The recombined ricin A chain protein (RTA) was transported into living cells by multiwalled carbon nanotubes (MWNTs) as a cellular carrier, as performed by natural ricin B chain protein (RTB). The conjugate of the toxin protein RTA and MWNT was found to translocate to the cytoplasm of various cell lines and performed biological functions, as evidenced by the induction of cell death. The delivery of RTA into the cells viananotube carriers was directly visualized by transmission electron microscopy (TEM) and confocal microscopy. About three times higher cell death rates for L-929, HL7702, MCF-7, HeLa and COS-7 cells were demonstrated induced by MWNT–RTA conjugates, compared to those achieved by RTA alone. Especially for HeLa cells, the cell mortality reached ∼75%. In addition, obvious selective destruction of cancer cells was achieved by coupling MWNTs–RTA–HER2, which selectively recognize the HER2/neu receptor on certain breast cancer cells. This is the first example of recombined protein toxin (RTA)-induced targeting destruction for tumor cells viacarbon nanotube molecular transporters. The transporting capabilities of carbon nanotubes combined with functional proteins may open exciting new venues for drug delivery and cancer therapy.

Lacticaseibacillus rhamnosus is a generalist that can adapt to different ecological niches, serving as a valuable source of probiotics. The genome of L. rhamnosus X253 contains one chromosome and no plasmids, with a size of 2.99 Mb. Both single-copy orthologous gene-based phylogenetic analysis and average nucleotide identity indicated that dairy-derived L. rhamnosus X253 was most closely related to the human-intestine-derived strain L. rhamnosus LOCK908, rather than other dairy strains. The adaptation of L. rhamnosus X253 and the human-intestine-derived strain L. rhamnosus GG to different ecological niches was explained by structural variation analysis and COG annotation. Hemolytic assays, API ZYM assays, and antimicrobial susceptibility tests were performed to validate risk-related sequences such as virulence factors, toxin-encoding genes, and antibiotic-resistance genes in the genomes of L. rhamnosus X253 and GG. The results showed that L. rhamnosus GG was able to use L-fucose, had a higher tolerance to bile salt, and adhered better to CaCo-2 cells. In contrast, L. rhamnosus X253 was capable of utilizing D-lactose, withstood larger quantities of hydrogen peroxide, and possessed excellent antioxidant properties. This study confirmed the safety and probiotic properties of L. rhamnosus X253 via complete genome and phenotype analysis, suggesting its potential as a probiotic.

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