PAMAM Dendrimers: Destined for Success or Doomed to Fail? Plain and Modified PAMAM Dendrimers in the Context of Biomedical Applications

The menace of severe adverse events and deaths associated with viral gene therapy and its potential solution

Over the past decade, in vivo gene replacement therapy has significantly advanced, resulting in market approval of numerous therapeutics predominantly relying on adeno-associated viral vectors (AAV). While viral vectors have undeniably addressed several critical healthcare challenges, their clinical application has unveiled a range of limitations and safety concerns. This review highlights the emerging challenges in the field of gene therapy. At first, we discuss both the role of biological barriers in viral gene therapy with a focus on AAVs, and review current landscape of in vivo human gene therapy. We delineate advantages and disadvantages of AAVs as gene delivery vehicles, mostly from the safety perspective (hepatotoxicity, cardiotoxicity, neurotoxicity, inflammatory responses etc.), and outline the mechanisms of adverse events in response to AAV. Contribution of every aspect of AAV vectors (genomic structure, capsid proteins) and host responses to injected AAV is considered and substantiated by basic, translational and clinical studies. The updated evaluation of recent AAV clinical trials and current medical experience clearly shows the risks of AAVs that sometimes overshadow the hopes for curing a hereditary disease. At last, a set of established and new molecular and nanotechnology tools and approaches are provided as potential solutions for mitigating or eliminating side effects. The increasing number of severe adverse reactions and, sadly deaths, demands decisive actions to resolve the issue of immune responses and extremely high doses of viral vectors used for gene therapy. In response to these challenges, various strategies are under development, including approaches aimed at augmenting characteristics of viral vectors and others focused on creating secure and efficacious non-viral vectors. This comprehensive review offers an overarching perspective on the present state of gene therapy utilizing both viral and non-viral vectors.

External Trigger Free Charge Switchable Cationic Ligands in the Design of Safe and Effective Universal Heparin Antidote

Thrombosis, the formation of blood clots within a blood vessel, can lead to severe complications including pulmonary embolism, cardiac arrest, and stroke. The most widely administered class of anticoagulants is heparin-based anticoagulants such as unfractionated heparin, low-molecular weight heparins (LMWHs), and fondaparinux. Protamine is the only FDA-approved heparin antidote. Protamine has limited efficacy neutralizing LMWHs and no reversal activity against fondaparinux. The use of protamine can lead to complications, including excessive bleeding, hypotension, and hypersensitivity, and has narrow therapeutic window. In this work, a new concept in the design of a universal heparin antidote: switchable protonation of cationic ligands, is presented. A library of macromolecular polyanion inhibitors (MPIs) is synthesized and screened to identify molecules that can neutralize all heparins with high selectivity and reduced toxicity. MPIs are developed by assembling cationic binding groups possessing switchable protonation states onto a polymer scaffold. By strategically selecting the identity and modulating the density of cationic binding groups on the polymer scaffold, a superior universal heparin reversal agent is developed with improved heparin-binding activity and increased hemocompatibility profiles leading to minimal effect on hemostasis. The activity of this heparin antidote is demonstrated using in vitro and in vivo studies.

Nanomaterials as Microglia Modulators in the Treatment of Central Nervous System Disorders

Microglia play a pivotal role in the central nervous system (CNS) homeostasis, acting as housekeepers and defenders of the surrounding environment. These cells can elicit their functions by shifting into two main phenotypes: pro-inflammatory classical phenotype, M1, and anti-inflammatory alternative phenotype, M2. Despite their pivotal role in CNS homeostasis, microglia phenotypes can influence the development and progression of several CNS disorders such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, multiple sclerosis, ischemic stroke, traumatic brain injuries, and even brain cancer. It is thus clear that the possibility of modulating microglia activation has gained attention as a therapeutic tool against many CNS pathologies. Nanomaterials are an unprecedented tool for manipulating microglia responses, in particular, to specifically target microglia and elicit an in situ immunomodulation activity. This review focuses the discussion on two main aspects: analyzing the possibility of using nanomaterials to stimulate a pro-inflammatory response of microglia against brain cancer and introducing nanostructures able to foster an anti-inflammatory response for treating neurodegenerative disorders. The final aim is to stimulate the analysis of the development of new microglia nano-immunomodulators, paving the way for innovative and effective therapeutic approaches for the treatment of CNS disorders.

Receptor for advanced glycation end-products: Biological significance and imaging applications

The receptor for advanced glycation end-products (RAGE or AGER) is a transmembrane, immunoglobulin-like receptor that, due to its multiple isoform structures, binds to a diverse range of endo- and exogenous ligands. RAGE activation caused by the ligand binding initiates a cascade of complex pathways associated with producing free radicals, such as reactive nitric oxide and oxygen species, cell proliferation, and immunoinflammatory processes. The involvement of RAGE in the pathogenesis of disorders such as diabetes, inflammation, tumor progression, and endothelial dysfunction is dictated by the accumulation of advanced glycation end-products (AGEs) at pathologic states leading to sustained RAGE upregulation. The involvement of RAGE and its ligands in numerous pathologies and diseases makes RAGE an interesting target for therapy focused on the modulation of both RAGE expression or activation and the production or exogenous administration of AGEs. Despite the known role that the RAGE/AGE axis plays in multiple disease states, there remains an urgent need to develop noninvasive, molecular imaging approaches that can accurately quantify RAGE levels in vivo that will aid in the validation of RAGE and its ligands as biomarkers and therapeutic targets. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Diagnostic Tools > Biosensing.

