Toward Multi-Parametric Porous Silicon Transducers Based on Covalent Grafting of Graphene Oxide for Biosensing Applications

Graphene oxide (GO) is a two-dimensional material with peculiar photoluminescence emission and good dispersion in water, that make it an useful platform for the development of label-free optical biosensors. In this study, a GO-porous silicon (PSi) hybrid device is realized using a covalent chemical approach in order to obtain a stable support for biosensing applications. Protein A, used as bioprobe for biosensing purposes, is covalently linked to the GO, using the functional groups on its surface, by carbodiimide chemistry. Protein A bioconjugation to GO-PSi hybrid device is investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), water contact angle (WCA) measurements, Fourier transform infrared (FTIR) spectroscopy, steady-state photoluminescence (PL), and fluorescence confocal microscopy. PSi reflectance and GO photoluminescence changes can thus be simultaneously exploited for monitoring biomolecule interactions as in a multi-parametric hybrid biosensing device

PNA-based graphene oxide/porous silicon hybrid biosensor: towards a label-free optical assay for Brugada Syndrome

Peptide nucleic acid (PNA) is a synthetic DNA mimic that outperforms the properties of traditional oligonucleotides (ONs). On account of its outstanding features, such as remarkable binding affinity towards complementary DNA or RNA as well as high thermal and chemical stability, PNA has been proposed as a valuable alternative to the ON probe in gene-sensor design. In this study, a hybrid transducer made-up of graphene oxide (GO) nano-sheets covalently grafted onto a porous silicon (PSi) matrix has been investigated for the early detection of a genetic cardiac disorder, the Brugada syndrome (BS). A functionalization strategy towards the realization of a potential PNA-based device is described. A peptide nucleic acid (PNA), able to detect the SCN5A associated with the BS has been properly synthesized and used as a bioprobe for the realization of a proof-of-concept label-free optical PNA-biosensor. PSi reflectance and GO photoluminescence (PL) signals were simultaneously exploited for the monitoring of the device functionalization and response

Design, fabrication and characterization of nanostructured hybrid bio/non-bio interfaces for biomolecular interactions study and industrial applications

Hybrid devices have one or more biological components bioconjugated with functional support surfaces preserving their specific activity and properties. They are extremely interesting from the biotechnological point of view since: 1)They provide a creative way to combine functional properties of different substances into a singular molecular composite; 2) They could show enhanced properties due to the coupling of different elements; 3)Their properties open innovative ways to applications in different fields, such as food, agriculture, medicine and so on. The goal of this PhD thesis is the development of some hybrid-nanocomposites, made of nanostructured materials and biological elements, in which the key issue is the interface between the bio and non-bio components of the systems. Bioconjugated nanostructured materials reveal peculiar physical and chemical properties that can boost their use in biotechnological applications. Inorganic nanoparticles, in particular those based on noble metals and semiconductors in native form or oxide, are becoming common tools in many popular fields of investigation such as nanomedicine, imaging, environmental monitoring and biomolecular sensing. Porous silicon (PSi), Gold nanoparticles (AuNPs) and Zinc Oxide (ZnO) are three highly-performing nanostructured systems whose features have been exploited in this thesis. The research approach used in this work thesis is focused on the synthesis and fabrication of nanostructured support materials, in planar or in nanoparticle shapes, followed by the functionalization and passivation of the material surfaces. Finally, biological elements are immobilized on the solid supports for specific studies and applications. Different hybrid devices have been developed in this work for applications in several research areas, in particular: Hybrid silicon-based device for the detection of Brugada Syndrome for diagnostic purposes; Luminescent silicon nanoparticles as label-free bioprobes for fluorescent bioimaging applications; Hybrid gold-copper nanoparticles as promising contrast agent in nuclear magnetic resonance; Gold nanoparticles complexed to an antimicrobial peptide to enhance the antibacterial activity of the peptide. The results obtained in each case highlighted the innovative potentialities of these nano-complexes in solving problems and breaking barriers in different ambits, spanning from diagnostic to healthcare

Porous Silicon Optical Devices: Recent Advances in Biosensing Applications

This review summarizes the leading advancements in porous silicon (PSi) optical-biosensors, achieved over the past five years. The cost-effective fabrication process, the high internal surface area, the tunable pore size, and the photonic properties made the PSi an appealing transducing substrate for biosensing purposes, with applications in different research fields. Different optical PSi biosensors are reviewed and classified into four classes, based on the different biorecognition elements immobilized on the surface of the transducing material. The PL signal modulation and the effective refractive index changes of the porous matrix are the main optical transduction mechanisms discussed herein. The approaches that are commonly employed to chemically stabilize and functionalize the PSi surface are described

