Facet-dependent interactions of islet amyloid polypeptide with gold nanoparticles: implications for fibril formation and peptide-induced lipid membrane disruption

A comprehensive understanding of the mechanisms of interaction between proteins or peptides and nanomaterials is crucial for the development of nanomaterial-based diagnos-tics and therapeutics. In this work, we systematically explored the interactions between citrate-capped gold nanoparticles (AuNPs) and islet amyloid polypeptide (IAPP), a 37-amino acid peptide hormone co-secreted with insulin from the pancreatic islet. We uti-lized diffusion-ordered spectroscopy, isothermal titration calorimetry, localized surface plasmon resonance spectroscopy, gel electrophoresis, atomic force microscopy, transmis-sion electron microscopy (TEM), and molecular dynamics (MD) simulations to systemati-cally elucidate the underlying mechanism of the IAPP−AuNP interactions. Because of the presence of a metal-binding sequence motif in the hydrophilic peptide domain, IAPP strongly interacts with the Au surface in both the monomeric and fibrillar states. Circular dichroism showed that AuNPs triggered the IAPP conformational transition from random coil to ordered structures (α-helix and β-sheet), and TEM imaging suggested the accelera-tion of IAPP fibrillation in the presence of AuNPs. MD simulations revealed that the IAPP−AuNP interactions were initiated by the N-terminal domain (IAPP residues 1−19), which subsequently induced a facet-dependent conformational change in IAPP. On a Au(111) surface, IAPP was unfolded and adsorbed directly onto the Au surface, while for the Au(100) surface, it interacted predominantly with the citrate adlayer and retained some helical conformation. The observed affinity of AuNPs for IAPP was further applied to reduce the level of peptide-induced lipid membrane disruption

Facet-dependent interactions of islet amyloid polypeptide with gold nanoparticles: Implications for fibril formation and peptide-induced lipid membrane disruption

A comprehensive understanding of the mechanisms of interaction between proteins or peptides and nanomaterials is crucial for the development of nanomaterial-based diagnostics and therapeutics. In this work, we systematically explored the interactions between citrate-capped gold nanoparticles (AuNPs) and islet amyloid polypeptide (IAPP), a 37-amino acid peptide hormone co-secreted with insulin from the pancreatic islet. We utilized diffusion-ordered spectroscopy, isothermal titration calorimetry, localized surface plasmon resonance spectroscopy, gel electrophoresis, atomic force microscopy, transmission electron microscopy (TEM), and molecular dynamics (MD) simulations to systematically elucidate the underlying mechanism of the IAPP–AuNP interactions. Because of the presence of a metal-binding sequence motif in the hydrophilic peptide domain, IAPP strongly interacts with the Au surface in both the monomeric and fibrillar states. Circular dichroism showed that AuNPs triggered the IAPP conformational transition from random coil to ordered structures (α-helix and β-sheet), and TEM imaging suggested the acceleration of IAPP fibrillation in the presence of AuNPs. MD simulations revealed that the IAPP–AuNP interactions were initiated by the N-terminal domain (IAPP residues 1–19), which subsequently induced a facet-dependent conformational change in IAPP. On a Au(111) surface, IAPP was unfolded and adsorbed directly onto the Au surface, while for the Au(100) surface, it interacted predominantly with the citrate adlayer and retained some helical conformation. The observed affinity of AuNPs for IAPP was further applied to reduce the level of peptide-induced lipid membrane disruption

