Can dendrimer based nanoparticles fight neurodegenerative diseases? Current situation versus other established approaches

Emerging nano-derived therapy for the treatment of dementia: a comprehensive review

Dementia includes a variety of neurodegenerative diseases that affect and target the brain's fundamental cognitive functions. It is undoubtedly one of the diseases that affects people globally. The ameliorating the disease is still not known; the symptoms, however, can be prevented to an extent. Dementia encompasses Alzheimer's disease, Parkinson's disease, Huntington's disease, Lewy body dementia, mixed dementia, and various other diseases. The aggregation of β-amyloid protein plaques and the formation of neurofibrillary tangles have been concluded as the foremost cause for the onset of the disease. As the cases climb, new neuroprotective methods are being developed in the form of new drug delivery systems that provide targeted delivery. Herbal drugs like Ashwagandha, Brahmi, and Cannabis have shown satisfactory results by not only treating the symptoms but have also been shown to reduce and ameliorate the formation of amyloid plaque formation. This article explores the intricate possibilities of drug delivery and the absolute use of herbal drugs to target neurodegenerative diseases. The various possibilities of nanotechnology currently available with new emerging techniques are also discussed.

Nanoodor Particles Deliver Drugs to Central Nervous System via Olfactory Pathway

Central nervous system (CNS) disorders confront significant challenges in drug delivery due to the blood-brain barrier (BBB). Inspired by the rapid and precise binding of odor molecules to olfactory receptors (ORs), this research uses thiolated HPMA to construct odor nanoparticles (nanoodors) capable of delivering drugs to the CNS via the olfacto-cerebral pathway to overcome the delivery obstruction. The nanoodor core is used to encapsulate agomelatine (AGO), a CNS-targeting antidepressant, and the encapsulation efficiency exceeded 80%. A series of thiol-presenting nanoscale structures with different surface densities of thiol groups are constructed, and the effectiveness positively correlated with the density of thiol groups on their surface. Notably, the nanoodors enable precise brain-targeted delivery, outperforming commercially available oral formulations in terms of drug accumulation in the brain and antidepressant effects. The study of the nanoodor transport and action mechanisms revealed that after binding to ORs, the nanoodors are rapidly delivered to the brain via the olfactory pathway. Nanoodors, the first design to deliver CNS drugs via the olfactory pathway by mimicking natural smells for the treatment of CNS disorders, are expected to achieve clinical transformation, benefiting human health.

Design of reversible cholinesterase inhibitors: Fine-tuning of enzymatic activity by PAMAM-calix-dendrimers

Reversible cholinesterase (ChE) inhibitors are widely used drugs for the therapy of various cognitive and neurodegenerative disorders. The development of a "universal drug" with easily tunable ChE inhibition activity is a relevant interdisciplinary problem. Here we propose for the first time the design of novel "fine-tuned" ChE inhibitors based on dendrimers with a thiacalix[4]arene core (PAMAM-calix-dendrimers). A series of first-generation PAMAM-calix-dendrimers with different terminal fragments were designed and synthesized. The human acetylcholinesterase and butyrylcholinesterase inhibition by PAMAM-calix-dendrimers was confirmed by molecular docking and in vitro studies. PAMAM-calix-dendrimers were found to have IC50 values for acetylcholinesterase and butyrylcholinesterase in the range of 0.076-5400 μM. Relationships between the structure of PAMAM-calix-dendrimers and the ChE inhibitory activity were established. The conformation of the macrocyclic core and the nature of the terminal groups were found to exert a direct impact on the inhibitory activity of dendrimers. We anticipate our study to be a starting point for creation of "universal drug" with tunable ChE inhibitory activity to specific therapeutic targets, and more sophisticated in vivo studies of such systems.

Advances in nanotechnology-assisted photodynamic therapy for neurological disorders: a comprehensive review

Neurological disorders such as neurodegenerative diseases and nervous system tumours affect more than one billion people throughout the globe. The physiological sensitivity of the nervous tissue limits the application of invasive therapies and leads to poor treatment and prognosis. One promising solution that has generated attention is Photodynamic therapy (PDT), which can potentially revolutionise the treatment landscape for neurological disorders. PDT attracted substantial recognition for anticancer efficacy and drug conjugation for targeted drug delivery. This review thoroughly explained the basic principles of PDT, scientific interventions and advances in PDT, and their complicated mechanism in treating brain-related pathologies. Furthermore, the merits and demerits of PDT in the context of neurological disorders offer a well-rounded perspective on its feasibility and challenges. In conclusion, this review encapsulates the significant potential of PDT in transforming the treatment landscape for neurological disorders, emphasising its role as a non-invasive, targeted therapeutic approach with multifaceted applications.

