Self-Catalyzed Assembly of Peptide Scaffolded Nanozyme as a Dynamic Biosensing System

An extracellular matrix biosensing mimetic for evaluating cathepsin as a host target for COVID-19

To combat the new virus currently ravaging the whole world, every possible anti-virus strategy should be explored. As the main strategy of targeting the virus itself is being frustrated by the rapid mutation of the virus, people are seeking an alternative "host targeting" strategy: neutralizing proteins in the human body that cooperate with the virus. The cathepsin family is such a group of promising host targets, the main biological function of which is to digest the extracellular matrix (ECM) to clear a path for virus spreading. To evaluate the potential of cathepsin as a host target, we have constructed a biosensing interface mimicking the ECM, which can detect cathepsin from 3.3 pM to 33 nM with the limit of detection of 1 pM. Based on our quantitative analysis enabled by this biosensing interface, it is clear that patients with background diseases such as chronic inflammation and tumor, tend to have higher cathepsin activity, confirming the potential of cathepsin to serve as a host target for combating COVID-19 virus.

An electrochemical biosensor based on electroactive peptide nanoprobes for the sensitive analysis of tumor cells

Peptides possess many appealing and desirable features, which have attracted increasing attention in the field of electrochemical biosensing. However, peptides hardly produce noticeable electronic signals in response to target binding events. In this work, amphipathic peptides FFFGGGGRGDS with both target recognition and self-assembly capabilities are designed to be co-assembled with the electroactive species ferrocenecarboxylic acid (FcCOOH). Furthermore, the resultant electroactive peptide nanoprobes (ePNPs) are applied for sensitive electrochemical analysis of tumor cells. Specifically, tumor cells are captured by the electrode modified with the corresponding DNA aptamers, and ePNPs can then selectively bind to integrin proteins on the cell surface, thereby accompanied by a remarkable increase of electrochemical signal. Taking the assay of MDA-MB-231 cells, the fabricated biosensor can detect cancer cells with a detection limit of 7 cells mL^-1. Moreover, the ePNPs can act as a universal probe for the detection of different cell lines. Given the merits of easy synthesis, convenient operation, and favorable analytical performance, the proposed biosensor exhibits great potential in developing peptide-based electrochemical biosensing for clinical applications.

Dual-Active Au@PNIPAm Nanozymes for Glucose Detection and Intracellular H2O2 Modulation

As a nanozyme, gold nanoparticles have some advantages compared with natural enzymes, such as stable structure, adjustable catalytic activity, multifunctionality, and recyclability. Due to their special dimension, they are easy to aggregate rapidly and lose their catalytic performance when exposed to normal saline or special pH environment. To avoid such a situation, Au@PNIPAm nanozymes with core-shell structure are constructed and their mimic peroxidase and glucose oxidase enzymatic activities are investigated. Kinetic examinations manifest that Au@PNIPAm nanozymes exhibited a high affinity for 3,3,5,5-tetramethylbenzidine (TMB), hydrogen peroxide (H₂O₂), and glucose. These predominant peroxidase-like and glucose-like oxidase Au@PNIPAm catalytic activities are successfully used in the detection of H₂O₂ or glucose (LOD is 2.43 mM or 5.07 mM). Otherwise, the potential Au@PNIPAm nanozymes are provided with a clear ability for decomposing the intracellular H₂O₂ in living cells. And it could protect cells from oxidative stress damage with inducing by H₂O₂. Therefore, it is easy to consider that Au@PNIPAm nanozymes show a certain possibility to retard cell senescence and increase the production of the hydroxyl radical which could prevent carcinogenesis of the cell.

"Covalent biosensing" enables a one-step, reagent-less, low-cost and highly robust assay of SARS-CoV-2

We have established a new protocol for detecting severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) using a peptidomimetic to covalently detect a viral marker protease.

Effect of TTLL12 on tubulin tyrosine nitration as a novel target for screening anticancer drugs in vitro

Nitrotyrosine, a structural analogue of tyrosine, is present in cells in pathological conditions and is incorporated into tubulin to form tubulin tyrosine nitration, which disrupts the normal function of microtubules. There is limited research on the functional aspects of tubulin tyrosine nitration in different types of tumor. In the present study, the effect of tubulin tyrosine nitration and tubulin tyrosine ligase like 12 (TTLL12) on the proliferation of SCC-25 cells was investigated. TTLL12-overexpressing cell lines were constructed and used to assess the effect of tubulin tyrosine nitration and TTLL12 on the proliferation of SCC-25 cells via western blotting, immunofluorescent and MTT assays. An TTLL12-stably overexpressing SCC-25 cell line and the enzyme-linked immunosorbent assay were used to establish a novel experiment in vitro for screening anticancer drugs targeting tubulin tyrosine nitration by assessing its sensitivity, specificity and repeatability, and using it to find an effective drug. The results demonstrated that the proliferative rate of the control cells was notably inhibited in the presence of nitrotyrosine compared with that of TTLL12-overexpressing cells. The results of the MTT assay revealed that the proliferation of TTLL12-silenced cells was significantly inhibited compared with that of the control group. The sensitivity, specificity and repeatability of the experiment were positive. It was found that nocodazole could have better anticancer effect than paclitaxel. Taken together, the results of the present study suggest that TTLL12 enhances SCC-25 cell survival in the presence of nitrotyrosine by disrupting nitration of the tyrosine residues of tubulin, and tubulin tyrosine nitration may be developed for the basic research of anticancer drugs.

