Se Geun Lee

Growth inhibition of aquatic plant caused by silver and titanium oxide nanoparticles

Emerging nanomaterials are of great concern to aquatic environment. The inhibitory effects of silver nanoparticles (Ag-NP) and titanium oxide nanoparticles (TiO2-NP) on the growth of aquatic plant duckweed were evaluated. Lemna paucicostata was used as a test organism, and the test method was followed by the OECD test guideline 221. Ag-NP (50 nm) and TiO2-NP (2–3 nm) inhibited the growth of Lemna in different manner and the EC50s were calculated as 13.8 and 538.5 ppm, respectively. The LOECs of Ag-NP and TiO2-NP were calculated to be 1 and 125 ppm, respectively. The results showed that Ag-NP could cause growth inhibition of Lemna in low concentration range (≥1 ppm), but TiO2-NP appeared toxic effect to the growth of Lemna in the concentration range of ≥250 ppm, which was over two orders higher than the previously reported concentration of TiO2-NP determined in the aquatic environment.

Antioxidative and antiinflammatory activities of quercetin-loaded silica nanoparticles

Utilizing the biological activities of compounds by encapsulating natural components in stable nanoparticles is an important strategy for a variety of biomedical and healthcare applications. In this study, quercetin-loaded silica nanoparticles were synthesized using an oil-in-water microemulsion method, which is a suitable system for producing functional nanoparticles of controlled size and shape. The resulting quercetin-loaded silica nanoparticles were spherical, highly monodispersed, and stable in an aqueous system. Superoxide radical scavenging effects were found for the quercetin-loaded silica nanoparticles as well as free quercetin. The quercetin-loaded silica nanoparticles showed cell viability comparable to that of the controls. The amounts of proinflammatory cytokines produced by macrophages, such as interleukin 1 beta, interleukin 6, and tumor necrosis factor alpha, were reduced significantly for the quercetin-loaded silica nanoparticles. These results suggest that the antioxidative and antiinflammatory activities of quercetin are maintained after encapsulation in silica. Silica nanoparticles can be used for the effective and stable incorporation of biologically active natural components into composite biomaterials.

Proteomic analysis of silver nanoparticle toxicity in rat

Silver nanoparticles (SNPs) have received considerable attention recently, because SNPs with different shapes and sizes exhibit variable antimicrobial activity, which makes them useful for medical and hygienic purposes. SNPs have been detected in various tissues and organisms after inhalation, oral ingestion, and contact with the skin, indicating that SNPs can be distributed to different body tissues after uptake. Thus, the toxicity of SNPs to different body tissues after their uptake needs to be studied. In this study, we performed a proteomic analysis of liver, lung, and kidney tissues in rats exposed to approximately 50 nm SNPs by intravascular injection. Then, the differentially expressed proteins representing a dose-dependent response were identified. The differentially expressed proteins were mostly related to the known toxicity of SNPs, such as apoptosis, increased reactive oxygen species, thrombus formation, and inflammation. Additionally, proteins related to metabolic disorders including diabetes were identified as differentially expressed proteins in kidney, based solely on the analysis of the protein profile and related disease pathway. In conclusion, the differentially expressed proteins identified in this study could provide basic data for understanding the toxic and pathological responses of SNP-exposed tissues and to identify candidate SNP toxicity biomarkers.

Selective detection of estradiol using a molecularly imprinted self-assembled monolayer on gold surface

Molecularly imprinted polymer (MIP) was synthesized to selectively detect estrogen-like chemicals depending on their shapes and binding characteristics to Estrogen Receptor (ER) active site. MIP was synthesized on self-assembled monolayer (SAM) formed by thiol-acrylate photopolymerization on Surface Plasmon Resonance (SPR) chip. The imprinting factor was calculated based on the shift of SPR angle at which the excitation of surface plasmons by light was minimum level. The imprinting factor, 4.3, was calculated by angle shift by SPR, which showed higher imprinting factor than the previous studies. We also validated the specificity of molecularly imprinted polymer loaded gold chip and compared the binding ability to estrogenicity known by in-vivo and in-vitro biological test. Molecular imprinting reflected the whole surface characteristics including three dimensional shape, types and location of functional groups, and distribution of interaction forces such as hydrogen bonding and van der Waals interaction. Therefore, MIP binding response could provide more insight on structure and estrogenic activity. Another purpose was to provide the basic data for future development of EDC screening array chip to find out various hormone activities at once.

