1,720,986 research outputs found
Hybrid plasmonic nanoparticle assemblies with tunable properties for biophysical applications
Full text linkIn recent years nanoplasmonics has attracted increasing scientific interest arising from the possibility of manipulating the optical phenomena at the interface of nanostructured materials. Indeed, advances in nanofabrication techniques enabled for tailoring and enhancing electromagnetic fields at the sub-wavelength scale, opening to a wide range of applications in different scientific contexts, spreading from electronics to biomedicine. Among the different nanoarchitectures available, a relevant position is occupied by systems made of nanoparticles (NPs) of noble metals such as gold and silver.
This Ph.D. Thesis is aimed at addressing the design of plasmonic nanostructures with the desired optical and biological properties. The general idea is to reach a strict control on the spatial organisation and surface properties of gold NP assemblies for mastering the plasmon coupling and the interaction with the external environment. Efforts have been made in quantitatively framing the presented studies in the context of nanoplasmonics theory, and in developing interpretative models for the specific phenomena studied.
The results were supported by biological investigation with the purpose of providing a strong scientific background in transferring the obtained findings towards the development of novel biophysical strategies
Surface-Enhanced Raman Scattering of DNA-Nanoparticle assemblies
No full textDuring the last years, soft matter colloids have gained important achievements and a large amount of results have been accomplished to the realisation of innovative and smart nanomaterials. In particular, the understanding in the mastering of DNA-nanoparticle systems, which combine the plasmonic properties of metallic nanoparticles (NPs) with the programmability and self-assembly of DNA strands – opens up a great number of applications in different branches of science, especially in nanoscience. Consequently, the importance of Surface Enhanced Raman Scattering (SERS), which associates a high sensitivity and a specific spectral signature of DNA, is significantly increasing in the detection of specific targets, thus, in the implementation of high-quality biosensors. The DNA base-pairing specificity (A-T, C-G) allows the breakthrough in “programmable bonds” between nanoparticles, serving as the basic building blocks for the creation of mesoscopic plasmonic aggregates.
In our labs we provided to the realisation of DNA-NP structures by properly functionalizing metallic gold NPs with complementary and purposely programmed single-stranded DNA. To this aim, we have chosen two specific single-stranded DNA sequences, consisting of 12 base oligomers, with a thiolgroup at the end of each one which allows to covalent bond onto the metallic NP surfaces; the
aforementioned sequence assures not only a harder and more reproducible bond but also a more controllable adherence. Therefore, it has been possible an ensuing study of the spectroscopic features of these binary systems through the use of SERS. We have thus characterised the SERS spectrum for both DNA sequences-which were attached on gold NPs and obtained a coherent and reproducible signal. The spectra were obtained by using a direct and label-free protocol, thus, avoiding the loss of information about the intrinsic chemical and structural properties of DNA oligonucleotides that fluorescence methods cause. In addition, we provided the realisation of DNA-nanoparticle aggregates, starting from gold nanoparticles functionalized with the two different 12-base DNA
sequences and let them hybridise through the addition of a DNA ‘bridge’ which is a 24 base oligomers complementary to the two chains
Surface-Enhanced Raman Scattering of DNA-Nanoparticle assemblies
No full textDuring the last years, soft matter colloids have gained important achievements and a large amount of results have been accomplished to the realisation of innovative and smart nanomaterials. In particular, the understanding in the mastering of DNA-nanoparticle systems, which combine the plasmonic properties of metallic nanoparticles (NPs) with the programmability and self-assembly of DNA strands – opens up a great number of applications in different branches of science, especially in nanoscience. Consequently, the importance of Surface Enhanced Raman Scattering (SERS), which associates a high sensitivity and a specific spectral signature of DNA, is significantly increasing in the detection of specific targets, thus, in the implementation of high-quality biosensors. The DNA base-pairing specificity (A-T, C-G) allows the breakthrough in “programmable bonds” between nanoparticles, serving as the basic building blocks for the creation of mesoscopic plasmonic aggregates.
