Dae-Hwan Park

DNA Core@Inorganic Shell

A chemically well-defined Bio Core@Inorganic Shell nanohybrid, which consists of rationally designed DNA molecule core with a size of ∼100 nm and spherical inorganic nanoshell with an overall thickness of ∼10 nm reassembled with exfoliated layered metal hydroxide (MH nanosheets), is prepared. The DNA encapsulation and its release, due to the pH-dependent solubility of the MH nanoshell, plays a crucial role in maximizing the stability of base sequence-manipulated and probe-functionalized DNA molecules with designed information. The present DNA Core@MH Shell nanohybrid can provide wide bioinspired applications converged with nanotechnology, such as an advanced gene delivery system and a biomedical diagnostics, tracing/collection/sensing system for DNA-based information.

Biodegradable Inorganic Nanovector: Passive versus Active Tumor Targeting in siRNA Transportation

The biodegradable inorganic nanovector based on a layered double hydroxide (LDH) holds great promise for gene and drug delivery systems. However, in vivo targeted delivery of genes through LDH still remains a key challenge in the development of RNA interference therapeutics. Here, we describe in vivo and in vitro delivery system for Survivin siRNA (siSurvivin) assembled with passive LDH with a particle size of 100 nm or active LDH conjugated with a cancer overexpressing receptor targeting ligand, folic acid (LDHFA), conferring them an ability to target the tumor by either EPR-based clathrin-mediated or folate receptor-mediated endocytosis. When not only transfected into KB cells but also injected into xenograft mice, LDHFA/siSurvivin induced potent gene silencing at mRNA and protein levels in vitro, and consequently achieved a 3.0-fold higher suppression of tumor volume than LDH/siSurvivin in vivo. This anti-tumor effect was attributed to a selectively 1.2-fold higher accumulation of siSurvivin in tumor tissue compared with other organs. Targeting to the tumor with inorganic nanovector can guide and accelerate an evolution of next-generation theranosis system.

LDH Nanocontainers as Bio-Reservoirs and Drug Delivery Carriers

This review outlines research and patents relating to the use of inorganic nanomaterial, layered double hydroxide, as nanocontainers for drug delivery and gene reservoirs. Various intercalative synthetic routes including coprecipitation, ion exchange, reconstruction and exfoliation-reassembly have been explored to incorporate drug or gene molecules. Its unique two-dimensional structure allows layered double hydroxide to act as a nanospace for the stabilization, targeted delivery or controlled release of gene or drug molecules. Intercalative hybrid nanomaterials have uses such as pharmaceutically active ingredients, in oral- or cellular delivery systems, cosmetic ingredients, molecular coding units and etc. Toxicological studies have found layered double hydroxides to be biocompatible compared with widely used nanoparticles such as iron oxide, silica, and single-walled carbon nanotubes. Due to their versatile functionality and biocompatibility, layered double hydroxides have been widely studied and their applicability can be expanded to other nanoparticle based bio-medical applications.

Highly Ordered Nitrogen-Rich Mesoporous Carbon Nitrides and Their Superior Performance for Sensing and Photocatalytic Hydrogen Generation

Mesoporous carbon nitrides (MCN) are fascinating materials with unique semiconducting and basic properties that are useful in many applications including photocatalysis and sensing. Most syntheses of MCN focus on creating theoretically predicted C3 N4 stoichiometry with a band gap of 2.7 eV using a nano-hard templating approach with triazine-based precursors. However, the performance of the MCN in semiconducting applications is limited to the MCN framework with a small band gap, which would be linked with the addition of more N in the CN framework, but this remains a huge challenge. Here, we report a precursor with high nitrogen content, 3-amino-1,2,4-triazole, that enables the formation of new and well-ordered 3D MCN with C3 N5 stoichiometry (MCN-8), which has not been predicted so far, and a low-band-gap energy (2.2 eV). This novel class of material without addition of any dopants shows not only a superior photocatalytic water-splitting performance with a total of 801 μmol of H2 under visible-light irradiation for 3 h but also excellent sensing properties for toxic acids.

