Investigating the Differential Circulating microRNA Expression in Adolescent Females with Severe Idiopathic Scoliosis: A Proof-of-Concept Observational Clinical Study.

Adolescent Idiopathic Scoliosis (AIS) is the most common form of three-dimensional spinal disorder in adolescents between the ages of 10 and 18 years of age, most commonly diagnosed in young women when severe disease occurs. Patients with AIS are characterized by abnormal skeletal growth and reduced bone mineral density. The etiology of AIS is thought to be multifactorial, involving both environmental and genetic factors, but to date, it is still unknown. Therefore, it is crucial to further investigate the molecular pathogenesis of AIS and to identify biomarkers useful for predicting curve progression. In this perspective, the relative abundance of a panel of microRNAs (miRNAs) was analyzed in the plasma of 20 AIS patients and 10 healthy controls (HC). The data revealed a significant group of circulating miRNAs dysregulated in AIS patients compared to HC. Further bioinformatic analyses evidenced a more restricted expression of some miRNAs exclusively in severe AIS females. These include some members of the miR-30 family, which are considered promising regulators for treating bone diseases. We demonstrated circulating extracellular vesicles (EVs) from severe AIS females contained miR-30 family members and decreased the osteogenic differentiation of mesenchymal stem cells. Proteomic analysis of EVs highlighted the expression of proteins associated with orthopedic disease. This study provides preliminary evidence of a miRNAs signature potentially associated with severe female AIS and suggests the corresponding vesicular component may affect cellular mechanisms crucial in AIS, opening the scenario for in-depth studies on prognostic differences related to gender and grade.

Timing Expression of miR203a-3p during OA Disease: Preliminary In Vitro Evidence.

Osteoarthritis (OA) is a degenerative bone disease that involves the microenvironment and macroenvironment of joints. Progressive joint tissue degradation and loss of extracellular matrix elements, together with different grades of inflammation, are important hallmarks of OA disease. Therefore, the identification of specific biomarkers to distinguish the stages of disease becomes a primary necessity in clinical practice. To this aim, we investigated the role of miR203a-3p in OA progression starting from the evidence obtained by osteoblasts isolated from joint tissues of OA patients classified according to different Kellgren and Lawrence (KL) grading (KL ≤ 3 and KL > 3) and hMSCs treated with IL-1ß. Through qRT-PCR analysis, it was found that osteoblasts (OBs) derived from the KL ≤ 3 group expressed high levels of miR203a-3p and low levels of ILs compared with those of OBs derived from the KL > 3 group. The stimulation with IL-1ß improved the expression of miR203a-3p and the methylation of the IL-6 promoter gene, favoring an increase in relative protein expression. The gain and loss of function studies showed that the transfection with miR203a-3p inhibitor alone or in co-treatments with IL-1ß was able to induce the expression of CX-43 and SP-1 and to modulate the expression of TAZ, in OBs derived from OA patients with KL ≤ 3 compared with KL > 3. These events, confirmed also by qRT-PCR analysis, Western blot, and ELISA assay performed on hMSCs stimulated with IL-1ß, supported our hypothesis about the role of miR203a-3p in OA progression. The results suggested that during the early stage, miR203a-3p displayed a protective role reducing the inflammatory effects on CX-43, SP-1, and TAZ. During the OA progression the downregulation of miR203a-3p and consequently the upregulation of CX-43/SP-1 and TAZ expression improved the inflammatory response and the reorganization of the cytoskeleton. This role led to the subsequent stage of the disease, where the aberrant inflammatory and fibrotic responses determined the destruction of the joint.

Magnesium Alloys in Orthopedics: A Systematic Review on Approaches, Coatings and Strategies to Improve Biocompatibility, Osteogenic Properties and Osteointegration Capabilities.

There is increasing interest in using magnesium (Mg) alloy orthopedic devices because of their mechanical properties and bioresorption potential. Concerns related to their rapid degradation have been issued by developing biodegradable micro- and nanostructured coatings to enhance corrosion resistance and limit the release of hydrogen during degradation. This systematic review based on four databases (PubMed®, Embase, Web of Science™ and ScienceDirect®) aims to present state-of-the-art strategies, approaches and materials used to address the critical factors currently impeding the utilization of Mg alloy devices. Forty studies were selected according to PRISMA guidelines and specific PECO criteria. Risk of bias assessment was conducted using OHAT and SYRCLE tools for in vitro and in vivo studies, respectively. Despite limitations associated with identified bias, the review provides a comprehensive analysis of preclinical in vitro and in vivo studies focused on manufacturing and application of Mg alloys in orthopedics. This attests to the continuous evolution of research related to Mg alloy modifications (e.g., AZ91, LAE442 and WE43) and micro- and nanocoatings (e.g., MAO and MgF2), which are developed to improve the degradation rate required for long-term mechanical resistance to loading and excellent osseointegration with bone tissue, thereby promoting functional bone regeneration. Further research is required to deeply verify the safety and efficacy of Mg alloys.

