Quantifying Dynamic Phenotypic Heterogeneity in Resistant Escherichia coli under Translation-Inhibiting Antibiotics.

Understanding the phenotypic heterogeneity of antibiotic-resistant bacteria following treatment and the transitions between different phenotypes is crucial for developing effective infection control strategies. The study expands upon previous work by explicating chloramphenicol-induced phenotypic heterogeneities in growth rate, gene expression, and morphology of resistant Escherichia coli using time-lapse microscopy. Correlating the bacterial growth rate and cspC expression, four interchangeable phenotypic subpopulations across varying antibiotic concentrations are identified, surpassing the previously described growth rate bistability. Notably, bacterial cells exhibiting either fast or slow growth rates can concurrently harbor subpopulations characterized by high and low gene expression levels, respectively. To elucidate the mechanisms behind this enhanced heterogeneity, a concise gene expression network model is proposed and the biological significance of the four phenotypes is further explored. Additionally, by employing Hidden Markov Model fitting and integrating the non-equilibrium landscape and flux theory, the real-time data encompassing diverse bacterial traits are analyzed. This approach reveals dynamic changes and switching kinetics in different cell fates, facilitating the quantification of observable behaviors and the non-equilibrium dynamics and thermodynamics at play. The results highlight the multi-dimensional heterogeneous behaviors of antibiotic-resistant bacteria under antibiotic stress, providing new insights into the compromised antibiotic efficacy, microbial response, and associated evolution processes.

Dual-functional DNA nanogels for anticancer drug delivery.

DNA hydrogels with unique sequence programmability on nucleic acid framework manifest remarkable attributes, such as high payload capacities, biocompatibility and biosafety. The availability of DNA nanogels with multimodal functionalities remains limited due to the absence of facile gelation methods applicable at the nanometer scale. Here, we developed a one-step assembly of DNA dendrimers into nanogels (DNG) with couple hundred nanometers size. DNG showed robust stability against physical forces and biological degradation for easy purification and sustainable drug release. Long-term stability either in powder or aqueous solution endows DNG easy for shipping, handling and storage. By encoding dual functionalities into separate branches on DNA dendrimers, DNG can accommodate chemodrugs and aptamers with distinctive loading moduli. DNG significantly enhanced the drug efficacy against cancerous cells while minimizing cytotoxicity towards somatic cells, as demonstrated in vitro and in xenografted mice models of breast cancer. Thus, due to their facile assembly and storage, bi-entity encoding, and inherent biocompatibility, DNG exhibits immense prospects as nanoscale vesicles for the synergistic delivery of multimodal theranostics in anticancer treatments. STATEMENT OF SIGNIFICANCE: DNA nanogels were self-assembled via a facile protocol utilizing a DNA dendrimer structure. These nanogels displayed robust stability against physical forces, permitting long term storage in concentrated solutions or as a powder. Furthermore, they exhibited resilience to biological degradation, facilitating sustained drug release. The bi-entity encoded dendritic branches conferred dual functionalities, enabling both chemodrug encapsulation and the presentation of aptamers as targeting motifs. In vivo investigations confirmed the nanogels provide high efficacy in tumor targeting and chemotherapy with enhanced drug efficacy and reduced side effects.

Self-Assembly of Dendritic DNA into a Hydrogel: Application in Three-Dimensional Cell Culture.

With inherent biocompatibility, biodegradability, and unique programmability, hydrogels with a DNA framework show great potential in three-dimensional (3D) cell culture. Here, a DNA hydrogel was assembled by a dendritic DNA with four branches. The hydrogel showed tunable mechanical strength and reversible thixotropy even under a nanomolar DNA concentration. The cell culture medium can be converted into the hydrogel isothermally at physiological temperature. This DNA hydrogel allows both cancer and somatic cells to be seeded in situ and to achieve high proliferation and viability. The bis-entity of dendritic branches enabled the specific loading of bioactive clues to regulate cell behaviors. Thus, the dendritic DNA-assembled hydrogel could serve as a highly biocompatible, readily functionalizing, and easy-casting gel platform for 3D cell culture.

Highly efficient nanomedicine from cationic antimicrobial peptide-protected Ag nanoclusters.