Anticancer Potential of Dendritic Poly(aryl ether)-Substituted Polypyridyl Ligand-Based Ruthenium(II) Coordination Entities

This paper studies the anticancer potency of dendritic poly(aryl ether)-substituted polypyridyl ligand-based ruthenium(II) coordination entities. The dendritic coordination entities were successfully designed, synthesized, and characterized by different spectral methods such as Fourier transform infrared (FTIR), 1H and 13C- NMR, and mass spectrometry. Further, to understand the structure and solvation behavior of the coordination entities, we performed all-atom molecular dynamics (MD) simulations. The behavior, configuration, and size of the coordination entities in DMSO and water were studied by calculating the radius of gyration (Rg) and solvent-accessible surface area (SASA). The MTT assay was used to assess the in vitro cytotoxicity of all of the coordination entities against cancerous A549 (lung cancer cells), MDA MB 231 (breast cancer cells), and HepG2 (liver cancer cells) and was found to be good with comparable IC50 values with respect to the standard drug cisplatin. The coordination entities exhibited dose dependence, and the highest activity was shown against HepG2 cell lines in comparison to the other cancer cell lines. In addition, fluorescence staining studies, such as AO/EB, DAPI, and cell death analysis by PI staining, were performed on the coordination entities to understand the apoptosis mechanism. Furthermore, reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) assays confirmed apoptosis in cancer cells via the mitochondrial pathway. The DNA fragmentation assay was done followed by molecular docking analysis with DNA executed to strengthen and support the experimental observations.

Conjugation of Short Oligopeptides to a Second-Generation Polyamidoamine Dendrimer Shows Antibacterial Activity

The growing evolution of bacterial resistance to antibiotics represents a global issue that not only impacts healthcare systems but also political and economic processes. This necessitates the development of novel antibacterial agents. Antimicrobial peptides have shown promise in this regard. Thus, in this study, a new functional polymer was synthesized by joining a short oligopeptide sequence (Phe-Lys-Phe-Leu, FKFL) to the surface of a second-generation polyamidoamine (G2 PAMAM) dendrimer as an antibacterial component. This method of synthesis proved simple and resulted in a high conjugation yield of the product FKFL-G2. To determine its antibacterial potential, FKFL-G2 was subsequently analyzed via mass spectrometry, a cytotoxicity assay, bacterial growth assay, colony-forming unit assay, membrane permeabilization assay, transmission electron microscopy, and biofilm formation assay. FKFL-G2 was found to exhibit low toxicity to noncancerous NIH3T3 cells. Additionally, FKFL-G2 had an antibacterial effect on Escherichia coli and Staphylococcus aureus strains by interacting with and disrupting the bacterial cell membrane. Based on these findings, FKFL-G2 shows promise as a potential antibacterial agent.

Nanoparticles: Taking a Unique Position in Medicine

The human nature of curiosity, wonder, and ingenuity date back to the age of humankind. In parallel with our history of civilization, interest in scientific approaches to unravel mechanisms underlying natural phenomena has been developing. Recent years have witnessed unprecedented growth in research in the area of pharmaceuticals and medicine. The optimism that nanotechnology (NT) applied to medicine and drugs is taking serious steps to bring about significant advances in diagnosing, treating, and preventing disease-a shift from fantasy to reality. The growing interest in the future medical applications of NT leads to the emergence of a new field for nanomaterials (NMs) and biomedicine. In recent years, NMs have emerged as essential game players in modern medicine, with clinical applications ranging from contrast agents in imaging to carriers for drug and gene delivery into tumors. Indeed, there are instances where nanoparticles (NPs) enable analyses and therapies that cannot be performed otherwise. However, NPs also bring unique environmental and societal challenges, particularly concerning toxicity. Thus, clinical applications of NPs should be revisited, and a deep understanding of the effects of NPs from the pathophysiologic basis of a disease may bring more sophisticated diagnostic opportunities and yield more effective therapies and preventive features. Correspondingly, this review highlights the significant contributions of NPs to modern medicine and drug delivery systems. This study also attempted to glimpse the future impact of NT in medicine and pharmaceuticals.

Mixed-surface polyamidoamine polymer variants retain nucleic acid-scavenger ability with reduced toxicity

Nucleic acid-binding polymers can have anti-inflammatory properties and beneficial effects in animal models of infection, trauma, cancer, and autoimmunity. PAMAM G3, a polyamidoamine dendrimer, is fully cationic bearing 32 protonable surface amines. However, while PAMAM G3 treatment leads to improved outcomes for mice infected with influenza, at risk of cancer metastasis, or genetically prone to lupus, its administration can lead to serosal inflammation and elevation of biomarkers of liver and kidney damage. Variants with reduced density of cationic charge through the interspersal of hydroxyl groups were evaluated as potentially better-tolerated alternatives. Notably, the variant PAMAM G3 50:50, similar in size as PAMAM G3 but with half the charge, was not toxic in cell culture, less associated with weight loss or serosal inflammation after parenteral administration, and remained effective in reducing glomerulonephritis in lupus-prone mice. Identification of such modified scavengers should facilitate their development as safe and effective anti-inflammatory agents.

PAMAM-Calix-Dendrimers: Second Generation Synthesis, Fluorescent Properties and Catecholamines Binding

A convenient method for the synthesis of the second generation of PAMAM dendrimers based on a p-tert-butylthiacalix[4]arene core in cone, partial cone and 1,3-alternate conformations was developed. Unusual fluorescence of the obtained PAMAM-calix-dendrimers has been found and explained. The binding ability of the synthesized dendrimers toward catecholamines (dopamine, L-adrenaline and L-noradrenaline) was shown by UV-Vis, fluorescence, 1D and 2D NMR spectroscopy and the binding constants (logK_a 3.85-4.74) calculated. As was shown, the PAMAM-calix-dendrimers bind catecholamines by the internal cavities. All the studied hormones were most efficiently bound by the dendrimers bearing a macrocyclic core in 1,3-alternate conformation. The size of the formed supramolecular systems of dendrimer/catecholamine was established by the DLS method. A decrease in hemolytic activity of the PAMAM-calix-dendrimers with an increase in the generation number of a dendrimer was shown for the dendrimers with a core in 1,3-alternate conformation. The prospects for the use of the synthesized dendrimers with the macrocyclic core as drug delivery agents were discussed.

