Browsing by Author "Alves, Wendel A."

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    Amphipathic design dictates self-assembly, cytotoxicity and cell uptake of arginine-rich surfactant-like peptides
    (Royal Society of Chemistry, 2020-03-28) Mello, Lucas R.; Aguiar, Rodrigo B.; Yamada, Renata Y.; Moraes, Jane Z.; Hamley, Ian W.; Alves, Wendel A.; Reza, Mehedi; Ruokolainen, Janne; Silva, Emerson R.; Universidade Federal de São Paulo; University of Reading; Universidade Federal do ABC; Department of Applied Physics; Molecular Materials
    Amphiphilicity is the most critical parameter in the self-assembly of surfactant-like peptides (SLPs), regulating the way by which hydrophobic attraction holds peptides together. Its effects go beyond supramolecular assembly and may also trigger different cell responses of bioactive peptide-based nanostructures. Herein, we investigate the self-assembly and cellular effects of nanostructures based on isomeric SLPs composed by arginine (R) and phenylalanine (F). Two amphipathic designs were studied: a diblock construct F4R4 and its bolaamphiphile analog R2F4R2. A strong sequence-dependent polymorphism emerges with appearance of globules and vesicle-like assemblies, or flat nanotapes and cylindrical micelles. The diblock construct possesses good cell penetrating capabilities and effectiveness to kill SK-MEL-28 melanoma tumor cells, in contrast to reduced intracellular uptake and low cytotoxicity exhibited by the bolaamphiphilic form. Our findings demonstrate that amphipathic design is a relevant variable for self-assembling SLPs to modulate different cellular responses and may assist in optimizing the production of nanostructures based on arginine-enriched sequences in cell penetrating and antimicrobial peptides.
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    Interaction between glyphosate pesticide and amphiphilic peptides for colorimetric analysis
    (Royal Society of Chemistry, 2022-07-28) Gerbelli, Barbara B.; Filho, Pedro L.O.; Cortez, Bruna; Sodré, Pedro T.; Coutinho-Neto, Mauricio D.; Hamley, Ian W.; Seitsonen, Jani; Alves, Wendel A.; OtaNano; University of Reading; Niels Bohr Institute; Universidade Federal do ABC
    The large-scale use of glyphosate pesticides in food production has attracted attention due to environmental damage and toxicity risks. Several regulatory authorities have established safe limits or concentrations of these pesticides in water and various food products consumed daily. The irreversible inhibition of acetylcholinesterase (AChE) activity is one of the strategies used for pesticide detection. Herein, we found that lipopeptide sequences can act as biomimetic microenvironments of AChE, showing higher catalytic activities than natural enzymes in an aqueous solution, based on IC50 values. These biomolecules contain in the hydrophilic part the amino acids l-proline (P), l-arginine (R), l-tryptophan (W), and l-glycine (G), covalently linked to a hydrophobic part formed by one or two long aliphatic chains. The obtained materials are referred to as compounds 1 and 2, respectively. According to fluorescence assays, 2 is more hydrophobic than 1. The circular dichroism (CD) data present a significant difference in the molar ellipticity values, likely related to distinct conformations assumed by the proline residue in the lipopeptide supramolecular structure in solution. The morphological aspect was further characterized using small-angle X-ray scattering (SAXS) and cryogenic transmission electron microscopy (cryo-TEM), which showed that compounds 1 and 2 self-assembly into cylindrical and planar core-shell structures, respectively. The mimetic AchE behaviour of lipopeptides was confirmed by Ellman's hydrolysis reaction, where the proline residue in the peptides act as a nucleophilic scavenger of organophosphate pesticides. Moreover, the isothermal titration calorimetry (ITC) experiments revealed that host-guest interactions in both systems were dominated by enthalpically-driven thermodynamics. UV-vis kinetic experiments were performed to assess the inhibition of the lipopeptide catalytic activity and the IC50 values were obtained, and we found that the detection limit correlated with the increase in hydrophobicity of the lipopeptides, implying the micellization process is more favorable.
