Poly(amidoamine) dendrimer-erythromycin conjugates for drug delivery to macrophages involved in periprosthetic inflammation

How Combined Macrolide Nanomaterials are Effective Against Resistant Pathogens? A Comprehensive Review of the Literature

Macrolide drugs are among the broad-spectrum antibiotics that are considered as "miracle drugs" against infectious diseases that lead to higher morbidity and mortality rates. Nevertheless, their effectiveness is currently at risk owing to the presence of devastating, antimicrobial-resistant microbes. In view of this challenge, nanotechnology-driven innovations are currently being anticipated for promising approaches to overcome antimicrobial resistance. Nowadays, various nanostructures are being developed for the delivery of antimicrobials to counter drug-resistant microbial strains through different mechanisms. Metallic nanoparticle-based delivery of macrolides, particularly using silver and gold nanoparticles (AgNPs & AuNPs), demonstrated a promising outcome with worthy stability, oxidation resistance, and biocompatibility. Similarly, macrolide-conjugated magnetic NPs resulted in an augmented antimicrobial activity and reduced bacterial cell viability against resistant microbes. Liposomal delivery of macrolides also showed favorable synergistic antimicrobial activities in vitro against resistant strains. Loading macrolide drugs into various polymeric nanomaterials resulted in an enhanced zone of inhibition. Intercalated nanomaterials also conveyed an outstanding macrolide delivery characteristic with efficient targeting and controlled drug release against infectious microbes. This review abridges several nano-based delivery approaches for macrolide drugs along with their recent achievements, challenges, and future perspectives.

Nano-based drug delivery system for therapeutics: a comprehensive review

Nanomedicine and nano-delivery systems hold unlimited potential in the developing sciences, where nanoscale carriers are employed to efficiently deliver therapeutic drugs at specifically targeted sites in a controlled manner, imparting several advantages concerning improved efficacy and minimizing adverse drug reactions. These nano-delivery systems target-oriented delivery of drugs with precision at several site-specific, with mild toxicity, prolonged circulation time, high solubility, and long retention time in the biological system, which circumvent the problems associated with the conventional delivery approach. Recently, nanocarriers such as dendrimers, liposomes, nanotubes, and nanoparticles have been extensively investigated through structural characteristics, size manipulation, and selective diagnosis through disease imaging molecules, which are very effective and introduce a new paradigm shift in drugs. In this review, the use of nanomedicines in drug delivery has been demonstrated in treating various diseases with significant advances and applications in different fields. In addition, this review discusses the current challenges and future directions for research in these promising fields as well.

Epsilon-poly-l-lysine conjugated erythromycin for enhanced antibiotic therapy

Antibiotic resistance is a big threat to public health. How to improve the therapeutic efficacy of conventional antibiotics is an effective way to address this issue. In order to enhance the antibacterial activity of conventional antibiotic erythromycin (EM), EM is conjugated to positively charged ε-poly-l-lysine (EPL) to obtain EPL modified EM (EPL-EM). The grafting ratio of EM can be calculated from the ¹H NMR spectrum. EPL-EM is stable in physiological environment, while EM can be readily released from EPL-EM upon incubating with esterase which can be secreted by most bacteria. Because of the presence of cationic EPL, EPL-EM showed much stronger antibacterial activity than free EM, with much lower minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Moreover, compared to free EM, the development of drug resistance can be slowed down if EPL-EM is used, which can be ascribed to the reduction of EM dosage. Meanwhile, EPL-EM cannot induce hemolysis and cytotoxicity, which indicates that EPL-EM exhibits excellent biocompatibility. The design of EPL-EM with enhanced antibacterial activity and excellent biocompatibility provides an innovative way to combat antibiotic resistance.

Phonophoresis through Nonsteroidal Anti-Inflammatory Drugs for Knee Osteoarthritis Treatment: Systematic Review and Meta-Analysis

Knee osteoarthritis (OA) is the most common joint disease. The administration of nonsteroidal anti-inflammatory drugs (NSAIDs) by phonophoresis is a therapeutic alternative to relieve pain in inflammatory pathologies. The main aim was to analyze the efficacy of the application of NSAIDs by phonophoresis in knee OA. A systematic review and meta-analysis of controlled clinical trials were performed between January and March 2021 in the following databases: Web of Science, Scopus, PubMed, Cinahl, SciELO, and PEDro. The PEDro scale was used to evaluate the level of evidence of the selected studies. The RevMan 5.4 statistical software was used to obtain the meta-analysis. Eight studies were included, of which five were included in the meta-analysis, involving 195 participants. The NSAIDs used through phonophoresis were ibuprofen, piroxicam, diclofenac sodium, diclofenac diethylammonium, ketoprofen, and methyl salicylate. The overall result for pain showed not-conclusive results, but a trend toward significance was found in favor of the phonophoresis group compared to the control group (standardized mean difference (SMD) = -0.92; 95% confidence interval: -1.87-0.02). Favorable results were obtained for physical function (SMD = -1.34; 95% CI: -2.00-0.68). Based on the selected studies, the application of NSAIDs by phonophoresis is effective in relieving the symptoms of knee OA. Future long-term studies are recommended.