The Binomial "Inflammation-Epigenetics" in Breast Cancer Progression and Bone Metastasis: IL-1ß Actions Are Influenced by TET Inhibitor in MCF-7 Cell Line.

The existence of a tight relationship between inflammation and epigenetics that in primary breast tumor cells can lead to tumor progression and the formation of bone metastases was investigated. It was highlighted how the induction of tumor progression and bone metastasis by Interleukin-1 beta, in a non-metastatic breast cancer cell line, MCF-7, was dependent on the de-methylating actions of ten-eleven translocation proteins (TETs). In fact, the inhibition of their activity by the Bobcat339 molecule, an inhibitor of TET enzymes, determined on the one hand, the modulation of the epithelial-mesenchymal transition process, and on the other hand, the reduction in the expression of markers of bone metastasis, indicating that the epigenetic action of TETs is a prerequisite for IL-1ß-dependent tumor progression and bone metastasis formation.

Potential Anti-Metastatic Role of the Novel miR-CT3 in Tumor Angiogenesis and Osteosarcoma Invasion.

Osteosarcoma (OS) is the most common primary bone tumor mainly occurring in young adults and derived from primitive bone-forming mesenchyme. OS develops in an intricate tumor microenvironment (TME) where cellular function regulated by microRNAs (miRNAs) may affect communication between OS cells and the surrounding TME. Therefore, miRNAs are considered potential therapeutic targets in cancer and one of the goals of research is to accurately define a specific signature of a miRNAs, which could reflect the phenotype of a particular tumor, such as OS. Through NGS approach, we previously found a specific molecular profile of miRNAs in OS and discovered 8 novel miRNAs. Among these, we deepen our knowledge on the fifth candidate renamed now miR-CT3. MiR-CT3 expression was low in OS cells when compared with human primary osteoblasts and healthy bone. Through TargetScan, VEGF-A was predicted as a potential biological target of miR-CT3 and luciferase assay confirmed it. We showed that enforced expression of miR-CT3 in two OS cell lines, SAOS-2 and MG-63, reduced expression of VEGF-A mRNA and protein, inhibiting tumor angiogenesis. Enforced expression of miR-CT3 also reduced OS cell migration and invasion as confirmed by soft agar colony formation assay. Interestingly, we found that miR-CT3 behaves inducing the activation of p38 MAP kinase pathway and modulating the epithelial-mesenchymal transition (EMT) proteins, in particular reducing Vimentin expression. Overall, our study highlights the novel role of miR-CT3 in regulating tumor angiogenesis and progression in OS cells, linking also to the modulation of EMT proteins.

How miR-31-5p and miR-33a-5p Regulates SP1/CX43 Expression in Osteoarthritis Disease: Preliminary Insights.

Osteoarthritis (OA) is a degenerative bone disease that involved micro and macro-environment of joints. To date, there are no radical curative treatments for OA and novel therapies are mandatory. Recent evidence suggests the role of miRNAs in OA progression. In our previous studies, we demonstrated the role of miR-31-5p and miR-33a families in different bone regeneration signaling. Here, we investigated the role of miR-31-5p and miR-33a-5p in OA progression. A different expression of miR-31-5p and miR-33a-5p into osteoblasts and chondrocytes isolated from joint tissues of OA patients classified in based on different Kellgren and Lawrence (KL) grading was highlighted; and through a bioinformatic approach the common miRNAs target Specificity proteins (Sp1) were identified. Sp1 regulates the expression of gap junction protein Connexin43 (Cx43), which in OA drives the modification of i) osteoblasts and chondrocytes genes expression, ii) joint inflammation cytokines releases and iii) cell functions. Concerning this, thanks to gain and loss of function studies, the possible role of Sp1 as a modulator of CX43 expression through miR-31-5p and miR-33a-5p action was also evaluated. Finally, we hypothesize that both miRNAs cooperate to modulate the expression of SP1 in osteoblasts and chondrocytes and interfering, consequently, with CX43 expression, and they might be further investigated as new possible biomarkers for OA.

Osteosarcoma cell-derived exosomes affect tumor microenvironment by specific packaging of microRNAs.

