Correct folding and assembling are essential for biopolymers to exhibit their inherent biological activities. We have designed ionic comb-type copolymers consisting of a polyion backbone and hydrophilic graft chains to engineer folding and assembling of biopolymers, such as DNA and peptides, having opposite ionic charges. The cationic copolymer formed soluble and soft inter-polyelectrolyte complex (IPEC) with DNA and acidic peptides. The copolymers significantly facilitate nucleic acid assembly including DNA duplex, triplex and quadruplex formations. Activities of functional DNAs such as molecular beacons and DNAzymes were enhanced by the copolymer. The cationic comb-type copolymers also facilitated folding of peptides having anionic charges. E5 peptide, a membrane active peptide, was folded into alpha-helical structure by the added copolymer. The copolymer/peptide mixture showed stronger membrane disrupting activity than peptide alone. Soluble and soft IPECs produced with the ionic comb-type copolymer are promising to improve function and applications of biopolymers.

Biomolecular motor system microtubule-kinesin can perform mechanical work by using chemical energy of ‘adenosine-5’-triphosphate’ (ATP) which is the fuel that provides energy to all living things. Using this fuel, biomolecular motors can produce a huge amount of energy almost 100 times larger than that of widely used electric motors. Modern technology is still far away from producing such a powerful molecular machine. By making the best use of this natural machine, we are aiming to design an artificial robot where biomolecular motors will be working as the central power generating unit.

Polymeric hydrogel particles (microgels) have “stimuli-responsiveness” and their physicochemical properties can be controlled by external stimuli such as temperature and pH. Moreover, microgels are swollen by water, which show Brownian motion, and also possess colloidal properties such as dispersing/flocculating. The authors have been studying microgels under the concept of “dimension and function control of polymeric hydrogel particles in microscopic spatial fields”, and it includes function control by utilizing self-organization in non-equilibrium system. In particular, when thermoresponsive poly(N-isopropyl acrylamide) (pNIPAm) microgel dispersions are dried, non-closepacked ordered structure of microgels are assembled on substrate. We focused on this phenomenon, and clarified the spontaneous structure formation process of pNIPAm microgels by observing the drying process. Furthermore, different from a very simple system such as “droplet drying”, we succeeded in the development of novel microgels (autonomously oscillating microgels) which periodically change their volume and interparticle interaction by coupling the pNIPAm microgels with chemical oscillation reaction (Belousov-Zhabotinsky (BZ) reaction). In this paper, we will mainly explain the study about “self-organization of microgels”, especially, the development of the autonomously oscillating microgels.

Abiotic colloids in nonequilibrium states exhibit various types of motion. Unlike thermal motions, these motions can be transformed into regular motions in space and time. They can exhibit self-organized patterns, active transport, stimuli-responsive behaviors, and/or chemotaxes. Although these characteristics resemble biological motions, abiotic systems are composed of much simpler chemicals. Because motions are generated near the interface where colloids exchange matter with their surroundings, the moving system must be on the colloidal scale. In this review, catalytic particles in solution, dispersions of oil/water system, the oil/water interface itself, and amphiphilic molecular assemblies are introduced with an emphasis on our studies. We discuss the emergence of regular motions from apparently random fluctuations, self-organized patterns from numerous elementary particles, separation of matter using active motions of abiotic colloids, motion control by coexisting cation species, and chemotactic dynamics shown by amphiphilic molecular assemblies.