Protein-Directed Immobilization of Phosphocholine Ligands on a Gold Surface for Multivalent C-Reactive Protein Binding

The preparation of a synthetic receptor for multivalent protein binding by a directed immobilization of bifunctional ligands was demonstrated using pentameric C-reactive protein (CRP) and a thiolated phosphocholine-containing ligand on a gold surface. CRP consisting of five identical, noncovalently linked subunits and having five phosphocholine-binding sites on the same face was complexed with 12-mercaptododecylphosphocholine. The complexes were reacted with a gold surface, which was blocked with BSA or 2-mercaptoethanol to avoid non-specific binding. CRP binding to the molecularly imprinted monolayer was investigated by surface plasmon resonance, exhibiting high sensitivity with a detection limit as low as 1 pM (0.12 ng/mL) and binding affinity (K(A) ~ 10(-7)-10(-9) M(-1)) comparable to that of immobilized anti- CRP.

Phosphocholine-Modified Magnetic Nanoparticles for Isolation of C-Reactive Protein from Human Serum

In the present study, we describe the easy isolation of C-reactive protein (CRP) from human serum using phosphocholine-modified magnetic nanoparticles (MNPs). A phosphocholine-based monomer, 3-(4)-vinylbenzyl-12-phosphorylcholine dodecanoate (VPC), was polymerized on methacrylate-coated MNPs and the resulting MNPs (VPC-MNPs) were assessed for their ability to isolate CRP from a human serum sample. CRP could be isolated from human serum with one adsorption step to VPC-MNPs within 1 h. The high purity of the isolated CRP fraction determined by SDS-PAGE indicates a good selectivity of VPC-MNPs for CRP binding. These results demonstrate the feasibility of using ligand-functionalized MNPs for rapid, easy, and efficient protein isolation.

Preparation of monodisperse poly(vinyl alcohol) (PVA) nanoparticles by dispersion polymerization and heterogeneous surface saponification

Monodisperse poly(vinyl alcohol) (PVA)/poly(vinyl acetate) (PVAc) nanoparticles with a skin-core structure were prepared through heterogeneous surface saponification of PVAc nanoparticles. For the preparation of PVAc nanoparticles with a uniform particle size distribution, vinyl acetate (VAc) was dispersion polymerized in a mixed solvent of ethanol and water using PVA with a low degree of saponification as a stabilizer. Increase of the amount of ethanol in media, the resulting PVAc nanoparticle size increases due to increasing solubility of VAc and oligomer PVAc. To preserve the sphericity and size uniformity of PVAc nanoparticles, we restricted saponification to the surface of the nanoparticles by using a small amount of aqueous sodium hydroxide solution. To determine the proper concentration of alkali solution for heterogeneous saponification, monodisperse PVAc nanoparticles were saponified with different concentrations of alkali solution at 25 °C for 0.5–3.0 h. The PVA/PVAc nanoparticles obtained by the heterogeneous saponification with 4 % (relative to the amount of the VAc) alkali solution for 2.0 h were uniformly shaped and monodispersed with diameter ranging from 428 to 615 nm. Transmission electron microscopy (TEM) confirmed the spherical nature and regular skin-core structure of the PVA/PVAc nanoparticles.

Color Stability of the Bioplastic containing Sorghum Extract Chelated by Fe(II) and Cu(II)

To improve the color stability of the bioplastic containing sorghum extract, sorghum extract was chelated by a metal ion. The chelating activity was quantitatively evaluated under the various conditions. Chelation of sorghum extract by Cu(II) was determined by reaction with pyrocatechol violet, whereas Fe(II) chelation was investigated by forming complexes with ferrozine. Chelation of sorghum extract was increased rapidly with increasing concentrations of metal salt and sorghum extract. At a 0.1g/L metal salt addition level, the chelating activity of Fe(II) and Cu(II) were 66.7% and 54.2%, respectively. According to the chelation pH conditions, the sorghum extract was chelated almost 100% by Fe(II) above the pH 6.5. It was confirmed that Fe(II) was a strong chelator of sorghum extract than Cu(II). The sorghum extract chelated with metal salt exhibit higher thermal stability. The bioplastic containing chelated sorghum extract showed relatively less color change than the control.