Antimicrobial efficacy of tobramycin polymeric nanoparticles for Pseudomonas aeruginosa infections in cystic fibrosis: formulation, characterisation and functionalisation with dornase alfa (DNase)

Targeted treatment for biofilm-based infections using PEGylated tobramycin

Chronic infections often involve biofilm-based bacteria, in which the biofilm results in significant resistance against antimicrobial agents and prevents eradication of the infection. The physicochemical barrier presented by the biofilm matrix is a major impediment to the delivery of many antibiotics. Previously, PEGylation has been shown to improve antibiotic penetration into biofilms in vitro. In these studies, PEGylating tobramycin was investigated both in vitro and in vivo. Two distinct PEGylated tobramycin molecules were synthesized (mPEG-SA-Tob and mPEG-AA-Tob). Then, in a P. aeruginosa biofilm in vitro model, we found that mPEG-SA-Tob can operate as a prodrug and showed 7 times more effectiveness than tobramycin (MIC80: 14 μM vs.100 μM). This improved biofilm eradication is attributable to the fact that mPEG-SA-Tob can aid tobramycin to penetrate through the biofilm and overcome the alginate-mediated antibiotic resistance. Finally, we used an in vivo biofilm-based chronic pulmonary infection rat model to confirm the therapeutic impact of mPEG-SA-Tob on biofilm-based chronic lung infection. mPEG-SA-Tob has a better therapeutic impact than tobramycin in that it cannot only stop P. aeruginosa from multiplying in the lungs but can also reduce inflammation caused by infections and prevent a recurrence infection. Overall, our findings show that PEGylated tobramycin is an effective treatment for biofilm-based chronic lung infections.

Inhaled antibiotics: A promising drug delivery strategies for efficient treatment of lower respiratory tract infections (LRTIs) associated with antibiotic resistant biofilm-dwelling and intracellular bacterial pathogens

Antibiotic-resistant bacteria associated with LRTIs are frequently associated with inefficient treatment outcomes. Antibiotic-resistant Streptococcus pneumoniae, Haemophilus influenzae, Pseudomonas aeruginosa, and Staphylococcus aureus, infections are strongly associated with pulmonary exacerbations and require frequent hospital admissions, usually following failed management in the community. These bacteria are difficult to treat as they demonstrate multiple adaptational mechanisms including biofilm formation to resist antibiotic threats. Currently, many patients with the genetic disease cystic fibrosis (CF), non-CF bronchiectasis (NCFB) and chronic obstructive pulmonary disease (COPD) experience exacerbations of their lung disease and require high doses of systemically administered antibiotics to achieve meaningful clinical effects, but even with high systemic doses penetration of antibiotic into the site of infection within the lung is suboptimal. Pulmonary drug delivery technology that reliably deliver antibacterials directly into the infected cells of the lungs and penetrate bacterial biofilms to provide therapeutic doses with a greatly reduced risk of systemic adverse effects. Inhaled liposomal-packaged antibiotic with biofilm-dissolving drugs offer the opportunity for targeted, and highly effective antibacterial therapeutics in the lungs. Although the challenges with development of some inhaled antibiotics and their clinicals trials have been studied; however, only few inhaled products are available on market. This review addresses the current treatment challenges of antibiotic-resistant bacteria in the lung with some clinical outcomes and provides future directions with innovative ideas on new inhaled formulations and delivery technology that promise enhanced killing of antibiotic-resistant biofilm-dwelling bacteria.

Chitosan/Alginate-Based Nanoparticles for Antibacterial Agents Delivery

Nanoparticle systems integrating alginate and chitosan emerge as a promising avenue to tackle challenges in leveraging the potency of pharmacological active agents. Owing to their intrinsic properties as polysaccharides, alginate and chitosan, exhibit remarkable biocompatibility, rendering them conducive to bodily integration. By downsizing drug particles to the nano-scale, the system enhances drug solubility in aqueous environments by augmenting surface area. Additionally, the system orchestrates extended drug release kinetics, aligning well with the exigencies of chronic drug release requisite for antibacterial therapeutics. A thorough scrutiny of existing literature underscores a wealth of evidence supporting the utilization of the alginate-chitosan nanoparticle system for antibacterial agent delivery. Literature reviews present abundant evidence of the utilization of nanoparticle systems based on a combination of alginate and chitosan for antibacterial agent delivery. Various experiments demonstrate enhanced antibacterial efficacy, including an increase in the inhibitory zone diameter, improvement in the minimum inhibitory concentration, and an enhancement in the bacterial reduction rate. This enhancement in efficacy occurs due to mechanisms involving increased solubility resulting from particle size reduction, prolonged release effects, and enhanced selectivity towards bacterial cell walls, stemming from ionic interactions between positively charged particles and teichoic acid on bacterial cell walls. However, clinical studies remain limited, and there are currently no marketed antibacterial drugs utilizing this system. Hence, expediting clinical efficacy validation is crucial to maximize its benefits promptly.

Polymeric Nanoparticles for Drug Delivery

The recent emergence of nanomedicine has revolutionized the therapeutic landscape and necessitated the creation of more sophisticated drug delivery systems. Polymeric nanoparticles sit at the forefront of numerous promising drug delivery designs, due to their unmatched control over physiochemical properties such as size, shape, architecture, charge, and surface functionality. Furthermore, polymeric nanoparticles have the ability to navigate various biological barriers to precisely target specific sites within the body, encapsulate a diverse range of therapeutic cargo and efficiently release this cargo in response to internal and external stimuli. However, despite these remarkable advantages, the presence of polymeric nanoparticles in wider clinical application is minimal. This review will provide a comprehensive understanding of polymeric nanoparticles as drug delivery vehicles. The biological barriers affecting drug delivery will be outlined first, followed by a comprehensive description of the various nanoparticle designs and preparation methods, beginning with the polymers on which they are based. The review will meticulously explore the current performance of polymeric nanoparticles against a myriad of diseases including cancer, viral and bacterial infections, before finally evaluating the advantages and crucial challenges that will determine their wider clinical potential in the decades to come.

Multitasking functions of bacterial extracellular DNA in biofilms

Bacterial biofilms are intricate ecosystems of microbial communities that adhere to various surfaces and are enveloped by an extracellular matrix composed of polymeric substances. Within the context of bacterial biofilms, extracellular DNA (eDNA) originates from cell lysis or is actively secreted, where it exerts a significant influence on the formation, stability, and resistance of biofilms to environmental stressors. The exploration of eDNA within bacterial biofilms holds paramount importance in research, with far-reaching implications for both human health and the environment. An enhanced understanding of the functions of eDNA in biofilm formation and antibiotic resistance could inspire the development of strategies to combat biofilm-related infections and improve the management of antibiotic resistance. This comprehensive review encapsulates the latest discoveries concerning eDNA, encompassing its origins, functions within bacterial biofilms, and significance in bacterial pathogenesis.

Excipients for Novel Inhaled Dosage Forms: An Overview

Pulmonary drug delivery is a form of local targeting to the lungs in patients with respiratory disorders like cystic fibrosis, pulmonary arterial hypertension (PAH), asthma, chronic pulmonary infections, and lung cancer. In addition, noninvasive pulmonary delivery also presents an attractive alternative to systemically administered therapeutics, not only for localized respiratory disorders but also for systemic absorption. Pulmonary delivery offers the advantages of a relatively low dose, low incidence of systemic side effects, and rapid onset of action for some drugs compared to other systemic administration routes. While promising, inhaled delivery of therapeutics is often complex owing to factors encompassing mechanical barriers, chemical barriers, selection of inhalation device, and limited choice of dosage form excipients. There are very few excipients that are approved by the FDA for use in developing inhaled drug products. Depending upon the dosage form, and inhalation devices such as pMDIs, DPIs, and nebulizers, different excipients can be used to provide physical and chemical stability and to deliver the dose efficiently to the lungs. This review article focuses on discussing a variety of excipients that have been used in novel inhaled dosage forms as well as inhalation devices.

