Self-Assembled Cationic Nanoparticles Combined with Curcumin against Multidrug-Resistant Bacteria.

The overuse of antibiotics exacerbates the development of antibiotic-resistant bacteria, threatening global public health, while most traditional antibiotics act on specific targets and sterilize through chemical modes. Therefore, it is a desperate need to design novel therapeutics or extraordinary strategies to overcome resistant bacteria. Herein, we report a positively charged nanocomposite PNs-Cur with a hydrodynamic diameter of 289.6 nm, which was fabricated by ring-opening polymerization of ε-caprolactone and Z-Lys-N-carboxyanhydrides (NCAs), and then natural curcumin was loaded onto the PCL core of PNs with a nanostructure through self-assembly, identified through UV-vis, and characterized by scanning electron microscopy (SEM) and dynamic light scattering (DLS). Especially, the self-assembly dynamics of PNs was simulated through molecular modeling to confirm the formation of a core-shell nanostructure. Biological assays revealed that PNs-Cur possessed broad-spectrum and efficient antibacterial activities against both Gram-positive and Gram-negative bacteria, including drug-resistant clinical bacteria and fungus, with MIC values in the range of 8-32 µg/mL. Also, in vivo evaluation showed that PNs-Cur exhibited strong antibacterial activities in infected mice. Importantly, the nanocomposite did not indeed induce the emergence of drug-resistant bacterial strains even after 21 passages, especially showing low toxicity regardless of in vivo or in vitro. The study of the antibacterial mechanism indicated that PNs-Cur could indeed destruct membrane potential, change the membrane potential, and cause the leakage of the cytoplasm. Concurrently, the released curcumin further plays a bactericidal role, eventually leading to bacterial irreversible apoptosis. This unique bacterial mode that PNs-Cur possesses may be the reason why it is not easy to make the bacteria susceptible to easily produce drug resistance. Overall, the constructed PNs-Cur is a promising antibacterial material, which provides a novel strategy to develop efficient antibacterial materials and combat increasingly prevalent bacterial infections.

Identification of Cisplatin and Palladium(II) Complexes as Potent Metallo-ß-lactamase Inhibitors for Targeting Carbapenem-Resistant Enterobacteriaceae.

The emergence and prevalence of carbapenem-resistant bacterial infection have seriously threatened the clinical use of almost all ß-lactam antibacterials. The development of effective metallo-ß-lactamase (MßL) inhibitors to restore the existing antibiotics efficacy is an ideal alternative. Although several types of serine-ß-lactamase inhibitors have been successfully developed and used in clinical settings, MßL inhibitors are not clinically available to date. Herein, we identified that cisplatin and Pd(II) complexes are potent broad-spectrum inhibitors of the B1 and B2 subclasses of MßLs and effectively revived Meropenem efficacy against MßL-expressing bacteria in vitro. Enzyme kinetics, thermodynamics, inductively coupled plasma atomic emission spectrometry (ICP-AES), matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS), and site-directed mutation assays revealed that these metal complexes irreversibly inhibited NDM-1 through a novel inhibition mode involving binding to Cys208 and displacing one Zn(II) ion of the enzyme with one Pt(II) containing two NH3's or one Pd(II) ion. Importantly, the combination therapy of Meropenem and metal complexes significantly suppressed the development of higher-level resistance in bacteria producing NDM-1, also effectively reduced the bacterial burden in liver and spleen of mice infected by carbapenem-resistant Enterobacteriaceae producing NDM-1. These findings will offer potential lead compounds for the further development of clinically useful inhibitors targeting MßLs.

meta-Substituted benzenesulfonamide: a potent scaffold for the development of metallo-ß-lactamase ImiS inhibitors.

