Microarray-based Raman spectroscopic assay for kinase inhibition by gold nanoparticle probes

Biomedical applications of peptide-gold nanoarchitectonics

Gold nanoparticles (AuNPs) have become a focus of interest in biomedicine due to their unique properties. By attaching peptides to these nanoparticles (NPs), they can be utilized for a wide range of applications. Peptides, which are short chains of amino acids, can be customized for specific molecular interactions, making them ideal for delivering AuNPs to particular cells or tissues. One of the peptide-AuNP-based bio-nano technological approaches involves targeted drug delivery. Including peptides as targeting agents, these NPs can be designed to bind to specific cell receptors or biomarkers. This allows for the direct delivery of therapeutic agents to diseased cells while minimizing unwanted side effects, improving the effectiveness of treatments. Additionally, peptide-functionalized AuNPs (PAuNPs) are crucial for imaging and diagnostics. By functionalizing the NPs with peptides that bind to specific molecular targets, such as cancer biomarkers, these NPs can be used to visualize diseased tissues. This enables the early detection of diseases and helps in determining the severity of conditions for better diagnosis and treatment outcomes. Moreover, PAuNPs have displayed promising potential in photothermal therapy. Once PAuNPs uptake and penetrate target cancer cells effectively, these NPs generate heat when exposed to specific wavelengths of light, efficiently eliminating tumors while preserving healthy surrounding tissues. Therefore, in this paper, we systematically review the potential of PAuNPs in various biomedical applications, including therapy and diagnosis, providing a future perspective.

Recent Progress in Fluorescent Chemosensors for Protein Kinases

Protein kinases are involved in almost all biological activities. The activities of different kinases reflect the normal or abnormal status of the human body. Therefore, detecting the activities of different kinases is important for disease diagnosis and drug discovery. Fluorescent probes offer opportunities for studying kinase behaviors at different times and spatial locations. In this review, we summarize different kinds of fluorescent chemosensors that have been used to detect the activities of many different kinases.

Two-Dimensional Metalloporphyrinic Framework Nanosheet-Based Dual-Mechanism-Driven Ratiometric Electrochemiluminescent Biosensing of Protein Kinase Activity

A dual-mechanism-driven ratiometric electrochemiluminescent (ECL) biosensor was developed for the ultrasensitive detection of protein kinase activity, which was based on a competitive catalytic reaction and resonance energy transfer (RET) by assembling gold nanoparticles (GNPs) on two-dimensional (2D) porphyrinic metal-organic framework (MOF) nanosheets. In this work, an ECL catalytic reaction competing for dissolved O₂ proceeded between 2D copper-based zinc porphyrinic MOF (Cu-TCPP(Zn)) nanosheets and luminol. Meanwhile, the cathodic ECL of singlet oxygen (¹O₂), derived from the electrocatalytic reaction of 2D Cu-TCPP(Zn), would be reduced by the assembled GNPs due to RET, while the anodic emission of luminol could be enhanced by GNPs with excellent electrocatalytic activity. With the detection of protein kinase A (PKA) as an example, this dual-mechanism-driven ECL biosensor exhibited a broad linear range (0.005-5.0 U mL^-1) and a sensitive detection limit (0.0037 U mL^-1). Compared with the traditional single-mechanism-driven sensing strategies, the developed dual-mechanism-driven ratiometric ECL biosensor may provide an effective method for the design of green and ultrasensitive ECL sensors.

Rational Design of Functional Peptide-Gold Hybrid Nanomaterials for Molecular Interactions

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.

