Modified silk films containing glycerol

a technology of glycerol and silk fibroin, which is applied in the field of modified silk fibroin films containing glycerol, can solve the problems of low ductility, stiffness and brittleness of silk fibroin films, and high tensile strength of silk fibroin films, and achieve enhanced aqueous solubility and biocompatibility, enhanced biocompatibility and the potential to load bioactive compounds

Inactive Publication Date: 2011-09-15
TRUSTEES OF TUFTS COLLEGE TUFTS UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0005]The present invention provides for films comprising silk fibroin and glycerol, which have distinct properties compared with silk fibroin films lacking glycerol. More specifically, the aqueous solubility and biocompatibility are enhanced with the use or inclusion and use of glycerol as a plasticizer. Processing silk fibroin in water also enhances both biocompatibility and the potential to load bioactive compounds without loss of function, and adds “green chemistry” value to these biomaterials. For example, blends of silk fibroin and glycerol with glycerol concentrations above 30% (w / w) cast into films resulted in the conversion of silk secondary structure from random coil to a-helix, prevented silk from dissolution upon hydration, provided distinct film nanostructure morphology, improved film flexibility in either dry (as-cast film) or wet (after leaching out the glycerol) environments, and preserved cell biocompatibility. Mechanistically, glycerol may replace water in silk fibroin chain hydration, resulting in initial stabilization of helical structures as opposed to random coil or β-sheet structures. The impact of glycerol on stabilizing film structure, aqueous insolubility and function apparently occurs above a glycerol concentration of about 20 wt % glycerol. The use of glycerol in combination with silk fibroin in materials processing expands the functional features attainable with this fibrous protein, and the formation of more flexible films with potential utility in biomaterial and device applications.

Problems solved by technology

Some pure silk fibroin films tend, over time, to become stiff and brittle in the dry state, however, exhibiting impressive tensile strength but low ductility.

Method used

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  • Modified silk films containing glycerol
  • Modified silk films containing glycerol
  • Modified silk films containing glycerol

Examples

Experimental program
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Effect test

example 1

Silk Fibroin Purification

[0065]Silk fibroin aqueous stock solutions were prepared as previously described. Sofia et al., 54 J. Biomed. Mater. Res. 139-48 (2001). Briefly, cocoons of Bombyx mori were boiled for 20 min in an aqueous solution of 0.02 M sodium carbonate, and then rinsed thoroughly with pure water. After drying, the extracted silk fibroin was dissolved in 9.3 M LiBr solution at 60° C. for 4 hr, yielding a 20% (w / v) solution. This solution was dialyzed against distilled water using SLIDE-A-LYZER® Dialysis Cassettes, 3,500 MWCO (Pierce, Rockford, Ill.) for 3 days to remove the salt. The solution was optically clear after dialysis and was centrifuged to remove the small amounts of silk aggregates that formed during the process, usually from environment contaminants that are present on the cocoons. The final concentration of silk fibroin aqueous solution was approximately 6% (w / v). This concentration was determined by weighing the residual solid of a known volume of solution...

example 2

Preparation of Silk / Glycerol Blend Films

[0067]The purified silk fibroin solution was mixed with glycerol at weight ratios of 0%, 5%, 10%, 20%, 30%, 40%, 50% (w / w). The mixed solutions were poured into Petri dishes and dried at room temperature in a laminar flow hood overnight. Unless otherwise stated, the ‘dry blend films’ refers to the films prepared by this direct casting and overnight drying, and the ‘wet blend films’ refers to the same cast and dried films from which the glycerol is subsequently extracted in ultrapure water at 37° C. for 1 hr, after which the films are dried again in the air. For additional variables in the treatment groups, methanol treatments were used, and in these cases the films (with and without glycerol) were immersed in 90% (v / v) methanol for 1 hr and then air-dried.

example 3

Dissolution of silk / glycerol films

[0068]Blend films were cut into approximately 5 mm×5 mm squares, and one square film was weighed and immersed in ultrapure water in a 2 ml tube to a concentration of 1% (weight of film / volume of water), and kept at 37° C. for 1 hr or 1 day. After the incubation, the silk films were removed from the solution, air-dried overnight, weighed, and compared with the mass of original film to obtain residual mass (%). The remaining solution was subjected to UV absorbance measurement at 280 nm. The absorbance values were converted to the amount of silk solubilized in water using purified silk fibroin solution at various concentrations as standards. The amount of dissolved silk was then compared with the total silk mass in the film to obtain the percentage of the film dissolved silk in water.

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Abstract

The present invention provides for compositions and methods for preparing aqueous insoluble, ductile, flexible silk fibroin films. The silk films comprise silk fibroin and about 10% to about 50% (w/w) glycerol, and are prepared by entirely aqueous processes. The ductile silk film may be further treated by extracting the glycerol from and re-drying the silk film. Active agents may be embedded in or deposited on the glycerol modified silk film for a variety of medical applications. The films may be into 3-dimentional structures, or placed on support surfaces as labels or coatings. The glycerol modified silk films of the present invention are useful in variety of applications such as tissue engineering, medical devices or implants, drug delivery, and edible pharmaceutical or food labels.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 61 / 104,135 filed Oct. 9, 2008, the contents of which are incorporated herein by reference in its entirety.GOVERNMENT SUPPORT[0002]This invention was made with government support under grant no. EB002520 awarded by the National Institutes of Health and No. FA9550-07-1-0079 awarded by the Air Force Office of Scientific Research. The U.S. federal government has certain rights in the invention.FIELD OF THE INVENTION[0003]The present invention provides for compositions and methods for preparing silk fibroin films containing glycerol and having improved mechanical properties.BACKGROUND[0004]Silk fibroin has excellent film-forming capabilities and is also compatible for use in the human body. Silk fibroin films, without further manipulation or treatment, are soluble in water because of dominating random coil protein structures. The structural features of ...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): A61K39/395C12N5/071A61K47/42A61K35/12A61K38/02A61K31/7088A61K38/43A61K35/76A61P31/00A61P31/04A61P35/00B29D11/00A23L19/00
CPCA61L27/3604A61L27/3804A61L27/50C08J2389/00C12N11/02C08L89/00C08J3/18C08J5/18C08K5/053A61P31/00A61P31/04A61P35/00A61F2/02A61L27/22A61L27/54A61L2420/06B05D1/30B05D3/0254B05D3/107
Inventor LU, SHENZHOUWANG, XIAOQINOMENETTO, FIORENZOKAPLAN, DAVID
Owner TRUSTEES OF TUFTS COLLEGE TUFTS UNIV
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