The emergence and dissemination of AMR have become a global public health crisis and pose a profound challenge to modern medicine [1]. Since Alexander Fleming’s discovery of the antibacterial activity of penicillin in 1928, antibiotics have been widely employed in antimicrobial therapy. However, the widespread and often indiscriminate use of antibiotics has exerted intense selective pressure on microbial populations, driving the rapid emergence and spread of multidrug-resistant (MDR) strains [2]. Traditionally, antibiotics exert their effects by targeting essential bacterial processes, including protein biosynthesis, DNA replication and repair, and cell cycle progression, thereby selectively inhibiting or eliminating bacterial pathogens [3]. Building upon this, persistent antibiotic exposure has fueled the evolution of diverse resistance mechanisms, including enzymatic antibiotic degradation (e.g., β-lactamases), overexpression of efflux pumps that expel antibiotics, structural modifications of antibiotic targets (e.g., ribosomal mutations), and regulatory adaptations that upregulate resistance gene expression. Furthermore, the formation of biofilms—complex multicellular communities embedded within a self-produced extracellular polymeric substance (EPS)—plays a crucial role in the persistence of infections and the amplification of antibiotic resistance. The EPS matrix serves as a protective barrier, impeding antibiotic penetration, shielding bacteria from the host immune system, and enhancing their stress tolerance [4]. Indeed, biofilm formation not only complicates treatment strategies but also markedly contributes to the persistence of MDR infections [5], conferring up to a 1,000-fold increase in antibiotic tolerance [6]. Accordingly, there is an urgent need for innovative, non-antibiotic antimicrobial strategies that can effectively target both MDR bacteria and biofilms.
The escalating limitations of conventional antibiotic therapies due to the rise of AMR have catalyzed the exploration of alternative therapeutic modalities. Among these, GT has emerged as a promising non-antibiotic approach for combating bacterial infections and biofilms. Unlike traditional antibiotics, which typically target specific bacterial processes prone to the development of resistance, GSMs exert distinct and multifaceted antimicrobial mechanisms. These GSMs can damage bacterial membranes [7], [8], [9], inhibit bacterial respiration [10], [11], induce oxidative, nitrosative, or reactive sulfur species-mediated stress [12], [13], [14], disrupt metabolic pathways [15], interfere with DNA replication and repair [7], modulate bacterial signaling and quorum sensing (QS), and impair biofilm formation [16], [17], [18], [19]. In addition, they promote wound healing by enhancing angiogenesis, modulating inflammation, and stimulating tissue regeneration [20], [21], [22], thereby addressing multiple aspects of bacterial pathogenesis. Furthermore, their small molecular size and high diffusivity enable effective penetration of bacterial membranes and the dense EPS matrix of biofilms [23]. Importantly, these mechanisms of action fundamentally differ from those of antibiotics, significantly reducing the likelihood of resistance development [24], [25]. Collectively, these properties highlight GT’s potential as a next-generation antimicrobial strategy.
Preclinical studies have demonstrated the efficacy of GT against MDR pathogens in various animal infection models, underscoring its potential for clinical translation. However, despite these promising results, several critical challenges must be addressed before GT can achieve widespread clinical application [20], [26]. GSMs’ small size and high diffusivity present substantial obstacles to achieving targeted delivery and sufficient therapeutic accumulation at infection sites. Systemic administration often leads to non-specific biodistribution, limiting therapeutic efficacy and increasing the risk of off-target effects, including potential toxicity [27]. Moreover, monotherapy based on a single GSM often demonstrates limited antibacterial efficacy and may carry risks associated with gas overdose or toxicity [8], [28]. Another major hurdle lies in the stringent dose-dependent biological effects of GSMs. Their therapeutic window is often narrow, with effective concentrations closely approaching toxic thresholds. For instance, NO exhibits concentration-dependent biphasic effects—promoting vasodilation at low concentrations (<1 μM) while inducing cytotoxicity at higher levels (>1 μM). This nonlinear dose-response relationship complicates precise dosing, as minor variations in GSM delivery can shift outcomes from therapeutic benefit to adverse effects.
To address these limitations, considerable research efforts are now directed toward developing advanced delivery systems that enable controlled, targeted release of GSMs [29]. These systems often utilize nanoscale vectors with tunable sizes and tailored physicochemical properties, which facilitate site-specific delivery via active or passive targeting mechanisms [30]. In particular, stimulus-responsive gas delivery nanoplatforms have attracted significant attention. These systems exploit endogenous stimuli (e.g., hydrogen peroxide (H2O2), glutathione (GSH), glucose, acidic microenvironments, or specific enzymes) or exogenous stimuli (e.g., light, ultrasound (US), heat, or magnetic fields) to trigger precise gas release [31], [32], [33]. Leveraging the progress in stimulus-responsive delivery, researchers have developed combination strategies that integrate GT with other treatment modalities such as PDT [34], PTT [35], CDT [36], and SDT [37]. These multimodal approaches expand the therapeutic landscape of GT-based interventions, offering synergistic effects that enhance bacterial eradication, disrupt biofilms, and modulate immune responses. Fig. 1 schematically illustrates the antibacterial mechanisms of four GSMs and their integration with multimodal therapies, highlighting their diverse roles in bacterial clearance, biofilm disruption, and immunomodulation.
This review provides a comprehensive analysis of GT and its synergistic applications in combating MDR bacteria and biofilms. It begins by elucidating the fundamental mechanisms underlying the antimicrobial and anti-biofilm activities of each GSM, thereby establishing a mechanistic framework to contextualize their biological effects. Advances in gas delivery systems, including cutting-edge technologies, are thoroughly explored, with particular emphasis on design principles, functional properties, and targeted delivery capabilities. The therapeutic potential of GT is evaluated both as a standalone modality and in combination with complementary treatment strategies such as PDT, PTT, SDT, and CDT. These multimodal approaches are highlighted for their ability to address the limitations of conventional GT treatments, offering improved targeting, precision, and efficacy against bacterial infections and biofilms. In addition, the review highlights key challenges that currently hinder the clinical translation of GT, including issues related to delivery efficiency, safety, and regulatory approval. By providing a comprehensive synthesis of recent progress and outlining future research directions, this review bridges the fields of microbiology, nanomedicine, and materials science, offering valuable insights to guide the development of safer, more effective nano-antibacterial platforms for overcoming AMR.