Gallium nanoparticles facilitate phagosome maturation and inhibit growth of virulent Mycobacterium tuberculosis in macrophages

Metallic Gallium Droplets Exhibit Poor Antibacterial Properties

The rise of antibiotic resistance in pathogenic bacteria requires new therapeutics to be developed. Several metallic nanoparticles such as those made from silver, copper, and zinc have shown significant antibacterial activity, in part due to metal ion leaching. Ga3+ containing compounds have also been shown to have antibacterial properties. Accordingly, it is estimated that metallic Ga droplets may be antibacterial, and some studies to date have confirmed this. Here, multiple concentrations of Ga droplets were tested against the antibiotic resistant Gram-positive bacteria methicillin-resistantStaphylococcus aureus (MRSA) and the Gram-negative bacteria Pseudomonas aeruginosa (P. aeruginosa) Despite a high concentration (2 mg/mL), Ga droplets had only modest antibacterial activity against both bacteria after 24 h of interaction. Finally, we demonstrated that Ga droplets were easily functionalized through a galvanic replacement reaction to develop antibacterial particles with copper and silver demonstrating a total detectable reduction of MRSA and >96% reduction ofP. aeruginosa. Altogether, these results contradict previous literature and show that Ga droplets demonstrate no antibacterial activity at concentrations comparable to those of conventional antibiotics and well-established antibacterial nanomaterials and only modest antibacterial activity at very high concentrations. However, we demonstrate that their antibacterial activity can be easily enhanced by functionalization.

Investigating Novel IspE Inhibitors of the MEP Pathway in Mycobacterium

In a recent effort to mitigate harm from human pathogens, many biosynthetic pathways have been extensively evaluated for their ability to inhibit pathogen growth and to determine drug targets. One of the important products/targets of such pathways is isopentenyl diphosphate. Isopentenyl diphosphate is the universal precursor of isoprenoids, which are essential for the normal functioning of microorganisms. In general, two biosynthetic pathways lead to the formation of isopentenyl diphosphate: (1) the mevalonate pathway in animals; and (2) the non-mevalonate or methylerythritol phosphate (MEP) in many bacteria, and some protozoa and plants. Because the MEP pathway is not found in mammalian cells, it is considered an attractive target for the development of antimicrobials against a variety of human pathogens, including Mycobacterium tuberculosis (M.tb). In the MEP pathway, 4-diphosphocytidyl-2-c-methyl-d-erythritol kinase (IspE) phosphorylates 4-diphosphocytidyl-2-C-methyl-D-erythritol (CDPME) to form 4-diphosphocytidyl-2-C-methyl-D-erythritol 2-phosphate (CDPME2P). A virtual high-throughput screening against 15 million compounds was carried out by docking IspE protein. We identified an active heterotricyclic compound which showed enzymatic activity; namely, IC50 of 6 µg/mL against M.tb IspE and a MIC of 12 µg/mL against M.tb (H37Rv). Hence, we designed and synthesized similar new heterotricyclic compounds and tested them against mycobacterium, observing a MIC of 5 µg/mL against M. avium. This study will provide the critical insight necessary for developing novel antimicrobials that target the MEP pathways in pathogens.

Micro-nanoemulsion and nanoparticle-assisted drug delivery against drug-resistant tuberculosis: recent developments

Tuberculosis (TB) is a major global health problem and the second most prevalent infectious killer after COVID-19. It is caused by Mycobacterium tuberculosis (Mtb) and has become increasingly challenging to treat due to drug resistance. The World Health Organization declared TB a global health emergency in 1993. Drug resistance in TB is driven by mutations in the bacterial genome that can be influenced by prolonged drug exposure and poor patient adherence. The development of drug-resistant forms of TB, such as multidrug resistant, extensively drug resistant, and totally drug resistant, poses significant therapeutic challenges. Researchers are exploring new drugs and novel drug delivery systems, such as nanotechnology-based therapies, to combat drug resistance. Nanodrug delivery offers targeted and precise drug delivery, improves treatment efficacy, and reduces adverse effects. Along with nanoscale drug delivery, a new generation of antibiotics with potent therapeutic efficacy, drug repurposing, and new treatment regimens (combinations) that can tackle the problem of drug resistance in a shorter duration could be promising therapies in clinical settings. However, the clinical translation of nanomedicines faces challenges such as safety, large-scale production, regulatory frameworks, and intellectual property issues. In this review, we present the current status, most recent findings, challenges, and limiting barriers to the use of emulsions and nanoparticles against drug-resistant TB.

Combination Therapy with Gallium Protoporphyrin and Gallium Nitrate Exhibits Enhanced Antimicrobial Activity In Vitro and In Vivo against Methicillin-Resistant Staphylococcus aureus

There is a major need for the development of new therapeutics to combat antibiotic-resistant Staphylococcus aureus. Recently, gallium (Ga)-based complexes have shown promising antimicrobial effects against various bacteria, including multidrug-resistant organisms, by targeting multiple heme/iron-dependent metabolic pathways. Among these, Ga protoporphyrin (GaPP) inhibits bacterial growth by targeting heme pathways, including aerobic respiration. Ga(NO3)3, an iron mimetic, disrupts elemental iron pathways. Here, we demonstrate the enhanced antimicrobial activity of the combination of GaPP and Ga(NO3)3 against methicillin-resistant S. aureus (MRSA) under iron-limited conditions, including small colony variants (SCV). This therapy demonstrated significant antimicrobial activity without inducing slow-growing SCV. We also observed that the combination of GaPP and Ga(NO3)3 inhibited the MRSA catalase but not above that seen with Ga(NO3)3 alone. Neither GaPP nor Ga(NO3)3 alone or their combination inhibited the dominant superoxide dismutase expressed (SodA) under the iron-limited conditions examined. Intranasal administration of the combination of the two compounds improved drug biodistribution in the lungs compared to intraperitoneal administration. In a murine MRSA lung infection model, we observed a significant increase in survival and decrease in MRSA lung CFUs in mice that received combination therapy with intranasal GaPP and Ga(NO3)3 compared to untreated control or mice receiving GaPP or Ga(NO3)3 alone. No drug-related toxicity was observed as assessed histologically in the spleen, lung, nasal cavity, and kidney for both single and repeated doses of 10 mg Ga /Kg of mice over 13 days. Our results strongly suggest that GaPP and Ga(NO3)3 in combination have excellent synergism and potential to be developed as a novel therapy for infections with S. aureus.