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    Self-assembly of a catalytically active lipopeptide and its incorporation into cubosomes
    (AMERICAN CHEMICAL SOCIETY, 2019-08-19) Castelletto, Valeria; Edwards-Gayle, Charlotte J.C.; Hamley, Ian W.; Pelin, Juliane N.B.D.; Alves, Wendel A.; Aguilar, Andrea M.; Seitsonen, Jani; Ruokolainen, Janne; University of Reading; Centro de Ciências Naturais e Humanas; Universidade Federal de São Paulo; Department of Applied Physics; Molecular Materials
    The self-assembly and biocatalytic activity of the proline-functionalized lipopeptide PRW-NH-C16 are examined and compared to that of the related PRW-O-C16 lipopeptide, which differs in having an ester linker between the lipid chain and tripeptide headgroup instead of an amide linker. Lipopeptide PRW-NH-C16 self-assembles into spherical micelles above a critical aggregation concentration, similar to the behavior of PRW-O-C16 reported previously [B. M. Soares et al. Phys. Chem. Chem. Phys., 2017, 19, 1181 - 1189]. However, PRW-NH-C16 shows an improved catalytic activity in a model aldol reaction. In addition, we explore the incorporation of the biocatalytic lipopeptide into lipid cubosomes. SAXS shows that increasing lipopeptide concentration leads to an expansion of the monoolein cubosome lattice spacing and a loss of long-range cubic order as the lipopeptide is encapsulated in the cubosomes. At higher loadings of lipopeptide, reduced cubosome formation is observed at the expense of vesicle formation. Our results show that the peptide-lipid chain linker does not influence self-assembly but does impart an improved biocatalytic activity. Furthermore, we show that lipopeptides can be incorporated into lipid cubosomes, leading to restructuring into vesicles at high loadings. These findings point the way toward the future development of bioactive lipopeptide assemblies and slow release cubosome-based delivery systems.
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    Self-Assembly, Nematic Phase Formation, and Organocatalytic Behavior of a Proline-Functionalized Lipopeptide
    (AMERICAN CHEMICAL SOCIETY, 2020-03-25) Pelin, Juliane N.B.D.; Edwards-Gayle, Charlotte J.C.; Castelletto, Valeria; Aguilar, Andrea M.; Alves, Wendel A.; Seitsonen, Jani; Ruokolainen, Janne; Hamley, Ian W.; University of Reading; Universidade Federal de São Paulo; Universidade Federal do ABC; Department of Applied Physics; Molecular Materials
    The self-assembly of the amphiphilic lipopeptide PAEPKI-C16 (P = proline, A = alanine, E = glutamic acid, K = lysine, I = isoleucine, and C16 = hexadecyl) was investigated using a combination of microscopy, spectroscopy, and scattering methods and compared to that of C16-IKPEAP with the same (reversed) peptide sequence and the alkyl chain positioned at the N-terminus and lacking a free N-terminal proline residue. The catalytic activity of these peptides was then compared using a model aldol reaction system. For PAEPKI-C16, the cryo-TEM images showed the formation of micrometer-length fibers, which by small-angle X-ray scattering (SAXS) were found to have radii of 2.5-2.6 nm. Spectroscopic analysis shows that these fibers are built from β-sheets. This behavior is in complete contrast to that of C16-IKPEAP, which forms spherical micelles with peptides in a disordered conformation [ Hutchinson et al. J. Phys. Chem. B 2019, 123, 613 ]. In PAEPKI-C16, spontaneous alignment of fibers was observed upon increasing pH, which was accompanied by observed birefringence and anisotropy of SAXS patterns. This shows the ability to form a nematic phase, and unprecedented nematic hydrogel formation was also observed for these lipopeptides at sufficiently high concentrations. SAXS shows retention of an ultrafine (1.7 nm core radius) fibrillar network within the hydrogel. PAEPKI-C16 with free N-terminal proline shows enhanced anti:syn diastereoselectivity and better conversion compared to C16-IKPEAP. The cytotoxicity of PAEPKI-C16 was also lower than that of C16-IKPEAP for both fibroblast and cancer cell lines. These results highlight the sensitivity of lipopeptide properties to the presence of a free proline residue. The spontaneous nematic phase formation by PAEPKI-C16 points to the high anisotropy of its ultrafine fibrillar structure, and the formation of such a phase at low concentrations in aqueous solution may be valuable for future applications.