Osteoblastic differentiation and bactericidal activity are enhanced by erythromycin released from PCL/PLGA-PVA coaxial nanofibers

Prosthesis with antibiotic-eluting nanofibrous (NF) coating represents coating alternative to prevent periprosthetic joint infection (PJI). In this study, four formulas of erythromycin (EM)-embedded both in core and sheath components of coaxial PCL/PLGA-PVA NF coatings were developed: EM 0 (no EM), EM 100 (100 μg/mL), EM500 (500 μg/mL) and EM1000 (1000 μg/mL). EM doping altered the physicochemical and structural properties of NFs to some extent, including the increase of NF porosity and surface wettability. A sustained EM release from EM-NFs for >4 weeks was observed. Eluents collected from EM-NFs showed strong zone of inhibition (ZOI) to Staphylococcus aureus growth and the sizes of ZOI positively related to the amount of EM released. EM-NFs were nontoxic to rat bone marrow stem cells (rBMSCs). Cell growth was significantly enhanced when comparing rBMSCs cultured on EM-NFs (EM0 and EM 100) to those cultured on NF-free control. Cell differentiation (ALP activity) was notably enhanced by EM100, compared to control and EM0. Eluents from EM-NFs on rBMSCs were also investigated. The presence of 10% EM-NF eluents inhibited the growth of rBMSCs, which was proportional to the amount of EM doped. The ALP activity was notably enhanced by eluents from EM-NFs with the highest activity in EM100 compared to control and EM0. Our data indicate that EM-doped PCL/PLGA-PVA coaxial NF coatings have a great potential to be applied as a new implant coating matrices. Further in vivo testing in animal models is currently planned that should represent the first step in predicting the clinical outcomes of EM-eluting NF coating approach.

Delivering macrolide antibiotics to heal a broken heart - And other inflammatory conditions

Drug carriers to deliver macrolide antibiotics, such as azithromycin, show promise as antibacterial agents. Macrolide drug carriers have largely focused on improving the drug stability and pharmacokinetics, while reducing adverse reactions and improving antibacterial activity. Recently, macrolides have shown promise in treating inflammatory conditions by promoting a reparative effect and limiting detrimental pro-inflammatory responses, which shifts the immunologic setpoint from suppression to balance. While macrolide drug carriers have only recently been investigated for their ability to modulate immune responses, the previous strategies that deliver macrolides for antibacterial therapy provide a roadmap for repurposing the macrolide drug carriers for therapeutic interventions targeting inflammatory conditions. This review describes the antibacterial and immunomodulatory activity of macrolides, while assessing the past in vivo evaluation of drug carriers used to deliver macrolides with the intention of presenting a case for increased effort to translate macrolide drug carriers into the clinic.

Overcoming Multidrug Resistance of Antibiotics via Nanodelivery Systems

Antibiotic resistance has become a threat to microbial therapies nowadays. The conventional approaches possess several limitations to combat microbial infections. Therefore, to overcome such complications, novel drug delivery systems have gained pharmaceutical scientists’ interest. Significant findings have validated the effectiveness of novel drug delivery systems such as polymeric nanoparticles, liposomes, metallic nanoparticles, dendrimers, and lipid-based nanoparticles against severe microbial infections and combating antimicrobial resistance. This review article comprises the specific mechanism of antibiotic resistance development in bacteria. In addition, the manuscript incorporated the advanced nanotechnological approaches with their mechanisms, including interaction with the bacterial cell wall, inhibition of biofilm formations, activation of innate and adaptive host immune response, generation of reactive oxygen species, and induction of intracellular effect to fight against antibiotic resistance. A section of this article demonstrated the findings related to the development of delivery systems. Lastly, the role of microfluidics in fighting antimicrobial resistance has been discussed. Overall, this review article is an amalgamation of various strategies to study the role of novel approaches and their mechanism to fight against the resistance developed to the antimicrobial therapies.

Stimuli-Responsive Delivery Strategies for Controllable Gene Editing in Tumor Therapeutics

CRISPR system has attracted significant interest due to its great potential in tumour therapy. Developing effective, precise and safe delivery vectors is a prerequisite for CRISPR applications. Some disease-related biological...

Amine-terminated dendritic polymers as promising nanoplatform for diagnostic and therapeutic agents' modification: A review

It is often challenging to design diagnostic and therapeutic agents that fulfill all functional requirements. So, bulk and surface modifications as a common approach for biomedical applications have been suggested. There have been considerable research interests in using nanomaterials to the prementioned methods. Among all nanomaterials, dendritic materials with three-dimensional structures, host-guest properties, and nano-polymeric dimensions have received considerable attention. Amine-terminated dendritic structures including, polyamidoamine (PAMAM), polypropyleneimine (PPI), and polyethyleneimine (PEI), have been enormously utilized in bio-modification. This review briefly described the structure of these three common dendritic polymers and their use to modify diagnostic and therapeutic agents in six major applications, including drug delivery, gene delivery, biosensor, bioimaging, tissue engineering, and antimicrobial activity. The current review covers amine-terminated dendritic polymers toxicity challenging and improvement strategies as well.

