Biodegradable Nanocomposite of ZnS(Mn) Quantum Dots Immobilized Graphene Oxide for Bioimaging Applications.

Developing a biocompatible and biodegradable graphene-based fluorescent nanoprobe with the ability to visualize live cells could be interesting for intracellular imaging and monitoring the efficiency of chemotherapy. Herein, we report a biodegradable and biocompatible hybrid fluorescent graphene oxide (GO)-ZnS(Mn) composite synthesized via in situ growth of ZnS(Mn) quantum dots (QDs) on the surface of GO in the aqueous medium. The prepared 'GO-ZnS(Mn)' composite was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and high-resolution transmission electron microscopy (HR-TEM) along with selected area electron diffraction (SAED). Further, the fluorescence properties of the GO-ZnS(Mn) composite were studied using fluorescence emission spectroscopy. The composite material exhibited a strong and broad visible light fluorescence from 500 to 600 nm by excitation with 365 nm (UV) light. The cytotoxic experiments of folic acid (FA) conjugated GO-ZnS(Mn) using MTT [(3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide)] assay revealed that the composite had excellent biocompatibility even at higher concentrations up to 200 µg/mL in HeLa cell lines. Next, the bioimaging experiments carried out using confocal fluorescence laser scanning microscopy (CLSM) revealed that GO-ZnS(Mn) composite was taken up by the HeLa cells effectively within 12 h of incubation via receptor (folate) mediated endocytosis with strong fluorescence throughout the cell surface. Finally, the biodegradability of GO-ZnS(Mn) composite was studied by treating it with human myeloperoxidase enzyme (hMPO) isolated from the primary immune cells, neutrophils, which is important to understand the in vivo fate of GO-Zns(Mn). The HR-TEM and Raman analyses confirmed the biodegradation of GO-ZnS(Mn) within 15 h of hMPO treatment. Thus, the biodegradable GO-ZnS (Mn) composite could be helpful for chemotherapy and bioimaging applications.

Interaction of silver nanoparticles with serum proteins affects their antimicrobial activity in vivo.

The emergence of multidrug-resistant bacteria is a global threat for human society. There exist recorded data that silver was used as an antimicrobial agent by the ancient Greeks and Romans during the 8th century. Silver nanoparticles (AgNPs) are of potential interest because of their effective antibacterial and antiviral activities, with minimal cytotoxic effects on the cells. However, very few reports have shown the usage of AgNPs for antibacterial therapy in vivo. In this study, we deciphered the importance of the chosen methods for synthesis and capping of AgNPs for their improved activity in vivo. The interaction of AgNPs with serum albumin has a significant effect on their antibacterial activity. It was observed that uncapped AgNPs exhibited no antibacterial activity in the presence of serum proteins, due to the interaction with bovine serum albumin (BSA), which was confirmed by UV-Vis spectroscopy. However, capped AgNPs [with citrate or poly(vinylpyrrolidone)] exhibited antibacterial properties due to minimized interactions with serum proteins. The damage in the bacterial membrane was assessed by flow cytometry, which also showed that only capped AgNPs exhibited antibacterial properties, even in the presence of BSA. In order to understand the in vivo relevance of the antibacterial activities of different AgNPs, a murine salmonellosis model was used. It was conclusively proved that AgNPs capped with citrate or PVP exhibited significant antibacterial activities in vivo against Salmonella infection compared to uncapped AgNPs. These results clearly demonstrate the importance of capping agents and the synthesis method for AgNPs in their use as antimicrobial agents for therapeutic purposes.

Chitosan-dextran sulphate nanocapsule drug delivery system as an effective therapeutic against intraphagosomal pathogen Salmonella.