Designing the homogeneous assembly of the bio-nano interface to fine-tune the interactions between the nanoprobes and biological systems is of prime importance to improve the antimicrobial efficiency of nanomedicines. In this work, highly luminescent silver nanoclusters with the homogeneous conjugation of an antimicrobial peptide (referred to as Dpep-Ag NCs) were achieved via the reduction-decomposition-reduction process as a single package. The as-designed Dpep-Ag NCs inherited the two distinctive features of bactericides from the Ag+ species and the antimicrobial peptide of Dpep, and exhibited enhanced bacterial killing efficiency compared with other control groups including BSA-capped Ag NCs and the original antimicrobial peptide bactenecin (Opep)-protected Ag nanoparticles (Opep-Ag NPs). The ultrasmall size feature of Dpep-Ag NCs combined with the positively charged bactericidal tail allow a better interface and interaction with the cell membrane owing to the selective targeting of lipopolysaccharides in the Gram-negative bacteria and electrostatic interaction, facilitating the membrane permeability. Dpep-Ag NCs restrained the E. coli growth visibly and outperformed commercial Ag NPs (30 nm) with reduced (ca. 100-fold) minimal inhibitory concentration. The analysis of infected wound sizes and tissues treated with Dpep-Ag NCs in a murine model reveal obvious differences in the healing effect compared with the other counterparts, demonstrating its antibacterial efficiency in practical application.

Boosted Oxygen Evolution Reactivity via Atomic Iron Doping in Cobalt Carbonate Hydroxide Hydrate.

Cobalt carbonate hydroxide hydrate (CCHH) has long been functioning merely as a precursor to prepare compound catalysts; however, its intrinsic potential for the oxygen evolution reaction (OER) is quite limited due to its poor catalytic activity. Herein, a concept has been proposed to solve this issue by doping Fe into CCHH nanowires grown on nickel foam (denoted as Fe-CCHH/NF) for achieving efficient OER catalysis by electrochemical transformation. The obtained Fe-CCHH/NF-30 exhibits OER catalytic performance with an overpotential of only 200 mV versus the reversible hydrogen electrode (vs. RHE) at a current density of 10 mA cm-2 and small Tafel slope of 50 mV dec-1 in 1 M KOH. Moreover, it displays stability for over 130 h at a large current density of 55 mA cm-2, and no activity decline is observed after the 3000 cycle test. The performance of Fe-CCHH/NF-30 renders it one of the most promising OER catalysts. The density functional theory calculation reveals that the doped Fe can greatly enhance the OER activity by lowering the reactive energy barrier.

A General Method for Transition Metal Single Atoms Anchored on Honeycomb-Like Nitrogen-Doped Carbon Nanosheets.

Excavating and developing highly efficient and cost-effective nonnoble metal single-atom catalysts for electrocatalytic reactions is of paramount significance but still in its infancy. Herein, reported is a general NaCl template-assisted strategy for rationally designing and preparing a series of isolated transition metal single atoms (Fe/Co/Ni) anchored on honeycomb-like nitrogen-doped carbon matrix (M1 -HNC-T1 -T2 , M = Fe/Co/Ni, T1 = 500 °C, T2 = 850 °C). The resulting M1 -HNC-500-850 with M-N4 active sites exhibits superior capability for oxygen reduction reaction (ORR) with the half-wave potential order of Fe1 -HNC-500-850 > Co1 -HNC-500-850 > Ni1 -HNC-500-850, in which Fe1 -HNC-500-850 shows better performance than commercial Pt/C. Density functional theory calculations reveal a choice strategy that the strong p-d-coupled spatial charge separation results the Fe-N4 effectively merges active electrons for elevating d-band activity in a van-Hove singularity like character. This essentially generalizes an optimal electronic exchange-and-transfer (ExT) capability for boosting sluggish alkaline ORR activity. This work not only presents a universal strategy for preparing single-atom electrocatalyst to accelerate the kinetics of cathodic ORR but also provides an insight into the relationship between the electronic structure and the electrocatalytical activity.

Lighting Up the Gold Nanoclusters via Host-Guest Recognition for High-Efficiency Antibacterial Performance and Imaging.

Au nanoclusters (Au NCs) with a unique size effect on the antibacterial performance provide a promising nanoprobe for developing an efficient nanomedicine. However, little progress has been made owing to the low quantum yield and poor stability of Au NCs. In this work, protamine (Prot) functionalized Au NCs (Prot/MTU-Au NCs) with high stability were achieved through a simple mixing with 6-methyl-2-thiouracil-capped Au NCs (MTU-Au NCs) due to the hydrogen bonding between 5-methyl-2-thiouracil (MTU) and the guanidine groups from Prot. Interestingly, a distinctly enhanced photoluminescence from Prot/MTU-Au NCs (ca. 28-fold) was observed due to the formation of rigid host-guest assemblies. We inferred that the cross-linked structure and supramolecular hydrogen bonds both contributed to the fluorescence enhancement and stability. The extra small size of the NCs and the efficient antibacterial capability from the capping shell of Prot encouraged us to probe its antibacterial performance systemically. It was found that the Prot/MTU-Au NCs with highly stable loading of positively charged antibacterial reagents were likely to penetrate into the bacteria and thus enhance the ability to kill both Gram-negative bacteria (Escherichia coli) and Gram-positive bacteria (multiple-resistant Staphylococcus aureus). The synergetic effect between the unique size and the capping layers enabled the minimal inhibitory concentration of the as-derived Prot/MTU-Au NCs reduced by ∼100-fold compared to that with individual Au nanoparticle. The antibacterial mechanism further revealed that membrane injury occurred and reactive oxygen species were generated after the incubation of the bacteria with Prot/MTU-Au NCs. Moreover, the highly luminescent fluorescence and positive surface charge of Prot/MTU-Au NCs could image the bacteria easily, which held great potential for imaging-guided antibacterial platform.

