A review on dendrimer-based nanoconjugates and their intracellular trafficking in cancer photodynamic therapy.

Nanotechnology-based cancer treatment has received considerable attention, and these treatments generally use drug-loaded nanoparticles (NPs) to target and destroy cancer cells. Nanotechnology combined with photodynamic therapy (PDT) has demonstrated positive outcomes in cancer therapy. Combining nanotechnology and PDT is effective in targeting metastatic cancer cells. Nanotechnology can also increase the effectiveness of PDT by targeting cells at a molecular level. Dendrimer-based nanoconjugates (DBNs) are highly stable and biocompatible, making them suitable for drug delivery applications. Moreover, the hyperbranched structures in DBNs have the capacity to load hydrophobic compounds, such as photosensitizers (PSs) and chemotherapy drugs, and deliver them efficiently to tumour cells. This review primarily focuses on DBNs and their potential applications in cancer treatment. We discuss the chemical design, mechanism of action, and targeting efficiency of DBNs in tumour metastasis, intracellular trafficking in cancer treatment, and DBNs' biocompatibility, biodegradability and clearance properties. Overall, this study will provide the most recent insights into the application of DBNs and PDT in cancer therapy.

DBNs' intracellular journey in cancer-PDT refines targeted therapy, boosting efficacy.DBN in PDT for tumour metastasis: targeting and drug release mechanisms.DBNs' biocompatibility, biodegradability and clearance were explored thoroughly.

Systemically targeting monocytic myloid-derrived suppressor cells using dendrimers and their cell-level biodistribution kinetics.

The focus of nanoparticles in vivo trafficking has been mostly on their tissue-level biodistribution and clearance. Recent progress in the nanomedicine field suggests that the targeting of nanoparticles to immune cells can be used to modulate the immune response and enhance therapeutic delivery to the diseased tissue. In the presence of tumor lesions, monocytic-myeloid-derived suppressor cells (M-MDSCs) expand significantly in the bone marrow, egress into peripheral blood, and traffic to the solid tumor, where they help maintain an immuno-suppressive tumor microenvironment. In this study, we investigated the interaction between PAMAM dendrimers and M-MDSCs in two murine models of glioblastoma, by examining the cell-level biodistribution kinetics of the systemically injected dendrimers. We found that M-MDSCs in the tumor and lymphoid organs can efficiently endocytose hydroxyl dendrimers. Interestingly, the trafficking of M-MDSCs from the bone marrow to the tumor contributed to the deposition of hydroxyl dendrimers in the tumor. M-MDSCs showed different capacities of endocytosing dendrimers of different functionalities in vivo. This differential uptake was mediated by the unique serum proteins associated with each dendrimer surface functionality. The results of this study set up the framework for developing dendrimer-based immunotherapy to target M-MDSCs for cancer treatment.

Dendrimers as drug delivery systems for oncotherapy: Current status of promising applications.

Cancer affects millions of people worldwide, causing death and serious health problems. Despite significant investment in the development of new anticancer compounds, there are still several limitations that can still be found. Many compounds exhibit high levels of toxicity and low bioavailability. Therefore, it is urgent to design safer, more effective, and particularly more selective compounds for oncological treatment. Dendrimers are polymeric structures that have been shown to be potential drug nanocarriers to overcome physicochemical, pharmacokinetic, and indirect pharmacodynamic issues. Due to their versatility, they can be used in the design of nanovaccines, lipophilic complexes, amphiphilic complexes, smart nanocomplexes, and others. This work targets the use of dendrimers in oncological treatment and their importance and effectiveness as drug delivery systems for the development of new therapies. For this review, only publications from the last two years are considered in this review.

ROS-Responsive Ferrocenyl Amphiphilic PAMAM Dendrimers for On-Demand Delivery of siRNA Therapeutics to Cancer Cells.

