Novel electrochemical biosensors based on a biomimetic graphene-lipid bilayer interface

In our work we investigate the development of a novel electrochemical biosensor that integrates a graphene layer as the transducer element for the analysis of electroactive membrane proteins. Graphene is used as transducer because of its unique properties (high surface area, electrical conductivity, ultra-high electron mobility, wide electrochemical potential window, low charge-transfer resistance, reduction of overvoltage), all of which are responsible for the enhancement of the direct electron transfer between graphene and the membrane proteins. However, in biosensors for membrane proteins a major problem is the denaturation of such proteins when they are in contact with the electrode solid surface. To avoid this, membrane proteins are normally embedded in a biological system mimicking their native environment, the supported lipid bilayer (SLB). This study is focused on the synthesis of the graphene interface through chemical vapour deposition, on its surface treatments through a mild oxidation to improve its biocompatibility, and on the investigation of the graphene interface with SLBs. The obtained films of graphene are characterized using scanning electron microscopy, Raman spectroscopy and measuring the water contact angles before and after surface treatments. The interaction of the graphene surface with liposomes and the formation of the graphene-supported lipid bilayer are investigated using electrochemical impedance spectroscopy

Graphene-lipids interaction. Towards the fabrication of a novel sensor for biomedical uses

In this work we investigate the use of graphene as transducer in a novel biosensor for biomedical uses, in which electroactive membrane proteins would serve as biological recognition elements. Membrane proteins maintain their functionalities only if embedded in the cell membrane, so it is necessary to develop a system, which mimics their native environment. This study is focused on surface treatments of graphene to improve its biocompatibility and a first investigation of its interaction with liposomes, which rupture and spread to form a Supported Lipid Bilayer under specific surface conditions. The first step involved the characterization of the graphene membranes synthesized by Chemical Vapor Deposition, using several techniques to determine their morphological and structural properties. From these investigations, the CVD-synthesized graphene resulted to be mono- to few-layer. Next, the interaction of graphene with lipids (1,2-dioleoyl-sn-glicero-3-phosphocholine), in particular the formation of a supported lipid bilayer due to the liposome spreading, was investigated via electrochemical impedance spectroscopy. This indicated the presence of a stable insulating lipid layer on the graphene surface after liposome incubation

Synthesis of smooth graphene surfaces by CVD for electrochemical biosensors with supported lipid membranes

In this work we perform an ab initio study on the design of a novel electrochemical biosensor, in which graphene and membrane proteins would serve as transducer and biological recognition elements, respectively. Graphene is used as transducer because of its unique and intriguing properties, namely surface area, electrical conductivity, ultra high electron mobility, wide electrochemical potential window, low charge-transfer resistance, and reduction of overvoltage. All these properties are responsible for the enhancement of the direct electron transfer between the graphene surface and the membrane proteins. Membrane proteins are the chosen biosensing element for this study since they represent almost 60% of all human protein drug targets. The main problem is that the contact with electrode surface causes the denaturation of membrane proteins, so they need to be embedded in a system mimicking their native environment (i.e. the cell membrane). Supported lipid bilayers (SLBs) are widely used as artificial cell membranes for biophysical studies and nano-biotechnology applications. They are most often generated starting from a liposome solution in which surfaces are incubated for a certain period of time. SLBs form preferentially and are functional on more hydrophilic substrates, whereas graphene surfaces are highly hydrophobic, and so they need to be modified

Study of graphene - supported lipid bilayers interaction for applications in novel electrochemical biosensors

In our work we investigate the development of a novel electrochemical biosensor using graphene as transducer and electroactive membrane proteins as biological recognition elements. Graphene is used as transducer because of its unique properties, namely high surface area, electrical conductivity, ultra-high electron mobility, wide electrochemical potential window, low charge-transfer resistance, and reduction of overvoltage: all these properties are responsible for the enhancement of the direct electron transfer between graphene and the membrane proteins. Membrane proteins are the chosen biosensing element since they are the key factors in cell metabolism, e.g., in cell-cell interactions, signal transduction, and transport of ions and nutrients. Thanks to this important function, membrane proteins are a preferred target for pharmaceuticals, with about 60% of consumed drugs addressing them. The main problem is that the contact with electrode surface causes the denaturation of membrane proteins, so they need to be embedded in a system mimicking their native environment, the supported lipid bilayers (SLBs). This study is focused on the synthesis of graphene through chemical vapour deposition (CVD), on the surface treatments of graphene through a mild oxidation – to improve its biocompatibility – and on the investigation of its interaction with SLBs. High quality graphene is synthetized by chemical vapour deposition and it is characterized by using scanning electron microscopy (SEM) imaging, Raman spectroscopy and by measuring the water contact angles (WCAs) before and after surface treatments. The interaction of graphene with lipids (DOPC - 1,2-dioleoyl-sn-glicero-3-phosphocholine), in particular the formation of SLBs is investigated via electrochemical impedance spectroscopy (EIS), which is a valuable tool for characterizing surface modifications, such as those occurring during the immobilisation of biomolecules (i.e. lipid membrane) on the transducer. A way of interpretation of EIS data is to use an equivalent circuit: its parameters are determined from the best fitting of theoretically calculated impedance plots to experimental ones

