Preparation of Degradable and Transformable Core–Corona-Type Particles that Control Cellular Uptake by Thermal Shape Change

Particle–cell interactions, such as cellular uptake, vary depending on the particle size, shape, and surface properties. By dynamic control of the physical properties of particles, microparticle–cell interactions can intentionally be altered. Particle degradability is also necessary for their application in the body. In this study, we aimed to prepare degradable core–corona-type particles that are deformed near the body temperature and investigated particle shape-dependent cellular uptake. Degradable and transformable particles consisting of poly(2-methylene-1,3-dioxepane)-co-poly(ethylene glycol) with three-armed poly(ε-caprolactone) (PCL) were prepared. The particle melting point was controlled by the chain length of the three-armed PCL. Particle degradation occurred under both acidic and alkaline conditions via ester group hydrolysis in the polymer backbones. The rod-shaped microparticles prepared by uniaxial stretching at a temperature above the melting point of the core showed less uptake into macrophages than did the spherical microparticles. Therefore, the degradable transformable particles enable macrophage interaction control via stimuli-regulated particle shapes and are expected to be applied as drug delivery carriers that can be decomposed and excreted from the body

Thermoresponsive Nanospheres with a Regulated Diameter and Well-Defined Corona Layer

In the present work, we prepared core–corona-type nanospheres bearing a thermoresponsive polymer with a controlled chain length on their surface. The corona layers were composed of poly­(<i>N</i>-isopropylacrylamide) (PNIPAAm) chains (<i>M</i>_n = 3000–18 000) with a narrow polydispersity index prepared by atom-transfer radical polymerization (ATRP). Nanospheres were prepared by dispersion copolymerization of styrene with the PNIPAAm macromonomer in a polar solvent. The obtained nanospheres were monodisperse in diameter. The diameter of the nanospheres was regulated either by the number or chain length of the PNIPAAm macromonomers. In fact, the nanosphere diameter was regulated from ca. 100 to 1000 nm. When two types of PNIPAAm macromonomers are used, the obtained nanospheres have two different kinds of PNIPAAm on their surface. The surface of the nanospheres was observed to be thermoresponsive nanosphere in 0, 50, 100 mmol L^–1 NaCl aqueous solution. The nanosphere diameter and the surface-grafted polymer were concurrently adjusted for use in biomedical applications

Terminal-Functionality Effect of Poly(<i>N</i>‑isopropylacrylamide) Brush Surfaces on Temperature-Controlled Cell Adhesion/Detachment

Terminally functionalized poly­(<i>N</i>-isopropylacrylamide) (PIPAAm) brush grafted glass surfaces were prepared by a surface-initiated reversible addition-fragmentation chain transfer radical (SI-RAFT) polymerization. SI-RAFT mediated PIPAAm chains possessed terminal dodecyl trithiocarbonate groups which can be substituted with various functional groups. In this study, dodecyl groups were substituted with hydrophilic maleimide groups for controlling the thermoresponsive character of PIPAAm brushes. PIPAAm brushes exhibited reversible temperature-dependent surface wettability changes around PIPAAm’s lower critical solution temperature. Phase transition of dodecyl-terminated PIPAAm brushes clearly shifted to lower temperature than that of maleimide-terminated PIPAAm brushes, and this shift was attributed to promoted PIPAAm dehydration via terminal hydrophobes. By using this feature, the specific adhesion temperatures of bovine carotid artery endothelial cells (BAECs) on the PIPAAm brush surfaces were successfully controlled. BAECs were initiated to adhere on dodecyl-PIPAAm surfaces at 31 °C, while their adhesion was significantly suppressed on maleimide-PIPAAm surfaces under 33 °C. In contrast, terminal functionality scarcely affected the thermoresponsive behavior of PIPAAm brushes in the polymer rehydration process by reducing temperatures, and thus, the difference in spontaneous cell detachment from different PIPAAm-brush surface was negligible. Consequently, confluently cultured cells were able to be harvested as contiguous cell sheets from individual surfaces with comparable periods at 20 °C

Thermally Modulated Cationic Copolymer Brush on Monolithic Silica Rods for High-Speed Separation of Acidic Biomolecules

