Probiotics have shown excellent application prospects in preventing and treating many diseases. However, their sensitivity to the harsh environment in vivo always leads to a massive loss of viability and insufficient therapeutic effect. Fortunately, modified probiotics have emerged and provide multiple possibilities for their use in various diseases. Modification not only endows probiotics with extra capacity to resist severe environments but also gives them exogenous characteristics, such as prolonged retention time and improved therapeutic effects. Modified probiotics could combine with other therapies, which has opened up new avenues to enhance the efficacy of probiotic-based therapy. In this review, we have summarized the current physicochemical and biological modification strategies of probiotics. In addition, the progress of research on probiotic-based combination therapy has also been extensively reviewed, which contributes to the enhanced delivery of probiotics or other active constituents and provides new ideas for disease treatment, bioimaging, and diagnosis.

A colon-specific drug delivery system has great potential for the oral administration of colorectal cancer. However, the uncontrollable in vivo fate of liposomes makes their effectiveness for colonic location, and intratumoral accumulation remains unsatisfactory. Here, an oral colon-specific drug delivery system (CBS-CS@Lipo/Oxp/MTZ) was constructed by covalently conjugating Clostridium butyricum spores (CBS) with drugs loaded chitosan (CS)-coated liposomes, where the model chemotherapy drug oxaliplatin (Oxp) and anti-anaerobic bacteria agent metronidazole (MTZ) were loaded. Following oral administration, CBS germinated into Clostridium butyricum (CB) and colonized in the colon. Combined with colonic specifically β-glucosidase responsive degrading of CS, dual colon-specific release of liposomes was achieved. And the accumulation of liposomes at the CRC site furtherly increased by 2.68-fold. Simultaneously, the released liposomes penetrated deep tumor tissue via the permeation enhancement effect of CS to kill localized intratumoral bacteria. Collaborating with blocking the translocation of intestinal pathogenic bacteria from lumen to tumor with the gut microbiota modulation of CB, the intratumoral pathogenic bacteria were eliminated fundamentally, blocking their recruitment to immunosuppressive cells. Furtherly, synchronized with lipopolysaccharide (LPS) released from MTZ-induced dead Fusobacterium nucleatum and the tumor-associated antigens produced by Oxp-caused immunogenic dead cells, they jointly enhanced tumor infiltration of CD8⁺ T cells and reactivated robust antitumor immunity.

Activating humoral and cellular immunity in lymph nodes (LNs) of nanoparticle-based vaccines is critical to controlling tumors. However, how the physical properties of nanovaccine carriers orchestrate antigen capture, lymphatic delivery, antigen presentation and immune response in LNs is largely unclear. Here, we manufactured gold nanoparticles (AuNPs) with the same size but different shapes (cages, rods, and stars), and loaded tumor antigen as nanovaccines to explore their disparate characters on above four areas. Results revealed that star-shaped AuNPs captured and retained more repetitive antigen epitopes. On lymphatic delivery, both rods and star-shaped nanovaccines mainly drain into the LN follicles region while cage-shaped showed stronger paracortex retention. A surprising finding is that the star-shaped nanovaccines elicited potent humoral immunity, which is mediated by CD4⁺ T helper cell and follicle B cell cooperation significantly preventing tumor growth in the prophylactic study. Interestingly, cage-shaped nanovaccines preferentially presented peptide-MHC I complexes to evoke robust CD8⁺ T cell immunity and showed the strongest therapeutic efficacy when combined with the PD-1 checkpoint inhibitor in established tumor study. These results highlight the importance of nanoparticle shape on antigen delivery and presentation for immune response in LNs, and our findings support the notion that different design strategies are required for prophylactic and therapeutic vaccines.