Current Therapeutic Delivery Approaches Using Nanocarriers for the Treatment of Tuberculosis Disease

Tuberculosis is a major health issue globally and a leading cause of death due to the infective microorganism Mycobacterium tuberculosis. Treatment of drug resistance tuberculosis requires longer treatment with multiple daily doses of drugs. Unfortunately, these drugs are often associated with poor patient compliance. In this situation, a need has been felt for the less toxic, shorter, and more effective treatment of the infected tuberculosis patients. Current research to develop novel anti-tubercular drugs shows hope for better management of the disease. Research on drug targeting and precise delivery of the old anti-tubercular drugs with the help of nanotechnology is promising for effective treatment. This review has discussed the status currently available treatments for tuberculosis patients infected with Mycobacterium alone or in comorbid conditions like diabetes, HIV and cancer. This review also highlighted the challenges in the current treatment and research on the novel anti-tubercular drugs to prevent multi-drug-resistant tuberculosis. It presents the research highlights on the targeted delivery of anti-tubercular drugs using different nanocarriers for preventing multi-drug resistant tuberculosis. Report has shown the importance and development of the research on nanocarriers mediated anti-tubercular delivery of the drugs to overcome the current challenges in tuberculosis treatment.

A Current Perspective on the Potential of Nanomedicine for Anti-Tuberculosis Therapy

Tuberculosis (TB) is one of the ten infectious diseases that cause the highest amount of human mortality and morbidity. This infection, which is caused by a single pathogen, Mycobacterium tuberculosis, kills over a million people every year. There is an emerging problem of antimicrobial resistance in TB that needs urgent treatment and management. Tuberculosis treatment is complicated by its complex drug regimen, its lengthy duration and the serious side-effects caused by the drugs required. There are a number of critical issues around drug delivery and subsequent intracellular bacterial clearance. Drugs have a short lifespan in systemic circulation, which limits their activity. Nanomedicine in TB is an emerging research area which offers the potential of effective drug delivery using nanoparticles and a reduction in drug doses and side-effects to improve patient compliance with the treatment and enhance their recovery. Here, we provide a minireview of anti-TB treatment, research progress on nanomedicine and the prospects for future applications in developing innovative therapies.

Combining Gallium Protoporphyrin and Gallium Nitrate Enhances In Vitro and In Vivo Efficacy against Pseudomonas aeruginosa: Role of Inhibition of Bacterial Antioxidant Enzymes and Resultant Increase in Cytotoxic Reactive Oxygen Species

Pseudomonas aeruginosa is a highly antibiotic-resistant opportunistic pathogenic bacteria that is responsible for thousands of deaths each year. Infections with P. aeruginosa disproportionately impact individuals with compromised immune systems as well as cystic fibrosis patients, where P. aeruginosa lung infection is a leading cause of morbidity and mortality. In previous work, we showed that a combination of gallium (Ga) nitrate and Ga protoporphyrin worked well in several bacterial infection models but its mechanism of action (MOA) is unknown. In the current work, we have investigated the MOA of Ga combination therapy in P. aeruginosa and its analysis in the in vivo model. In P. aeruginosa treated with Ga combination therapy, we saw a decrease in catalase and superoxide dismutase (SOD) activity, key antioxidant enzymes, which could correlate with a higher potential for oxidative stress. Consistent with this hypothesis, we found that, following combination therapy, P. aeruginosa demonstrated higher levels of reactive oxygen species, as measured using the redox-sensitive fluorescent probe, H2DCFDA. We also saw that the Ga combination therapy killed phagocytosed bacteria inside macrophages in vitro. The therapy with low dose was able to fully prevent mortality in a murine model of P. aeruginosa lung infection and also significantly reduced lung damage. These results support our previous data that Ga combination therapy acts synergistically to kill P. aeruginosa, and we now show that this may occur through increasing the organism's susceptibility to oxidative stress. Ga combination therapy also showed itself to be effective at treating infection in a murine pulmonary-infection model.

Gallium-Based Liquid Metal Materials for Antimicrobial Applications

The hazards caused by drug-resistant bacteria are rocketing along with the indiscriminate use of antibiotics. The development of new non-antibiotic antibacterial drugs is urgent. The excellent biocompatibility and diverse multifunctionalities of liquid metal have stimulated the studies of antibacterial application. Several gallium-based antimicrobial agents have been developed based on the mechanism that gallium (a type of liquid metal) ions disorder the normal metabolism of iron ions. Other emerging strategies, such as physical sterilization by directly using LM microparticles to destroy the biofilm of bacteria or thermal destruction via infrared laser irradiation, are gaining increasing attention. Different from traditional antibacterial agents of gallium compounds, the pronounced property of gallium-based liquid metal materials would bring innovation to the antibacterial field. Here, LM-based antimicrobial mechanisms, including iron metabolism disorder, production of reactive oxygen species, thermal injury, and mechanical destruction, are highlighted. Antimicrobial applications of LM-based materials are summarized and divided into five categories, including liquid metal motors, antibacterial fabrics, magnetic field-responsive microparticles, liquid metal films, and liquid metal polymer composites. In addition, future opportunities and challenges towards the development and application of LM-based antimicrobial materials are presented.

Recent Developments in Drug Delivery for Treatment of Tuberculosis by Targeting Macrophages

Tuberculosis (TB) is among the greatest public health and safety concerns in the 21st century, Mycobacterium tuberculosis, which causes TB, infects alveolar macrophages and uses these cells as one of its primary sites of replication. The current TB treatment regimen, which consist of chemotherapy involving a combination of 3-4 antimicrobials for a duration of 6-12 months, is marked with significant side effects, toxicity, and poor compliance. Targeted drug delivery offers a strategy that could overcome many of the problems of current TB treatment by specifically targeting infected macrophages. Recent advances in nanotechnology and material science have opened an avenue to explore drug carriers that actively and passively target macrophages. This approach can increase the drug penetration into macrophages by using ligands on the nanocarrier that interact with specific receptors for macrophages. This review encompasses the recent development of drug carriers specifically targeting macrophages actively and passively. Future directions and challenges associated with development of effective TB treatment is also discussed.