Local drug delivery systems for inflammatory diseases: Status quo, challenges, and opportunities

Inflammation that is not resolved in due course becomes a chronic disease. The treatment of chronic inflammatory diseases involves a long-term use of anti-inflammatory drugs such as corticosteroids and nonsteroidal anti-inflammatory drugs, often accompanied by dose-dependent side effects. Local drug delivery systems have been widely explored to reduce their off-target side effects and the medication frequency, with several products making to the market or in development over the years. However, numerous challenges remain, and drug delivery technology is underutilized in some applications. This review showcases local drug delivery systems in different inflammatory diseases, including the targets well-known to drug delivery scientists (e.g., joints, eyes, and teeth) and other applications with untapped opportunities (e.g., sinus, bladder, and colon). In each section, we start with a brief description of the disease and commonly used therapy, introduce local drug delivery systems currently on the market or in the development stage, focusing on polymeric systems, and discuss the remaining challenges and opportunities in future product development.

Stimulus-cleavable chemistry in the field of controlled drug delivery

This review comprehensively summarises stimulus-cleavable linkers from various research areas and their cleavage mechanisms, thus provides an insightful guideline to extend their potential applications to controlled drug release from nanomaterials.

Cyanuric chloride-imidazole dendrimer functionalized nanoparticles as an adsorbent for magnetic solid phase extraction of quaternary ammonium compounds from fruit and vegetable puree based infant foods

A novel magnetic solid-phase extraction (MSPE) material (Fe₃O₄@SiO₂-NH₂-G2) had been prepared and employed for adsorption and analysis of seven quaternary ammonium compounds (QACs) in infant fruit and vegetable products coupled with high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). In this paper, Fe₃O₄@SiO₂-NH₂-G2 was synthesized based on Fe₃O₄@SiO₂-NH₂ and dendrimer (G2) consisting of cyanuric chloride and imidazole. The morphology, configuration and magnetic behavior of the magnetic material were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). Critical parameters affecting extraction efficiency, such as the adsorbent amount, sample pH, extraction time, the type of eluent, and desorption time, were optimized. The proposed method provided good linearity with the correlation coefficients (R²) of 0.9992-0.9999, low limits of detection (LODs) (0.05-0.50 μg kg^-1) and limits of quantitation (LOQs) (0.20-2.00 μg kg^-1). The satisfactory method recoveries in three spiked infant fruit and vegetable products samples were between 80.12% and 101.35% with the relative standard deviations (RSDs) less than 12.04%. In summary, the established method was an effective sample preparation method and showed good prospect for the analysis of QACs in complex matrices.

Dendrimer-Mediated Targeted Delivery of Rapamycin to Tumor-Associated Macrophages Improves Systemic Treatment of Glioblastoma

Glioblastoma exhibits high mortality rates due to challenges with drug delivery to the brain and into solid tumors. This two-pronged barrier necessitates high doses of systemic therapies, resulting in significant off-target toxicities. Recently, dendrimer-nanomedicines (without ligands) have shown promise for targeting specific cells in brain tumors from systemic circulation, for improved efficacy and amelioration of systemic toxicities. A dendrimer-rapamycin conjugate (D-Rapa) is presented here that specifically targets tumor-associated macrophages (TAMs) in glioblastoma from systemic administration. D-Rapa improves suppression of pro-tumor expression in activated TAMs and antiproliferative properties of rapamycin in glioma cells in vitro. In vivo, D-Rapa localizes specifically within TAMs, acting as depots to release rapamycin into the tumor microenvironment. This targeted delivery strategy yields improved reduction in tumor burden and systemic toxicities in a challenging, clinically relevant orthotopic syngeneic model of glioblastoma, demonstrating the significant potential of dendrimers as targeted immunotherapies for improving glioblastoma treatment, still an unmet need.