Mitigating Cardiotoxicity of Dendrimers: Angiotensin-(1-7) via Its Mas Receptor Ameliorates PAMAM-Induced Cardiac Dysfunction in the Isolated Mammalian Heart

AIM

The influence of the physiochemical properties of dendrimer nanoparticles on cardiac contractility and hemodynamics are not known. Herein, we investigated (a) the effect of polyamidoamine (PAMAM) dendrimer generation (G7, G6, G5, G4 and G3) and surface chemistry (-NH₂, -COOH and -OH) on cardiac function in mammalian hearts following ischemia-reperfusion (I/R) injury, and (b) determined if any PAMAM-induced cardiotoxicity could be mitigated by Angiotensin-(1-7) (Ang-(1-7), a cardioprotective agent.

METHODS

Hearts isolated from male Wistar rats underwent regional I/R and/or treatment with different PAMAM dendrimers, Ang-(1-7) or its MAS receptors antagonists. Thirty minutes of regional ischemia through ligation of the left anterior descending coronary artery was followed by 30 min of reperfusion. All treatments were initiated 5 min prior to reperfusion and maintained during the first 10 min of reperfusion. Cardiac function parameters for left ventricular contractility, hemodynamics and vascular dynamics data were acquired digitally, whereas cardiac enzymes and infarct size were used as measures of cardiac injury.

RESULTS

Treatment of isolated hearts with increasing doses of G7 PAMAM dendrimer progressively exacerbated recovery of cardiac contractility and hemodynamic parameters post-I/R injury. Impairment of cardiac function was progressively less on decreasing dendrimer generation with G3 exhibiting little or no cardiotoxicity. Cationic PAMAMs (-NH₂) were more toxic than anionic (-COOH), with neutral PAMAMs (-OH) exhibiting the least cardiotoxicity. Cationic G7 PAMAM-induced cardiac dysfunction was significantly reversed by Ang-(1-7) administration. These cardioprotective effects of Ang-(1-7) were significantly revoked by administration of the MAS receptor antagonists, A779 and D-Pro⁷-Ang-(1-7).

CONCLUSIONS

PAMAM dendrimers can impair the recovery of hearts from I/R injury in a dose-, dendrimer-generation-(size) and surface-charge dependent manner. Importantly, PAMAM-induced cardiotoxicity could be mitigated by Ang-(1-7) acting through its MAS receptor. Thus, this study highlights the activation of Ang-(1-7)/Mas receptor axis as a novel strategy to overcome dendrimer-induced cardiotoxicity.

Co-delivery of curcumin and Bcl-2 siRNA to enhance therapeutic effect against breast cancer cells using PEI-functionalized PLGA nanoparticles

PURPOSE

Breast cancer is the second major cause of death worldwide among women. Co-delivery of anticancer drugs and nucleic acids targeting the apoptosis pathway could be a promising new approach.

METHODS

In the present study, we synthesized a novel nanostructure for co-delivery of curcumin and siRNA to breast cancer cells. Curcumin-loaded polylactic-co-glycolic acid (PLGA) was synthesized using an O/W emulsion-solvent diffusion method. It was coated with polyethylenimine (PEI) and subsequently complexed with Bcl-2 siRNA. Also nanoparticles were characterized such as zeta potential, size distribution and drug encapsulation. Finally the cytotoxicity of NP and Bcl2 experession was evaluated.

RESULTS

The curcumin loaded PLGA nanoparticles were 70nm in size, and increased to 84 nm after incorporation of PEI plus Bcl-2 siRNA. The encapsulation ratio of drug in our nanoparticle was 78%. Cellular internalization PLGA-CUR-PEI/Bcl-2 siRNA NPs was confirmed by fluorescence microscopy with broadcasting of the fluorescence in the cytoplasm and into the nucleus. The results of the cell viability assay revealed that curcumin-loaded PLGA coated with PEI and Bcl-2 siRNA exhibited the highest cytotoxicity against the T47D cell line, while the siRNA decreased the Bcl-2 expression by 90.7%.

CONCLUSION

The co-delivery of curcumin plus Bcl-2 siRNA with the PLGA-PEI nanosystem could be a synergistic drug carrier against breast cancer cells.

Cationic nanoparticles enhance T cell tumor infiltration and antitumor immune responses to a melanoma vaccine

In clinical settings, cancer vaccines as monotherapies have displayed limited success compared to other cancer immunotherapeutic treatments. Nanoscale formulations have the ability to increase the efficacy of cancer vaccines by combatting the immunosuppressive nature of the tumor microenvironment. Here, we have synthesized a previously unexplored cationic polymeric nanoparticle formulation using polyamidoamine dendrimers and poly(d,l-lactic-co-glycolic acid) that demonstrate adjuvant properties in vivo. Tumor-challenged mice vaccinated with an adenovirus-based cancer vaccine [encoding tumor-associated antigen (TAA)] and subsequently treated with this nanoparticulate formulation showed significant increases in TAA-specific T cells in the peripheral blood, reduced tumor burden, protection against tumor rechallenge, and a significant increase in median survival. An investigation into cell-based pathways suggests that administration of the nanoformulation at the site of the developing tumor may have created an inflammatory environment that attracted activated TAA-specific CD8+ T cells to the vicinity of the tumor, thus enhancing the efficacy of the vaccine.

Advances of nano drug delivery system for the theranostics of ischemic stroke

From the global perspective, stroke refers to a highly common cause of disability and death. Ischemic stroke (IS), attributed to blood vessel blockage, preventing the flow of blood to brain, acts as the most common form of stroke. Thus far, thrombolytic therapy is the only clinical treatment for IS with the approval from the FDA. Moreover, the physiology barrier complicates therapeutically and diagnostically related intervention development of IS. Accordingly, developing efficient and powerful curative approaches for IS diagnosis and treatment is urgently required. The advent of nanotechnology has brought dawn and hope to better curative and imaging forms for the management of IS. This work reviews the recent advances and challenges correlated with the nano drug delivery system for IS therapy and diagnosis. The overview of the current knowledge of the important molecular pathological mechanisms in cerebral ischemia and how the drugs cross the blood brain barrier will also be briefly summarized.