Advancement of Gallium and Gallium-Based Compounds as Antimicrobial Agents

With the abuse and misuse of antibiotics, antimicrobial resistance has become a challenging issue in the medical system. Iatrogenic and non-iatrogenic infections caused by multidrug-resistant (MDR) pathogens pose serious threats to global human life and health because the efficacy of traditional antibiotics has been greatly reduced and the resulting socio-economic burden has increased. It is important to find and develop non-antibiotic-dependent antibacterial strategies because the development of new antibiotics can hardly keep pace with the emergence of resistant bacteria. Gallium (III) is a multi-target antibacterial agent that has an excellent antibacterial activity, especially against MDR pathogens; thus, a gallium (III)-based treatment is expected to become a new antibacterial strategy. However, some limitations of gallium ions as antimicrobials still exist, including low bioavailability and explosive release. In recent years, with the development of nanomaterials and clathrates, the progress of manufacturing technology, and the emergence of synergistic antibacterial strategies, the antibacterial activities of gallium have greatly improved, and the scope of application in medical systems has expanded. This review summarizes the advancement of current optimization for these key factors. This review will enrich the knowledge about the efficiency and mechanism of various gallium-based antibacterial agents and provide strategies for the improvement of the antibacterial activity of gallium-based compounds.

Nanoparticulate β-Cyclodextrin with Gallium Tetraphenylporphyrin Demonstrates in Vitro and in Vivo Antimicrobial Efficacy against Mycobacteroides abscessus and Mycobacterium avium

The emergence of drug-resistant pathogens causes the greatest challenge for drug development research. Recently, gallium(III)-based compounds have received great attention as novel antimicrobial agents against drug-resistant pathogens. Here, we synthesized a new β-cyclodextrin Ga nanoparticle (CDGaTP) using Ga tetraphenylporphyrin (GaTP, a hemin analogue) and β-cyclodextrin. The newly synthesized nanoparticle was nontoxic and efficient at a single dose, showing sustained drug release for 15 days in vitro. CDGaTP's activity with transferrin or lactoferrin was tested, and synergism in activity was observed against nontuberculosis mycobacteria (NTM), Mycobacterium avium (M. avium), and Mycobacteroides abscessus. Human serum albumin (HSA) decreased the efficacy of both GaTP and CDGaTP in a concentration-dependent manner. The NTMs incubated with GaTP or CDGaTP significantly produced reactive oxygen species (ROS), indicating potential inhibition of antioxidant enzymes, such as catalase. The single-dose CDGaTP displayed a prolonged intracellular inhibitory activity in an in vitro macrophage infection model against both NTMs. In addition, CDGaTP, not GaTP, was effective in a murine lung M. avium infection model when delivered via intranasal administration. These results suggest that CDGaTP provides new opportunities for the development of gallium-porphyrin based antibiotics.

Cathepsin D-Managing the Delicate Balance

Lysosomal proteases play a crucial role in maintaining cell homeostasis. Human cathepsin D manages protein turnover degrading misfolded and aggregated proteins and favors apoptosis in the case of proteostasis disruption. However, when cathepsin D regulation is affected, it can contribute to numerous disorders. The down-regulation of human cathepsin D is associated with neurodegenerative disorders, such as neuronal ceroid lipofuscinosis. On the other hand, its excessive levels outside lysosomes and the cell membrane lead to tumor growth, migration, invasion and angiogenesis. Therefore, targeting cathepsin D could provide significant diagnostic benefits and new avenues of therapy. Herein, we provide a brief overview of cathepsin D structure, regulation, function, and its role in the progression of many diseases and the therapeutic potentialities of natural and synthetic inhibitors and activators of this protease.

M. M. de Almeida J, Pastoriza-Santos I, C. C. Coelho L. Advances in Plasmonic Sensing at the NIR-A Review

Surface plasmon resonance (SPR) and localized surface plasmon resonance (LSPR) are among the most common and powerful label-free refractive index-based biosensing techniques available nowadays. Focusing on LSPR sensors, their performance is highly dependent on the size, shape, and nature of the nanomaterial employed. Indeed, the tailoring of those parameters allows the development of LSPR sensors with a tunable wavelength range between the ultra-violet (UV) and near infra-red (NIR). Furthermore, dealing with LSPR along optical fiber technology, with their low attenuation coefficients at NIR, allow for the possibility to create ultra-sensitive and long-range sensing networks to be deployed in a variety of both biological and chemical sensors. This work provides a detailed review of the key science underpinning such systems as well as recent progress in the development of several LSPR-based biosensors in the NIR wavelengths, including an overview of the LSPR phenomena along recent developments in the field of nanomaterials and nanostructure development towards NIR sensing. The review ends with a consideration of key advances in terms of nanostructure characteristics for LSPR sensing and prospects for future research and advances in this field.

Pulling the Brakes on Fast and Furious Multiple Drug-Resistant (MDR) Bacteria

Life-threatening bacterial infections have been managed by antibiotics for years and have significantly improved the wellbeing and lifetime of humans. However, bacteria have always been one step ahead by inactivating the antimicrobial agent chemically or by producing certain enzymes. The alarming universal occurrence of multidrug-resistant (MDR) bacteria has compelled researchers to find alternative treatments for MDR infections. This is a menace where conventional chemotherapies are no longer promising, but several novel approaches could help. Our current review article discusses the novel approaches that can combat MDR bacteria: starting off with potential nanoparticles (NPs) that efficiently interact with microorganisms causing fatal changes in the morphology and structure of these cells; nanophotothermal therapy using inorganic NPs like AuNPs to destroy pathogenic bacterial cells; bacteriophage therapy against which bacteria develop less resistance; combination drugs that act on dissimilar targets in distinctive pathways; probiotics therapy by the secretion of antibacterial chemicals; blockage of quorum sensing signals stopping bacterial colonization, and vaccination against resistant bacterial strains along with virulence factors. All these techniques show us a promising future in the fight against MDR bacteria, which remains the greatest challenge in public health care.

