Detection of white spot syndrome virus in seafood samples using a magnetosome-based impedimetric biosensor.

White spot syndrome virus (WSSV) is a significant threat to the aquaculture sector, causing mortality among crabs and shrimps. Currently available diagnostic tests for WSSV are not rapid or cost-effective, and a new detection method is therefore needed. This study demonstrates the development of a biosensor by functionalization of magnetosomes with VP28-specific antibodies to detect WSSV in seafood. The magnetosomes (1 and 2 mg/ml) were conjugated with VP28 antibody (0.025-10 ng/µl), as confirmed by spectroscopy. The magnetosome-antibody conjugate was used to detect the VP28 antigen. The binding of antigen to the magnetosome-antibody complex resulted in a change in absorbance. The magnetosome-antibody-antigen complex was then concentrated and brought near a screen-printed carbon electrode by applying an external magnetic field, and the antigen concentration was determined using impedance measurements. The VP28 antigen (0.025 ng/µl) bound more efficiently to the magnetosome-VP28 antibody complex (0.025 ng/µl) than to the VP28 antibody (0.1 ng/µl) alone. The same assay was repeated to detect the VP28 antigen (0.01 ng/µl) in WSSV-infected seafood samples using the magnetosome-VP28 antibody complex (0.025 ng/µl). The WSSV in the seafood sample was also drawn toward the electrode due to the action of magnetosomes controlled by the external magnetic field and detected using impedance measurement. The presence of WSSV in seafood samples was verified by Western blot and RT-PCR. Cross-reactivity assays with other viruses confirmed the specificity of the magnetosome-based biosensor. The results indicate that the use of the magnetosome-based biosensor is a sensitive, specific, and rapid way to detect WSSV in seafood samples.

Biomimetic Magnetosomes as Versatile Artificial Antigen-Presenting Cells to Potentiate T-Cell-Based Anticancer Therapy.

Adoptive T-cell transfer for cancer therapy relies on both effective ex vivo T-cell expansion and in vivo targeting performance. One promising but challenging method for accomplishing this purpose is to construct multifunctional artificial antigen-presenting cells (aAPCs). We herein developed biomimetic magnetosomes as versatile aAPCs, wherein magnetic nanoclusters were coated with azide-engineered leucocyte membranes and then decorated with T-cell stimuli through copper-free click chemistry. These nano aAPCs not only exhibited high performance for antigen-specific cytotoxic T-cell (CTL) expansion and stimulation but also visually and effectively guided reinfused CTLs to tumor tissues through magnetic resonance imaging and magnetic control. The persisting T cells were able to delay tumor growth in a murine lymphoma model, while the systemic toxicity was not notable. These results together demonstrated the excellent potential of this "one-but-all" aAPC platform for T-cell-based anticancer immunotherapy.

Biomimetic Immuno-Magnetosomes for High-Performance Enrichment of Circulating Tumor Cells.

A novel biomimetic immuno-magnetosome (IMS) is developed by coating a leukocyte membrane (decorated with anti-epithelial cell-adhesion molecule antibody) on a magnetic nanocluster. In addition to the good stability and magnetic controllability, the IMS also exhibits satisfactory binding avidity to circulating tumor cells but stealth property to leukocytes. As a result, rare tumor cells can be effectively enriched with undetectable leukocyte background.

[Influence of native bacterial magnetic particles on mouse immune response].

OBJECTIVE: To study the influence of native bacterial magnetic particles on mouse immune response. METHODS: Ovalbumin was used as an antigen, mixed with complete Freund's adjuvant, bacterial magnetic particles (BMP) and phosphate buffer solution, to immunize BALB/C mouse. After 14 days later, we detected the titers of the antiovalbumin (IgG) and subtype (IgG1, IgG2a) , the proliferation ability of T lymphocyte, and the expression of IL-2, IL4, IL-10 and IFN-gamma. RESULTS: Compared to the negative control group, the BMP group had the similar level in the titer of specific antibody, the proliferation ability of T lymphocyte and the expression of cytokines (IL-2, IL-4, IL-10 and IFN-gamma). CONCLUSION: Native BMPs has no significantly influence on mouse immune response.

Biocompatibility of bacterial magnetosomes: acute toxicity, immunotoxicity and cytotoxicity.

In this study, we examined the acute toxicity, immunotoxicity, and cytotoxicity of bacterial magnetosomes (BMs). LD(50) of BMs injected into the sublingual vein of SD rats was 62.7 mg/kg. Further studies with injection of 40 mg/kg BMs showed no significant difference between BM-treated and control rats in terms of routine blood exam results, liver and kidney function tests, organ coefficients of major organs, or Stimulation Index (SI) of lymph cells with ConA and/or LPS antigens. Histological examination of major organs from 40 mg/kg BM-treated rats showed no obvious pathological changes except for increased number of vacuoles in livers, and somewhat thicker interlobular septa in lungs. BMs showed little cytotoxic effect on H22, HL60, or EMT-6 cells. Growth of all three cells was neither inhibited nor stimulated by incubation with 9 microg/ml BMs, which also had no effect on DNA content, cell size, or cell membrane integrity.