Nanomedicine for intracellular therapy

Mechanistic insights into nanoparticle surface-bacterial membrane interactions in overcoming antibiotic resistance

Antimicrobial Resistance (AMR) raises a serious concern as it contributes to the global mortality by 5 million deaths per year. The overall impact pertaining to significant membrane changes, through broad spectrum drugs have rendered the bacteria resistant over the years. The economic expenditure due to increasing drug resistance poses a global burden on healthcare community and must be dealt with immediate effect. Nanoparticles (NP) have demonstrated inherent therapeutic potential or can serve as nanocarriers of antibiotics against multidrug resistant (MDR) pathogens. These carriers can mask the antibiotics and help evade the resistance mechanism of the bacteria. The targeted delivery can be fine-tuned through surface functionalization of Nanocarriers using aptamers, antibodies etc. This review covers various molecular mechanisms acquired by resistant bacteria towards membrane modification. Mechanistic insight on 'NP surface-bacterial membrane' interactions are crucial in deciding the role of NP as therapeutic. Finally, we highlight the potential accessible membrane targets for designing smart surface-functionalized nanocarriers which can act as bacteria-targeted robots over the existing clinically available antibiotics. As the bacterial strains around us continue to evolve into resistant versions, nanomedicine can offer promising and alternative tools in overcoming AMR.

Elimination of macrophage-entrapped antibiotic-resistant bacteria by a targeted metal-organic framework-based nanoplatform

A novel metal-organic framework-based platform was designed and constructed for photosensitizer delivery for the elimination of intracellular antibiotic-resistant bacteria. With the merit of targeting and internalizing ability, the system could kill the stealthy bacteria efficiently under light irradiation.

Antibacterial nanotruffles for treatment of intracellular bacterial infection

Bacterial pathogens residing in host macrophages in intracellular infections are hard to eradicate because traditional antibiotics do not readily enter the cells or get eliminated via efflux pumps. To overcome this challenge, we developed a new particle formulation with a size amenable to selective macrophage uptake, loaded with two antibacterial agents - pexiganan and silver (Ag) nanoparticles. Here, pexiganan was loaded in 600 nm poly(lactic-co-glycolic acid) (PLGA) particles (NP), and the particle surface was modified with an iron-tannic acid supramolecular complex (pTA) that help attach Ag nanoparticles. PLGA particles coated with Ag (NP-pTA-Ag) were taken up by macrophages, but not by non-phagocytic cells, such as fibroblasts, reducing non-specific toxicity associated with Ag nanoparticles. NP-pTA-Ag loaded with pexiganan (Pex@NP-pTA-Ag) showed more potent antibacterial activity against various intracellular pathogens than NP-pTA-Ag or Pex@NP (pexiganan-loaded NP with no Ag), suggesting a collaborative function between pexiganan and Ag nanoparticles. Mouse whole-body imaging demonstrated that, upon intravenous injection, NP-pTA-Ag quickly accumulated in the liver and spleen, where intracellular bacteria tend to reside. These results support that Pex@NP-pTA-Ag is a promising strategy for the treatment of intracellular bacterial infection.

Recent Advances in Polymeric Nanoparticle-Encapsulated Drugs against Intracellular Infections

Polymeric nanocarriers (PNs) have demonstrated to be a promising alternative to treat intracellular infections. They have outstanding performance in delivering antimicrobials intracellularly to reach an adequate dose level and improve their therapeutic efficacy. PNs offer opportunities for preventing unwanted drug interactions and degradation before reaching the target cell of tissue and thus decreasing the development of resistance in microorganisms. The use of PNs has the potential to reduce the dose and adverse side effects, providing better efficiency and effectiveness of therapeutic regimens, especially in drugs having high toxicity, low solubility in the physiological environment and low bioavailability. This review provides an overview of nanoparticles made of different polymeric precursors and the main methodologies to nanofabricate platforms of tuned physicochemical and morphological properties and surface chemistry for controlled release of antimicrobials in the target. It highlights the versatility of these nanosystems and their challenges and opportunities to deliver antimicrobial drugs to treat intracellular infections and mentions nanotoxicology aspects and future outlooks.

