We describe the generation of transgenic silkworms that produce cocoons containing recombinant human collagen. A fusion cDNA was constructed encoding a protein that incorporated a human type III procollagen mini-chain with C-propeptide deleted, a fibroin light chain (L-chain), and an enhanced green fluorescent protein (EGFP). This cDNA was ligated downstream of the fibroin L-chain promoter and inserted into a piggyBac vector. Silkworm eggs were injected with the vectors, producing worms displaying EGFP fluorescence in their silk glands. The cocoons emitted EGFP fluorescence, indicating that the promoter and fibroin L-chain cDNAs directed the synthesized products to be secreted into cocoons. The presence of fusion proteins in cocoons was demonstrated by immunoblotting, collagenase-sensitivity tests, and amino acid sequencing. The fusion proteins from cocoons were purified to a single electrophoretic band. This study demonstrates the viability of transgenic silkworms as a tool for producing useful proteins in bulk.

KEY WORDS: Polyester / Bio-based Polymer / Curcumin / Photodegradable Polymer / Polymer Complex / Design of bio-based plastics derived from renewable resources is one of key technologies to attain sustainable development of modern civilization. In order to reduce the dependency on petroleum resources in chemical industry, a great deal of efforts have been paid to utilize a wide variety of bio-resources. These days, bio-based polymers 1 are of particularly strong interest because the use of such material is believed to lead to reduction of carbon dioxide emission.In the present paper, we wish to report synthesis of novel polyesters using curcumin as a monomer. Curcumin [5-hydroxy-1,7-bis(4-hydroxy-3-methoxyphenyl)-1,4,6-heptatrien-3-one] 2 is well known as yellow coloring dye that is naturally abundant in Turmeric plant (Curcuma longa). Turmeric plant is indigenous to tropical Asia such as India and Malaysia. For many centuries, turmeric has been commonly used as spice (curry) in various foods or medicine for diseases such as inflammatory.3 However, in spite of a great deal of concern toward curcumin and common availability of this compound, it is amazing that it has scarcely been utilized as a bioresource for material synthesis. From a standing point of polymer synthesis, curcumin has a symmetrical structure and possesses two hydroxyl groups which are available as polymerizable functional group. Therefore, curcumin can be regarded as an inherent natural monomer which can be readily polymerized by conventional polymerization methods. In the field of polymer synthesis, curcumin has been examined as a photoinitiator for polymerization of styrene and methyl methacrylate. 4 However, there had not been examples of polymer synthesis using curcumin as a monomer itself. Herein, we have prepared novel polyesters bearing -diketone units in their main chain.To begin with, a polycondensation of curcumin (1) with sebacoyl chloride (2a) was examined in chloroform as depicted in Scheme 1. Curcumin was purchased from Tokyo Chemical Industry Co. Ltd. (TCI) and used after recrystallization in 2-propanol. The polymerization was carried out by adding a chloroform solution of sebacoyl chloride to a suspension of an equimolar amount of curcumin in chloroform in the presence of triethylamine at 0 C. Then, the resulting mixture was stirred for 1 h at room temperature. Although curcumin is poorly soluble in chloroform, the reaction mixture gradually became homogeneous during the polymerization. Some insoluble precipitate was formed when molecular weight of the resulting polymer was large. The insoluble part was removed by filteration before further purification. The obtained crude polymer was reprecipitated in n-hexane twice and then obtained polymer was dissolved in chloroform and washed with water three times. After removal of the solvent, yelloworange colored polymer was obtained in good efficiency. The obtained polyester 3a was soluble in common organic solvents such as dichloromethane and chloroform. After casting the chloroform ...

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