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Bombyx mori silk/titania/gold hybrid materials for photocatalytic water splitting: combining renewable raw materials with clean fuels.

ABSTRACT: The synthesis, structure, and photocatalytic water splitting performance of two new titania (TiO2)/gold(Au)/Bombyx mori silk hybrid materials are reported. All materials are monoliths with diameters of up to ca. 4.5 cm. The materials are macroscopically homogeneous and porous with surface areas between 170 and 210 m2/g. The diameter of the TiO2 nanoparticles (NPs) - mainly anatase with a minor fraction of brookite - and the Au NPs are on the order of 5 and 7-18 nm, respectively. Addition of poly(ethylene oxide) to the reaction mixture enables pore size tuning, thus providing access to different materials with different photocatalytic activities. Water splitting experiments using a sunlight simulator and a Xe lamp show that the new hybrid materials are effective water splitting catalysts and produce up to 30 mmol of hydrogen per 24 h. Overall the article demonstrates that the combination of a renewable and robust scaffold such as B. mori silk with a photoactive material provides a promising approach to new monolithic photocatalysts that can easily be recycled and show great potential for application in lightweight devices for green fuel production.

SUBMITTER: Kruger S

PROVIDER: S-EPMC5789386 | biostudies-other | 2018

REPOSITORIES: biostudies-other

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Bombyx mori silk/titania/gold hybrid materials for photocatalytic water splitting: combining renewable raw materials with clean fuels.

Krüger Stefanie S Schwarze Michael M Baumann Otto O Günter Christina C Bruns Michael M Kübel Christian C Szabó Dorothée Vinga DV Meinusch Rafael R Bermudez Verónica de Zea VZ Taubert Andreas A

Beilstein journal of nanotechnology 20180117

The synthesis, structure, and photocatalytic water splitting performance of two new titania (TiO2)/gold(Au)/Bombyx mori silk hybrid materials are reported. All materials are monoliths with diameters of up to ca. 4.5 cm. The materials are macroscopically homogeneous and porous with surface areas between 170 and 210 m2/g. The diameter of the TiO2 nanoparticles (NPs) - mainly anatase with a minor fraction of brookite - and the Au NPs are on the order of 5 and ...[more]

PMID: 29441264

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Project description:Bombyx mori (B. mori) silk sericin is a protein with features desirable as a biomaterial, such as increased hydrophilicity and biodegradation, as well as resistance to oxidation, bacteria, and ultraviolet light. In contrast to other widely studied B. mori silk proteins such as fibroin, sericin is still unexplored as a building block for fabricating biomaterial, and thus a facile technique of processing it into a material is needed. Here, electrospinning technology was used to fabricate it into biomaterials from two forms of B. mori silk sericin with different molecular weights, one is a low (12.0 kDa) molecular sericin (LS) form and another is a high (66.0 kDa) molecular weight sericin (HS) form. Circular dichroism (CD) spectra showed that LS in hexafluoroacetone (HFA) solvent adopted a predominantly random coil conformation, whereas HS tended to form a β-sheet structure along with a large content of random coils. In addition, LS and HS in HFA solvent were found to form cylinder-like smaller nanoparticles and larger irregular aggregates before electrospinning, respectively. As a result, biomaterials based on microparticles and nanofibers were successfully fabricated by electrospinning of LS and HS dissolved in HFA, respectively. The cell viability and differentiation assay indicated that nanofibers and microparticles improved cell adhesion, growth, and differentiation, proving that the scaffolds electrospun from sericin are biocompatible regardless of its molecular weight. The microparticles, not common in electrospinning of silk proteins reported previously, were found to promote the osteogenic differentiation of mesenchymal stem cells in comparison to the nanofibers. This study suggested that molecular weight of sericin mediates its secondary structure and assembly structure, which in turn leads to a control of final morphology of the electrospun materials. The microparticles and nanofibers of sericin can be potentially used as building blocks for fabricating the scaffolds for tissue engineering.

Project description:To identify functions that distinguish the posterior and median cells producing fibroin and sericin in the silk gland of Bombyx mori, serial analysis of gene expression (SAGE) profiles from both silk gland regions were analyzed and compared. The construction of a B. mori reference tag collection extracted from a set of 38000 Bombyx EST sequenced from the 3’ side, helped annotating the SAGE libraries. Most of the tags appeared at similar relative concentration in the two libraries except for those corresponding to silk proteins that were found region-specific and highly abundant. Strikingly, besides tags from silk protein mRNAs, 19 tags were found in the class of high abundance in the median cell library, which were absent in the posterior cell tag collection. Except tags from SP1 mRNA, no PSG specific tags were found in the same class of abundance. The analysis of MSG-specific different transcripts led to suggest that middle silk gland cell realizes more diversified functions as those already known, of synthesis and secretion of the silk sericins. EST libraries from 11 silkworm tissues were 3’-sequenced to ensure the identification of the most terminal tag. 37,920 sequences were analyzed on ABI 3700 or 3730XL sequencers. Electrophoregrams were processed with KB Basecaller (3730XL traces) or with PHRED (3700 traces) to obtain the .phd files from which were extracted text sequences and their corresponding quality files in Fasta format (Phd2Fasta, Green and Ewing, 1995; 2002). Vector sequences and bad quality regions were removed with an home made software after identification by Lucy (Chou and Holmes, 2001). Chimera were removed by an home made software and retrotransposon sequences were masked by RepeatMasker (http://repeatmasker.org). The cleaned sequences were clusterized with TGICL package (TIGR) and assembled into contigs with CAP3 (Huang and Madan, 1999). Contigs were identified with Blastn and Blastx on GenBank and SwissProt/TREMBL, respectively. Some clusters, splitted by CAP3 procedure, have been regrouped on the basis of Blastx identity. Identitag (Keime et al., 2004) was used to extract all possible tags (forward and reverse) to create a reference database. Moreover, a quality index is attached to each tag depending to the presense of poly-A, polyadenylation signal and its proximity to 3-prime extremity in the original mRNA sequence. This database was supplemented with the tags extracted from public B. mori sequences (GenBank, Silkbase) with the same software. Tags were extracted from MSG and PSG libraries (from 2304 and 3072 sequenced inserts respectively) with the Sagenhaft software (Beissbarth et al., 2004) then identified and compared with Identitag. The assessment of significant differences among the two libraries was performed by using the Z-test used for comparison of SAGE libraries of different size (Kal et al., 1999). For graphic purpose and to avoid division by zero we used a tag value of 1 for tags that were not detected in MSG or PSG libraries. Since the two SAGE libraries showed up different TAG number, we used the Z-test for comparing the two mRNA populations.

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Bombyx mori silk/titania/gold hybrid materials for photocatalytic water splitting: combining renewable raw materials with clean fuels.

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<i>Bombyx mori</i> silk/titania/gold hybrid materials for photocatalytic water splitting: combining renewable raw materials with clean fuels.

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