High quality water-soluble photoluminescent (PL) microspheres consisting of CdSe/ZnS quantum dots (QDs) and amphiphilic oligomers (polymaleic acid n-hexadecanol ester) were prepared by a versatile phase transfer method in an emulsion system. Controlled synthesis of different sizes of PL microspheres can be conducted by simply changing the initial oligomer concentration and/or the water/chloroform volume ratio. When the oligomer/QDs molar ratio exceeded 200 : 1, only oligomer-coated monodisperse CdSe/ZnS QDs without any aggregation were obtained. If the molar ratio ranged from 20 : 1 to 120 : 1, size-tunable PL microspheres could be obtained with a size range from 151 to 50 nm. Both of them exhibited high stability in aqueous solution under a wide range of pH, different salt concentrations, and thermal treatment at 100 °C. FTIR spectroscopy, transmission electron microscopy, dynamic light scattering, and fluorescence microscopy were used to characterize the PL microspheres and oligomer-coated monodisperse QDs. It is demonstrated that the stability of PL microspheres indeed depended on their dimensions. Larger PL microspheres could provide more hydrophobic protection for their interior QDs than smaller PL microspheres. A biosensor system (lateral flow immunoassay system, LFIA) for the detection of human chorionic gonadotrophin (HCG) antigen was developed by using CdSe/ZnS PL microspheres as fluorescence labels and a nitrocellulose filter membrane for lateral flow. The result showed that the PL microspheres were excellent fluorescence labels to detect HCG antigen in this LFIA system. The sensitivity of HCG antigen detection can reach 0.5 IU L⁻¹, which is almost 20 times higher than traditional LFIAs using tinctorial labels.

Ulcerative colitis (UC) is a chronic inflammatory bowel disease characterized by recurrent gastrointestinal inflammation caused by abnormal immune response, and patients usually have intestinal flora imbalance. At present, the pathogenesis of UC is not well understood, and it appears that there is chronic activation of the immune and inflammatory cascade in genetically susceptible individuals. Some food supplements such as specific peptides and probiotics have been investigated and shown the potential for the treatment of UC. The purpose of this study is to investigate the therapeutic effect and potential mechanism of tetrapeptide from maize (TPM) and probiotic treatment on dextran sulfate sodium (DSS)-induced UC in C57BL/6J mice. Our results indicated that the therapeutic effects of TPM and probiotics are positively associated with a reduction in pro-inflammatory cytokine levels and restoration of the gut microbiota. Treatment with TPM or probiotics effectively alleviated the adverse effects of UC, including weight loss, shortened colon length, and colon and kidney tissue damage in mice. Additionally, both TPM and probiotics significantly reduced pro-inflammatory cytokine levels and oxidative stress in UC mice, and the effect was more pronounced when both were used together. Moreover, co-treatment with TPM and probiotics increased the diversity of gut microbes in UC mice, reduced the ratio of Firmicutes to Bacteroidetes (F/B) and increased the abundance of bacterial species, including Muribaculaceae, Alistipes, Ligilactobacillus and Lactobacillus, and has been shown to be beneficial for a variety of pathological conditions.

In this study, we successfully prepared a selenium-containing pentapeptide (Sec-Arg-Gly-Asp-Cys)-modified gold nanozyme that exhibited glutathione peroxidase (GPx) activity. The nanozyme catalyzed the reduction of H₂O₂ by GSH, and its GPx activity was about 14 times that of free selenopeptide. Kinetic analysis indicated that the nanozyme changed the catalytic mechanism from the ping-pong mechanism of the peptide to an ordered mechanism. This indicated that the gold nanoparticle acts as a scaffold that may limit the mobility and constrain the conformation of the peptides, hence exposing the active center to the substrates, and allowing the multivalent selenopeptide to act cooperatively to increase the catalytic rate. Furthermore, upon addition of cysteamine to regulate the surface chemistry of gold nanoparticles and thereby modify the microenvironment of the active center, this nanozyme system could achieve a tunable GPx activity that was about 20 times that of free selenopeptide. Thus, the rational design of the nanozyme greatly improved and amplified the catalytic activity of the ‘active unit’ peptide. This study provides an alternative strategy to establish GPx mimics and provides new insights for the use of gold nanoparticles to develop nanozymes with biological applications.

Recent studies have indicated that protein hydrolysates have broad biological effects. In the current study we describe a novel antioxidative peptide, FDPAL, from soybean protein isolate (SPI). The aim of this study was to purify and characterize an antioxidative peptide from SPI and determine its antioxidative mechanism. LC–MS/MS was used to isolate and identify the peptide from SPI. The sequence of the peptide was determined to be Phe-Asp-Pro-Ala-Leu (FDPAL, 561 Da). FDPAL can cause significant enhancement of resistance to oxidative stress both in cells as well as simple organisms. In Caenorhabditis elegans (C. elegans), FDPAL can up-regulate the expression of certain genes associated with resistance. The antioxidant activity of this peptide can be attributed to the presence of a specific amino acid sequence. Results from our work suggest that FDPAL can facilitate potential applications of proteins carrying this sequence in the nutraceutical, bioactive material and clinical medicine areas, as well as in cosmetics and health care products.