatibility, water solubility and stability to the complex. Hydrophilic NIR-CPL optical probes can find applications in the field of NIR-CPL bio-assays.

Improving the Cellular Uptake of Biomimetic Magnetic Nanoparticles.

Magnetococcus marinus magnetosome-associated protein MamC, expressed as recombinant, has been proven to mediate the formation of novel biomimetic magnetic nanoparticles (BMNPs) that are successful drug nanocarriers for targeted chemotherapy and hyperthermia agents. These BMNPs present several advantages over inorganic magnetic nanoparticles, such as larger sizes that allow the former to have larger magnetic moment per particle, and an isoelectric point at acidic pH values, which allows both the stable functionalization of BMNPs at physiological pH value and the molecule release at acidic (tumor) environments, simply based on electrostatic interactions. However, difficulties for BMNPs cell internalization still hold back the efficiency of these nanoparticles as drug nanocarriers and hyperthermia agents. In the present study we explore the enhanced BMNPs internalization following upon their encapsulation by poly (lactic-co-glycolic) acid (PLGA), a Food and Drug Administration (FDA) approved molecule. Internalization is further optimized by the functionalization of the nanoformulation with the cell-penetrating TAT peptide (TATp). Our results evidence that cells treated with the nanoformulation [TAT-PLGA(BMNPs)] show up to 80% more iron internalized (after 72 h) compared to that of cells treated with BMNPs (40%), without any significant decrease in cell viability. This nanoformulation showing optimal internalization is further characterized. In particular, the present manuscript demonstrates that neither its magnetic properties nor its performance as a hyperthermia agent are significantly altered due to the encapsulation. In vitro experiments demonstrate that, following upon the application of an alternating magnetic field on U87MG cells treated with BMNPs and TAT-PLGA(BMNPs), the cytotoxic effect of BMNPs was not affected by the TAT-PLGA enveloping. Based on that, difficulties shown in previous studies related to poor cell uptake of BMNPs can be overcome by the novel nanoassembly described here.

Ozone at low concentrations does not affect motility and proliferation of cancer cells in vitro.

Exposure to low ozone concentrations is used in medicine as an adjuvant/complementary treatment for a variety of diseases. The therapeutic potential of low ozone concentrations relies on their capability to increase the nuclear translocation of the Nuclear factor erythroid 2-related factor 2 (Nrf2), thus inducing the transcription of Antioxidant Response Elements (ARE)-driven genes and, through a cascade of events, a general cytoprotective response. However, based on the controversial role of Nrf2 in cancer initiation, progression and resistance to therapies, possible negative effects of ozone therapy may be hypothesised in oncological patients. With the aim to elucidate the possible changes in morphology, migration capability and proliferation of cancer cells following mild ozone exposure, we performed wound healing experiments in vitro on HeLa cells treated with low ozone concentrations currently used in the clinical practice. By combining a multimodal microscopy approach (light and fluorescence microscopy, scanning electron microscopy, atomic force microscopy) with morphometric analyses, we demonstrated that, under our experimental conditions, exposure to low ozone concentrations does not alter cytomorphology, motility and proliferation features, thus supporting the notion that ozone therapy should not positively affect tumour cell growth and metastasis.

Dynamic molecular exchange and conformational transitions of alpha-synuclein at the nano-bio interface.

The notion that nanoscale surfaces influence protein conformational transitions stimulates the investigation of fibrillogenic polypeptides adsorbing to nanomaterials. Alpha-synuclein (αS) is a prototypical amyloidogenic protein whose aggregation is associated with severe neurodegenerative disorders. We explored the interaction of αS with silica nanoparticles (SNPs) in diverse solution conditions, ranging from protein-free to protein-rich media. We found that the SNP-binding region of αS, determined by site-resolved NMR spectroscopy, was similar in simple buffer and blood serum. Competition binding experiments with isotopic homologues and different proteins showed that cosolutes elicited molecular exchange in a protein-specific manner. The interaction of an oxidized, fibrillation-resistant protein form with SNPs was similar to that of unmodified αS. SNPs, however, did not stimulate fibrillation of the oxidized protein, which remained fibrillation incompetent. CD experiments revealed SNP-induced perturbations of the structural properties of oxidized and non-oxidized αS. Thus, while αS binding to SNPs is essentially orthogonal to fibril formation, the interaction perturbs the distribution of conformational states populated by the protein in the colloidal suspension. This study sheds light on the dynamic nature of αS interactions with NPs, an aspect that crucially impacts on our ability to control aggregation of αS.

Semisynthetic and Enzyme-Mediated Conjugate Preparations Illuminate the Ubiquitination-Dependent Aggregation of Tau Protein.