Targeted Molecular Therapeutics for Pulmonary Diseases: Addressing the Need for Precise Drug Delivery

Respiratory diseases are a major concern in public health, impacting a large population worldwide. Despite the availability of therapies that alleviate symptoms, selectively addressing the critical points of pathopathways remains a major challenge. Innovative formulations designed for reaching these targets within the airways, enhanced selectivity, and prolonged therapeutic effects offer promising solutions. To provide insights into the specific medical requirements of chronic respiratory diseases, the initial focus of this chapter is directed on lung physiology, emphasizing the significance of lung barriers. Current treatments involving small molecules and the potential of gene therapy are also discussed. Additionally, we will explore targeting approaches, with a particular emphasis on nanoparticles, comparing targeted and non-targeted formulations for pulmonary administration. Finally, the potential of inhaled sphingolipids in the context of respiratory diseases is briefly discussed, highlighting their promising prospects in the field.

Amphotericin B-loaded natural latex dressing for treating Candida albicans wound infections using Galleria mellonella model

Amphotericin B (AmB) is the gold standard for antifungal drugs. However, AmB systemic administration is restricted because of its side effects. Here, we report AmB loaded in natural rubber latex (NRL), a sustained delivery system with low toxicity, which stimulates angiogenesis, cell adhesion and accelerates wound healing. Physicochemical characterizations showed that AmB did not bind chemically to the polymeric matrix. Electronic and topographical images showed small crystalline aggregates from AmB crystals on the polymer surface. About 56.6% of AmB was released by the NRL in 120 h. However, 33.6% of this antifungal was delivered in the first 24 h due to the presence of AmB on the polymer surface. The biomaterial's excellent hemo- and cytocompatibility with erythrocytes and human dermal fibroblasts (HDF) confirmed its safety for dermal wound application. Antifungal assay against Candida albicans showed that AmB-NRL presented a dose-dependent behavior with an inhibition halo of 30.0 ± 1.0 mm. Galleria mellonella was employed as an in vivo model for C. albicans infection. Survival rates of 60% were observed following the injection of AmB (0.5 mg.mL-1) in G. mellonella larvae infected by C. albicans. Likewise, AmB-NRL (0.5 mg.mL-1) presented survival rates of 40%, inferring antifungal activity against fungus. Thus, NRL adequately acts as an AmB-sustained release matrix, which is an exciting approach, since this antifungal is toxic at high concentrations. Our findings suggest that AmB-NRL is an efficient, safe, and reasonably priced ($0.15) dressing for the treatment of cutaneous fungal infections.

Nanotechnology-Based Drug Delivery Systems to Control Bacterial-Biofilm-Associated Lung Infections

Airway mucus dysfunction and impaired immunological defenses are hallmarks of several lung diseases, including asthma, cystic fibrosis, and chronic obstructive pulmonary diseases, and are mostly causative factors in bacterial-biofilm-associated respiratory tract infections. Bacteria residing within the biofilm architecture pose a complex challenge in clinical settings due to their increased tolerance to currently available antibiotics and host immune responses, resulting in chronic infections with high recalcitrance and high rates of morbidity and mortality. To address these unmet clinical needs, potential anti-biofilm therapeutic strategies are being developed to effectively control bacterial biofilm. This review focuses on recent advances in the development and application of nanoparticulate drug delivery systems for the treatment of biofilm-associated respiratory tract infections, especially addressing the respiratory barriers of concern for biofilm accessibility and the various types of nanoparticles used to combat biofilms. Understanding the obstacles facing pulmonary drug delivery to bacterial biofilms and nanoparticle-based approaches to combatting biofilm may encourage researchers to explore promising treatment modalities for bacterial-biofilm-associated chronic lung infections.

Engineered lipid liquid crystalline nanoparticles as an inhaled nanoplatform for mucus penetration enhancement

Nanocarrier-assisted pulmonary drug delivery system has been widely employed for lung local disease treatment due to its enhanced drug lesion accumulation and reduced systematical side effects. However, the mucus barriers covered on the epithelia of trachea and bronchial tree construct a dense barrier for inhaled nanocarrier transport, which compromises the therapeutical effects. In this study, a lipid liquid crystalline nanoparticle NLP@Z with surface zwitterion material hexadecyl betaine (HB) modification and N-acetylcysteine (NAC) encapsulation was presented to exert the combination strategy of mucus-inert surface and mucus degradation. The HB modification endowed NLP@Z mucus-inert surface to inhibit the interaction between NLP@Z and mucins, and the encapsulated NAC could effectively degrade the mucins and further decrease the mucus viscosity. This combination strategy was proved to significantly promote the mucus penetration performance and enhance epithelial cell uptake. In addition, the proposed NLP@Z was equipped with desired nebulization property, which could be served as a potential pulmonary delivery nanoplatform. In summary, the proposed NLP@Z highlights the employment of the combination strategy for mucus penetration enhancement in pulmonary delivery, which may become a versatile platform for lung disease therapy.

Drug delivery strategies for antibiofilm therapy

Although new antibiofilm agents have been developed to prevent and eliminate pathogenic biofilms, their widespread clinical use is hindered by poor biocompatibility and bioavailability, unspecific interactions and insufficient local concentrations. The development of innovative drug delivery strategies can facilitate penetration of antimicrobials through biofilms, promote drug dispersal and synergistic bactericidal effects, and provide novel paradigms for clinical application. In this Review, we discuss the potential benefits of such emerging techniques for improving the clinical efficacy of antibiofilm agents, as well as highlighting the existing limitations and future prospects for these therapies in the clinic.

An Inhalable Hybrid Biomimetic Nanoplatform for Sequential Drug Release and Remodeling Lung Immune Homeostasis in Acute Lung Injury Treatment

Interactions of lung macrophages and recruited neutrophils with the lung microenvironment continuously aggravate the dysregulation of lung inflammation in the pathogenesis of acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). Either modulating macrophages or destroying neutrophil counts cannot guarantee a satisfactory outcome in ARDS treatment. Aimed at inhibiting the coordinated action of neutrophils and macrophages and modulating the hyper-inflammatory condition, an inhalable biomimetic sequential drug-releasing nanoplatform was developed for the combinatorial treatment of ALI. The nanoplatform (termed D-SEL) was made by conjugating DNase I, as outer cleavable arms, to a serum exosomal and liposomal hybrid nanocarrier (termed SEL) via a matrix metalloproteinase 9 (MMP-9)-cleavable peptide and then encapsulating methylprednisolone sodium succinate (MPS). In lipopolysaccharide (LPS) induced ALI in mice, the MPS/D-SEL moved through muco-obstructive airways and was retained in the alveoli for over 24 h postinhalation. DNase I was then released from the nanocarrier first after responding to MMP-9, resulting in inner SEL core exposure, which precisely delivered MPS into macrophages for promoting M2 macrophage polarization. Local and sustained DNase I release degraded dysregulated neutrophil extracellular traps (NETs) and suppressed neutrophil activation and the mucus plugging microenvironment, which in turn amplified M2 macrophage polarization efficiency. Such dual-stage drug release behavior facilitated down-regulation of pro-inflammatory cytokines in the lung but anti-inflammatory cytokine production through remodeling lung immune homeostasis, ultimately promoting lung tissue repair. This work presents a versatile hybrid biomimetic nanoplatform for the local pulmonary delivery of dual-drug therapeutics and displays potential in the treatment of acute inflammation.

ISOTHERMAL TITRATION CALORIMETRY (ITC) AS A PROMISING TOOL IN PHARMACEUTICAL NANOTECHNOLOGY

Isothermal titration calorimetry (ITC) is a technique for evaluating the thermodynamic profiles of connection between two molecules, allowing the experimental design of nanoparticles systems with drugs and/or biological molecules. Taking into account the relevance of ITC, we conducted, therefore, an integrative revision of the literature, from 2000 to 2023, on the main purposes of using this technique in pharmaceutical nanotechnology. The search were carried out in the Pubmed, Sciencedirect, Web of Science, and Scifinder databases using the descriptors "Nanoparticles", "Isothermal Titration Calorimetry", and "ITC". We have observed that the ITC technique has been increasingly used in pharmaceutical nanotechnology, seeking to understand the interaction mechanisms in the formation of nanoparticles. Additionally, to understand the behavior of nanoparticles with biological materials (proteins, DNA, cell membranes, among others), thereby helping to understand the behavior of nanocarriers in vivo studies. As a contribution, we intended to reveal the importance of ITC in the laboratory routine, which is itself a quick and easy technique to obtain relevant results that help to optimize the nanosystems formulation process.