Co3 O4 /Fe0.33 Co0.66 P Interface Nanowire for Enhancing Water Oxidation Catalysis at High Current Density.

Designing well-defined nanointerfaces is of prime importance to enhance the activity of nanoelectrocatalysts for different catalytic reactions. However, studies on non-noble-metal-interface electrocatalysts with extremely high activity and superior stability at high current density still remains a great challenge. Herein, a class of Co3 O4 /Fe0.33 Co0.66 P interface nanowires is rationally designed for boosting oxygen evolution reaction (OER) catalysis at high current density by partial chemical etching of Co(CO3 )0.5 (OH)·0.11H2 O (Co-CHH) nanowires with Fe(CN)6 3- , followed by low-temperature phosphorization treatment. The resulting Co3 O4 /Fe0.33 Co0.66 P interface nanowires exhibit very high OER catalytic performance with an overpotential of only 215 mV at a current density of 50 mA cm-2 and a Tafel slope of 59.8 mV dec-1 in 1.0 m KOH. In particular, Co3 O4 /Fe0.33 Co0.66 P exhibits an obvious advantage in enhancing oxygen evolution at high current density by showing an overpotential of merely 291 mV at 800 mA cm-2 , much lower than that of RuO2 (446 mV). Co3 O4 /Fe0.33 Co0.66 P is remarkably stable for the OER with negligible current loss under overpotentials of 200 and 240 mV for 150 h. Theoretical calculations reveal that Co3 O4 /Fe0.33 Co0.66 P is more favorable for the OER since the electrochemical catalytic oxygen evolution barrier is optimally lowered by the active Co- and O-sites from the Co3 O4 /Fe0.33 Co0.66 P interface.

L-tyrosine methyl ester-stabilized carbon dots as fluorescent probes for the assays of biothiols.

Over the past few decades, assays of biothiols had attracted much attention due to the essential role they played in human physiology, especially using the fluorescent analysis. In most cases, competitive mechanism was often employed, where the metal ions were often introduced as the quenchers and thiols competed with metal ions due to the high binding affinity and strong thiophilicity for 'signal-on' assays. To develop a metal ions-free approach for the assays of thiols, here, L-tyrosine methyl ester capped carbon dots (Tyr-CDs) were employed and prepared as the fluorescent probes. The as-prepared Tyr-CDs displayed narrow size distribution and distinct blue fluorescence with high quantum yield (12.9%) compared with the unmodified CDs. Moreover, Tyr-CDs exhibited higher quenching efficiency due to the efficient energy transfer between Tyr-CDs and the quinone products in the presence of tyrosinase. When the targeted biothiols was present, the catalytic reaction of the tyrosinase to the formation of quinone was inhibited and the fluorescence signal was recovered in a biothiols-concentration-dependent manner, which provided the basis for the analysis of biothiols. The practical application of the present system was demonstrated by testing the biothiols in human plasma samples and good recovery was obtained, indicating that the sensing platform we proposed hold great promise in the accurate detection of biothiols in complex biosystems.

A simple and sensitive fluorescent sensor for methyl parathion based on L-tyrosine methyl ester functionalized carbon dots.

In this paper, a simple and sensitive fluorescent sensor for methyl parathion is developed based on L-tyrosine methyl ester functionalized carbon dots (Tyr-CDs) and tyrosinase system. The carbon dots are obtained by simple hydrothermal reaction using citric acid as carbon resource and L-tyrosine methyl ester as modification reagent. The carbon dots are characterized by transmission electron microscope, high resolution transmission electron microscopy, X-ray diffraction spectrum, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The carbon dots show strong and stable photoluminescence with a quantum yield of 3.8%. Tyrosinase can catalyze the oxidation of tyrosine methyl ester on the surface of carbon dots to corresponding quinone products, which can quench the fluorescence of carbon dots. When organophosphorus pesticides (OPs) are introduced in system, they can decrease the enzyme activity, thus decrease the fluorescence quenching rate. Methyl parathion, as a model of OPs, was detected. Experimental results show that the enzyme inhibition rate is proportional to the logarithm of the methyl parathion concentration in the range 1.0×10(-10)-1.0×10(-4) M with the detection limit (S/N=3) of 4.8×10(-11) M. This determination method shows a low detection limit, wide linear range, good selectivity and high reproducibility. This sensing system has been successfully used for the analysis of cabbage, milk and fruit juice samples.