Juno Lee

Cytoprotective Silica Coating of Individual Mammalian Cells through Bioinspired Silicification

The cytoprotective coating of physicochemically labile mammalian cells with a durable material has potential applications in cell-based sensors, cell therapy, and regenerative medicine, as well as providing a platform for fundamental single-cell studies in cell biology. In this work, HeLa cells in suspension were individually coated with silica in a cytocompatible fashion through bioinspired silicification. The silica coating greatly enhanced the resistance of the HeLa cells to enzymatic attack by trypsin and the toxic compound poly(allylamine hydrochloride), while suppressing cell division in a controlled fashion. This bioinspired cytocompatible strategy for single-cell coating was also applied to NIH 3T3 fibroblasts and Jurkat cells.

Nanocoating of single cells: from maintenance of cell viability to manipulation of cellular activities.

The chronological progresses in single-cell nanocoating are described. The historical developments in the field are divided into biotemplating, cytocompatible nanocoating, and cells in nano-nutshells, depending on the main research focuses. Each subfield is discussed in conjunction with the others, regarding how and why to manipulate living cells by nanocoating at the single-cell level.

Artificial spores: cytoprotective nanoencapsulation of living cells

In this Opinion we discuss the development of artificial spores and their maturation as an independent field of research. The robust cell-in-shell structures have displayed unprecedented characteristics, which include the retardation of cell division and extensive cytoprotective capabilities that encompass exposure to osmotic pressure, shear force, heat, UV radiation, and lytic enzymes. Additionally, the nanothin shells act as highly versatile scaffolds for chemical functionalization to equip cells for implementation in tissue engineering, biosensors, cell therapy, or other biotechnological applications. We also explore the future direction of this emerging field and dictate that the next phase of research should focus on attaining more intricate engineering to achieve stimulus-responsive shell-degradation, multilayer casings with orthogonal functions, and the encapsulation of multiple cells for multicellular artificial spores.

Generation of ultra-high-molecular-weight polyethylene from metallocenes immobilized onto N-doped graphene nanoplatelets.

Catalytic natures of organometallic catalysts are modulated by coordinating organic ligands with proper steric and electronic properties to metal centers. Carbon-based nanomaterials such as graphene nanoplatelets are used with and without N-doping and multiwalled carbon nanotube as a ligand for ethylene polymerizations. Zirconocenes or titanocenes are immobilized on such nanomaterials. Polyethylenes (PEs) produced by such hybrids show a great increase in molecular weight relative to those produced by free catalysts. Specially, ultra-high-molecular-weight PEs are produced from the polymerizations at low temperature using the hybrid with N-doped graphene nanoplatelets. This result shows that such nanomaterials act a crucial role to tune the catalytic natures of metallocenes.

Magnetotactic molecular architectures from self-assembly of β-peptide foldamers

The design of stimuli-responsive self-assembled molecular systems capable of undergoing mechanical work is one of the most important challenges in synthetic chemistry and materials science. Here we report that foldectures, that is, self-assembled molecular architectures of β-peptide foldamers, uniformly align with respect to an applied static magnetic field, and also show instantaneous orientational motion in a dynamic magnetic field. This response is explained by the amplified anisotropy of the diamagnetic susceptibilities as a result of the well-ordered molecular packing of the foldectures. In addition, the motions of foldectures at the microscale can be translated into magnetotactic behaviour at the macroscopic scale in a way reminiscent to that of magnetosomes in magnetotactic bacteria. This study will provide significant inspiration for designing the next generation of biocompatible peptide-based molecular machines with applications in biological systems.

Axon-First Neuritogenesis on Vertical Nanowires

In this work, we report that high-density, vertically grown silicon nanowires (vg-SiNWs) direct a new in vitro developmental pathway of primary hippocampal neurons. Neurons on vg-SiNWs formed a single, extremely elongated major neurite earlier than minor neurites, which led to accelerated polarization. Additionally, the development of lamellipodia, which generally occurs on 2D culture coverslips, was absent on vg-SiNWs. The results indicate that surface topography is an important factor that influences neuronal development and also provide implications for the role of topography in neuronal development in vivo.

Effects Of Post Annealing And Oxidation Processes On The Removal Of Damage Generated During The Shallow Trench Etch Process

In this study, 0.3–0.5 µm deep silicon trenches were etched using Cl2/10%N2 and Cl2/50%HBr inductively coupled plasmas, and the defects remaining on the etched silicon trench surfaces and the effects of various annealing and oxidation on the removal of the defects were studied. High resolution transmission electron microscopy was used to investigate the degree of remaining defects and X-ray photoelectron spectroscopy was also used to investigate surface contamination of the etched silicon wafers. Defects were found on the silicon trench surfaces etched using both Cl2/10%N2 and Cl2/50%HBr. A thermal oxidation of 200 A at the temperature up to 1,100°C did not remove the remaining defects completely and more defects were remained on the silicon trench etched using Cl2/10%N2. More defects remaining on the oxidized silicon trench for Cl2/10%N2 appear to be related to the formation of silicon oxynitride on the silicon trench etched in Cl2/10%N2, therefore, forming less thermal oxide during the oxidation process. The annealing of the etched silicon trenches from 900°C to 1,000°C for 30 min in N2 also decreased the number of defects, however, to remove the defects formed in our experiments, the annealings at the temperature higher than 1,000°C in N2 for 30 min appears to be required. A combination process of annealing at 1,000°C and oxidation at 900°C was also effective in removing the defects completely.

Backfilling‐Free Strategy for Biopatterning on Intrinsically Dual‐Functionalized Poly[2‐Aminoethyl Methacrylate‐co‐Oligo(Ethylene Glycol) Methacrylate] Films

We demonstrated protein and cellular patterning with a soft lithography technique using poly[2-aminoethyl methacrylate-co-oligo(ethylene glycol) methacrylate] films on gold surfaces without employing a backfilling process. The backfilling process plays an important role in successfully generating biopatterns; however, it has potential disadvantages in several interesting research and technical applications. To overcome the issue, a copolymer system having highly reactive functional groups and bioinert properties was introduced through a surface-initiated controlled radical polymerization with 2-aminoethyl methacrylate hydrochloride (AMA) and oligo(ethylene glycol) methacrylate (OEGMA). The prepared poly(AMA-co-OEGMA) film was fully characterized, and among the films having different thicknesses, the 35 nm-thick biotinylated, poly(AMA-co-OEGMA) film exhibited an optimum performance, such as the lowest nonspecific adsorption and the highest specific binding capability toward proteins.

CHAPTER 4:Bioinspired Encapsulation of Living Cells within Inorganic Nanoshells

In this chapter, we describe methods for encapsulating individual cells within inorganic nanoshells. Inspired by the biomineralization that occurs in nature, living cells have been encapsulated within various inorganic shells made of gold, calcium phosphate, calcium carbonate, silica, or titania. The viability and metabolic activities of the cells were ensured by the careful selection of biocompatible materials and processes. Importantly, inorganic shells have been useful for enhancing long-term cell viability, controlling cell division, protecting the cytoplasm against foreign aggression, and functionalizing cell surfaces. This chapter focuses on the chemical reactions used to generate inorganic shells, categorized as direct reduction, in situ crystallization, and in situ condensation, and on the artificial control of the cellular behaviors conferred by the inorganic shells. The future prospects in the field of cell encapsulation within inorganic materials are also discussed.