Hyejoong Jeong

Robust superhydrophobic carbon nanofiber network inlay-gated mesh for water-in-oil emulsion separation with high flux

Much progress has been made toward applying super-wetting membranes to various oil–water separation processes with high molecular permeation flux. However, there are still numerous challenges in the simple preparation of extremely durable membranes with super-wetting properties, especially considering the great developments in high-flux membranes with nanometer-scale thickness. Previous membranes have been usually limited to either high durability with low selectivity or enhanced separation performance with low stability. Herein, an extremely robust carbon nanofiber-polydimethylsiloxane (CNFs-PDMS) network inlay-gated stainless steel mesh (SSM) that shows superhydrophobic and superoleophilic properties is presented. Carbon nanofibers are subtly deposited into SSM pores to form network fillers via an improved vacuum-based filtration. Most importantly, the SSM/CNFs-PDMS membrane exhibits excellent resistance to harsh environmental conditions such as acid, salt, organic, biofouling, and mechanical abrasion. In particular, mechanical damage to the inserted membrane can be avoided using the protective SSM, thereby ensuring super-wetting performance. In the present work, we propose a new concept of discrete or partial superhydrophobicity. Moreover, compared to previous superhydrophobic membranes, the thickness is significantly decreased, leading to enhanced oil-in-water emulsion separation flux. The membranes exhibit a gravity-driven water-in-oil emulsion separation with flux up to 2970 L m−2 h−1. This work provides a brand new route for designing durable and high-flux separation systems with an inlay-gated structure in the future by combining ultrathin membranes with protective supports.

The Effect of Silica Nanoparticles on Human Corneal Epithelial Cells.

Ocular drug delivery is an interesting field in current research. Silica nanoparticles (SiNPs) are promising drug carriers for ophthalmic drug delivery. However, little is known about the toxicity of SiNPs on ocular surface cells such as human corneal epithelial cells (HCECs). In this study, we evaluated the cytotoxicity induced by 50, 100 and 150 nm sizes of SiNPs on cultured HCECs for up to 48 hours. SiNPs were up-taken by HCECs inside cytoplasmic vacuoles. Cellular reactive oxygen species generation was mildly elevated, dose dependently, with SiNPs, but no significant decrease of cellular viability was observed up to concentrations of 100 μg/ml for three different sized SiNPs. Western blot assays revealed that both cellular autophagy and mammalian target of rapamycin (mTOR) pathways were activated with the addition of SiNPs. Our findings suggested that 50, 100 and 150 nm sized SiNPs did not induce significant cytotoxicity in cultured HCECs.

Multilayered Graphene Nano-Film for Controlled Protein Delivery by Desired Electro-Stimuli.

Recent research has highlighted the potential use of “smart” films, such as graphene sheets, that would allow for the controlled release of a variety of therapeutic drugs. Taking full advantage of these versatile conducting sheets, we investigated the novel concept of applying graphene oxide (GO) and reduced graphene oxide (rGO) materials as both barrier and conducting layers that afford controlled entrapment and release of any molecules of interest. We fabricated multilayered nanofilm architectures using a hydrolytically degradable cationic poly(β-amino ester) (PAE), a model protein antigen, ovalbumin (OVA) as a building block along with the GO and rGO. We successfully showed that these multilayer films are capable of blocking the initial burst release of OVA, and they can be triggered to precisely control the release upon the application of electrochemical potential. This new drug delivery platform will find its usefulness in various transdermal drug delivery devices where on-demand control of drug release from the surface is necessary.

Electronic Activation of a DNA Nanodevice Using a Multilayer Nanofilm

A method to control activation of a DNA nanodevice by supplying a complementary DNA (cDNA) strand from an electro-responsive nanoplatform is reported. To develop functional nanoplatform, hexalayer nanofilm is precisely designed by layer-by-layer assembly technique based on electrostatic interaction with four kinds of materials: Hydrolyzed poly(β-amino ester) can help cDNA release from the film. A cDNA is used as a key building block to activate DNA nanodevice. Reduced graphene oxides (rGOs) and the conductive polymer provide conductivity. In particular, rGOs efficiently incorporate a cDNA in the film via several interactions and act as a barrier. Depending on the types of applied electronic stimuli (reductive and oxidative potentials), a cDNA released from the electrode can quantitatively control the activation of DNA nanodevice. From this report, a new system is successfully demonstrated to precisely control DNA release on demand. By applying more advanced form of DNA-based nanodevices into multilayer system, the electro-responsive nanoplatform will expand the availability of DNA nanotechnology allowing its improved application in areas such as diagnosis, biosensing, bioimaging, and drug delivery.

The Effects of Nonporous Silica Nanoparticles on Cultured Human Keratocytes.

Purpose Silica nanoparticles (SiNPs) are promising carriers for ophthalmic drug delivery. In this study, we investigated the effect of various sizes of nonporous SiNPs on cultured human keratocytes. Methods Three different sizes of SiNPs (50, 100, and 150 nm) were manufactured. Primarily cultured human keratocytes were exposed to different concentrations (0, 25, 50, and 100 μg/mL) of three sizes of SiNPs for up to 72 hours. Intracellular reactive oxygen species (ROS) generation, cellular viability, lactate dehydrogenase (LDH) assay, autophagy, vimentin expression, and mammalian target of rapamycin (mTOR) pathway activation were evaluated. Intracellular distribution of SiNPs was evaluated with transmission electron microscopy. Results Transmission electron microscopy revealed SiNPs were taken up by keratocytes inside cytoplasmic vacuoles. Neither nuclear entry of SiNPs nor mitochondrial structural damage was observed. Both intracellular ROS generation and LDH level remained unchanged with up to 100 μg/mL SiNP treatment. Cellular viability was not affected by SiNP treatment. Autophagy showed significant dose-dependent activation with 50- and 100-nm SiNPs. However, mTOR activation remained unchanged. Vimentin expression did not show any significant increase with SiNPs. Conclusions Our findings suggested that 50-, 100-, and 150-nm SiNPs did not induce significant cytotoxicity in cultured human keratocytes at concentrations up to 100 μg/mL.

