Siqi Zhuo,Mingyue Xun,Mingda Li,Xiaoxue Kong,Rui Shao,Tiesong Zheng,Daodong Pan,Jianlin Li,Qianjin Li
S-layer protein (SLP) is a surface protein present in many bacteria and shows unique self-assemble ability for various applications, but its detection methods are very limited. In this paper, a label-free, highly selective and sensitive assay of SLP was developed by using the TiO 2 -coated porous silicon (PSi)-based microfluidic biosensor. The PSi-based biosensor could be easily prepared in a microfluidic device to build a microfluidic biosensing system for measuring SLP in samples rapidly. As the detection principle of the biosensor was based on the light reflection interference, so there was no labeling requirement. The specific recognition capability of the PSi-based biosensor was achieved by the non-covalently immobilized anti-SLP on the PSi surface. The developed biosensing system showed a rapid response time (5 min) and an excellent specificity to SLP, and displayed a broad detection linear range of 0.001 ∼ 10 μg/mL and a low detection limit of 3.2 ± 1.7 × 10 −5 μg/mL (0.70 ± 0.37 pM). The microfluidic biosensor can also be used for determination of the apparent dissociation constant ( K d ) between SLP and anti-SLP, which was measured to be 4.8 ± 0.9 × 10 -9 M.
Scope Lactobacillus casei F0822-fermented milk has exhibited significant hypocholesterolemic activity in hamsters in the previous study. Under this premise, the objective of this study is to further explore whether bile salt hydrolase (BSH) and S-layer protein (SLP) of the strain have a significant influence on hypocholesterolemic activity of the fermented milk. Methods and results Independent and double interposon mutants of BSH and SLP genes are constructed from wild-type L. casei F0822 via chromosomal insertion of chloramphenicol or/and erythromycin resistance genes based on double-crossover homologous recombination. The mutants- and the wild-type strain-fermented milk is prepared (viable counts of approximately 8.0 × 10 8 colony-forming units mL –1 each) and intragastrically administered to high-cholesterol-fed hamsters once daily at a dose of 1.25 mL d –1 for 28 d, respectively. Both the BSH-deficient mutant- and the SLP-deficient mutant-fermented milk significantly ( p < 0.05) increase serum total and LDL-cholesterol levels in hamsters compared with the wild-type strain-fermented milk. However, only the BSH-deficient mutant-fermented milk could significantly ( p < 0.05) increase hepatic total and esterified cholesterol levels in hamsters. Conclusion Both BSH and SLP have a significant influence on the hypocholesterolemic activity of L. casei F0822-fermented milk in hamsters. Nevertheless, the BSH is greater than the SLP in this regard.
S-layer proteins (Slps) are crystalline arrays of protein on bacterial cell surface layers. Owning to their capability to reassemble on the surface of lipid layers, Slps have been employed to modify liposomes for various profits. But the interaction information between Slps and positively charged liposomes are destitute, especially the gastrointestinal adhesion of Slps-coating liposomes is rarely reported. In the present work, the Slps extracted from Lactobacillus helveticus were reassembled on the surface of novel positively charged liposomes composed of soybean lecithin , Eudragit ® RL100 and cholesterol. The particle size and remarkable changes of Zeta potential with various Slps/lipid weight ratios were determined by dynamic light scattering and phase analysis light scattering. Significant difference in fluorescence dequenching percentage of liposomes decorated by ODA-FITC confirmed Slps self-reassemble on the surface of liposomes. A higher integrity of vesicular membrane after the addition of Triton X-100 solution demonstrated the stability enhancement of Slps-coating liposomes. Fourier transform infrared (FTIR) spectroscopy illustrated the interaction came from non-covalent bond. The mucoadhesion of Slps-coating liposomes was evaluated by the resident FITC-LP on the gastric and intestinal tract of mice at 7 h and 12 h after intragastrical administration, which proved that the Slps-coating improved the gastrointestinal adhesion significantly.
Pan Daodong,Xun Mingyue,Lan Hangzhen,Li Jianlin,Wu Zhen,Guo Yuxing
A newly developed molecularly imprinted photonic polymer (MIPP) film, which was prepared by colloidal crystal templating and surface molecular imprinting, was used for selective capture of S-layer protein (SLP) from a complex Lactobacillus acidophilus sample. The colloidal crystal templates were formed by a dipping process followed by chemical binding of the imprinted template SLP molecules. A sandwich structure consisting of two glass slides was formed after the SLP–silica layer had been covered with a poly(methyl methacrylate) glass slide. After polymerization of the SLP–silica layer with the preprepared polymerization solution, hydrofluoric acid and acetic phosphate buffer solutions removed the silica particles and SLP molecules, respectively. The MIPP film obtained exhibited a three-dimensional, highly ordered and interconnected macroporous structure (pore size greater than 200 nm), which is specifically accessible to SLP molecules. The adsorbed SLP molecules were simply and straightforwardly detected by a fiber-optic spectrometer. The redshift of the Bragg diffraction peak of the MIPP film was linearly related to the number of SLP molecules that had been harvested in the film. The detection limit of the SLP–MMIP–fiber-optic spectrometer method for SLP was 1 ng mL -1 . The MIPP sensor was successfully applied to detect SLP molecules in a crudely extracted Lactobacillus acidophilus sample. Our results prove the applicability of the SLP–MIPP film for fast and real-time measurement of SLP.
Graphical abstract
危险品化学品经营许可证（带存储）