Poly­(<i>N</i>-isopropylacrylamide (IPAAm)-<i>co</i>-2-(dimethylamino)­ethylmethacrylate­(DMAEMA)-<i>co</i>-<i>tert</i>-butylacrylamide (tBAAm)), a thermoresponsive-cationic-copolymer, brush-grafted monolithic-silica column was prepared through surface-initiated atom transfer radical polymerization (ATRP) for effective thermoresponsive anion-exchange chromatography matrices. ATRP-initiator was grafted on monolithic silica-rod surfaces by flowing a toluene solution containing ATRP initiator into monolithic silica-rod columns. IPAAm, DMAEMA, and tBAAm monomers and CuCl/CuCl₂/Me₆TREN, an ATRP catalytic system, were dissolved in 2-propanol, and the reaction solution was pumped into the preprepared initiator modified columns at 25 °C for 16 h. The constructed copolymer-brush structure on monolithic silica-rod surface was confirmed by X-ray photoelectron spectroscopy (XPS), elemental analysis, scanning electron microscopy (SEM) observation, and gel permeation chromatography (GPC) measurement of grafted copolymer. The prepared monolithic silica-rod columns were also characterized by chromatographic analysis. The cationic copolymer brush modified monolithic silica-rod columns were able to separate adenosine nucleotides with a shorter analysis time (4 min) than thermoresponsive copolymer brush-modified silica-bead-packed columns, because of the reduced diffusion path length of monolithic supporting materials. These results indicated that thermoresponsive cationic copolymer brush grafted monolithic silica-rod column prepared by ATRP was a promising tool for analyzing acidic-bioactive compounds with a remarkably short analysis time

Monolithic Silica Rods Grafted with Thermoresponsive Anionic Polymer Brushes for High-Speed Separation of Basic Biomolecules and Peptides

Thermoresponsive anionic copolymer brushes, poly­(<i>N</i>-isopropylacrylamide-<i>co</i>-acrylic acid-<i>co</i>-<i>tert</i>-butylacrylamide) [P­(IPAAm-<i>co</i>-AAc-<i>co</i>-tBAAm)], were grafted onto a monolithic silica rod column through surface-initiated atom-transfer radical polymerization (ATRP) to prepare an effective thermoresponsive anionic chromatography matrix. An ATRP initiator was attached to the rod surface. <i>N</i>-Isopropylacrylamide (IPAAm), <i>tert</i>-butyl acrylate (tBA), <i>tert</i>-butylacrylamide (tBAAm), and the ATRP catalyst CuCl/CuCl₂/tris­[2-(<i>N</i>,<i>N</i>-dimethylamino)­ethyl]­amine were dissolved in 2-propanol, and the reaction mixture was pumped into the initiator-modified column. After grafting P­(IPAAm-<i>co</i>-tBA-<i>co</i>-tBAAm) on the monolithic silica surfaces, deprotection of the <i>tert</i>-butyl group of tBA was performed. Chromatographic analysis showed that the prepared column was able to separate catecholamine derivatives and angiotensin subtypes within a shorter analysis time (5 min) than a silica-bead-packed column modified with the same copolymer brush could. These results indicated that the prepared copolymer-modified monolithic silica rod column may be a promising bioanalytical and bioseparation tool for rapid analysis of basic bioactive compounds and peptides

High Stability of Thermoresponsive Polymer-Brush-Grafted Silica Beads as Chromatography Matrices

