PVP-capped silver nanoparticles for efficient SERS detection of adenine based on the stabilizing and enrichment roles of PVP.

A polyvinylpyrrolidone-capped (PVP-capped) strategy is reported to synthesize Ag NPs on silicon wafers via galvanic replacement reaction for SERS detection of adenine, where PVP acts as stabilizing agent in synthesis and efficient enrichment in detection. The morphologies of Ag NPs are optimized with uniform particle size by adjusting synthesis conditions, which hold excellent SERS performances like a high enhancement factor of 1.42 × 106, good uniform, reproducibility, and transferable nature. With the protection of the capped PVP, the Ag NPs keep excellent SERS properties even against harsh conditions of high temperature (100 ℃) and strong acid and base for 24 h. Utilizing the structural feature of PVP with abundant carbonyl groups, the PVP-capped Ag NPs achieve efficient enrichment of adenine through hydrogen bonding and π-interactions, which is analyzed by density functional theory. Quantitative detection of adenine is performed with a wide linear range from 10-4 to 10-8 M and a low limit of detection of 1 nM. Detection of adenine in human urine samples is achieved with a recovery of 99.1-103.4% and an RSD of less than 5%.

Galactosylated iron oxide nanoparticles for enhancing oral bioavailability of ceftriaxone.

The current study focuses on the development, characterization, biocompatibility investigation and oral bioavailability evaluation of ceftriaxone (CFT)-loaded lactobionic acid (LBA)-functionalized iron oxide magnetic nanoparticles (MNP-LBA). Atomic force microscopy and dynamic light scattering showed that the developed CFT-loaded MNP-LBA is spherical, with a measured hydrodynamic size of 147 ± 15.9 nm and negative zeta potential values (-35 ± 0.58 mV). Fourier transformed infrared analysis revealed interactions between the nanocarrier and the drug. Nanoparticles showed high drug entrapment efficiencies of 91.5 ± 2.2%, and the drug was released gradually in vitro and shows prolonged in vitro stability using simulated gastrointestinal (GI) fluids. The formulations were found to be highly biocompatible (up to 100 µg/mL) and hemocompatible (up to 1.0 mg/mL). Using an albino rabbit model, the formulation showed a significant enhancement in drug plasma concentration up to 14.46 ± 2.5 µg/mL in comparison with its control (1.96 ± 0.58 µg/mL). Overall, the developed MNP-LBA formulation was found promising for provision of high-drug entrapment, gradual drug release and was appropriate for enhancing the oral delivery of CFT.

A naphthalimide-based lysosome-targeting fluorescent probe for the selective detection and imaging of endogenous peroxynitrite in living cells.

The morpholine (ML) group can be used as a targeting unit for lysosomes. Here, a novel turn-off fluorescence probe for the highly selective imaging of peroxynitrite (ONOO-) produced by the endogenous stimulation of lysosomes in living cells is presented. The probe, denoted ML-NAP-DPPEA, comprises ML and 2-(diphenylphosphino)ethylamine (DPPE) groups attached to the fluorophore naphthalimide (NAP). ML-NAP-DPPEA shows excellent properties, including high selectivity for ONOO-, low cytotoxicity, and no interference, leading to low detection limits (17.6 nM). In the presence of ONOO-, the secondary amine group (NH) is oxidized to an electron-withdrawing group (HN → O), which quenches the fluorescence of ML-NAP-DPPEA. This intracellular lysosomal imaging technique was tested, and the results pointed to its potential use as a probe for studying the biological function and pathological effects of ONOO- in subcellular structure. Graphical abstract.

Dual-Site and Dual-Excitation Fluorescent Probe That Can Be Tuned for Discriminative Detection of Cysteine, Homocystein, and Thiophenols.

Thiols play a vital role in both the physiological process and organic synthesis field, including aliphatic thiols (e.g., Cys, Hcy, and GSH) and thiophenols. As a result of the similarities of thiols in terms of molecular structure and chemical properties, it is difficult for conventional fluorescent probes to distinguish them, which hinders the progress of biological and pathological research. Keeping this in mind, a dual-site and dual-excitation fluorescent probe (YY) was designed to distinguish among Cys, Hcy, and thiophenols by three different reaction paths. When excited at 470 nm, YY only exhibits a fluorescence OFF-ON response toward thiophenols. However, when excited at 453 nm, YY not only displays a fluorescence OFF-ON response toward Hcy and thiophenols (λem = 499 and 561 nm) but also presents a two-stage fluorescence response toward Cys, which possesses a fluorescence OFF-ON response in the first stage (λem = 501 nm) and then a fluorescence ON-OFF response in the second stage (λem = 556 nm). This specific fluorescence response indicates that YY has ability to overcome the above-mentioned challenge to achieve discriminative detection of Cys, Hcy, and thiophenols qualitatively, which promotes the study of thiols in the fields of physiology and pathology. Furthermore, cell-imaging studies show that YY can be applied to the imaging of exogenous Cys, Hcy, and thiophenols through two different emission channels.

