Jung-Hyurk Lim

Polymer-Coated Tips for Patterning of Viruses by Dip-Pen Nanolithography†

Methods have recently been developed to allow the study of protein–protein and cell–surface interactions on a molecular level. These techniques rely on nanoscale arrays for highthroughput analysis of biological functions. Researchers working in areas including biosensors, biodiagnostics, genomics, proteomics, cytology, materials science, and general chemistry have benefited from these advances. To further drive this technology, high-precision patterning techniques are necessary to allow a wider range of biomolecules to be deposited onto a substrate. A variety of methods including UV lithography, electron-beam lithography, contact printing, nanoimprinting, and scanning probe lithography have been used to deposit biomolecules on various surfaces with nanometer accuracy. One such technique is dip-pen nanolithography (DPN). DPN is a scanning probe lithography method based on atomic force microscopy (AFM). Using DPN, nanostructure patterns of extraordinary complexity can be created. This technique has potential applications for gene chips and multiple biomolecular arrays because one can create patterns with numerous molecules in a directwrite fashion. The driving force of DPN for transporting materials is molecular diffusion through the water meniscus formed between the AFM tip and the surface. Although DPN provides a simple and efficient method to deposit DNA, peptides, and proteins on surfaces at nanoscale resolution, most DPN methods struggle with higher-molecular-weight biomolecules. Molecules larger than 15 nm (the maximum size of most immunoglobulin G proteins) are not efficiently transported through this water meniscus. Recently, many strategies have been employed to solve this problem by modifying tip surfaces, and by adding carrier materials to ink solutions. For example, Mirkin and co-workers published a description of a polymer-pen lithography (PPL) method, in which elastomeric tips without cantilevers are used to deliver ink solutions. These tips, which are made entirely of poly(dimethylsiloxane) (PDMS), make it possible to control feature sizes by varying the tip–substrate contact time and contact force. However, no general methods have been developed that would allow the direct-write DPN technique to create patterns of large-sized biomaterials such as viruses. Herein, we describe a novel and effective method for fabricating porous polymer-coated AFM tips, which overcome the shortcomings of DPN, such as the difficulty of transporting large bioparticles and the limited amount of ink solution that can be delivered. Using this tip, we have generated patterns of adeno-associated viruses (AAVs). Our approach uses a nanoporous poly(2-methyl-2-oxazoline) (PMeOx)-coated tip (Scheme 1). A bare SiO2 AFM tip was first modified with 11-iodoundecyltrichlorosilane as an initiator through a silanization reaction. This active layer was then used to initiate the ring-opening polymerization of 2methyl-2-oxazoline monomer, which resulted in the formation of nanopore network structures. A typical scanning electron microscopy (SEM) image of the fabricated PMeOxcoated tip shows that the pore sizes ranged from 50 nm to a few hundred nanometers (Figure 1a). The AFM image of PMeOx, taken under ambient conditions, showed similar nanopore structures (Figure S1 in the Supporting Information). PMeOx is a well-characterized, hydrophilic, biocompatible, and water-soluble nonionic polymer that is often used for drug delivery. A variety of PMeOx hydrogels can be formed by chemically cross-linking a hydrophilic polymer matrix through covalent bonds or by physically cross-linking with hydrogen bonds. In our method, when the PMeOx-coated AFM tip is brought into contact with an aqueous ink solution, the surface-immobilized porous polymer layer absorbs the ink solution and forms a swollen hydrogel. Because the AAV used [*] Y.-H. Shin, S.-H. Yun, S.-H. Pyo, Y.-S. Lim, H.-J. Yoon, K.-H. Kim, Prof. K.-M. Kim, Prof. J.-H. Lim Department of Polymer Science and Technology Chungju National University 72 Daehangno, Chungju-si 380-702 (Korea) Fax: (+ 82)43-841-5420 E-mail: jhlim@cjnu.ac.kr

Interleukin-28A triggers wound healing migration of bladder cancer cells via NF-κB-mediated MMP-9 expression inducing the MAPK pathway