Photoelectrochemical biosensor for protein kinase A detection based on carbon microspheres, peptide functionalized Au-ZIF-8 and TiO2/g-C3N4

In this work, a novel and sensitive photoelectrochemical (PEC) strategy was designed for protein kinase A (PKA) detection, comprising carbon microsphere (CMS) modified ITO electrode, TiO₂ as the phosphate group recognition material and graphite-carbon nitride (g-C₃N₄) as photoactive material. For the first time, gold nanoparticle decorated zeolitic imidazolate frameworks (Au-ZIF-8) was employed to fabricate biosensor for PKA activity assay with the function of substrate peptide immobilization and signal amplification. Firstly, substrate peptides were assembled on the Au-ZIF-8/CMS/ITO surface through the covalent bonding between the gold nanoparticles (AuNPs) and sulfydryl groups of the peptides. Then, in the presence of ATP, phosphorylation of the substrate peptide was achieved under PKA catalysis. Finally, TiO₂-g-C₃N₄ composites were further modified on the electrode surface based on bonding between TiO₂ and phosphate groups created via phosphorylation of the peptide (yielding TiO₂-g-C₃N₄/P-peptide/Au-ZIF-8/CMS/ITO), which is different with our previous work by directly immobilizing g-C₃N₄ composite on electrode surface. The developed method showed a wide linear range from 0.05-50 U mL^-1. The detection limit was 0.02 U mL^-1 (S/N = 3). The constructed biosensor exhibited high detection specificity for PKA. In addition, the wide applicability of this biosensor was demonstrated by evaluating the inhibition ability of ellagic acid towards PKA.

Rational design of an anchoring peptide for high-efficiency and quantitative modification of peptides and DNA strands on gold nanoparticles

The pentapeptide Cys-Ala-Leu-Asn-Asn (CALNN) could stabilize gold nanoparticles (AuNPs), most of which serve as anchoring blocks for various bioanalyses by introducing recognition blocks. However, the typical conjugation strategy greatly suffers from excessive use of peptides, overnight incubation and consequently low efficiency. In this study, new design criteria for the efficacious anchor were established. In addition, a stable, instantaneous and effective modification of the anchoring peptide RRFPDD or its derivatives on AuNPs is first proposed for the first time. With low consumption of peptides (50 μM), the loading process could be realized in 100 seconds. The anchor RRFPDD also allowed for the quantitative adsorption of appended recognition blocks (e.g., peptides or DNAs), thus adjusting their proportions for better performance. In particular, the biological characteristics of those recognition blocks were fully retained. Furthermore, the anchor RRFPDD contributed to a time-saving and high-efficiency (85%) hydrolysis of peptide-capped AuNPs. Considering these advantages of the new anchor, a reliable assay for cardiac troponin I (cTnI) was developed with a detection limit as low as 0.45 ng mL-1, and also successfully applied in human serum samples.

Simple fluorescence-based detection of protein kinase A activity using a molecular beacon probe

Protein kinase A was detected by quantifying the amount of ATP used after a protein kinase reaction. The ATP assay was performed using the T4 DNA ligase and a molecular beacon (MB). In the presence of ATP, DNA ligase catalyzed the ligation of short DNA. The ligation product then hybridized to MB, resulting in a fluorescence enhancement of the MB. This assay was capable of determining protein kinase A in the range of 12.5∼150 nM, with a detection limit of 1.25 nM. Furthermore, this assay could also be used to investigate the effect of genistein on protein kinase A. It was a universal, non-radioisotopic, and homogeneous method for assaying protein kinase A.

Zirconium-metalloporphyrin frameworks as a three-in-one platform possessing oxygen nanocage, electron media, and bonding site for electrochemiluminescence protein kinase activity assay

A Zr-based metal-organic framework with zinc tetrakis(carboxyphenyl)-porphyrin (ZnTCPP) groups (MOF-525-Zn) was utilized to develop a novel electrochemiluminescence (ECL) biosensor for highly sensitive protein kinase activity assay. In this work, in terms of ECL measurements and cyclic voltammetry, the cathodic ECL behaviors of MOF-525-Zn in aqueous media were thoroughly investigated for the first time. The photoelectric active groups ZnTCPP on the MOF-525-Zn frameworks could promote the generation of singlet oxygen ((1)O2) via a series of electrochemical and chemical reactions, resulting in a strong and stable red irradiation at 634 nm. Additionally, the surfactant tetraoctylammonium bromide (TOAB) further facilitated dissolved oxygen to interact with the active sites ZnTCPP of MOF-525-Zn. Furthermore, the inorganic Zr-O clusters of MOF-525-Zn were simultaneously served as the recognition sites of phosphate groups. And then, an ultrasensitive ECL sensor was proposed for protein kinase A (PKA) activity detection with a linear range from 0.01 to 20 U mL(-1) and a sensitive detection limit of 0.005 U mL(-1). This biosensor can also be applied for quantitative kinase inhibitor screening. Finally, it exhibits good performance with high stability and acceptable fabrication reproducibility, which provide a valuable strategy for clinic diagnostics and therapeutics.

