CRP-binding bacteriophage as a new element of layer-by-layer assembly carbon nanofiber modified electrodes

Investigation of Peptides for Molecular Recognition of C-Reactive Protein-Theoretical and Experimental Studies

We investigate the interactions between C-reactive protein (CRP) and new CRP-binding peptide materials using experimental (biological and physicochemical) methods with the support of theoretical simulations (computational modeling analysis). Three specific CRP-binding peptides (P2, P3, and P9) derived from an M13 bacteriophage have been identified using phage-display technology. The binding efficiency of the peptides exposed on phages toward the CRP protein was demonstrated via biological methods. Fibers of the selected phages/peptides interact differently due to different compositions of amino acid sequences on the exposed peptides, which was confirmed by transmission electron microscopy. Numerical and experimental studies consistently showed that the P3 peptide is the best CRP binder. A combination of theoretical and experimental methods demonstrates that identifying the best binder can be performed simply, cheaply, and fast. Such an approach has not been reported previously for peptide screening and demonstrates a new trend in science where calculations can replace or support laborious experimental techniques. Finally, the best CRP binder─the P3 peptide─was used for CRP recognition on silicate-modified indium tin oxide-coated glass electrodes. The obtained electrodes exhibit a wide range of operation (1.0-100 μg mL-1) with a detection limit (LOD = 3σ/S) of 0.34 μg mL-1. Moreover, the dissociation constant Kd of 4.2 ± 0.144 μg mL-1 (35 ± 1.2 nM) was evaluated from the change in the current. The selectivity of the obtained electrode was demonstrated in the presence of three interfering proteins. These results prove that the presented P3 peptide is a potential candidate as a receptor for CRP, which can replace specific antibodies.

Determination of the Dissociation Constant for Polyvalent Receptors Using ELISA: A Case of M13 Phages Displaying Troponin T-Specific Peptides

Phage-derived affinity peptides have become widespread thanks to their easy selection via phage display. Interactions between a target protein and its specific peptide are similar to those between antibodies and antigens. The strength of these non-covalent complexes may be described by the dissociation constant (K_d). In this paper, protein-specific peptides are exposed on the pIII protein present in the M13 bacteriophage virion with up to five copies. Therefore, one phage particle can bind from one to five ligands. Here, we discuss the dependences between phage-displayed peptides and their ligands in solution using a model system based on troponin T (TnT) binding phages. Moreover, a method of calculating K_d values from ELISA experiments was developed and is presented. The determined K_d values are in the picomolar range.

Modification of polyacrylonitrile-derived carbon nanofibers and bacteriophages on screen-printed electrodes: A portable electrochemical biosensor for rapid detection of Escherichia coli

A facile method was developed for fabricating a disposable phage-based electrochemical biosensor for the detection of Escherichia coli. Bare screen-printed electrodes (SPEs) were modified using a two-step drop-casting method, in which polyacrylonitrile-derived electrospun carbon nanofibers (CNFs) were deposited, followed by E. coli bacteriophage immobilization. The deposition of CNFs increased the surface area for bacteriophage immobilization while maintaining a conductive link for ferro/ferricyanide redox transitions. Cyclic voltammetry and electrochemical impedance spectroscopy confirmed that the CNF modification increased the electron-transfer rate, whereas bacteriophages and E. coli blocked electron transfer at the electrode. The biosensor achieved a response within 10 min and a linear response in the E. coli concentration range of 10²-10⁶ CFU/mL. A limit of detection (LOD) of 36 CFU/mL in phosphate-buffered saline was achieved, which is the lowest LOD reported thus far for phage-based disposable SPE sensors. The biosensor exhibited recovery rates between 106 % and 119 % for E. coli detection in apple juice. The proposed fabrication method allowed electrodes to be obtained from different production batches with remarkable consistency and reproducibility, and they remained stable at room temperature for one month. Thus, a phage-based disposable SPE that can be used for bacterial detection was developed for the first time.

Electroanalytical point-of-care detection of gold standard and emerging cardiac biomarkers for stratification and monitoring in intensive care medicine - a review

Determination of specific cardiac biomarkers (CBs) during the diagnosis and management of adverse cardiovascular events such as acute myocardial infarction (AMI) has become commonplace in emergency department (ED), cardiology and many other ward settings. Cardiac troponins (cTnT and cTnI) and natriuretic peptides (BNP and NT-pro-BNP) are the preferred biomarkers in clinical practice for the diagnostic workup of AMI, acute coronary syndrome (ACS) and other types of myocardial ischaemia and heart failure (HF), while the roles and possible clinical applications of several other potential biomarkers continue to be evaluated and are the subject of several comprehensive reviews. The requirement for rapid, repeated testing of a small number of CBs in ED and cardiology patients has led to the development of point-of-care (PoC) technology to circumvent the need for remote and lengthy testing procedures in the hospital pathology laboratories. Electroanalytical sensing platforms have the potential to meet these requirements. This review aims firstly to reflect on the potential benefits of rapid CB testing in critically ill patients, a very distinct cohort of patients with deranged baseline levels of CBs. We summarise their source and clinical relevance and are the first to report the required analytical ranges for such technology to be of value in this patient cohort. Secondly, we review the current electrochemical approaches, including its sub-variants such as photoelectrochemical and electrochemiluminescence, for the determination  of important CBs highlighting the various strategies used, namely the use of micro- and nanomaterials, to maximise the sensitivities and selectivities of such approaches. Finally, we consider the challenges that must be overcome to allow for the commercialisation of this technology and transition into intensive care medicine.

Native llama Nanobody Library Panning Performed by Phage and Yeast Display Provides Binders Suitable for C-Reactive Protein Detection

C-reactive protein (CRP) is an inflammation biomarker that should be quantified accurately during infections and healing processes. Nanobodies are good candidates to replace conventional antibodies in immunodiagnostics due to their inexpensive production, simple engineering, and the possibility to obtain higher binder density on capture surfaces. Starting from the same pre-immune library, we compared the selection output resulting from two independent panning strategies, one exclusively exploiting the phage display and another in which a first round of phage display was followed by a second round of yeast display. There was a partial output convergence between the two methods, since two clones were identified using both panning protocols but the first provided several further different sequences, whereas the second favored the recovery of many copies of few clones. The isolated anti-CRP nanobodies had affinity in the low nanomolar range and were suitable for ELISA and immunoprecipitation. One of them was fused to SpyTag and exploited in combination with SpyCatcher as the immunocapture element to quantify CRP using electrochemical impedance spectroscopy. The sensitivity of the biosensor was calculated as low as 0.21 μg/mL.

Taking Advantage of the Morpheein Behavior of Peroxiredoxin in Bionanotechnology

Morpheeins are proteins that reversibly assemble into different oligomers, whose architectures are governed by conformational changes of the subunits. This property could be utilized in bionanotechnology where the building of nanometric and new high-ordered structures is required. By capitalizing on the adaptability of morpheeins to create patterned structures and exploiting their inborn affinity toward inorganic and living matter, “bottom-up” creation of nanostructures could be achieved using a single protein building block, which may be useful as such or as scaffolds for more complex materials. Peroxiredoxins represent the paradigm of a morpheein that can be applied to bionanotechnology. This review describes the structural and functional transitions that peroxiredoxins undergo to form high-order oligomers, e.g., rings, tubes, particles, and catenanes, and reports on the chemical and genetic engineering approaches to employ them in the generation of responsive nanostructures and nanodevices. The usefulness of the morpheeins’ behavior is emphasized, supporting their use in future applications.