Preparation and characterization of silk fibroin as a biomaterial with potential for drug delivery.

Hao Zhang,Yu-Zhang Wu,Bing Ni,Wei Zhou,Ling-Ling Li,Fang-Yin Dai,Xia Yang

doi:10.1186/1479-5876-10-117

Abstract

BackgroundDegummed silk fibroin from Bombyx mori (silkworm) has potential carrier capabilities for drug delivery in humans; however, the processing methods have yet to be comparatively analyzed to determine the differential effects on the silk protein properties, including crystalline structure and activity.MethodsIn this study, we treated degummed silk with four kinds of calcium-alcohol solutions, and performed secondary structure measurements and enzyme activity test to distinguish the differences between the regenerated fibroins and degummed silk fibroin.ResultsGel electrophoresis analysis revealed that Ca(NO3)2-methanol, Ca(NO3)2-ethanol, or CaCl2-methanol treatments produced more lower molecular weights of silk fibroin than CaCl2-ethanol. X-ray diffraction and Fourier-transform infrared spectroscopy showed that CaCl2-ethanol produced a crystalline structure with more silk I (α-form, type II β-turn), while the other treatments produced more silk II (β-form, anti-parallel β-pleated sheet). Solid-State 13C cross polarization and magic angle spinning-nuclear magnetic resonance measurements suggested that regenerated fibroins from CaCl2-ethanol were nearly identical to degummed silk fibroin, while the other treatments produced fibroins with significantly different chemical shifts. Finally, enzyme activity test indicated that silk fibroins from CaCl2-ethanol had higher activity when linked to a known chemotherapeutic drug, L-asparaginase, than the fibroins from other treatments.ConclusionsCollectively, these results suggest that the CaCl2-ethanol processing method produces silk fibroin with biomaterial properties that are appropriate for drug delivery.

Highlights

Degummed silk fibroin from Bombyx mori has potential carrier capabilities for drug delivery in humans; the processing methods have yet to be comparatively analyzed to determine the differential effects on the silk protein properties, including crystalline structure and activity
Preparation of degummed silk fibroin Cocoons from B. mori were degummed by incubating in a mixture of sodium dodecyl sulfate (SDS; 0.25%,w/v) and sodium carbonate (0.25%,w/v) at 98°C for 30 min
Morphology of silk fibroins The silk fibroins treated with Ca(NO3)2Á4H2O-methanol, Ca(NO3)2Á4H2O-ethanol, CaCl2-methanol-H2O, and CaCl2ethanol solution were separately dissolved

Summary

Introduction

Degummed silk fibroin from Bombyx mori (silkworm) has potential carrier capabilities for drug delivery in humans; the processing methods have yet to be comparatively analyzed to determine the differential effects on the silk protein properties, including crystalline structure and activity. Silk fibers produced by silkworms are widely used in our daily life. While they have occupied an important niche in the textile industry for thousands of years, their potential as biomaterials has been recognized and developed only over the past decade [1]. Bioconjugations of insulin, glucose oxidase, Lasparaginase (L-ASNase), lipase and phenylalanine ammonia-lyase with the regenerated silk fibroin greatly improved their biological stability, reduced the immunogenicity and toxicity of the drug [7,8,9,10,11]. The SELP (silk-elastinlike protein polymer)-controlled gene delivery approach could potentially improve activity of adenoviral-mediated gene therapy of head and neck cancer and limit viral spread to normal organs at the same time [12]

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Results

Conclusion