Silk Fibroin/Chitosan Blended Microparticles: Preparation, Characterization, and Oil Absorption

In this work, we extracted silk fibroin (SF) via a tertiary solvent system (CaCl₂:Ethanol:H₂O) and then blended it with chitosan (CS) solution to construct microparticles using the water-in-oil-emulsion-diffusion method. For the mixture of SF/CS solution aqueous phase (W) was prepared at ratios of 4:0, 3:1, 1:1, 1:3, and 0:4, using ethyl acetate as the oil phase (O). After the microparticles were prepared, their morphology was examined using scanning electron microscopy (SEM). The optimal preparation conditions were determined to be a 1% (w/v) aqueous phase with a volume of 1 milliliter, 100 milliliters of oil phase, and a stirring speed of 700 rpm. The average microparticle size was 50-100 micrometers. ATR-FTIR spectra showed unique functional groups of SF and CS, as well as interactions between the two polymers. The results of the thermal property study using a TGA instrument showed that SF microparticles had a higher maximum decomposition temperature (T_d,max) than chitosan, and the blended microparticles' T_d,max increased with the proportion of SF. Most microparticles exhibited a semi-crystalline polymer structure, with SF microparticles being the most hydrophobic, followed by blended microparticles and CS, respectively. Testing for absorption capacity, the SF microparticles were more effective at absorbing used engine oil than vegetable oil and chloroform, while CS microparticles showed the highest capacity for vegetable oil. The experimental results indicated that all SF/CS blended particles played an efficiency of absorption variable by ratios of SF or CS blended. This suggested that the prepared microparticles might be useful for oil/water separation application.