In the brain of individuals with Alzheimer's disease, the regulatory protein ubiquitin is found conjugated to different lysine residues of tau protein assembled into pathological paired helical filaments. To shed light on the hitherto unexplored ubiquitination-linked conformational transitions of tau, the availability of in vitro ubiquitin conjugation methods is of primary importance. In our work, we focused on the four-repeat domain of tau and assembled an enzymatic machinery formed by UBE1, Ubc13, and CHIP enzymes. The enzymatic reaction resulted in monoubiquitination at multiple sites, reminiscent of the ubiquitination pattern observed in vivo. We further exploited chemoselective disulfide coupling reactions to construct three tau regioisomers with site-specific monoubiquitination. Protein aggregation experiments revealed that the multiple enzyme-derived products were unable to convert into amyloid fibrils, while the semisynthetic conjugates exhibited diverse capability to form filaments. This study contributes novel insight into the effects of a key post-translational modification on aberrant protein self-assembly.

Encapsulation of Photosystem I in Organic Microparticles Increases Its Photochemical Activity and Stability for Ex Vivo Photocatalysis.

Photosystem I (PSI) is a pigment binding multisubunit protein complex involved in the light phase of photosynthesis, catalyzing a light-dependent electron transfer reaction from plastocyanin to ferredoxin. PSI is characterized by a photochemical efficiency close to one, suggesting its possible application in light-dependent redox reaction in an extracellular context. The stability of PSI complexes isolated from plant cells is however limited if not embedded in a protective environment. Here we show an innovative solution for exploiting the photochemical properties of PSI, by encapsulation of isolated PSI complexes in PLGA (poly lactic-co-glycolic acid) organic microparticles. These encapsulated PSI complexes were able to catalyze light-dependent redox reactions with electron acceptors and donors outside the PLGA microparticles. Moreover, PSI complexes encapsulated in PLGA microparticles were characterized by a higher photochemical activity and stability compared with PSI complexes in detergent solution, suggesting their possible application for ex vivo photocatalysis.

Novel functionalization strategies of polymeric nanoparticles as carriers for brain medications.

For targeted brain delivery, nanoparticles (NPs) should bypass the blood-brain barrier (BBB). Novel functionalization strategies, based on low-density lipoprotein receptor (LDLR) binding domain, have been here tested to increase the brain targeting efficacy of poly d,l-lactic-co-glycolic acid (PLGA) NPs, biodegradable and suited for biomedical applications. Custom-made PLGA NPs were functionalized with an apolipoprotein E modified peptide (pep-apoE) responsible for LDLR binding, or with lipocalin-type prostaglandin-d-synthase (L-PGDS), highly expressed in the brain. At the comparison of pep-apoE and L-PGDS sequences, a highly homologs region was here identified, indicating that also L-PGDS could bind LDLR. Non-functionalized and functionalized NPs did not affect the viability of cultured human dendritic cells, protagonists of the immune response, and did not activate them to a proinflammatory profile. At 2 h after intravenous injection in mice, functionalized, but not the non-functionalized ones, fluorescent-tagged NPs were observed in the cerebral cortex parenchyma. The NPs were mostly internalized by neurons and microglia; glial cells showed a weak activation. The findings indicate that the tested functionalization strategies do not elicit adverse immune responses and that the peptidic moieties enable BBB traversal of the NPs, thus providing potential brain drug carriers. These could be especially effective for brain diseases in which LDLR is involved. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 847-858, 2017.

Singlet and triplet state transitions of carotenoids in the antenna complexes of higher-plant photosystem I.

In this work, the spectroscopic characteristics of carotenoids associated with the antenna complexes of Photosystem I have been studied. Pigment composition, absorption spectra, and laser-induced triplet-minus-singlet (T-S) spectra were determined for native LHCI from the wild type (WT) and lut2 mutant from Arabidopsis thaliana as well as for reconstituted individual Lhca WT and mutated complexes. All WT complexes bind lutein and violaxanthin, while beta-carotene was found to be associated only with the native LHCI preparation and recombinant Lhca3. In the native complexes, the main lutein absorption bands are located at 492 and 510 nm. It is shown that violaxanthin is able to occupy all lutein binding sites, but its absorption is blue-shifted to 487 and 501 nm. The "red" lutein absorbing at 510 nm was found to be associated with Lhca3 and Lhca4 which also show a second carotenoid, peaking around 490 nm. Both these xanthophylls are involved in triplet quenching and show two T-S maxima: one at 507 nm (corresponding to the 490 nm singlet absorption) and the second at 525 nm (with absorption at 510 nm). The "blue"-absorbing xanthophyll is located in site L1 and can receive triplets from chlorophylls (Chl) 1012, 1011, and possibly 1013. The red-shifted spectral component is assigned to a lutein molecule located in the L2 site. A 510 nm lutein was also observed in the trimers of LHCII but was absent in the monomers. In the case of Lhca, the 510 nm band is present in both the monomeric and dimeric complexes. We suggest that the large red shift observed for this xanthophyll is due to interaction with the neighbor Chl 1015. In the native T-S spectrum, the contribution of carotenoids associated with Lhca2 is visible while the one of Lhca1 is not. This suggests that in the Lhca2-Lhca3 heterodimeric complex energy equilibration is not complete at least on a fast time scale.