Raman-based microarray readout: a review

For a quarter of a century, microarrays have been part of the routine analytical toolbox. Label-based fluorescence detection is still the commonest optical readout strategy. Since the 1990s, a continuously increasing number of label-based as well as label-free experiments on Raman-based microarray readout concepts have been reported. This review summarizes the possible concepts and methods and their advantages and challenges. A common label-based strategy is based on the binding of selective receptors as well as Raman reporter molecules to plasmonic nanoparticles in a sandwich immunoassay, which results in surface-enhanced Raman scattering signals of the reporter molecule. Alternatively, capture of the analytes can be performed by receptors on a microarray surface. Addition of plasmonic nanoparticles again leads to a surface-enhanced Raman scattering signal, not of a label but directly of the analyte. This approach is mostly proposed for bacteria and cell detection. However, although many promising readout strategies have been discussed in numerous publications, rarely have any of them made the step from proof of concept to a practical application, let alone routine use. Graphical Abstract Possible realization of a SERS (Surface-Enhanced Raman Scattering) system for microarray readout.

Kinase phosphorylation monitoring with i-motif DNA cross-linked SERS probes

We propose an ultrasensitive SERS-based peptide biosensor platform to monitor phosphorylation catalyzed by kinase in a dynamic format. The developed SERS strategy has a short response time with potential to monitor phosphorylation in live cells.

Water-Mediated Assembly of Gold Nanoparticles into Aligned One-Dimensional Superstructures

This Article shows that water in ethanol colloids of gold nanoparticles enhances the formation of linear clusters and, more important for applications in electronics, determines their assembly on surfaces. We show by dynamic light scattering that ethanol colloids contain mainly monomers and dimers and that wormlike superstructures are mostly absent, despite UV-vis evidence of aggregation. Water added to the colloid as a cosolvent was found to enhance the number of clusters as well as their average size, confirming its role in linear self-assembly, on the scale of a few particles. Water adsorbed from the atmosphere during coating was also found to be a powerful lever to tune self-assembly on surfaces. By varying the relative humidity, a sharp transition from branched to linear superstructures was observed, showing the importance of water as a cosolvent in the formation of cluster superstructures. We show that one-dimensional superstructures may form due to long-range mobility of precursor clusters on wet surfaces, allowing their rearrangement. The understanding of the phenomenon allows us to statistically align both clusters and resulting superstructures on patterned substrates, opening the way to rapid screening in molecular electronics.

Label and Label-Free Detection Techniques for Protein Microarrays

Protein microarray technology has gone through numerous innovative developments in recent decades. In this review, we focus on the development of protein detection methods embedded in the technology. Early microarrays utilized useful chromophores and versatile biochemical techniques dominated by high-throughput illumination. Recently, the realization of label-free techniques has been greatly advanced by the combination of knowledge in material sciences, computational design and nanofabrication. These rapidly advancing techniques aim to provide data without the intervention of label molecules. Here, we present a brief overview of this remarkable innovation from the perspectives of label and label-free techniques in transducing nano-biological events.

Determination of the sodium 2-mercaptoethanesulfonate based on surface-enhanced Raman scattering

Based on the surface-enhanced Raman scattering (SERS) sodium 2-mercaptoethanesulfonate (mesna) was determined using unmodified gold colloid as the probe. The Raman scattering intensity was obviously enhanced in the presence of sodium chloride. The influence of experimental parameters, such as incubation time, sodium chloride concentration and pH value on SERS performance was examined. Under the optimum conditions, the SERS intensity is proportional to the concentration of mesna in the range of 9.0×10(-8) to 9.0×10(-7) mol/L and detection limit (S/N=3) is 1.16×10(-8) mol/L. The corresponding correlation coefficient of the linear equation is 0.996, which indicates that there is a good linear relationship between SERS intensity and mesna concentration. The experimental results indicate that the proposed method is a viable method for determination of mesna. The real samples were analyzed and the results obtained were satisfactory.