Intracellular delivery, accumulation, and discrepancy in antibacterial activity of four enrofloxacin-loaded fatty acid solid lipid nanoparticles

Four fatty acid-solid lipid nanoparticles (SLNs) were formulated and evaluated for intracellular delivery, accumulation, as well as discrepancy in antimicrobial efficacy of their loaded enrofloxacin by using RAW 264.7 cells. The delivery efficacy of enrofloxacin into the macrophages by docosanoic acid SLNs (DAS), octadecanoic acid SLNs (OAS), hexadecanoic acid SLNs (HAS), and tetradecanoic acid SLNs (TAS) were 26.1-29.0, 9.3-10.3, 4.7-5.3 and 4.5-5.0 folds, respectively, compared to free drug when co-incubation for 0.25-4 h. The longer fatty acid prepared nanoparticles loaded enrofloxacin eliminated more slowly and accumulated in the cells for a longer time.The confocal microscopy also demonstrated that higher amount of fatty acid SLNs entered the cells with stronger accumulation performance and less amount SLNs absorbed on the cytomembrane as the carbon chain of fatty acids increased. The bactericidal activity of the four fatty acid SLNs against intracellular Salmonella CVCC541 significantly enhanced compared to the free enrofloxacin. These results revealed that fatty acid SLNs, especially docosanoic acid nanoparticles, might be effective nanocarriers to ferry enrofloxacin or other lipid soluble drugs into cells for intracellular bacterial infection treatment.

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.

Inhibition of sialidase activity and cellular invasion by the bacterial vaginosis pathogen Gardnerella vaginalis

Bacterial vaginosis is a genital tract infection, thought to be caused by transformation of a lactobacillus-rich flora to a dysbiotic microbiota enriched in mixed anaerobes. The most prominent of these is Gardnerella vaginalis (GV), an anaerobic pathogen that produces sialidase enzyme to cleave terminal sialic acid residues from human glycans. Notably, high sialidase activity is associated with preterm birth and low birthweight. We explored the potential of the sialidase inhibitor Zanamavir against GV whole cell sialidase activity using methyl–umbelliferyl neuraminic acid (MU-NANA) cleavage assays, with Zanamavir causing a 30% reduction in whole cell GV sialidase activity (p < 0.05). Furthermore, cellular invasion assays using HeLa cervical epithelial cells, infected with GV, demonstrated that Zanamivir elicited a 50% reduction in cell association and invasion (p < 0.05). Our data thus highlight that pharmacological sialidase inhibitors are able to modify BV-associated sialidase activity and influence host–pathogen interactions and may represent novel therapeutic adjuncts.

Clearance of intracellular Klebsiella pneumoniae infection using gentamicin-loaded nanoparticles

Klebsiella pneumoniae is a foremost gram-negative pathogen that can induce life-threatening nosocomial pulmonary infections. Although it can be phagocytosed successfully by lung resident macrophages, this pathogen remains viable within vacuolar compartments, resulting in chronic infection and limiting therapeutic treatment with antibiotics. In this study, we aimed to generate and evaluate a cell-penetrant antibiotic poly(lactide-co-glycolide) (PLGA)-based formulation that could successfully treat intracellular K. pneumoniae infection. Screening of formulation conditions allowed the generation of high drug loaded nanoparticles through a water-in-oil-in-water approach. We demonstrated the therapeutic usefulness of these gentamicin-loaded nanoparticles (GNPs), showing their ability to improve survival and provide extended prophylactic protection towards K. pneumoniae using a Galleria mellonella infection model. We subsequently showed that the GNPs could be phagocytosed by K. pneumoniae infected macrophages, and significantly reduce the viability of the intracellular bacteria without further stimulation of pro-inflammatory or pro-apoptotic effects on the macrophages. Taken together, these results clearly show the potential to use antibiotic loaded NPs to treat intracellular K. pneumoniae infection, reducing bacterial viability without concomitant stimulation of inflammatory or pyroptotic pathways in the treated cells.

Biological macromolecules based targeted nanodrug delivery systems for the treatment of intracellular infections

Intracellular infections are tricky to treat, the reason being the poor penetration of antibiotics/antimycotics into the microbial niche (host cell). Macrophages are primary targets of facultative and obligate intracellular bacteria/fungi to be abused as host cells. The need for drugs with better intracellular penetration led to the development of endocytosable drug carriers, which can cross the cell membrane of the host cells (macrophages) by imitating the entry path of the pathogens. Therefore, the drugs can be targeted to macrophages ensuring enhanced therapeutic effect. This review discusses the exploitation of various nanocarriers for targeted delivery of drugs to the macrophages in the last two decades.