Mannose receptor 1 expression does not determine the uptake of high-density mannose dendrimers by activated macrophages populations

The presence of a high number of macrophages within solid tumors is often significantly associated with poor prognosis and predict treatment failure for chemotherapy and radiotherapy. Macrophages are innate immune cells capable of performing diverse functions depending on the different signals from the microenvironment. The classically activated macrophage is commonly present during the early stages of tumor development while alternatively activated macrophages are associated with more advanced tumors. The distinction of the antitumoral macrophages from the pro-tumoral macrophages is not absolute. However, they have different cell surface markers such as mannose receptor (MRC1 or CD206) abundantly expressed by macrophages treated with interleukin-4 (IL-4). The important roles of macrophages in cancers suggest that it is important to develop novel therapies that target these cells. In the present study, we designed a probe using Polyamidoamine (PAMAM) fifth-generation (G5) dendrimers conjugated with mannose, Cyanine 7 (Cy7), and hydrazinonicotinamide (HYNIC) for target macrophages with high expression of MRC1 in the tumor. The intracellular uptake of 99mTc-HYNIC-dendrimer-mannose-Cy7 through the interaction with MRC1 in bone marrow-derived macrophages (BMDMs) untreated or treated with lipopolysaccharides (LPS) + interferon (IFN)γ or IL-4 was analyzed. Our results show that high-density mannose dendrimers are preferentially bound by macrophages treated by IFNγ and LPS that express lower levels of MRC1 than for macrophages treated by IL-4 that express high levels of MRC1. Furthermore, the intracellular 99mTc-HYNIC-dendrimer-mannose-Cy7 uptake in BMDMs was not inhibited in the presence of free mannose or glucose. This result suggests that 99mTc-HYNIC-dendrimer-mannose-Cy7 is not internalized via macrophage MRC1. Based on these findings, we concluded that MRC1 expression does not determine the uptake of high-density mannose dendrimers.

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.

A multifunctional lipid that forms contrast-agent liposomes with dual-control release capabilities for precise MRI-guided drug delivery

Monitoring of nanoparticle-based therapy in vivo and controlled drug release are urgently needed for the precise treatment of disease. We have synthesized a multifunctional Gd-DTPA-ONB (GDO) lipid by introducing the Gd-DTPA contrast agent moiety into an o-nitro-benzyl ester lipid. By design, liposomes formed from the GDO lipid combine MRI tracking ability and dual-trigger release capabilities with maximum sensitivity (because all lipids bear the cleavable moiety) without reducing the drug encapsulation rate. We first confirmed that both photo-treatment and pH-triggered hydrolysis are able to cleave the GDO lipid and lyse GDO liposomes. We then investigated the efficiency of drug release via the combined release processes for GDO liposomes loaded with doxorubicin (DOX). Relative to neutral pH, the release efficiency in acidic environment increased by 10.4% (at pH = 6.5) and 13.3% (at pH = 4.2). This pH-dependent release response is conducive to distinguishing pathological tissue such as tumors and endolysosomal compartments. The photo-induced release efficiency increases with illumination time as well as with distance of the pH from neutral. Photolysis increased the release efficiency by 13.8% at pH = 4.2, which is remarkable considering the already increased amount of drug release in the acidic environment. In addition, the relaxation time of GDO liposomes was 4.1 times that of clinical Gd-DTPA, with brighter T₁-weighted imaging in vitro and in vivo. Real-time MRI imaging and in vivo fluorescence experiments demonstrated tumor targeting and MRI guided release. Furthermore, significant tumor growth inhibition in a treatment experiment using DOX-loaded GDO liposomes clearly demonstrated the benefit of photo-treatment for efficacy: the tumor size in the photo-treatment group was 3.7 times smaller than in the control group. The present study thus highlights the benefit of the design idea of combining efficient imaging/guiding, targeting, and triggerable release functions in one lipid molecule for drug delivery applications.

Antimicrobial Polymers: The Potential Replacement of Existing Antibiotics?

Antimicrobial resistance is now considered a major global challenge; compromising medical advancements and our ability to treat infectious disease. Increased antimicrobial resistance has resulted in increased morbidity and mortality due to infectious diseases worldwide. The lack of discovery of novel compounds from natural products or new classes of antimicrobials, encouraged us to recycle discontinued antimicrobials that were previously removed from routine use due to their toxicity, e.g., colistin. Since the discovery of new classes of compounds is extremely expensive and has very little success, one strategy to overcome this issue could be the application of synthetic compounds that possess antimicrobial activities. Polymers with innate antimicrobial properties or that have the ability to be conjugated with other antimicrobial compounds create the possibility for replacement of antimicrobials either for the direct application as medicine or implanted on medical devices to control infection. Here, we provide the latest update on research related to antimicrobial polymers in the context of ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) pathogens. We summarise polymer subgroups: compounds containing natural peptides, halogens, phosphor and sulfo derivatives and phenol and benzoic derivatives, organometalic polymers, metal nanoparticles incorporated into polymeric carriers, dendrimers and polymer-based guanidine. We intend to enhance understanding in the field and promote further work on the development of polymer based antimicrobial compounds.

Anti-inflammatory drug-eluting implant model system to prevent wear particle-induced periprosthetic osteolysis

BACKGROUND

Aseptic loosening, as a consequence of an extended inflammatory reaction induced by wear particles, has been classified as one of the most common complications of total joint replacement (TJR). Despite its high incidence, no therapeutical approach has yet been found to prevent aseptic loosening, leaving revision as only effective treatment. The local delivery of anti-inflammatory drugs to modulate wear-induced inflammation has been regarded as a potential therapeutical approach to prevent aseptic-loosening.