Role of salt in the spontaneous assembly of charged gold nanoparticles in ethanol

This paper investigates the role of salt in the spontaneous linear assembly of charged gold nanoparticles in ethanol and attempts to clear up a misunderstanding on the role of ethanol in this process. Many prior reports have noted that the addition of ethanol to an aqueous solution of gold nanoparticles causes their aggregation into linear assemblies. It was therefore believed that ethanol plays the determining role during the assembly process. In this work, we carried out systematic studies which indicate that residual salt in conjunction with ethanol, instead of ethanol itself, induces the assembly of gold nanoparticles in ethanol. In the absence of salt, gold nanoparticles can be well dispersed in an ethanol solution. Furthermore, we find that the chainlike assemblies can disassemble upon dilution of the salt or the evaporation of ethanol if the gold nanoparticles are protected with a sufficiently strong ligand.

Controlled synthesis and biomolecular probe application of gold nanoparticles

In addition to their optical properties, the ability of gold nanoparticles (Au NPs) to generate table immobilization of biomolecules, whilst retaining their bioactivities is a major advantage to apply them as biosensors. Optical biosensors using Au NPs are simple, fast and reliable and, recently, they have been moving from laboratory study to the point of practical use. The optical properties of Au NPs strongly depend on their size, shape, degree of aggregation and the functional groups on their surface. Rapid advances in the field of nanotechnology offer us a great opportunity to develop the controllable synthesis and modification of Au NPs as well as to study on their properties and applications. The size-controlled growth of Au NPs requires the isotropic growth on the surface of Au nuclei whereas anisotropic growth will induce the formation of Au NPs of varying shape. Functionalized Au NPs provide sensitive and selective biosensors for the detection of many targets, including metal ions, small organic compounds, protein, DNA, RNA and cell based on their optical, electrical or electrochemical signals. In this review, we will discuss the size- and shape-controlled growth and functionalization of Au NPs to obtain Au nanoprobes. The basis of the optical detection of Au nanoprobes and their applications in nucleic acid, protein detection and cell imaging are also introduced.

Highly reproducible immunoassay of cancer markers on a gold-patterned microarray chip using surface-enhanced Raman scattering imaging

This paper reports a highly reproducible immunoassay of cancer markers using surface-enhanced Raman scattering (SERS) imaging. SERS is a highly sensitive detection method but it is limited in its ability to achieve reproducible signal enhancement because of the difficulty with precisely controlling the uniform distribution of hot junctions. Consequently, inconsistent enhancement prevents the wide exploitation of SERS detection as a bio-detection tool for quantitative analysis. To resolve this problem, we explored the use of a SERS imaging-based immunoassay. For this purpose, Raman reporter-labeled hollow gold nanospheres (HGNs), were manufactured and antibodies were immobilized onto their surfaces for targeting specific antigens. After the formation of sandwich immunocomplexes using these functional HGNs on the surfaces of gold patterned wells, the SERS mapping images were measured. For target protein markers, 12×9 pixels were imaged using a Raman mapping technique in the 0-10(-4) g/mL concentration range, and the SERS signals for 66 pixels were averaged. Here, the SERS imaging-based assay shows much better correlations between concentration and intensity than does the conventional point-based assay. The limits of detection were determined to be 0.1 pg/mL and 1.0 pg/mL for angiogenin (ANG) and alpha-fetoprotein (AFP), respectively. This detection sensitivity is increased by three or four orders of magnitude over that of conventional ELISA method. The detectable dynamic range for SERS imaging (10(-4)-10(-12) g/mL) is also much wider than that for ELISA (10(-6)-10(-9) g/mL).

Gold nanoparticle-based colorimetric assay for selective detection of aluminium cation on living cellular surfaces

A colorimetric assay based on pentapeptide (CALNN) functionalized gold nanoparticles exhibits high sensitivity and selectivity for detection of aluminium cation (Al(3+)) both in aqueous solution and on living cellular surfaces under physiological condition.