Small interfering RNA (siRNA) therapeutics, characterized by high specificity, potency, and durability, hold great promise in the treatment of cancer and other diseases. However, the clinic implementation of siRNA therapeutics critically depends on the safe and on-demand delivery of siRNA to the target cells. Here, we reported a family of ferrocenyl amphiphilic dendrimers (Fc-AmDs) for on-demand delivery of siRNA in response to the high ROS content in cancer cells. These dendrimers bear ROS-sensitive ferrocene moieties in the hydrophobic components and positively chargeable poly(amidoamine) dendrons as the hydrophilic entities, possessing favorable safety profiles and ROS responsive properties. One of these ferrocenyl amphiphilic dendrimers, Fc-C8-AmD 8A, outperforms in siRNA delivery, benefiting from its optimal balance of hydrophobicity and hydrophilicity. Its ROS feature facilitates specific and efficient disassembly of its complex with siRNA in ROS-rich cancer cells for effective siRNA delivery and gene silencing. Moreover, Fc-C8-AmD 8A also integrates the features and beneficial properties of both lipid and dendrimer vectors. Therefore, it represents a novel on-demand delivery system for cancer cell-specific siRNA delivery. This work opens new perspectives for designing self-assembly nanosystems for on-demand drug delivery.

Hybrid Dendrimer Network based on Silsesquioxane and glycidyl methacrylate for Enhanced Adsorption of Iodine and Dyes in Environmental Remediation.

A novel hybrid network was synthesized in two steps: the first step involved the attachment of glycidyl methacrylate (GMA) to octa(aminophenyl) silsesquioxane (OAPS) through a ring-opening reaction, forming a hybrid dendrimer structure, and the second step involved the cross-linking of hybrid dendrimer using an azobisisobutyronitrile initiator to create the final hybrid network of OAPS-GMA. The synthesized hybrid material was comprehensively characterized using fourier transform infrared Spectroscopy (FTIR), nuclear magnetic resonance ((1H, 13C, and 29Si NMR) spectroscopy, thermogravimetric Analysis (TGA), and scanning electron microscopy (SEM).  The BET surface area was found to be 25.44 m²/g, and significant 2.341 cm³/g of total pore volume was observed. The TGA analysis shows that the material is highly stable up to 450 oC. The synthesized network demonstrated remarkable adsorption capacities for iodine and dyes. It exhibited an iodine adsorption capacity of 3.4g/g from vapors and 874mg/g from solution. Additionally, it showed significant adsorption capacities for Rhodamine B and Congo red, with values of 762mg/g and 517mg/g, respectively. This study not only provides a novel method for preparing GMA-functionalized silsesquioxane-based porous hybrid polymers but also contributes to advancing solutions for environmental pollution issues.

Dendrimer Platforms for Targeted Doxorubicin Delivery-Physicochemical Properties in Context of Biological Responses.

The unique structure of G4.0 PAMAM dendrimers allows a drug to be enclosed in internal spaces or immobilized on the surface. In the conducted research, the conditions for the formation of the active G4.0 PAMAM complex with doxorubicin hydrochloride (DOX) were optimized. The physicochemical properties of the system were monitored using dynamic light scattering (DLS), circular dichroism (CD), and fluorescence spectroscopy. The Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D) method was chosen to determine the preferential conditions for the complex formation. The highest binding efficiency of the drug to the cationic dendrimer was observed under basic conditions when the DOX molecule was deprotonated. The decrease in the zeta potential of the complex confirms that DOX immobilizes through electrostatic interaction with the carrier's surface amine groups. The binding constants were determined from the fluorescence quenching of the DOX molecule in the presence of G4.0 PAMAM. The two-fold way of binding doxorubicin in the structure of dendrimers was visible in the Isothermal calorimetry (ITC) isotherm. Fluorescence spectra and release curves identified the reversible binding of DOX to the nanocarrier. Among the selected cancer cells, the most promising anticancer activity of the G4.0-DOX complex was observed in A375 malignant melanoma cells. Moreover, the preferred intracellular location of the complexes concerning the free drug was found, which is essential from a therapeutic point of view.

Fe3O4@SiO2@NTMPThio-Cu: a sustainable and eco-friendly approach for the synthesis of heterocycle derivatives using a novel dendrimer template nanocatalyst.

In this research, Fe3O4@SiO2@NTMPThio-Cu was introduced as a novel and green heterogeneous nanocatalyst with a dendrimer template that is environmentally friendly and reusable based on Fe3O4@SiO2. In this way, magnetic silica nanoparticles were first modified with cyanuric chloride, followed by melamine and thiosemicarbazide, and ultimately, it's decorated with the cost-effective metal copper. The synthesized nanocatalyst was characterized by various analyses such as FT-IR, XRD, SEM, TGA, and EDX. The efficiency of Fe3O4@SiO2@NTMPThio-Cu was measured in one-pot synthesis of xanthene and spirooxindole-pyran derivatives under mild solvent-free conditions. High efficiency, excellent yield of products, mild reaction conditions, simple operation, no use of toxic organic solvents, and reusability of this catalyst increase the attractiveness of this technique for large-scale environmentally friendly operations.