Thermo-responsive chromatography matrices with three types of graft architecture were prepared, and their separation performance and stability for continuous use were investigated. Poly­(<i>N</i>-isopropylacrylamide)­(PIPAAm) hydrogel-modified silica beads were prepared by a radical polymerization through modified 4,4′-azobis­(4-cyanovaleric acid) and <i>N</i>,<i>N</i>′-methylenebisacrylamide. Dense PIPAAm brush-grafted silica beads and dense poly­(<i>N-tert</i>-Butylacrylamide (tBAAm)-<i>b</i>-IPAAm) brush-grafted silica beads were prepared through a surface-initiated atom transfer radical polymerization (ATRP) using CuCl/CuCl₂/ Tris­(2-(<i>N</i>,<i>N</i>-dimethylamino)­ethyl)­amine (Me₆TREN) as an ATRP catalytic system and 2-propanol as a reaction solvent. Dense PIPAAm brush-grafted silica beads exhibited the highest separation performance because of their strong hydrophobic interaction between the densely grafted well-defined PIPAAm brush on silica-bead surfaces and analytes. Using an alkaline mobile phase, dense themoresponsive polymer brushes, especially having a hydrophobic basal layer, exhibited a high stability for continuous use, because polymer brush on the silica bead surfaces prevented the access of water to silica surface, leading to the hydrolysis of silica and cleavage of grafted polymers. Thus, the precisely modulating graft configuration of thermoresponsive polymers provided chromatography matrices with a high separation efficiency and stability for continuous use, resulting in elongating the longevity of chromatographic column

Rapid and Easy Extracellular Vesicle Detection on a Surface-Functionalized Power-Free Microchip toward Point-of-Care Diagnostics

Extracellular vesicles (EVs) are promising novel cancer biomarkers. However, rapid and easy analysis of EVs is challenging because conventional detection methods require large sample volumes and long detection times. Microchip-based analytical systems have particularly attracted attention for development of point-of-care (POC) diagnostics. Previously, various biomarker detection methods on a portable power-free poly­(dimethylsiloxane) (PDMS) microchip using laminar flow-assisted dendritic amplification have been developed. Recently, for easy functionalization, we proposed a microchannel inner surface-functionalized power-free PDMS microchip (SF-PF microchip) utilizing electron beam-induced graft polymerization. In this study, we apply the technique and prepare a novel SF-PF microchip. On the microchip, EVs were successfully detected. The required sample volume was 1.0 μL, and the total analysis time was 20 min. The microchip can contribute to EV-based POC cancer diagnosis

Demonstration of thermo-sensitive tetra-gel with implication for facile and versatile platform for a new class of smart gels

<p>A tertiary branched poly(N-isopropylacrylamide) with controlled molecular weight, distribution and the end amino-functionalization (tetra-PNIPAAm-NH₂) was studied for the ability to form a gel via <i>in situ</i> chain-end reaction with a counterpart tertiary branched poly(ethyleneglycol) bearing N-hydroxysuccinimide end groups (tetra-PEG-NHS), a well-documented class of building block to yield the tetra-gel. Some of these polymers, both comparable and distinct (relative to the counterpart) extended chain length pairs, provided a self-standing and macroscopically homogeneous gel, which was capable of undergoing thermo-sensitive and reversible change in hydration in line with the nature of PNIPAAm. Phantom network model based calculation indicated that a half molar fraction of the polymer chains in the network remained unreacted, revealing further room for optimizing the reaction condition. Since such tetra-PNIPAAm based motif can be readily tailored to a variety of other physicochemical stimuli-responsive analogues, our finding may give important insight into a platform for ‘smart’ tetra-gels with exceptional mechanical properties and potentially highly controllable molecular cut-off capability.</p

Bundle Gel Fibers with a Tunable Microenvironment for in Vitro Neuron Cell Guiding

As scaffolds for neuron cell guiding in vitro, gel fibers with a bundle structure, comprising multiple microfibrils, were fabricated using a microfluidic device system by casting a phase-separating polymer blend solution comprising hydroxypropyl cellulose (HPC) and sodium alginate (Na-Alg). The topology and stiffness of the obtained bundle gel fibers depended on their microstructure derived by the polymer blend ratio of HPC and Na-Alg. High concentrations of Na-Alg led to the formation of small microfibrils in a one-bundle gel fiber and stiff characteristics. These bundle gel fibers permitted for the elongation of the neuron cells along their axon orientation with the long axis of fibers. In addition, human-induced pluripotent-stem-cell-derived dopaminergic neuron progenitor cells were differentiated into neuronal cells on the bundle gels. The bundle gel fibers demonstrated an enormous potential as cell culture scaffold materials with an optimal microenvironment for guiding neuron cells