Drug-inorganic-polymer nanohybrid for transdermal delivery.

For transdermal drug delivery, we prepared a drug-inorganic nanohybrid (FB-LDH) by intercalating a transdermal model drug, flurbiprofen (FB), into the layered double hydroxides (LDHs) via coprecipitation reaction. The X-ray diffraction patterns and FT-IR spectra of the FB-LDH indicated that the FB molecules were successfully intercalated via electrostatic interaction within the LDH lattices. The in vitro drug release revealed that the Eudragit(®) S-100 in release media could facilitate the drug out-diffusion by effectively replacing the intercalated drug and also enlarging the lattice spacing of the FB-LDH. In this work, a hydrophobic gel suspension of the FB-LDH was suggested as a transdermal controlled delivery formulation, where the suspensions were mixed with varying amounts of Eudragit(®) S-100 aqueous solution. The Frantz diffusion cell experiments using mouse full-skins showed that a lag time and steady-state flux of the drug could be controlled from 12.8h and 3.28μgcm(-2)h(-1) to less than 1h and 14.57μgcm(-2)h(-1), respectively, by increasing the mass fraction of Eudragit(®) S-100 solution in gel suspensions from 0% to 20% (w/w), respectively. Therefore, we conclude gel formulation of the FB-LDH have a potential for transdermal controlled drug delivery.

Hollow Fibers Networked with Perovskite Nanoparticles for H2 Production from Heavy Oil

Design of catalytic materials has been highlighted to build ultraclean use of heavy oil including liquid-to-gas technology to directly convert heavy hydrocarbons into H2–rich gas fuels. If the H2 is produced from such heavy oil through high-active and durable catalysts in reforming process that is being constructed in hydrogen infrastructure, it will be addressed into renewable energy systems. Herein, the three different hollow fiber catalysts networked with perovskite nanoparticles, LaCr0.8Ru0.2O3, LaCr0.8Ru0.1Ni0.1O3, and LaCr0.8Ni0.2O3 were prepared by using activated carbon fiber as a sacrificial template for H2 production from heavy gas oil reforming. The most important findings were arrived at: (i) catalysts had hollow fibrous architectures with well-crystallized structures, (ii) hollow fibers had a high specific surface area with a particle size of ≈50 nm, and (iii) the Ru substituted ones showed high efficiency for H2 production with substantial durability under high concentrations of S, N, and aromatic compounds.

Energy efficient synthesis of highly ordered mesoporous carbon nitrides with uniform rods and their superior CO2 adsorption capacity

An energy efficient route for the synthesis of mesoporous carbon nitride (MCN) materials with highly ordered mesopores and a rod shaped morphology from uncalcined mesoporous SBA-15 (SEW-SBA-15) templates with a controlled morphology through a nanocasting technique using ethylenediamine and carbon tetrachloride as carbon and nitrogen sources is introduced. Porosity in the SBA-15 templates is created by washing with ethanol whereas the controlled rod shaped morphology in the nanotemplates is obtained by modifying the synthesis conditions from stirring to static conditions. The prepared MCN from the SEW-SBA-15 templates retains the morphological and structural order of the template. By tuning the pore diameter of SEW-SBA-15, it is possible to prepare MCN with tuneable pore diameters, which exhibits a specific BET surface area of 596–655 m2 g−1, pore diameter of 2.8–5.7 nm, and specific pore volume of 0.49–0.89 cm3 g−1. These values are similar to those of MCN-1 prepared from the calcined SBA-15 template with an irregular morphology. The SEW-MCN-1-T samples are used as CO2 adsorbents at 0, 10 and 25 °C and pressures from 1 up to 30 bar. Among the samples, the SEW-MCN-1-130 sample with the highest specific surface area, uniform particle size and morphology, and the largest pore volume exhibits the highest CO2 uptake capacity of 15.4 mmol g−1 at 0 °C and 30 bar, which is similar to the sample prepared by the calcination route but higher than that of activated carbon and multiwalled carbon nanotubes. This is the first report of the MCN prepared from uncalcined SBA-15 which helps to avoid the required energy intensive calcination step of the template and offers a promising system for CO2 capture.

