Masao Gen

Immobilisation of cyclodextrin glucanotransferase into polyvinyl alcohol (PVA) nanofibres via electrospinning

Highlights • Fabrication of enzyme-carrying polymeric nanofibers by electrospinning.• PVA nanofibers structure and size were not affected by the addition of enzyme.• The electrospun CGTase/PVA nanofibers show excellent immobilisation efficiency.

Transformation of cyclodextrin glucanotransferase (CGTase) from aqueous suspension to fine solid particles via electrospraying

In this study, the potential of electrohydrodynamic atomization or electrospraying to produce nanometer-order CGTase particles from aqueous suspension was demonstrated. CGTase enzyme was prepared in acetate buffer solution (1% v/v), followed by electrospraying in stable Taylor cone-jet mode. The deposits were collected on aluminium foil (collector) at variable distances from the tip of spraying needle, ranging from 10 to 25 cm. The Coulomb fission that occurs during electrospraying process successfully transformed the enzyme to the solid state without any functional group deterioration. The functional group verification was conducted by FTIR analysis. Comparison between the deposit and the as-received enzyme in dry state indicates almost identical spectra. By increasing the distance of the collector from the needle tip, the average particle size of the solidified enzyme was reduced from 200±117 nm to 75±34 nm. The average particle sizes produced from the droplet fission were in agreement with the scaling law models. Enzyme activity analysis showed that the enzyme retained its initial activity after the electrospraying process. The enzyme particles collected at the longest distance (25 cm) demonstrated the highest enzyme activity, which indicates that the activity was controlled by the enzyme particle size.

Probing a dip-coated layer of organic molecules by an aerosol nanoparticle sensor with sub-100 nm resolution based on surface-enhanced Raman scattering

A surface coated with organic molecules has been probed by a sub 100 nm resolution particulate sensor by surface-enhanced Raman scattering (SERS) technique. The spatial distribution of those molecules formed on the solid surface was altered by a dip-coating method as a function of a substrate-lifting rate. Isolated silver nanoparticles (∼50 nm) as “antenna” particles were deposited from the gas phase onto the surface by means of an electrostatic-assisted spray. The surface with the particles was analyzed with Raman spectroscopy technique. These analyses provide spatial information on the molecules over the surface, when SERS spectra of the molecules obtained from each measurement point are converted into the position of molecules. The occurrence frequency of SERS is found to be correlated with the two-third power law of the lifting rate which is proportional to a mass concentration of molecules per unit area, whereas the average Raman intensity is independent. A gas-phase route assisted SERS technique offers direct measurement of the molecular patterns on target surfaces.

A Colloidal Route to Detection of Organic Molecules Based on Surface-Enhanced Raman Spectroscopy Using Nanostructured Substrate Derived from Aerosols

A detection method based on the surface-enhanced Raman spectroscopy (SERS)-active substrate derived from aerosol nanoparticles and a colloidal suspension for detecting organic molecules of a model analyte (a pesticide) is proposed. This approach can detect the molecules of the derived from its solution with the concentration levels of ppb. For substrate fabrication, a gas-phase method is used to directly deposit Ag nanoparticles on to a silicon substrate having pyramidal structures. By mixing the target analyte with a suspension of Ag colloids purchased in advance, clotianidin analyte on Ag colloid can exist in junctions of co-aggregated Ag colloids. Using (i) a nanostructured substrate made from aerosol nanoparticles and (ii) colloidal suspension can increase the number of activity spots.