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Abstract: A new enzymatic process for production of l-theanine was presented using glutaminase combined with immobilization technique on carbon-coated mesoporous silica (carbon/SBA-15). For the attempt to enhance the durability against high pH conditions, the pore surface of mesoporous silica SBA-15 was coated with a thin layer of carbon. Carbon coating was done by addition of 2,3-dihydroxynaphthalene (DN) on the pore surface, followed by a dehydration reaction between surface silanol groups in SBA-15 and hydroxyl groups of DN molecules, and further carbonization of DN. A glutaminase was confined in nanospace (about 5nm) of carbon/SBA-15. The resulting product, glutaminase/carbon/SBA-15, successfully catalyzed the reaction for production of l-theanine under high pH conditions. [Copyright &y& Elsevier]

Abstract: A novel mesoporous silica (TMPS) was synthesized via self-assembly using a myristic acid ester of pentaglycerol. The ester is obtained from catalytic esterification and it is commercially available as a food grade emulsifier. TMPS material was employed for preparation of a biocatalyst in order to examine the ability as an enzyme support in comparison with the other mesoporous silica materials having a channel or a cage-like pore system. The used TMPS materials possessed the interconnected channel-like pore system with the pore sizes of 9.2, 12, and 16nm. The materials successfully entrapped lipase into their mesopores with the high loadings. The resultant lipase/TMPS conjugates functioned as the biocatalyst for hydrolysis of p-nitrophenyl propionate (p-NPP), having the higher activity than those of the used mesoporous silica conjugates. The high activities were ascribed to the textural properties such as the small particle length, large pore size and the three-dimensional pore connectivity that permit the accessibility of p-NPP to the immobilized lipases during the reactions. Consequently, we concluded that TMPS materials are of the suitable mesoporous support for the enzymes. [Copyright &y& Elsevier]

Abstract: We have successfully developed an electrochemical biosensor which could detect low level concentration of misty lactic-acid (LA) directly. In our method, enzyme lactate oxidase (LOD) was immobilized within mesoporous silica (FSM8.0) which was formed on screen-printed Prussian Blue (PB)-modified working electrode and the top of that was covered with hydrophilic porous membrane. The resulting biosensor showed an excellent sensitivity (150nM-1.1mM in solution) and can detect misty LA directly. This result indicates that our method provides a high-performance biosensor to determine LA levels in exhaled breath and that our approach is ideal for various medical applications and might improve the detection or management of disease. [Copyright &y& Elsevier]

Abstract: Laccase was immobilized in mesoporous silica powder with a 7.0nm pore diameter (FSM7.0) coated onto a glassy carbon electrode using an electrophoretic deposition technique, and the electrode was then applied to the amperometric detection of catechol, which is a typical phenolic compound. The behavior of a biosensor attached to the electrode was examined in terms of pH, applied potential, sensitivity and operational range, selectivity, and storage stability. The sensor showed an optimum response at a pH of 5.0 and at an applied potential of −50mV. The determination range and the response time for catechol were 2.0–100μM and approximately 2min, respectively. In addition, the sensor was quite stable and retained its initial response without notable change after being stored for over 50 days. This result suggests that our method is quite useful for the fabrication of a high-performance biosensor for practical use. [Copyright &y& Elsevier]

Abstract: The assembly and relative orientation of two fluorescent proteins (sGFP and DsRed) encapsulated in four kinds of mesoporous silica – namely, ethanol-treated folded-sheet mesoporous materials (FSMs) with different pore sizes (i.e. pore diameters of 2.6, 3.7, 5.4, and 7.1nm) – were confirmed directly using a fluorescence resonance energy-transfer (FRET) technique. The physicochemical properties of the ethanol-treated FSMs were analyzed finely by powder X-ray diffraction, and nitrogen adsorption/desorption measurements. When sGFP and DsRed were encapsulated in the FSM mesopores, the sGFP–DsRed–FSMs composites showed a notable FRET signal, indicating that the composites function as an energy-transfer system through the combination of the two proteins, due to the successful encapsulation of the sGFP–DsRed pairs in the pores. The FRET signal indicates the possibility of a high level of accessibility between sGFP and DsRed, as encapsulated in the same FSM channels. Interestingly, the FRET efficiency depended highly on the FSM pore size. In the case of the protein concentration of 1 and 2mg/mL, FRET efficiency reached to a maximum value at a pore diameter of 3.7nm (FSM3.7). In contrast, the proteins encapsulated in FSM2.6 (i.e. pore diameter of 2.6nm), which would arrange both sGFP and DsRed tandemly along the one-direction pores, indicated a higher FRET efficiency at 4mg/mL. These results strongly demonstrated that FRET efficiency depends on not only the distance between the proteins, but also the relative orientation of the proteins encapsulated in the pores. [Copyright &y& Elsevier]