METHODS

In this context, we developed and characterized anti-inflammatory drug-eluting TiO2 surfaces, using nanoparticles as a model for larger surfaces. The eluting surfaces were obtained by conjugating dexamethasone to carboxyl-functionalized TiO2 particles, obtained by using either silane agents with amino or mercapto moieties.

RESULTS

Zeta potential measurements, thermogravimetric analysis (TGA) and drug release results suggest that dexamethasone was successfully loaded onto the TiO2 particles. Release was pH dependent and greater amounts of drug were observed from amino route functionalized surfaces. The model-system was then tested for its cytotoxic and anti-inflammatory properties in LPS-stimulated macrophages. Dexamethasone released from amino route functionalized surfaces TiO2 particles was able to decrease LPS-induced nitric oxide (NO) and TNF-a production similarly to pure DEX at the same concentration; DEX released from mercapto route functionalized surfaces was at a too low concentration to be effective.

CONCLUSION

Dexamethasone released from amino functionalized titanium can offer the possibility of preventing asepting loosening of joint replacement devices.

Dendrimeric Poly(Epsilon-Lysine) Delivery Systems for the Enhanced Permeability of Flurbiprofen across the Blood-Brain Barrier in Alzheimer's Disease

Alzheimer's disease (AD) is a progressive brain disorder and age-related disease characterised by abnormal accumulation of β-amyloid (Aβ). The development of drugs to combat AD is hampered by the lack of therapeutically-active molecules able to cross the blood-brain barrier (BBB). It is agreed that specifically-designed carriers, such as dendrimers, could support the drug penetration across the BBB. The aim of this study was to design biocompatible and biodegradable dendrimeric delivery systems able to carry Flurbiprofen (FP), as drug for AD treatment, across the BBB and liberate it at the target tissue. These dendrons were synthesised using solid-phase peptide synthesis method and characterised by mass spectrometry and fourier-transform infrared spectroscopy (FTIR). The results revealed successful synthesis of dendrons having FP been integrated during the synthesis at their branching ends. Cytotoxicity assays demonstrated the biocompatibility of the delivery systems, whereas HPLC analysis showed high percentages of permeability across an in vitro BBB model for FP-integrated dendrons. Results also revealed the efficiency of drug conjugates on the γ-secretase enzyme in target cells with evidence of eventual drug release by hydrolysis of the carrier. This study demonstrates that the coupling of FP to dendrimeric delivery systems can successfully be achieved during the synthesis of the poly(epsilon-lysine) macromolecules to improve the transport of the active drug across the BBB.

Synthesis of the erythromycin-conjugated nanodendrimer and its antibacterial activity

The development and spread of bacterial resistance to antimicrobial drugs necessitates the need to search for novel and effective antimicrobial agents. In the last few decades, innovative nanomaterials are attracting increasing attention and, among them, dendrimers have shown wide application in the various fields. In the current study, the two generations of an anionic linear- spherical nanodendrimer G1 and G2 were synthetized and compound G2 of nanodendrimer conjugated with erythromycin. The structures of the nanodendrimers were characterized by FTIR spectroscopy, zetasizer, and scanning electron microscopy (SEM). The antibacterial activity of the erythromycin-conjugated nanodendrimer and erythromycin alone were evaluated by the microdilution method against Staphylococcus aureus, S. epidermidis, S. saprophyticus, and Pseudomonas aeruginosa. The size of first and second generation of nanodendrimer, and the erythromycin-conjugated nanodendrimer was 75, 95, and 65.6 nm, respectively. The drug loading percentage of the nanodendrimer conjugates was obtained to be in 35.2%. In our study, the erythromycin-conjugated nanodendrimer showed significantly more bacteriostatic and bactericidal activities against all four studied bacteria than erythromycin alone. Our study's results highlight that the erythromycin-conjugated nanodendrimer is a highly effective agent against Gram positive and negative bacteria. The antibacterial properties of erythromycin combined with the targeting potential of the nanodendrimer can lead to sustained intracellular delivery of therapeutic agent.

Overcoming antibiotic resistance: Is siderophore Trojan horse conjugation an answer to evolving resistance in microbial pathogens?

Comparative study of siderophore biosynthesis pathway in pathogens provides potential targets for antibiotics and host drug delivery as a part of computationally feasible microbial therapy. Iron acquisition using siderophore models is an essential and well established model in all microorganisms and microbial infections a known to cause great havoc to both plant and animal. Rapid development of antibiotic resistance in bacterial as well as fungal pathogens has drawn us at a verge where one has to get rid of the traditional way of obstructing pathogen using single or multiple antibiotic/chemical inhibitors or drugs. 'Trojan horse' strategy is an answer to this imperative call where antibiotic are by far sneaked into the pathogenic cell via the siderophore receptors at cell and outer membrane. This antibiotic once gets inside, generates a 'black hole' scenario within the opportunistic pathogens via iron scarcity. For pathogens whose siderophore are not compatible to smuggle drug due to their complex conformation and stiff valence bonds, there is another approach. By means of the siderophore biosynthesis pathways, potential targets for inhibition of these siderophores in pathogenic bacteria could be achieved and thus control pathogenic virulence. Method to design artificial exogenous siderophores for pathogens that would compete and succeed the battle of intake is also covered with this review. These manipulated siderophore would enter pathogenic cell like any other siderophore but will not disperse iron due to which iron inadequacy and hence pathogens control be accomplished. The aim of this review is to offer strategies to overcome the microbial infections/pathogens using siderophore.