Hybrid Metal-Organic-Framework/Inorganic Nanocatalyst toward Highly Efficient Discoloration of Organic Dyes in Aqueous Medium.

Nanoscale metal-organic frameworks (NMOFs) represent a unique class of solids with superior adsorption, mass transport, and catalytic properties. In this study, a facile and novel approach was developed for the generation of hybrid Cu-NMOF/Ce-doped-Mg-Al-LDH nanocatalyst through in situ self-assembly and solvothermal synthesis of a 2D Cu-NMOF, [Cu2(µ-OH)(µ4-btc)(phen)2] n·5 nH2O {H3btc, trimesic acid; phen, 1,10-phenanthroline}, on a cerium-doped Mg-Al layered double hydroxide (Ce-doped-Mg-Al-LDH) matrix. Self-assembly between Cu-NMOF nanocrystals and exfoliated LDH led to their nanoscale mixing and prevented the formation of aggregated Cu-NMOF nanoparticles. In the resulting hybrid nanostructure, Cu-NMOF nanocrystals (∼10-20 nm particle size) are anchored uniformly on a Ce-doped-Mg-Al-LDH's surface, possessing a dimension of several hundred nanometers. Catalytic activity of Cu-NMOF/Ce-doped-Mg-Al-LDH and Cu-NMOF was evaluated under ambient conditions in the reductive degradation (discoloration) of aqueous solutions of 4-nitrophenol (4-NP, model substrate) and a series of commercial organic dyes by applying sodium borohydride as a reducing agent. The Cu-NMOF/Ce-doped-Mg-Al-LDH nanocatalyst exhibited an outstanding catalytic activity toward degradation of 4-NP, with kapp (rate constant) of 0.03 and a catalyst TOF (turnover frequency) up to 7.1 × 103 h-1. Full and very quick discoloration of organic dyes {rhodamine B (RhB), methylene blue (MB), Congo red (CR), methyl orange (MO), and rhodamine 6G (R6G)} was also achieved with TOF values of up to 1.4 × 105/h. A superior activity of the hybrid nanocatalyst over Cu-NMOF can be regarded as a synergic effect among Cu-NMOF and Ce-doped-Mg-Al-LDH components, while the Ce-doped-Mg-Al-LDH carrier acts as a cocatalyst. The hybrid nanocatalyst can easily be recovered and reused successfully for the five consecutive reaction runs with the same catalytic performance. This study also shows that NMOFs can be easily incorporated onto conventional catalyst supports, resulting in hybrid nanocatalysts with a highly uniform structural architecture, controlled chemical composition, and excellent catalytic function.

Synthesis, characterization and drug delivery application of Dapsone based double tailed biocompatible nonionic surfactant.

The increase in antimicrobial resistance has created a crisis that has become top priority for global policy and public health. Antibiotics are constantly being rendered in-effective due to the emergence of bacterial resistance; therefore, novel strategies for improving therapeutic efficacies of existing drugs must be focused. Advancements in nanotechnology have opened up new avenues for enhancing therapeutic efficacy of existing drugs via construction of intelligent and efficient delivery systems. This study reports the synthesis of Dapsone based nonionic surfactant and its utilization as delivery system for Ceftriaxone sodium. The synthesized nonionic surfactant was characterized via mass spectrometry and 1H NMR and IR spectroscopic techniques. The drug loaded vesicles of newly synthesized sulfur based nonionic were formed through thin film hydration method and characterized for drug entrapment efficiency, vesicles size, zeta potential, morphology using UV-vis spectrometry, dynamic light scattering (DLS) and atomic force microscopic (AFM) techniques. The biocompatibility of newly synthesized surfactant was assessed using blood hemolysis and in-vitro cells cytotoxicity. Antibacterial potential of drug loaded vesicles was assessed in gram positive and gram negative bacterial cultures. The spectroscopic results confirm successful synthesis of novel sulfur based nonionic surfactant that formed spherical shaped drug loaded vesicles with an average size of 97.95 ± 3.45 nm and 56.3 ± 3.15 % entrapment of the model drug (Ceftriaxone sodium). The vesicles displayed negative surface charge of -16.8 ± 3.72 mV and released the entrapped drug in a controlled way in-vitro drug release. The drug loaded vesicular formulation showed enhanced cellular uptake and greater antibacterial potentials when compared with control. Results of this study show that the Dapsone based surfactant is safe, biocompatible, non-toxic and can be used as promising vesicular carrier for enhancing therapeutic efficacy of antibacterial drug, Ceftriaxone sodium.