Baseline and time-updated factors in preclinical development of anionic dendrimers as successful anti-HIV-1 vaginal microbicides

Although a wide variety of topical microbicides provide promising in vitro and in vivo efficacy, most of them failed to prevent sexual transmission of human immunodeficiency virus type 1 (HIV-1) in human clinical trials. In vitro, ex vivo, and in vivo models must be optimized, considering the knowledge acquired from unsuccessful and successful clinical trials to improve the current gaps and the preclinical development protocols. To date, dendrimers are the only nanotool that has advanced to human clinical trials as topical microbicides to prevent HIV-1 transmission. This fact demonstrates the importance and the potential of these molecules as microbicides. Polyanionic dendrimers are highly branched nanocompounds with potent activity against HIV-1 that disturb HIV-1 entry. Herein, the most significant advancements in topical microbicide development, trying to mimic the real-life conditions as closely as possible, are discussed. This review also provides the preclinical assays that anionic dendrimers have passed as microbicides because they can improve current antiviral treatments' efficacy. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine.

β-Cyclodextrin and Oligoarginine Peptide-Based Dendrimer-Entrapped Gold Nanoparticles for Improving Drug Delivery to the Inner Ear

Here, we developed a safe and highly effective nanocarrier using β-cyclodextrin (β-CD) and oligoarginine peptide (Arg8)-modified dendrimer-entrapped gold nanoparticles (Au@CD-PAMAM-Arg8), with a diameter of 5 nm, for improved delivery of dexamethasone (Dex) to the inner ear. The properties and in vivo distribution of the Au@CD-PAMAM-Arg8 were assessed in vitro, and a streptomycin (SM) ototoxicity model was used in vivo. Flow cytometry analysis of HEIOC1 cells treated with Au@CD-PAMAM-Arg8 and Au @CD-PAMAM at different time intervals indicated that cell uptake efficiency of the drug delivery carrier Au@CD-PAMAM-Arg8 was higher than that of Au @CD-PAMAM. Au@CD-PAMAM-Arg8 carrying Dex (Au@CD-PAMAM-Arg8/Dex) were mainly distributed in hair cells, the spiral ganglion, lateral wall, and nerve fibers and had stronger protective effects on the inner ear than Dex administration alone. In vivo tracer tests revealed that tympanic injection was significantly more effective than posterior ear injection, muscle injection, and tail vein injection, whereas clinical retro-auricular injection could not increase the efficiency of drug delivery into the ear. Electrocochleography results showed that Au@CD-PAMAM-Arg8/Dex significantly improved hearing in C57/BL6 mice after SM exposure. These findings indicate that Au@CD-PAMAM-Arg8 may be the useful drug carriers for the treatment of inner ear diseases.

Conjugation to PEG as a Strategy to Limit the Uptake of Drugs by the Placenta: Potential Applications for Drug Administration in Pregnancy

Here, we evaluated the feasibility of non-prodrug PEG-drug conjugates to decrease the accumulation of drugs within the placental tissues. The results showed that PEG was biocompatible with the human placenta with no alteration of the basal rate of proliferation or apoptosis in term placental explants. No significant changes in the released levels of lactate dehydrogenase and the human chorionic gonadotropin were observed after PEG treatment. The cellular uptake studies revealed that conjugating Cy5.5 and haloperidol to PEG significantly reduced (by up to ∼40-fold) their uptake by the placenta. These findings highlight the viability of novel non-prodrug polymer-drug conjugates to avoid the accumulation of drugs within the placenta.

Peptide-Functionalized Dendrimer Nanocarriers for Targeted Microdystrophin Gene Delivery

Gene therapy is a good alternative for determined congenital disorders; however, there are numerous limitations for gene delivery in vivo including targeted cellular uptake, intracellular trafficking, and transport through the nuclear membrane. Here, a modified G5 polyamidoamine (G5 PAMAM) dendrimer-DNA complex was developed, which will allow cell-specific targeting to skeletal muscle cells and transport the DNA through the intracellular machinery and the nuclear membrane. The G5 PAMAM nanocarrier was modified with a skeletal muscle-targeting peptide (SMTP), a DLC8-binding peptide (DBP) for intracellular transport, and a nuclear localization signaling peptide (NLS) for nuclear uptake, and polyplexed with plasmid DNA containing the GFP-tagged microdystrophin (µDys) gene. The delivery of µDys has been considered as a therapeutic modality for patients suffering from a debilitating Duchenne muscular dystrophy (DMD) disorder. The nanocarrier-peptide-DNA polyplexes were prepared with different charge ratios and characterized for stability, size, surface charge, and cytotoxicity. Using the optimized nanocarrier polyplexes, the transfection efficiency in vitro was determined by demonstrating the expression of the GFP and the µDys protein using fluorescence and Western blotting studies, respectively. Protein expression in vivo was determined by injecting an optimal nanocarrier polyplex formulation to Duchenne model mice, mdx^4Cv. Ultimately, these nanocarrier polyplexes will allow targeted delivery of the microdystrophin gene to skeletal muscle cells and result in improved muscle function in Duchenne muscular dystrophy patients.

Ionic conductive nanocomposite based on poly(l-lactic acid)/poly(amidoamine) dendrimerelectrospun nanofibrous for biomedical application

The modification of poly (l-lactic acid) (PLLA) electrospun nanofibrous scaffolds was carried out by blending with second-generation poly amidoamine (PAMAM) for enhancement of their ionic conductivity. The samples containing PLLA and various amounts of PAMAM (1%, 3%, 5%, and 7% by wt.) were fabricated by electrospinning techniques. The electrospun fibers were characterized using scanning electron microscopy (SEM), porosity, Fourier-transform infrared (FTIR) spectroscopy, differential scanning calorimetry, contact angle measurement, water uptake measurement, mechanical properties, and electrical properties. Furthermore,in vitrodegradation study and cell viability assay were investigated in biomaterial applications. Creating amide groups through aminolysis reaction was confirmed by FTIR analysis successfully. The results reveal that adding PAMAM caused an increase in fiber diameter, crystallinity percentage, hydrophilicity, water absorption, elongation-at-break, and OE-mesenchymal stem cell viability. It is worth mentioning that this is the first report investigating the conductivity of PLLA/PAMAM nanofiber. The results revealed that by increasing the amount of PAMAM, the ionic conductivity of scaffolds was enhanced by about nine times. Moreover, the outcomes indicated that the presence of PAMAM could improve the limitations of PLLA like hydrophobicity, lack of active group, and poor cell adhesion.