Superior antibacterial activity of gallium based liquid metals due to Ga3+ induced intracellular ROS generation

Gallium metals demonstrate enhanced antibacterial activity compared to gallium nitrate with the same gallium ion concentration.

Approaches to treating tuberculosis by encapsulating metal ions and anti-mycobacterial drugs utilizing nano- and microparticle technologies

Tuberculosis (TB) is caused by a bacterial infection that affects a number of human organs, primarily the lungs, but also the liver, spleen, and spine, causing key symptoms of fever, fatigue, and persistent cough, and if not treated properly, can be fatal. Every year, 10 million individuals become ill with active TB resulting with a mortality approximating 1.5 million. Current treatment guidelines recommend oral administration of a combination of first-line anti-TB drugs for at least 6 months. While efficacious under optimum conditions, 'Directly Observed Therapy Short-course' (DOTS) is not without problems. The long treatment time and poor pharmacokinetics, alongside drug side effects lead to poor patient compliance and has accelerated the emergence of multi-drug resistant (MDR) organisms. All this, combined with the limited number of newly discovered TB drugs to treat MDR-TB and shorten standard therapy time, has highlighted the need for new targeted drug delivery systems. In this respect, there has been recent focus on micro- and nano-particle technologies to prepare organic or/and metal particles loaded with TB drugs to enhance their efficacy by targeted delivery via the inhaled route. In this review, we provide a brief overview of the current epidemiology of TB, and risk factors for progression of latent stage tuberculosis (LTBI) to the active TB. We identify current TB treatment regimens, newly discovered TB drugs, and identify studies that have used micro- or nano-particles technologies to design a reliable inhalation drug delivery system to treat TB more effectively.

The Role of Metallic Nanoparticles in Inhibition of Mycobacterium Tuberculosis and Enhances Phagosome Maturation into the Infected Macrophage

This review focuses on the role of gallium (Ga) nanoparticles (NPs) to enhance phagosome maturation into the Mycobacterium tuberculosis-infected macrophage and the role of magnetic iron NPs as nanocarriers of antituberculosis drugs. The literature shows that silver (Ag) and zinc oxide (ZnO) NPs with dimensions less than 10 nm can penetrate directly through the macrophage bilayer membrane. Ag NPs increase the permeability membrane by motiving the aggregation of proteins in the periplasmic space and forming nano-sized pores. ZnO NPs can interact with the membrane of M. tuberculosis, which leads to the formation of surface pores and the release of intracellular nucleotides. The colloidal Ag:ZnO mixture NPs with 1:1 ratio can eliminate M. tuberculosis and shows the lowest cytotoxicity effects on MCF-7 and THP-1 cell lines. Ag/ZnO nanocrystals are not able to kill M. tuberculosis alone ex-vivo. Hence, bimetallic gold (Au)/Ag NPs possessed high efficiency to inhibit M. tuberculosis in an ex-vivo THP-1 infection model. Co-delivery of mixed MeNPs into a polymeric carrier collaborated to selective uptake by macrophages through passive targeting, initial burst release of ions from the encapsulated metallic (Me) NPs, and eventually, reduction of MeNPs toxicity, and plays a pivotal role in increasing the antitubercular activity compared to use alone. In addition, Ga NPs can import drugs to the macrophage, inhibit M. tuberculosis growth, and reduce the inhibition of phagosome maturation. Magnetic encapsulated NPs exhibited good drug release properties and might be suitable as carriers of antituberculosis drugs.

Gallium Porphyrin and Gallium Nitrate Synergistically Inhibit Mycobacterial Species by Targeting Different Aspects of Iron/Heme Metabolism

There is an urgent need for new effective and safe antibiotics active against pathogenic mycobacterial species. Gallium (Ga) nitrate (Ga(NO₃)₃) and Ga porphyrin (GaPP) have each been shown to inhibit the growth of a variety of mycobacterial species. The Ga(III) ion derived from Ga(NO₃)₃ has the potential to disrupt the mycobacterial Fe(III) uptake mechanisms and utilization, including replacing iron (Fe) in the active site of enzymes, resulting in the disruption of function. Similarly, noniron metalloporphyrins such as heme mimetics, which can be transported across the bacterial membrane via heme-uptake pathways, would potentially block the acquisition of iron-containing heme and bind to heme-utilizing proteins, making them nonfunctional. Given that they likely act on different aspects of mycobacterial Fe metabolism, the efficacy of combining Ga(NO₃)₃ and GaPP was studied in vitro against Mycobacterium avium, Mycobacterium abscessus, and Mycobacterium tuberculosis (M. tb). The combination was then assessed in vivo in a murine pulmonary infection model of M. abscessus. We observed that Ga(NO₃)₃ in combination with GaPP exhibited synergistic inhibitory activity against the growth of M. avium, M. tb, and M. abscessus, being most active against M. abscessus. Activity assays indicated that Ga(NO₃)₃ and GaPP inhibited both catalase and aconitase at high concentrations. However, the combination showed a synergistic effect on the aconitase activity of M. abscessus. The Ga(NO₃)₃/GaPP combination via intranasal administration showed significant antimicrobial activity in mice infected with M. abscessus. M. abscessus CFU from the lungs of the Ga(NO₃)₃/GaPP-treated mice was significantly less compared to that of nontreated or single Ga(III)-treated mice. These findings suggest that combinations of different Ga(III) compounds can synergistically target multiple iron/heme-utilizing mycobacterial enzymes. The results support the potential of combination Ga therapy for development against mycobacterial pathogens.

Drug delivery to macrophages: a review of nano-therapeutics targeted approach for inflammatory disorders and cancer

INTRODUCTION

Macrophages are involved in the normal defense of the body; however, the varying phenotypes of macrophages and imbalance in their ratio lead to the impairment of immune response initiating the production of inflammation. As the role of macrophages in immunological disorders and their surface receptors modulation has already been manifested; hence, macrophages can be exploited to make them a viable candidate for targeted delivery, which was not possible with previously designed conventional therapies for the immune disorders.

AREAS COVERED

Nanotechnology is a promising, clear cut, efficient, and adequate approach for targeting macrophages. Literature addresses the receptors available for targeting and the novel small dimensional therapeutic delivery vehicles to target them along with a brief overview of the role of macrophages in these diseases. Furthermore, the patents based on this idea are also listed.

