The rapid proliferation of MDRB has escalated into a critical global health emergency, with the World Health Organization categorizing antimicrobial resistance as a top-tier threat [1], [2]. Traditional antibiotics are increasingly failing, resulting in hundreds of thousands of deaths annually and projections of over 10 million by 2050 [3]. This urgent scenario demands the development of alternative, non-antibiotic therapeutic strategies capable of overcoming bacterial resistance mechanisms.

Among emerging alternatives, PTT and gasotransmitter-based therapies, particularly NO, have shown significant promise. PTT utilizes photothermal agents to convert NIR light into localized heat, physically disrupting bacterial membranes with spatiotemporal precision and minimal off-target effects [3], [4]. NO, an endogenous signaling molecule, exerts potent antimicrobial action through multiple pathways: it induces lipid peroxidation to compromise membrane integrity and generates reactive nitrogen species (RNS) that cause oxidative stress and metabolic disruption within bacterial cells [5]. Combining these two modalities offers a synergistic approach—where PTT-induced hyperthermia can enhance membrane permeability and potentiate NO delivery—thereby improving antibacterial efficacy while reducing the risk of resistance development.

Nanomaterial-based carriers are ideal for integrating such multimodal therapies. Polydopamine, in particular, has gained attention due to its excellent biocompatibility, strong NIR absorption, and versatile surface chemistry [6]. Recent studies highlight the versatility of PDA nanostructures as a new generation of smart theranostic tools, capable of photothermal conversion, drug delivery, and imaging, while offering high biocompatibility and biodegradability [7]. Moreover, functionalized nanoparticles based on natural polymers such as chitosan and gelatin have demonstrated significant potential in active food packaging, where they enhance mechanical strength, barrier properties, and antimicrobial activity, extending the shelf life of perishable foods such as seafood [8]. This underscores the broader applicability of nanoparticle-enhanced composite materials in both biomedical and packaging fields. However, most existing PDA-based NO delivery systems rely on multi-step synthetic routes, such as preparing mesoporous PDA (mPDA) followed by post-synthesis loading of NO donors like BNN6 [9], [10], [11], [12]. These approaches are often labor-intensive, suffer from low drug-loading efficiency, and are prone to premature drug leakage, which severely limits their translational potential as reliable drug delivery systems.

To overcome these limitations, we developed a streamlined one-step in situ co-assembly strategy for fabricating NIR-responsive polydopamine nanoparticles co-loaded with the NO prodrug BNN6 (PDA NP-BNN6). This approach simultaneously encapsulates BNN6 during the polymerization of dopamine, eliminating the need for separate template removal or post-loading steps. In this study, we systematically characterized the nanoparticles, optimized their photothermal and NO release properties, and evaluated their synergistic antibacterial performance against both Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria. Furthermore, we assessed their hemocompatibility and colloidal stability to support potential biomedical application. This work presents a simplified yet effective nanoplatform that combines controlled NO release with potent photothermal activity, offering a promising strategy for combating MDRB infections through localized, non-antibiotic therapy.