Fate of the capping agent of biologically produced gold nanoparticles and adsorption of enzymes onto their surface

Enzymotherapy based on DNase I or RNase A has often been suggested as an optional strategy for cancer treatment. The efficacy of such procedures is limited e.g. by a short half-time of the enzymes or a low rate of their internalization. The use of nanoparticles, such as gold nanoparticles (AuNPs), helps to overcome these limits. Specifically, biologically produced AuNPs represent an interesting variant here due to naturally occurring capping agents (CA) on their surface. The composition of the CA depends on the producing microorganism. CAs are responsible for the stabilization of the nanoparticles, and promote the direct linking of targeting and therapeutic molecules. This study provided proof of enzyme adsorption onto gold nanoparticles and digestion efficacy of AuNPs-adsorbed enzymes. We employed Fusarium oxysporum extract to produce AuNPs. These nanoparticles were round or polygonal with a size of about 5 nm, negative surface charge of about - 33 mV, and maximum absorption peak at 530 nm. After the adsorption of DNAse I, RNase A, or Proteinase K onto the AuNPs surface, the nanoparticles exhibited shifts in surface charge (values between - 22 and - 13 mV) and maximum absorption peak (values between 513 and 534 nm). The ability of AuNP-enzyme complexes to digest different targets was compared to enzymes alone. We found a remarkable degradation of ssDNA, and dsDNA by AuNP-DNAse I, and a modest degradation of ssRNA by AuNP-RNase A. The presence of particular enzymes on the AuNP surface was proved by liquid chromatography-mass spectrometry (LC-MS). Using SDS-PAGE electrophoresis, we detected a remarkable digestion of collagen type I and fibrinogen by AuNP-proteinase K complexes. We concluded that the biologically produced AuNPs directly bound DNase I, RNase A, and proteinase K while preserving their ability to digest specific targets. Therefore, according to our results, AuNPs can be used as effective enzyme carriers and the AuNP-enzyme conjugates can be effective tools for enzymotherapy.

Nanomedicine: New Frontiers in Fighting Microbial Infections

Microbes have dominated life on Earth for the past two billion years, despite facing a variety of obstacles. In the 20th century, antibiotics and immunizations brought about these changes. Since then, microorganisms have acquired resistance, and various infectious diseases have been able to avoid being treated with traditionally developed vaccines. Antibiotic resistance and pathogenicity have surpassed antibiotic discovery in terms of importance over the course of the past few decades. These shifts have resulted in tremendous economic and health repercussions across the board for all socioeconomic levels; thus, we require ground-breaking innovations to effectively manage microbial infections and to provide long-term solutions. The pharmaceutical and biotechnology sectors have been radically altered as a result of nanomedicine, and this trend is now spreading to the antibacterial research community. Here, we examine the role that nanomedicine plays in the prevention of microbial infections, including topics such as diagnosis, antimicrobial therapy, pharmaceutical administration, and immunizations, as well as the opportunities and challenges that lie ahead.

Tobramycin Nanoantibiotics and Their Advantages: A Minireview

Nowadays, antimicrobial resistance (AMR) represents a challenge for antibiotic therapy, mostly involving Gram-negative bacteria. Among the strategies activated to overcome AMR, the repurposing of already available antimicrobial molecules by encapsulating them in drug delivery systems, such as nanoparticles (NPs) and also engineered NPs, seems to be promising. Tobramycin is a powerful and effective aminoglycoside, approved for complicated infections and reinfections and indicated mainly against Gram-negative bacteria, such as Pseudomonas aeruginosa, Escherichia coli, Proteus, Klebsiella, Enterobacter, Serratia, Providencia, and Citrobacter species. However, the drug presents several side effects, mostly due to dose frequency, and for this reason, it is a good candidate for nanomedicine formulation. This review paper is focused on what has been conducted in the last 20 years for the development of Tobramycin nanosized delivery systems (nanoantibiotics), with critical discussion and comparison. Tobramycin was selected as the antimicrobial drug because it is a wide-spectrum antibiotic that is effective against both Gram-positive and Gram-negative aerobic bacteria, and it is characterized by a fast bactericidal effect, even against multidrug-resistant microorganisms (MDR).

Degradable and Non-Degradable Chondroitin Sulfate Particles with the Controlled Antibiotic Release for Bacterial Infections

Non-degradable, slightly degradable, and completely degradable micro/nanoparticles derived from chondroitin sulfate (CS) were synthesized through crosslinking reactions at 50%, 40%, and 20% mole ratios, respectively. The CS particles with a 20% crosslinking ratio show total degradation within 48 h, whereas 50% CS particles were highly stable for up to 240 h with only 7.0 ± 2.8% weight loss in physiological conditions (pH 7.4, 37 °C). Tobramycin and amikacin antibiotics were encapsulated into non-degradable CS particles with high loading at 250 g/mg for the treatment of corneal bacterial ulcers. The highest release capacity of 92 ± 2% was obtained for CS-Amikacin particles with sustainable and long-term release profiles. The antibacterial effects of CS particles loaded with 2.5 mg of antibiotic continued to render a prolonged release time of 240 h with 24 ± 2 mm inhibition zones against Pseudomonas aeruginosa. Furthermore, as a carrier, CS particles significantly improved the compatibility of the antibiotics even at high particle concentrations of 1000 g/mL with a minimum of 71 ± 7% fibroblast cell viability. In summary, the sustainable delivery of antibiotics and long-term treatment of bacterial keratitis were shown to be afforded by the design of tunable degradation ability of CS particles with improved biocompatibility for the encapsulated drugs.

Effects of Mucin and DNA Concentrations in Airway Mucus on Pseudomonas aeruginosa Biofilm Recalcitrance

The pathological properties of airway mucus in cystic fibrosis (CF) are dictated by mucus concentration and composition, with mucins and DNA being responsible for mucus viscoelastic properties. As CF pulmonary disease progresses, the concentrations of mucins and DNA increase and are associated with increased mucus viscoelasticity and decreased transport. Similarly, the biophysical properties of bacterial biofilms are heavily influenced by the composition of their extracellular polymeric substances (EPS). While the roles of polymer concentration and composition in mucus and biofilm mechanical properties have been evaluated independently, the relationship between mucus concentration and composition and the biophysical properties of biofilms grown therein remains unknown. Pseudomonas aeruginosa biofilms were grown in airway mucus as a function of overall concentration and DNA concentration to mimic healthy, and CF pathophysiology and biophysical properties were evaluated with macro- and microrheology. Biofilms were also characterized after exposure to DNase or DTT to examine the effects of DNA and mucin degradation, respectively. Identifying critical targets in biofilms for disrupting mechanical stability in highly concentrated mucus may lead to the development of efficacious biofilm therapies and ultimately improve CF patient outcomes. Overall mucus concentration was the predominant contributor to biofilm viscoelasticity and both DNA degradation and mucin reduction resulted in compromised biofilm mechanical strength.

IMPORTANCE Pathological mucus in cystic fibrosis (CF) is highly concentrated and insufficiently cleared from the airway, causing chronic inflammation and infection. Pseudomonas aeruginosa establishes chronic infection in the form of biofilms within mucus, and this study determined that biofilms formed in more concentrated mucus were more robust and less susceptible to mechanical and chemical challenges compared to biofilms grown in lower concentrated mucus. Neither DNA degradation nor disulfide bond reduction was sufficient to fully degrade biofilms. Mucus rehydration should remain a priority for treating CF pulmonary disease with concomitant multimechanistic biofilm degradation agents and antibiotics to clear chronic infection.

