<p>Treating urinary tract infections (UTIs) effectively is a difficult task due to the emergence of antibiotic-resistant bacteria and limited antibiotic access to intracellular bacteria within the bladder lining. Numerous studies of the antibiotics-nanodiamonds (NDs) synthesis and their inhibitory effect on bacteria have been performed previously. However, their effectiveness and toxicity in cell-based and animal infection models remain unclear. In this study, we presented the utilization of biopolymer-coated nanodiamonds for the delivery of tetracycline (TET) to the intracellular bacterial communities within the bladder cells using an intravesical delivery approach, aiming to effectively treat UTIs. Compared with antibiotics alone, the TET-loaded ND-based carrier system significantly improved the clearance of intracellular bacteria in the infected cell and animal models. Moreover, the intravesical delivery avoids the potential toxic effects from NDs accumulation in the organs, and minimizes the loss of the drugs during delivery. These results offer a promising strategy to treat chronic infections and prevent the recurrence of urinary tract infections (rUTIs).</p> Graphical Abstract <p></p>