Bone microenvironment provides growth and survival signals essential for osteosarcoma (OS) initiation and progression. OS cells regulate communications inside tumor microenvironment through different ways and, among all, tumor-derived exosomes support cancer progression and metastasis. To define the contribution of OS-derived exosomes inside the microenvironment, we investigated the effects induced in bone remodeling mechanism and tumor angiogenesis. We demonstrated that exosomes promoted osteoclasts differentiation and bone resorption activity. Furthermore, exosomes potentiated tube formation of endothelial cells and increased angiogenic markers expression. We therefore investigated the micro RNA (miRNA) cargo from exosomes and their parental cells by performing small RNA sequencing through NGS Illumina platform. Hierarchical clustering highlighted a unique molecular profile of exosomal miRNA; bioinformatic analysis by DIANA-mirPath revealed that miRNAs identified take part in various biological processes and carcinogenesis. Among these miRNAs, some were already known for their involvement in the tumor microenvironment establishment, as miR-148a and miR-21-5p. Enforced expression of miR-148a and miR-21-5p in Raw264.7 and hTert immortalized umbilical vein endothelial cells recapitulated the effects induced by exosomes. Overall, our study highlighted the importance of OS exosomes in tumor microenvironment also by a specific packaging of miRNAs.

Bone's Response to Mechanical Loading in Aging and Osteoporosis: Molecular Mechanisms.

Mechanotransduction is pivotal in the maintenance of homeostasis in different tissues and involves multiple cell signaling pathways. In bone, mechanical stimuli regulate the balance between bone formation and resorption; osteocytes play a central role in this regulation. Dysfunctions in mechanotransduction signaling or in osteocytes response lead to an imbalance in bone homeostasis. This alteration is very relevant in some conditions such as osteoporosis and aging. Both are characterized by increased bone weakness due to different causes, for example, the increase of osteocyte apoptosis that cause an alteration of fluid space, or the alteration of molecular pathways. There are intertwined yet very different mechanisms involved among the cell-intrinsic effects of aging on bone, the cell-intrinsic and tissue-level effects of estrogen/androgen withdrawal on bone, and the effects of reduced mechanical loading on bone, which are all involved to some degree in how aged bone fails to respond properly to stress/strain compared to younger bone. This review aims at clarifying how the cellular and molecular pathways regulated and induced in bone by mechanical stimulation are altered with aging and in osteoporosis, to highlight new possible targets for antiresorptive or anabolic bone therapeutic approaches.

Long Non Coding RNA H19: A New Player in Hypoxia-Induced Multiple Myeloma Cell Dissemination.

The long non-coding RNA H19 (lncH19) is broadly transcribed in the first stage of development and silenced in most cells of an adult organism; it appears again in several tumors where, through different molecular mediators, promotes cell proliferation, motility and metastases. LncH19 has been associated with hypoxia-inducible factor 1-alpha (HIF-1α) activation and, in some tumors, it has proved to be necessary and required to sustain hypoxic responses. Here we propose to investigate a putative role for the lncH19 in hypoxia induced multiple myeloma (MM) progression. Transcriptional analysis of MM cell lines (RPMI and MM1.S) exposed to normoxia or hypoxia (1% O2) was done in order to evaluate lncH19 levels under hypoxic stimulation. Then, to investigate the role of lncH19 in hypoxia mediated MM progression, transcriptional, protein and functional assays have been performed on hypoxia stimulated MM cell lines, silenced or not for lncH19. Our data demonstrated that hypoxic stimulation in MM cell lines induced the overexpression of lncH19, which, in turn, is required for the expression of the hypoxia induced genes involved in MM dissemination, such as C-X-C Motif Chemokine Receptor 4 (CXCR4) and Snail. Moreover, adhesion assays demonstrated that lncH19 silencing abrogates the increased adhesion on stromal cells induced by the hypoxic condition. Finally, Western blot analysis indicated that lncH19 silencing impaired HIF1α nuclear translocation. The LncH19, required for the induction of hypoxic responses in MM cells, could represent a new therapeutic target for MM.

miR-31-5p Is a LIPUS-Mechanosensitive MicroRNA that Targets HIF-1α Signaling and Cytoskeletal Proteins.

The roles of low-intensity pulsed ultrasound (LIPUS) and microRNAs (miRNAs) on hMSCs commitments have already been investigated; however, the effects of the application of their co-treatments in an in vitro cell model are still unknown. Our previous studies demonstrated that (i) LIPUS modulated hMSCs cytoskeletal organization and (ii) miRNA-675-5p have a role in HIF-1α signaling modulation during hMSCs osteoblast commitment. We investigated for the first time the role of LIPUS as promoter tool for miRNA expression. Thanks to bioinformatic analysis, we identified miR-31-5p as a LIPUS-induced miRNA and investigated its role through in vitro studies of gain and loss of function. Results highlighted that LIPUS stimulation induced a hypoxia adaptive cell response, which determines a reorganization of cell membrane and cytoskeleton proteins. MiR-31-5p gain and loss of function studies, demonstrated as miR-31-5p overexpression, were able to induce hypoxic and cytoskeletal responses. Moreover, the co-treatments LIPUS and miR-31-5p inhibitor abolished the hypoxic responses including angiogenesis and the expression of Rho family proteins. MiR-31-5p was identified as a LIPUS-mechanosensitive miRNAs and may be considered a new therapeutic option to promote or abolish hypoxic response and cytoskeletal organization on hMSCs during the bone regeneration process.