Covalent grafting of graphene oxide on functionalized macroporous silicon

Graphene oxide (GO) is a single-atom-thick and two-dimensional carbon material that has attracted great attention because of its remarkable electronic, mechanical, chemical and thermal properties. GO could be an ideal substrate for the development of label-free optical biosensors, however, its weak photoluminescence (PL) strongly limits the use for this purpose. In this study, we developed a covalent chemical strategy in order to obtain a hybrid GO-macroporous silicon (PSi) structure for biomedical applications. The realized structure was characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM)water contact angle (WCA) measurements, Fourier transform infrared spectroscopy (FTIR) and label- free optical methods based on spectroscopic reflectometry and PL analysis. Investigations showed that the hybrid structure is suitable as a transducer material for biosensing applications due to its peculiar optical properties resulting from the combination of GO and PSi

Synthesis and Surface Modification of Nanostructured F-Doped ZnO: Toward a Transducer for Label-Free Optical Biosensing

In this work, the surface of nanostructured fluorine-doped ZnO (nZnO·F) is functionalized with protein A (PrA), and used as a model biomolecule. The chemical procedure is characterized by several analytical techniques such as Fourier Transform Infrared Spectroscopy, water contact angle analysis, and fluorescence microscopy. The surface modification of nZnO·F by binding increasing concentrations of PrA is also investigated by two label-free optical techniques, i.e., the spectroscopic reflectometry and the steady-state photoluminescence. The results are compared with those obtained using undoped nZnO substrates in order to highlight the better performances of nZnO·F due to the fluorine doping. The results of this study pave the way for the design and realization of a ZnO-based nanostructured platform for label-free optical sensing

Photoemissive properties and stability of undecylenic acid-modified porous silicon nanoparticles in physiological medium

International audienc

Design and Synthesis of Hybrid PEGylated Metal Monopicolinate Cyclam Ligands for Biomedical Applications

International audienceIn this study, we report, for the first time, the synthesis of two original nanosystems, based on gold Au(III) and copper Cu(II): simple gold−copper nanoparticles (Cu 0 AuNPs) and enriched monopicolinate cyclam (L1)−Cu(II)−Au(III)-complex (L1@Cu 2+ AuNPs). The two nanomaterials differ substantially by the chelation or not of the Cu(II) ions during the NPs synthesis process. The two hybrid nanoparticles (Cu 0 AuNPs; L1@Cu 2+ AuNPs) were deeply studied from the chemical and physical point of view, using many different analytical techniques such as Raman and UV−vis spectroscopy, electron transmission microscopy, and dynamic light scattering. Both nanosystems show morphological and good chemical stability at pH 4 values and in physiological conditions during 98 h. Undifferentiated and neural differentiated murine embryonic stem cells were used as a model system for in vitro experiments to reveal the effects of NPs on these cells. The comparative study between Cu 0 AuNPs and L1@Cu 2+ AuNPs highlights that copper chelated in its +2 oxidation state in the NPs is more functional for biological application

POLY-L-LYSINE-CONJUGATED POROUS SILICON NANOPARTICLES AS LABEL-FREE LUMINESCENT PROBES FOR IN VIVO TIME-GATED IMAGING OF HYDRA VULGARIS

In this work, we present the characterization of biocompatible porous silicon nanoparticles (PSiNPs) functionalized with poly-l-lysine following a two-step process. The material exhibits sub-micrometric size, bright photoluminescence (PL) and positive surface charge, coupled with satisfactory morphological and optical stability. Such properties make as-modified PSiNPs effectively exploitable as long-lived photoluminescent probes for rapid time-gated in vivo imaging of Hydra vulgaris

Hybrid Organic/Inorganic Nanomaterials for Biochemical Sensing

In this paper, different nanostructured semiconductors with advanced properties are explored for the realization of both optical and electrical biosensors for DNA detection. A hybrid sensor constituted by graphene oxide (GO) covalently grafted on a porous silicon (PSi) matrix is realized. A peptide nucleic acid (PNA) probe, able to recognize its complementary DNA (c-DNA) sequence, is immobilized on the surface of PSi/GO device for label-free optical sensing. Electrical sensing of DNA is also demonstrated using a Zinc Oxide Nanowires (ZnONWs) sensor functionalized with PNA probe; the I–V characteristic of the device depends on the c-DNA concentration under analysis