Seiichi Ohta

Precise control of biosystems requires development of materials that can dynamically change physicochemical properties. Inspired by the ability of proteins to alter their conformation to mediate function, we explored the use of DNA as molecular keys to assemble and transform colloidal nanoparticle systems. The systems consist of a core nanoparticle surrounded by small satellites, the conformation of which can be transformed in response to DNA via a toe-hold displacement mechanism. The conformati

The blood-brain barrier (BBB) has hampered the efficiency of nanoparticle delivery into the brain via conventional strategies. The widening of BBB tight junctions via focused ultrasound (FUS) offers a promising approach for enhancing the delivery of nanoparticles into the brain. However, there is currently an insufficient understanding of how nanoparticles pass through the opened BBB gaps. Here we investigated the size-dependence of nanoparticle delivery into the brain assisted by FUS-induced BB

Abstract Status of C, N, and P including available N and P was studied in 35 Typic Paleudults and Typic Hapludults under a “Lowland Dipterocarp Forest” in East Kalimantan, Indonesia. The total C, N, and P contents decreased abruptly within the top 15–20 cm layers. The contents were directly correlated with the clay content in each horizon group. The higher C, N, and P contents in the finer soils were considered to be associated with the stabilization of organic matter by clay particles and with

Hyaluronan (HA) is a promising drug carrier for cancer therapy because of its CD44 targeting ability, good biocompatibility, and biodegradability. In this study, cisplatin (CDDP)-incorporating HA nanogels were fabricated through a chelating ligand-metal coordination cross-linking reaction. We conjugated chelating ligands, iminodiacetic acid or malonic acid, to HA and used them as a precursor polymer. By mixing the ligand-conjugated HA with CDDP, cross-linking occurred via coordination of the lig

Abstract Thirty five Typic Paleudults and Typic Hapludults under a Lowland Dipterocarp Forest were characterized for clay minerals, free oxides, cation exchange capacity, and exchangeable bases. Kaolinite was predominant in the soil clays followed by quartz, vermiculite and gibbsite and an accessory amount of illite, partially-interlayered-vermiculite (PIV) and goethite in most soils. Goethite formation appeared to take place concomitantly with the weathering of illite into PIV. Lepidocrocite wa

Abstract Morphological and physical properties of 35 Typic Paleudults and Typic Hapludults, the major soils of the “Lowland Dipterocarp Forest” in East Kalimantan were investigated. The soil morphology was related to the texture, and occasionally to the geomorphology. The coarse soils were distinguished from the fine ones by the more frequent occurrence of gray and rusty mottles in the epipedons, thicker albic horizons, thinner cutan development in the argillic horizons, weaker mottling in the s

Intraperitoneal administration of chemotherapeutics is expected for the treatment of peritoneally disseminated gastric cancer because of poor migration of the drugs from the systemic circulation to the peritoneal cavity. In this study, for intraperitoneal delivery of cisplatin (CDDP), we developed a hyaluronan (HA)-based hybrid system in which CDDP-loaded HA nanogels were either physically encapsulated in or chemically conjugated to injectable HA hydrogels. Physical encapsulation enabled sustain

Abstract To analyze the influences of prolonged grassland conditions after deforestation on tropical soils, soils under a natural Dipterocarp forest and grassland in Central Luzon, the Philippines were compared with each other in terms of morphology, clay mineralogy, physicochemical properties, nitrogen fertility, and humus composition. The influence of forest land degradation on the soil was limited to the shallow superficial horizon in the case of the Plinthic Acrisols, but extended to the E o

Abstract The influence of afforestation on the soil of grasslands denuded for a long period of time was studied in plantations of 5-year-old Acacia auriculiformis and 8-year-old Pinus kesiya in comparison with the soils of adjacent denuded grasslands in Central Luzon, the Philippines. Soils where Acacia and Pinus grew were Ferralic Cambisols derived from Quaternary sediment containing large amounts of ironstone nodules and Chromic Vertisols from Tertiary mudstone, respectively. Soil physical pro

Aggregates of luminescent silicon quantum dots (Si-QDs) selectively label certain organelles, such as lysosomes, endoplasmic reticulum, cytosol and nuclei, depending upon the size of the aggregates and their surface properties. We used Si-QDs in an aggregated form and the size of aggregates was controlled from ca. 30 to 270 nm diameter. In fixed human umbilical vein endothelial cells (HUVECs), allylamine-terminated Si-QDs selectively labeled cell nuclei, while Si-QDs, treated by the amphiphilic

Using amine-modified silicon quantum dots (Si-QDs) with visible photoluminescence as a building block, drug-loaded Si-QD aggregates were assembled. The aggregates were designed to break down in response to the endosomal pH decrease, which enabled the selective intracellular release of the loaded drugs.