PAMAM-calix-dendrimers: Synthesis and Thiacalixarene Conformation Effect on DNA Binding

A convenient method for the synthesis of the first generation PAMAM dendrimers based on the thiacalix[4]arene has been developed for the first time. Three new PAMAM-calix-dendrimers with the macrocyclic core in cone, partial cone, and 1,3-alternate conformations were obtained with high yields. The interaction of the obtained compounds with salmon sperm DNA resulted in the formation of the associates of the size up to 200 nm, as shown by the UV-Vis spectroscopy, DLS, and TEM. It was demonstrated by the CD method that the structure of the DNA did not undergo significant changes upon binding. The PAMAM-calix-dendrimer based on the macrocycle in cone conformation stabilized DNA and prevented its degradation.

Emerging innate biological properties of nano-drug delivery systems: A focus on PAMAM dendrimers and their clinical potential

Drug delivery systems or vectors are usually needed to improve the bioavailability and effectiveness of a drug through improving its pharmacokinetics/pharmacodynamics at an organ, tissue or cellular level. However, emerging technologies with sensitive readouts as well as a greater understanding of physiological/biological systems have revealed that polymeric drug delivery systems are not biologically inert but can have innate or intrinsic biological actions. In this article, we review the emerging multiple innate biological/toxicological properties of naked polyamidoamine (PAMAM) dendrimer delivery systems in the absence of any drug cargo and discuss their correlation with the defined physicochemical properties of PAMAMs in terms of molecular size (generation), architecture, surface charge and chemistry. Further, we assess whether any of the reported intrinsic biological actions of PAMAMs such as their antimicrobial activity or their ability to sequester glucose and modulate key protein interactions or cell signaling pathways, can be exploited clinically such as in the treatment of diabetes and its complications.

Evaluation of Multivalent Sialylated Polyglycerols for Resistance Induction in and Broad Antiviral Activity against Influenza A Viruses

The development of multivalent sialic acid-based inhibitors active against a variety of influenza A virus (IAV) strains has been hampered by high genetic and structural variability of the targeted viral hemagglutinin (HA). Here, we addressed this challenge by employing sialylated polyglycerols (PGs). Efficacy of prototypic PGs was restricted to a narrow spectrum of IAV strains. To understand this restriction, we selected IAV mutants resistant to a prototypic multivalent sialylated PG by serial passaging. Resistance mutations mapped to the receptor binding site of HA, which was accompanied by altered receptor binding profiles of mutant viruses as detected by glycan array analysis. Specifying the inhibitor functionalization to 2,6-α-sialyllactose (SL) and adjusting the linker yielded a rationally designed inhibitor covering an extended spectrum of inhibited IAV strains. These results highlight the importance of integrating virological data with chemical synthesis and structural data for the development of sialylated PGs toward broad anti-influenza compounds.

Substantial cell apoptosis provoked by naked PAMAM dendrimers in HER2-positive human breast cancer via JNK and ERK1/ERK2 signalling pathways

HER2-positive breast cancer is one of its most challenging subtypes, forming around 15-25% of the total cases. It is characterized by aggressive behavior and treatment resistance. On the other hand, poly (amidoamine) (PAMAM) dendrimers are widely used in drug delivery systems and gene transfection as carriers. PAMAMs can modulate gene expression and interfere with transactivation of the human epidermal growth factor receptor family members (HER1-4). Nevertheless, the outcome of PAMAMs on HER2-positive breast cancer remains unknown. Thus, in this study, we investigated the anti-cancer effects of different generations of PAMAM dendrimers (G₄ and G₆) and the outcome of their surface chemistries (cationic, neutral, and anionic) on HER2-positive breast cancer cell lines, SKBR3 and ZR75. Our data showed that PAMAM dendrimers, mainly cationic types, significantly reduce cell viability in a dose-dependent manner. More significantly, PAMAMs induce substantial cell apoptosis, accompanied by the up-regulation of apoptotic markers (Bax, Caspases-3, 8 and 9) in addition to down-regulation of Bcl-2. Moreover, our data pointed out that cationic PAMAMs inhibit colony formation compared to controls and other types of PAMAMs. The molecular pathway analysis of PAMAM exposed cells revealed that PAMAMs enhance JNK1/2/3 expression while blocking ERK1/2, in addition to EGFR1 (HER1) and HER2 activities, which could be the major molecular pathway behind these events. These observed effects were comparable to lapatinib treatment, a clinically used inhibitor of HER1 and 2 receptors phosphorylation. Our findings implicate that PAMAMs may possess important therapeutic effects against HER2-positive breast cancer via JNK1/2/3, ERK1/2, and HER1/2 signalling pathways.

Peptide-Modified Biopolymers for Biomedical Applications

Polymeric biomaterials have been used in a variety of applications, like cargo delivery and tissue scaffolding, because they are easily synthesized and can be adapted to many systems. However, there is still a need to further enhance and improve their functions to progress their use in the biomedical field. A promising solution is to modify the polymer surfaces with peptides that can increase biocompatibility, cellular interactions, and receptor targeting. In recent years, peptide modifications have been used to overcome many challenges to polymer biomaterial development. This review discusses recent progress in developing peptide-modified polymers for therapeutic applications including cell-specific targeting and tissue engineering. Furthermore, we will explore some of the most frequently studied base components of these biomaterials.