OBJECTIVES: The ability to target conventional drugs efficiently inside cells to kill intraphagosomal bacteria has been a major hurdle in treatment of infective diseases. We aimed to develop an efficient drug delivery system for combating infection caused by Salmonella, a well-known intracellular and intraphagosomal pathogen. Chitosan-dextran sulphate (CD) nanocapsules were assessed for their efficiency in delivering drugs against Salmonella. METHODS: The CD nanocapsules were prepared using the layer-by-layer method and loaded with ciprofloxacin or ceftriaxone. Antibiotic-loaded nanocapsules were analysed in vitro for their ability to enter epithelial and macrophage cells to kill Salmonella. In vivo pharmacokinetics and organ distribution studies were performed to check the efficiency of the delivery system. The in vivo antibacterial activity of free antibiotic and antibiotic loaded into nanocapsules was tested in a murine salmonellosis model. RESULTS: In vitro and in vivo experiments showed that this delivery system can be used effectively to clear Salmonella infection. CD nanocapsules were successfully employed for efficient targeting and killing of the intracellular pathogen at a dosage significantly lower than that of the free antibiotic. The increased retention time of ciprofloxacin in the blood and organs when it was delivered by CD nanocapsules compared with the conventional routes of administration may be the reason underlying the requirement for a reduced dosage and frequency of antibiotic administration. CONCLUSIONS: CD nanocapsules can be used as an efficient drug delivery system to treat intraphagosomal pathogens, especially Salmonella infection. This delivery system might be used effectively for other vacuolar pathogens including Mycobacteria, Brucella and Legionella.

Development of micro-shock wave assisted dry particle and fluid jet delivery system.

Small quantity of energetic material coated on the inner wall of a polymer tube is proposed as a new method to generate micro-shock waves in the laboratory. These micro-shock waves have been harnessed to develop a novel method of delivering dry particle and liquid jet into the target. We have generated micro-shock waves with the help of reactive explosive compound [high melting explosive (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) and traces of aluminium] coated polymer tube, utilising ∼9 J of energy. The detonation process is initiated electrically from one end of the tube, while the micro-shock wave followed by the products of detonation escape from the open end of the polymer tube. The energy available at the open end of the polymer tube is used to accelerate tungsten micro-particles coated on the other side of the diaphragm or force a liquid jet out of a small cavity filled with the liquid. The micro-particles deposited on a thin metal diaphragm (typically 100-µm thick) were accelerated to high velocity using micro-shock waves to penetrate the target. Tungsten particles of 0.7 µm diameter have been successfully delivered into agarose gel targets of various strengths (0.6-1.0 %). The device has been tested by delivering micro-particles into potato tuber and Arachis hypogaea Linnaeus (ground nut) stem tissue. Along similar lines, liquid jets of diameter ∼200-250 µm (methylene blue, water and oils) have been successfully delivered into agarose gel targets of various strengths. Successful vaccination against murine salmonellosis was demonstrated as a biological application of this device. The penetration depths achieved in the experimental targets are very encouraging to develop a future device for biological and biomedical applications.

Corrigendum: Successful treatment of biofilm infections using shock waves combined with antibiotic therapy.

This corrects the article DOI: 10.1038/srep17440.

Modulating cellular autophagy for controlled antiretroviral drug release.

AIM: Pharmacologic agents that affect autophagy were tested for their abilities to enhance macrophage nanoformulated antiretroviral drug (ARV) depots and its slow release. METHODS: These agents included URMC-099, rapamycin, metformin, desmethylclomipramine, 2-hydroxy-ß-cyclodextrin (HBC) and clonidine. Each was administered with nanoformulated atazanavir (ATV) nanoparticles to human monocyte-derived macrophages. ARV retention, antiretroviral activity and nanocrystal autophagosomal formation were evaluated. RESULTS: URMC-099, HBC and clonidine retained ATV. HBC, URMC-099 and rapamycin improved intracellular ATV retention. URMC-099 proved superior among the group in affecting antiretroviral activities. CONCLUSION: Autophagy inducing agents, notably URMC-099, facilitate nanoformulated ARV depots and lead to sustained release and improved antiretroviral responses. As such, they may be considered for development as part of long acting antiretroviral treatment regimens.

Autophagy facilitates macrophage depots of sustained-release nanoformulated antiretroviral drugs.