Toward an optimized treatment of intracellular bacterial infections: input of nanoparticulate drug delivery systems

Intracellular pathogenic bacteria can lead to some of the most life-threatening infections. By evolving a number of ingenious mechanisms, these bacteria have the ability to invade, colonize and survive in the host cells in active or latent forms over prolonged period of time. A variety of nanoparticulate systems have been developed to optimize the delivery of antibiotics. Main advantages of nanoparticulate systems as compared with free drugs are an efficient drug encapsulation, protection from inactivation, targeting infection sites and the possibility to deliver drugs by overcoming cellular barriers. Nevertheless, despite the great progresses in treating intracellular infections using nanoparticulate carriers, some challenges still remain, such as targeting cellular subcompartments with bacteria and delivering synergistic drug combinations. Engineered nanoparticles should allow controlling drug release both inside cells and within the extracellular space before reaching the target cells.

Genome Expression Profiling-Based Identification and Administration Efficacy of Host-Directed Antimicrobial Drugs against Respiratory Infection by Nontypeable Haemophilus influenzae

Therapies that are safe, effective, and not vulnerable to developing resistance are highly desirable to counteract bacterial infections. Host-directed therapeutics is an antimicrobial approach alternative to conventional antibiotics based on perturbing host pathways subverted by pathogens during their life cycle by using host-directed drugs. In this study, we identified and evaluated the efficacy of a panel of host-directed drugs against respiratory infection by nontypeable Haemophilus influenzae (NTHi). NTHi is an opportunistic pathogen that is an important cause of exacerbation of chronic obstructive pulmonary disease (COPD). We screened for host genes differentially expressed upon infection by the clinical isolate NTHi375 by analyzing cell whole-genome expression profiling and identified a repertoire of host target candidates that were pharmacologically modulated. Based on the proposed relationship between NTHi intracellular location and persistence, we hypothesized that drugs perturbing host pathways used by NTHi to enter epithelial cells could have antimicrobial potential against NTHi infection. Interfering drugs were tested for their effects on bacterial and cellular viability, on NTHi-epithelial cell interplay, and on mouse pulmonary infection. Glucocorticoids and statins lacked in vitro and/or in vivo efficacy. Conversely, the sirtuin-1 activator resveratrol showed a bactericidal effect against NTHi, and the PDE4 inhibitor rolipram showed therapeutic efficacy by lowering NTHi375 counts intracellularly and in the lungs of infected mice. PDE4 inhibition is currently prescribed in COPD, and resveratrol is an attractive geroprotector for COPD treatment. Together, these results expand our knowledge of NTHi-triggered host subversion and frame the antimicrobial potential of rolipram and resveratrol against NTHi respiratory infection.

Nanocapsules loaded with iron-saturated bovine lactoferrin have antimicrobial therapeutic potential and maintain calcium, zinc and iron metabolism

AIM

This study aimed to evaluate the potential antimicrobial efficacy of alginate gel-encapsulated ceramic nanocarriers loaded with iron-saturated bovine lactoferrin (Fe-bLf) nanocarriers/nanocapsules (AEC-CP-Fe-bLf NCs).

MATERIALS & METHODS

The antimicrobial activities of non-nanoformulated apo (iron free), Fe-bLf and native forms of Australian bLf against pathogenic Salmonella typhimurium (wild strain) were studied in vitro. The efficacy of AEC-CP-Fe-bLf NCs were checked in vivo using Balb/c mice model.

RESULTS

The study revealed that native bLf is more effective in combating infection than the conventional drug ciprofloxacin (0.4 mg/ml). The efficacy of the drug was also revealed in vivo when BALB/c mice that, after being challenged with S. typhimurium (200 μl of 10(8) CFU/ml suspension), were fed orally with a nanoformulated bLf diet and the infection was observed to be eliminated. However, chronic infection developed in the group of infected mice that did not receive any drug treatment, as well as the mice treated with ciprofloxacin. The immune response to bacterial infection and to various drug treatments thereafter was studied in the mice.

CONCLUSION

The study concludes that bLf and nanoformulated Fe-bLf are more effective in the treatment of Salmonella-infected mice than ciprofloxacin.

Nanomedicine in the Management of Microbial Infection - Overview and Perspectives

For more than 2 billion years, microbes have reigned on our planet, evolving or outlasting many obstacles they have encountered. In the 20th century, this trend took a dramatic turn with the introduction of antibiotics and vaccines. Nevertheless, since then, microbes have progressively eroded the effectiveness of previously successful antibiotics by developing resistance, and many infections have eluded conventional vaccine design approaches. Moreover, the emergence of resistant and more virulent strains of bacteria has outpaced the development of new antibiotics over the last few decades. These trends have had major economic and health impacts at all levels of the socioeconomic spectrum - we need breakthrough innovations that could effectively manage microbial infections and deliver solutions that stand the test of time. The application of nanotechnologies to medicine, or nanomedicine, which has already demonstrated its tremendous impact on the pharmaceutical and biotechnology industries, is rapidly becoming a major driving force behind ongoing changes in the antimicrobial field. Here we provide an overview on the current progress of nanomedicine in the management of microbial infection, including diagnosis, antimicrobial therapy, drug delivery, medical devices, and vaccines, as well as perspectives on the opportunities and challenges in antimicrobial nanomedicine.