A ratiometric fluorescent sensor for rapid detection of the pyroglutamate aminopeptidase-1 in mouse tumors.

Pyroglutamate aminopeptidase-1 (PGP-1) is an important enzyme that plays an indispensable role in the process of inflammation. Up to now, few reports have been reported on the detection of PGP-1 activity in vivo and in vitro, and there are no reports on ratiometric detection. Here, the first red-emitting ratiometric fluorescent sensor (DP-1) for the specific detection of PGP-1 both in vivo and in vitro was designed and synthesized by using DCD-NH2 as the luminescent parent and pyroglutamate as a recognition group. After interacting with PGP-1, the amide bond is hydrolyzed by the enzyme and the color of the solution changes from yellow (λabs = 420 nm) to red (λabs = 520 nm), accompanied by obvious fluorescence emission wavelength change (from ∼564 nm to ∼616 nm). The probe has high specificity and sensitivity towards PGP-1 in about 10 min, and the DL is as low as 0.25 ng mL-1. Interestingly, under the stimulation of Freund's incomplete adjuvant and lipopolysaccharide, the imaging of DP-1 in HepG2 and RAW264 cells shows that the expression of PGP-1 is associated with inflammation. What's more, for the first, the imaging of a mouse tumor model confirms that the enzyme is closely related to the occurrence of some inflammation and tumor diseases. These results indicate that DP-1 can be used as an effective tool for real-time monitoring of PGP-1 levels both in vivo and in vitro and the study of inflammatory tumor pathology.

Electrospun Nanofiber-Based Viroblock/ZnO/PAN Hybrid Antiviral Nanocomposite for Personal Protective Applications.

Designing novel antiviral personal protective equipment (PPE) is crucial for preventing viral infections such as COVID-19 in humans. Here, we fabricate an electrospun nanofiber-based Viroblock (VB)-loaded polyacrylonitrile (PAN)/zinc oxide (ZnO) hybrid nanocomposite for PPE applications. Five different concentrations of Viroblock (0.5%, 1.5%, 2.5%, 3.5%, and 5%) were added to PAN/ZnO solution and loaded for electrospinning. The developed samples reflected antibacterial activity of 92.59% and 88.64% against Staphylococcus aureus and Pseudomonas aeruginosa bacteria, respectively, with 5% VB loading. Moreover, a significant reduction in virus titer (37%) was observed with the 5% VB/PAN/ZnO nanofiber sheet. Hence, VB-loaded PAN/ZnO nanofibers have great potential to kill enveloped viruses such as influenzas and coronaviruses and could be the ideal candidate for the development of nanofiber-based PPE, such as facemasks and surgical gowns, which can play a key role in the protection of frontline health workers and the general public in the COVID-19 pandemic.

Enhancement in Oral Absorption of Ceftriaxone by Highly Functionalized Magnetic Iron Oxide Nanoparticles.

The present study aims at the development, characterization, biocompatibility investigation and oral bioavailability evaluation of ceftriaxone (CFT)-loaded N'-methacryloylisonicotinohydrazide (MIH)-functionalized magnetic nanoparticles (CFT-MIH-MNPs). Atomic force microscopy (AFM) and dynamic light scattering (DLS) showed that the developed CFT loaded MIH-MNPs are spherical, with a measured hydrodynamic size of 184.0 ± 2.7 nm and negative zeta potential values (-20.2 ± 0.4 mV). Fourier transformed infrared spectroscopic (FTIR) analysis revealed interactions between the nanocarrier and the drug. Nanoparticles showed high drug entrapment efficiency (EE) of 79.4% ±1.5%, and the drug was released gradually in vitro and showed prolonged in vitro stability using simulated gastrointestinal tract (GIT) fluids. The formulations were found to be highly biocompatible (up to 100 µg/mL) and hemocompatible (up to 1.0 mg/mL). Using an albino rabbit model, the formulation showed a significant enhancement in drug plasma concentration up to 14.4 ± 1.8 µg/mL in comparison with its control (2.0 ± 0.6 µg/mL). Overall, the developed CFT-MIH-MNPs formulation was promising for provision of high drug entrapment, gradual drug release and suitability for enhancing the oral delivery of CFT.

Isoniazid Conjugated Magnetic Nanoparticles Loaded with Amphotericin B as a Potent Antiamoebic Agent against Acanthamoeba castellanii.

