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In the last two decades, microfluidic technology has emerged as a highly efficient tool for the study of various chemical and biological reactions. Recently, we reported that high-throughput detection of various concentrations of a reagent is possible using a continuous gradient microfluidic channel combined with a surface-enhanced Raman scattering (SERS) detection platform. In this continuous flow regime, however, the deposition of nanoparticle aggregates on channel surfaces induces the "memory effect," affecting both sensitivity and reproducibility. To resolve this problem, a SERS-based gradient droplet system was developed. Herein, the serial dilution of a reagent was achieved in a stepwise manner using microfluidic concentration gradient generators. Then various concentrations of a reagent generated in different channels were simultaneously trapped into the tiny volume of droplets by injecting an oil mixture into the channel. Compared to the single-phase regime, this two-phase liquid/liquid segmented flow regime allows minimization of resident time distributions of reagents through localization of reagents in encapsulated droplets. Consequently, the sample stacking problem could be solved using this system because it greatly reduces the memory effect. We believe that this SERS-based gradient droplet system will be of significant utility in simultaneously monitoring chemical and biological reactions for various concentrations of a reagent.

We report the development of amplification-free surface-enhanced Raman scattering (SERS)-based DNA assays for the rapid and highly sensitive detection of prostate cancer antigen 3 (PCA3) mimic DNA. This technique does not require any DNA amplification process using thermo-cycles in conventional polymerase chain reaction (PCR) due to its highly sensitive detection capability. Herein, the PCA3 mimic DNA, composed of 45 nucleotide sequences, was sandwiched between two probe DNA-immobilized particles (ASO 735 -conjugated detection HGNs and ASO 683 -immobilized capture magnetic beads) by hybridization reactions. Its quantitative analysis was performed by monitoring the characteristic Raman peak intensity of sandwich DNA complexes. The limit of detection (LOD) is estimated to be 2.7 fM, which is about four orders of magnitude more sensitive than that of conventional PCR. This SERS-based DNA assay technique is expected to be a potentially useful tool for early disease diagnosis.

A surface-enhanced Raman scattering-based lateral flow assay (SERS-LFA) technique has been developed for the rapid and accurate diagnosis of scrub typhus. Lateral flow kits for the detection of O. tsutsugamushi IgG (scrub typhus biomarker) were fabricated, and the calibration curve for various standard clinical sera concentrations were obtained by Raman measurements. The clinical sera titer values were determined by fitting the Raman data to the calibration curve. To assess the clinical feasibility of the proposed method, SERS-LFA assays were performed on 40 clinical samples. The results showed good agreement with those of the standard indirect immunofluorescence assay (IFA) method. SERS-LFA has many advantages over IFA including the less sample volume, simpler assay steps, shorter assay time, more systematic quantitative analysis, and longer assay lifetime. As SERS strips can be easily integrated with a miniaturized Raman spectrophotometer, field serodiagnosis is also more feasible.

A surface-enhanced Raman scattering (SERS)-based lateral flow assay (LFA) strip using silica-encapsulated gold nanoparticles (Si-AuNPs) was developed for the diagnosis of mosquito-borne diseases—dengue fever, Zika virus, or malaria—which are endemic to tropical regions. To investigate the thermal stability of the SERS nanoprobes, Raman peak intensity variations for AuNPs and Si-AuNPs were measured and compared at 45°C. SERS mapping images of target human immunoglobulin (IgG) on the test line of the Si-AuNP-loaded LFA strip were also evaluated at the same temperature to test the reproducibility of detection. In this case, the distribution of Raman mapping points on the test line was relatively uniform compared with the AuNP-loaded LFA strips at 45°C. This indicates that the silica encapsulation on the surface of the AuNPs improves the reproducibility of the SERS nanoprobes at high temperatures. The limit of detection (LOD) value of the AuNP-loaded LFA strips was significantly increased when the temperature was increased from 25°C to 45°C. In the case of the Si-AuNP-loaded LFA strips, however, the LOD value at 45°C was almost the same as that at 25°C. This result also shows that the silica encapsulation of the AuNPs improves the thermal stability of the LFA strips at high temperatures. Thus, Si-AuNPs are reproducible and thermally stable labeling agents for use in LFA strips at high temperatures and are suitable for the preparation of rapid kits, which can be used in tropical areas.

Surface-enhanced Raman scattering (SERS)-based aptasensor platform, using double strand DNA-embedded Au/Ag core-shell nanoparticles, has been developed for the ultrasensitive detection of bisphenol A (BPA) in water. By combining optimally controlled Au/Ag core-shell nanoparticles with the selective BPA binding characteristics of DNA aptamers, a highly sensitive limit of detection (LOD) of 10 fM could be achieved for BPA-spiked tap water over a wide concentration range from 100 nM to 10 fM. This LOD is two or three orders of magnitude lower than that reported for other BPA sensing techniques, and also yields a detection limit that is 100-1000 times lower than the US EPA-defined Predicted No Effect Concentration (PNEC) values in potable water. Total detection time is estimated to be about 40 min including the reaction between aptamer and BPA (30 min) and detection (10 min). This sensing platform is also suitable for field applications since measurement can be performed under aqueous colloidal conditions.

APT attack has caused chaos in society since 2006. Especially, the vulnerability of the infrastructure is exposed to the outside a lot due to the development of the IT infrastructure in Korea. In addition, APT attacks targeting companies' major confidential information are increasing every year. APT attack causes negative publicity for the company and financial damage. APT is completely different from the problem which most organizations have been dealt with. Cyber-attack threats were visible in the past. But currently, APT attacks were invisible and focused on confidential data. Therefore, we need a new approach to solve this problem. We have to find traces of prejudice in the circumstances, everything seems normal. If we perform a correlation analysis of the log acquired from all the devices, systems and applications, we can easily understand the problems which occur in our information systems. Current commercial SIEM has the ability to visualize the correlation analysis and the log. But the security officer takes a lot of time to understand the visualized security logs. Moreover, due to expensive cost of SIEM solution, small companies have difficulty introducing SIEM solution. For these reasons, we have developed a SIEM solution based on open-source program such as D3 component which results in decreasing the cost of the program. In addition, we analyzed the D3 components which can visualize the security logs, and matched D3 components with the security logs. In this paper, we propose the visualization methods using D3 components for analyzing the security logs efficiently.