Metallo-ß-lactamase (MßL) ImiS contributes to the emergence of carbapenem resistance. A potent scaffold, meta-substituted benzenesulfonamide, was constructed and assayed against MßLs. The twenty-one obtained molecules specifically inhibited ImiS (IC50 = 0.11-9.3 µM); 2g was found to be the best inhibitor (IC50 = 0.11 µM), and 1g and 2g exhibited partially mixed inhibition with K i of 8.0 and 0.55 µM. The analysis of the structure-activity relationship revealed that the meta-substitutes improved the inhibitory activity of the inhibitors. Isothermal titration calorimetry (ITC) assays showed that 2g reversibly inhibited ImiS. The benzenesulfonamides exhibited synergistic antibacterial effects against E. coli BL21 (DE3) cells with ImiS, resulting in a 2-4-fold reduction in the MIC of imipenem and meropenem. Also, mouse experiments showed that 2g had synergistic efficacy with meropenem and significantly reduced the bacterial load in the spleen and liver after a single intraperitoneal dose. Tracing the ImiS in living E. coli cells by RS at a super-resolution level (3D-SIM) showed that the target was initially associated on the surface of the cells, then there was a high density of uniform localization distributed in the cytosol of cells, and it finally accumulated in the formation of inclusion bodies at the cell poles. Docking studies suggested that the sulfonamide group acted as a zinc-binding group to coordinate with Zn(ii) and the residual amino acid within the CphA active center, tightly anchoring the inhibitor at the active site. This study provides a highly promising scaffold for the development of inhibitors of ImiS, even the B2 subclasses of MßLs.

Silver Nanoparticle Conjugated Star PCL-b-AMPs Copolymer as Nanocomposite Exhibits Efficient Antibacterial Properties.

The traditional antibiotics have specific intracellular targets and disinfect in chemical ways, and the drug-resistance induced by the antibiotics has grown into an emerging threat. It is urgent to call for novel strategies and antibacterial materials to control this situation. Herein, we report a class of silver-decorated nanocomposite AgNPs@PCL-b-AMPs as potent nanoantibiotic, constructed by ring-opening polymerization of the monomers ε-caprolactone, Z-Lys-N-carboxyanhydrides (NCAs), and Phe-NCAs, then decorated with AgNPs, and characterized by SEM, TEM, and DLS. The biological assays revealed that the nanocomposite possessed strong antibacterial efficacy against both Gram-positive and Gram-negative bacteria including clinical isolated bacteria MRSA, VRE, P. aeruginosa, and K. pneumonia, exhibiting a MIC value range in 2-8 µg/mL. Importantly, the S. aureus and P. aeruginosa treated with the nanocomposite did not show drug-resistance even after 21 passages. Also, in vivo anti-infective assays showed that the nanocomposite was able to effectively kill bacteria in the infected viscera of mice. The study of the sterilization mechanism showed that the nanocomposite exhibited a multimodal antimicrobial mechanism, including irreversibly damaging the membrane structure, making the leakage of intracellular ions and subsequently inducing generation of the reactive oxygen species (ROS), ultimately sterilizing the bacteria. The nanocomposite exhibits effective broad-spectrum antibacterial properties and shows low toxicity to the mammalian cells/animal. Overall, the AgNPs@PCL-b-AMPs gained in this work show great potential as a highly promising antibacterial material for biomedical applications including drug-resistant bacterial infection.

Construction, mechanism, and antibacterial resistance insight into polypeptide-based nanoparticles.

The emergence of drug-resistant bacteria poses a serious threat to public health. The traditional antibiotics have specific intracellular targets and disinfect via chemical ways, which easily lead to the development of drug resistance, therefore, cationic peptides as promising antibiotic agents have attracted extensive attention due to their unique properties. Herein, we report a class of amphiphilic peptide-based pectinate polymers with primary amino groups. The polymers spontaneously self-assembled into the positively charged nanoparticles, which were evaluated and confirmed by scanning electron microscopy (SEM) and dynamic light scattering (DLS). Biological assays revealed that the nanoparticles showed broad-spectrum antibacterial efficacy against both Gram-positive and Gram-negative bacteria, exhibiting a MIC of 16 µg mL-1 against six clinical bacteria, namely, E. faecalis, S. aureus, MRSA, VRE, P. aeruginosa, and K. pneumonia, and three bacterial strains E. coli and E. coli producing NDM-1 and ImiS, and showed a sterilization rate of 95.6% and 94.7% on S. aureus and E. coli, respectively. Importantly, the nanoparticles did not result in drug-resistance for both the normal and drug-resistant bacteria tested after 14 passages and showed low toxicity on the mouse fibroblast cells (L929). The fluorescence staining, electrical conductivity, SEM, and surface plasmon resonance (SPR) characterization suggested that the nanoparticles initially bound to the surface of the bacteria, then pierced into the membranes of the bacteria with their phenyl groups, and finally disrupted the membranes, resulting in ions leaking out and thus exhibiting broad-spectrum antibacterial efficacy. This bactericidal mechanism that the nanoparticles employed does not lead the bacteria susceptible to developing drug resistance. This study provides a promising pathway for the development of the efficient antibacterial materials.