Enabling Molecular Gapping and Bridging on a Biosensing Surface via Electrochemical Cross-Linking and Cleavage

Protein detection in complicated biological samples requires robust design and a rigorous rinsing process. Many recently developed artificial targeting probes, however, often do not possess antibody-like binding strength that enables them to endure harsh biosensing conditions, and the classic 2-to-1 sandwich binding pattern is unavailable for many targets, often necessitating a complicated indirect signal conversion mechanism. Here, an attempt is made to provide innovative "covalent" solutions to such problems by employing peptide reactivity to form a covalent and robust biosensing structure upon target binding. Both the cross-coupling and cleavage of peptide chains are employed to achieve the classic 2-to-1 binding when only one targeting probe is available. Specifically, a targeting probe against the protein and a signaling probe are coimmobilized onto the sensing interface. The ratio between the two probes and their surface density is modulated so that direct cross-linking between the two immobilized probes is suppressed by the average distance between two such probes. Upon protein binding, the protein molecule may bridge that gap by itself. The signaling probe can carry any motif of signal amplification. And here a Cu-ion-complexed motif, which can exhibit peroxidase-like activity upon electrochemical agitation, is employed multipurposely as the catalyst for cross-linking, cleavage, and signal amplification. Three nonhomologous target proteins can be sensitively quantified in serum-spiked samples and clinical sample detection of one of them is also successful; these results suggest the potential of the proposed method in future clinical applications.

A novel signal self-enhancement photoelectrochemical immunosensor without addition of a sacrificial agent in solution based on Ag2S/CuS/α-Fe2O3 n–p–n heterostructure films

A novel signal self-enhancement photoelectrochemical immuno-sensor has been developed based on the curing of sacrificial agent SO₃²⁻ coated-Au NPs sensitizing Ag₂S/CuS/α-Fe₂O₃ n–p–n hetero-structure films for the first time.

Platelet-driven formation of interface peptide nano-network biosensor enabling a non-invasive means for early detection of Alzheimer's disease

Soft material fabricated with DNA origami or peptide cross-linking technique may be promising theranostic platforms in the future; however, their naturally occurring counterparts, such as the peptide aggregates in the neurodegenerative diseases, constitute an increasingly burdensome issue of public health. Thus, a design of artificial peptide nano-network biosensor is conceived, in an attempt to combat the natural pathological peptides, by mimicking their pathogenesis process. Specifically, periphery platelet can secrete A-beta and induce its cross-linking & aggregation to form a surface peptide nano-network, resulting in large numbers of poly-tyrosine strands being covalently trapped in the network to serve as an efficient signal amplifier, through the electrochemical oxidation of tyrosine. This method is sensitive and quantitative in the range of normal and pathological periphery platelet distribution and can effectively discriminate Alzheimer's disease (AD) patients based on the detected potential neurodegenerative activity of platelet. These results may point to some future perspective of this method in the early screening of AD.

A dopamine-induced Au hydrogel nanozyme for enhanced biomimetic catalysis

Due to porous nanostructure and polydopamine-induced interfacial electron transfer effects, Au hydrogel nanozyme exhibits enhanced glucose oxidase-like and peroxidase-like activities, with a biomimetic cascade catalysis.

Nanozyme-based bio-barcode assay for high sensitive and logic-controlled specific detection of multiple DNAs

Since HCV and HIV share a common transmission path, high sensitive detection of HIV and HCV gene is of significant importance to improve diagnosis accuracy and cure rate at early stage for HIV virus-infected patients. In our investigation, a novel nanozyme-based bio-barcode fluorescence amplified assay is successfully developed for simultaneous detection of HIV and HCV DNAs with excellent sensitivity in an enzyme-free and label-free condition. Here, bimetallic nanoparticles, PtAu_NPs, present outstanding peroxidase-like activity and act as barcode to catalyze oxidation of nonfluorescent substrate of amplex red (AR) into fluorescent resorufin generating stable and sensitive "Turn On" fluorescent output signal, which is for the first time to be integrated with bio-barcode strategy for fluorescence detection DNA. Furthermore, the provided strategy presents excellent specificity and can distinguish single-base mismatched mutant from target DNA. What interesting is that cascaded INHIBIT-OR logic gate is integrated with biosensors for the first time to distinguish individual target DNA from each other under logic function control, which presents great application in development of rapid and intelligent detection.

Structural and Mechanical Properties of Amyloid Beta Fibrils: A Combined Experimental and Theoretical Approach

In this combined experimental (deep ultraviolet resonance Raman (DUVRR) spectroscopy and atomic force microscopy (AFM)) and theoretical (molecular dynamics (MD) simulations and stress-strain (SS)) study, the structural and mechanical properties of amyloid beta (Aβ40) fibrils have been investigated. The DUVRR spectroscopy and AFM experiments confirmed the formation of linear, unbranched and β-sheet rich fibrils. The fibrils (Aβ40)n, formed using n monomers, were equilibrated using all-atom MD simulations. The structural properties such as β-sheet character, twist, interstrand distance, and periodicity of these fibrils were found to be in agreement with experimental measurements. Furthermore, Young's modulus (Y) = 4.2 GPa computed using SS calculations was supported by measured values of 1.79 ± 0.41 and 3.2 ± 0.8 GPa provided by two separate AFM experiments. These results revealed size dependence of structural and material properties of amyloid fibrils and show the utility of such combined experimental and theoretical studies in the design of precisely engineered biomaterials.