Antibody-Gold nanoparticle (Ab-AuNP) bioconjugates are widely used in the field of biosensing. This prompted researchers to set up various strategies to conjugate antibodies to gold nanoparticles. ...Optimal conjugation is of critical importance, as the Ab-AuNP bioconjugates should be stable while maintaining the ability of the antibody to recognize and bind its corresponding antigen. All the same, a high coverage of antibodies on AuNPs is a key-step to build up a sensitive biosensor, but an ideal coverage requires to be perfectly balanced with the orientation and accessibility of the conjugated antibodies. In this review, we intend to provide the reader with the key elements allowing for mastering the conjugation of Ab to AuNP and rationalizing, at the molecular level, the mechanisms involved together with the expected antibody coverages and orientations. We will focus on IgG-type antibodies conjugated to spherical AuNPs as these bioconjugates are the most commonly used ones for biosensors. First, we report an exhaustive survey of the methods of conjugation, via strategies of physisorption and chemisorption. Then we provide a critical restitution of the relevant strategies allowing the quantification of antibodies coverage on gold nanoparticles either through direct analysis of the bioconjugates or indirect analysis of the supernatant. In the last part, we review and discuss selected applications of these Ab-AuNP bioconjugates in optical biosensing.
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•The methodologies for antibodies attachment to gold nanoparticles through physical or chemical adsorption are described.•The challenging question of the quantification of antibodies on gold nanoparticles surface is critically addressed.•The importance of mastering the association antibody/gold nanoparticles is highlighted.•A selection of relevant application of gold nanoparticles antibody bioconjugates in optical biosensing is presented.
Gold nanoparticles (AuNPs) have been extensively used for decades in biosensing‐related development due to outstanding optical properties. Peptides, as newly realized functional biomolecules, are ...promising candidates of replacing antibodies, receptors, and substrates for specific molecular interactions. Both peptides and AuNPs are robust and easily synthesized at relatively low cost. Hence, peptide–AuNP‐based bio‐nano‐technological approaches have drawn increasing interest, especially in the field of molecular targeting, cell imaging, drug delivery, and therapy. Many excellent works in these areas have been reported: demonstrating novel ideas, exploring new targets, and facilitating advanced diagnostic and therapeutic technologies. Importantly, some of them also have been employed to address real practical problems, especially in remote and less privileged areas. This contribution focuses on the application of peptide–gold hybrid nanomaterials for various molecular interactions, especially in biosensing/diagnostics and cell targeting/imaging, as well as for the development of highly active antimicrobial/antifouling coating strategies. Rationally designed peptide–gold nanomaterials with functional properties are discussed along with future challenges and opportunities.
Rationally designed functional peptide–gold hybrid nanomaterials for various applications, such as biosensing, targeting, imaging, and so forth, due to their specific molecular interactions, are reviewed. With all the advantages of peptide–gold‐based interactive nano‐approaches, they are promising for future applications in the biomedical domain and beyond, especially in field testing.
High‐adhesion stretchable electrodes are fabricated by utilizing a novel nanopile interlocking strategy. Nanopiles significantly enhance adhesion and redistribute the strain in the film, achieving ...high stretchability. The nanopile electrodes enable simultaneous monitoring of electromyography signals and mechanical deformations. This study opens up a new perspective of achieving stretchability and high adhesion for stretchable electronics.
Localized surface plasmon resonance (LSPR) occurring in noble metal nanoparticles (e.g., Au) is a widely used phenomenon to report molecular interactions. Traditional LSPR sensors typically monitor ...shifts in the peak position or extinction in response to local refractive index changes in the close vicinity of the nanoparticle surface. The ability to resolve minute shifts/extinction changes is to a large extent limited by instrumental noise. A new strategy to evaluate LSPR responses utilizing changes in the shape of the extinction spectrum (the curvature) is proposed. The response of curvature to refractive index changes is investigated theoretically using Mie theory and an analytical expression relating the curvature to the refractive index is presented. The experimentally derived curvatures for 13 nm spherical gold nanoparticles (AuNPs) exposed to solvents with different bulk refractive indices confirm the theoretical predictions. Moreover, both the calculated and experimental findings suggest that the curvature is approximately a linear function of refractive index in regimes relevant to bio and chemical sensing. We demonstrate that curvature is superior over peak shift and extinction both in terms of signal-to-noise (S/N) ratio and reliability of LSPR sensors. With a curvature, one could readily monitor submonolayer adsorption of a low molecular weight thiol molecule (M w = 458.6) onto 13 nm AuNPs. It is also worthwhile mentioning that curvature is virtually insensitive to instrumental instabilities and artifacts occurring during measurement. Instabilities such as baseline tilt and shift, shift in peak position as well as sharp spikes/steps in the extinction spectra do not induce artifacts in the sensorgrams of curvature.
Fiber‐shaped stretchable strain sensors with small testing areas can be directly woven into textiles. This paves the way for the design of integrated wearable devices capable of obtaining real‐time ...mechanical feedback for various applications. However, for a simple fiber that undergoes uniform strain distribution during deformation, it is still a big challenge to obtain high sensitivity. Herein, a new strategy, surface strain redistribution, is reported to significantly enhance the sensitivity of fiber‐shaped stretchable strain sensors. A new method of transient thermal curing is used to achieve the large‐scale fabrication of modified elastic microfibers with intrinsic microbeads. The proposed strategy is independent of the active materials utilized and can be universally applied for various active materials. The strategy used here will shift the vision of the sensitivity enhancement method from the active materials design to the mechanical design of the elastic substrate, and the proposed strategy can also be applied to nonfiber‐shaped stretchable strain sensors.