The Therapeutic Efficacy of Dendrimer and Micelle Formulations for Breast Cancer Treatment

Breast cancer is among the most common types of cancer in women and it is the cause of a high rate of mortality globally. The use of anticancer drugs is the standard treatment approach used for this type of cancer. However, most of these drugs are limited by multi-drug resistance, drug toxicity, poor drug bioavailability, low water solubility, poor pharmacokinetics, etc. To overcome multi-drug resistance, combinations of two or more anticancer drugs are used. However, the combination of two or more anticancer drugs produce toxic side effects. Micelles and dendrimers are promising drug delivery systems that can overcome the limitations associated with the currently used anticancer drugs. They have the capability to overcome drug resistance, reduce drug toxicity, improve the drug solubility and bioavailability. Different classes of anticancer drugs have been loaded into micelles and dendrimers, resulting in targeted drug delivery, sustained drug release mechanism, increased cellular uptake, reduced toxic side effects of the loaded drugs with enhanced anticancer activity in vitro and in vivo. This review article reports the biological outcomes of dendrimers and micelles loaded with different known anticancer agents on breast cancer in vitro and in vivo.

Glycosylated Nanoparticles for Cancer-Targeted Drug Delivery

Nanoparticles (NPs) are novel platforms that can carry both cancer-targeting molecules and drugs to avoid severe side effects due to nonspecific drug delivery in standard chemotherapy treatments. Cancer cells are characterized by abnormal membranes, metabolic changes, the presence of lectin receptors, glucose transporters (GLUT) overexpression, and glycosylation of immune receptors of programmed death on cell surfaces. These characteristics have led to the development of several strategies for cancer therapy, including a large number of carbohydrate-modified NPs, which have become desirable for use in cell-selective drug delivery systems because they increase nanoparticle-cell interactions and uptake of carried drugs. Currently, the potential of NP glycosylation to enhance the safety and efficacy of carried therapeutic antitumor agents has been widely acknowledged, and much information is accumulating in this field. This review seeks to highlight recent advances in NP stabilization, toxicity reduction, and pharmacokinetic improvement and the promising potential of NP glycosylation from the perspective of molecular mechanisms described for drug delivery systems for cancer therapy. From preclinical proof-of-concept to demonstration of therapeutic value in the clinic, the challenges and opportunities presented by glycosylated NPs, with a focus on their applicability in the development of nanodrugs, are discussed in this review.

Nanotechnological strategies for systemic microbial infections treatment: A review

Systemic infections is one of the major causes of mortality worldwide, and a shortage of drug approaches applied for the rapid and necessary treatment contribute to increase the levels of death in affected patients. Several drug delivery systems based in nanotechnology such as metallic nanoparticles, liposomes, nanoemulsion, microemulsion, polymeric nanoparticles, solid lipid nanoparticles, dendrimers, hydrogels and liquid crystals can contribute in the biological performance of active substances for the treatment of microbial diseases triggered by fungi, bacteria, virus and parasites. In the presentation of these statements, this review article present and demonstrate the effectiveness of these drug delivery systems for the treatment of systemic diseases caused by several microorganisms, through a review of studies on scientific literature worldwide that contributes to better information for the most diverse professionals from the areas of health sciences. The studies demonstrated that the drug delivery systems described can contribute to the therapeutic scenario of these diseases, being classified as safe, active platforms and with therapeutic versatility.

Cell death-inducing properties of selected dendrimers against different breast cancer and leukemia cell lines

Dendrimers represent an opportunity for targeted drug delivery into tumor cells. This is facilitated, for example, by loading of dendrimers with anticancer compounds. However, to assess the effects caused by such conjugates, knowledge of the cytotoxicity of the dendrimers themselves is necessary. The poly(amido amine)-derived dendrimers G₁ (Phe)₆ , G₁ (Dan)₃ , and G₂ were selected due to their different numbers of free amino groups and the poly(propylene imine) (PPI) dendrimer PPI-G₃ served as a reference. The compounds were evaluated for cell-death induction using breast cancer (MCF-7, MDA-MB-231) and leukemia (LAMA-84, K562, SD-1, SUP-B15) cell lines. The compounds exhibited concentration-dependent effects in the low micromolar range against the mammary carcinoma cells. A dependency on the generation, and particularly on the type of dendrimer, was deduced while the quantity of the free amino groups was subsidiary. G₂ revealed to be most cytotoxic, also against all tested leukemia cell lines. The cell line SD-1, however, was susceptible to all dendrimers. The mode of cell death was mainly determined by necrosis, especially at higher concentrations, while apoptosis played a subordinate role. The other dendrimers exerted no antimetabolic effects against LAMA-84, K562, and SUP-B15 cells. Therefore, these dendrimers are generally suitable as nontoxic drug carriers for leukemia cells.

Efficient modification of PAMAM G1 dendrimer surface with β-cyclodextrin units by CuAAC: impact on the water solubility and cytotoxicity

The toxicity of the poly(amidoamine) dendrimers (PAMAM) caused by the peripheral amino groups has been a limitation for their use as drug carriers in clinical applications. In this work, we completely modified the periphery of PAMAM dendrimer generation 1 (PAMAM G1) with β-cyclodextrin (β-CD) units through the Cu(i)-catalyzed azide–alkyne cycloaddition (CuAAC) to obtain the PAMAM G1-β-CD dendrimer with high yield. The PAMAM G1-β-CD was characterized by ¹H- and ¹³C-NMR and mass spectrometry studies. Moreover, the PAMAM G1-β-CD dendrimer showed remarkably higher water solubility than native β-CD. Finally, we studied the toxicity of PAMAM G1-β-CD dendrimer in four different cell lines, human breast cancer cells (MCF-7 and MDA-MB-231), human cervical adenocarcinoma cancer cells (HeLa) and pig kidney epithelial cells (LLC-PK1). The PAMAM G1-β-CD dendrimer did not present any cytotoxicity in cell lines tested which shows the potentiality of this new class of dendrimers.

The toxicity of the poly(amidoamine) dendrimers (PAMAM) caused by the peripheral amino groups has been a limitation for their use as drug carriers in clinical applications.

