Vancomycin-Modified Mesoporous Silica Nanoparticles for Selective Recognition and Killing of Pathogenic Gram-Positive Bacteria Over Macrophage-Like Cells

Rapid, reliable recognition and detection of bacteria from an authentic specimen have been gained increasing interests in the past decades. Various materials have been designed and prepared for implementation of bacterial recognition and treatment in the artificial systems. However, in the complicated physiological condition, the macrophages always compromise the outcomes of bacterial detection and/or treatment. In this work, we demonstrated the vancomycin-modified mesoporous silica nanoparticles (<b>MSNs⊂Van</b>) for efficiently targeting and killing gram-positive bacteria over macrophage-like cells. Owing to the specific hydrogen bonding interactions of vancomycin toward the terminal d-alanyl-d-alanine moieties of gram-positive bacteria, the <b>MSNs⊂Van</b> exhibited enhanced recognition for gram-positive bacteria due to the multivalent hydrogen binding effect. Furthermore, the fluorescent molecules (FITC) were covalently decorated inside of mesopores of MSNs for tracking and visualizing the <b>MSNs⊂Van</b> during the detection/treatment processes. Upon incubation of FITC decorated MSNs with bacteria (i.e., <i>S. aureus</i> and <i>E. coli</i> as gram-positive and gram-negative bacteria, respectively) or macrophage-like cells (Raw 264.7), the fluorescence signals in <i>S. aureus</i> were 2–4 times higher than that in <i>E. coli</i> and no detectable fluorescence signals were observed in Raw 264.7 cells under the same condition. Finally, the <b>MSNs⊂Van</b> showed unambiguous antibacterial efficacy without decrease in cell viability of macrophage-like cells. This new strategy opens a new door for specific detection and treatment of pathogenic bacteria with minimized side effects

Tautomeric Polymorphism of 4‑Hydroxynicotinic Acid

4-Hydroxynicotinic acid (4-HNA) was discovered to exist in the solid state as either 4-HNA or its tautomer 4-oxo-1,4-dihydropyridine-3-carboxylic acid (4-ODHPCA) in three polymorphs and two hydrates. Packing motifs differ as each of the three oxygen atoms acts as the hydrogen-bond acceptor, respectively, in the anhydrate forms, while in the hydrate forms, water molecules participate in hydrogen bonding with 4-HNA. Phase behaviors of the forms were characterized by differential scanning calorimetry (DSC), hot-stage microscopy (HSM), and thermogravimetric analysis (TGA). It was found that anhydrates I and II converted into III during heating; the two hydrate forms dehydrated at different temperatures and eventually transformed into anhydrate III, and sublimation of all five forms led to form III when the crystals were heated. Quantum mechanical calculations were performed providing further insight into the polymorphism

Core–Shell Supramolecular Gelatin Nanoparticles for Adaptive and “On-Demand” Antibiotic Delivery

The treatment of bacterial infection is one of the most challenging tasks in the biomedical field. Antibiotics were developed over 70 years and are regarded as the most efficient type of drug to treat bacterial infection. However, there is a concern that the overuse of antibiotics can lead to a growing number of multidrug-resistant bacteria. The development of antibiotic delivery systems to improve the biodistribution and bioavailability of antibiotics is a practical strategy for reducing the generation of antibiotic resistance and increasing the lifespan of newly developed antibiotics. Here we present an antibiotic delivery system (Van⊂SGNPs@RBC) based on core–shell supramolecular gelatin nanoparticles (SGNPs) for adaptive and “on-demand” antibiotic delivery. The core composed of cross-linked SGNPs allows for bacterial infection–microenvironment responsive release of antibiotics. The shell coated with uniform red blood cell membranes executes the function of disguise for reducing the clearance by the immune system during the antibiotic delivery, as well as absorbs the bacterial exotoxin to relieve symptoms caused by bacterial infection. This approach demonstrates an innovative and biomimetic antibiotic delivery system for the treatment of bacterial infection with a minimum dose of antibiotics

Selenylsulfide Bond-Launched Reduction-Responsive Superparamagnetic Nanogel Combined of Acid-Responsiveness for Achievement of Efficient Therapy with Low Side Effect

With the objective to achieve in-between reduction-responsive drug release, selenylsulfide bond was first explored as a reduction cleavable linkage, compared with the most commonly employed disulfide and diselenide bonds. The reductive nanogel, with a combination of superparamagnetic and acid responsiveness, was fabricated. The expected release profiles were testified. Cytotoxicity assays illustrated the remarkable inhibition to the growth of HeLa cells, in contrast, high tolerance to L02 cells. In vivo investigation exhibited the obvious shrinkage in tumor but a healthy appearance. Hematoxylin-eosin staining and histological examination revealed the lower toxicity. The complex nanogels would have appeared highly promising in cancer therapy

Structural Isomerization of 2‑Anilinonicotinic Acid Leads to a New Synthon in 6‑Anilinonicotinic Acids

Through structural modification of 2-anilinonicotinic acid by isomerization, a new synthon, acid-aminopyridine, is created, and the two original synthons, i.e., the acid–acid homosynthon and acid–pyridine heterosynthon are no longer observed in the newly designed 6-anilinonicotinic acids. The new synthon has a hydrogen-bond strength rivaling that of the acid–acid homosynthon and the acid–pyridine heterosynthon, as suggested by theoretical calculations, which explains its formation

LiMn_0.8Fe_0.2PO₄/C Nanoparticles via Polystyrene Template Carburizing Enhance the Rate Capability and Capacity Reversibility of Cathode Materials

In order to unlock the electrochemical performance ability of manganese-based lithium ferromanganese phosphate cathode materials, CP1–LiMn0.8Fe0.2PO4/C (coprecipitation) nanocomposites were prepared by introducing polystyrene nanospheres as templates and carbon sources into the coprecipitation method combined with a multistage carburizing heat treatment. In the processes of heat treatment, polystyrene nanospheres can not only build a conductive carbon layer and optimize the electron transport path but also refine the particles and inhibit the nanoparticle aggregation. The interconnected conductive carbon coating significantly improves the diffusion coefficient of lithium ions, which assists LiMn0.8Fe0.2PO4 in lifting discharge specific capacity and cycle performance. The test results show that the as-prepared CP1–LiMn0.8Fe0.2PO4/C shows superior rate capability (130.5 mAh g–1 at 0.1C and 92.8 mAh g–1 at 5C) and capacity reversibility (95.5% after 200 cycles at 0.5C)