Electrochemical peptide sensor for diagnosing adenoma-carcinoma transition in colon cancer

Hybrid MoSe2/P3HT Transistor for Real-Time Ammonia Sensing in Biofluids

Organic and inorganic hybrid field-effect transistors (FETs), utilizing layered molybdenum diselenide (MoSe2) and an organic semiconductor poly(3-hexylthiophene) (P3HT), are presented for biosensing applications. A new hybrid device structure that combines organic (P3HT) and inorganic (MoSe2) components is showcased for accurate and selective bioanalyte detection in human bodily fluids to overcome 2D-transition metal dichalcogenides (TMDs) nonspecific interactions. This hybrid structure utilizes organic and inorganic semiconductors' high surface-to-volume ratio, carrier transport, and conductivity for biosensing. Ammonia concentrations in saliva and plasma are closely linked to physiological and pathological conditions of the human body. A highly sensitive hybrid FET biosensor detects total ammonia (NH4+ and NH3) from 0.5 μM to 1 mM concentrations, with a detection limit of 0.65 μM in human bodily fluids. The sensor's ammonia specificity in artificial saliva against interfering species is showcased. Furthermore, the fabricated hybrid FET device exhibits a stable and repeatable response to ammonia in both saliva and plasma, achieving a remarkable response level of 2300 at a 1 mM concentration of ammonia, surpassing existing literature by 10-fold. This hybrid FET biosensing platform holds significant promise for developing a precise tool for the real-time monitoring of ammonia concentrations in human biological fluids, offering potential applications in point-of-care diagnostics.

Electrochemical peptide-based biosensor for the detection of the inflammatory disease biomarker, interleukin-1beta

This paper reports the development of a highly sensitive and selective electrochemical peptide-based biosensor for the detection of the inflammatory disease biomarker, interleukin-1beta (IL-1β). To this end, flower-like Au-Ag@MoS2-rGO nanocomposites were used as the signal amplification platform to achieve a label-free biosensor with a high sensitivity and selectivity. First, a high-affinity peptide for IL-1β was identified through biopanning with M13 random peptide libraries, and was newly designed by incorporating cysteine at the C-terminus. An IL-1β specific binding peptide was used as the bio-receptor, and the interaction between the IL-1β binding peptide and IL-1β was confirmed via enzyme-linked immunosorbent assay and various physicochemical and electrochemical analyses. Under optimal conditions, the biosensor achieved an ultrasensitive and specific IL-1β detection in a wide linear concentration range of 0-250 ng/mL with a picomolar-level detection limit (∼2.4 pM), low binding constant (∼0.62 pM), and a low coefficient of variation (<1.65 %). The biosensor was successfully utilized for IL-1β determination in the serum of Crohn's disease patients with a good correlation coefficient. In addition, the detection performance was comparable to that of commercially available IL-1β ELISA kit. This indicates that the electrochemical peptide-based biosensor may offer a potentially valuable platform for the clinical diagnosis of various inflammatory disease biomarkers.

The Progress of Research into Flexible Sensors in the Field of Smart Wearables

In modern society, technology associated with smart sensors made from flexible materials is rapidly evolving. As a core component in the field of wearable smart devices (or 'smart wearables'), flexible sensors have the advantages of excellent flexibility, ductility, free folding properties, and more. When choosing materials for the development of sensors, reduced weight, elasticity, and wearer's convenience are considered as advantages, and are suitable for electronic skin, monitoring of health-related issues, biomedicine, human-computer interactions, and other fields of biotechnology. The idea behind wearable sensory devices is to enable their easy integration into everyday life. This review discusses the concepts of sensory mechanism, detected object, and contact form of flexible sensors, and expounds the preparation materials and their applicability. This is with the purpose of providing a reference for the further development of flexible sensors suitable for wearable devices.

Lab-on-a-chip technologies for minimally invasive molecular sensing of diabetic retinopathy

Diabetic retinopathy (DR) is the most common diabetic eye disease and the worldwide leading cause of vision loss in working-age adults. It progresses from mild to severe non-proliferative or proliferative DR based on several pathological features including the magnitude of blood-retinal barrier breakdown and neovascularization. Available pharmacological and retinal laser photocoagulation interventions are mostly applied in the advanced stages of DR and are inefficient in halting disease progression in a significantly high percentage of patients. Yet, recent evidence has shown that some therapies could potentially limit DR progression if applied at early stages, highlighting the importance of early disease diagnostics. In the past few decades, different imaging modalities have proved their utility for examining retinal and optic nerve changes in patients with retinal diseases. However, imaging based-methodologies solely rely on morphological examination of the retinal vascularization and are not suitable for recurrent and personalized patient evaluation. This raises the need for new technologies to enable accurate and early diagnosis of DR. In this review, we critically discuss the potential clinical benefit of minimally-invasive molecular biomarker identification and profiling of diabetic patients who are at risk of developing DR. We provide a comparative overview of conventional and recently developed lab-on-a-chip technologies for quantitative assessment of potential DR molecular biomarkers and discuss their advantages, current limitations and challenges for future practical implementation and continuous patient monitoring at the point-of-care.