Targeting mucus barrier in respiratory diseases by chemically modified advanced delivery systems

Mucus gel constitutes of heavily cross-linked mucin fibers forming a viscoelastic, dense porous network that coats all the exposed epithelia not covered with the skin. The layer provides protection to the underlying gastrointestinal, respiratory, and female reproductive tracts, in addition to the organs such as the surface of eye by trapping the pathogens, irritants, environmental fine particles, and potentially hazardous foreign matter. However, this property of mucus gel poses a substantial challenge for realizing the localized and sustained drug delivery across the mucosal surfaces. The mucus permeating particles that spare the protective properties of mucus gel improve the therapeutic potency of the drugs aimed at the management of diseases, including sexually transmitted infections, lung cancer, irritable bowel disease, degenerative eye diseases and infections, and cystic fibrosis. As such, the mucoadhesive materials conjugated with drug molecules display a prolonged retention time in the mucosal gel that imparts a sustained release of the deliberated drug molecules across the mucosa. The contemporarily developed mucus penetrating materials for drug delivery applications comprise of a finer size, appreciable hydrophilicity, and a neutral surface to escape the entrapment within the cross-inked mucus fibers. Pertaining to the mucus secretion as a first line of defence in respiratory tract in response to the invading physical, chemical, and biological pathogens, the development of mucus penetrating materials hold promise as a stalwart approach for revolutionizing the respiratory drug delivery paradigm. The present review provides an epigrammatic collation of the mucus penetrating/mucoadhesive materials for achieving a controlled/sustained release of the cargo pharmaceutics and drug molecules across the respiratory mucus barrier.

Neutralization of ionic interactions by dextran-based single-chain nanoparticles improves tobramycin diffusion into a mature biofilm

The extracellular matrix protects biofilm cells by reducing diffusion of antimicrobials. Tobramycin is an antibiotic used extensively to treat P. aeruginosa biofilms, but it is sequestered in the biofilm periphery by the extracellular negative charge matrix and loses its efficacy significantly. Dispersal of the biofilm extracellular matrix with enzymes such as DNase I is another promising therapy that enhances antibiotic diffusion into the biofilm. Here, we combine the charge neutralization of tobramycin provided by dextran-based single-chain polymer nanoparticles (SCPNs) together with DNase I to break the biofilm matrix. Our study demonstrates that the SCPNs improve the activity of tobramycin and DNase I by neutralizing the ionic interactions that keep this antibiotic in the biofilm periphery. Moreover, the detailed effects and interactions of nanoformulations with extracellular matrix components were revealed through time-lapse imaging of the P. aeruginosa biofilms by laser scanning confocal microscopy with specific labeling of the different biofilm components.

Biological chemotaxis-guided self-thermophoretic nanoplatform augments colorectal cancer therapy through autonomous mucus penetration

Oral drug delivery systems have great potential to treat colorectal cancer (CRC). However, the drug delivery efficiency is restricted by limited CRC-related intestine positioning and dense mucus barrier. Here, we present a biological chemotaxis-guided self-thermophoretic nanoplatform that facilitates precise intestinal positioning and autonomous mucus penetration. The nanoplatform introduces asymmetric platinum-sprayed mesoporous silica to achieve autonomous movement in intestinal mucus. Furthermore, inspired by the intense interaction between pathogenic microbes and CRC, the nanoplatform is camouflaged by Staphylococcus aureus membrane to precisely anchor in CRC-related intestine. Owing to 4.3-fold higher biological chemotactic anchoring of CRC-related intestine and 14.6-fold higher autonomous mucus penetration performance, the nanoplatform vastly improves the oral bioavailability of cisplatin, leading to a tumor inhibition rate of 99.1% on orthotopic CRC-bearing mice. Together, the exquisitely designed nanoplatform to overcome multiple physiological barriers provides a new horizon for the development of oral drug delivery systems.

Dry powder inhalers of antitubercular drugs

Despite advancements in the medical and pharmaceutical fields, tuberculosis remains a major health problem globally. Patients do not widely accept the conventional approach to treating tuberculosis (TB) due to prolonged treatment periods with multiple high doses of drugs and associated side effects. A pulmonary route is a non-invasive approach to delivering drugs, hormones, nucleic acid, steroids, proteins, and peptides directly to the lungs, improving the efficacy of the treatment and consequently decreasing the adverse effect of the treatment. This route has been successfully developed for the treatment of various respiratory diseases such as asthma, chronic obstructive pulmonary disease (COPD), tuberculosis (TB), lung cancer, and other pulmonary infections. The major approaches of inhalation delivery systems include nebulizers, metered-dose inhalers (MDIs), and dry powder inhalers (DPIs). However, dry powder inhalers (DPIs) are more advantageous due to their stability and ability to deliver a high dose of the drug to the lungs. The present review analyzes the modern therapeutic approach of inhaled dry powders, with a special focus on novel drug delivery system (NDDS) based DPIs for the treatment of TB. The article also discussed the challenges of preparing inhalable dry powder formulations for the treatment of TB. The clinical development of inhalable anti-TB drugs is also reviewed.

Pulmonary delivery nanomedicines towards circumventing physiological barriers: Strategies and characterization approaches

Pulmonary delivery of nanomedicines is very promising in lung local disease treatments whereas several physiological barriers limit its application via the interaction with inhaled nanomedicines, namely bio-nano interactions. These bio-nano interactions may affect the pulmonary fate of nanomedicines and impede the distribution of nanomedicines in its targeted region, and subsequently undermine the therapeutic efficacy. Pulmonary diseases are under worse scenarios as the altered physiological barriers generally induce stronger bio-nano interactions. To mitigate the bio-nano interactions and regulate the pulmonary fate of nanomedicines, a number of manipulating strategies were established based on size control, surface modification, charge tuning and co-delivery of mucolytic agents. Visualized and non-visualized characterizations can be employed to validate the robustness of the proposed strategies. This review provides a guiding overview of the physiological barriers affecting the in vivo fate of inhaled nanomedicines, the manipulating strategies, and the validation methods, which will assist with the rational design and application of pulmonary nanomedicine.

Nanostructures for drug delivery in respiratory diseases therapeutics: Revision of current trends and its comparative analysis

Respiratory diseases are leading causes of death and disability in developing and developed countries. The burden of acute and chronic respiratory diseases has been rising throughout the world and represents a major problem in the public health system. Acute respiratory diseases include pneumonia, influenza, SARS-CoV-2 and MERS viral infections; while chronic obstructive pulmonary disease (COPD), asthma and, occupational lung diseases (asbestosis, pneumoconiosis) and other parenchymal lung diseases namely lung cancer and tuberculosis are examples of chronic respiratory diseases. Importantly, chronic respiratory diseases are not curable and treatments for acute pathologies are particularly challenging. For that reason, the integration of nanotechnology to existing drugs or for the development of new treatments potentially benefits the therapeutic goals by making drugs more effective and exhibit fewer undesirable side effects to treat these conditions. Moreover, the integration of different nanostructures enables improvement of drug bioavailability, transport and delivery compared to stand-alone drugs in traditional respiratory therapy. Notably, there has been great progress in translating nanotechnology-based cancer therapies and diagnostics into the clinic; however, researchers in recent years have focused on the application of nanostructures in other relevant pulmonary diseases as revealed in our database search. Furthermore, polymeric nanoparticles and micelles are the most studied nanostructures in a wide range of diseases; however, liposomal nanostructures are recognized to be some of the most successful commercial drug delivery systems. In conclusion, this review presents an overview of the recent and relevant research in drug delivery systems for the treatment of different pulmonary diseases and outlines the trends, limitations, importance and application of nanomedicine technology in treatment and diagnosis and future work in this field.