The pathogenic free-living amoeba, Acanthamoeba castellanii, is responsible for a rare but deadly central nervous system infection, granulomatous amoebic encephalitis and a blinding eye disease called Acanthamoeba keratitis. Currently, a combination of biguanides, amidine, azoles and antibiotics are used to manage these infections; however, the host cell cytotoxicity of these drugs remains a challenge. Furthermore, Acanthamoeba species are capable of transforming to the cyst form to resist chemotherapy. Herein, we have developed a nano drug delivery system based on iron oxide nanoparticles conjugated with isoniazid, which were further loaded with amphotericin B (ISO-NPs-AMP) to cause potent antiamoebic effects against Acanthamoeba castellanii. The IC50 of isoniazid conjugated with magnetic nanoparticles and loaded with amphotericin B was found to be 45 µg/mL against Acanthamoeba castellanii trophozoites and 50 µg/mL against cysts. The results obtained in this study have promising implications in drug discovery as these nanomaterials exhibited high trophicidal and cysticidal effects, as well as limited cytotoxicity against rat and human cells.

Nanoscale Phenotypic Textures of Yersinia pestis Across Environmentally-Relevant Matrices.

The persistence of bacterial pathogens within environmental matrices plays an important role in the epidemiology of diseases, as well as impacts biosurveillance strategies. However, the adaptation potentials, mechanisms for survival, and ecological interactions of pathogenic bacteria such as Yersinia pestis are largely uncharacterized owing to the difficulty of profiling their phenotypic signatures. In this report, we describe studies on Y. pestis organisms cultured within soil matrices, which are among the most important reservoirs for their propagation. Morphological (nanoscale) and phenotypic analysis are presented at the single cell level conducted using Atomic Force Microscopy (AFM), coupled with biochemical profiles of bulk populations using Fatty Acid Methyl Ester Profiling (FAME). These studies are facilitated by a novel, customizable, 3D printed diffusion chamber that allows for control of the external environment and easy harvesting of cells. The results show that incubation within soil matrices lead to reduction of cell size and an increase in surface hydrophobicity. FAME profiles indicate shifts in unsaturated fatty acid compositions, while other fatty acid components of the phospholipid membrane or surface lipids remained consistent across culturing conditions, suggesting that phenotypic shifts may be driven by non-lipid components of Y. pestis.

A ratiometric fluorescent probe for detection of endogenous and exogenous hydrogen sulfide in living cells.

A ratiometric visualized fluorescent probe of H2S of intramolecular charge transfer (ICT) and excited intramolecular proton transfer (ESIPT) mechanisms due to solvation effects has been designed and synthesized. This chemosensor shows the distinct signal changes with dual-emission in blue and green fluorescence spectral channel (from 495 nm to 525 nm) upon the addition of H2S in a single wavelength excitation. This chemosensor exhibits the low detection limit (91 nM) and high sensitivity and selectivity. Based on this, this chemosensor was successfully used not only to monitor H2S exogenously but also used to detect and image the endogenously generated H2S in HeLa cells with excellent performance.

Customizable 3D printed diffusion chambers for studies of bacterial pathogen phenotypes in complex environments.

Gaps in our understanding of the natural ecology and survival mechanisms of pathogenic bacteria in complex microenvironments such as soil typically occur due to the difficulty in characterizing biochemical profiles and morphological characteristics as they exist in environmental samples. Conversely, accurate simulation of the abiotic and biotic chemistries of soil habitats within the laboratory is often a significant challenge. Herein, we present the fabrication of customizable and precisely engineered 3D printed diffusion chambers that can be used to incubate bacterial cultures directly in soil matrices within a controlled laboratory experiment, and study the dynamics between bacterial cells and soil components. As part of the design process, different types of 3D printing materials were evaluated for ease of sterilization, structural integrity throughout the experiment, as well as cost/ease of production. To demonstrate potential applications for environmental studies, the diffusion chamber was used to incubate cultures of Bacillus cereus T-strain and Escherichia coli strain O157 directly in soil matrices. We show that the chamber facilitates diffusion of abiotic/biotic components of the soil with target cells without contamination from in situ microbial communities, while allowing for single cell and ensemble level phenotypic analyses of bacteria cultured with and without soil matrices.

N-doped carbon coated Mn3O4/PdCu nanocomposite as a high-performance catalyst for 4-nitrophenol reduction.