LRG1: an emerging player in disease pathogenesis

The secreted glycoprotein leucine-rich α-2 glycoprotein 1 (LRG1) was first described as a key player in pathogenic ocular neovascularization almost a decade ago. Since then, an increasing number of publications have reported the involvement of LRG1 in multiple human conditions including cancer, diabetes, cardiovascular disease, neurological disease, and inflammatory disorders. The purpose of this review is to provide, for the first time, a comprehensive overview of the LRG1 literature considering its role in health and disease. Although LRG1 is constitutively expressed by hepatocytes and neutrophils, Lrg1-/- mice show no overt phenotypic abnormality suggesting that LRG1 is essentially redundant in development and homeostasis. However, emerging data are challenging this view by suggesting a novel role for LRG1 in innate immunity and preservation of tissue integrity. While our understanding of beneficial LRG1 functions in physiology remains limited, a consistent body of evidence shows that, in response to various inflammatory stimuli, LRG1 expression is induced and directly contributes to disease pathogenesis. Its potential role as a biomarker for the diagnosis, prognosis and monitoring of multiple conditions is widely discussed while dissecting the mechanisms underlying LRG1 pathogenic functions. Emphasis is given to the role that LRG1 plays as a vasculopathic factor where it disrupts the cellular interactions normally required for the formation and maintenance of mature vessels, thereby indirectly contributing to the establishment of a highly hypoxic and immunosuppressive microenvironment. In addition, LRG1 has also been reported to affect other cell types (including epithelial, immune, mesenchymal and cancer cells) mostly by modulating the TGFβ signalling pathway in a context-dependent manner. Crucially, animal studies have shown that LRG1 inhibition, through gene deletion or a function-blocking antibody, is sufficient to attenuate disease progression. In view of this, and taking into consideration its role as an upstream modifier of TGFβ signalling, LRG1 is suggested as a potentially important therapeutic target. While further investigations are needed to fill gaps in our current understanding of LRG1 function, the studies reviewed here confirm LRG1 as a pleiotropic and pathogenic signalling molecule providing a strong rationale for its use in the clinic as a biomarker and therapeutic target.

The Role of Peptides in the Design of Electrochemical Biosensors for Clinical Diagnostics

Peptides represent a promising class of biorecognition elements that can be coupled to electrochemical transducers. The benefits lie mainly in their stability and selectivity toward a target analyte. Furthermore, they can be synthesized rather easily and modified with specific functional groups, thus making them suitable for the development of novel architectures for biosensing platforms, as well as alternative labelling tools. Peptides have also been proposed as antibiofouling agents. Indeed, biofouling caused by the accumulation of biomolecules on electrode surfaces is one of the major issues and challenges to be addressed in the practical application of electrochemical biosensors. In this review, we summarise trends from the last three years in the design and development of electrochemical biosensors using synthetic peptides. The different roles of peptides in the design of electrochemical biosensors are described. The main procedures of selection and synthesis are discussed. Selected applications in clinical diagnostics are also described.

Nanostructured functional peptide films and their application in C-reactive protein immunosensors

Peptides with an active redox molecule are incorporated into nanostructured films for electrochemical biosensors with stable and controllable physicochemical properties. In this study, we synthesized three ferrocene (Fc)-containing peptides with the sequence Fc-Glu-(Ala)_n-Cys-NH₂, which could form self-assembled monolayers on gold and be attached to antibodies. The peptide with two alanines (n = 2) yielded the immunosensor with the highest performance in detecting C-reactive protein (CRP), a biomarker of inflammation. Using electrochemical impedance-derived capacitive spectroscopy, the limit of detection was 240 pM with a dynamic range that included clinically relevant CRP concentrations. With a combination of electrochemical methods and polarization-modulated infrared reflection-absorption spectroscopy, we identified the chemical groups involved in the antibody-CRP interaction, and were able to relate the highest performance for the peptide with n = 2 to chain length and efficient packing in the organized films. These strategies to design peptides and methods to fabricate the immunosensors are generic, and can be applied to other types of biosensors, including in low cost platforms for point-of-care diagnostics.