Fluorinated PAMAM-Arginine Carrier Prodrugs for pH-Sensitive Sustained Ibuprofen Delivery.

OBJECTIVE: The development of an efficient, multifunctional drug delivery system overcoming different obstacles generally associated with drug formulations, including the poor accumulation of the active principle in the target site and its sustained release for prolonged time. METHODS: Our study proposes the development of a fluorinated poly(amidoamine) (PAMAM) carrier prodrug combining drug release boosted in alkaline environments with a possible implementation in 19F MRI applications. In particular, we functionalized the terminal primary amines of PAMAM G2 and G4 through an ad hoc designed fluorinated ibuprofen-arginine Michael acceptor to obtain multifunctional ibuprofen-PAMAM-Arg conjugates. RESULTS: These carriers demonstrated pH-dependent and sustained ibuprofen release for more than 5 days. This advantage was observed in both weak alkaline and physiological buffer solutions, allowing to overcome the limits associated to the burst release from similar fluorinated Arg-PAMAM dendrimers with ibuprofen physically encapsulated. CONCLUSION: These findings, coupled to the high biocompatibility of the system, suggest a potential synergistic biomedical application of our conjugates, serving as vehicles for drug delivery and as 19F magnetic resonance imaging contrast agents.

Unilateral Administration of Surface-Modified G1 and G4 PAMAM Dendrimers in Healthy Mice to Assess Dendrimer Migration in the Brain.

Polyamidoamine (PAMAM) dendrimers are nanoparticles that have a wide scope in the field of biomedicine. Previous evidence shows that the generation 4 (G4) dendrimers with a 100% amine surface (G4-NH2) are highly toxic to cells in vitro and in vivo due to their positively charged amine groups. To reduce the toxicity, we modified the surface of the dendrimers to have more neutral functional groups, with 10% of the surface covered with -NH2 and 90% of the surface covered with hydroxyl groups (-OH; G4-90/10). Our previous in vitro data show that these modified dendrimers are taken up by cells, neurons, and different types of stem cells in vitro and neurons and glial cells in vivo. The toxicity assay shows that these modified dendrimers are less toxic compared with G4-NH2 dendrimers. Moreover, prolonged dendrimer exposure (G1-90/10 and G4-90/10), up to 3 weeks following unilateral intrastriatal injections into the striatum of mice, showed that dendrimers have the tendency to migrate within the brain via corpus callosum at different rates depending on their size. We also found that there is a difference in migration between the G1 and G4 dendrimers based on their size differences. The G4 dendrimers migrate in the anterior and posterior directions as well as more laterally from the site of injection in the striatum compared to the G1 dendrimers. Moreover, the G4 dendrimers have unique projections from the site of injection to the cortical areas.

Analytical Model to Deduce the Conformational and Dynamical Behavior in Dendrimers: A Review.

This review utilizes an optimized Rouse-Zimm discrete hydrodynamic model and the preaveraged Oseen tensor, which accurately consider hydrodynamic interactions to study model dendrimers. We report the analytical theories that have been previously developed for the creation of generalized analytical models for dendrimers. These generalized theories were used to assess the conformational and dynamical behavior of the dendrimers. By including stiffness in the bonds, the neglect of excluded volume interactions may be somewhat offset. This is true at least in the case of short spacers. While the topological limitations on the directions and orientations of the individual bond vectors in dendrimers implement semiflexibility, the intensity of these contacts was determined by the potential geometric orientations of the bonds, and later on the excluded volume interactions in dendrimers, which were described in terms of the effective co-volume between nearest non-bonded monomers and modeled using the delta function pseudopotential. With the aid of the models developed, the authors condensed various conformational and dynamic properties of dendrimers that depend on their degree of semiflexibility and the strength of the excluded volume. These analyses came to the conclusion that the flexible dendrimer in one limit and the earlier described freely rotating model of dendrimers in the other constitute a highly generalized way of capturing a wide range of conformations in the developed mathematical model in dendrimers.