Long-acting anti-HIV products can substantively change the standard of care for patients with HIV/AIDS. To this end, hydrophobic antiretroviral drugs (ARVs) were recently developed for parenteral administration at monthly or longer intervals. While shorter-acting hydrophilic drugs can be made into nanocarrier-encased prodrugs, the nanocarrier encasement must be boosted to establish long-acting ARV depots. The mixed-lineage kinase 3 (MLK-3) inhibitor URMC-099 provides this function by affecting autophagy. Here, we have shown that URMC-099 facilitates ARV sequestration and its antiretroviral responses by promoting the nuclear translocation of the transcription factor EB (TFEB). In monocyte-derived macrophages, URMC-099 induction of autophagy led to retention of nanoparticles containing the antiretroviral protease inhibitor atazanavir. These nanoparticles were localized within macrophage autophagosomes, leading to a 4-fold enhancement of mitochondrial and cell vitality. In rodents, URMC-099 activation of autophagy led to 50-fold increases in the plasma drug concentration of the viral integrase inhibitor dolutegravir. These data paralleled URMC-099-mediated induction of autophagy and the previously reported antiretroviral responses in HIV-1-infected humanized mice. We conclude that pharmacologic induction of autophagy provides a means to extend the action of a long-acting, slow, effective release of antiretroviral therapy.

Chronic lung infection by Pseudomonas aeruginosa biofilm is cured by L-Methionine in combination with antibiotic therapy.

Bacterial biofilms are associated with 80-90% of infections. Within the biofilm, bacteria are refractile to antibiotics, requiring concentrations >1,000 times the minimum inhibitory concentration. Proteins, carbohydrates and DNA are the major components of biofilm matrix. Pseudomonas aeruginosa (PA) biofilms, which are majorly associated with chronic lung infection, contain extracellular DNA (eDNA) as a major component. Herein, we report for the first time that L-Methionine (L-Met) at 0.5 µM inhibits Pseudomonas aeruginosa (PA) biofilm formation and disassembles established PA biofilm by inducing DNase expression. Four DNase genes (sbcB, endA, eddB and recJ) were highly up-regulated upon L-Met treatment along with increased DNase activity in the culture supernatant. Since eDNA plays a major role in establishing and maintaining the PA biofilm, DNase activity is effective in disrupting the biofilm. Upon treatment with L-Met, the otherwise recalcitrant PA biofilm now shows susceptibility to ciprofloxacin. This was reflected in vivo, in the murine chronic PA lung infection model. Mice treated with L-Met responded better to antibiotic treatment, leading to enhanced survival as compared to mice treated with ciprofloxacin alone. These results clearly demonstrate that L-Met can be used along with antibiotic as an effective therapeutic against chronic PA biofilm infection.

Successful treatment of biofilm infections using shock waves combined with antibiotic therapy.

Many bacteria secrete a highly hydrated framework of extracellular polymer matrix on suitable substrates and embed within the matrix to form a biofilm. Bacterial biofilms are observed on many medical devices, endocarditis, periodontitis and lung infections in cystic fibrosis patients. Bacteria in biofilm are protected from antibiotics and >1,000 times of the minimum inhibitory concentration may be required to treat biofilm infections. Here, we demonstrated that shock waves could be used to remove Salmonella, Pseudomonas and Staphylococcus biofilms in urinary catheters. The studies were extended to a Pseudomonas chronic pneumonia lung infection and Staphylococcus skin suture infection model in mice. The biofilm infections in mice, treated with shock waves became susceptible to antibiotics, unlike untreated biofilms. Mice exposed to shock waves responded to ciprofloxacin treatment, while ciprofloxacin alone was ineffective in treating the infection. These results demonstrate for the first time that, shock waves, combined with antibiotic treatment can be used to treat biofilm infection on medical devices as well as in situ infections.

Biocides--resistance, cross-resistance mechanisms and assessment.

