Jong Pil Park

Effect of aeration rate on the mycelial morphology and exo-biopolymer production in Cordyceps militaris

The influence of aeration rate on Cordyceps militaris morphology and exo-biopolymer production was investigated in a 5-l jar fermentor. The mycelial morphology of C. militaris was characterized by image analysis, which included mean diameter, circularity, roughness, and compactness of the pellets. Cells were observed to form mainly pellets during the entire culture period irrespective of aeration conditions. There existed a notable variation in morphological parameters between the pellets grown on different aeration conditions, by which exo-biopolymer production yields were correspondingly altered. The mean diameter and compactness of the pellets indicated higher values at 2 vvm (volume of air per volume of culture per minute), which was closely related to exo-biopolymer biosynthesis. The more compact pelleted form was favourable for exo-biopolymer production. Under extremely low and high aeration conditions (e.g. 0.5 and 4 vvm), severe deformations of pellets (autolysis of core and shaving off the outer hairy region) were observed at the later stages of fermentation associated with a decrease in morphological parameters.

High sensitive and selective electrochemical biosensor: Label-free detection of human norovirus using affinity peptide as molecular binder.

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.

Identification of high affinity peptides for capturing norovirus capsid proteins

Here, we present a platform where novel short and linear peptide motifs that enable binding to norovirus capsid proteins are selected by M13 phage display. The best peptide which recognizes recombinant norovirus 6H-P2 proteins has a sequence of ‘QHIMHLPHINTL’ and the apparent dissociation binding constants (Kd,app) of the selected peptides was found to be 185 nM of affinity.

Evolutionary identification of affinity peptides for the detection of sepsis biomarker procalcitonin

We demonstrate for the first time the use of phage display for identification and selection of novel peptides that are capable of binding to procalcitonin. The best peptide specific for procalcitonin has an amino acid sequence of ‘MSCAGHMCTRFV’ and the binding affinity was observed with a nanomolar binding.

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.

Synergistic molecular assembly of an aptamer and surfactant on gold nanoparticles for the colorimetric detection of trace levels of As3+ ions in real samples

The use of the synergistic molecular assembly of an aptamer and cetyltrimethylammonium bromide (CTAB) on gold nanoparticles (AuNPs) is described for the selective and sensitive colorimetric recognition of As3+ ions in water samples. The As3+ ions coordinate with Ars-3 aptamer–AuNPs, causing aggregation in the presence of CTAB, which induces a red-shift in the surface plasmon resonance (SPR) band and a visual change in the color. The aptamer has shown a strong tendency to bind with As3+ ions using CTAB as a binder, exhibiting good linearity between the absorption ratio (A650/A520) and the concentration of As3+ ions (1.0–100 ppb) with a detection limit of 16.9 ppb. In contrast, other chemical species (metal ions and anions) did not induce these changes at all, and thus the aptasensor is highly specific for As3+ ion sensing. The spectroscopic and TEM results show high selectivity for As3+ ion sensing and the assay is completed within 30 min. The aptamer–AuNP-based colorimetric method illustrates the potential utility for screening As3+ ion levels in real samples. The developed aptasensor was successfully applied for the detection of As3+ ions in water and cosmetic samples, signifying its remarkable application for As3+ ion sensing in real samples.

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.

Development of a rapid and sensitive electrochemical biosensor for detection of human norovirus via novel specific binding peptides

Human noroviruses cause acute foodborne gastroenteritis outbreaks worldwide. In this study, a highly sensitive and selective electrochemical biosensor was fabricated for the detection of human norovirus using novel peptides as recognition elements. The electrochemical biosensor was fabricated by assembling of eight novel peptides separately on the gold electrode and investigated their efficiencies for sensing human noroviruses. Among eight peptides, NoroBP peptide coated onto the gold electrode exhibited a high binding affinity towards human noroviruses, resulting a progressive decrease in current signals with increasing concentration of human norovirus (0-105 copies/mL). As a result, NoroBP-nonFoul(FlexL)2-coated gold electrode acts an efficient electrochemical biosensor for highly selective detection of human norovirus with a detection limit of 1.7 copies/mL, which is 3-fold lower than the reported methods. The developed electrochemical biosensor was successfully applied to detect human norovirus prepared by standard procedure from oyster, which suggests that the developed biosensor can be used as a very sensitive and selective point-of-care bioanalytical platform for the detection of human norovirus in various food samples.

Gold-copper nanoshell dot-blot immunoassay for naked-eye sensitive detection of tuberculosis specific CFP-10 antigen

Herein, a straightforward and highly specific dot-blot immunoassay was successfully developed for the detection of Mycobacterium tuberculosis antigen (10u202fkDa culture filtrate protein, CFP-10) via the formation of copper nanoshell on the gold nanoparticles (AuNPs) surface. The principle of dot-blot immunoassay was based on the reduction of Cu2+ ion on the GBP-CFP10G2-AuNPs conjugates, which has gold binding and antigen binding affinities, simultaneously, favouring to appear red dot that can be observed with naked-eye. The dot intensity is proportional to the concentration of tuberculosis antigen CFP-10, which offers a detection limit of 7.6u202fpg/mL. The analytical performance of GBP-CFP10G2-AuNPs-copper nanoshell dot-blot was superior than that of conventional silver nanoshell. This method was successfully applied to identify the CFP-10 antigen in the clinical urine sample with high sensitivity, specificity, and minimized sample preparation steps. This method exhibits great application potential in the field of nanomedical science for highly reliable point-of-care detection of CFP-10 antigen in real samples to early diagnosis of tuberculosis.