Re-engineering of peptides with high binding affinity to develop an advanced electrochemical sensor for colon cancer diagnosis

Colorectal cancer (CRC) develops from polyps in the inner large intestine or rectum and an increasing incidence and high mortality rate has been observed in humans. Currently, colonoscopy is the preferred modality for early CRC diagnosis. However, this technique has several limitations, such as high medical costs and intricate procedures, leading to increasing demands for the development of a new, simple, and affordable diagnostic method. In this study, an advanced electrochemical biosensor based on rationally designed affinity peptides was developed for discriminating adenoma to carcinoma progression. Amino acid-substituted and rationally designed synthetic peptides (BP3-1 to BP3-8) based on in silico modeling studies were chemically synthesized, and covalently immobilized onto a gold electrode using aromatic ring compounds through surface chemistry techniques. The binding performance of the developed sensor system was observed using square wave voltammetry (SWV). The peptide BP3-2 was selected depending on its relative binding affinity; SWV indicated the limit of detection of BP3-2 for LRG1 to be 0.025 μg/mL. This sensor could distinguish the adenoma-carcinoma transition with improved binding abilities (specificity and selectivity), and stability in plasma samples spiked with LRG1 and real samples from patients with CRC. These results indicate that this electrochemical sensor system can be used for early monitoring of the colorectal adenoma to carcinoma progression.

A screening study of high affinity peptide as molecular binder for AXL, tyrosine kinase receptor involving in Zika virus entry

The recent extensive spread of Zika virus has led to increased interest in the development of early diagnostic tests. To the best of our knowledge, this is the first study to demonstrate the successful use of phage display to identify affinity peptides for quantitative analysis of AXL, a tyrosine kinase receptor involved in Zika virus entry. Biopanning of M13 phage library successfully identified a high affinity peptide, with the sequence AHNHTPIKQKYL. To study the feasibility of using free peptides for molecular recognition, we synthesized a series of amino acid-substituted peptides and examined their binding affinity for AXL using electrochemical impedance spectroscopy and square wave voltammetry. Most synthetic peptides had non-identical random coil structures based on circular dichroism spectroscopy. Of the peptides tested, AXL BP1 exhibited nanomolar binding affinity for AXL. To verify whether AXL BP1 could be used as a peptide inhibitor at the cellular level, two functional tests were carried out: a WST assay for cell viability and qRT-PCR for quantification of RNA levels in Zika virus-infected Huh7 cells. The results showed that AXL BP1 had low cytotoxicity and could block Zika virus entry. These results indicate that newly identified affinity peptides could potentially be used for the development of Zika virus entry inhibitors.

Electrochemical Biosensors for Determination of Colorectal Tumor Biomarkers

The accurate determination of specific tumor markers associated with cancer with non-invasive or minimally invasive procedures is the most promising approach to improve the long-term survival of cancer patients and fight against the high incidence and mortality of this disease. Quantification of biomarkers at different stages of the disease can lead to an appropriate and instantaneous therapeutic action. In this context, the determination of biomarkers by electrochemical biosensors is at the forefront of cancer diagnosis research because of their unique features such as their versatility, fast response, accurate quantification, and amenability for multiplexing and miniaturization. In this review, after briefly discussing the relevant aspects and current challenges in the determination of colorectal tumor markers, it will critically summarize the development of electrochemical biosensors to date to this aim, highlighting the enormous potential of these devices to be incorporated into the clinical practice. Finally, it will focus on the remaining challenges and opportunities to bring electrochemical biosensors to the point-of-care testing.

A surface plasmon resonance biosensor in conjunction with a DNA aptamer-antibody bioreceptor pair for heterogeneous nuclear ribonucleoprotein A1 concentrations in colorectal cancer plasma solutions

A new DNA aptamer and antibody pair was incorporated into surface plasmon resonance (SPR) sensing platform to detect heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) in plasma at clinically relevant native concentrations for the diagnosis of colorectal cancer (CRC). SPR detection of hnRNP A1 was realized via formation of the surface sandwich complex of aptamer/hnRNP A1/anti-hnRNP A; the specific adsorption of hnRNP A1 onto a gold chip surface modified with a DNA aptamer followed by the adsorption of anti-hnRNP A1. Changes in the refractive unit (RU) with respect to the hnRNP A1 concentration in buffer solutions were monitored at a fixed anti-hnRNP A1 concentration of 90 nM, resulting in a dynamic range of 0.1-10 nM of hnRNP A1. The surface sandwich SPR biosensor was further applied to the direct analysis of undiluted human normal and pooled CRC patient plasma solutions. Our plasma analysis results were compared to those obtained with a commercial enzyme-linked immunosorbent assay kit.

