Jong Min Lim

An electrochemical biosensor for detection of the sepsis-related biomarker procalcitonin

An electrochemical peptide sensor employing a sensitive synthetic peptide was designed for the diagnosis of sepsis. A series of synthetic peptides were chemically synthesized, and the binding events and performance of the sensor were monitored by CV and EIS. PCT BP3, selected as a potential high-affinity peptide, was found to have a Kd value of 0.39 ± 0.11 nM for procalcitonin.

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

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 Kd 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 ΔRct 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.

Selection of affinity peptides for interference-free detection of cholera toxin

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-AB5.

Cloning, Expression, and Production of Xylo-Oligosaccharides by Using a Newly Screened Xylanase Isolated from Bovine Rumen

Recently, there has been growing interest in the new types of functional prebiotics, including xylo-oligosaccharides (XOS) [1–3], fructo-oligosaccharides (FOS) [4, 5], maltooligosaccharides (MOS) [6, 7], isomalto-oligosaccharides (IMOS) [8, 9], inulooligosaccharides (IOS) [10–12], and other derivatives [13]. The fast-growing industry of functional foods and other food-related products allows investigation of bioactive materials and new technologies for improving the large-scale production of functional prebiotics. Of these prebiotics, XOS can be produced by the hydrolysis of xylan or xylan-containing agricultural sources as the substrate by enzymatic reaction with the endoand/or exoxylanases derived from various microorganisms, including Cellulomonas flavigena [14], Streptomyces rameus [2], Actinomadura species [15], Geobacillus thermoleovorans [1], Paecilomyces thermophila [3], Aspergillus usamii [16], and other microorganisms [17–19]. Appl Biochem Biotechnol https://doi.org/10.1007/s12010-017-2623-0

An electrochemical peptide sensor for detection of dengue fever biomarker NS1

Dengue virus type 2 NS1 (DENV2 NS1) is a specific and sensitive protein biomarker for dengue fever diagnosis. In this study we used polyvalent phage display to identify unique affinity peptides that can bind NS1 protein. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to investigate the binding interactions. The potential affinity peptide-displayed phage from these methods was selected; its sequence was EHDRMHAYYLTR (R3#10). Amino acid sequence analysis showed that the peptide was rich in basic residues (two His and Arg). Among all the peptides tested, R3#10 showed the greatest decrease in current in CV and increase in impedance in EIS upon binding to NS1 proteins. EIS revealed that R3#10 phage clones were more specific towards NS1 proteins, as compared to bovine serum albumin or the M13 wild type used as control. Detection of NS1 proteins is in accordance with the electron-transfer resistance (Rct) value of the sensor layer, which is confirmed by EIS, and the Kd value of the R3#10 peptide while binding to the phage particles was measured. To the best of our knowledge, this is the first example of identification and characterization of NS1 binding affinity peptides using phage display technology and electrochemical methods. We concluded that these new peptide-displayed phages or free peptides from phages may have potential applications in dengue diagnosis.