This paper reports the chemical synthesis of highly-active Mn3O4/PdCu nanocomposites coated with N-doped carbon (NC) shell using polydopamine (PDA) as the carbon source, which provides high specific surface area and pore volume. The structure and morphology of Mn3O4/PdCu@NC nanocomposites were systematically studied. Taking advantage of the synergistic effects of PdCu alloy and Mn3O4 support, the Mn3O4/PdCu@NC catalyst exhibited an outstanding activity toward the reduction of 4-nitrophenol (4-NP), in comparison to Mn3O4/PdM@NC (M = Ni, Au, Ag), Mn3O4/PdCu@PDA, and commercial Pd/C catalyst. Owing to the protection by NC shell, the as-prepared catalyst showed stable conversion efficiency of up to 90% over ten successive cycles. Considering 4-NP as one of the important organic pollutants from industrial production, the effects of various inorganic and organic species on the catalytic efficiency were further tested and most of them had negligible impact. This strategy of utilizing an N-doped carbon shell could be extended to obtain PdCu alloys supported on other metal oxides, making it applicable for applications in treatment of environmental pollutants.

BODIPY-based asymmetric monosubstituted (turn-on) and symmetric disubstituted (ratiometric) fluorescent probes for selective detection of phosgene in solution and gas phase.

Here, we designed and synthesized two fluorescent probes for detecting phosgene by nucleophilic substitution reaction using BODIPY as a fluorophore and 2-aminobenzylamine as reactive functional group. For the first time, we have studied the similarities and differences between asymmetric monosubstituted (1) and symmetric disubstituted (2) probes. A monosubstituted probe 1 (having a 2-aminobenzylamine group at the 3-position of BODIPY) has fluorescence-enhancing (weak green fluorescence to strong green fluorescence) responce to phosgene in 30 s with a large Stokes shift (∼70 nm) and sensitive property (DL = 0.81 nM); while the disubstituted probe 2 (having two 2-aminobenzylamine groups at the 3, 5-position of BODIPY) has a ratiometric fluorescent responce to phosgene in 2 min. The linear range of the response is wider than that of the monosubstitution probe 1, and the detection limit is also lower (2.36 nM). In addition, probes 1 and 2 can effectively eliminate the interference of other substances with similar chemical structure as phosgene. They can not only detect phosgene in solution environment, but also in gaseous environment quickly and sensitively.

Ratiometric fluorescent probe based on ESIPT for the highly selective detection of cysteine in living cells.

A new simple and facile fluorescent ratiometric probe (probe 1) has been designed for the detection of cysteine (Cys). Probe 1 as the fluorophore contains a typical excited-state intramolecular proton transfer (ESIPT) dye. In probe 1 to restore the ESIPT process, the group of acrylate which acts as the recognition unit can block the ESIPT process and can be selectively achieved by Cys, which makes the probe as the ratiometric fluorescent detection for Cys in aqueous solution. This probe shows highly selectivity towards Cys over other biothiols including glutathione (GSH) and homocysteine (Hcy) because of specific cyclization between Cys and acrylate group, and having a detection limit of 42.3 nM. In addition, the experiment of cell imaging shows that probe 1 possesses low cytotoxicity and excellent cell permeability towards the living cells, and has been successfully applied to the ratiometric imaging not only for the endogenous but also for the exogenous cysteine in the living cells effectively.

Optimization of iron-doped Ni3S2 nanosheets by disorder engineering for oxygen evolution reaction.

Nowadays, disorder engineering of catalytic materials has attracted significant attention because it can increase catalytic active sites and thus enhance their catalytic activity for electrocatalytic reactions. However, it is extremely important to uncover the relationship between disorder engineering and catalytic activity. Particularly, deep exploration of the relationship is very important for fabricating excellent highly active catalysts for oxygen evolution reaction (OER), which is one of the promising technologies in energy transition. In this study, we prepared Fe-doped Ni3S2 materials and simultaneously controlled the disorder degree by regulating the ion concentration to improve the activity for OER. By investigating the as-prepared catalysts with various disorder degrees for OER, we also explored the relationship between the disordered structure and OER catalytic performance. In particular, the optimized electrocatalyst with an appropriate disorder degree showed excellent activity and stability. We hope that this study provides a feasible direction to fabricate and optimize transition metal chalcogenide (TMC) electrocatalysts as efficient and stable electrocatalysts for OER.

Mechanochromic luminescent covalent organic frameworks for highly selective hydroxyl radical detection.

The mechanochromic luminescence phenomenon was first reported in the low-cost mechanochemical (MC) synthesis process of a covalent organic framework (COF-TpMA (MC)) prepared using triformylphloroglucinol (Tp) and melamine (MA) as precursors, which shows excellent performance as a hydroxyl radical (˙OH) detector in living systems. This work not only shows a new kind of mechanochromic luminescent material but also exhibits a close relationship between the π-π stacking and luminescence properties of COF materials.