Ion-Selective Transport Promotion Enabled by Angstrom-Scale Nanochannels in Dendrimer-Assembled Polyamide Nanofilm for Efficient Electrodialysis.

The ion permeability and selectivity of membranes are crucial in nanofluidic behavior, impacting industries ranging from traditional to advanced manufacturing. Herein, we demonstrate the engineering of ion-conductive membranes featuring angstrom-scale ion-transport channels by introducing ionic polyamidoamine (PAMAM) dendrimers for ion separation. The exterior quaternary ammonium-rich structure contributes to significant electrostatic charge exclusion due to enhanced local charge density; the interior protoplasmic channels of PAMAM dendrimer are assembled to provide additional degrees of free volume. This facilitates the monovalent ion transfer while maintaining continuity and efficient ion screening. The dendrimer-assembled hybrid membrane achieves high monovalent ion permeance of 2.81 mol m-2 h-1 (K+), reaching excellent mono/multivalent selectivity up to 20.1 (K+/Mg2+) and surpassing the permselectivities of state-of-the-art membranes. Both experimental results and simulating calculations suggest that the impressive ion selectivity arises from the significant disparity in transport energy barrier between mono/multivalent ions, induced by the "exterior-interior" synergistic effects of bifunctional membrane channels.

Journey from lab to clinic: Design, preclinical, and clinical development of systemic, targeted dendrimer-N-acetylcysteine (D-NAC) nanomedicines.

Drug discovery is challenging task with numerous obstacles in translating drug candidates into clinical products. Dendrimers are highly adaptable nanostructured polymers with significant potential to improve the chances of clinical success for drugs. Yet, dendrimer-based drug products are still in their infancy. However, Hydroxyl polyamidoamine (PAMAM) dendrimers showed significant promise in drug discovery efforts, owning their remarkable potential to selectively target and deliver drugs specifically to activated microglia and astrocytes at the site of brain injury in several preclinical models. After a decade's worth of academic research and pre-clinical efforts, the hydroxyl PAMAM dendrimer-N-acetyl cysteine conjugate (OP-101) nanomedicine has made a significant advancement in the field of nanomedicine and targeted delivery. The OP-101 conjugate, primarily developed and validated in academic labs, has now entered clinical trials as a potential treatment for hyperinflammation in hospitalized adults with severe COVID-19 through Ashvattha Therapeutics. This chapter, we delve into the journey of the hydroxyl PAMAM dendrimer-N-acetylcysteine (NAC) OP-101 formulation from the laboratory to the clinic. It will specifically focus on the design, synthesis, preclinical, and clinical development of OP-101, highlighting the potential it holds for the future of medicine and the positive Phase 2a results for treating severe COVID-19.

Lysine and citric acid based pegylated polymeric dendritic nano drug delivery carrier and their bioactivity evaluation.

The main objective of this work is to synthesize multifunctional nanodendritic structural molecules that can effectively encapsulate hydrophilic as well as hydrophobic therapeutic agents. Four different types of fourth-generation lysine-citric acid based dendrimer have been synthesized in this work: PE-MC-Lys-CA-PEG, TMP-MC-Lys-CA-PEG, PE-MS-Lys-CA-PEG, and TMP-MS-Lys-CA-PEG. The antibacterial drug cefotaxime (CFTX) was further conjugated to these dendrimers. The dendrimer and drug-dendrimer conjugate structures were characterized with the help of FTIR,1H-NMR, and 13C-NMR spectroscopy. Zeta sizer, AFM, and HR-TEM techniques were used to investigate the particle size, surface topography, and structural characteristics of drug-dendrimer conjugates. In vitro drug release was then investigated using dialysis method. Various kinetic drug release models were examined to evaluate the type of kinetic drug release mechanism of the formulations. Cytotoxicity study revealed that the dendrimers encapsulated with CFTX exhibited 2-3% toxicity against healthy epithelial cells, indicating their safe use. Plain dendrimers show 10-15% hemolytic toxicity against red blood cells (RBC), and the toxicity was reduced to 2-3% when CFTX was conjugated to the same dendrimers. The 3rd and 4th generation synthesized drug-dendrimer conjugates exhibit a significantly effective zone of inhibition (ZOI) against both Gram-positive and Gram-negative bacteria. For Gram-positive bacteria, the lower concentration of 0.1 mg/mL showed more than 98% inhibition of drug-dendrimer conjugate samples against B. subtilis and more than 50% inhibition against S. aureus using 0.2 mg/mL, respectively. Moreover, samples with concentrations of 0.5 and 1.0 mg/mL exhibited more than 50% inhibition against S. typhimurium and E. coli, respectively.