Synthesis of G0 aminopolyol and aminosugar dendrimers, controlled by NMR and MALDI TOF mass spectrometry

Organic compounds designed to serve as stable dendrimer cores were developed. A series of aminosugar and amino polyol containing G0 dendrimers were synthesized. The reaction mixture composition was checked by MALDI TOF mass spectrometry, while that of purified products – by ¹H and ¹³C NMR combined with 2D NMR spectroscopy as well as MALDI TOF MSMS mass spectra. Mass spectrometric fragmentation experiments were performed in positive ion mode in order to determine common fragmentation patterns of [M+H]⁺ ions.

Dendrimer Prodrugs

The main objective of this review is to describe the importance of dendrimer prodrugs in the design of new drugs, presenting numerous applications of these nanocomposites in the pharmaceutical field. Therefore, the use of dendrimer prodrugs as carrier for drug delivery, to improve pharmacokinetic properties of prototype, to promote drug sustained-release, to increase selectivity and, consequently, to decrease toxicity, are just some examples of topics that have been extensively reported in the literature, especially in the last decade. The examples discussed here give a panel of the growing interest dendrimer prodrugs have been evoking in the scientific community.

Anti-inflammatory Nanoparticle for Prevention of Atherosclerotic Vascular Diseases

Recent technical innovation has enabled chemical modifications of small materials and various kinds of nanoparticles have been created. In clinical settings, nanoparticle-mediated drug delivery systems have been used in the field of cancer care to deliver therapeutic agents specifically to cancer tissues and to enhance the efficacy of drugs by gradually releasing their contents. In addition, nanotechnology has enabled the visualization of various molecular processes by targeting proteinases or inflammation. Nanoparticles that consist of poly (lactic-co-glycolic) acid (PLGA) deliver therapeutic agents to monocytes/macrophages and function as anti-inflammatory nanoparticles in combination with statins, angiotensin receptor antagonists, or agonists of peroxisome proliferator-activated receptor-γ (PPARγ). PLGA nanoparticle-mediated delivery of pitavastatin has been shown to prevent inflammation and ameliorated features associated with plaque ruptures in hyperlipidemic mice. PLGA nanoparticles were also delivered to tissues with increased vascular permeability and nanoparticles incorporating pitavastatin, injected intramuscularly, were retained in ischemic tissues and induced therapeutic arteriogenesis. This resulted in attenuation of hind limb ischemia. Ex vivo treatment of vein grafts with imatinib nanoparticles before graft implantation has been demonstrated to inhibit lesion development. These results suggest that nanoparticle-mediated drug delivery system can be a promising strategy as a next generation therapy for atherosclerotic vascular diseases.

Drug delivery to macrophages: Challenges and opportunities

Macrophages are prevalent in the body and have roles in almost every aspect of human biology. They have often been considered a subject to avoid during drug delivery. However, with recent understanding of their diverse functions in diseases, macrophages have gained increasing interest as important therapeutic targets. To develop drug carriers to macrophages, it is important to understand their biological roles and requirements for efficient targeting. This review provides an overview of representative carriers and various approaches to address challenges in drug delivery to macrophages such as biodistribution, cellular uptake, intracellular trafficking, and drug release.

Poly(Propylene Imine) Dendrimers and Amoxicillin as Dual-Action Antibacterial Agents

Besides acting as antimicrobial compounds, dendrimers can be considered as agents that improve the therapeutic effectiveness of existing antibiotics. In this work we present a new approach to using amoxicillin (AMX) against reference strains of common Gram-negative pathogens, alone and in combination with poly(propylene imine) (PPI) dendrimers, or derivatives thereof, in which 100% of the available hydrogen atoms are substituted with maltose (PPI 100%malG3). The concentrations of dendrimers used remained in the range non-toxic to eukaryotic cells. The results indicate that PPI dendrimers significantly enhance the antibacterial effect of amoxicillin alone, allowing antibiotic doses to be reduced. It is important to reduce doses of amoxicillin because its widespread use in medicine could lead to the development of bacterial resistance and environmental pollution. This is the first report on the combined antibacterial activity of PPI surface-modified maltose dendrimers and amoxicillin.

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.

