We prepared microspheres densely covered with oligo-DNA strands by immobilizing amino-terminated oligo-DNA strands on the surface of carboxylate polystyrene latex (PS) particles via the amide bond formation. The obtained microspheres (ssDNA-PS) stably dispersed in neutral pH buffer containing high concentrations of NaCl. For the ssDNA-PS ≥1 m diameter, only 3%-5% of surface-immobilized oligo-DNA could form a duplex with the complementary strands. Nevertheless, the resulting ssDNA-PS showed a distinct duplex terminal dependency in their dispersion behavior under neutral pH and high NaCl conditions; the microspheres with fully-matched duplexes on the surface spontaneously aggregated in a non-crosslinking manner. By contrast, the microspheres with terminal-mismatched duplexes remained dispersed under the identical conditions. These results suggest that the micrometer-scale particles covered with oligo-DNA strands also have high susceptibility to a duplex terminal sequence in their dispersion property, similar to previously reported DNA-functionalized nanoparticles. This property could potentially be used in various applications including analytical purpose.

The dispersion behavior of DNA duplex-carrying colloidal particles in aqueous high-salt solutions shows extraordinary selectivity against the duplex terminal sequence. We investigated the interparticle force between DNA duplex-carrying polystyrene (dsDNA-PS) microparticles in aqueous salt solutions and examined their behavior in relation to the duplex terminal sequences. Force−distance (F−D) curves for a pair of dsDNA-PS particles were recorded with a dual-beam optical tweezers system with the two optically trapped particles closely approaching each other. Interestingly, only 3− 5% of the oligo-DNA strands on the dsDNA-PS particles formed a duplex with complementary DNAs, and the F−D curves showed a distinct specificity to the duplex terminal sequences in the interparticle force at a high-NaCl concentration; a clear attraction peak was observed in F−D curves only when the duplex terminal was a complementary base pair. The attractive strength reached 2.6 ± 0.5 pN at 500 mM NaCl and 4.3 ± 1.0 pN at 750 mM NaCl. By sharp contrast, no significant attraction occurred for the particles with mismatched duplex terminals even at 750 mM NaCl. Similar duplex terminal-specificity in the interparticle force was also confirmed for dsDNA-PS particles in divalent MgCl 2 solutions. Considering that the duplex terminal sequences on the dsDNA-PS particles showed only a negligible difference in their surface charges under identical salt conditions, we concluded that the interparticle attraction observed only for the dsDNA-PS particles with complementary duplex terminals is attributable to the salt-facilitated stacking interaction between the paired terminal nucleobases (i.e., blunt-end stacking) on the dsDNA-PS surfaces. Our results thus demonstrate the occurrence of a duplex terminal-specific interparticle force between dsDNA-PS particles under high-salt conditions.

In this study, we developed a new method to extract mycelial fibers from the fruiting bodies of mushrooms without destroying their structure. After chemical treatment with NaOH and H2O2, the fruiting bodies were decolorized via an environmentally friendly method using sunlight irradiation. The visible light reflectance of decolorized fruiting bodies was more than 80%. Ultrasonic treatment was used to defibrillate the fruiting bodies at the mycelial level, and a white micrometer-sized dispersion of mycelial fibers (mycelium pulp) was obtained. The mycelium retained its structure, demonstrating a thick linear mycelium pulp (width: 8.0 ± 3.4 μm) in Flammulina velutipes and a thin branched mycelium pulp (width: 2.3 ± 0.6 μm) in Ganoderma lucidum. The mycelium pulp is a completely new material that maintains its mycelial structure, unlike previously reported materials derived from fruiting bodies. The mycelium pulp demonstrates excellent deformability and can be used to create one- to three-dimensional deformable products, showing a wide range of material applicability.