Drug Loading and Release Behavior Depending on the Induced Porosity of Chitosan/Cellulose Multilayer Nanofilms

The ability to control drug loading and release is the most important feature in the development of medical devices. In this research, we prepared a functional nanocoating technology to incorporate a drug-release layer onto a desired substrate. The multilayer films were prepared using chitosan (CHI) and carboxymethyl cellulose (CMC) polysaccharides by the layer-by-layer (LbL) method. By using chemical cross-linking to change the inner structure of the assembled multilayer, we could control the extent of drug loading and release. The cross-linked multilayer film had a porous structure and enhanced water wettability. Interestingly, more of the small-molecule drug was loaded into and released from the non-cross-linked multilayer film, whereas more of the macromolecular drug was loaded into and released from the cross-linked multilayer film. These results indicate that drug loading and release can be easily controlled according to the molecular weight of the desired drug by changing the structure of the film.

An Evaluation of the in vivo Safety of Nonporous Silica Nanoparticles: Ocular Topical Administration versus Oral Administration

Nonporous silica nanoparticles (SiNPs) have potential as promising carriers for ophthalmic drugs. However, the in vivo safety of ocular topical SiNPs remains unclear. This study investigated the in vivo safety of oral and ocular topical applications of 100 nm-sized SiNPs in Sprague-Dawley rats. The rats were divided into the following four groups: low-dose oral administration (total 100 mg/kg of SiNPs mixed with food for one week), high-dose oral administration (total 1000 mg/kg of SiNPs mixed with food for one week), ocular topical administration (10 mg/ml concentration, one drop, applied to the right eyes four times a day for one month), or a negative control (no SiNP treatment). The rats were observed for 12 weeks to investigate any signs of general or ocular toxicity. During the observation period, no differences were observed in the body weights, food and water intakes, behaviors and abnormal symptoms of the four groups. No animal deaths occurred. After 12 weeks, hematologic, blood biochemical parameters and ophthalmic examinations revealed no abnormal findings in any of the animals. The lack of toxicity of the SiNPs was further verified in autopsy findings of brain, liver, lung, spleen, heart, kidneys, intestine, eyeballs, and ovaries or testes.

In vitro blood cell viability profiling of polymers used in molecular assembly

Biocompatible polymers have been extensively applied to molecular assembly techniques on a micro- and nanoscale to miniaturize functional devices for biomedical uses. However, cytotoxic assessments of developed devices are prone to partially focus on non-specific cells or cells associated with the specific applications. Thereby, since toxicity is dependent on the type of cells and protocols, we do not fully understand the relative toxicities of polymers. Additionally, we need to ensure the blood cell biocompatibility of developed devices prior to that of targeted cells because most of the devices contact the blood before reaching the targeted regions. Motivated by this issue, we focused on screening cytotoxicity of polymers widely used for the layer-by-layer assembly technique using human blood cells. Cytotoxicity at the early stage was investigated on twenty types of polymers (positively charged, negatively charged, or neutral) and ten combination forms via hemolysis, cell viability, and AnnexinV-FITC/PI staining assays. We determined their effects on the cell membrane depending on their surface chemistry by molecular dynamics simulations. Furthermore, the toxicity of LbL-assembled nanofilms was assessed by measuring cell viability. Based on this report, researchers can produce nanofilms that are better suited for drug delivery and biomedical applications by reducing the possible cytotoxicity.

Safety of Nonporous Silica Nanoparticles in Human Corneal Endothelial Cells

Nonporous silica nanoparticles (SiNPs) are promising drug carrier platforms for intraocular drug delivery. In this study, we investigated the safety of three different sizes of SiNPs (50, 100, and 150 nm) in a human corneal endothelial cell (HCEC) line, B4G12. The HCECs were exposed to different concentrations (0, 25, 50, and 100 µg/ml) of three sizes of SiNPs for up to 48 h. Cellular viability, autophagy, lactate dehydrogenase (LDH) assay, and mammalian target of rapamycin (mTOR) pathway activation were evaluated. Intracellular distribution of the SiNPs was evaluated with transmission electron microscopy (TEM). TEM revealed that the SiNPs were up-taken by the HCECs inside cytoplasmic vacuoles. No mitochondrial structural damage was observed. Both cellular viability and LDH level remained unchanged with up to 100 µg/mL of SiNP treatment. Autophagy showed a significant dose-dependent activation with 50, 100, and 150 nm SiNPs. However, the mTOR activation remained unchanged. Human corneal tissue culture with 100 µg/ml concentrations of SiNPs for 72 h revealed no significant endothelial toxicity. In vivo corneal safety of the SiNPs (0.05 ml intracameral injection, 200 mg/ml concentration) was also verified in rabbit models. These findings suggested that 50, 100, and 150 nm SiNPs did not induce acute significant cytotoxicity in corneal endothelial cells at concentrations up to 100 µg/mL. However, long-term toxicity of SiNPs remains unknown.