Amino acid composition and anti‐polyphenol oxidase of peptide fractions from sericin hydrolysate

Sericin hydrolysate (SH), prepared from enzymatic hydrolysis of sericin, was investigated for its antipolyphenol oxidase (PPO) properties. SH decreased PPO activity from both purified mushroom PPO and extracts from apple and eggplant, and retarded browning in fresh‐cut apple and eggplant. SH was a competitive inhibitor using catechol as a substrate. SH exhibited copper ion‐chelating power and reducing power abilities. Fractionation of SH using size exclusion chromatography resulted in four fractions, designated as F1, F2, F3 and F4, with PPO inhibition of 35.75%, 3.89%, 24.52% and 14.75%, respectively. Ser and Asp were major amino acids found in F1. Amino acid sequences in F1, as investigated by LC‐MS/MS using de novo sequencing, contained a high ratio of amino acids with chelating ability. Moreover, amino acids with reducing power ability and with antityrosinase ability were also identified in the sequences.     

Preparation and characterization of amphotericin B-loaded silk fibroin nanoparticles-in situ hydrogel composites for topical ophthalmic application

Journal of Materials Science - The objective of this study was to develop and characterize a novel combined systems of amphotericin B-loaded silk fibroin nanoparticles (AmB-FNPs) and in situ...     

Inhibitory effect of sericin on polyphenol oxidase and its application as edible coating

Sericin, a water‐soluble globular protein derived from silk industry wastewater, was investigated for food industrial applications. The results proved that sericin retarded polyphenol oxidase (PPO) activity. However, the degree of inhibition varied depending on the enzyme origins, the types of substrate, sericin content and sericin molecular size. Using catechol as a substrate, under the conditions studied, sericin lowered purified mushroom PPO and apple extract PPO activity by 40% and mango extract PPO by 75%. Kinetic studies on purified mushroom PPO indicated that the type of inhibition of sericin was dependent on the substrates used. Inhibitory effects of sericin increased as the sericin content increased. The reduction in sericin molecular size by enzymatic hydrolysis produced sericin hydrolysate with ability to decrease PPO activity approximately three times greater than that of sericin. Fresh‐cut Red Delicious apples coated with sericin showed significant reduction in weight loss and improvement in the colour and texture.     

Crosslinked fibroin nanoparticles using EDC or PEI for drug delivery: physicochemical properties,crystallinity and structure

A new silk fibroin-based nanoparticles (FNPs) have been successfully developed utilizing crosslinker EDC (EDC-FNPs) or cationic polymer poly(ethyleneimine) (PEI-FNPs). All developed crosslinked FNPs show a similar spherical particle size of ~?300 nm. Depending on the amount of EDC or the addition of PEI, the zeta potential could be controlled favorably and range from ??15 mV to +?30 mV. Particle structures and crystallinity index are determined and compared using different techniques; X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FT-IR), differential scanning calorimetry and nuclear magnetic resonance (NMR). The most reliable crystallinity calculation methods are based on FT-IR and NMR. The degree of fibroin crystallinity increases with increasing EDC content, whereas PEI reduces it. Exceptionally, XRD shows a reverse order of crystallinity due to the inability to detect short-range ordered structures. Proposed schematic particle structures match all experimental data. In conclusion, the crosslinked fibroin-based nanoparticle properties could be manipulated by using carbodiimide or PEI crosslinkers. In addition, both EDC-FNPs and PEI-FNPs showed high potential as a drug delivery system.