PREFERRED EMBODIMENT FOR CARRYING OUT THE INVENTION
The present invention is directed toward synthetically spun silk nanofibers. Silk nanofilbers refere to those silk fibers that have been spun. In other words, these silk fibers are solid phase materials, and should be distinguished from liquid phase or gel state silk. The term synthetically spun refers to those fibers that are produced or spun by means, apparatus, or techniques other than by an animal, i.e., naturally spun fibers. An example of a naturally spun fiber is that produced by a spider.
As the skilled artisan will appreciate, a solid phase fiber is produced by drawing a viscous liquid or gel through a fine orifice. This liquid phase or gel can include native silk, which is an aqueous solution of silk polymer as found within the glands of animals. The liquid or gel can also include regenerated solutions of silk, which are obtained by dissolving naturally spun fibers within a solvent. Additionally, the liquid or gel can include genetically engineered silk-like solutions. An example of a genetically engineered silk-like solution is that disclosed by Prince et al., D. Biochemistry, Vol. 34 (1995), pp. 5 or Lewis et al. in Protein Expression Purification, Vol. 7 (1996), pp. 400-406.
It should be understood that the term silk, in general, refers to those numerous polypeptide high molecular weight polymers that are produced by a large variety of organisms. The term, of course, will also refer to those silk-like polymers that have been genetically engineered. Particularly useful silks include those produced by organisms within the phylum Arthropoda. Preferred Arthropoda include those species that fall within the classes Insecta and Arachnida, even more preferred are the species Bombyx mori and Nephila clavipes. Most preferred are the Nephila clavipes fibers obtained from the major ampullate gland, and the domestic Bombyx mori.
The nanofibers of the present invention have an average diameter of less than about 2, 000 nanometers. Preferably, the average diameter of the fibers is from about 2 to about 2, 000 nanometers, preferably from about 5 to about 1, 000 nanometers, more preferably from about 8 to about 500 nanometers, and even more preferably from about 20 to about 200 nanometers, still more preferably from about 30 to about 120 nanometers, and most preferably from about 40 to about 80 nanometers. The skilled artisan will appreciate that the use of the term average diameter accounts for the fact that one single fiber strand may have a varying diameter across its length, and that the production of numerous fibers can produce fibers of different diameter.