Определение природных и техногенных радионуклидов в бальнеологических объектах

Quantitative detection of angiogenic biomarkers provides a powerful tool to diagnose cancers in early stages and to follow its progression during therapy. Conventional tests require trained personnel, dedicated laboratory equipment and are generally time-consuming. Herein, we propose our developed biosensing platform as a useful tool for a rapid determination of Angiopoietin-2 biomarker directly from patient plasma within 30 minutes, without any sample preparation or dilution. Bloch surface waves supported by one dimensional photonic crystal are exploited to enhance and redirect the fluorescence arising from a sandwich immunoassay that involves Angiopoietin-2. The sensing units consist of disposable and low-cost plastic biochips coated with the photonic crystal. The biosensing platform is demonstrated to detect Angiopoietin-2 in plasma samples at the clinically relevant concentration of 6 ng/mL, with an estimated limit of detection of approximately 1 ng/mL. This is the first Bloch surface wave based assay capable of detecting relevant concentrations of an angiogenic factor in plasma samples. The results obtained by the developed biosensing platform are in close agreement with enzyme-linked immunosorbent assays, demonstrating a good accuracy, and their repeatability showed acceptable relative variations

Effective biosensor arrays using gold nanaoparticle-protein conjugates

Developing effective biosensor for proteins, cells, and tissues would enhance the likelihood of early disease detection and treatment. Traditional specificity-based methods are limited by the requirement of prior knowledge of the specific biomarker(s) and high production cost. My research has been focused on developing a rapid and efficient biosensor based on selective interactions using an unbiased array of supramolecular complexes formed between cationic gold nanoparticles and fluorescent proteins. The sensor is capable of discriminating between mammalian cells, as well as healthy and metastatic tissues with significantly small amount of samples, an important requirement for disease diagnosis in clinics. In addition to the cell/tissue state classification, the sensor array is able to identify protein imbalances in undiluted serum, demonstrating the applicability of the sensor array in physiological matrices. Later, I have developed a triple-channel high-throughput sensor to identify chemotherapeutic drug mechanism that would simplify drug discovery. Overall, the sensor array provides a generic tool for bio-profiling, precluding additional processing steps prior to screening and holds great promise for personalized screening of disease states

Silver-Based Supramolecular Hydrogel for the Development of Smartphone-Enabled Alkaline Phosphatase Sensor

Alkaline phosphatase (ALP) is an important protein responsible for various conditions related to hepatobiliary, osteopenia, pregnancy, and certain cancers. Developing an easy-to-use paper-based sensor for ALP would provide a point-of-care diagnostic device. A silver-coordinated cytidine hydrogel is a potential candidate to show responses under different concentrations of ALP. Herein, we prepared and characterized a three-component hydrogel system comprising cytidine, boric acid, and silver nitrate. The gelation occurs rapidly within a minute at room temperature and atmospheric pressure, which makes the system more convenient to use. Reduction of Ag+ by the in situ generated ascorbic acid by ALP allows the development of colorimetric sensor based on the gel-coated paper, enabling quantification of ALP concentration. This portable sensor works efficiently on a smartphone color-scanning app, making point-of-care detection easier. RGB values obtained from scanning indicate the ALP concentration in the range of 1-100 nM, which is independent of mobile cameras. The hydrogel exhibits excellent solvo-reversibility and enables naked-eye colorimetric detection of ALP with a detection limit of 0.23 nM (0.016 U/L). The sensing strategy works well in spiked human serum with a detection limit of 0.34 nM (0.023 U/L) in solution and paper-based sensors. Overall, the cytidine-based gel system presents an effective point-of-care diagnostic system for detecting ALP with high sensitivity

A Dissipative Supramolecular Glue for Temporal Control of Amplified Enzyme Activity and Biocatalytic Cascades

Regulation of enzyme activity is key to the adaptation of cellular processes such as signal transduction and metabolism in response to varying external conditions. Synthetic molecular glues have provided effective systems for enzyme inhibition and regulation of protein-protein interactions. So far, all the molecular glue systems based on covalent interactions operated in equilibrium conditions. To emulate dynamic far-from-equilibrium biological processes, we introduce herein a transient supramolecular glue with controllable lifetime. The transient system uses multivalent supramolecular interactions between guanidium group-bearing surfactants and adenosine triphosphates (ATP), resulting in bilayer vesicle structures. Unlike the conventional fuels for non-equilibrium assemblies, ATP here plays the dual role of providing a structural component for the assembly as well as presenting active functional groups to “glue” enzymes on the surface. While gluing of the enzymes on the vesicles achieves augmented catalysis, oscillation of ATP concentration allows temporal control of the catalytic activities. We further demonstrate temporal activation and control of biocatalytic cascade networks on the vesicles, which represents an essential cellular component. Altogether, the temporal activation of biocatalytic cascades on the dissipative vesicular glue presents an adaptable and dynamic system emulating heterogeneous cellular processes, opening up avenues for effective protocell construction and therapeutic interventions