Phosphorus-carrying cascade molecules: inner architecture to biomedical applications

Cascade molecules are nearly uniform-sized macromolecules of small molecules or linear polymer cores built around symmetric branching units. A wide range of biological properties can be achieved with phosphorus-containing dendrimers, depending on their terminal functions, ranging from biomaterials to imaging, drug delivery, and acting as a drug by themselves. This feature article presents significant examples of phosphorus-containing dendrimers used to develop biochips, support cell cultures, carry or deliver biomacromolecules and drugs, bioimaging, and combinational benefits. Because of the thermal stability, ferrocene function, and physical and chemical properties of phosphorus, dendrimers show greater rigidity, mobility, and strength. These dendrimers will be discussed as having a favorable effect on cell growths, especially on neuronal cells, as well as human immune cells like natural killer cells and monocytes, which have a crucial part in preventing cancerous and viral infections. Several phosphorus dendrimers are effective as drugs by themselves (drug per se) and show their activity against neurodegenerative diseases, cancer, inflammation, ocular hypertension, and transmissible spongiform encephalopathies (TSEs) in both in vivo and in vitro. The present review discusses the synthetic route, fabrications, and biomedical applications of phosphorus-containing dendrimers. The toxicity of these dendrimers was also reported.

Mitochondrial dysfunction and oxidative stress in Alzheimer's disease, and Parkinson's disease, Huntington's disease and Amyotrophic Lateral Sclerosis -An updated review

Misfolded proteins in the central nervous system can induce oxidative damage, which can contribute to neurodegenerative diseases in the mitochondria. Neurodegenerative patients face early mitochondrial dysfunction, impacting energy utilization. Amyloid-ß and tau problems both have an effect on mitochondria, which leads to mitochondrial malfunction and, ultimately, the onset of Alzheimer's disease. Cellular oxygen interaction yields reactive oxygen species within mitochondria, initiating oxidative damage to mitochondrial constituents. Parkinson's disease, linked to oxidative stress, α-synuclein aggregation, and inflammation, results from reduced brain mitochondria activity. Mitochondrial dynamics profoundly influence cellular apoptosis via distinct causative mechanisms. The condition known as Huntington's disease is characterized by an expansion of polyglutamine, primarily impactingthe cerebral cortex and striatum. Research has identified mitochondrial failure as an early pathogenic mechanism contributing to HD's selective neurodegeneration. The mitochondria are organelles that exhibit dynamism by undergoing fragmentation and fusion processes to attain optimal bioenergetic efficiency. They can also be transported along microtubules and regulateintracellular calcium homeostasis through their interaction with the endoplasmic reticulum. Additionally, the mitochondria produce free radicals. The functions of eukaryotic cells, particularly in neurons, have significantly deviated from the traditionally assigned role of cellular energy production. Most of them areimpaired in HD, which may lead to neuronal dysfunction before symptoms manifest. This article summarises the most important changes in mitochondrial dynamics that come from neurodegenerative diseases including Alzheimer's, Parkinson's, Huntington's and Amyotrophic Lateral Sclerosis. Finally, we discussed about novel techniques that can potentially treat mitochondrial malfunction and oxidative stress in four most dominating neuro disorders.

Dendrimers and Derivatives as Multifunctional Nanotherapeutics for Alzheimer's Disease

Alzheimer's disease (AD) is the most prevalent form of dementia. It affects more than 30 million people worldwide and costs over US$ 1.3 trillion annually. AD is characterized by the brain accumulation of amyloid β peptide in fibrillar structures and the accumulation of hyperphosphorylated tau aggregates in neurons, both leading to toxicity and neuronal death. At present, there are only seven drugs approved for the treatment of AD, of which only two can slow down cognitive decline. Moreover, their use is only recommended for the early stages of AD, meaning that the major portion of AD patients still have no disease-modifying treatment options. Therefore, there is an urgent need to develop efficient therapies for AD. In this context, nanobiomaterials, and dendrimers in particular, offer the possibility of developing multifunctional and multitargeted therapies. Due to their intrinsic characteristics, dendrimers are first-in-class macromolecules for drug delivery. They have a globular, well-defined, and hyperbranched structure, controllable nanosize and multivalency, which allows them to act as efficient and versatile nanocarriers of different therapeutic molecules. In addition, different types of dendrimers display antioxidant, anti-inflammatory, anti-bacterial, anti-viral, anti-prion, and most importantly for the AD field, anti-amyloidogenic properties. Therefore, dendrimers can not only be excellent nanocarriers, but also be used as drugs per se. Here, the outstanding properties of dendrimers and derivatives that make them excellent AD nanotherapeutics are reviewed and critically discussed. The biological properties of several dendritic structures (dendrimers, derivatives, and dendrimer-like polymers) that enable them to be used as drugs for AD treatment will be pointed out and the chemical and structural characteristics behind those properties will be analysed. The reported use of these nanomaterials as nanocarriers in AD preclinical research is also presented. Finally, future perspectives and challenges that need to be overcome to make their use in the clinic a reality are discussed.