Abstract: We assembled a highly durable conjugate with both a high-density accumulation and a regular array of lipase, by encapsulating it in mesoporous silica (FSM) with alkyltrimethylammonium (CTAB) chains on the surface. The activity for hydrolyzing esters of the lipase immobilized in mesoporous silica was linearly related to the concentration of lipase, whereas that of non-immobilized lipase showed saturation due to self-aggregation at a high concentration. The lipase conjugate also had increased resistance to heating when stayed in the silica coupling with CTAB. In addition, encapsulating the enzyme with FSM coupled CTAB caused the lipase to remain stable even in the presence of urea and trypsin, suggesting that the encapsulation prevented dissociation and denaturing. This conjugate had much higher activity and much higher stability for hydrolyzing esters when compared to the native lipase. These results show that FSM provides suitable support for the immobilization and dispersion of proteins in mesopores with disintegration of the aggregates. [Copyright &y& Elsevier]

Abstract: Acetylcholine sensor is successfully prepared by using immobilized enzymes, i.e., acetylcholinesterase and choline oxidase within separate hybrid mesoporous silica membranes with 12nm pore diameter (F127M). The measurement was based on the detection of hydrogen peroxide produced by two sequential enzyme reactions. The determination range and the response time are 6.0–800μM and within approximately 3min, respectively. The sensor is very stable compared to free enzymes and 80% of the initial response was maintained even after storage for 80 days. These results show that two enzymes are successfully immobilized and well stabilized, and at the same time, two sequential enzyme reactions efficiently proceed within the separate hybrid mesoporous membranes. Further, we studied the possible detection of organophosphorus pesticides in terms of the inhibition of acetylcholinesterase activity, i.e., the decrease of current response, and demonstrated that the nanomolar concentrations of pesticide (DZN-oxon) can be detected with our sensor. [Copyright &y& Elsevier]

Abstract: Catalase was confined in a nanospace of about 7nm in diameter in mesoporous silica (FSM; folded-sheet mesoporous material), forming a catalase-FSM conjugate. That the enzyme was encapsulated in the pores of mesoporous materials was proven by the direct visualization technique. The catalase-FSM showed not only an activity similar to that of the native catalase in the decomposition of H2O2 but also much higher stability: specifically, the catalase immobilized in FSM still retained its original activity after being applied 50 times to the decomposition, whereas the native lost its activity after 20 times recycling. Furthermore, the catalase-FSM showed catalase activity even in an organic media in which the native catalase had almost no catalytic activity. [Copyright &y& Elsevier]

Abstract: Mesoporous silica materials have a potential application for enzyme immobilization, which increases the stability of enzymes. We report the development of a novel detection method based on biosensors comprising an immobilized enzyme in mesoporous silica materials (i.e., FSM8.0 or P123-M), an electrochemical mediator (i.e., quinone), and an electrochemical cell, using the enzyme formaldehyde dehydrogenase. These biosensors exhibit a rapid response and high sensitivity, and they can detect 1.2μM of formaldehyde in an aqueous solution (corresponding to sub-ppb atmospheric concentration of formaldehyde). Furthermore, the sensors exhibit high selectivity, reusability, and a remarkable storage stability (stable over 80 days), indicating that formaldehyde dehydrogenase retains its highly ordered structure in these mesoporous silica materials. These results indicate that mesoporous silica materials can provide favorable methods for enzyme immobilization on the electrode and they are useful for developing high-performance electrochemical biosensors. [Copyright &y& Elsevier]

Chlorophyll a was adsorbed to mesoporous silica (FSM, folded-sheet mesoporous material) to form a chlorophyll-FSM conjugate, in which a nanometer-scale interaction between chlorophyll a molecules resembles a living plant leaf. The mesopores of FSM acted as nanoscale spaces not only for an interaction between chlorophyll molecules and the silica support but also for a nanoscale interaction between the absorbed chlorophyll molecules. These interactions contribute to photostability. An increase in the amount of chlorophyll adsorbed to the pores of FSM leads to an enhancement of the photostability accompanied by a shift in the absorbance maximum to a longer wavelength. The physiological function of the chlorophyllFSM conjugate was explored as chlorophyll-FSM exhibited the photoinduced ability to catalyze the reduction of methyl viologen (an electron carrier). The evolution of hydrogen gas was observed for 14 h without deterioration when an aqueous suspension containing chlorophyll-FSM, methyl viologen, 2-mercaptoethanol (an electron donor), and platinum was illuminated with visible light. [ABSTRACT FROM AUTHOR]

Abstract: In this study, a direct visualization technique was applied to the determination of a hetero-enzyme co-encapsulated in pores of mesoporous silicas in solution. Lipase and trypsin modified with fluorescent dyes, used as model enzymes, were co-encapsulated at the same instant in two kinds of mesoporous silicas – FSM-22 and SBA-15 – with pore diameters of 4.2 and 7.1nm, respectively. A direct observation of composite materials of a hetero-enzyme and a mesoporous silica by a combination of differential interference contrast and fluorescence microscopy revealed that the enzymes were uniformly dispersed throughout the particles of the mesoporous silicas, because of the successful incorporation of the two enzymes. Moreover, lipase and trypsin co-encapsulated in the mesopores maintained their enzymatic activities in hydrolysis reactions of their substrates (triglyceride and casein, respectively), without loss of their enzymatic activities due to structural degradation. [Copyright &y& Elsevier]