G-quadruplex Hydrogel-based Stimuli-responsive High-internal-phase Emulsion Scaffold for Biocatalytic Cascades and Synergistic Antimicrobial Activity

High internal phase emulsions (HIPEs) are non-equilibrium systems with distorted liquid droplet shapes consisting of high volume of internal phase (>74% v/v), enabling high loading of pharmaceutics and useful viscoelastic properties. Stability of the HIPEs is low and requires a high volume of surfactants in the continuous phase, which is environmentally unfriendly. Utilization of hydrogel as the continuous phase to stabilize HIPEs would offer a robust method to produce stable HIPE gels displaying reconfigurable and biocompatible properties, as well as access the huge repertoire of different biocompatible hydrogels. Herein, we introduce a new gel-immobilized HIPE (HIPEG) using chiral G-quadruplex (GQ) based hydrogel with external stimuli-responsive dual-drug release behavior, which is scarce for HIPEs. The hydrophilic and hydrophobic compartments of HIPEGs allow encapsulation of different drugs in both the compartments, with stimuli-responsive diffusion mediated release. Encapsulation of natural oils and antibiotics produces synergistic antimicrobial effects on both Gram positive (MRSA) and Gram negative (P. aeruginosa) bacterial strains. Moreover, we demonstrate biocatalytic reaction networks utilizing compartmentalized enzyme dyads. Notably, the ideal viscoelastic property of HIPEGs enables 3D bioprinting into different shapes, making the scaffold potential for tissue engineering applications. Altogether, our approach offers a one-step route to stimuli-responsive HIPE microcompartments immobilized in GQ hydrogels with endogenous reactivity and high viscoelasticity, and provides a viable step towards the development of biocompatible soft materials with tailorable functionality

Nanoparticles for detection and diagnosis

Nanoparticle-based platforms for identification of chemical and biological agents offer substantial benefits to biomedical and environmental science. These platforms benefit from the availability of a wide variety of core materials as well as the unique physical and chemical properties of these nanoscale materials. This review surveys some of the emerging approaches in the field of nanoparticle based detection systems, highlighting the nanoparticle based screening methods for metal ions, proteins, nucleic acids, and biologically relevant small molecules

Sequestration of histidine kinases by non-cognate response regulators establishes a threshold level of stimulation for bacterial two-component signaling

Abstract Bacterial two-component systems (TCSs) consist of a sensor histidine kinase (HK) that perceives a specific signal, and a cognate response regulator (RR) that modulates the expression of target genes. Positive autoregulation improves TCS sensitivity to stimuli, but may trigger disproportionately large responses to weak signals, compromising bacterial fitness. Here, we combine experiments and mathematical modelling to reveal a general design that prevents such disproportionate responses: phosphorylated HKs (HK~Ps) can be sequestered by non-cognate RRs. We study five TCSs of Mycobacterium tuberculosis and find, for all of them, non-cognate RRs that show higher affinity than cognate RRs for HK~Ps. Indeed, in vitro assays show that HK~Ps preferentially bind higher affinity non-cognate RRs and get sequestered. Mathematical modelling indicates that this sequestration would introduce a ‘threshold’ stimulus strength for eliciting responses, thereby preventing responses to weak signals. Finally, we construct tunable expression systems in Mycobacterium bovis BCG to show that higher affinity non-cognate RRs suppress responses in vivo