Influence of anionic surface modifiers on the thermal stability and mechanical properties of layered double hydroxide/polypropylene nanocomposites

Organo-layered double hydroxide/polypropylene (LDH/PP) nanocomposites were successfully synthesized via a solution blending method. As an attempt to improve the compatibility with hydrophobic PP, the LDH surface was modified by the incorporation of various anionic surfactants via electrostatic interaction with LDH cationic layers. Surfactants were selected by considering the aliphatic carbon chain length (laurate, palmitate, stearate and dodecyl sulfate) and anionic functional groups (–COO−, –OPO32−, and –OSO3−) with the purpose of optimizing the homogeneous dispersion in the PP matrix. In PP nanocomposites containing LDH modified with alkyl carboxylate, the (00l) X-ray diffraction (XRD) peaks originating from organo-LDH were not observed, indicating that organo-LDH layers were fully exfoliated and homogeneously dispersed within the PP matrix, which were also confirmed by cross-sectional TEM analysis. However, PP nanocomposites containing LDH modified with dodecyl sulfate and lauryl phosphate showed broad (00l) XRD peaks, indicating that organo-LDH was partially exfoliated. According to the thermogravimetric analysis, the thermal stability (T0.5) of organo-LDH/PP nanocomposites was significantly improved by 37–60 K, depending on the type and loading content of organo-LDH compared to that of pristine PP. PP nanocomposites containing well-dispersed organo-LDH showed substantial enhancement of the elastic modulus with little decrease of tensile strength. These results are due to the increased interface volume fraction provided by the exfoliated LDH nanosheets.

Highly Stable Nanocontainer of APTES-Anchored Layered Titanate Nanosheet for Reliable Protection/Recovery of Nucleic Acid

A universal technology for the encapsulative protection of unstable anionic species by highly stable layered metal oxide has been developed via the surface modification of a metal oxide nanosheet. The surface anchoring of (3-aminopropyl)triethoxysilane (APTES) on exfoliated titanate nanosheet yields a novel cationic metal oxide nanosheet, which can be universally used for the hybridization with various biological and inorganic anions. The encapsulation of deoxyribonucleic acid (DNA) in the cationic APTES-anchored titanate lattice makes possible the reliable long-term protection of DNA against enzymatic, chemical, and UV−vis light corrosions. The encapsulated DNA can be easily released from the titanate lattice via sonication, underscoring the functionality of the cationic APTES-anchored titanate nanosheet as a stable nanocontainer for DNA. The APTES-anchored titanate nanosheet can be also used as an efficient CO2 adsorbent and a versatile host material for various inorganic anions like polyoxometalates, leading to the synthesis of novel intercalative nanohybrids with unexplored properties and useful functionalities.

Diaminotetrazine based mesoporous C3N6 with a well-ordered 3D cubic structure and its excellent photocatalytic performance for hydrogen evolution

Novel nitrogen enriched diamino-s-tetrazine based highly ordered 3D mesoporous carbon nitride (MCN-9) hybrid materials with a body centered cubic Ia3d structure having high specific surface areas, large pore volumes, and tunable pore diameters were prepared by employing 3D body centered cubic KIT-6 mesoporous silica having a gyroidal porous structure and various pore diameters as the sacrificial hard template through a simple self-condensation followed by polymerization reaction of aminoguanidine hydrochloride inside the nanochannels of the KIT-6 template. Characterization results reveal that the prepared materials exhibit a 3D porous structure with well-defined mesopores and possess excellent physical parameters including high surface areas (157–346 m2 g−1), large pore volumes (0.36–0.63 cm3 g−1), different pore diameters (5.5–6.0 nm) and a high N/C ratio of 1.87, which is much higher than that of ideal C3N4 (1.33). The deep yellow colored MCN-9 with a 3D porous structure also shows good absorption properties with a tunable narrow bandgap of 2.25–2.5 eV, which is again much lower than that of C3N4 (2.7 eV) and helps to achieve much higher photocatalytic water splitting activity than non-porous C3N4 and other carbon nitrides under visible light irradiation.