Dendrimers in Alzheimer’s Disease: Recent Approaches in Multi-Targeting Strategies

Nanomaterials play an increasingly important role in current medicinal practice. As one of the most significant causes of human mortality, and one that is increasing year by year, Alzheimer’s disease (AD) has been the subject of a very great body of research and is an area in which nanomedicinal approaches show great promise. Dendrimers are a class of multivalent nanomaterials which can accommodate a wide range of modifications that enable them to be used as drug delivery systems. By means of suitable design, they can incorporate multiple functionalities to enable transport across the blood–brain barrier and subsequently target the diseased areas of the brain. In addition, a number of dendrimers by themselves often display therapeutic potential for AD. In this review, the various hypotheses relating to the development of AD and the proposed therapeutic interventions involving dendrimer–base systems are outlined. Special attention is focused on more recent results and on the importance of aspects such as oxidative stress, neuroinflammation and mitochondrial dysfunction in approaches to the design of new treatments.

Applications of Various Types of Nanomaterials for the Treatment of Neurological Disorders

Neurological disorders (NDs) are recognized as one of the major health concerns globally. According to the World Health Organization (WHO), neurological disorders are one of the main causes of mortality worldwide. Neurological disorders include Alzheimer’s disease, Parkinson′s disease, Huntington′s disease, Amyotrophic lateral sclerosis, Frontotemporal dementia, Prion disease, Brain tumor, Spinal cord injury, and Stroke. These diseases are considered incurable diseases because no specific therapies are available to cross the blood-brain barrier (BBB) and reach the brain in a significant amount for the pharmacological effect in the brain. There is a need for the development of strategies that can improve the efficacy of drugs and circumvent BBB. One of the promising approaches is the use of different types of nano-scale materials. These nano-based drugs have the ability to increase the therapeutic effect, reduce toxicity, exhibit good stability, targeted delivery, and drug loading capacity. Different types and shapes of nanomaterials have been widely used for the treatment of neurological disorders, including quantum dots, dendrimers, metallic nanoparticles, polymeric nanoparticles, carbon nanotubes, liposomes, and micelles. These nanoparticles have unique characteristics, including sensitivity, selectivity, and the ability to cross the BBB when used in nano-sized particles, and are widely used for imaging studies and treatment of NDs. In this review, we briefly summarized the recent literature on the use of various nanomaterials and their mechanism of action for the treatment of various types of neurological disorders.

Fluorescent-based nanosensors for selective detection of a wide range of biological macromolecules: A comprehensive review

Thanks to their unique attributes, such as good sensitivity, selectivity, high surface-to-volume ratio, and versatile optical and electronic properties, fluorescent-based bioprobes have been used to create highly sensitive nanobiosensors to detect various biological and chemical agents. These sensors are superior to other analytical instrumentation techniques like gas chromatography, high-performance liquid chromatography, and capillary electrophoresis for being biodegradable, eco-friendly, and more economical, operational, and cost-effective. Moreover, several reports have also highlighted their application in the early detection of biomarkers associated with drug-induced organ damage such as liver, kidney, or lungs. In the present work, we comprehensively overviewed the electrochemical sensors that employ nanomaterials (nanoparticles/colloids or quantum dots, carbon dots, or nanoscaled metal-organic frameworks, etc.) to detect a variety of biological macromolecules based on fluorescent emission spectra. In addition, the most important mechanisms and methods to sense amino acids, protein, peptides, enzymes, carbohydrates, neurotransmitters, nucleic acids, vitamins, ions, metals, and electrolytes, blood gases, drugs (i.e., anti-inflammatory agents and antibiotics), toxins, alkaloids, antioxidants, cancer biomarkers, urinary metabolites (i.e., urea, uric acid, and creatinine), and pathogenic microorganisms were outlined and compared in terms of their selectivity and sensitivity. Altogether, the small dimensions and capability of these nanosensors for sensitive, label-free, real-time sensing of chemical, biological, and pharmaceutical agents could be used in array-based screening and in-vitro or in-vivo diagnostics. Although fluorescent nanoprobes are widely applied in determining biological macromolecules, unfortunately, they present many challenges and limitations. Efforts must be made to minimize such limitations in utilizing such nanobiosensors with an emphasis on their commercial developments. We believe that the current review can foster the wider incorporation of nanomedicine and will be of particular interest to researchers working on fluorescence technology, material chemistry, coordination polymers, and related research areas.

