Fluorescent Peptide Beacons for the Selective Ratiometric Detection of Heparin

Photocatalysed C-H amidation of indoles enabled by tert-butyl alkyl((perfluoropyridin-4-yl)oxy)carbamate

Development of a new catalytic and straightforward strategy to construct C-N bonds is playing a pivotal role in synthetic chemistry. Here, we report a photocatalysed protocol to access direct C-H amidation of indoles, enabled by a rationally designed tert-butyl alkyl((perfluoropyridin-4-yl)oxy)carbamate. A series of biologically important aminoindoles were prepared under mild conditions with excellent regioselectivity and broad substrate scope.

Pyrene-Based Self-Assembling Peptide for Ratiometric Detection of Heparin

Heparin is a commonly used anticoagulant in clinical practice; however, excessive heparin can cause serious adverse reactions. Convenient and accurate detection of heparin levels is thus very important. In this research, a pyrene-based self-assembling fluorescent peptide PyFFRRR was designed for simple, selective, and efficient heparin detection. The guanidine groups in the arginine residues of PyFFRRR bind tightly with heparin, which is highly sulfated, through electrostatic interactions. Charge neutralization facilitated the self-assembly of PyFFRRR, resulting in its spectral response changing from deep blue monomer fluorescence to green excimer fluorescence. PyFFRRR exhibited excellent sensitivity and selectivity for ratiometric detection of heparin. The binding mechanism was investigated by using spectral and simulation tools, and structural observation. Finally, PyFFRRR was employed in human serum samples for ratiometric detection of heparin.

Pharmacology of Heparin and Related Drugs: An Update

Heparin has been used extensively as an antithrombotic and anticoagulant for close to 100 years. This anticoagulant activity is attributed mainly to the pentasaccharide sequence, which potentiates the inhibitory action of antithrombin, a major inhibitor of the coagulation cascade. More recently it has been elucidated that heparin exhibits anti-inflammatory effect via interference of the formation of neutrophil extracellular traps and this may also contribute to heparin's antithrombotic activity. This illustrates that heparin interacts with a broad range of biomolecules, exerting both anticoagulant and nonanticoagulant actions. Since our previous review, there has been an increased interest in these nonanticoagulant effects of heparin, with the beneficial role in patients infected with SARS2-coronavirus a highly topical example. This article provides an update on our previous review with more recent developments and observations made for these novel uses of heparin and an overview of the development status of heparin-based drugs. SIGNIFICANCE STATEMENT: This state-of-the-art review covers recent developments in the use of heparin and heparin-like materials as anticoagulant, now including immunothrombosis observations, and as nonanticoagulant including a role in the treatment of SARS-coronavirus and inflammatory conditions.

The heparinase-linked differential time method allows detection of heparin potency in whole blood with high sensitivity and dynamic range

Anticoagulation therapy with heparin is an effective treatment against thrombosis. Heparin tends to cause spontaneous bleeding and requires regular monitoring during therapy. Most high-sensitivity heparin sensors have focused on the concentration detection in clarified buffer solution. However, the pharmacodynamics of heparin vary depending on individual patient or disease, while potency detection with high sensitivity and dynamic range outperforms concentration detection in clinical diagnosis. In this study, a novel heparinase-linked differential time (HLDT) method was established with a two-zone of Graphene modified Carbon (GR-C) sensor, which was utilized to evaluate heparin potency in whole blood. It was based on electrochemical measurement of clotting time shifting associated with presence or absence of heparinase. Heparinase inhibits the anticoagulant ability of heparin by forming a heparin-antithrombin-thrombin complex during coagulation. And the intensity and peak time of electrochemical current were associated with thrombin activity and clotting on the electrode. The results demonstrated that the sensor had high selectivity for heparin potency in 10 μL of whole blood with a detection limit of 0.1 U/mL, and the linear detection range was 0.1-5 U/mL. The coefficient of variation (CV) of the peak time was less than 5%, and linear correlation between the GR-C sensor and the TEG-5000 instrument was 0.987. Thus, the HLDT method has better clinical application due to its good repeatability, high sensitivity and wide range in heparin potency evaluation.

Terminal protection of peptides by interactions with proteins: A "signal-on" peptide-templated gold nanocluster beacon for label-free protein detection

Characterization of the protein-peptide interactions are a critical for understanding the functions and signal pathways of proteins. Herein, a new finding of universal terminal protection that protein bind specifically with peptide and provide a protective coating to prevent peptide hydrolysis in the presence of peptidase. On the basis of this mechanism, we first reported a novel label-free fluorescence biosensor strategy that utilizes the protection of specific terminal protein on peptide-templated gold nanocluster (AuNCs) beacon for the detection of proteins. The fluorescence quenching of peptide-templated AuNCs can be effectively inhibited with increasing concentration of the specific protein, exhibiting a satisfactory sensitivity and selectivity toward protein with the detection limit of MDM2 and gp120 are 0.0019 U/mL and 0.0012 U/mL, respectively. The developed label-free fluorescence biosensor strategy provides new ideas to detect and screen protein for analyzing protein-peptide interaction in biomedical applications.

