Application In Label-free Detection Research Articles

Bio-Tailored Sensing at the Nanoscale: Biochemical Aspects and Applications.

The demonstration of the first enzyme-based electrode to detect glucose, published in 1967 by S. J. Updike and G. P. Hicks, kicked off huge efforts in building sensors where biomolecules are exploited as native or modified to achieve new or improved sensing performances. In this growing area, bionanotechnology has become prominent in demonstrating how nanomaterials can be tailored into responsive nanostructures using biomolecules and integrated into sensors to detect different analytes, e.g., biomarkers, antibiotics, toxins and organic compounds as well as whole cells and microorganisms with very high sensitivity. Accounting for the natural affinity between biomolecules and almost every type of nanomaterials and taking advantage of well-known crosslinking strategies to stabilize the resulting hybrid nanostructures, biosensors with broad applications and with unprecedented low detection limits have been realized. This review depicts a comprehensive collection of the most recent biochemical and biophysical strategies for building hybrid devices based on bioconjugated nanomaterials and their applications in label-free detection for diagnostics, food and environmental analysis.

The role of band structure in Co- and Fe-co-doped Ba0.5Sr0.5Zr0.1Y0.1O3-δ perovskite semiconductor to design an electrochemical aptasensing platform: application in label-free detection of ochratoxin A using voltammetry.

Nanocomposites can offer a platform to conjugate biorecognition features of aptamer with unique size-dependent properties of a given material, which can autoprobe the binding event based on their electroactive characteristics. Herein, we design electroactive switchable aptamer probes based on co-doped single-phase semiconducting materials employing the cyclic voltammetry method to record the current signal at each step of electrochemical characterization. To do so, we utilized a facile hydrothermal method assisted by co-precipitation method such as Co-Fe-co-doped Ba0.5Sr0.5Zr0.1Y0.1O3-δ (CF-BSZY) and tuned the alignment of the energy band structure of the material to amplify the output of theelectrochemical signal. Atvarious steps, changes occurred in the electrochemical properties at the surface of CF-BSZY. The binding of the ssDNA with prepared materials enhances the current signal by the interaction with the target (ochratoxin A (OTA)) depressing the current signal and facilitating the construction of a novel design of electrochemical aptasensor. As a proof of concept, an electrochemical aptasensor for the detection of ochratoxin A (OTA) in rice samples has been developed. The electrochemical aptasensor provides a limit of detection (LOD) of 0.00012μM (0.12nM), with a linear range from 0.000247 to 0.74μM and sound OTA recovery in real samples. The developed aptasensor is simply designed andis free of oligonucleotide labeling or decorative nanoparticle modifications. The proposed mechanism is generic in principle with the potential to translate any type of aptamer and target binding event into a detectable signal; hence, it can be largely applied to various bioreceptor recognition phenomena for subsequent applications.

Ordering Transitions in Liquid Crystals Triggered by Bioactive Cyclic Amphiphiles: Potential Application in Label-Free Detection of Amyloidogenic Peptides

We report the orientational behavior of nematic liquid crystals (LCs) influenced by a cyclic lipopeptide, polymyxin B (PmB). It was found that PmB can spontaneously self-assemble at aqueous-LC interfaces and induce a homeotropic ordering of the LCs at those interfaces, thus resulting in dark optical appearance of the LC under cross polarizers. Density functional theory studies substantiate the experimental findings that the stability of homeotropic anchoring of the LC is strongly influenced by the hydrophobic interactions between aliphatic tails of PmB and LC molecules along with the additional supramolecular interactions between their head groups. Interestingly, exposure of the PmB-laden aqueous-LC interface to anionic serum proteins such as bovine serum albumin (BSA) and human hemoglobin triggered a planar reorientation of the LC, leading to a bright optical state of the LC. This allows label-free characterization of the biomolecular interactions between proteins and antibiotics (i.e., PmB) in vitro at ...

Nickel Nanowires Combined with Surface-Enhanced Raman Spectroscopy: Application in Label-Free Detection of Cytochrome c-Mediated Apoptosis.