Contamination-free graphene by chemical vapor deposition in quartz furnaces

Abstract Although the growth of graphene by chemical vapor deposition is a production technique that guarantees high crystallinity and superior electronic properties on large areas, it is still a challenge for manufacturers to efficiently scale up the production to the industrial scale. In this context, issues related to the purity and reproducibility of the graphene batches exist and need to be tackled. When graphene is grown in quartz furnaces, in particular, it is common to end up with samples contaminated by heterogeneous particles, which alter the growth mechanism and affect graphene’s properties. In this paper, we fully unveil the source of such contaminations and explain how they create during the growth process. We further propose a modification of the widely used quartz furnace configuration to fully suppress the sample contamination and obtain identical and clean graphene batches on large areas

Nanomolded buried light-scattering (BLiS) back-reflectors using dielectric nanoparticles for light harvesting in thin-film silicon solar cells

The article presents a nanoparticle-based buried light-scattering (BLiS) back-reflector design realized through a simplified nanofabrication technique for the purpose of light-management in solar cells. The BLiS structure consists of a flat silver back-reflector with an overlying light-scattering bilayer which is made of a TiO2 dielectric nanoparticles layer with micron-sized inverted pyramidal cavities, buried under a flat-topped silicon nanoparticles layer. The optical properties of this BLiS back-reflector show high broadband and wide angular distribution of diffuse light-scattering. The efficient light-scattering by the buried inverted pyramid back-reflector is shown to effectively improve the short-circuit-current density and efficiency of the overlying n-i-p amorphous silicon solar cells up to 14% and 17.5%, respectively, compared to the reference flat solar cells. A layer of TiO2 nanoparticles with exposed inverted pyramid microstructures shows equivalent light scattering but poor fill factors in the solar cells, indicating that the overlying smooth growth interface in the BLiS back-reflector helps to maintain a good fill factor. The study demonstrates the advantage of spatial separation of the light-trapping and the semiconductor growth layers in the photovoltaic back-reflector without sacrificing the optical benefit

Improvement of CVD-graphene interaction with supported lipid bilayer for the application in novel electrochemical biosensors

In our work we investigate the development of a novel electrochemical biosensor using graphene as transducer and electroactive membrane proteins as biological recognition elements. Graphene is used as transducer because of its unique properties. namely high surface area, electrical conductivity, ultra-high electron mobility, wide electrochemical potential window, low charge-transfer resistance and reduction of overvoltage. All these properties allow the enhancement of the direct electron transfer between graphene and the membrane proteins. [1,2] Membrane proteins are selected as biosensing element since they are the key factors in cell metabolism, e.g. in cell-cell interactions, signal transduction and transport of ions and nutrients. Thanks to this important function, membrane proteins are a preferred target for pharmaceuticals, with about 60% of consumed drugs addressing them. For applications in electrochemical biosensors, the main problem is related to the denaturation of membrane proteins when they get in contact with electrode surface, so they need to be embedded in a system mimicking their native environment, as the supported lipid bilayers (SLBs). The graphene is synthesized by chemical vapour deposition (CVD) and completely characterized by scanning electron microscopy (SEM) imaging, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and water contact angles (WCAs) measurements, both before and after peculiar graphene treatments, performed in order to improve its biocompatibility and enhance its interaction with SLBs. The graphene-SLBs interaction is investigated via electrochemical impedance spectroscopy (EIS), using an equivalent circuit for the interpretation of EIS data: its parameters are determined from the best fitting of theoretically calculated impedance plots to experimental ones

Congenital self-healing reticulohistiocytosis in a newborn: unusual oral and cutaneous manifestations

Abstract Background Congenital self-healing reticulohistiocytosis (CSHRH), also called Hashimoto-Pritzker disease, is a rare and benign variant of Langerhans cell histiocytosis, characterized by cutaneous lesions without extracutaneous involvement. Case presentation We present a case of CSHRH with diffuse skin lesions and erosions in the oral mucosa, present since birth and lasting for 2 months, and we perform a review of the literature on Pubmed in the last 10 years. Conclusions Our case confirm that lesions on oral mucosa, actually underestimated, may be present in patients with CSHRH. Patients affected by CSHRH require a close follow-up until the first years of life, due to the unpredictable course of Langerhans cell histiocytosis, in order to avoid missing diagnosis of more aggressive types of this disorder

Near-infrared photodetectors based on embedded graphene

In last years, the introduction of 2-dimensional materials such as graphene has revolutionized the world of silicon photonics. In this work, we demonstrate a new approach for integrating graphene into silicon-based photodetectors. We leverage a thin film of hydrogenated amorphous silicon to embed the graphene within two different photonic structures, an optical Fabry-Pérot microcavity, and a waveguide, achieving a stronger light-matter interaction. The investigated devices have shown promising performance resulting in responsivities as high as 27 mA/W and 0.15 A/W around 1550 nm, respectively