EXPERT OPINION

Targeted drug delivery to macrophages should take into consideration the plasticity of macrophages and their modulation over time in the diseases. A cost-effective scale-up method of development will further facilitate the clinical trials. Besides, the implementation of safety guidelines to target macrophages and the studies of long-term effects of targeted approaches in humans would highly encourage the clinical outcomes.

Metal-Peptide Complexes as Promising Antibiotics to Fight Emerging Drug Resistance: New Perspectives in Tuberculosis

In metal-peptide interactions, cations form stable complexes through bonds with coordinating groups as side chains of amino acids. These compounds, among other things, exert a wide variety of antimicrobial activities through structural changes of peptides upon metal binding and redox chemistry. They exhibit different mechanisms of action (MOA), including the modification of DNA/RNA, protein and cell wall synthesis, permeabilization and modulation of gradients of cellular membranes. Nowadays, the large increase in antibiotic resistance represents a crucial problem to limit progression at the pandemic level of the diseases that seemed nearly eradicated, such as tuberculosis (Tb). Mycobacterium tuberculosis (Mtb) is intrinsically resistant to many antibiotics due to chromosomal mutations which can lead to the onset of novel strains. Consequently, the maximum pharmaceutical effort should be focused on the development of new therapeutic agents and antimicrobial peptides can represent a valuable option as a copious source of potential bioactive compounds. The introduction of a metal center can improve chemical diversity and hence specificity and bioavailability while, in turn, the coordination to peptides of metal complexes can protect them and enhance their poor water solubility and air stability: the optimization of these parameters is strictly required for drug prioritization and to obtain potent inhibitors of Mtb infections with novel MOAs. Here, we present a panoramic review of the most recent findings in the field of metal complex-peptide conjugates and their delivery systems with the potential pharmaceutical application as novel antibiotics in Mtb infections.

Antimycobacterial Effect of Selenium Nanoparticles on Mycobacterium tuberculosis

Tuberculosis (TB) remains the leading cause of death from a single infection agent worldwide. In recent years, the occurrence of TB cases caused by drug-resistant strains has spread, and is expected to continue to grow. Therefore, the development of new alternative treatments to the use of antibiotics is highly important. In that sense, nanotechnology can play a very relevant role, due to the unique characteristics of nanoparticles. In fact, different types of nanoparticles have already been evaluated both as potential bactericides and as efficient drug delivery vehicles. In this work, the use of selenium nanoparticles (SeNPs) has been evaluated to inhibit the growth of two types of mycobacteria: Mycobacterium smegmatis (Msm) and Mycobacterium tuberculosis (Mtb). The results showed that SeNPs are able to inhibit the growth of both types of mycobacteria by damaging their cell envelope integrity. These results open a new opportunity for the use of this type of nanoparticles as antimycobacterial agents by themselves, or for the development of novel nanosystems that combine the action of these nanoparticles with other drugs.

Multi-functionalized nanocarriers targeting bacterial reservoirs to overcome challenges of multi drug-resistance

INTRODUCTION

Infectious diseases associated with intracellular bacteria such as Staphylococcus aureus, Salmonella typhimurium and Mycobacterium tuberculosis are important public health concern. Emergence of multi and extensively drug-resistant bacterial strains have made it even more obstinate to offset such infections. Bacteria residing within intracellular compartments provide additional barriers to effective treatment.

METHOD

Information provided in this review has been collected by accessing various electronic databases including Google scholar, Web of science, Scopus, and Nature index. Search was performed using keywords nanoparticles, intracellular targeting, multidrug resistance, Staphylococcus aureus; Salmonella typhimurium; Mycobacterium tuberculosis. Information gathered was categorized into three major sections as 'Intracellular targeting of Staphylococcus aureus, Intracellular targeting of Salmonella typhimurium and Intracellular targeting of Mycobacterium tuberculosis' using variety of nanocarrier systems.

RESULTS

Conventional management for infectious diseases typically comprises of long-term treatment with a combination of antibiotics, which may lead to side effects and decreased patient compliance. A wide range of multi-functionalized nanocarrier systems have been studied for delivery of drugs within cellular compartments where bacteria including Staphylococcus aureus, Salmonella typhimurium and Mycobacterium tuberculosis reside. Such carrier systems along with targeted delivery have been utilized for sustained and controlled delivery of drugs. These strategies have been found useful in overcoming the drawbacks of conventional treatments including multi-drug resistance.

CONCLUSION

Development of multi-functional nanocargoes encapsulating antibiotics that are proficient in targeting and releasing drug into infected reservoirs seems to be a promising strategy to circumvent the challenge of multidrug resistance. Graphical abstract.

Nano-antimicrobials: A New Paradigm for Combating Mycobacterial Resistance

BACKGROUND

Mycobacterium group contains several pathogenic bacteria including M. tuberculosis where the emergence of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) is alarming for human and animal health around the world. The condition has further aggravated due to the speed of discovery of the newer drugs has been outpaced by the rate of resistance developed in microorganisms, thus requiring alternative combat strategies. For this purpose, nano-antimicrobials have emerged as a potential option.

OBJECTIVE

The current review is focused on providing a detailed account of nanocarriers like liposome, micelles, dendrimers, solid lipid NPs, niosomes, polymeric nanoparticles, nano-suspensions, nano-emulsion, mesoporous silica and alginate-based drug delivery systems along with the recent updates on developments regarding nanoparticle-based therapeutics, vaccines and diagnostic methods developed or under pipeline with their potential benefits and limitations to combat mycobacterial diseases for their successful eradication from the world in future.

RESULTS

Distinct morphology and the underlying mechanism of pathogenesis and resistance development in this group of organisms urge improved and novel methods for the early and efficient diagnosis, treatment and vaccination to eradicate the disease. Recent developments in nanotechnology have the potential to meet both the aspects: nano-materials are proven components of several efficient targeted drug delivery systems and the typical physicochemical properties of several nano-formulations have shown to possess distinct bacteriocidal properties. Along with the therapeutic aspects, nano-vaccines and theranostic applications of nano-formulations have grown in popularity in recent times as an effective alternative means to combat different microbial superbugs.