Intrinsic properties of nickel have enabled its wide applications as an effective catalyst. In this study, nickel nanowires (Ni NWs) as electron donors for oxidized cytochrome c (Cyt c) are investigated, which are NW diameter, temperature, and pH value-dependent. The reductive and magnetic properties facilitate the Ni NWs to rapidly and conveniently reduce Cyt c in complicated biological samples. Moreover, we find that the Ni NWs combined with resonance Raman spectroscopy have specificity toward Cyt c detection in real biological samples, which is successfully used to distinguish the redox state of the released Cyt c from isolated mitochondria in apoptotic Hela cells. Moreover, rapid label-free Cyt c quantification can be achieved by surface-enhanced Raman spectroscopy with a limit of detection of 1 nM and long concentration linear range (1 nM-1 μM). The proposed Ni NWs-based reduction approach will significantly simplify the traditional biological methods and has great potential in the application of Cyt c-related apoptotic studies.

Junctionless based dielectric modulated electrically doped tunnel FET based biosensor for label‐free detection

The fabrication complexity and cost effectiveness in nanoscale regime have been one of the major issues in the modern biosensor. Therefore, to overcome such issue, this study investigates a junctionless dielectrically modulated electrically doped tunnel field effect transistor (FET) as a biosensor for application of label free detection. In this work, the authors have been considered the n + heavily doped silicon layer and two isolate gates for the formation of intrinsic and p + source regions underneath the control gate (CG) and polarity gate (PG) with appropriate work functions and polarity bias over silicon body which are similar to that of conventional tunnel FET. The proposed device structure is immune against doping control issues, avoids thermal budget, and fabrication issues. Moreover, the formation of nanogap cavity embedded within the CG dielectric is performed by etching of CG dielectric region towards the PG side for the purpose of sensing the biomolecules. The sensing ability of the proposed device has been evaluated in terms of varying the dielectric constant and charge density of the biomolecules. However, transfer characteristics are also evaluated with the variation in thickness and length of the cavity. All the simulations have been performed using ATLAS technology computer aided design device simulator.

Dielectric-Modulated Impact-Ionization MOS Transistor as a Label-Free Biosensor

In this letter, we propose a dielectric-modulated impact-ionization MOS (DIMOS) transistor-based sensor for application in label-free detection of biomolecules. Numerous reports exist on the experimental demonstration of nanogap-embedded field effect transistor-based biosensors, but an impact-ionization MOS (I-MOS)-based biosensor has not been reported previously. The concept of a dielectric-modulated I-MOS-based biosensor is presented in this letter based on technology computer-aided design simulation study. The results show a high sensitivity to the presence of biomolecules even at small channel lengths. In addition, a low variability of the sensitivity to the charges on the biomolecule is observed. The high sensitivity, dominance of dielectric-modulation effects, and operation at even small channel lengths make the DIMOS biosensor a promising alternative for CMOS-based sensor applications.

Construction of logic gates with the fluorene-based small molecule/DNA probes

Fluorene-based small molecules (FSMs) have optical properties and can interact with DNA. In this paper, the integrated "INH" and "AND" gates operating in parallel are developed with the fluorene-based small molecule (FSM)/DNA probe. They are activated by taking advantage of the two-step fluorescence resonance energy transfer (FRET) process and the sequence-recognition mechanism of DNA. Then, a "NOT" gate is obtained with a molecular beacon-like probe (FSM-MB) by using the FSM as the fluorophore. Moreover, the "NOT" gate based on the FSM-MB probe can be used as a biosensor and has potential applications in label-free detection of target molecules.

A high-density poly(ethylene glycol) polymer brush for immobilization on glass-type surfaces

Label-free heterogeneous phase detection critically depends on the properties of the interfacial layer. We have obtained high-density monomolecular poly(ethylene glycol) (PEG) layers by solvent-free coupling of homo-bifunctional PEGs (2000 g/mol) at 75°C to silica surfaces silanized with glycidyloxipropyltrimethoxysilane (GOPTS). Characterization by ellipsometry and contact angles revealed that PEG layers up to 3.4 ng/mm 2 with low roughness and flexibility were obtained. Specific and non-specific binding at these PEG surfaces was monitored by reflectometric interference spectroscopy (RIfS). No significant non-specific adsorption upon incubation of 1 mg/ml ovalbumin was detectable (<10 pg/mm 2), and 150 pg/mm 2 upon incubation of 10% calf serum, less than 10% of the amount adsorbed to the solely silanized surfaces. The terminal functional groups of the PEG layers were utilized to couple ligands and a protein. Specific protein interaction with these immobilized compounds was detected with saturation loadings in the range of protein monolayers (2–4 ng/mm 2). The excellent functional properties, the high stability of the layers, the generic and practical coupling procedure and the versatility for immobilizing compounds of very different functionality make these PEG layers very attractive for application in label-free detection with silica or metal-oxide based transducers.