Jaeyeong Choi

Proteins and antibodies in serum, plasma, and whole blood—size characterization using asymmetrical flow field-flow fractionation (AF4)

The analysis of aggregates of therapeutic proteins is crucial in order to ensure efficacy and patient safety. Typically, the analysis is performed in the finished formulation to ensure that aggregates are not present. An important question is, however, what happens to therapeutic proteins, with regard to oligomerization and aggregation, after they have been administrated (i.e., in the blood). In this paper, the separation of whole blood, plasma, and serum is shown using asymmetric flow field-flow fractionation (AF4) with a minimum of sample pre-treatment. Furthermore, the analysis and size characterization of a fluorescent antibody in blood plasma using AF4 are demonstrated. The results show the suitability and strength of AF4 for blood analysis and open new important routes for the analysis and characterization of therapeutic proteins in the blood.

Optimization of fractionation efficiency (FE) and throughput (TP) in a large scale splitter less full-feed depletion SPLITT fractionation (Large scale FFD-SF)

Split-flow thin cell fractionation (SPLITT fractionation, SF) is a particle separation technique that allows continuous (and thus a preparative scale) separation into two subpopulations based on the particle size or the density. In SF, there are two basic performance parameters. One is the throughput (TP), which was defined as the amount of sample that can be processed in a unit time period. Another is the fractionation efficiency (FE), which was defined as the number % of particles that have the size predicted by theory. Full-feed depletion mode (FFD-SF) have only one inlet for the sample feed, and the channel is equipped with a flow stream splitter only at the outlet in SF mode. In conventional FFD-mode, it was difficult to extend channel due to splitter in channel. So, we use large scale splitter-less FFD-SF to increase TP from increase channel scale. In this study, a FFD-SF channel was developed for a large-scale fractionation, which has no flow stream splitters (‘splitter less’), and then was tested for optimum TP and FE by varying the sample concentration and the flow rates at the inlet and outlet of the channel. Polyurethane (PU) latex beads having two different size distribution (about 3~7 µm, and about 2~30 µm) were used for the test. The sample concentration was varied from 0.2 to 0.8% (wt/vol). The channel flow rate was varied from 70, 100, 120 and 160 mL/min. The fractionated particles were monitored by optical microscopy (OM). The sample recovery was determined by collecting the particles on a 0.1 µm membrane filter. Accumulation of relatively large micron sized particles in channel could be prevented by feeding carrier liquid. It was found that, in order to achieve effective TP, the concentration of sample should be at higher than 0.4%.

Characterization of CdS-quantum dot particles using sedimentation field-flow fractionation (SdFFF)

Abstract: CdS-QD particles are a nano-sized semiconducting crystal that emits light. Their optical propertiesshow great potential in many areas of applications such as disease-diagnostic reagents, optical technologies,media industries and solar cells. The wavelength of emitting light depends on the particle size and thus thequality control of CdS-QD particle requires accurate determination of the size distribution. In this study, CdS-QD particles were synthesized by a simple γ-ray irradiation method. As a particle stabilizer polyvinyl pyrrolidone(PVP) were added. In order to determine the size and size distribution of the CdS-QD particles, sedimentationfield-flow fractionation (SdFFF) was employed. Effects of carious parameters including the the flow rate, externalfield strength, and field programming conditions were investigated to optimize SdFFF for analysis of CdS-QD particles. The Transmission electron microscopy (TEM) analysis show the primary single particle size was~4 nm, TEM images indicate that the primarty particles were aggregated to form secondary particles havingthe mean size of about 159 nm. As the concentration of the stabilizer increases, the particle size tends to decrease.Mean size determined by SdFFF, TEM, and dynamic light scattering (DLS) were 126, 159, and 152 nm,respectively. Results showed SdFFF may become a useful tool for determination of the size and its distributionof various types of inorganic particles. 요약: CdS 양자점 입자는 특정 파장의 빛을 방출하는 반도체 나노 결정으로 이러한 광학적 특성 때문에 질병 진단 시약, 광학기술, 미디어 산업 및 태양전지와 같은 다양한 분야에서 응용되는 물질이다. 방출하는 빛의 색은 입자의 크기에 의존하기 때문에 CdS 양자점 입자의 크기 및 크기분포를 정확하게 분석하는 것이 필요하다. 본 연구에서는 CdS 양자점 입자를 감마-선 조사법(γ-ray irradiation method)을 이용하여 합성하고, 크기 및 크기 분포도를 결정하기 위하여 침강 장-흐름 분획법 (SdFFF)를 이용하였다.