SENSIA is a technological leader company in the field of analytical instrumentation based on SPR (Surface Plasmon Resonance), for life sciences laboratories and environmental measurements.
Graphene biosensing in SPR, in combination with nanoparticles and/ or bacteria:
Sensia has developed in 2014 an innovative SPR (Surface Plasmon Resonance) solution, using graphene biosensing and introducing on the market the first available commercial graphene biosensors, in a device whose microfluidics have been conceived to withstand the use of bacteria and/or of nanoparticles.
The conception of the optical system enables extreme versatility, allowing the indifferent use of gold biosensors, of graphene coated biosensors, and of silica coated biosensors, with no required change of geometry of the optical platform, although the refractive indexes change.
Several strategies of immobilization can be therefore used .
The combination of graphene biosensors and of nanoparticles in our SPR device, the Indicator-G, leads to new unattained limits of detection, getting into the attomolar range.
Differentiation of Crohn’s Disease-Associated Isolates from Other Pathogenic Escherichia coli by Fimbrial Adhesion under Shear Force
Abstract: Shear force exerted on uropathogenic Escherichia coli adhering to surfaces makes type-1 fimbriae stretch out like springs to catch on to mannosidic receptors. This mechanism is initiated by a disruption of the quaternary interactions between the lectin and the pilin of the two-domain FimH adhesin and transduces allosterically to the mannose-binding pocket of FimH to increase its affinity. Mannose-specific adhesion of 14 E. coli pathovars was measured under flow, using surface plasmon resonance detection on functionalized graphene-coated gold interfaces. Increasing the shear had important differential consequences on bacterial adhesion. Adherent-invasive E. coli, isolated from the feces and biopsies of Crohn’s disease patients, consistently changed their adhesion behavior less under shear and displayed lower SPR signals, compared to E. coli opportunistically infecting the urinary tract, intestines or loci of knee and hip prostheses. We exemplified this further with the extreme behaviors of the reference strains UTI89 and LF82. Whereas their FimA major pilins have identical sequences, FimH of LF82 E. coli is marked by the Thr158Pro mutation. Positioned in the inter-domain region known to carry hot spots of mutations in E. coli pathotypes, residue 158 is indicated to play a structural role in the allosteric regulation of type-1 fimbriae-mediated bacterial adhesion.
Keywords: adherent-invasive Escherichia coli; shear force; surface plasmon resonance; graphene; heptyl α-d-mannose
Surface Plasmon Resonance (SPR) for the Evaluation of Shear-Force-Dependent Bacterial Adhesion
Abstract: The colonization of Escherichia coli (E. coli) to host cell surfaces is known to be a glycan-specific process that can be modulated by shear stress. In this work we investigate whether flow rate changes in microchannels integrated on surface plasmon resonance (SPR) surfaces would allow for investigating such processes in an easy and high-throughput manner. We demonstrate that adhesion of uropathogenic E. coli UTI89 on heptyl α-d-mannopyranoside-modified gold SPR substrates is minimal under almost static conditions (flow rates of 10 µL·min−1), and reaches a maximum at flow rates of 30 µL·min−1 (≈30 mPa). This concept is applicable to the investigation of any ligand-pathogen interactions, offering a robust, easy, and fast method for screening adhesion characteristics of pathogens to ligand-modified interfaces.
(This article belongs to the Special Issue «Affinity Sensors»)
Plasmonic Photothermal Therapy of uropathogenic E. coli with reduced graphene oxide and core/shell nanocomposites of gold nanorods/reduced graphene oxide
Abstract:The development of non antibiotic based treatments against bacterial infections by gram-negative uropathogenic E. coli is a complex task. New strategies to treat such infections are thus urgently needed. This report illustrates the development of pegylated reduced graphene oxide nanoparticles (rGO-PEG) and gold nanorods (Au NRs) coated with rGO-PEG (rGO-PEG-Au NRs) for the selective killing of uropathogenic E. coli UTI89. We took advantage of the excellent light absorption properties of rGO-PEG and Au NRs particles in the near-infrared (NIR) to photothermally kill gram-negative pathogens up to 99% in 10 min. by illumination of solutions containing the bacteria. The rGO-PEG-Au NRs demonstrated better photothermal efficiency towards E. coli than rGO-PEG. Targeted killing of E. coli UTI89 could be achieved with rGO-PEG-Au NRs functionalized with multimeric heptyl α-D-mannoside probes. This currently offers a unique biocompatible method for the ablation of pathogens with the opening of probably a new possibility for clinical treatments of patients with urinary infections.
Highly sensitive detection of DNA hybridization on commercialized graphene coated surface plasmon resonance interfaces
Abstract: Strategies employed to interface biomolecules with nanomaterials have advanced considerably in recent years and found practical applications in many different research fields. The construction of nucleic acid modified interfaces together with the label-free detection of hybridization events has been one of the major research focuses in science and technology. In this paper, we demonstrate the high interest of graphene-on-metal surface plasmon resonance (SPR) interfaces for the detection of DNA hybridization events in the attomolar concentration range. The strategy consists on the non-covalent functionalization of graphene coated SPR interfaces with gold nanostars carrying single-stranded DNA (ssDNA). Upon hybridization with its complementary, desorption of the nanostructures takes place and thus enables the sensitive detection of the DNA hybridization event. The DNA sensor exhibits a detection limit of ≈500 aM for complementary DNA with a linear dynamic range up to 10-8 M. This label-free DNA detection platform should spur off new interest towards the use of commercially available graphene-coated SPR interfaces.