Multimodal, PSMA-Targeted, PAMAM Dendrimer-Drug Conjugates for Treatment of Prostate Cancer: Preclinical Evaluation.

Introduction: Prostate cancer (PC) is the second most common cancer and the fifth most frequent cause of cancer death among men. Prostate-specific membrane antigen (PSMA) expression is associated with aggressive PC, with expression in over 90% of patients with metastatic disease. Those characteristics have led to its use for PC diagnosis and therapies with radiopharmaceuticals, antibody-drug conjugates, and nanoparticles. Despite these advancements, none of the current therapeutics are curative and show some degree of toxicity. Here we present the synthesis and preclinical evaluation of a multimodal, PSMA-targeted dendrimer-drug conjugate (PT-DDC), synthesized using poly(amidoamine) (PAMAM) dendrimers. PT-DDC was designed to enable imaging of drug delivery, providing valuable insights to understand and enhance therapeutic response. Methods: The PT-DDC was synthesized through consecutive conjugation of generation-4 PAMAM dendrimers with maytansinoid-1 (DM1) a highly potent antimitotic agent, Cy5 infrared dye for optical imaging, 2,2',2"-(1,4,7-triazacyclononane-1,4,7-triyl)triacetic acid (NOTA) chelator for radiolabeling with copper-64 and positron emission tomography tomography/computed tomography (PET/CT), lysine-urea-glutamate (KEU) PSMA-targeting moiety and the remaining terminal primary amines were capped with butane-1,2-diol. Non-targeted control dendrimer-drug conjugate (Ctrl-DDC) was formulated without conjugation of KEU. PT-DDC and Ctrl-DDC were characterized using high-performance liquid chromatography, matrix assisted laser desorption ionization mass spectrometry and dynamic light scattering. In vitro and in vivo evaluation of PT-DDC and Ctrl-DDC were carried out in isogenic human prostate cancer PSMA+ PC3 PIP and PSMA- PC3 flu cell lines, and in mice bearing the corresponding xenografts. Results: PT-DDC was stable in 1×PBS and human blood plasma and required glutathione for DM1 release. Optical, PET/CT and biodistribution studies confirmed the in vivo PSMA-specificity of PT-DDC. PT-DDC demonstrated dose-dependent accumulation and cytotoxicity in PSMA+ PC3 PIP cells, and also showed growth inhibition of the corresponding tumors. PT-DDC did not accumulate in PSMA- PC3 flu tumors and did not inhibit their growth. Ctrl-DDC did not show PSMA specificity. Conclusion: In this study, we synthesized a multimodal theranostic agent capable of delivering DM1 and a radionuclide to PSMA+ tumors. This approach holds promise for enhancing image-guided treatment of aggressive, metastatic subtypes of prostate cancer.

Sweet corn phytoglycogen dendrimers as a lyoprotectant for dry-state protein storage.

Protein biotherapeutics typically require expensive cold-chain storage to maintain their fold and function. Packaging proteins in the dry state via lyophilization can reduce these cold-chain requirements. However, formulating proteins for lyophilization often requires extensive optimization of excipients that both maintain the protein folded state during freezing and drying (i.e., "cryoprotection" and "lyoprotection"), and form a cake to carry the dehydrated protein. Here we show that sweet corn phytoglycogens, which are glucose dendrimers, can act as both a protein lyoprotectant and a cake-forming agent. Phytoglycogen (PG) dendrimers from 16 different maize sources (PG1-16) were extracted via ethanol precipitation. PG size was generally consistent at ~70-100 nm for all variants, whereas the colloidal stability in water, protein contaminant level, and maximum density of cytocompatibility varied for PG1-16. 10 mg/mL PG1, 2, 9, 13, 15, and 16 maintained the activity of various proteins, including green fluorescent protein, lysozyme, ß-galactosidase, and horseradish peroxidase, over a broad range of concentrations, through multiple rounds of lyophilization. PG13 was identified as the lead excipient candidate as it demonstrated narrow dispersity, colloidal stability in phosphate-buffered saline, low protein contaminants, and cytocompatibility up to 10 mg/mL in NIH3T3 cell cultures. All dry protein-PG13 mixtures had a cake-like appearance and all frozen protein-PG13 mixtures had a Tg' of ~ -26°C. The lyoprotection and cake-forming properties of PG13 were density-dependent, requiring a minimum density of 5 mg/mL for maximum activity. Collectively these data establish PG dendrimers as a new class of excipient to formulate proteins in the dry state.