Antibacterial Efficacies of Nanostructured Aminoglycosides

The widespread use of broad-spectrum aminoglycoside antibiotics is restricted from various clinical applications due to the emergence of bacterial resistance and the adverse effects such as ototoxicity and nephrotoxicity. The intensive applicability of nanoparticles in modern medicinal chemistry has gained the interest of researchers for modification of aminoglycosides as nanoconjugates either via covalent conjugation or physical interactions to alleviate their undesirable effects and bacterial resistance. In this context, various carbohydrates, polymers, lipids, silver, gold, and silica-attached aminoglycoside nanoparticles have been reported with improvements in physicochemical properties, bioavailability, and biocompatibility in physiological medium. Overall, this review encompassed the synthesis of nanostructured aminoglycosides and their applications in the development of new antibacterial therapeutics.

Extracts of Sida cordifolia contain polysaccharides possessing immunomodulatory activity and rosmarinic acid compounds with antibacterial activity

BACKGROUND

The overuse of antibiotics has led to increased antimicrobial resistance, but plant-derived biological response modifiers represent a potential alternative to these drugs. This investigation examined the immunomodulatory and antibacterial activities of Sida cordifolia (used in ethnomedicinal systems to treat infectious disease).

METHODS

Successive extractions were performed from the roots of these plants in hexane, chloroform, methanol and water. Immunomodulatory activity was determined in a series of experiments measuring the responses of splenocytes, macrophages and an in vivo model of innate immunity (Galleria mellonella). Antibacterial activity was assessed by determining minimum inhibitory/bactericidal concentrations (MIC/MBCs) for various Gram-positive and Gram-negative bacterial strains.

RESULTS

Immunomodulatory activity was confined to the aqueous extract, and further fractionation and biochemical analysis yielded a highly potent polysaccharide-enriched fraction (SCAF5). SCAF5 is a complex mixture of different polysaccharides with multiple immunomodulatory effects including immune cell proliferation, antibody secretion, phagocytosis, nitric oxide production, and increased expression of pro-inflammatory cytokines. Furthermore, Galleria mellonella pre-treated with SCAF5 produced more haemocytes and were more resistant (P < 0.001) to infection with methicillin-resistant Staphylococcus aureus (MRSA) with a 98% reduction in bacterial load in pre-treated larvae compared to the negative control. The antibacterial activity of Sida cordifolia was confined to the methanolic fraction. Extensive fractionation identified two compounds, rosmarinic acid and its 4-O-β-d-glucoside derivative, which had potent activity against Gram-positive antibiotic-resistant bacteria, including MRSA.

CONCLUSIONS

Sida cordifolia counters bacterial infections through a dual mechanism, and immunomodulatory polysaccharides from this plant should be isolated and characterised to realise their potential as anti-infective agents. Such properties could be developed as an antibiotic alternative (1) in the clinic and (2) alternative growth promoter for the agri-food industry.

Plant-derived nanotherapeutic systems to counter the overgrowing threat of resistant microbes and biofilms

Since antiquity, the survival of human civilization has always been threatened by the microbial infections. An alarming surge in the resistant microbial strains against the conventional drugs is quite evident in the preceding years. Furthermore, failure of currently available regimens of antibiotics has been highlighted by the emerging threat of biofilms in the community and hospital settings. Biofilms are complex dynamic composites rich in extracellular polysaccharides and DNA, supporting plethora of symbiotic microbial life forms, that can grow on both living and non-living surfaces. These enforced structures are impervious to the drugs and lead to spread of recurrent and non-treatable infections. There is a strong realization among the scientists and healthcare providers to work out alternative strategies to combat the issue of drug resistance and biofilms. Plants are a traditional but rich source of effective antimicrobials with wider spectrum due to presence of multiple constituents in perfect synergy. Other than the biocompatibility and the safety profile, these phytochemicals have been repeatedly proven to overcome the non-responsiveness of resistant microbes and films via multiple pathways such as blocking the efflux pumps, better penetration across the cell membranes or biofilms, and anti-adhesive properties. However, the unfavorable physicochemical attributes and stability issues of these phytochemicals have hampered their commercialization. These issues of the phytochemicals can be solved by designing suitably constructed nanoscaled structures. Nanosized systems can not only improve the physicochemical features of the encapsulated payloads but can also enhance their pharmacokinetic and therapeutic profile. This review encompasses why and how various types of phytochemicals and their nanosized preparations counter the microbial resistance and the biofouling. We believe that phytochemical in tandem with nanotechnological innovations can be employed to defeat the microbial resistance and biofilms. This review will help in better understanding of the challenges associated with developing such platforms and their future prospects.

Nanomedicine to advance the treatment of bacteria-induced acute lung injury

Bacteria-induced acute lung injury (ALI) is associated with a high mortality rate due to the lack of an effective treatment. Patients often rely on supportive care such as low tidal volume ventilation to alleviate the symptoms. Nanomedicine has recently received much attention owing to its premium benefits of delivering drugs in a sustainable and controllable manner while minimizing the potential side effects. It can effectively improve the prognosis of bacteria-induced ALI through targeted delivery of drugs, regulation of multiple inflammatory pathways, and combating antibiotic resistance. Hence, in this review, we first discuss the pathogenesis of ALI and its potential therapeutics. In particular, the state-of-the-art nanomedicines for the treatment of bacteria-induced ALI are highlighted, including their administration routes, in vivo distribution, and clearance. Furthermore, the available bacteria-induced ALI animal models are also summarized. In the end, future perspectives of nanomedicine for ALI treatment are proposed.

Challenges and solutions in polymer drug delivery for bacterial biofilm treatment: A tissue-by-tissue account

To tackle the emerging antibiotic resistance crisis, novel antimicrobial approaches are urgently needed. Bacterial communities (biofilms) are a particular concern in this context. Biofilms are responsible for most human infections and are inherently less susceptible to antibiotic treatments. Biofilms have been linked with several challenging chronic diseases, including implant-associated osteomyelitis and chronic wounds. The specific local environments present in the infected tissues further contribute to the rise in antibiotic resistance by limiting the efficacy of systemic antibiotic therapies and reducing drug concentrations at the infection site, which can lead to reoccurring infections. To overcome the shortcomings of systemic drug delivery, encapsulation within polymeric carriers has been shown to enhance antimicrobial efficacy, permeation and retention at the infection site. In this Review, we present an overview of current strategies for antimicrobial encapsulation within polymeric carriers, comparing challenges and solutions on a tissue-by-tissue basis. We compare challenges and proposed drug delivery solutions from the perspective of the local environments for biofilms found in oral, wound, gastric, urinary tract, bone, pulmonary, vaginal, ocular and middle/inner ear tissues. We will also discuss future challenges and barriers to clinical translation for these therapeutics. The following Review demonstrates there is a significant imbalance between the research focus being placed on different tissue types, with some targets (oral and wound biofims) being extensively more studied than others (vaginal and otitis media biofilms and endocarditis). Furthermore, the importance of the local tissue environment when selecting target therapies is demonstrated, with some materials being optimal choices for certain sites of bacterial infection, while having limited applicability in others.

Combined Treatment of 6-Gingerol Analog and Tobramycin for Inhibiting Pseudomonas aeruginosa Infections