Dendrimers as Antiamyloid Agents

Dendrimer-protein conjugates have significant prospects for biological applications. The complexation changes the biophysical behavior of both proteins and dendrimers. The dendrimers could influence the secondary structure of proteins, zeta-potential, distribution of charged regions on the surface, the protein-protein interactions, etc. These changes offer significant possibilities for the application of these features in nanotheranostics and biomedicine. Based on the dendrimer-protein interactions, several therapeutic applications of dendrimers have emerged. Thus, the formation of stable complexes retains the disordered proteins on the aggregation, which is especially important in neurodegenerative diseases. To clarify the origin of these properties and assess the efficiency of action, the mechanism of protein-dendrimer interaction and the nature and driving force of binding are considered in this review. The review outlines the antiamyloid activity of dendrimers and discusses the effect of dendrimer structures and external factors on their antiamyloid properties.

A Review of the Common Neurodegenerative Disorders: Current Therapeutic Approaches and the Potential Role of Nanotherapeutics

Neurodegenerative disorders are primarily characterized by neuron loss. The most common neurodegenerative disorders include Alzheimer’s and Parkinson’s disease. Although there are several medicines currently approved for managing neurodegenerative disorders, a large majority of them only help with associated symptoms. This lack of pathogenesis-targeting therapies is primarily due to the restrictive effects of the blood–brain barrier (BBB), which keeps close to 99% of all “foreign substances” out of the brain. Since their discovery, nanoparticles have been successfully used for targeted delivery into many organs, including the brain. This review briefly describes the pathophysiology of Alzheimer’s, Parkinson’s disease, and amyotrophic lateral sclerosis, and their current management approaches. We then highlight the major challenges of brain-drug delivery, followed by the role of nanotherapeutics for the diagnosis and treatment of various neurological disorders.

Interaction of multicomponent anionic liposomes with cationic pyridylphenylene dendrimer: Does the complex behavior depend on the liposome composition?

Dendrimers are individual macromolecular compounds having a great potential for biomedical application. The key step of the cell penetration by dendrimers is the interaction with lipid bilayer. Here, the interaction between cationic pyridylphenylene dendrimer of third generation (D₃⁵⁰⁺) and multicomponent liquid (CL/POPC), solid (CL/DPPC) and cholesterol-containing (CL/POPC/30% Chol) anionic liposomes was investigated by dynamic light scattering, fluorescence spectroscopy, conductometry, calorimetric studies and molecular dynamic (MD) simulations. Microelectrophoresis and MD simulations revealed the interaction is electrostatic and reversible with only part of pyridinium groups of dendrimers involved in binding with liposomes. The ability of dendrimer molecules to migrate between liposomes was discovered by the labeling liposomes with Rhodamine B. The phase state of the lipid membrane and the incorporation of cholesterol into the lipid bilayer were found to not affect the mechanism of the dendrimer - liposome complex formation. Rigid dendrimer adsorption on liposomal surface does not induce the formation of significant defects in the lipid membrane pave the way for possible biological application of pyridylphenylene dendrimers.