Surface strain redistribution in substrates significantly enhances sensitivity of fiber‐shaped stretchable strain sensors fabricated by thermal‐transient‐curing and Plateau–Rayleigh instability. Poly(dimethylsiloxane) (PDMS) microfibers with beads are produced in large scale. The beads regulate strain distribution. Novel sensors are well adhered to textiles for monitoring sports activities. This study opens up a new perspective of fiber‐shaped sensors and a method to enhance sensitivity.
We report a smartphone label-free biosensor platform based on grating-coupled surface plasmon resonance (GC-SPR). The sensor system relies on the smartphone's built-in flash light source and camera, ...a disposable sensor chip with Au diffraction grating and a compact disk (CD) as the spectra dispersive unit. The Au grating sensor chip was modified with a synthetic peptide receptor and employed on the GC-SPR detection of lipopolysaccharides (known as endotoxins) with detection limit of 32.5ng/mL in water. Upon incubation of various small and macro-molecules with the synthetic peptide modified sensor chips, we concluded the good selectivity of the sensor for LPS detection. In addition, the sensor shows feasibility for the detection of LPS in commonly used clinical injectable fluids, such as clinical-grade 0.9% sodium chloride intravenous infusion, compound sodium lactate intravenous infusion and insulin aspart. The developed sensor platform offers the advantage of portability and simplicity, which is attractive for point-of-care and remote detection of biomedical and environmental targets.
•A smartphone label-free biosensor based on grating-coupled SPR was developed.•The sensor system relies on the smartphone's built-in flash light and camera.•A synthetic peptide receptor was employed for the detection of LPS (endotoxins).
Giant lipid vesicles are closed compartments consisting of semi-permeable shells, which isolate femto- to pico-liter quantities of aqueous core from the bulk. Although water permeates readily across ...vesicular walls, passive permeation of solutes is hindered. In this study, we show that, when subject to a hypotonic bath, giant vesicles consisting of phase separating lipid mixtures undergo osmotic relaxation exhibiting damped oscillations in phase behavior, which is synchronized with swell-burst lytic cycles: in the swelled state, osmotic pressure and elevated membrane tension due to the influx of water promote domain formation. During bursting, solute leakage through transient pores relaxes the pressure and tension, replacing the domain texture by a uniform one. This isothermal phase transition--resulting from a well-coordinated sequence of mechanochemical events--suggests a complex emergent behavior allowing synthetic vesicles produced from simple components, namely, water, osmolytes, and lipids to sense and regulate their micro-environment.
We report on a smartphone spectrometer for colorimetric biosensing applications. The spectrometer relies on a sample cell with an integrated grating substrate, and the smartphone's built-in ...light-emitting diode flash and camera. The feasibility of the smartphone spectrometer is demonstrated for detection of glucose and human cardiac troponin I, the latter in conjunction with peptide-functionalized gold nanoparticles.
Stretchable conductors are the basic units of advanced flexible electronic devices, such as skin‐like sensors, stretchable batteries and soft actuators. Current fabrication strategies are mainly ...focused on the stretchability of the conductor with less emphasis on the huge mismatch of the conductive material and polymeric substrate, which results in stability issues during long‐term use. Thermal‐radiation‐assisted metal encapsulation is reported to construct an interlocking layer between polydimethylsiloxane (PDMS) and gold by employing a semipolymerized PDMS substrate to encapsulate the gold clusters/atoms during thermal deposition. The stability of the stretchable conductor is significantly enhanced based on the interlocking effect of metal and polymer, with high interfacial adhesion (>2 MPa) and cyclic stability (>10 000 cycles). Also, the conductor exhibits superior properties such as high stretchability (>130%) and large active surface area (>5:1 effective surface area/geometrical area). It is noted that this method can be easily used to fabricate such a stretchable conductor in a wafer‐scale format through a one‐step process. As a proof of concept, both long‐term implantation in an animal model to monitor intramuscular electric signals and on human skin for detection of biosignals are demonstrated. This design approach brings about a new perspective on the exploration of stretchable conductors for biomedical applications.
Thermal‐radiation‐assisted metal encapsulation is used to prepare large‐scale high‐performance stretchable conductors that possess high stretchability, stability and adhesion and large surface area. They are used to simultaneously monitor electromyography and skin deformation and implanted to detect intramuscular signals. This study offers a new path for highly stable stretchable conductors and related biointerface applications.
Efficient removal of interferents from complex matrices would significantly improve the performance of state of the art dipstick assays. Herein, we evaluate a graphitized carbon black ...(GCB)–incorporated dipstick, a configuration that has not been explored before, for reliable and facile on-site analysis of complex matrices. Carrot juice, a highly pigmented sample matrix, is chosen for evaluating the retention of interferents within the sorbent-incorporated cleanup pad on the dipstick. A peptide with a specific cleavage site for botulinum neurotoxin A light chain (BoNT/A LC), a model protease for validation of the proposed dipstick assay, is incubated with the test samples containing BoNT/A LC. Subsequently, the BoNT/A LC digested substrate and sample matrix flow vertically through the GCB-deposited cleanup pad within which the matrix interferents are captured, while the substrate, with a minimum of interferents, continues to flow toward a conjugation pad for labelling with Europium particles. Finally, the cleaved and uncleaved substrates flow toward a detection zone, where they bind to the test line producing a pinkish band which is not visible in the absence of GCB incorporation. The dipstick assay yields a LOD of 0.1 nM (5 ng/mL) of BoNT/A LC in carrot juice, within 20 min. The reported approach enables detection of proteases in a wide range of matrices upon incorporation of appropriate sorbents, ultimately aiming to exclude tedious laboratory-based sample pre-treatment protocols. Thus, merging extraction, cleanup, and pre-concentration steps with a sensitive optical detection approach is an attractive strategy for on-site assaying in complex matrices.
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