In our labs we provided to the realisation of DNA-NP structures by properly functionalizing metallic gold NPs with complementary and purposely programmed single-stranded DNA. To this aim, we have chosen two specific single-stranded DNA sequences, consisting of 12 base oligomers, with a thiolgroup at the end of each one which allows to covalent bond onto the metallic NP surfaces; the
aforementioned sequence assures not only a harder and more reproducible bond but also a more controllable adherence. Therefore, it has been possible an ensuing study of the spectroscopic features of these binary systems through the use of SERS. We have thus characterised the SERS spectrum for both DNA sequences-which were attached on gold NPs and obtained a coherent and reproducible signal. The spectra were obtained by using a direct and label-free protocol, thus, avoiding the loss of information about the intrinsic chemical and structural properties of DNA oligonucleotides that fluorescence methods cause. In addition, we provided the realisation of DNA-nanoparticle aggregates, starting from gold nanoparticles functionalized with the two different 12-base DNA
sequences and let them hybridise through the addition of a DNA ‘bridge’ which is a 24 base oligomers complementary to the two chains
Exploiting SERS sensitivity to monitor DNA aggregation properties
No full textIn the last decades. DNA has been considered far more than the system carrying the essential genetic instructions. Indeed, because of the remarkable properties of the base-pairing specificity and thermoreversibility of the interactions, DNA plays a central role in the design of innovative architectures at the nanoscale. Here, combining complementary DNA strands with a custom-made solution of silver nanoparticles, we realize plasmonic aggregates to exploit the sensitivity of Surface Enhanced Raman Spectroscopy (SERS) for the identification/detection of the distinctive features of DNA hybridization, both in solution and on dried samples. Moreover. SERS allows monitoring the DNA aggregation process by following the temperature variation of a specific spectroscopic marker associated with the Watson-Crick hydrogen bond formation. This temperature-dependent behavior enables us to precisely reconstruct the melting profile of the selected DNA sequences by spectroscopic measurements only. (C) 2020 Elsevier B.V. All rights reserved
The Catalyzing Effect of Aggregates on the Fibrillation Pathway of Human Insulin: A Spectroscopic Investigation During the Lag Phase
Full text linkThe kinetics of insulin aggregation and fibril formation were studied in vitro using Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) spectroscopy. Our investigation centered on the protein’s morphological and structural changes to better understand the transient molecular configurations that occur during the lag phase. SEM images showed that, already at early incubation stages, a network of disordered pseudo-filaments, ranging in length between 200 and 500 nanometers, develops on the surface of large aggregates. At later stages, fibrils catalyzed by protein aggregates were observed. Principal Component Analysis (PCA) of the FTIR data identified signatures of intramolecular β-sheet secondary structures forming during the lag phase and at the onset of the exponential growth phase. These absorption bands are linked to secondary nucleation mechanisms due to their transient nature. This interpretation is further supported by a chemical equilibrium model, which yielded a reliable secondary nucleation rate constant, K2, on the order of 104 M−2 s−1
Antifolate SERS-active nanovectors: quantitative drug nanostructuring and selective cell targeting for effective theranostics
No full textOne of the frontiers of nanomedicine is the rational design of theranostic nanovectors. These are nanosized materials combining diagnostic and therapeutic capabilities, i.e. capable of tracking cancer cells and tissues in complex environments, and of selectively acting against them. We herein report on the preparation and application of antifolate plasmonic nanovectors, made of functionalized gold nanoparticles conjugated with the folic acid competitors aminopterin and methotrexate. Due to the overexpression of folate binding proteins on many types of cancer cells, these nanosystems can be exploited for selective cancer cell targeting. The strong surface enhanced Raman scattering (SERS) signature of these nanovectors acts as a diagnostic tool, not only for tracing their presence in biological samples, but also, through a careful spectral analysis, to precisely quantify the amount of drug loaded on a single nanoparticle, and therefore delivered to the cells. Meanwhile, the therapeutic action is implemented based on the strong toxicity of antifolate drugs. Remarkably, supplying the drug in the nanostructured form, rather than as a free molecule, enhances its specific toxicity. The selectivity of the antifolate nanovectors can be optimized by the design of a hybrid folate/antifolate coloaded nanovector for the specific targeting of folate receptor alpha, which is overexpressed on numerous cancer cell types
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
Responsivity of Fractal Nanoparticle Assemblies to Multiple Stimuli: Structural Insights on the Modulation of the Optical Properties
Full text linkMulti-responsive nanomaterials based on the self-limited assembly of plasmonic nanoparticles are of great interest due to their widespread employment in sensing applications. We present a thorough investigation of a hybrid nanomaterial based on the protein-mediated aggregation of gold nanoparticles at varying protein concentration, pH and temperature. By combining Small Angle X-ray Scattering with extinction spectroscopy, we are able to frame the morphological features of the formed fractal aggregates in a theoretical model based on patchy interactions. Based on this, we established the main factors that determine the assembly process and their strong correlation with the optical properties of the assemblies. Moreover, the calibration curves that we obtained for each parameter investigated based on the extinction spectra point out to the notable flexibility of this nanomaterial, enabling the selection of different working ranges with high sensitivity. Our study opens for the rational tuning of the morphology and the optical properties of plasmonic assemblies to design colorimetric sensors with improved performances
Different impact of menthol chirality on ideal and deep eutectic solvents: Thermal and structural insights
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