Cationic Carbosilane Dendrimers Prevent Abnormal α-Synuclein Accumulation in Parkinson's Disease Patient-Specific Dopamine Neurons

Accumulation of misfolded α-synuclein (α-syn) is a hallmark of Parkinson’s disease (PD) thought to play important roles in the pathophysiology of the disease. Dendritic systems, able to modulate the folding of proteins, have emerged as promising new therapeutic strategies for PD treatment. Dendrimers have been shown to be effective at inhibiting α-syn aggregation in cell-free systems and in cell lines. Here, we set out to investigate the effects of dendrimers on endogenous α-syn accumulation in disease-relevant cell types from PD patients. For this purpose, we chose cationic carbosilane dendrimers of bow-tie topology based on their performance at inhibiting α-syn aggregation in vitro. Dopamine neurons were differentiated from induced pluripotent stem cell (iPSC) lines generated from PD patients carrying the LRRK2^G2019S mutation, which reportedly display abnormal accumulation of α-syn, and from healthy individuals as controls. Treatment of PD dopamine neurons with non-cytotoxic concentrations of dendrimers was effective at preventing abnormal accumulation and aggregation of α-syn. Our results in a genuinely human experimental model of PD highlight the therapeutic potential of dendritic systems and open the way to developing safe and efficient therapies for delaying or even halting PD progression.

Comparison of the effects of dendrimer, micelle and silver nanoparticles on phospholipase A2 structure

The interaction of nanoparticles (NP) with proteins (the so-called 'protein corona') is a huge challenge in attempting to apply them in personalized nanomedicine. We have analyzed the interaction between A) two 'soft' NPs (a cationic phosphorus dendrimer of generation 3; a cationic phosphorus amphiphilic dendron of generation 2), and B) one 'hard' nanoparticle (silver NP covered with cationic carbosilane dendritic moieties); and membrane-bound protein phospholipase A2 from bovine pancreas. The hard and soft NPs have differences in the nature of their interactions with phospholipase A2. This enzyme surrounds hard AgNP, whereas dendrimer and amphiphilic dendron form aggregates/micelles with phospholipase A2. There is a difference in action of phospholipase A2 bound to the core of dendrimer, and of micelles formed from non-covalent interactions between the amphiphilic dendron. These data are important in understanding the nature of interaction between different kinds of nanoparticles and proteins.

Nanoparticles for drug delivery in Parkinson's disease

Although effective symptomatic treatments for Parkinson's disease (PD) have been available for some time, efficient and well-controlled drug delivery to the brain has proven to be challenging. The emergence of nanotechnology has created new opportunities not only for improving the pharmacokinetics of conventional therapies but also for developing novel treatment approaches and disease modifying therapies. Several exciting strategies including drug carrier nanoparticles targeting specific intracellular pathways and structural reconformation of tangled proteins as well as introducing reprogramming genes have already shown promise and are likely to deliver more tailored approaches to the treatment of PD in the future. This paper reviews the role of nanoparticles in PD including a discussion of both their composition and functional capacity as well as their potential to deliver better therapeutic agents.

Dendrimer- and polymeric nanoparticle-aptamer bioconjugates as nonviral delivery systems: a new approach in medicine

Aptamers are RNA or DNA oligonucleotides interacting to form unique 3D target conformations with high affinity and specificity, and are emerging as a powerful class of ligands for therapeutic applications. In addition, dendrimers are well-defined nano-sized symmetric polymeric molecules. In this review, we provide an analysis of the use of dendrimers modified with aptamers as nonviral vectors to specifically target tumor cells. Various anticancer agents have been encapsulated with dendrimers complexing with aptamers, including epirubicin, camptothecin, Bcl-xL short hairpin (sh)RNA, and 5-fluorouracil rhodamine-labeled dextran. Other types of polymeric nanoparticle (NP)-aptamer bioconjugates have also been developed and loaded with Pt(IV) derivatives, to target specific tumor cells.

Generation Dependent Effects and Entrance to Mitochondria of Hybrid Dendrimers on Normal and Cancer Neuronal Cells In Vitro

Dendrimers as drug carriers can be utilized for drugs and siRNA delivery in central nervous system (CNS) disorders, including various types of cancers, such as neuroblastomas and gliomas. They have also been considered as drugs per se, for example as anti-Alzheimer's disease (AD), anti-cancer, anti-prion or anti-inflammatory agents. Since the influence of carbosilane-viologen-phosphorus dendrimers (SMT1 and SMT2) on the basic cellular processes of nerve cells had not been investigated, we examined the impact of two generations of these hybrid macromolecules on two murine cell lines-cancer cell line N2a (mouse neuroblastoma) and normal immortalized cell line mHippoE-18 (embryonic mouse hippocampal cell line). We examined alterations in cellular responses including the activity of mitochondrial dehydrogenases, the generation of reactive oxygen species (ROS), changes in mitochondrial membrane potential, and morphological modifications and fractions of apoptotic and dead cells. Our results show that both dendrimers at low concentrations affected the cancer cell line more than the normal one. Also, generation-dependent effects were found: the highest generation induced greater cytotoxic effects and morphological modifications. The most promising is that the changes in mitochondrial membrane potential and transmission electron microscopy (TEM) images indicate that dendrimer SMT1 can reach mitochondria. Thus, SMT1 and SMT2 seem to have potential as nanocarriers to mitochondria or anti-cancer drugs per se in CNS disorders.