IMPORTANCE OF THE FIELD: Antibiotic resistance in bacterial pathogens has increased worldwide leading to treatment failures. Concerns have been raised about the use of biocides as a contributing factor to the risk of antimicrobial resistance (AMR) development. In vitro studies demonstrating increase in resistance have often been cited as evidence for increased risks. It is therefore important to understand the mechanisms of resistance employed by bacteria toward biocides used in consumer products and their potential to impart cross-resistance to therapeutic antibiotics. AREAS COVERED: In this review, the mechanisms of resistance and cross-resistance reported in the literature toward biocides commonly used in consumer products are summarized. The physiological and molecular techniques used in describing and examining these mechanisms are reviewed and application of these techniques for systematic assessment of biocides for their potential to develop resistance and/or cross-resistance is discussed. EXPERT OPINION: The guidelines in the usage of biocides in household or industrial purpose should be monitored and regulated to avoid the emergence of any MDR strains. The genetic and molecular methods to monitor the resistance development to biocides should be developed and included in preclinical and clinical studies.

Salmonella enterica serovars Typhimurium and Typhi as model organisms: revealing paradigm of host-pathogen interactions.

The lifestyle of intracellular pathogens has always questioned the skill of a microbiologist in the context of finding the permanent cure to the diseases caused by them. The best tool utilized by these pathogens is their ability to reside inside the host cell, which enables them to easily bypass the humoral immunity of the host, such as the complement system. They further escape from the intracellular immunity, such as lysosome and inflammasome, mostly by forming a protective vacuole-bound niche derived from the host itself. Some of the most dreadful diseases are caused by these vacuolar pathogens, for example, tuberculosis by Mycobacterium or typhoid fever by Salmonella. To deal with such successful pathogens therapeutically, the knowledge of a host-pathogen interaction system becomes primarily essential, which further depends on the use of a model system. A well characterized pathogen, namely Salmonella, suits the role of a model for this purpose, which can infect a wide array of hosts causing a variety of diseases. This review focuses on various such aspects of research on Salmonella which are useful for studying the pathogenesis of other intracellular pathogens.

Acidic pH induced STM1485 gene is essential for intracellular replication of Salmonella.

During the course of infection, Salmonella has to face several potentially lethal environmental conditions, one such being acidic pH. The ability to sense and respond to the acidic pH is crucial for the survival and replication of Salmonella. The physiological role of one gene (STM1485) involved in this response, which is upregulated inside the host cells (by 90- to 113-fold) is functionally characterized in Salmonella pathogenesis. In vitro, the ΔSTM1485 neither exhibited any growth defect at pH 4.5 nor any difference in the acid tolerance response. The ΔSTM1485 was compromised in its capacity to proliferate inside the host cells and complementation with STM1485 gene restored its virulence. We further demonstrate that the surface translocation of Salmonella pathogenicity island-2 (SPI-2) encoded translocon proteins, SseB and SseD were reduced in the ΔSTM1485. The increase in co-localization of this mutant with lysosomes was also observed. In addition, the ΔSTM1485 displayed significantly reduced competitive indices (CI) in spleen, liver and mesenteric lymph nodes in murine typhoid model when infected by intra-gastric route. Based on these results, we conclude that the acidic pH induced STM1485 gene is essential for intracellular replication of Salmonella.

Multifaceted roles of curcumin: two sides of a coin!

INTRODUCTION: Curcumin has been a front-line topic of mainstream scientific research for a variety of diseases from cancer to Alzheimer's to infectious diseases. Curcumin suppresses the type 1 immune response, which might lead to alleviation of type 1 immune response disorders. However, the inhibition of type 1 immune response might invite infections with opportunistic pathogens. Considering its low bioavailability, several curcumin derivatives have been designed to improve its functionality. AREAS COVERED: This is a consolidated review which aims to compare and contrast diverse aspects of curcumin in variety of diseases. The intricate underlying mechanisms and the functional determinants of curcumin are discussed. EXPERT OPINION: Curcumin being considered as a spicy panacea, is not a remedy for all diseases. However, its ability to act differentially as an anti-oxidant or pro-oxidant akin to that of a double-edged sword/friend turning foe can be either beneficial or harmful for the host. It exhibits anti-oxidant properties at concentrations achievable in the body, making the host vulnerable to infections due to the suppression of innate immune responses. With the increase in knowledge of its functional groups, production of analogues of curcumin is underway to enhance its bioavailability and hence its therapeutic potency.