Dendrimer-coupled sonophoresis-mediated transdermal drug-delivery system for diclofenac

The purpose of the present study was to develop a novel transdermal drug-delivery system comprising a polyamidoamine dendrimer coupled with sonophoresis to enhance the permeation of diclofenac (DF) through the skin. The novel transdermal drug-delivery system was developed by using a statistical Plackett–Burman design. Hairless male Wistar rat skin was used for the DF-permeation study. Coupling media concentration, ultrasound-application time, duty cycle, distance from probe to skin, and a third-generation polyamidoamine-dendrimer concentration were selected as independent variables, while in vitro drug release was selected as a dependent variable. Independent variables were found to be statistically significant (P<0.05). DF gel without dendrimer and ultrasound treatment to skin (passive delivery, run 13) showed 56.69 µg/cm² cumulative drug permeated through the skin, while the DF-dendrimer gel without sonophoresis treatment (run 14) showed 257.3 µg/cm² cumulative drug permeated through the skin after 24 hours. However, when the same gel was applied to sonophoresis-treated skin, drastic permeation enhancement was observed. In the case of run 3, the cumulative drug that permeated through the skin was 935.21 µg/cm². It was concluded that dendrimer-coupled sonophoresis-mediated transdermal drug delivery system has the potential to enhance the permeation of DF through the skin.

Intracellular delivery of dendrimer triamcinolone acetonide conjugates into microglial and human retinal pigment epithelial cells

Triamcinolone acetonide (TA) is a potent, intermediate-acting, steroid that has anti-inflammatory and anti-angiogenic activity. Intravitreal administration of TA has been used for diabetic macular edema, proliferative diabetic retinopathy and exudative age-related macular degeneration (AMD). However, the hydrophobicity, lack of solubility, and the side effects limit its effectiveness in the treatment of retinal diseases. In this study, we explore a PAMAM dendrimer-TA conjugate (D-TA) as a potential strategy to improve intracellular delivery and efficacy of TA to target cells. The conjugates were prepared with a high drug payload (∼ 21%) and were readily soluble in saline. Compared to free TA, D-TA demonstrated a significantly improved toxicity profile in two important target [microglial and human retinal pigment epithelium (RPE)] cells. The D-TA was ∼ 100-fold more effective than free TA in its anti-inflammatory activity (measured in microglia), and in suppressing VEGF production (in hypoxic RPE cells). Dendrimer-based delivery may improve the efficacy of TA towards both its key targets of inflammation and VEGF production, with significant clinical implications.

Nanoengineered drug delivery systems for enhancing antibiotic therapy

Formulation scientists are recognizing nanoengineered drug delivery systems as an effective strategy to overcome limitations associated with antibiotic drug therapy. Antibiotics encapsulated into nanodelivery systems will contribute to improved management of patients with various infectious diseases and to overcoming the serious global burden of antibiotic resistance. An extensive review of several antibiotic-loaded nanocarriers that have been formulated to target drugs to infectious sites, achieve controlled drug release profiles, and address formulation challenges, such as low-drug entrapment efficiencies, poor solubility and stability is presented in this paper. The physicochemical properties and the in vitro/in vivo performances of various antibiotic-loaded delivery systems, such as polymeric nanoparticles, micelles, dendrimers, liposomes, solid lipid nanoparticles, lipid-polymer hybrid nanoparticles, nanohybirds, nanofibers/scaffolds, nanosheets, nanoplexes, and nanotubes/horn/rods and nanoemulsions, are highlighted and evaluated. Future studies that will be essential to optimize formulation and commercialization of these antibiotic-loaded nanosystems are also identified. The review presented emphasizes the significant formulation progress achieved and potential that novel nanoengineered antibiotic drug delivery systems have for enhancing the treatment of patients with a range of infections.

Dendrimer encapsulation enhances anti-inflammatory efficacy of silver nanoparticles

BACKGROUND

Our previous studies revealed that silver nanoparticles (AgNPs) promoted wound healing in part through their anti-inflammatory actions. As recent reports also suggested anti-inflammatory effects of dendrimers, we therefore undertook this study using dendrimer as the delivery system for AgNP to explore any potential synergistic anti-inflammatory efficacy.

METHODS

Lipopolysaccharide (LPS) was added to cultured RAW264.7 and J774.1 cells to mimic in vitro inflammation condition, followed by the addition of either silver dendrimer nanocomposite (Ag-DNC), AgNPs, or dendrimer. The levels of inflammatory markers TNF-alpha and interleukin-6 were assessed using ELISA assay. Furthermore, in vivo effects such of Ag-DNC, AgNPs, or dendrimer were studied in a burn wound model in mice.

RESULTS

Our results confirmed that both naked dendrimer and AgNPs had anti-inflammatory properties. In in vitro study, Ag-DNC was shown to have the best anti-inflammatory efficacy than AgNPs or dendrimer alone. In-vivo experiments also indicated that animals in the Ag-DNC group had the fastest healing time with the least inflammation.