Dense hydroxyl polyethylene glycol dendrimer targets activated glia in multiple CNS disorders

Poor transport of neuropharmaceutics through central nervous system (CNS) barriers limits the development of effective treatments for CNS disorders. We present the facile synthesis of a novel neuroinflammation-targeting polyethylene glycol-based dendrimer (PEGOL-60) using an efficient click chemistry approach. PEGOL-60 reduces synthetic burden by achieving high hydroxyl surface density at low generation, which plays a key role in brain penetration and glia targeting of dendrimers in CNS disorders. Systemically administered PEGOL-60 crosses impaired CNS barriers and specifically targets activated microglia/macrophages at the injured site in diverse animal models for cerebral palsy, glioblastoma, and age-related macular degeneration, demonstrating its potential to overcome impaired blood-brain, blood-tumor-brain, and blood-retinal barriers and target key cells in the CNS. PEGOL-60 also exhibits powerful intrinsic anti-oxidant and anti-inflammatory effects in inflamed microglia in vitro. Therefore, PEGOL-60 is an effective vehicle to specifically deliver therapies to sites of CNS injury for enhanced therapeutic outcomes in a range of neuroinflammatory diseases.

Bench-to-bedside translation of dendrimers: Reality or utopia? A concise analysis

Nanomedicine, which is an application of nanotechnologies in healthcare is developed to improve the treatments and lives of patients suffering from a range of disorders and to increase the successes of drug candidates. Within the nanotechnology universe, the remarkable unique and tunable properties of dendrimers have made them promising tools for diverse biomedical applications such as drug delivery, gene therapy and diagnostic. Up-to-date, very few dendrimers has yet gained regulatory approval for systemic administration, why? In this critical review, we briefly focus on the list of desired basic dendrimer requirements for decision-making purpose by the scientists (go/no-go decision), in early development stages, to become clinical candidates, and to move towards Investigational New Drugs (IND) application submission. In addition, the successful translation between research and clinic should be performed by the implementation of a simple roadmap to jump the 'valley of death' successfully.

Treatment of neurodegenerative disorders through the blood-brain barrier using nanocarriers

Neurodegenerative diseases refer to disorders of the central nervous system (CNS) that are caused by neuronal degradations, dysfunctions, or death. Alzheimer's disease, Parkinson's disease, and Huntington's disease (APHD) are regarded as the three major neurodegenerative diseases. There is a vast body of literature on the causes and treatments of these neurodegenerative diseases. However, the main obstacle in developing an effective treatment strategy is the permeability of the treatment components at the blood-brain barrier (BBB). Several strategies have been developed to improve this obstruction. For example, nanomaterials facilitate drug delivery to the BBB due to their size. They have been used widely in nanomedicine and as nanoprobes for diagnosis purposes among others in neuroscience. Nanomaterials in different forms, such as nanoparticles, nanoemulsions, solid lipid nanoparticles (SLN), and liposomes, have been used to treat neurodegenerative diseases. This review will cover the basic concepts and applications of nanomaterials in the therapy of APHD.

Effect of mannose targeting of hydroxyl PAMAM dendrimers on cellular and organ biodistribution in a neonatal brain injury model