Nanotoxicology of Dendrimers in the Mammalian Heart: ex vivo and in vivo Administration of G6 PAMAM Nanoparticles Impairs Recovery of Cardiac Function Following Ischemia-Reperfusion Injury

Aim

The effects of polyamidoamine (PAMAM) dendrimers on the mammalian heart are not completely understood. In this study, we have investigated the effects of a sixth-generation cationic dendrimer (G6 PAMAM) on cardiac function in control and diabetic rat hearts following ischemia-reperfusion (I/R) injury.

Methods

Isolated hearts from healthy non-diabetic (Ctr) male Wistar rats were subjected to ischemia and reperfusion (I/R). LV contractility and hemodynamics data were computed digitally whereas cardiac damage following I/R injury was assessed by measuring cardiac enzymes. For ex vivo acute exposure experiments, G6 PAMAM was administered during the first 10 mins of reperfusion in Ctr animals. In chronic in vivo studies, nondiabetic rats (Ctr) received either vehicle or daily i.p. injections of G6 PAMAM (40 mg/kg) for 4 weeks. Diabetic (D) animals received either vehicle or daily i.p. injections of G6 PAMAM (10, 20 or 40 mg/kg) for 4 weeks. The impact of G6 PAMAM on pacing-postconditioning (PPC) was also studied in Ctr and D rats.

Results

In ex vivo studies, acute administration of G6 PAMAM to isolated Ctr hearts during reperfusion dose-dependently impaired recovery of cardiac hemodynamics and vascular dynamics parameters following I/R injury. Chronic daily i.p. injections of G6 PAMAM significantly (P<0.01) impaired recovery of cardiac function following I/R injury in nondiabetic animals but this was not generally observed in diabetic animals except for CF which was impaired by about 50%. G6 PAMAM treatment completely blocked the protective effects of PPC in the Ctr animals.

Conclusion

Acute ex vivo or chronic in vivo treatment with naked G6 PAMAM dendrimer can significantly compromise recovery of non-diabetic hearts from I/R injury and can further negate the beneficial effects of PPC. Our findings are therefore extremely important in the nanotoxicological evaluation of G6 PAMAM dendrimers for potential clinical applications in physiological and pathological settings.

Quantitative imaging of the receptor for advanced glycation end-products in prostate cancer

PURPOSE

Current screening and monitoring of prostate cancer (PCa) is insufficient, producing inaccurate diagnoses. Presence of the receptor for advanced glycation end-products (RAGE) is associated with signature characteristics of PCa development such as cell proliferation, anchorage-independent growth, angiogenesis, migration, invasion, and poor patient survival. Therefore, we developed a preclinical multimodal imaging strategy targeted at RAGE to diagnose and monitor PCa.

METHODS

In this work, RAGE-targeted multimodal nanoparticles (64Cu-Cy5-G4-CML) were synthesized and rendered functional for nuclear and optical imaging using previously established methods. The probe's binding affinity and targeting specificity was assessed in androgen-dependent (LNCaP) and androgen-independent (DU145) prostate cancer cells using flow cytometry and confocal microscopy. In vivo PET-CT imaging was used to evaluate RAGE levels in DU145 and LNCaP xenograft models in mice. Then, tumors were excised post-imaging for histological staining and autoradiography to further assess RAGE levels and targeting efficiency of the tracer. Finally, RAGE levels from human PCa samples of varying Gleason Scores were evaluated using Western blot and immunohistochemical staining.

RESULTS

PCa cell culture studies confirmed adequate RAGE-targeting with 64Cu-Cy5-G4-CML with K_D between 360 and 540 nM as measured by flow cytometry. In vivo PET-CT images of PCa xenografts revealed favorable kinetics, rapid blood clearance, and a non-homogenous, enhanced uptake in tumors, which varied based on cell type and tumor size with mean uptake between 0.5 and 1.4%ID/g. RAGE quantification of human samples confirmed increased RAGE uptake corresponding to increased Gleason scoring.

CONCLUSIONS

Our study has shown that RAGE-targeted cancer imaging is feasible and could significantly impact PCa management.

Bone-targeted PAMAM nanoparticle to treat bone metastases of lung cancer

Aim: To prepare pH-sensitive nanoparticle composed of alendronate (ALN) and poly(amidoamine) (PAMAM) to treat bone metastases of lung cancer. Methods: The solvent evaporation method was used to prepare docetaxel (DTX)-loaded ALN-PAMAM nanoparticles (DTX@ALN-PAMAM). Results: The in vitro results showed DTX@ALN-PAMAM significantly enhanced the anticancer activity of DTX and inhibited the formation of osteoclasts. DTX@ALN-PAMAM concentrated at bone metastasis site in mice, which resulted in the suppression of bone resorption, pain response and growth of bone metastases. Eventually, the therapeutic effect of DTX on bone metastases of lung cancer was obviously improved. Conclusion: ALN modified PAMAM nanoparticle could be an effective platform for the treatment of bone metastases of lung cancer.

Soft and Condensed Nanoparticles and Nanoformulations for Cancer Drug Delivery and Repurpose

Drug repurpose or reposition is recently recognized as a high-performance strategy for developing therapeutic agents for cancer treatment. This approach can significantly reduce the risk of failure, shorten R&D time, and minimize cost and regulatory obstacles. On the other hand, nanotechnology-based delivery systems are extensively investigated in cancer therapy due to their remarkable ability to overcome drug delivery challenges, enhance tumor specific targeting, and reduce toxic side effects. With increasing knowledge accumulated over the past decades, nanoparticle formulation and delivery have opened up a new avenue for repurposing drugs and demonstrated promising results in advanced cancer therapy. In this review, recent developments in nano-delivery and formulation systems based on soft (i.e., DNA nanocages, nanogels, and dendrimers) and condensed (i.e., noble metal nanoparticles and metal-organic frameworks) nanomaterials, as well as their theranostic applications in drug repurpose against cancer are summarized.

Dendrimeric calcium-sensitive MRI probes: the first low-field relaxometric study

In the present work the first investigation ever of calcium sensitive dendrimer relaxation mechanisms at low fields is reported.