CONCLUSION

Nanomedicine holds a bright prospect to perform a key role in global tuberculosis elimination program.

Dual Inhibition of Klebsiella pneumoniae and Pseudomonas aeruginosa Iron Metabolism Using Gallium Porphyrin and Gallium Nitrate

Iron- and heme-uptake pathways and metabolism are promising targets for the development of new antimicrobial agents, as their disruption would lead to nutritional iron starvation and inhibition of bacterial growth. Salts of gallium(III) (Ga), an iron mimetic metal, disrupt iron-dependent biological processes by binding iron-utilizing proteins and competing with iron for uptake by bacterial siderophore-mediated iron uptake systems. Ga porphyrins, heme mimetic complexes, disrupt heme-utilizing hemoproteins. Because Ga(NO₃)₃ and Ga porphyrin disrupt different pathways of bacterial ion acquisition and utilization, we hypothesized that if used in combination, they would result in enhanced antimicrobial activity. Antimicrobial activity of Ga porphyrins (Ga protoporphyrin, GaPP, or Ga mesoporphyrin, GaMP) alone and in combination with Ga(NO₃)₃ were evaluated against Pseudomonas aeruginosa, Klebsiella pneumoniae, Acinetobacter baumannii, and methicillin-resistant Staphylococcus aureus (MRSA) under iron-limited conditions. The Ga porphyrin/Ga(NO₃)₃ combination demonstrated substantial synergism against K. pneumoniae, P. aeruginosa, and MRSA. Time-kill assays revealed that the synergistic combination of GaPP/Ga(NO₃)₃ was bacteriostatic against K. pneumoniae and MRSA and bactericidal against P. aeruginosa. The GaPP/Ga(NO₃)₃ combination significantly disrupted K. pneumoniae and P. aeruginosa biofilms on plasma-coated surfaces and increased the survival of Caenorhabditis elegans infected with K. pneumoniae or P. aeruginosa. When assessing the antibacterial activity of the Ga(III)/antibiotic combinations, GaPP/colistin and Ga(NO₃)₃/colistin combinations also showed synergistic activity against K. pneumoniae and P. aeruginosa. Our results demonstrate that GaPP and Ga(NO₃)₃ have significant synergistic effects against several important human bacterial pathogens through dual inhibition of iron and heme metabolism.

Treatment of Virulent Mycobacterium tuberculosis and HIV Coinfected Macrophages with Gallium Nanoparticles Inhibits Pathogen Growth and Modulates Macrophage Cytokine Production

GaNP interrupts iron-mediated enzymatic reactions, leading to growth inhibition of virulent HIV-M. tuberculosis coinfection in macrophages, and also modulates release of cytokines that may contribute to HIV-TB pathogenesis. Macrophage-targeting GaNP are a promising therapeutic approach to provide sustained antimicrobial activity against HIV-M. tuberculosis coinfection.

Tuberculosis (TB), caused by Mycobacterium tuberculosis, remains a global threat. The course of TB is negatively impacted by coexistent infection with human immunodeficiency virus type 1 (HIV). Macrophage infection with these pathogens modulates their production of pro- and anti-inflammatory cytokines, which could play a crucial role in pathogenesis. Despite the important role of macrophages in containing infection by a variety of microbes, both HIV and M. tuberculosis infect and replicate within these cells during the course of HIV-M. tuberculosis coinfection. Both M. tuberculosis and HIV require iron for growth and replication. We have previously shown that gallium encapsulated in nanoparticles, which interferes with cellular iron acquisition and utilization, inhibited the growth of HIV and an attenuated strain of M. tuberculosis within human monocyte-derived macrophages (MDMs) in vitro. Whether this was true for a fully virulent strain of M. tuberculosis and whether gallium treatment modulates cytokine production by HIV- and/or M. tuberculosis-infected macrophages have not been previously addressed. Therefore, coinfection of MDMs with HIV and a virulent M. tuberculosis strain (H37Rv) was studied in the presence of different gallium nanoparticles (GaNP). All GaNP were readily internalized by the MDMs, which provided sustained drug (gallium) release for 15 days. This led to significant growth inhibition of both HIV and M. tuberculosis within MDMs for up to 15 days after loading of the cells with all GaNP tested in our study. Cytokine analysis showed that HIV-M. tuberculosis coinfected macrophages secreted large amounts of interleukin 6 (IL-6) and IL-8 and smaller amounts of IL-1β, IL-4, and tumor necrosis factor alpha (TNF-α) cytokines. However, all GaNP were able to regulate the release of cytokines significantly. GaNP interrupts iron-mediated enzymatic reactions, leading to growth inhibition of HIV-M. tuberculosis coinfection in macrophages, and also modulates release of cytokines that may contribute to HIV-TB pathogenesis.

IMPORTANCE GaNP interrupts iron-mediated enzymatic reactions, leading to growth inhibition of virulent HIV-M. tuberculosis coinfection in macrophages, and also modulates release of cytokines that may contribute to HIV-TB pathogenesis. Macrophage-targeting GaNP are a promising therapeutic approach to provide sustained antimicrobial activity against HIV-M. tuberculosis coinfection.

Brief update on endocytosis of nanomedicines

The complexity of nanoscale interactions between biomaterials and cells has limited the realization of the ultimate vision of nanotechnology in diagnostics and therapeutics. As such, significant effort has been devoted to advancing our understanding of the biophysical interactions of the myriad nanoparticles. Endocytosis of nanomedicine has drawn tremendous interest in the last decade. Here, we highlight the ever-present barriers to efficient intracellular delivery of nanoparticles as well as the current advances and strategies deployed to breach these barriers. We also introduce new barriers that have been largely overlooked such as the glycocalyx and macromolecular crowding. Additionally, we draw attention to the potential complications arising from the disruption of the newly discovered functions of the lysosomes. Novel strategies of exploiting the inherent intracellular defects in disease states to enhance delivery and the use of exosomes for bioanalytics and drug delivery are explored. Furthermore, we discuss the advances in imaging techniques like electron microscopy, super resolution fluorescence microscopy, and single particle tracking which have been instrumental in our growing understanding of intracellular pathways and nanoparticle trafficking. Finally, we advocate for the push towards more intravital analysis of nanoparticle transport phenomena using the multitude of techniques available to us. Unraveling the underlying mechanisms governing the cellular barriers to delivery and biological interactions of nanoparticles will guide the innovations capable of breaching these barriers.