Neurotherapeutics for the treatment of central nervous system (CNS) disorders must overcome challenges relating to the blood-brain barrier (BBB), brain tissue penetration, and the targeting of specific cells. Neuroinflammation mediated by activated microglia is a major hallmark of several neurological disorders, making these cells a desirable therapeutic target. Building on the promise of hydroxyl-terminated generation four polyamidoamine (PAMAM) dendrimers (D4-OH) for penetrating the injured BBB and targeting activated glia, we explored if conjugation of targeting ligands would enhance and modify brain and organ uptake. Since mannose receptors [cluster of differentiation (CD) 206] are typically over-expressed on injured microglia, we conjugated mannose to the surface of multifunctional D4-OH using highly efficient, atom-economical, and orthogonal Cu(I)-catalyzed alkyne-azide cycloaddition (CuAAC) click chemistry and evaluated the effect of mannose conjugation on the specific cell uptake of targeted and non-targeted dendrimers both in vitro and in vivo. In vitro results indicate that the conjugation of mannose as a targeting ligand significantly changes the mechanism of dendrimer internalization, giving mannosylated dendrimer a preference for mannose receptor-mediated endocytosis as opposed to non-specific fluid phase endocytosis. We further investigated the brain uptake and biodistribution of targeted and non-targeted fluorescently labeled dendrimers in a maternal intrauterine inflammation-induced cerebral palsy (CP) rabbit model using quantification methods based on fluorescence spectroscopy and confocal microscopy. We found that the conjugation of mannose modified the distribution of D4-OH throughout the body in this neonatal rabbit CP model without lowering the amount of dendrimer delivered to injured glia in the brain, even though significantly higher glial uptake was not observed in this model. Mannose conjugation to the dendrimer modifies the dendrimer's interaction with cells, but does not minimize its inherent inflammation-targeting abilities.

Loading IR820 Using Multifunctional Dendrimers with Enhanced Stability and Specificity

Cyanine dyes are promising candidates in biomedical applications. Although various delivery systems have been developed to enhance their properties, their dendrimer-based delivery systems are seldom investigated. Herein, amine-terminated generation 5 poly(amidoamine) (G5.NH₂) dendrimers and new indocyanine green (IR820) dyes were chosen as models to study the loading ability of dendrimers for cyanine dynes. G5.NH₂ dendrimers were pre-modified with arginine-glycine-aspartic (RGD) peptides, poly(ethylene glycol) chains, and acetyl groups to be endowed with cancer cell specificity and biocompatibility. The formed Ac-PR dendrimers were used to load IR820, followed by thorough characterization. The loaded number of IR820 was estimated to be 6.7 per dendrimer. The stability of IR820 was improved through dendrimer loading, which was proved by their UV-vis spectra under different kinds of storage conditions. In addition, the formed Ac-PR dendrimers can retain the loaded IR820 effectively. Their cytocompatibility was desirable under the studied conditions. Their cellular uptake behaviors were demonstrated to be enhanced by RGD modification, showing concentration-, co-incubation time-, and αvβ₃ integrin receptor-dependent properties, displaying a cytoplasm-location. The findings from this work demonstrated the versatile loading and delivery capacity of dendrimers for near-infrared (NIR) dyes, providing fundamental data for the development of dendrimer/NIR dye systems for biomedical applications, especially for cancer theranostic applications.

Brain Delivery of Multifunctional Dendrimer Protein Bioconjugates

Neurological disorders are undoubtedly among the most alarming diseases humans might face. In treatment of neurological disorders, the blood-brain barrier (BBB) is a challenging obstacle preventing drug penetration into the brain. Advances in dendrimer chemistry for central nervous system (CNS) treatments are presented here. A poly(amido)amine (PAMAM) dendrimer bioconjugate with a streptavidin adapter for the attachment of dendrons or any biotinylated drug is constructed. In vitro studies on porcine or murine models and in vivo mouse studies are performed and reveal the permeation of dendronized streptavidin (DSA) into the CNS. The bioconjugate is taken up mainly by the caveolae pathway and transported across the BBB via transcytosis escaping from lysosomes. After transcytosis DSA are delivered to astrocytes and neurons. Furthermore, DSA offer high biocompatibility in vitro and in vivo. In summary, a new strategy for implementing therapeutic PAMAM function as well as drug delivery in neuropathology is presented here.

Highly Crystalline Multicolor Carbon Nanodots for Dual-Modal Imaging-Guided Photothermal Therapy of Glioma

Imaging-guided site-specific photothermal therapy (PTT) of glioma and other tumors in central nervous system presents a great challenge for the current nanomaterial design. Herein, an in situ solid-state transformation method was developed for the preparation of multicolor highly crystalline carbon nanodots (HCCDs). The synthesis yields 6-8 nm-sized HCCDs containing a highly crystalline carbon nanocore and a hydrophilic surface, which therefore simultaneously provide strong photoacoustic and photothermal performances as well as tunable fluorescence emission. In vitro and in vivo results demonstrate that the novel HCCDs have high water dispersity and good biocompatibility, but potent tumor cell killing upon near-infrared irradiation. As demonstrated in U87 glioma-bearing mice, HCCDs specifically accumulate in brain tumors and facilitate dual-modal imaging-guided PTT, with therapeutic antitumoral effects without any apparent damage to normal tissues.