Peptide-conjugated hemin/G-quadruplex as a versatile probe for "signal-on" electrochemical peptide biosensor

In this work, a novel "signal-on" electrochemical peptide biosensor based on peptide-conjugated hemin/G-quadruplex (DNAzyme-peptide) hybrid and rosebud-like MoSe₂@reduced graphene oxide (MoSe₂@rGO) nanocomposite, was developed for detection of prostate-specific antigen (PSA). Interestingly, the peptide not only served as recognition probe to detect PSA, but also acted as the enhancer to improve the enzyme activity of hemin/G4, which promoted the detection sensitivity. Up addition of PSA, Fe₃O₄-labeled DNAzyme-peptide probe was cleaved, followed by the magnetic separation. The cleaved DNAzyme-peptide was then captured onto the cysteine-modified electrode via the interaction between carboxyl groups of peptide and amino group of cysteine. A strong electrochemical signal was obtained from hemin and further was amplified by the enhanced electrocatalysis of DNAzyme-peptide. Compared to the original DNAzyme, DNAzyme-peptide exhibited more than 3-fold enhancement in signal amplification. And MoSe₂@rGO amplified the electrochemical signal due to its good conductivity and large surface area. So the proposed strategy detected PSA down to 0.3 fg/mL, and it showed the advantages of simplicity, low cost by avoiding the use of expensive protein enzyme and additional electroactive species. Therefore, the proposed biosensor potentially provided a very effective tool for early diagnosis of cancer by the detection of PSA.

Development of peptide biosensor for the detection of dengue fever biomarker, nonstructural 1

Dengue virus (DENV) nonstructural 1 (NS1) protein is a specific and sensitive biomarker for the diagnosis of dengue. In this study, an efficient electrochemical biosensor that uses chemically modified affinity peptides was developed for the detection of dengue virus NS1. A series of amino acid-substituted synthetic peptides was rationally designed, chemically synthesized and covalently immobilized to a gold sensor surface. The sensor performance was monitored via square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS). Potential affinity peptides specific for NS1 were chosen according to the dynamic current decrease in SWV experiments. Using circular dichroism, the molar ellipticity of peptides (DGV BP1–BP5) was determined, indicating that they had a mostly similar in random coil structure, not totally identical. Using SWV, DGV BP1 was selected as a promising recognition peptide and limit of detection for NS1 was found to be 1.49 μg/mL by the 3-sigma rule. DGV BP1 showed good specificity and stability for NS1, with low signal interference. The validation of the sensor to detect NS1 proteins was confirmed with four dengue virus culture broth (from serotype 1 to 4) as proof-of-concept. The detection performance of our sensor incorporating DGV BP1 peptides showed a statistically significant difference. These results indicate that this strategy can potentially be used to detect the dengue virus antigen, NS1, and to diagnosis dengue fever within a miniaturized portable device in point-of-care testing.

Use of anti-CRISPR protein AcrIIA4 as a capture ligand for CRISPR/Cas9 detection

The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) ribonucleoprotein (RNP) complex is an RNA-guided DNA-nuclease that is part of the bacterial adaptive immune system. CRISPR/Cas9 RNP has been adapted for targeted genome editing within cells and whole organisms with new applications vastly outpacing detection and quantification of gene-editing reagents. Detection of the CRISPR/Cas9 RNP within biological samples is critical for assessing gene-editing reagent delivery efficiency, retention, persistence, and distribution within living organisms. Conventional detection methods are effective, yet the expense and lack of scalability for antibody-based affinity reagents limit these techniques for clinical and/or field settings. This necessitates the development of low cost, scalable CRISPR/Cas9 RNP affinity reagents as alternatives or augments to antibodies. Herein, we report the development of the Streptococcus pyogenes anti-CRISPR/Cas9 protein, AcrIIA4, as a novel affinity reagent. An engineered cysteine linker enables covalent immobilization of AcrIIA4 onto glassy carbon electrodes functionalized via aryl diazonium chemistry for detection of CRISPR/Cas9 RNP by electrochemical, fluorescent, and colorimetric methods. Electrochemical measurements achieve a detection of 280 pM RNP in reaction buffer and 8 nM RNP in biologically representative conditions. Our results demonstrate the ability of anti-CRISPR proteins to serve as robust, specific, flexible, and economical recognition elements in biosensing/quantification devices for CRISPR/Cas9 RNP.

Designing phenylalanine-based hybrid biological materials: controlling morphology via molecular composition

Harnessing the self-assembly of peptide sequences has demonstrated great promise in the domain of creating high precision shape-tunable biomaterials. The unique properties of peptides allow for a building block approach to material design. In this study, self-assembly of mixed systems encompassing two peptide sequences with identical hydrophobic regions and distinct polar segments is investigated. The two peptide sequences are diphenylalanine and phenylalanine-asparagine-phenylalanine. The study examines the impact of molecular composition (namely, the total peptide concentration and the relative tripeptide concentration) on the morphology of the self-assembled hybrid biological material. We report a rich polymorphism in the assemblies of these peptides and explain the relationship between the peptide sequence, concentration and the morphology of the supramolecular assembly.