Iron/Heme Metabolism-Targeted Gallium(III) Nanoparticles Are Active against Extracellular and Intracellular Pseudomonas aeruginosa and Acinetobacter baumannii

Iron/heme acquisition systems are critical for microorganisms to acquire iron from the human host, where iron sources are limited due to the nutritional immune system and insolubility of the ferric form of iron. Prior work has shown that a variety of gallium compounds can interfere with bacterial iron acquisition. This study explored the intra- and extracellular antimicrobial activities of gallium protoporphyrin (GaPP), gallium mesoporphyrin (GaMP), and nanoparticles encapsulating GaPP or GaMP against the Gram-negative pathogens Pseudomonas aeruginosa and Acinetobacter baumannii, including clinical isolates. All P. aeruginosa and A. baumannii isolates were susceptible to GaPP and GaMP, with MICs ranging from 0.5 to ∼32 μg/ml in iron-depleted medium. Significant intra- and extracellular growth inhibition was observed against P. aeruginosa cultured in macrophages at a gallium concentration of 3.3 μg/ml (5 μM) of all Ga(III) compounds, including nanoparticles. Nanoparticle formulations showed prolonged activity against both P. aeruginosa and A. baumannii in previously infected macrophages. When the macrophages were loaded with the nanoparticles 3 days prior to infection, there was a 5-fold decrease in growth of P. aeruginosa in the presence of single emulsion F127 copolymer nanoparticles encapsulating GaMP (eFGaMP). In addition, all Ga(III) porphyrins and nanoparticles showed significant intracellular and antibiofilm activity against both pathogens, with the nanoparticles exhibiting intracellular activity for 3 days. Ga nanoparticles also increased the survival rate of Caenorhabditis elegans nematodes infected by P. aeruginosa and A. baumannii Our results demonstrate that Ga nanoparticles have prolonged in vitro and in vivo activities against both P. aeruginosa and A. baumannii, including disruption of their biofilms.

Tunneling Nanotubular Expressways for Ultrafast and Accurate M1 Macrophage Delivery of Anticancer Drugs to Metastatic Ovarian Carcinoma

It is extremely difficult for cancer chemotherapy to control the peritoneal metastasis of advanced ovarian carcinoma given its inability to target disseminated tumors and the severe toxic side effects on healthy organs. Here, we report antitumor M1 macrophages developed as live-cell carriers that deliver anticancer drugs for the treatment of the metastatic ovarian carcinoma. Engineered doxorubicin-loaded M1 macrophages (M1-Dox) significantly enhanced tumor tropism by upregulation of CCR2 and CCR4 compared with their parent cells. Meanwhile, M1-Dox inhibited doxorubicin-induced tumor invasion, whereas commercial Lipo-Dox did not limit these side effects. Importantly, our data uncovered a drug delivery mechanism by which M1-Dox transferred drug cargoes into tumor cells  via a tunneling nanotube pathway. The tunneling nanotube network acted as a transportation expressway for ultrafast drug delivery of M1-Dox, leading to efficient ovarian carcinoma cell death. Furthermore, genetic, pharmacological, and physical perturbations of these tunneling nanotubes obviously decreased drug transfer of M1-Dox, which further validated the evident correlation between drug delivery of M1-Dox and tunneling nanotubes. Finally, in peritoneal metastatic ovarian carcinoma-burdened mice, M1-Dox specifically penetrated into and accumulated deep within disseminated neoplastic lesions compared with commercial Lipo-Dox, resulting in reducing metastatic tumors to a nearly undetectable level and significantly increasing overall survival. Overall, the strategy of engineered macrophages for ultrafast and accurate drug delivery via the tunneling nanotubular expressway potentially revolutionizes the treatment of metastatic ovarian carcinoma.

In vitro Pharmacokinetic Cell Culture System that Simulates Physiologic Drug and Nanoparticle Exposure to Macrophages

PURPOSE

An in vitro dynamic pharmacokinetic (PK) cell culture system was developed to more precisely simulate physiologic nanoparticle/drug exposure.

METHODS

A dynamic PK cell culture system was developed to more closely reflect physiologic nanoparticle/drug concentrations that are changing with time. Macrophages were cultured in standard static and PK cell culture systems with rifampin (RIF; 5 μg/ml) or β-glucan, chitosan coated, poly(lactic-co-glycolic) acid (GLU-CS-PLGA) nanoparticles (RIF equivalent 5 μg/ml) for 6 h. Intracellular RIF concentrations were measured by UPLC/MS. Antimicrobial activity against M. smegmatis was tested in both PK and static systems.

RESULTS

The dynamic PK cell culture system mimics a one-compartment elimination pharmacokinetic profile to properly mimic in vivo extracellular exposure. GLU-CS-PLGA nanoparticles increased intracellular RIF concentration by 37% compared to free drug in the dynamic cell culture system. GLU-CS-PLGA nanoparticles decreased M. smegmatis colony forming units compared to free drug in the dynamic cell culture system.

CONCLUSIONS

The PK cell culture system developed herein enables more precise simulation of human PK exposure (i.e., drug dosing and drug elimination curves) based on previously obtained PK parameters.

Peptidyl-prolyl isomerase-B is involved in Mycobacterium tuberculosis biofilm formation and a generic target for drug repurposing-based intervention

Tuberculosis (TB), a disease caused by Mycobacterium tuberculosis (M.tb), takes one human life every 15 s globally. Disease relapse occurs due to incomplete clearance of the pathogen and reactivation of the antibiotic tolerant bacilli. M.tb, like other bacterial pathogens, creates an ecosystem of biofilm formed by several proteins including the cyclophilins. We show that the M.tb cyclophilin peptidyl-prolyl isomerase (PpiB), an essential gene, is involved in biofilm formation and tolerance to anti-mycobacterial drugs. We predicted interaction between PpiB and US FDA approved drugs (cyclosporine-A and acarbose) by in-silico docking studies and this was confirmed by surface plasmon resonance (SPR) spectroscopy. While all these drugs inhibited growth of Mycobacterium smegmatis (M.smegmatis) when cultured in vitro, acarbose and cyclosporine-A showed bacteriostatic effect while gallium nanoparticle (GaNP) exhibited bactericidal effect. Cyclosporine-A and GaNP additionally disrupted M.tb H₃₇Rv biofilm formation. Co-culturing M.tb in their presence resulted in significant (2–4 fold) decrease in dosage of anti-tubercular drugs- isoniazid and ethambutol. Comparison of the cyclosporine-A and acarbose binding sites in PpiB homologues of other biofilm forming infectious pathogens revealed that these have largely remained unaltered across bacterial species. Targeting bacterial biofilms could be a generic strategy for intervention against bacterial pathogens.