Discovery of 2-deoxy glucose surfaced mixed layer dendrimer: a smart neuron targeted systemic drug delivery system for brain diseases.

The availability of non-invasive drug delivery systems capable of efficiently transporting bioactive molecules across the blood-brain barrier to specific cells at the injury site in the brain is currently limited. Delivering drugs to neurons presents an even more formidable challenge due to their lower numbers and less phagocytic nature compared to other brain cells. Additionally, the diverse types of neurons, each performing specific functions, necessitate precise targeting of those implicated in the disease. Moreover, the complex synthetic design of drug delivery systems often hinders their clinical translation. The production of nanomaterials at an industrial scale with high reproducibility and purity is particularly challenging. However, overcoming this challenge is possible by designing nanomaterials through a straightforward, facile, and easily reproducible synthetic process. Methods: In this study, we have developed a third-generation 2-deoxy-glucose functionalized mixed layer dendrimer (2DG-D) utilizing biocompatible and cost-effective materials via a highly facile convergent approach, employing copper-catalyzed click chemistry. We further evaluated the systemic neuronal targeting and biodistribution of 2DG-D, and brain delivery of a neuroprotective agent pioglitazone (Pio) in a pediatric traumatic brain injury (TBI) model. Results: The 2DG-D exhibits favorable characteristics including high water solubility, biocompatibility, biological stability, nanoscale size, and a substantial number of end groups suitable for drug conjugation. Upon systemic administration in a pediatric mouse model of traumatic brain injury (TBI), the 2DG-D localizes in neurons at the injured brain site, clears rapidly from off-target locations, effectively delivers Pio, ameliorates neuroinflammation, and improves behavioral outcomes. Conclusions: The promising in vivo results coupled with a convenient synthetic approach for the construction of 2DG-D makes it a potential nanoplatform for addressing brain diseases.

Targeted Modulation of Redox and Immune Homeostasis in Acute Lung Injury Using a Thioether-Functionalized Dendrimer.

Acute lung injury (ALI) is the pathophysiological precursor of acute respiratory distress syndrome. It is characterized by increased oxidative stress and exaggerated inflammatory response that disrupts redox reactions and immune homeostasis in the lungs, thereby posing significant clinical challenges. In this study, an internally functionalized thioether-enriched dendrimer Sr-G4-PEG is developed, to scavenge both proinflammatory cytokines and reactive oxygen species (ROS) and restore homeostasis during ALI treatment. The dendrimers are synthesized using an efficient and orthogonal thiol-ene "click" chemistry approach that involves incorporating thioether moieties within the dendritic architectures to neutralize the ROS. The ROS scavenging of Sr-G4-PEG manifests in its capacity to sequester proinflammatory cytokines. The synergistic effects of scavenging ROS and sequestering inflammatory cytokines by Sr-G4-PEG contribute to redox remodeling and immune homeostasis, along with the modulation of the NLRP3-pyroptosis pathway. Treatment with Sr-G4-PEG enhances the therapeutic efficacy of ALIs by alleviating alveolar bleeding, reducing inflammatory cell infiltration, and suppressing the release of inflammatory cytokines. These results suggest that Sr-G4-PEG is a potent nanotechnological candidate for remodeling redox and immune homeostasis in the treatment of ALIs, demonstrating the great potential of dendrimer-based nanomedicine for the treatment of respiratory pathologies.

Self-assembling dendrimer nanosystems for specific fluorine magnetic resonance imaging and effective theranostic treatment of tumors.