Pseudomonas aeruginosa is a ubiquitous human pathogen that causes severe infections. Although antibiotics, such as tobramycin, are currently used for infection therapy, their antibacterial activity has resulted in the emergence of multiple antibiotic-resistant bacteria. The 6-gingerol analog, a structural derivative of the main component of ginger, is a quorum sensing (QS) inhibitor. However, it has a lower biofilm inhibitory activity than antibiotics and the possibility to cause toxicity in humans. Therefore, novel and more effective approaches for decreasing dosing concentration and increasing biofilm inhibitory activity are required to alleviate P. aeruginosa infections. In this study, a 6-gingerol analog was combined with tobramycin to treat P. aeruginosa infections. The combined treatment of 6-gingerol analog and tobramycin showed strong inhibitory activities on biofilm formation and the production of QS-related virulence factors of P. aeruginosa compared to single treatments. Furthermore, the combined treatment alleviated the infectivity of P. aeruginosa in an insect model using Tenebrio molitor larvae without inducing any cytotoxic effects in human lung epithelial cells. The 6-gingerol analog showed these inhibitory activities at much lower concentrations when used in combination with tobramycin. Adjuvant effects were observed through increased QS-disrupting processes rather than through antibacterial action. In particular, improved RhlR inactivation by this combination is a possible target for therapeutic development in LasR-independent chronic infections. Therefore, the combined treatment of 6-gingerol analog and tobramycin may be considered an effective method for treating P. aeruginosa infections. IMPORTANCE Pseudomonas aeruginosa is a pathogen that causes various infectious diseases through quorum-sensing regulation. Although antibiotics are mainly used to treat P. aeruginosa infections, they cause the emergence of resistant bacteria in humans. To compensate for the disadvantages of antibiotics and increase their effectiveness, natural products were used in combination with antibiotics in this study. We discovered that combined treatment with 6-gingerol analog from naturally-derived ginger substances and tobramycin resulted in more effective reductions of biofilm formation and virulence factor production in P. aeruginosa than single treatments. Our findings support the notion that when 6-gingerol analog is combined with tobramycin, the effects of the analog can be exerted at much lower concentrations. Furthermore, its improved LasR-independent RhlR inactivation may serve as a key target for therapeutic development in chronic infections. Therefore, the combined treatment of 6-gingerol analog and tobramycin is suggested as a novel alternative for treating P. aeruginosa infections.

Current and Emerging Therapies to Combat Cystic Fibrosis Lung Infections

The ultimate aim of any antimicrobial treatment is a better infection outcome for the patient. Here, we review the current state of treatment for bacterial infections in cystic fibrosis (CF) lung while also investigating potential new treatments being developed to see how they may change the dynamics of antimicrobial therapy. Treatment with antibiotics coupled with regular physical therapy has been shown to reduce exacerbations and may eradicate some strains. Therapies such as hypertonic saline and inhaled Pulmozyme^TM (DNase-I) improve mucus clearance, while modifier drugs, singly and more successfully in combination, re-open certain mutant forms of the cystic fibrosis transmembrane conductance regulator (CFTR) to enable ion passage. No current method, however, completely eradicates infection, mainly due to bacterial survival within biofilm aggregates. Lung transplants increase lifespan, but reinfection is a continuing problem. CFTR modifiers normalise ion transport for the affected mutations, but there is conflicting evidence on bacterial clearance. Emerging treatments combine antibiotics with novel compounds including quorum-sensing inhibitors, antioxidants, and enzymes, or with bacteriophages, aiming to disrupt the biofilm matrix and improve antibiotic access. Other treatments involve bacteriophages that target, infect and kill bacteria. These novel therapeutic approaches are showing good promise in vitro, and a few have made the leap to in vivo testing.

Hyaluronan/Diethylaminoethyl Chitosan Polyelectrolyte Complexes as Carriers for Improved Colistin Delivery

Improving the therapeutic characteristics of antibiotics is an effective strategy for controlling the growth of multidrug-resistant Gram-negative microorganisms. The purpose of this study was to develop a colistin (CT) delivery system based on hyaluronic acid (HA) and the water-soluble cationic chitosan derivative, diethylaminoethyl chitosan (DEAECS). The CT delivery system was a polyelectrolyte complex (PEC) obtained by interpolymeric interactions between the HA polyanion and the DEAECS polycation, with simultaneous inclusion of positively charged CT molecules into the resulting complex. The developed PEC had a hydrodynamic diameter of 210-250 nm and a negative surface charge (ζ-potential = -19 mV); the encapsulation and loading efficiencies were 100 and 16.7%, respectively. The developed CT delivery systems were characterized by modified release (30-40% and 85-90% of CT released in 15 and 60 min, respectively) compared to pure CT (100% CT released in 15 min). In vitro experiments showed that the encapsulation of CT in polysaccharide carriers did not reduce its antimicrobial activity, as the minimum inhibitory concentrations against Pseudomonas aeruginosa of both encapsulated CT and pure CT were 1 μg/mL.

Eradicating biofilm infections: an update on current and prospective approaches

Biofilm formation is a multifactorial process and often a multi-species endeavour that involves complex signalling networks, chemical gradients, bacterial adhesion, and production or acquisition of matrix components. Antibiotics remain the main choice when treating bacterial biofilm-associated infections despite their intrinsic tolerance to antimicrobials, and propensity for acquisition and rapid dissemination of antimicrobial resistance within the biofilm. Eliminating hard to treat biofilm-associated infections that are antibiotic resistant will demand a holistic and multi-faceted approach, targeting multiple stages of biofilm formation, many of which are already in development. This mini review will highlight the current approaches that are employed to treat bacterial biofilm infections and discuss new approaches in development that have promise to reach clinical practice.

Hyaluronan/colistin polyelectrolyte complexes: Promising antiinfective drug delivery systems

Nanotechnology-based modification of known antimicrobial agents is a rational and straightforward way to improve their safety and effectiveness. The aim of this study was to develop colistin (CT)-loaded polymeric carriers based on hyaluronic acid (HA) for potential application as antimicrobial agents against multi-resistant gram-negative microorganisms (including ESKAPE pathogens). CT-containing particles were obtained via a polyelectrolyte interaction between protonated CT amino groups and HA carboxyl groups (the CT-HA complex formation constant [logK_CT-HA] was about 5.0). The resulting polyelectrolyte complexes had a size of 210-250 nm and a negative charge (ζ-potential -19 mV), with encapsulation and loading efficiencies of 100% and 20%, respectively. The developed CT delivery systems were characterized by modified release (45% and 85% of CT released in 15 and 60 min, respectively) compared to pure CT (100% CT released in 15 min). In vitro tests showed that the encapsulation of CT in polymer particles did not reduce its pharmacological activity; the minimum inhibitory concentrations of both encapsulated CT and pure CT were 1 μg/mL (against Pseudomonas aeruginosa).

Polymeric nano- and microparticulate drug delivery systems for treatment of biofilms

Now-a-days healthcare systems face great challenges with antibiotic resistance and low efficacy of antibiotics when combating pathogenic bacteria and bacterial biofilms. Administration of an antibiotic in its free form is often ineffective due to lack of selectivity to the infectious site and breakdown of the antibiotic before it exerts its effect. Therefore, polymeric delivery systems, where the antibiotic is encapsulated into a formulation, have shown great promise, facilitating a high local drug concentration at the site of infection, a controlled drug release and less drug degradation. All this leads to improved therapeutic effects and fewer systemic side effects together with a lower risk of developing antibiotic resistance. Here, we review and provide a comprehensive overview of polymer-based nano- and microparticles as carriers for antimicrobial agents and their effect on eradicating bacterial biofilms. We have a main focus on polymeric particulates containing poly(lactic-co-glycolic acid), chitosan and polycaprolactone, but also strategies involving combinations of these polymers are included. Different production techniques are reviewed and important parameters for biofilm treatment are discussed such as drug loading capacity, control of drug release, influence of particle size and mobility in biofilms. Additionally, we reflect on other promising future strategies for combating biofilms such as lipid-polymer hybrid particles, enzymatic biofilm degradation, targeted/triggered antibiotic delivery and future alternatives to the conventional particles.

Recent developments in biomolecule-based nanoencapsulation systems for antimicrobial delivery and biofilm disruption

Biomolecules are very attractive nanomaterial components, generally, due to their biocompatibility, biodegradability, abundance, renewability, and sustainability, as compared to other resources for nanoparticle-based delivery systems. Biomolecule-based nanoencapsulation and nanodelivery systems can be designed and engineered for antimicrobial cargos in order to surmount classical and current challenges, including the emergence of multi-drug resistant strains of microorganisms, the low effectiveness and limitations in the applicability of the present antimicrobials, and biofilm formation. This feature article highlights the recent applications and capabilities of biomacromolecule-based nanomaterials for the delivery and activity enhancement of antimicrobials, and disruption of biofilms. Unique properties of some nanomaterials, arising from specific biomacromolecules, were also emphasized. We expect that this review will be helpful to researchers in engineering new types of antimicrobial nanocarriers, hybrid particles and colloidal systems with tailored properties.