Tuberculosis, caused by Mycobacterium tuberculosis, is the leading cause of death due to a single infectious agent. New therapeutic options are needed, and repurposing clinically approved drugs to destroy biofilms is an attractive approach, as these microbial communities are often less susceptible to antibiotics. A team lead by Seyed Hasnain at the Indian Institute of Technology Delhi identified an enzyme, PpiB, from M. tuberculosis that promoted biofilm formation and showed that PpiB interacts with several drugs that are currently used to treat diabetes, immunological diseases and cancer. These drugs destabilise M. tuberculosis biofilms in culture and enhanced the potency of two current anti-tuberculosis antibiotics. Future work is needed to test these medications against tuberculosis in humans, but given PpiB is found in different bacteria, there may be broader promise of using these repurposed drugs to combat other infections.

Nano-Strategies to Fight Multidrug Resistant Bacteria-"A Battle of the Titans"

Infectious diseases remain one of the leading causes of morbidity and mortality worldwide. The WHO and CDC have expressed serious concern regarding the continued increase in the development of multidrug resistance among bacteria. Therefore, the antibiotic resistance crisis is one of the most pressing issues in global public health. Associated with the rise in antibiotic resistance is the lack of new antimicrobials. This has triggered initiatives worldwide to develop novel and more effective antimicrobial compounds as well as to develop novel delivery and targeting strategies. Bacteria have developed many ways by which they become resistant to antimicrobials. Among those are enzyme inactivation, decreased cell permeability, target protection, target overproduction, altered target site/enzyme, increased efflux due to over-expression of efflux pumps, among others. Other more complex phenotypes, such as biofilm formation and quorum sensing do not appear as a result of the exposure of bacteria to antibiotics although, it is known that biofilm formation can be induced by antibiotics. These phenotypes are related to tolerance to antibiotics in bacteria. Different strategies, such as the use of nanostructured materials, are being developed to overcome these and other types of resistance. Nanostructured materials can be used to convey antimicrobials, to assist in the delivery of novel drugs or ultimately, possess antimicrobial activity by themselves. Additionally, nanoparticles (e.g., metallic, organic, carbon nanotubes, etc.) may circumvent drug resistance mechanisms in bacteria and, associated with their antimicrobial potential, inhibit biofilm formation or other important processes. Other strategies, including the combined use of plant-based antimicrobials and nanoparticles to overcome toxicity issues, are also being investigated. Coupling nanoparticles and natural-based antimicrobials (or other repurposed compounds) to inhibit the activity of bacterial efflux pumps; formation of biofilms; interference of quorum sensing; and possibly plasmid curing, are just some of the strategies to combat multidrug resistant bacteria. However, the use of nanoparticles still presents a challenge to therapy and much more research is needed in order to overcome this. In this review, we will summarize the current research on nanoparticles and other nanomaterials and how these are or can be applied in the future to fight multidrug resistant bacteria.

Fluorescence & bioluminescence in the quest for imaging, probing & analysis of mycobacterial infections

Mycobacterioses represent a global health problem and rapid diagnostic improvements are urgently required. Mycobacteria-specific fluorescence and bioluminescence phenomena have been found to be useful for a wide range of mycobacteria-focused research. Here, we present a critical survey of the most promising techniques in this field and the potential of new methods under investigation. These approaches include acid-fast staining, intrinsic fluorescence of the coenzyme F₄₂₀, fluorogenic substrates (e.g., β-lactamase-sensitive coumpounds) and recombination of mycobacteria or mycobacteriophages. Probably the most interesting and emerging host-inspecting approach is in vivo imaging. Detection of fluorescence in vivo, however, is complicated by light scattering, light absorption, and autofluorescence, caused by the tissues. Despite this, many of these systems show promise as the foundations for improved rapid analysis and imaging of mycobacterial infections, both in vitro and in vivo.

Neuroprotection through flavonoid: Enhancement of the glyoxalase pathway

The glyoxalase pathway functions to detoxify reactive dicarbonyl compounds, most importantly methylglyoxal. The glyoxalase pathway is an antioxidant defense mechanism that is essential for neuroprotection. Excessive concentrations of methylglyoxal have deleterious effects on cells, leading to increased levels of inflammation and oxidative stress. Neurodegenerative diseases - including Alzheimer's, Parkinson's, Aging and Autism Spectrum Disorder - are often induced or exacerbated by accumulation of methylglyoxal. Antioxidant compounds possess several distinct mechanisms that enhance the glyoxalase pathway and function as neuroprotectants. Flavonoids are well-researched secondary plant metabolites that appear to be effective in reducing levels of oxidative stress and inflammation in neural cells. Novel flavonoids could be designed, synthesized and tested to protect against neurodegenerative diseases through regulating the glyoxalase pathway.

Metal-Based Nanoparticles for the Treatment of Infectious Diseases

Infectious diseases can be transmitted and they cause a significant burden on public health globally. They are the greatest world killers and it is estimated that they are responsible for the demise of over 17 million people annually. The impact of these diseases is greater in the developing countries. People with compromised immune systems and children are the most affected. Infectious diseases may be caused by bacteria, viruses, and protozoa. The treatment of infectious diseases is hampered by simultaneous resistance to multiple drugs, indicating that there is a serious and pressing need to develop new therapeutics that can overcome drug resistance. This review will focus on the recent reports of metal-based nanoparticles that are potential therapeutics for the treatment of infectious diseases and their biological efficacy (in vitro and in vivo).