CONCLUSION

Our study would suggest that dendrimer could provide additional anti-inflammatory benefits and might be an excellent delivery system for silver nanoparticles for future clinical application.

Dendrimers in drug delivery and targeting: Drug-dendrimer interactions and toxicity issues

Dendrimers are the emerging polymeric architectures that are known for their defined structures, versatility in drug delivery and high functionality whose properties resemble with biomolecules. These nanostructured macromolecules have shown their potential abilities in entrapping and/or conjugating the high molecular weight hydrophilic/hydrophobic entities by host-guest interactions and covalent bonding (prodrug approach) respectively. Moreover, high ratio of surface groups to molecular volume has made them a promising synthetic vector for gene delivery. Owing to these properties dendrimers have fascinated the researchers in the development of new drug carriers and they have been implicated in many therapeutic and biomedical applications. Despite of their extensive applications, their use in biological systems is limited due to toxicity issues associated with them. Considering this, the present review has focused on the different strategies of their synthesis, drug delivery and targeting, gene delivery and other biomedical applications, interactions involved in formation of drug-dendrimer complex along with characterization techniques employed for their evaluation, toxicity problems and associated approaches to alleviate their inherent toxicity.

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.

Folate-functionalized dendrimers for targeting Chlamydia-infected tissues in a mouse model of reactive arthritis

Chlamydia trachomatis is an intracellular human pathogen that causes a sexually transmitted disease which may result in an inflammatory arthritis designated Chlamydia-induced reactive arthritis (ReA). The arthritis develops after dissemination of infected cells from the initial site of chlamydial infection. During Chlamydia-associated ReA, the organism may enter into a persistent infection state making treatment with antibiotics a challenge. We hypothesize that folate receptors (FR), which are overexpressed in Chlamydia-infected cells, and the associated inflammation would allow folate-targeted nanodevices to better treat infections. To investigate this, we developed a folate-PAMAM dendrimer-Cy5.5 conjugate (D-FA-Cy5.5), where Cy5.5 is used as the near-IR imaging agent. Uptake of D-FA-Cy5.5 upon systemic administration was assessed and compared to non-folate conjugated controls (D-Cy5.5), using a mouse model of Chlamydia-induced ReA, and near-IR imaging. Our results suggested that there was a higher concentration of folate-based nanodevice in sites of infection and inflammation compared to that of the control nanodevice. The folate-conjugated nanodevices localized to infected paws and genital tracts (major sites of inflammation and infection) at 3-4 fold higher concentrations than were dendrimer alone, suggesting that the overexpression of folate receptors in infected and inflamed tissues enables higher dendrimer uptake. There was an increase in uptake into thymus, spleen, and lung, but no significant differences in the uptake of the folate nanodevices in other organs including kidney and heart, indicating the 'relative specificity' of the D-FA-Cy5.5 conjugate nanodevices. These results suggest that folate targeting dendrimers are able to deliver drugs to attenuate infection and associated inflammation in Chlamydia-induced ReA.

Biodistribution of fluorescently labeled PAMAM dendrimers in neonatal rabbits: effect of neuroinflammation

Dendrimers are being explored in many preclinical studies as drug, gene, and imaging agent delivery systems. Understanding their detailed organ, tissue, cellular uptake, and retention can provide valuable insights into their effectiveness as delivery vehicles and the associated toxicity. This work explores a fluorescence-quantification based assay that enables simultaneous quantitative biodistribution and imaging of dendrimers with a single agent. We have labeled an ethylenediamine-core generation-4 hydroxyl-terminated poly(amidoamine) (PAMAM) dendrimer using the fluorescent photostable, near-IR cyanine dye (Cy5) and performed quantitative and qualitative biodistribution of the dendrimer-Cy5 conjugates (D-Cy5) in healthy neonatal rabbits and neonatal rabbits with cerebral palsy (CP). The biodistribution of D-Cy5 and free Cy5 dye was evaluated in newborn rabbits, based on the developed quantification methods using fluorescence spectroscopy, high-performance liquid chromatography (HPLC), and size exclusion chromatography (SEC) and supported by microscopic imaging. The uptake was assessed in the brain, heart, liver, lungs, kidneys, blood serum, and urine. Results obtained based on these three independent methods are in good agreement and indicate the fast renal clearance of D-Cy5 and free Cy5 with relatively higher organs accumulation of the D-Cy5 conjugate. Following systemic administration, the D-Cy5 mainly accumulated in kidneys and bladder at 24 h. The quantitative biodistribution is in good agreement with previous studies based on radiolabeling. These methods for dendrimers quantification are easier and more practical, provide excellent sensitivity (reaching 0.1 ng per gram of tissue), and allow for quantification of dendrimers in different organs over longer time periods without concerns for radioactive decay, while also enabling tissue and cellular imaging in the same animal. In kits with fetal-neuroinflammation induced CP, there was a significantly higher uptake of D-Cy5 in the brain, while biodistribution in other organs was similar to that of healthy kits.