Fluorine magnetic resonance imaging (19F-MRI) is particularly promising for biomedical applications owing to the absence of fluorine in most biological systems. However, its use has been limited by the lack of safe and water-soluble imaging agents with high fluorine contents and suitable relaxation properties. We report innovative 19F-MRI agents based on supramolecular dendrimers self-assembled by an amphiphilic dendrimer composed of a hydrophobic alkyl chain and a hydrophilic dendron. Specifically, this amphiphilic dendrimer bears multiple negatively charged terminals with high fluorine content, which effectively prevented intra- and intermolecular aggregation of fluorinated entities via electrostatic repulsion. This permitted high fluorine nuclei mobility alongside good water solubility with favorable relaxation properties for use in 19F-MRI. Importantly, the self-assembling 19F-MRI agent was able to encapsulate the near-infrared fluorescence (NIRF) agent DiR and the anticancer drug paclitaxel for multimodal 19F-MRI and NIRF imaging of and theranostics for pancreatic cancer, a deadly disease for which there remains no adequate early detection method or efficacious treatment. The 19F-MRI and multimodal 19F-MRI and NIRF imaging studies on human pancreatic cancer xenografts in mice confirmed the capability of both imaging modalities to specifically image the tumors and demonstrated the efficacy of the theranostic agent in cancer treatment, largely outperforming the clinical anticancer drug paclitaxel. Consequently, these dendrimer nanosystems constitute promising 19F-MRI agents for effective cancer management. This study offers a broad avenue to the construction of 19F-MRI agents and theranostics, exploiting self-assembling supramolecular dendrimer chemistry.

Structural Optimization of Carboxy-Terminal Phenylalanine-Modified Dendrimers for T-Cell Association and Model Drug Loading.

Dendrimers are potent nanocarriers in drug delivery systems because their structure can be precisely controlled. We previously reported that polyamidoamine (PAMAM) dendrimers that were modified with 1,2-cyclohexanedicarboxylic acid (CHex) and phenylalanine (Phe), PAMAM-CHex-Phe, exhibited an effective association with various immune cells, including T-cells. In this study, we synthesized various carboxy-terminal Phe-modified dendrimers with different linkers using phthalic acid and linear dicarboxylic acids to determine the association of these dendrimers with Jurkat cells, a T-cell model. PAMAM-n-hexyl-Phe demonstrated the highest association with Jurkat T-cells. In addition, dendri-graft polylysine (DGL) with CHex and Phe, DGL-CHex-Phe, was synthesized, and its association with Jurkat cells was investigated. The association of DGL-CHex-Phe with T-cells was higher than that of PAMAM-CHex-Phe. However, it was insoluble in water and thus it is unsuitable as a drug carrier. Model drugs, such as protoporphyrin IX and paclitaxel, were loaded onto these dendrimers, and the most model drug molecules could be loaded into PAMAM-CHex-Phe. PTX-loaded PAMAM-CHex-Phe exhibited cytotoxicity against Jurkat cells at a similar level to free PTX. These results suggest that PAMAM-CHex-Phe exhibited both efficient T-cell association and drug loading properties.

Cationic Glucan Dendrimer Gel-Mediated Local Delivery of Anti-OC-STAMP-siRNA for Treatment of Pathogenic Bone Resorption.

Osteoclast stimulatory transmembrane protein (OC-STAMP) plays a pivotal role in the promotion of cell fusion during osteoclast differentiation (osteoclastogenesis) in the context of pathogenic bone resorption. Thus, it is plausible that the suppression of OC-STAMP through a bioengineering approach could lead to the development of an effective treatment for inflammatory bone resorptive diseases with minimum side effects. Here, we synthesized two types of spermine-bearing (Spe) cationic glucan dendrimer (GD) gels (with or without C12) as carriers of short interfering RNA (siRNA) to silence OC-STAMP. The results showed that amphiphilic C12-GD-Spe gel was more efficient in silencing OC-STAMP than GD-Spe gel and that the mixture of anti-OC-STAMP siRNA/C12-GD-Spe significantly downregulated RANKL-induced osteoclastogenesis. Also, local injection of anti-OC-STAMP-siRNA/C12-GD-Spe could attenuate bone resorption induced in a mouse model of periodontitis. These results suggest that OC-STAMP is a promising target for the development of a novel bone regenerative therapy and that C12-GD-Spe gel provides a new nanocarrier platform of gene therapies for osteolytic disease.