Interleukin (IL)-28A, also called IFN-λ2, is a member of the classIIcytokine family and has demonstrated anti-proliferative and anti-viral signals. The present study demonstrated migration inducement of IL-28A-treated bladder cancer cells - a novel function. RNA microarray analysis showed an enhanced expression of IL-28A and its receptor IL-28AR1 in muscle invasive urothelial carcinoma in a human bladder. Strong expression of IL-28A and IL-28AR1 was detected in bladder cancer tissues and cell lines (5637, T-24, and HT1376 cells), as determined by real-time PCR and immunoblot analysis. IL-28A treatment induced migration of bladder cancer cells, independent of the cell growth. IL-28AR1-specific small interfering RNA (si-IL-28AR1) inhibited the induction of migration in IL-28A-treated cells. IL-28A treatment stimulated the expression of matrix metalloproteinases-9 (MMP-9) via activation of transcription factor NF-κB. Gene knockdown for MMP-9 and the p65 subunit of NF-κB, using siRNA transfection, suppressed wound healing migration in IL-28A-treated bladder cancer cells. Also, treatment with IL-28A induced activation of mitogen-activated protein kinase (MAPK) in bladder cancer cells. MAPK function blockage by a MAPK-specific inhibitor showed that MAPK phosphorylation is required for IL-28A-induced MMP-9 expression through activation of NF-κB. The transient transfection of bladder cancer cells with ERK1/2 knock down (si-ERK1/2) and dominant negative p38 (DNp38) suppressed IL-28A-induced migration. IL-28A-induced induction of MMP-9 expression, MAPK activation, and DNA binding activity of NF-κB was abolished in the presence of IL-28A neutralizing antibody or by transfection of si-IL-28AR1. These results show that IL-28A/IL-28AR1 dyad-induced wound healing migration requires NF-κB-mediated MMP-9 expression by MAPK activation.

Fabrication of hybrid nanocomposites of poly(acrylic acid)-grafted MWNTs and spherical aggregates of palladium nanoparticles with POSS

In this report, hybrid nanocomposites were fabricated by poly(acrylic acid)-grafted multiwall carbon nanotubes (MWNTs) (PAA-grafted MWNTs) and spherical aggregates of palladium nanoparticles with cubic silsesquioxanes (Pd-POSS) through ionic interactions. The modification of MWNTs with PAA via in situ radical polymerization and self-organization of palladium nanoparticles by cubic silsesquioxanes (POSS) introduced negative and positive charge on the surface of MWNTs and Pd-POSS, respectively. Through electrostatic interactions, the positively charged Pd-POSS was physically attached to the surface of negatively charged PAA-grafted MWNTs. Pd-POSS were more densely and continuously deposited on the surface of PAA-grafted MWNTs than MWNTs-COOH due to the polymer effect. The characteristics of the hybrid nanocomposites were characterized by 1H-NMR, Fourier transform infrared, thermogravimetric analysis, differential scanning calorimetry, field-emission scanning electron microscopy, atomic force microscope, and energy dispersive spectrum.

Preparation and Characterization of Expanded Graphite Intercalation Compound/ UV-Crosslinked Acrylic Resin Pressure Sensitive Adhesives

The expanded graphite intercalated compound (xGIC)/pressure sensitive adhesives (PSAs) were prepared by syrup process and in situ process. The effects of xGIC filler on the morphology and property of acrylic resin based UV-crosslinked PSA were investigated. The xGICs showed more uniform dispersion in acrylic matrix and the degree of filler connection was more prominent in the syrup process than in situ process. The peel strength and tackiness of UV-crosslinked PSAs were strongly dependent on the amount of the filler and the peel strength decreased with increasing xGIC. The thermal conductivity of PSAs was explained in terms of filler dispersion, wetting, and matrix infiltration. The thermal conductivity of PSA was 0.46 W/mK by adding 20 wt% of xGIC, which was 287% improvement compared to the unfilled PSA. It is speculated that 2-dimensional xGIC fillers effectively formed the thermal pathway.

Synthesis and characterization of polycaprolactone-grafted carbon nanotubes via click reaction

Polycaprolactone (PCL) was covalently grafted on the surface of carbon nanotubes by a simple click reaction of propargyl-terminated PCL (propargyl-PCL) and carbon nanotubes (CNTs) containing azide groups (MWNT-N3). Propargyl-PCL was synthesized by the ring-opening polymerization of ε-caprolactone using propargyl alcohol and stannous octoate. MWNT-N3 was prepared from MWNT having 2-bromoisobutyryl groups (MWNT-Br) with sodium azide by azidation. The melting temperature of propargyl-PCL was shifted to the high temperature in PCL-grafted MWNT. The thermal stability of PCL-grafted MWNT was enhanced as compared to that of propargyl-PCL. PCL was coated on the surface of MWNT with a high density of PCL chains, which showed good solubility of PCL-grafted MWNT in organic solvents. PCL-grafted MWNT was characterized with FT-IR, 1H NMR, Raman, differential scanning calorimetry, thermogravimetric analysis, and scanning electron microscopy.

