Precision Dosing of Antibiotics and Potentiators by Hypoxia-Responsive Nanoparticles for Overcoming Antibiotic Resistance in Gram-Negative Bacteria

pH-Responsive Protein-Polycation Nanocarriers for Efficient Eradication of Bacterial Biofilms and Intracellular Bacteria

Bacterial biofilms and intracellular pathogens pose significant challenges in eradication, often leading to persistent infections that are difficult to treat. To address this issue, the hydrophobic biofilm dispersant D-tyrosine is encapsulated within protein-polycation nanoparticles, designed using a mannose-terminated cationic polymer and concanavalin through electrostatic interactions. Thermodynamic studies reveal that free mannosyl groups on the nanoparticle surface promote spontaneous binding to receptor molecules mimicking those on bacterial biofilms and host cells. Under mildly acidic conditions, the nanoparticles reduce in size from 550 to ≈48 nm within 2 h, releasing 76% of encapsulated D-tyrosine. The combination of mannose targeting, particle size reduction, and controlled D-tyrosine release enable the nanoparticles to eliminate 70%-80% of the Pseudomonas aeruginosa and Staphylococcus aureus biofilm biomass at minimum bactericidal concentration (MBC) and 2MBC while eradicating 8 log of bacteria embedded within the biofilm. In an intracellular Pseudomonas aeruginosa infection model using RAW 264.7 macrophages, the nanoparticles at 2MBC eliminate over 95% of the intracellular bacteria without inducing an increase in the inflammatory cytokine interleukin-6. These protein-polycation nanoparticles, which activate their antimicrobial properties under acidic conditions, efficiently penetrate bacterial biofilms and host cell barriers via their mannose-rich surface, offering a promising strategy for the treatment of persistent infections.

Nitazoxanide synergizes polymyxin B against Escherichia coli by depleting cellular energy

The rapid expansion of antibiotic-resistant bacterial diseases is a global burden on public health. It makes sense to repurpose and reposition already-approved medications for use as supplementary agents in synergistic combinations with existing antibiotics. Here, we demonstrate that the anthelmintic drug nitazoxanide (NTZ) synergistically enhances the effectiveness of the lipopeptide antibiotic polymyxin B in inhibiting gram-negative bacteria, including those resistant to polymyxin B. Mechanistic investigations revealed that nitazoxanide inhibited calcium influx and cell membrane depolarization, enhanced the affinity between polymyxin B and the extracellular membrane, and promoted intracellular ATP depletion and an increase in reactive oxygen species (ROS), thus enhancing the penetration and disruption of the Escherichia coli cell membrane by polymyxin B. The transcriptomic analysis revealed that the combination resulted in energy depletion by inhibiting both aerobic and anaerobic respiration patterns in bacterial cells. The increased bactericidal effect of polymyxin B on the E. coli ∆nuoC strain further indicates that NuoC could be a promising target for nitazoxanide. Furthermore, the combination of nitazoxanide and polymyxin B showed promising therapeutic effects in a mouse infection model infected with E. coli. Taken together, these results demonstrate the potential of nitazoxanide as a novel adjuvant to polymyxin B, to overcome antibiotic resistance and improve therapeutic outcomes in refractory infections.IMPORTANCEThe rapid spread of antibiotic-resistant bacteria poses a serious threat to public health. The search for potential compounds that can increase the antibacterial activity of existing antibiotics is a promising strategy for addressing this issue. Here, the synergistic activity of the FDA-approved agent nitazoxanide (NTZ) combined with polymyxin B was investigated in vitro using checkerboard assays and time-kill curves. The synergistic mechanisms of the combination of nitazoxanide and polymyxin B were explored by fluorescent dye, transmission electron microscopy (TEM), and transcriptomic analysis. The synergistic efficacy was evaluated in vivo by the Escherichia coli and mouse sepsis models. These results suggested that nitazoxanide, as a promising antibiotic adjuvant, can effectively enhance polymyxin B activity, providing a potential strategy for treating multidrug-resistant bacteria.

A universal strategy to enhance photothermal conversion efficiency by regulating the molecular aggregation states for safe photothermal therapy of bacterial infections

Photothermal therapy (PTT) has emerged as a promising approach for treating bacterial infections. However, achieving a high photothermal conversion efficiency (PCE) of photothermal agents (PTAs) remains a challenge. Such a problem is usually compensated by the use of a high-intensity laser, which inevitably causes tissue damage. Here, we present a universal strategy to enhance PCE by regulating the molecular aggregation states of PTAs within thermoresponsive nanogels. We demonstrate the effectiveness of this approach using aggregation-induced emission (AIE) and aggregation-caused quenching (ACQ) PTAs, showing significant enhancements in PCE without the need for intricate molecular modifications. Notably, the highest PCEs reach up to 80.9% and 64.4% for AIE-NG and ACQ-NG, respectively, which are nearly 2-fold of their self-aggregate counterparts. Moreover, we elucidate the mechanism underlying PCE enhancement, highlighting the role of strong intermolecular π-π interactions facilitated by nanogel-induced volume contraction. Furthermore, we validate the safety and efficacy of this strategy in in vitro and in vivo models of bacterial infections at safe laser power densities, demonstrating its potential for clinical translation. Our findings offer a straightforward, universal, and versatile method to improve PTT outcomes while minimizing cytotoxicity, paving the way for enhanced treatment of bacterial infections with safe PTT protocols.