Therapeutic efficacy of nanoparticles and routes of administration

In modern-day medicine, nanotechnology and nanoparticles are some of the indispensable tools in disease monitoring and therapy. The term “nanomaterials” describes materials with nanoscale dimensions (< 100 nm) and are broadly classified into natural and synthetic nanomaterials. However, “engineered” nanomaterials have received significant attention due to their versatility. Although enormous strides have been made in research and development in the field of nanotechnology, it is often confusing for beginners to make an informed choice regarding the nanocarrier system and its potential applications. Hence, in this review, we have endeavored to briefly explain the most commonly used nanomaterials, their core properties and how surface functionalization would facilitate competent delivery of drugs or therapeutic molecules. Similarly, the suitability of carbon-based nanomaterials like CNT and QD has been discussed for targeted drug delivery and siRNA therapy. One of the biggest challenges in the formulation of drug delivery systems is fulfilling targeted/specific drug delivery, controlling drug release and preventing opsonization. Thus, a different mechanism of drug targeting, the role of suitable drug-laden nanocarrier fabrication and methods to augment drug solubility and bioavailability are discussed. Additionally, different routes of nanocarrier administration are discussed to provide greater understanding of the biological and other barriers and their impact on drug transport. The overall aim of this article is to facilitate straightforward perception of nanocarrier design, routes of various nanoparticle administration and the challenges associated with each drug delivery method.

Co-delivery of doxorubicin and TRAIL plasmid by modified PAMAM dendrimer in colon cancer cells, in vitro and in vivo evaluation

One strategy for cancer treatment is combination therapy using nanoparticles (NPs), which has resulted in enhanced anti-cancer effects and reduced cytotoxicity of therapeutic agents. Polyamidoamine dendrimer (PAMAM) has attracted considerable attention because of its potential applications ranging from drug delivery to molecular encapsulation and gene therapy. In this study, PAMAM G5 modified with cholesteryl chloroformate and alkyl-PEG was applied for co-delivery of doxorubicin (DOX) and plasmid encoding TRAIL into colon cancer cells, in vitro and in vivo. The results showed DOX was efficiently encapsulated in modified carrier (M-PAMAM) with loading level about 90%, and the resulting DOX-loaded M-PAMAM complexed with TRAIL plasmid showed much stronger antitumor effect than M-PAMAM containing DOX or TRAIL plasmid. On the other hand, the obtained results demonstrated that the treatment of mice bearing C26 colon carcinoma with this developed co-delivery system significantly decreased tumor growth rate. Thus, this modified PAMAM G5 can be considered as a potential carrier for co-delivery of drug and gene in cancer therapy.

Citrullinated Peptide Epitope Targets Therapeutic Nanoparticles to Human Neutrophils

Multiple drugs have been proposed for reducing harsh symptoms of human rheumatic diseases. However, a targeted therapy with mild to no side effects is still missing. In this study, we have prepared and tested a series of therapeutic nanoparticles for specific targeting of human neutrophils associated with rheumatoid arthritis. In doing this, a series of citrullinated peptide epitopes derived from human proteins, fibrinogen, vimentin, and histone 3, were screened with regard to specific recognition of neutrophils. The most potent epitope proved to be a mutated fragment of an alpha chain in human fibrinogen. Next, a straightforward synthetic strategy was developed for nanoparticles decorated with this citrullinated peptide epitope and an antisense oligonucleotide targeting disease associated microRNA miR-125b-5p. Our study shows that the nanoparticles specifically recognize neutrophils and knock down miR-125b-5p, with no apparent toxicity to human cells. In contrast to organic dendrimers, chitosan-hyaluronic acid formulations do not activate human innate immune response. Our data proves that the strategy we report herein is effective in developing peptide epitopes for decorating delivery vehicles bearing biological drugs, targeted to a specific cell type.

Dendrimer Based Nanoarchitectures in Diabetes Management: An Overview

Diabetes has turned out to be one of the biggest worldwide health and economic burdens, with its expanded predominance and high complexity proportion. The quantity of diabetic patients is expanding enormously around the world. Several reports have demonstrated the sharp increment in the sufferers. Stable and acceptable blood glucose control is fundamental to diminish diabetes-related complications. Consequently, ceaseless endeavors have been made in antidiabetic drugs, treatment strategies, and nanotechnology based products to accomplish better diabetes control. The nanocarriers pertaining hypoglycaemics provide improved diabetes management with minimum risk of associated side effects. Dendrimers have caught an incredible attention in the field of drug delivery and personalized medicines. Dendrimers are three-dimensional well-defined homogenous nanosized structures consisting tree-like branches. The present review highlights the different aspects of dendrimers including fabrication, surface engineering, toxicological profile as well as delivery of antidiabetic drugs for the effective cure of diabetes.

Rising horizon in circumventing multidrug resistance in chemotherapy with nanotechnology

Multidrug resistance (MDR) is one of the key barriers in chemotherapy, leading to the generation of insensitive cancer cells towards administered therapy. Genetic and epigenetic alterations of the cells are the consequences of MDR, resulted in drug resistivity, which reflects in impaired delivery of cytotoxic agents to the cancer site. Nanotechnology-based nanocarriers have shown immense shreds of evidence in overcoming these problems, where these promising tools handle desired dosage load of hydrophobic chemotherapeutics to facilitate designing of safe, controlled and effective delivery to specifically at tumor microenvironment. Therefore, encapsulating drugs within the nano-architecture have shown to enhance solubility, bioavailability, drug targeting, where co-administered P-gp inhibitors have additionally combat against developed MDR. Moreover, recent advancement in the stimuli-sensitive delivery of nanocarriers facilitates a tumor-targeted release of the chemotherapeutics to reduce the associated toxicities of chemotherapeutic agents in normal cells. The present article is focused on MDR development strategies in the cancer cell and different nanocarrier-based approaches in circumventing this hurdle to establish an effective therapy against deadliest cancer disease.