| Summary: | 碩士 === 臺北醫學大學 === 生醫材料暨工程研究所 === 97 === The objective of this study is to produce electrospun regenerated silk fibroin (R-SF) membrane for enzyme immobilization and to explore the feasibility of its dental applications as a tooth whitening strip. The SF harvested from degummed cocoons of silkworm was dissolved in (CaCl2:C2H5OH:H2O) solvent. The shear viscosity of SF solution was measured by rotational rheometer. The processing window of R-SF was constructed with shear-induced method and titration test. The R-SF precipitation could be produced by shear-induced method without dialysis. The inherent viscosity, morphology, and crystal structure of R-SF were analyzed by capillary viscometer, scanning electron microscope (SEM), and X-ray diffractiometer. The R-SF was dissolved in formic acid to prepare the spinning dopes. The extensional viscosity of R-SF/formic acid was analyzed by Wilhelmy type of surface tensiometer and capillary breakup extensional rheometer (CaBER®). Non-woven membranes were then produced via electrospinning. The morphology, wettability, surface energy, and secondary structure of methanol treated R-SF membranes were respectively examined by SEM, contact angle measurement, and FTIR-ATR. Finally, the potatoes extract antioxidant (PEA) was immobilized on electrospun R-SF membranes via freeze drying. The tooth whitening strips were prepared by adding 5.25 wt% hydrogen peroxide onto PEA immobilized R-SF membranes and examined whitening efficacy by colorimeter. R-SF was produced by shear-induced precipitation method (6~8k rpm, 35 ℃) when percentage of SF was below 1 wt%. With this new method, the average yield (87.7±3.51 %) was higher than that of dialysis one (70.8±4.72 %). The crystal structures were different between the new method and dialysis. Besides, extensional viscosity of R-SF/formic acid was depended on solution concentration. The characteristic of solution showed shear thinning in the concentration range of 4~7 wt%, however it transformed to shear thickening at higher concentration range of 8~9 wt%. Within this shear thickening range, the uniform fibers were obtained by electrospinning. The 10 wt% R-SF spinning solution was chosen for experiment hereafter. The average diameter of electrospun fibers was 0.71±0.06 ?慆. After treated by methanol, the contact angle of electrospun R-SF membranes decreased from 110.1±1.52 to 60.1±0.25 degrees. The structure transformation from random coil to ??-pleated crystal of SF was expressed by crystallinity index, ratio of A1628 cm-1/A1665 cm-1, increasing from 0.7 to 2.86. After the treatment of fresh whitening strips, the stained teeth showed a significant color difference (?媧*) value of 61. But it decreased down to 8 after the whitening strip aged for 2 weeks. A new shear-induced precipitation method for R-SF production is developed with advantage of high productivity. Besides, the relationship between electrospinnability of R-SF/formic acid and solution characteristic about extensional rheology is established. This phenomenon is worth further exploration. Membranes prepare from shear-induced R-SF show superior water-resistance and hydrophilicity than those from dialyzed one. The concept for a novel tooth whitening system containing hydrogen peroxide/PEA/electrospun R-SF membrane is effective for tooth whitening evidently.
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