Strategies to load therapeutics into polysaccharide-based nanogels with a focus on microfluidics: A review

Nowadays nanoparticles are increasingly investigated for the targeted and controlled delivery of therapeutics, as suggested by the high number of research articles (2400 in 2000 vs 8500 in 2020). Among them, almost 2% investigated nanogels in 2020. Nanogels or nanohydrogels (NGs) are nanoparticles formed by a swollen three-dimensional network of synthetic polymers or natural macromolecules such as polysaccharides. NGs represent a highly versatile nanocarrier, able to deliver a number of therapeutics. Currently, NGs are undergoing clinical trials for the delivery of anti-cancer vaccines. Herein, the strategies to load low molecular weight drugs, (poly)peptides and genetic material into polysaccharide NGs as well as to formulate NGs-based vaccines are summarized, with a focus on the microfluidics approach.

Cystic Fibrosis: Recent Insights into Inhaled Antibiotic Treatment and Future Perspectives

Although new inhaled antibiotics have profoundly improved respiratory diseases in cystic fibrosis (CF) patients, lung infections are still the leading cause of death. Inhaled antibiotics, i.e., colistin, tobramycin, aztreonam lysine and levofloxacin, are used as maintenance treatment for CF patients after the development of chronic Pseudomonas aeruginosa (P. aeruginosa) infection. Their use offers advantages over systemic therapy since a relatively high concentration of the drug is delivered directly to the lung, thus, enhancing the pharmacokinetic/pharmacodynamic parameters and decreasing toxicity. Notably, alternating treatment with inhaled antibiotics represents an important strategy for improving patient outcomes. The prevalence of CF patients receiving continuous inhaled antibiotic regimens with different combinations of the anti-P. aeruginosa antibiotic class has been increasing over time. Moreover, these antimicrobial agents are also used for preventing acute pulmonary exacerbations in CF. In this review, the efficacy and safety of the currently available inhaled antibiotics for lung infection treatment in CF patients are discussed, with a particular focus on strategies for eradicating P. aeruginosa and other pathogens. Moreover, the effects of long-term inhaled antibiotic therapy for chronic P. aeruginosa infection and for the prevention of pulmonary exacerbations is reviewed. Finally, how the mucus environment and microbial community richness can influence the efficacy of aerosolized antimicrobial agents is discussed.

Nanoparticle-mediated pulmonary drug delivery: state of the art towards efficient treatment of recalcitrant respiratory tract bacterial infections

Recalcitrant respiratory tract infections caused by bacteria have emerged as one of the greatest health challenges worldwide. Aerosolized antimicrobial therapy is becoming increasingly attractive to combat such infections, as it allows targeted delivery of high drug concentrations to the infected organ while limiting systemic exposure. However, successful aerosolized antimicrobial therapy is still challenged by the diverse biological barriers in infected lungs. Nanoparticle-mediated pulmonary drug delivery is gaining increasing attention as a means to overcome the biological barriers and accomplish site-specific drug delivery by controlling release of the loaded drug(s) at the target site. With the aim to summarize emerging efforts in combating respiratory tract infections by using nanoparticle-mediated pulmonary delivery strategies, this review provides a brief introduction to the bacterial infection-related pulmonary diseases and the biological barriers for effective treatment of recalcitrant respiratory tract infections. This is followed by a summary of recent advances in design of inhalable nanoparticle-based drug delivery systems that overcome the biological barriers and increase drug bioavailability. Finally, challenges for the translation from exploratory laboratory research to clinical application are also discussed and potential solutions proposed.

Enhancing nanoparticle penetration through airway mucus to improve drug delivery efficacy in the lung

Introduction: Airway mucus gel layer serves as a key delivery barrier that limits the performance of inhaled drug delivery nanoparticles. Conventional nanoparticles are readily trapped by the airway mucus and rapidly cleared from the lung via mucus clearance mechanisms. These nanoparticles cannot distribute throughout the lung airways, long-reside in the lung and/or reach the airway epithelium. To address this challenge, strategies to enhance particle penetration through the airway mucus have been developed and proof-of-concept has been established using mucus model systems..Areas covered: In this review, we first overview the biochemical and biophysical characteristics that render the airway mucus a challenging delivery barrier. We then introduce strategies to improve particle penetration through the airway mucus. Specifically, we walk through two classes of approaches, including modification of physicochemical properties of nanoparticles and modulation of barrier properties of airway mucus.Expert opinion: State-of-the-art strategies to overcome the airway mucus barrier have been introduced and experimentally validated. However, data should be interpreted in the comprehensive context of therapeutic delivery from the site of administration to the final destination to determine clinically-relevant approaches. Further, safety should be carefully monitored, particularly when it comes to mucus-altering strategies that may perturb physiological functions of airway mucus.

Pseudomonas aeruginosa Biofilms

Pseudomonas aeruginosa is an opportunistic human pathogen causing devastating acute and chronic infections in individuals with compromised immune systems. Its highly notorious persistence in clinical settings is attributed to its ability to form antibiotic-resistant biofilms. Biofilm is an architecture built mostly by autogenic extracellular polymeric substances which function as a scaffold to encase the bacteria together on surfaces, and to protect them from environmental stresses, impedes phagocytosis and thereby conferring the capacity for colonization and long-term persistence. Here we review the current knowledge on P. aeruginosa biofilms, its development stages, and molecular mechanisms of invasion and persistence conferred by biofilms. Explosive cell lysis within bacterial biofilm to produce essential communal materials, and interspecies biofilms of P. aeruginosa and commensal Streptococcus which impedes P. aeruginosa virulence and possibly improves disease conditions will also be discussed. Recent research on diagnostics of P. aeruginosa infections will be investigated. Finally, therapeutic strategies for the treatment of P. aeruginosa biofilms along with their advantages and limitations will be compiled.

State-of-the-art polymeric nanoparticles as promising therapeutic tools against human bacterial infections

Infectious diseases kill over 17 million people a year, among which bacterial infections stand out. From all the bacterial infections, tuberculosis, diarrhoea, meningitis, pneumonia, sexual transmission diseases and nosocomial infections are the most severe bacterial infections, which affect millions of people worldwide. Moreover, the indiscriminate use of antibiotic drugs in the last decades has triggered an increasing multiple resistance towards these drugs, which represent a serious global socioeconomic and public health risk. It is estimated that 33,000 and 35,000 people die yearly in Europe and the United States, respectively, as a direct result of antimicrobial resistance. For all these reasons, there is an emerging need to find novel alternatives to overcome these issues and reduced the morbidity and mortality associated to bacterial infectious diseases. In that sense, nanotechnological approaches, especially smart polymeric nanoparticles, has wrought a revolution in this field, providing an innovative therapeutic alternative able to improve the limitations encountered in available treatments and capable to be effective by theirselves. In this review, we examine the current status of most dangerous human infections, together with an in-depth discussion of the role of nanomedicine to overcome the current disadvantages, and specifically the most recent and innovative studies involving polymeric nanoparticles against most common bacterial infections of the human body.

Multi-Omics Approaches: The Key to Improving Respiratory Health in People With Cystic Fibrosis?

The advent of high-throughput multi-omics technologies has underpinned the expansion in lung microbiome research, increasing our understanding of the nature, complexity and significance of the polymicrobial communities harbored by people with CF (PWCF). Having established that structurally complex microbial communities exist within the airways, the focus of recent research has now widened to investigating the function and dynamics of the resident microbiota during disease as well as in health. With further refinement, multi-omics approaches present the opportunity to untangle the complex interplay between microbe-microbe and microbe-host interactions in the lung and the relationship with respiratory disease progression, offering invaluable opportunities to discover new therapeutic approaches for our management of airway infection in CF.