Synthesis and Characterization of Bridged Polysilsesquioxane Nanoparticles and Their Nanocomposites with Polycaprolactone by UV Irradiation

Spherical bridged polysilsesquioxane nanoparticles with thiol groups (BPS-SH) were prepared by the reduction of BPS with disulfide groups after the base-catalyzed hydrolysis and condensation reaction of bis(triethoxysilylpropyl)disulfide. The average size of BPS was around 100∼300 nm. Hydroxyethyl methacrylate (HEMA)-initiated polycaprolactone (PCL) was synthesized by ring-opening polymerization of caprolactone under the co-initiation of HEMA and Sn(Oct)2. New nanocomposites of BPS-SH and HEMA-PCL were fabricated by the photo-induced chemical reaction under a photoradical generator and ultraviolet light. BPS was fully and continuously covered with PCL, which resulted in the rough surface of BPS nanoparticles as well as the connected BPS nanoparticles together.

Fabrication of Hybrid Nanocomposites of PAA-grafted Graphene and Pd Nanoparticles having POSS (Pd-POSS)

The palladium nanoparticles were self-assembled to make Pd-POSS using POSS-NH3 + (polyhedral oligomeric silsesquioxane) as a crosslinker. Graphene oxide (GO) was produced by the reaction of graphite under a strong acid and oxidizer and poly(acrylic acid) (PAA) was covalently grafted on the surface of graphene to make PAA-grafted graphene through the radical polymerization of acrylic acid and GO along with a reduction process under NaBH4. The nanocomposites of Pd-POSS and PAA-grafted graphene were fabricated via ionic interactions between positively charged PdPOSS and negatively charged PAA-grafted graphene. Pd-POSS nanoparticles were attached to the surface of PAA-grafted graphene through ionic interactions. The thermal stability of Pd-POSS/PAA-grafted graphene was higher than that of PAA and PAA-grafted graphene. The composition, structure, surface morphology, and thermal stability of the Pd-POSS/ PAA-grafted graphene were studied by FE-SEM, AFM, TEM, FTIR, and TGA.

In-situ generation of spherical aggregates of Pd nanoparticles on the surface of poly(acrylic acid)-grafted MWNTs containing POSS

ABSTRACT PAA-grafted MWNTs containing POSS (POSS/PAA-grafted MWNTs) were synthesized by the simple mixing of octa(3-aminopropyl)octasils-esquioxane (POSS-NH3+) and PAA-grafted MWNTs via ionic interactions. The spherical aggregates of Pd nanoparticles on the surface of POSS/PAA-grafted MWNTs (Pd-POSS/MWNTs) were produced with an average size of 10–20 nm due to the effect of POSS-NH3+ used as a cubic linker physically attached to PAA-grafted MWNTs. The size of Pd-POSS/MWNTs was smaller than that of spherical aggregates of Pd nanoparticles prepared by only POSS-NH3+. The residual content of Pd-POSS/MWNTs is larger than that of POSS/PAA-grafted MWNTs because of the aggregates of Pd nanoparticles.

Fabrication of organic-inorganic bridged polysilsesquioxane (BPS) matrix containing polycarbonate diol (PCD) units for solid polymer electrolytes (SPEs)

ABSTRACT New type of solid polymer electrolytes (SPEs) were synthesized by polycarbonate diol (PCD)-based bridged polysilsesquioxane (BPS) monomer and lithium bis(trifluoromethane)sulfonimidate (LiTFSI) via the sol-gel process. The ion conductivity of PCD-based BPS matrix was increased from 1.41 × 10−7 to 4.09 × 10−5 ((Ω · cm)−1) according to the amount of lithium salts at room temperature. The effect of lithium salts to the ion conductivity is attributed to the homogenous dispersion of lithium salts into the SPEs matrix. The thermal stability of PCD-based BPS matrix is higher than that of PCD oligomer and PCD-based BPS monomer in thermogravimetric analysis (TGA).

Synthesis and characterization of PVP/PVA hydrogels using E-beam irradiation

A series of polyvinylpyrrolidone (PVP) hydrogels with different contents of polyvinylalcohol (PVA) have been prepared by E-beam irradiation. The gel fraction and strength of PVP/PVA hydrogels were increased with increasing the contents of PVA. On the contrary, the swelling degree was decreased. The PVP/PVA hydrogels were transparent and elastic, and have highly porous network.