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Lee, Kyubae,Shin, Hanbyeol,Gupta, Kailash Chandra,Lee, Dong Yun,Park, Soo-Young,Kang, Inn-Kyu IEEE 2018 IEEE SENSORS JOURNAL Vol.18 No.20
<P>The 4-cyano- <TEX>$4^{\prime }$</TEX> -pentyl biphenyl (5CB) liquid crystals molecules are fascinating materials for the fabrication of sensors as they are able to show a detectable optical signal in presence of small variation in surface forces. The sensitivity of 5CB molecules increased further on using them as microdroplets emulsion as compared to layered structures on plannar solid surfaces. The anchoring of receptor (AIgG) on LC microdroplets makes microdroplets capable to produce species specific optical signal in presence of nonspecific interactions. Gold nanoparticles (GNPs) have increased the interactions of antigen (IgG) with LC microdroplets anchored AIgG. The concomitant emission of calcein green fluorescence on interactions of GNPs anchored esterase with LC microdroplet anchored calcein-AM has provided an evidence to confirm the interactions induced transition from radial to bipolar in LC microdroplets. The AIgG ( <TEX>$4.2~\mu \text{g}$</TEX>, 28 pmol) and calcein-AM ( <TEX>$4.8~\mu \text{g}$</TEX>, 4.55 nmol) anchored LC microdroplets within a size variation of 20- <TEX>$30~\mu \text{m}$</TEX> have shown a lower limit of detection of 0.22 ± 0.001 pmol of IgG in PBS (pH 7.4) within a contact time of 20 minutes. Thus, liquid crystals microdroplets have sufficient scope to develop biosensors for <I>in vitro</I> detection of disease causing antigens in biological fluids.</P>
Anti-IgG-anchored liquid crystal microdroplets for label free detection of IgG
Lee, Kyubae,Gupta, Kailash Chandra,Park, Soo-Young,Kang, Inn-Kyu The Royal Society of Chemistry 2016 Journal of materials chemistry. B, Materials for b Vol.4 No.4
<P>The orientational variation of 4-cyano-4′-pentyl biphenyl (5CB) molecules in LC microdroplets in response to IgG antigen (IgG) interactions has been utilized to develop a biosensor for rapid and label-free detection of IgG in biological fluids. In order to prepare a LC microdroplet-based biosensor, the anti-IgG (AIgG) anchored 4-cyano-4′-pentyl biphenyl LC microdroplets were prepared in the presence of sodium dodecylsulfate (SDS) as a mediator and amphiphilic poly(styrene-<I>b</I>-acrylic acid) (PS-<I>b</I>-PA) as a modifier of the LC/water interface. The AIgG-anchored LC microdroplets with a size variation from 20 to 30 μm have been used successfully for the detection of IgG within a concentration range of 20 to 1000 ng mL<SUP>−1</SUP>, at a detection limit of as low as 16 ng mL<SUP>−1</SUP>, and a response time of 30 min in PBS solution at room temperature. The LC microdroplets anchored with 5 μg mL<SUP>−1</SUP> of AIgG were found to be more sensitive for the detection of IgG in the concentration range from 20 to 800 ng mL<SUP>−1</SUP> in PBS. The AIgG-anchored LC microdroplets have shown a delayed response of 90 minutes for IgG in a solution containing 10% FBS or 10% blood plasma in comparison to PBS solution. The LC microdroplets anchored with 5 μg mL<SUP>−1</SUP> (34 pmol) of AIgG have shown a recovery of 106% of IgG, a coefficient of variance of ±4% and a precision within a limit of 1-6% for a spiked sample of 25 ng mL<SUP>−1</SUP> of IgG. The results indicated that orientational response of LC microdroplets is potentially useful to develop a biosensor for <I>in vivo</I> detection of proteins or pathogens in a biological fluid.</P>
Targeted images of KB cells using folate-conjugated gold nanoparticles
Rathinaraj, Pierson,Lee, Kyubae,Park, Soo-Young,Kang, Inn-Kyu Springer US 2015 NANOSCALE RESEARCH LETTERS Vol.10 No.1
<P>Mercaptosuccinic acid-coated gold (GM) nanoparticles were prepared and characterized by transmission electron microscopy and dynamic light scattering. Folic acid (F) was then conjugated to the GM to preferentially target oral squamous cancer (KB) cells with folate receptors expressed on their membranes and facilitate the transit of the nanoparticles across the cell membrane. Finally, a fluorescence dye (Atto) was conjugated to the nanoparticles to visualize their internalization into KB cells. After culture of the cells in a medium containing GM and folate-conjugated GM (GF), the interaction of surface-modified gold nanoparticles with KB cells was studied.</P>
Choi, Yuri,Lee, Kyubae,Gupta, Kailash C.,Park, Soo-Young,Kang, Inn-Kyu The Royal Society of Chemistry 2015 Journal of Materials Chemistry B Vol.3 No.44
<P>Liquid crystal (LC) microdroplets have been prepared for visual detection of HepG2 cells using 4-cyano-4′-pentyl biphenyl molecules in the presence of sodium dodecyl sulfate as a mediator and β-galactose-conjugated poly(styrene-<I>b</I>-acrylic acid) block copolymer (PS-<I>b</I>-PA-G) as a modifier of LC-water interfaces. To clarify the effect of β-galactose-containing ligands on the orientational transitions of LC microdroplets, maltotriose as a ligand simulant was conjugated to poly(styrene-<I>b</I>-acrylic acid) and used as a LC modifier. The interaction of HepG2 cells with the β-galactose-conjugated block copolymer was effective in causing orientational transitions, from radial to bipolar, in LC microdroplets, whereas interactions of HepG2 cells with maltotriose-conjugated block copolymers were ineffective in inducing orientational transitions in LC microdroplets. To confirm the necessity of the PS segment of the block copolymer for transmitting the ligand-receptor interaction forces from the interface to the core of the LC microdroplets, β-galactose-conjugated block copolymers (PS-<I>b</I>-PA-G) and homopolymers (PVLA) were synthesized and used to prepare LC microdroplets. The LC microdroplets containing a β-galactose-conjugated homopolymer did not show orientational transitions upon contact with HepG2 cells. However, LC microdroplets containing a β-galactose-conjugated block copolymer showed orientational transitions from radial to bipolar, indicating that the polystyrene segment in the amphiphilic block copolymer is essential for the effective transmission of ligand-receptor interactions to the core of LC microdroplets. β-Galactose anchored LC microdroplets were able to detect 1.0 ± 0.1 HepG2 cells per μm<SUP>2</SUP> of the test cell and had shown significantly high reproducibility (<I>p</I> < 0.05, <I>n</I> = 3). The configurational transition in LC microdroplets that was dependent on ligand-receptor interactions was used to develop a LC microdroplet-based biosensor for the detection of HepG2 cells in biological fluids.</P>