Selected peptide-based fluorescent probes for biological applications

To understand the molecular interactions, present in living organisms and their environments, chemists are trying to create novel chemical tools. In this regard, peptide-based fluorescence techniques have attracted immense interest. Synthetic peptide-based fluorescent probes are advantageous over protein-based sensors, since they are synthetically accessible, more stable, and can be easily modified in a site-specific manner for selective biological applications. Peptide receptors labeled with environmentally sensitive/FRET fluorophores have allowed direct detection/monitoring of biomolecules in aqueous media and in live cells. In this review, key peptide-based approaches for different biological applications are presented.

Selective recognition of ATP by multivalent nano-assemblies of bisimidazolium amphiphiles through "turn-on" fluorescence response

Bisimidazolium receptors, tagged with chromophoric pyrene at one end and linked to an n-alkyl chain at the other, underwent self-assembly in aqueous media depending on the length of the alkyl segment. The amphiphilic derivatives having n-decyl or longer chains, formed nano-assemblies with cyanic-green emission resulting from the stacked pyrene chromophores in the aggregates. The presence of positive surface charges on the multivalent aggregates led to ATP binding which was accompanied by a significant increase in the excimeric emission intensity. This provided a convenient way of monitoring ATP binding in a "turn-on" mode and an efficient detection of ATP was achieved in aqueous buffer and also in buffer containing 150 mM NaCl at physiological pH value. Furthermore, the multivalent aggregates demonstrated a significant selectivity in ATP detection over ADP, AMP and pyrophosphate.

Chemical sensors for selective and quantitative heparin sensing

In this review article, chemical sensors for selective and quantitative heparin sensing are discussed with detailed examples.

A Selective Cucurbit[8]uril-Peptide Beacon Ensemble for the Ratiometric Fluorescence Detection of Peptides

A convenient supramolecular strategy for constructing a ratiometric fluorescent chemosensing ensemble, consisting of a macrocyclic host (cucurbit[8]uril CB[8]), and a pyrene-tagged amphiphilic peptide beacon (AP 1), is reported. AP 1 unfolds upon encapsulation of the pyrene termini into the hydrophobic CB[8] cavity. This changes pyrene excimer to monomer emission. Substrates with higher affinity for the CB[8] cavity can displace AP 1 from the ensemble. The released AP 1 folds again to form a pyrene excimer, which allows for the ratiometric fluorescence monitoring of the substrate. In this report, the ensemble capacity for ratiometric fluorescence monitoring of biological substrates, such as amino acid derivatives, specific peptides, and proteins, in aqueous media is demonstrated.

Arginine mimetic appended peptide-based probes for fluorescence turn-on detection of 14-3-3 proteins

Development of fluorescence markers for the 14-3-3 adapter protein class.

Sensing, Transport and Other Potential Biomedical Applications of Pseudopeptides

Pseudopeptides are privileged synthetic molecules built from the designed combination of peptide-like and abiotic artificial moieties. Consequently, they are benefited from the advantages of both families of chemical structures: modular synthesis, chemical and functional diversity, tailored three-dimensional structure, usually high stability in biological media and low non-specific toxicity. Accordingly, in the last years, these compounds have been used for different biomedical applications, ranging from bio-sensing, ion transport, the molecular recognition of biologically relevant species, drug delivery or gene transfection. This review highlights a selection of the most remarkable and recent advances in this field.

Facile synthesis of near-infrared emitting dBSA-templated Cu nanoclusters for sensitive detection of heparin

The near-infrared emitting dBSA-Cu NCs were synthesized through a facile synthesis route and were applied for ultra-sensitive detection of heparin in human plasma.

Peptide-Based Probes with an Artificial Anion-Binding Motif for Direct Fluorescence "Switch-On" Detection of Nucleic Acid in Cells

This work reports two new peptide-based fluorescence probes (1 and 2) for the detection of ds-DNA at physiological pH. Probes 1 and 2 contain a fluorophore, either amino-naphthalimide or diethyl-aminocoumarin, respectively, and two identical peptide arms each equipped with a guanidiniocarbonylpyrrole (GCP) anion-binding motif. These probes show "switch-on" fluorescence response upon binding to ds-DNA, whereby they can differentiate between various types of polynucleotides. For instance, they exhibit more pronounced fluorescence response for AT-rich polynucleotides than GC-rich polynucleotides, and both give only negligible response to ds-RNA. The fluorimetric response of 1 is proportional to the AT-basepair content in DNA, whereas the fluorescence of 2 is sensitive to the secondary structure of the polynucleotide. Fluorescence experiments, thermal melting experiments and circular dichroism studies suggest that 1 interacts with ds-DNA in a combined intercalation and minor groove binding, whereas 2 interacts mainly with the outer surface of DNA/RNA. As 1 and 2 have a very low cytotoxicity, 1 can be applied for the imaging of nuclear DNA in cells.

A metal-free fluorescence turn-on molecular probe for detection of nucleoside triphosphates

We report a fluorescence probe 1, which contains a naphthalimide fluorophore with two symmetric peptidic arms equipped with a tailor-made anion-binding motif, the guanidiniocarbonyl pyrrole moiety, for the detection of nucleoside triphosphates. Upon binding to nucleoside triphosphates, especially ATP, 1 shows significant turn-on fluorescence response. Probe 1 can also be applied for the imaging of ATP in cells.