Current Status of Alginate in Drug Delivery

Alginate is one of the natural polymers that are often used in drug- and protein-delivery systems. The use of alginate can provide several advantages including ease of preparation, biocompatibility, biodegradability, and nontoxicity. It can be applied to various routes of drug administration including targeted or localized drug-delivery systems. The development of alginates as a selected polymer in various delivery systems can be adjusted depending on the challenges that must be overcome by drug or proteins or the system itself. The increased effectiveness and safety of sodium alginate in the drug- or protein-delivery system are evidenced by changing the physicochemical characteristics of the drug or proteins. In this review, various routes of alginate-based drug or protein delivery, the effectivity of alginate in the stem cells, and cell encapsulation have been discussed. The recent advances in the in vivo alginate-based drug-delivery systems as well as their toxicities have also been reviewed.

Successes and Challenges: Inhaled Treatment Approaches Using Magnetic Nanoparticles in Cystic Fibrosis

Magnetic nanoparticles have been largely applied to increase the efficacy of antibiotics due to passive accumulation provided by enhancing permeability and retention, which is essential for the treatment of lung infections. Recurring lung infections such as in the life-shortening genetic disease cystic fibrosis (CF) are a major problem. The recent advent of the CF modulator drug ivacaftor, alone or in combination with lumacaftor or tezacaftor, has enabled systemic treatment of the majority of patients. Magnetic nanoparticles (MNPs) show unique properties such as biocompatibility and biodegradability as well as magnetic and heat-medicated characteristics. These properties make them suitable to be used as drug carriers and hyperthermia-based agents. Hyperthermia is a promising approach for the thermal activation therapy of several diseases, including pulmonary diseases. The benefits of delivering CF drugs via inhalation using MNPs as drug carriers afford application of sufficient therapeutic dosages directly to the primary target site, while avoiding potential suboptimal pharmacokinetics/pharmacodynamics and minimizing the risks of systemic toxicity. This review explores the multidisciplinary approach of using MNPs as vehicles of drug delivery. Additionally, we highlight advantages such as increased drug concentration at disease site, minimized drug loss and the possibility of specific cell targeting, while addressing major challenges for this emerging field.

Ternary nanoparticle complex of antibiotic, polyelectrolyte, and mucolytic enzyme as a potential antibiotic delivery system in bronchiectasis therapy

Antibiotic-polyelectrolyte nanoparticle complex (or nanoplex in short) has been recently demonstrated as a superior antibiotic delivery system to the native antibiotic in bronchiectasis therapy owed to its ability to overcome the lung's mucus barrier and generate high localized antibiotic exposure in the infected sites. The present work aimed to further improve the mucus permeability, hence the antibacterial efficacy of the nanoplex, by incorporating mucolytic enzyme papain (PAP) at the nanoplex formation step to produce PAP-decorated antibiotic-polyelectrolyte nanoplex exhibiting built-in mucolytic capability. Ciprofloxacin (CIP) and dextran sulfate (DXT) were used as the models for antibiotics and polyelectrolyte, respectively. The results showed that the PAP inclusion had minimal effects on the physical characteristics, preparation efficiency, and dissolution of the CIP-DXT nanoplex. The optimal CIP-(DXT-PAP) nanoplex exhibited size and zeta potential of approximately 200 nm and -50 mV with CIP and PAP payloads of 60% and 32% (w/w), respectively. The nanoplex was prepared at high efficiency with larger than 80% CIP and PAP utilization rates. The CIP-(DXT-PAP) nanoplex exhibited tenfold improvement in the mucus permeability compared to its CIP-DXT nanoplex counterpart, resulting in the former's superior bactericidal activity against clinical Pseudomonas aeruginosa biofilm in the presence of mucus barrier. A trade-off, nevertheless, existed between antibacterial efficacy and cytotoxicity towards human lung epithelium cells upon the incorporation of PAP above a certain concentration threshold. Therefore, the optimal dosing of the CIP-(DXT-PAP) nanoplex must be carefully determined.

Antibacterial and antifungal impacts of combined silver, zinc oxide, and chitosan nanoparticles within tissue conditioners of complete dentures in vitro

BACKGROUND

Tissue conditioners are suitable places for colonization of microorganisms. A combination of tissue conditioners with antibacterial and antifungal materials inhibits the growth of microorganisms.

AIMS

Here, we aimed to investigate the antibacterial and antifungal effects of silver (Ag), zinc oxide (ZnO), and chitosan nanoparticles on tissue conditioners in complete dentures.

METHODS

The growth of four microorganisms in six different concentrations of Ag, ZnO, and chitosan nanoparticles was investigated after 24 and 48 h. Nanoparticles were synthesized using optical sequestration and approved by scanning electron microscope, x-ray diffraction, and infrared (FT-IR) methods. Nanoparticles were combined at 0.5, 0.25, and 0.25 ratios (chitosan, Ag, and ZnO, respectively) with 0.625, 1.25, 2.5, 5, 10, and 20 mass percentages. Tissue conditioners with nanoparticles were entered to test tubes containing microorganisms, and the growth rate was measured using the turbidity method by spectrophotometer after 24 and 48 h of incubation at 37 °C.

RESULTS

Growth inhibition of Candida albicans occurred at 2.5% concentration. However, the growth inhibition of Streptococcus mutans, Enterococcus faecalis, and Pseudomonas aeruginosa occurred at 5% after both 24 and 48 h. Also, the optimum nanoparticle concentration for Candida albicans was found to be 1.25% for both timings. On the other hand, the optimum nanoparticle concentration for Streptococcus mutans, Enterococcus faecalis, and Pseudomonas aeruginosa was 2.5% for both time scales.

CONCLUSIONS

The combination of Ag, ZnO, and chitosan nanoparticles inhibited the growth of fungi and bacteria in tissue conditioners. These nanoparticles inhibited the growth of fungi more effectively than bacteria.

Polymyxin Delivery Systems: Recent Advances and Challenges

Polymyxins are vital antibiotics for the treatment of multiresistant Gram-negative ESKAPE pathogen infections. However, their clinical value is limited by their high nephrotoxicity and neurotoxicity, as well as their poor permeability and absorption in the gastrointestinal tract. This review focuses on various polymyxin delivery systems that improve polymyxin bioavailability and reduce drug toxicity through targeted and controlled release. Currently, the most suitable systems for improving oral, inhalation, and parenteral polymyxin delivery are polymer particles, liposomes, and conjugates, while gels, polymer fibers, and membranes are attractive materials for topical administration of polymyxin for the treatment of infected wounds and burns. In general, the application of these systems protects polymyxin molecules from the negative effects of both physiological and pathological factors while achieving higher concentrations at the target site and reducing dosage and toxicity. Improving the properties of polymyxin will be of great interest to researchers who are focused on developing antimicrobial drugs that show increased efficacy and safety.

Nano-Based Drug Delivery or Targeting to Eradicate Bacteria for Infection Mitigation: A Review of Recent Advances

Pathogenic bacteria infection is a major public health problem due to the high morbidity and mortality rates, as well as the increased expenditure on patient management. Although there are several options for antimicrobial therapy, their efficacy is limited because of the occurrence of drug-resistant bacteria. Many conventional antibiotics have failed to show significant amelioration in overall survival of infectious patients. Nanomedicine for delivering antibiotics provides an opportunity to improve the efficiency of the antibacterial regimen. Nanosystems used for antibiotic delivery and targeting to infection sites render some benefits over conventional formulations, including increased solubility, enhanced stability, improved epithelium permeability and bioavailability, prolonged antibiotic half-life, tissue targeting, and minimal adverse effects. The nanocarriers' sophisticated material engineering tailors the controllable physicochemical properties of the nanoparticles for bacterial targeting through passive or active targeting. In this review, we highlight the recent progress on the development of antibacterial nanoparticles loaded with antibiotics. We systematically introduce the concepts and amelioration mechanisms of the nanomedical techniques for bacterial eradication. Passive targeting by modulating the nanoparticle structure and the physicochemical properties is an option for efficient drug delivery to the bacteria. In addition, active targeting, such as magnetic hyperthermia induced by iron oxide nanoparticles, is another efficient way to deliver the drugs to the targeted site. The nanoparticles are also designed to respond to the change in environment pH or enzymes to trigger the release of the antibiotics. This article offers an overview of the benefits of antibacterial nanosystems for treating infectious diseases.