Abstract: A polydimethylsiloxane/glass microfluidic reactor containing lipase–mesoporous silica (FSM-22) conjugates has been successfully constructed without chemical cross-linking between enzyme and support. A direct visualization of conjugates of lipase and FSM-22 immobilized in the microreactor by optical microscopy revealed that the enzymes were uniformly dispersed throughout the particles of the FSM-22, because of the successful immobilization of the enzyme. Moreover, the lipase–FSM-22 conjugates contained in the microreactor indicated higher enzymatic activity in hydrolysis of triglyceride, as compared with a batch experiment. These results demonstrate that the microreactor using mesoporous silica performs not only the reagent-less enzyme immobilization but also the high reactivity of the enzyme. [Copyright &y& Elsevier]

Abstract: We present a new enzymatic process for synthesis of l-theanine using glutaminase combined with immobilization technique on a mesoporous silica (MPS). The MPS was firstly attempted to modify with zirconia in order to enhance the durability against the reaction under high pH conditions. The glutaminase on the MPS successfully catalyzed the reaction for the synthesis of l-theanine. The glutaminase/MPS conjugate was subsequently recovered and employed for the reaction again. The conjugate showed the corresponding activity to the first synthesis. This indicates that the conjugate functions as a catalyst for synthesis of l-theanine, having the operational stability sufficient for reuse. [ABSTRACT FROM AUTHOR]

Acid-base equilibria and effective proton concentration inside a silica mesopore modified with a tnmethyl ammonium (TMAP) layer were studied by steady-state fluorescence experiments. The mesoporous silica with a dense TMAP layer (1.4 molecules/nm ) was prepared by a post grafting of N tiimethoxysilylpropyl-N,N,N-trimethylammoflium at surfactant-temptated mesoporous silica (diameter of silica framework =3.1 nm). The resulting TMAP-modified mesoporous silica strongly adsorbed of anionic fluorescence indicator dyes (8-hydroxypyrene-l,3,6-trisulfonate (pyranine), 8-amino pyrene-1,3,&trisulfonate (APTS), 5,l0,IS,20 tetraphenyl21H,23H-porphifletetrasullonic acid disulfuric acid (TPPS), 2-naplittiol- 3,6-disulfonate (2NT)) and fluorescence excitation spectra of these dyes within TMAP-m9dled mesoporous silica were measured by varying the solution pH. The fluorescence experiments revealed that the acid-base equilibnum reactions of all pH indicator dyes within the TMAP-modifled silica mesopore were quite different from those in bulk water. From the analysis of the acid-base equilibrium of pyranine, the following relationships between solution pH (pHpore) and the effective proton concentration inside the pore (pHpore) were obtained (1) shift of pHpore was 1.8 (dipHpore = 1.8) forthe pHpore change from 2.1 to 9.1 (dipHpore = 7.0); (2) pHpore was not simply proportional to pHpore (3) the inside of the TMAP-modified silica mesopore was suggested to be in a weak acidic or neutral condition when pHpore, was changed from 2.0 to 9.1. Since these relationships between pHpore and pHpore could explain the acid-base equilibria of other pH indicator dyes (AJ'TS, TPPS, 2NT), these relationships were inferred to describe the effective proton concentration inside the TMAP-modifled silica mesopore. [ABSTRACT FROM AUTHOR]

Abstract: One-dimensional (1D) nanomaterials have unique applications due to their inherent physical properties. In this study, hexagonally ordered mesoporous silica hybrid anodic alumina membranes (AAM) were synthesized using template-guided synthesis with a number of nonionic n-alkyl-oligo(ethylene oxide), Brij-type (C x EO y ), which are surfactants that have different molecular sizes and characteristics. The hexagonal mesoporous silicas are vertically aligned in the AAM channels with a predominantly columnar orientation. The hollow mesostructured silicas had tunable pore diameters varying from 3.7 to 5.1nm. In this synthesis protocol, the surfactant molecular natures (corona/core features) are important for the controlled generation of ordered structures throughout AAM channels. The development of ultrafiltration membranes composed of silica mesostructures could be used effectively in separating silver nanoparticles (Ag NPs) in both aqueous and organic solution phases. This would be relevant to the production of well-defined Ag NPs with unique properties. To create a size-exclusive separation system of Ag NPs, we grafted hydrophobic trimethylsilyl (TMS) groups onto the inner pores of the mesoporous silica hybrid AAM. The immobilization of the TMS groups allowed the columnar mesoporous silica inside AAM to retain this inner pore order without distortion during the separation of solution-phase Ag NPs in organic solvents that may cause tortuous-pore membranes. Mesoporous TMS-silicas inside 1D AAM channels were applicable as a size-exclusive separation system to isolate organic solution-phase Ag NPs of uniform morphology and size. [Copyright &y& Elsevier]