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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., Competing Interests: The authors have declared that no competing interests exist.

Cholera toxin is a major virulent agent of Vibrio cholerae, and it can rapidly lead to severe dehydration, shock, causing death within hours without appropriate clinical treatments. In this study, we present a method wherein unique and short peptides that bind to cholera toxin subunit B (CTX-B) were selected through M13 phage display. Biopanning over recombinant CTX-B led to rapid screening of a unique peptide with an amino acid sequence of VQCRLGPPWCAK, and the phage-displayed peptides analyzed using ELISA, were found to show specific affinities towards CTX-B. To address the use of affinity peptides in development of the biosensor, sequences of newly selected peptides were modified and chemically synthesized to create a series of affinity peptides. Performance of the biosensor was studied using plasmonic-based optical techniques: localized surface plasmon resonance (LSPR) and surface-enhanced Raman scattering (SERS). The limit of detection (LOD) obtained by LSPR with 3σ-rule was 1.89ng/mL, while SERS had a LOD of 3.51pg/mL. In both cases, the sensitivity was much higher than the previously reported values, and our sensor system was specific towards actual CTX-B secreted from V. cholera, but not for CTX-AB 5 ., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Colorectal cancer (CRC) is one of the leading causes of cancer-related deaths. Therefore, more sensitive and early diagnostic methods for CRC are urgently needed. In this study, an efficient electrochemical biosensor for early diagnosis of adenoma-to-carcinoma progression that employs a series of chemically modified affinity peptides was developed. A series of amino acid-substituted and cysteine-incorporated synthetic peptides with flexible linkers was chemically synthesized and immobilized to a gold sensor layer; performance of the sensor was monitored using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Potential affinity peptides (LRG1 BP1-BP4) specific for the LRG1 biomarker as a target protein were chosen according to a quantitative current decrease and dynamic impedance increase by CV and EIS, respectively. Using EIS, the K d value of the LRG1 BP3 peptide was found to be 8.3 ± 2.7nM. The applicability of the sensor to detect LRG1 proteins was confirmed in human plasma from colorectal adenomas and carcinomas (n = 20 in each group). The detection of LRG1 in accordance with the ΔR ct value (electron-transfer resistance at the electrode surface) of the sensor layer incorporating LRG1 BP3 peptides showed a statistically significant difference (p < 0.001) between adenomas and carcinomas, indicating that the potential use of this biosensing platform for detecting the CRC biomarker, as well as for monitoring the colorectal adenoma-to-carcinoma transition in an electrochemically miniaturized biosensor (e-chem biosensor) in point-of-care testing, is possible., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Norovirus is known as the major cause of highly infection for gastrointestinal tracts. In this study, robust and highly sensitive biosensors for detecting human norovirus by employing a recognition affinity peptide-based electrochemical platform were described. A series of amino acid-substituted and cysteine-incorporated recognition peptides isolated from evolutionary phage display technique was chemically synthesized and immobilized to a gold sensor layer, the detection performance of the gold-immobilized synthetic peptide-based sensor system was assessed using QCM, CV and EIS. Using EIS, the limit of detection with Noro-1 as a molecular binder was found to be 99.8nM for recombinant noroviral capsid proteins (rP2) and 7.8copies/mL for human norovirus, thereby demonstrating a high degree of sensitivity for their corresponding targets. These results suggest that a biosensor which consists of affinity peptides as a molecular binder and miniaturized microdevices as diagnostic tool could be served as a new type of biosensing platform for point-of-care testing., (Copyright © 2016 Elsevier B.V. All rights reserved.)