Cyclotriphosphazene core-based dendrimers for biomedical applications: an update on recent advances

This review is focused on the recent use of cyclotriphosphazene-based dendrimers in biomedicine. Since its synthesis for the first time in 1834, cyclotriphosphazene has been an important compound of phosphorus chemistry as a scaffold, and a large number of cyclotriphosphazene derivatives have been synthesized and applied in various fields such as biology, catalysis, fluorescence, nanomaterials, etc. Today, one of the most important uses concerns its biomedical applications. In this review, the recent developments (since 2012) of cyclotriphosphazene for major pharmaceutical applications are highlighted and analyzed.

Dendrimers in combination with natural products and analogues as anti-cancer agents

For the first time, an overview of dendrimers in combination with natural products and analogues as anti-cancer agents is presented. This reflects the development of drug delivery systems, such as dendrimers, to tackle cancers. The most significant advantages of using dendrimers in nanomedicine are their high biocompatibility, good water solubility, and their entry - with or without encapsulated, complexed or conjugated drugs - through an endocytosis process. This strategy has accelerated over the years in order to develop nanosystems as nanocarriers, to decrease the intrinsic toxicity of anti-cancer agents, to decrease the drug side effects, to increase the efficacy of the treatment, and consequently to improve patient compliance.

Dendrimers in combination with natural products and analogues as anti-cancer agents

Overview of the use of dendrimers in combination with encapsulated and conjugated natural products and analogues as anti-cancer agents.

Dendrimers in combination with natural products and analogues as anti-cancer agents

Overview of the use of dendrimers in combination with encapsulated and conjugated natural products and analogues as anti-cancer agents.

Original Multivalent Gold(III) and Dual Gold(III)-Copper(II) Conjugated Phosphorus Dendrimers as Potent Antitumoral and Antimicrobial Agents

Original metallophosphorus dendrimers (generation 3, 48 terminal groups) have been prepared via the complexation of phosphorus dendrimers bearing imino-pyridino end groups with Au(III) or with both Au(III) and Cu(II). The complexation of the dendrimer with Au(III), leading to 1G3-[Au₄₈][AuCl₄]₄₈, strongly increased the antiproliferative activities against both KB and HL-60 tumoral cell lines, showing IC₅₀s in the low nanomolar range. It can be noticed also that this gold conjugated phosphorus dendrimer displayed low activity on the quiescent cell line EPC versus its potent antiproliferative activity against actively dividing cells. In order to evaluate the potential synergistic effect between Au(III) and Cu(II) and the influence of the number of Au(III) moieties on the surface of dendrimer against the proliferative activities, nine other original dendrimers with several surface modifications have been prepared. Whatever the number of Au(III) moieties introduced on the surface of dendrimers, all the dendrimers prepared displayed similar potency (nanomolar range) to 1G3-[Au₄₈][AuCl₄]₄₈ against KB and HL60. In marked contrast synergistic effects on the antimicrobial activity of some of these phosphorus dendrimers are observed when both Au(III) and Cu(II) are present on the dendritic structure.

Cationic Phosphorus Dendrimer Enhances Photodynamic Activity of Rose Bengal against Basal Cell Carcinoma Cell Lines

In the last couple of decades, photodynamic therapy emerged as a useful tool in the treatment of basal cell carcinoma. However, it still meets limitations due to unfavorable properties of photosensitizers such as poor solubility or lack of selectivity. Dendrimers, polymers widely studied in biomedical field, may play a role as photosensitizer carriers and improve the efficacy of photodynamic treatment. Here, we describe the evaluation of an electrostatic complex of cationic phosphorus dendrimer and rose bengal in such aspects as singlet oxygen production, cellular uptake, and phototoxicity against three basal cell carcinoma cell lines. Rose bengal-cationic dendrimer complex in molar ratio 5:1 was compared to free rose bengal. Obtained results showed that the singlet oxygen production in aqueous medium was significantly higher for the complex than for free rose bengal. The cellular uptake of the complex was 2-7-fold higher compared to a free photosensitizer. Importantly, rose bengal, rose bengal-dendrimer complex, and dendrimer itself showed no dark toxicity against all three cell lines. Moreover, we observed that phototoxicity of the complex was remarkably enhanced presumably due to high cellular uptake. On the basis of the obtained results, we conclude that rose bengal-cationic dendrimer complex has a potential in photodynamic treatment of basal cell carcinoma.