1,720,968 research outputs found
Engineered peptides on Gold Nanostructures for cell targeting as SERRS biosensors for cancer diagnostics
Full text linkDue to their optical properties, facile surface chemistry and biocompatibility, Gold Nanoparticles (AuNP) have attracted an increasing interest in the last years for Nano-biotechnological applications. Their targeted delivery to malignant tumours, in particular, has become a powerful tool in cancer nanomedicine exploiting AuNP as promising platform for imaging, using for example SERS spectroscopy, diagnosis and therapy. In order to fully exploit their potentialities, AuNP have to be conjugated with active targeting ligands which could improve their pharmacokinetic and pharmacodynamic profiles. Among many targeting agents, such as antibodies, proteins and small molecules, peptides have achieved great success in cancer nanotechnology for their low toxicity and immunogenicity as well as for their relatively low synthetic costs. To achieve an efficient cancer cell targeting a convenient design of the targeting ligands is necessary to optimize the association of the nanostructures with the receptor, reducing the interactions with healthy tissues. However, the effect of the organization of the targeting units on the nanostructures surface has never been studied in detail.
In this PhD thesis the engineering of peptide targeted gold nanostructures, as SERRS biosensors for colorectal and liver cancer diagnostics, is described. The targeting activity of the nanostructures was studied both in vitro on cancer cells and in vivo on murine tumour models. Experimental results were combined to Molecular Dynamics (MD) calculations and spectroscopic analysis to investigate the role of the peptide organization on the nanostructures surface for the receptor recognition. In Chapter 2 methodologies used to synthesize and characterize peptides as well as gold nanostructures are described. Chapters 3-6 are focused on colorectal cancer targeting achieved by conjugating gold nanostructures with peptides specific for the Epidermal Growth Factor receptor (GE11 peptide) and αvβ3 Integrins (RGD peptide), two receptors overexpressed in cancer cells and tissues. In Chapters 3 and 4 the exposure of the targeting units on the nanostructures surface for achieving an efficient association with the receptor is investigated with the help of molecular dynamics. To achieve this goal, several peptide analogues were conveniently synthesized to present the targeting unit in different arrangements on the nanostructure surface and the targeting properties of the resulting nanosystems were assessed. Since among many ligands those engineered by conjugating the peptide to polyethylene glycol (PEG) showed the best targeting activity, the role of the polymer was investigated in dept by studying the targeting activity of nanostructures coated with a mixed monolayer of PEG and peptides (Chapter 5). For in vivo applications of peptide functionalized nanoparticles, the stability to proteolysis of the targeting units is an important issue that was evaluated by incubation of the nanostructures with different proteolytic enzymes and in serum (Chapter 6). Chapter 7 concerns liver cancer cells targeting achieved by functionalizing gold nanostructures with properly designed analogues of the peptide PreS1, known as specific ligand of the Squamous Cell Carcinoma Antigen 1 which is overexpressed in hepatoma and hepatoblastoma. The arguments developed in the thesis are introduced in the Chapter 1
Linker dependent chirality of solvent induced self-assembled structures of porphyrin–α-helical peptide conjugates
No full textThe solvent-promoted aggregation of porphyrins covalently linked to medium length peptides occurs
with the formation of chiral supramolecular structures if the peptide chain can adopt an α-helical secondary
structure. The circular dichroism spectra of different porphyrin–peptide conjugates show that the
chiral arrangement of the porphyrins in the aggregates does not depend on the screw-sense of the
peptide helix. Experimental evidence and molecular dynamic simulations suggest that the linker between
the porphyrin and the peptide helix is responsible for the overall chirality of supramolecular structures. In
particular when the linker is a chiral α-amino acid it is possible to tune the morphology of the chiral
aggregates by inverting the configuration of the chiral center
SYNTHESIS AND BIOFUNCTIONALIZATION OF PLASMONIC NANOSTRUCTURES FOR EGFR-MARKED CANCER CELL TARGETING AND SERRS IMAGING
No full textPlasmonic nanoparticles are increasingly utilized in biomedical applications including imaging, diagnostics and therapy. Gold nanoparticles (AuNP), besides displaying useful optical properties, possess a facile surface chemistry and absence of inherent toxicity, an essential requirement for biological application. AuNP can passively target tumors by the enhanced permeability and retention effect, but active targeting by proteins, peptides or small molecules, can further improve the pharmacokinetic and pharmacodynamics profiles of these multifunctional agents. The dodecapeptide YHWYGYTPQNVI (GE11) was recently identified as a specific ligand for the Epidermal Growth Factor Receptor, which is overexpressed in many types of cancer[1]. In the present work we have employed the enormous sensitivity of the Surface Enhanced Raman Spectroscopy [2] to study the targeting activity of GE11-functionalized plasmonic nanostructures on different types of tumor cells. Nanoparticles were prepared, without stabilizing molecules, by laser ablation of a gold target in water, functionalized with a SERRS reporter [3], and conjugated with a number of ligands: GE11, mPEG, and different PEG-GE11 conjugates. Nanoaggregates covered with PEG or with the monoclonal antibody Cetuximab were used as negative and positive control, respectively. Targeting of nanostructures to EGFR was checked by incubation with cancer cells expressing or not the receptor and recording the SERRS signals for each cell. The influence of different aspects for EGFR recognition, such as peptide orientation and exposure on the NP surface, will be presented
Protection against proteolysis of a targeting peptide on gold nanostructures
No full textCell targeting has been considered an important strategy in diagnostic and therapeutic applications. Among different targeting units, peptides have emerged for their ability to bind to many different cellular targets, their scarce immunogenicity and the possibility of introducing multiple copies on nanosystems, providing high avidity for the target. However, their sensitivity to proteases strongly limits their applications in vivo. Here, we show that when presented on the surface of nanostructures, peptide stability to proteolysis is strongly improved without reducing the targeting activity. We prepared plasmonic nanostructures functionalized with a dodecapeptide (GE11) which targets EGFR, a protein overexpressed on different types of tumors. Two types of nanosystems were prepared in which the targeting unit was either directly linked to gold nanoparticles or through a PEG chain, resulting in a different peptide density on the surface of nanostructures. The peptide was rapidly degraded in 20% human serum or in the presence of isolated serine proteases, whereas no significant proteolytic fragments were detected during incubation of the nanosystems and after 24 h digestion, the nanostructures maintained their targeting activity and selectivity on colon cancer cells. Molecular dynamic calculations of the interaction of the nanostructure with chymotrypsin suggest that the formation of the enzyme-peptide complex, the first step in the mechanism of peptide hydrolysis, is highly unlikely because of the constraint imposed by the link of the peptide to the nanoparticle. These results support the utilization of peptides as active targeting units in nanomedicine
A surface enhanced Raman scattering based colloid nanosensor for developing therapeutic drug monitoring
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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