Biodegradable nanoparticles for intracellular delivery of antimicrobial agents

Biodegradable nanoparticles have emerged as a promising strategy for ferrying antimicrobial agents into specific cells due to their unique properties. This review discusses the current progress and challenges of biodegradable nanoparticles for intracellular antimicrobial delivery to understand design principles for the development of ideal nanocarriers. The intracellular delivery performances of biodegradable nanoparticles for diverse antimicrobial agents are first summarized. Second, the cellular internalization and intracellular trafficking, degradation and release kinetics of nanoparticles as well as their relation with intracellular delivery of encapsulated antimicrobial agents are provided. Third, the influences of nanoparticle properties on the cellular internalization and intracellular fate of nanoparticles and their payload antimicrobial agents are discussed. Finally, the challenges and perspectives of nanoparticles for intracellular delivery of antimicrobial agents are addressed. The review will be helpful to the scientists who are interested in searching for more efficient nanosystem strategies for intracellular delivery of antimicrobial agents.

Multiple strategies to activate gold nanoparticles as antibiotics

Widespread antibiotic resistance calls for new strategies. Nanotechnology provides a chance to overcome antibiotic resistance by multiple antibiotic mechanisms. This paper reviews the progress in activating gold nanoparticles with nonantibiotic or antibiotic molecules to combat bacterial resistance, analyzes the gap between experimental achievements and real clinical application, and suggests some potential directions in developing antibacterial nanodrugs.

Advances in Integrative Nanomedicine for Improving Infectious Disease Treatment in Public Health

INTRODUCTION

Infectious diseases present public health challenges worldwide. An emerging integrative approach to treating infectious diseases is using nanoparticle (NP) forms of traditional and alternative medicines. Advantages of nanomedicine delivery methods include better disease targeting, especially for intracellular pathogens, ability to cross membranes and enter cells, longer duration drug action, reduced side effects, and cost savings from lower doses.

METHODS

We searched Pubmed articles in English with keywords related to nanoparticles and nanomedicine. Nanotechnology terms were also combined with keywords for drug delivery, infectious diseases, herbs, antioxidants, homeopathy, and adaptation.

RESULTS

NPs are very small forms of material substances, measuring 1-100 nanometers along at least one dimension. Compared with bulk forms, NPs' large ratio of surface-area-to-volume confers increased reactivity and adsorptive capacity, with unique electromagnetic, chemical, biological, and quantum properties. Nanotechnology uses natural botanical agents for green manufacturing of less toxic NPs.

DISCUSSION

Nanoparticle herbs and nutriceuticals can treat infections via improved bioavailability and antiinflammatory, antioxidant, and immunomodulatory effects. Recent studies demonstrate that homeopathic medicines may contain source and/or silica nanoparticles because of their traditional manufacturing processes. Homeopathy, as a form of nanomedicine, has a promising history of treating epidemic infectious diseases, including malaria, leptospirosis and HIV/AIDS, in addition to acute upper respiratory infections. Adaptive changes in the host's complex networks underlie effects.

CONCLUSIONS

Nanomedicine is integrative, blending modern technology with natural products to reduce toxicity and support immune function. Nanomedicine using traditional agents from alternative systems of medicine can facilitate progress in integrative public health approaches to infectious diseases.

The enhanced permeability retention effect: a new paradigm for drug targeting in infection

Multidrug-resistant, Gram-negative infection is a major global determinant of morbidity, mortality and cost of care. The advent of nanomedicine has enabled tailored engineering of macromolecular constructs, permitting increasingly selective targeting, alteration of volume of distribution and activity/toxicity. Macromolecules tend to passively and preferentially accumulate at sites of enhanced vascular permeability and are then retained. This enhanced permeability and retention (EPR) effect, whilst recognized as a major breakthrough in anti-tumoral targeting, has not yet been fully exploited in infection. Shared pathophysiological pathways in both cancer and infection are evident and a number of novel nanomedicines have shown promise in selective, passive, size-mediated targeting to infection. This review describes the similarities and parallels in pathophysiological pathways at molecular, cellular and circulatory levels between inflammation/infection and cancer therapy, where use of this principle has been established.