Simple yet efficient detection methods for food allergens are in urgent need to help people avoid the risks imposed by allergenic food. In this work, a polydopamine (PDA)-based fluorescent aptasensor was developed to detect arginine kinase (AK), one of the major allergens in shellfish. The aptamer towards AK was firstly selected via systematic evolution of ligands by exponential enrichment method and labeled with fluorescein amidite (FAM) to build a fluorescence resonance energy transfer (FRET) system with PDA particles. Polyethylene glycol (PEG) was employed to construct an antifouling surface for the aptasensor to eliminate food matrix interferences. With the presence of AK, the PDA-based aptasensor exhibited elevated fluorescent signals as the FAM-labeled aptamer bound to AK and detached from the PDA particles. The aptasensor showed great stability and resistance to nonspecific interference of background proteins and had a limit of detection (LOD) of 0.298 μg/mL. The proposed aptasensor was further proved to be feasible for quantitative analysis of AK in nine species of shrimps and five commercial processed products, which indicated its high potential in tracing the presence of AK in complex aquatic products.

Porphyra polysaccharide is a special kind of nutrient showing multiple physiological functions including regulating cell proliferation, but the detailed mechanisms are not fully revealed, impairing its further development and applications. This work was to purify and characterize the Porphyra haitanensis polysaccharide (PH), investigate its physiological function, and demonstrate the underlying mechanisms. The purified PH was first characterized by Fourier-transform infrared spectroscopy. Then an intestinal epithelial cell model was established, in which PH significantly suppressed cell hyperplasia. Specifically, PH activated the Hippo/YAP pathway, which subsequently activated mTOR pathway, however mTOR activated Hippo in the absence of PH. Moreover, both the inhibition of Hippo by YAP1 knock-down and the suppression of mTOR by rapamycin impaired PH function. These results indicated that PH attenuated hyperplasia activity by remodeling the cross-talk between Hippo/YAP and mTOR pathways, which revealed potential targets and approaches for treating hyperplasia-related diseases and provided novel ways to utilize P. haitanensis as well as other related functional foods.

D-tryptophan is a special kind of nonprotein amino acid showing multiple physiological functions, but the detailed mechanisms are not fully revealed, impairing its further development and applications. This work was to investigate D-tryptophan physiological function and demonstrate the underlying mechanisms. D-tryptophan suppressed HaCaT cell proliferation but increased cell migration. Specifically, D-tryptophan decreased E-cadherin and increased Snail, Twist, and Slug expression, resulting in the development of an epithelial-mesenchymal transitions (EMT) phenomenon. Moreover, D-tryptophan promoted the expression of transforming growth factor-β (TGF-β) 1, and Smad4 knockout damages D-tryptophan's ability. These results indicated that D-tryptophan stimulated HaCaT cells to produce TGF-β1 and thus activated the TGF-β/Samd pathway, resulting in the triggering of EMT. This study revealed the molecular mechanisms of D-tryptophan activity, provided D-tryptophan as a potential approach for cancer treatment, wound healing, organ development and other relevant applications.