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Host mucosal barriers possess an arsenal of defense molecules to maintain host-microbe homeostasis such as antimicrobial peptides and immunoglobulins. In addition to these well-established defense molecules, we recently reported small RNAs (sRNAs)-mediated interactions between human oral keratinocytes and Fusobacterium nucleatum (Fn), an oral pathobiont with increasing implications in extra-oral diseases. Specifically, upon Fn infection, oral keratinocytes released Fn-targeting tRNA-derived sRNAs (tsRNAs), an emerging class of noncoding sRNAs with gene regulatory functions. To explore potential antimicrobial activities of tsRNAs, we chemically modify the nucleotides of the Fn-targeting tsRNAs and demonstrate that the resultant tsRNA derivatives, termed MOD-tsRNAs, exhibit growth inhibitory effect against various Fn type strains and clinical tumor isolates without any delivery vehicle in the nanomolar concentration range. In contrast, the same MOD-tsRNAs do not inhibit other representative oral bacteria. Further mechanistic studies uncover the ribosome-targeting functions of MOD-tsRNAs in inhibiting Fn. Taken together, our work provides an engineering approach to targeting pathobionts through co-opting host-derived extracellular tsRNAs.

Advanced staged high‐grade serous ovarian cancer (HGSOC) is the leading cause of gynecological cancer death in the developed world, with 5‐year survival rates of only 25–30% due to late‐stage diagnosis and the shortcomings of platinum‐based therapies. A Phase I clinical trial of a combination of free cisplatin and poly(ADP‐ribose) polymerase inhibitors (PARPis) showed therapeutic benefit for HGSOC. In this study, we address the challenge of resistance to platinum‐based therapy by developing a targeted delivery approach. Novel electrostatic layer‐by‐layer (LbL) liposomal nanoparticles (NPs) with a terminal hyaluronic acid layer that facilitates CD44 receptor targeting are designed for selective targeting of HGSOC cells; the liposomes can be formulated to contain both cisplatin and the PARPi drug within the liposomal core and bilayer. The therapeutic effectiveness of LbL NP‐encapsulated cisplatin and PARPi alone and in combination was compared with the corresponding free drugs in luciferase and CD44‐expressing OVCAR8 orthotopic xenografts in female nude mice. The NPs exhibited prolonged blood circulation half‐life, mechanistic staged drug release and targeted codelivery of the therapeutic agents to HGSOC cells. Moreover, compared to the free drugs, the NPs resulted in significantly reduced tumor metastasis, extended survival, and moderated systemic toxicity.