Search

For the encapsulation of biomolecules in inorganic materials, we have developed a unique enzyme-silicate conjugate material that consists of a self-assembled molecularly thin silicate layer on the surface of each individual enzyme molecule. The enzyme-silicate conjugate materials, called single enzyme caged nanoparticles (SECNs), were synthesized via the silica polymerization on the surface of enzyme molecule after solubilizing each enzyme molecule in hexane by using a tiny amount of surfactant, called “ion-pairing”. SECNs possess near native enzyme activity in aqueous media with minimal substrate diffusional limitations, and are highly stable under the protection of silicate network cage. Due to their nearly molecular size, SECNs can also be adsorbed into mesoporous silica materials to yield robust and easily-recyclable enzymatic systems that can be used in a number of potential biocatalytic applications such as diagnostics, biosensors, biotransformations, biofuel production, bioremediation and CO2 capture.

Protein digestion, using an enzyme called trypsin (TR), is one of the key steps in proteomic analysis. The current technology of protein digestion in proteomic analysis is time-consuming, tedious and not-automated due to the poor stability and autolysis of trypsin. To improve the protein digestion process, trypsin was immobilized and stabilized on polymer nanofibers entrapping superparamagnetic nanoparticles (magnetic nanofibers, NP-NFs). By electrospinning the homogeneous mixture of superparamagnetic nanoparticles (NPs) and polystyrene-poly(styrene-co-maleic anhydride), NPs could be effectively entrapped within polymer nanofibers, generating magnetically-separable nanofibers with high surface area for trypsin immobilization via the approach of enzyme coatings. Trypsin coatings on magnetic nanofibers (EC-TR/NP-NFs; EC-TR), fabricated via simple attachment of crosslinked trypsin molecules onto NP-NFs, were highly stable and could be recycled via facile magnetic separation. EC-TR showed negligible loss of trypsin activity even after incubation in an aqueous buffer under rigorous shaking (200 rpm) for 80 days, while the control samples of covalently-attached trypsin on NP-NFs (CA-TR/NP-NFs; CA-TR) and free trypsin lost more than 90% of their initial activities within 11 and 6 days, respectively. When highly-stable and magnetically-separable EC-TR was employed for the repetitive digestions of enolase under recycled uses for the duration of 50 days and even after treatment with another protease (chymotrypsin) for 32 h, the performance of enolase digestion was successfully maintained. The use of EC-TR for the enolase digestion in the ultra-sonication system resulted in fast (∼10 min) and efficient digestions with reproducible performance under recycled uses.

Gas separation membranes with polydimethylsiloxane(PDMS)/polystyrene(PS) were prepared by using the sequential interpenetrating polymer network (IPN) method with various PS contents (10–70wt%). These gas separation membranes can be applied to reduce the smoke density in the emission gas of diesel engines. PS content has a pronounced effect on the membrane performance. It was found that the optimized PS contents in the final membrane were 50wt%. The emission capacities of diesel engines used in this study were 632 cc and 11,149 cc. When the oxygen separation membrane was used in the diesel engines, the smoke density of both diesel engines was remarkably reduced (35–73%). The oxygen concentration in the inlet air affects the composition of the emission gases. Especially, hydrocarbon (HC) decreased with the increase of oxygen concentration.

Subtilisin Carlsberg (SC) was immobilized and stabilized on magnetically-separable mesoporous silica (Mag-MSU-F) in the form of nanoscale enzyme reactors (NERs) based on the ship-in-a-bottle mechanism. Stabilized NERs of SC (NER-SC) were freeze-dried and successfully used for the transesterification of N-acetyl-L-phenylalanine ethyl ester with n-propanol in isooctane. Magnetic separation of Mag-MSU-F facilitated the repeated usages of stable NER-SC. This is the first demonstration for the use of stable and magnetically-separable NERs in an organic solvent, which has the potential for environmentally-friendly synthesis using enzymes in organic solvents.