Osteogenic commitment and differentiation of human mesenchymal stem cells by low-intensity pulsed ultrasound stimulation.

Low-intensity pulsed ultrasound (LIPUS) as an adjuvant therapy in in vitro and in vivo bone engineering has proven to be extremely useful. The present study aimed at investigating the effect of 30 mW/cm2 LIPUS stimulation on commercially available human mesenchymal stem cells (hMSCs) cultured in basal or osteogenic medium at different experimental time points (7, 14, 21 days). The hypothesis was that LIPUS would improve the osteogenic differentiation of hMSC and guarantying the maintenance of osteogenic committed fraction, as demonstrated by cell vitality and proteomic analysis. LIPUS stimulation (a) regulated the balance between osteoblast commitment and differentiation by specific networks (activations of RhoA/ROCK signaling and upregulation of Ribosome constituent/Protein metabolic process, Glycolysis/Gluconeogenesis, RNA metabolic process/Splicing and Tubulins); (b) allowed the maintenance of a few percentage of osteoblast precursors (21 days CD73+/CD90+: 6%; OCT-3/4+/NANOG+/SOX2+: 10%); (c) induced the activation of osteogenic specific pathways shown by gene expression (early: ALPL, COL1A1, late: RUNX2, BGLAP, MAPK1/6) and related protein release (COL1a1, OPN, OC), in particular in the presence of osteogenic soluble factors able to mimic bone microenvironment. To summarize, LIPUS might be able to improve the osteogenic commitment of hMSCs in vitro, and, at the same time, enhance their osteogenic differentiation.

Hypoxia-inducible factor 1Α may regulate the commitment of mesenchymal stromal cells toward angio-osteogenesis by mirna-675-5P.

BACKGROUND AIMS: During bone formation, angiogenesis and osteogenesis are regulated by hypoxia, which is able to induce blood vessel formation, as well as recruit and differentiate human mesenchymal stromal cells (hMSCs). The molecular mechanisms involved in HIF-1α response and hMSC differentiation during bone formation are still unclear. This study aimed to investigate the synergistic role of hypoxia and hypoxia-mimetic microRNA miR-675-5p in angiogenesis response and osteo-chondroblast commitment of hMSCs. METHODS: By using a suitable in vitro cell model of hMSCs (maintained in hypoxia or normoxia), the role of HIF-1α and miR-675-5p in angiogenesis and osteogenesis coupling was investigated, using fluorescence-activated cell sorting (FACS), gene expression and protein analysis. RESULTS: Hypoxia induced miR-675-5p expression and a hypoxia-angiogenic response, as demonstrated by increase in vascular endothelial growth factor messenger RNA and protein release. MiR-675-5p overexpression in normoxia promoted the down-regulation of MSC markers and the up-regulation of osteoblast and chondroblast markers, as demonstrated by FACS and protein analysis. Moreover, miR-675-5p depletion in a low-oxygen condition partially abolished the hypoxic response, including angiogenesis, and in particular restored the MSC phenotype, demonstrated by cytofluorimetric analysis. In addition, current preliminary data suggest that the expression of miR-675-5p during hypoxia plays an additive role in sustaining Wnt/ß-catenin pathways and the related commitment of hMSCs during bone ossification. DISCUSSION: MiR-675-5p may trigger complex molecular mechanisms that promote hMSC osteoblastic differentiation through a dual strategy: increasing HIF-1α response and activating Wnt/ß-catenin signaling.

Formation of Dendrimer Nanoassemblies by Oligomerization-Induced Liquid-Liquid Phase Separation.

Dendrimers are hyperbranched macromolecules with applications in host-guest chemistry, self-assembly, nanocatalysis, and nanomedicine. We show that dendrimer-based globular nanoparticles are formed by using dendrimer oligomerization to isothermally induce liquid-liquid phase separation (LLPS). We first determined that LLPS of aqueous mixtures of the fourth-generation amino-functionalized poly(amido amine) dendrimer is observed by lowering temperature in the presence of sodium sulfate. In relation to LLPS, we experimentally characterized the effect of salt and dendrimer concentrations on the LLPS temperature and salt-dendrimer isothermal partitioning. Our results were theoretically examined using a two-parameter thermodynamic model. We then showed that the addition of a small amount of glutaraldehyde, which leads to the formation of soluble dendrimer oligomers by chemical cross-linking, increases the LLPS temperature. This implies that a dendrimer aqueous mixture, which is initially homogeneous at room temperature and exhibits LLPS only at relatively low temperatures, can exhibit LLPS at room temperature due to dendrimer oligomerization. The high dendrimer concentration inside the nanodroplets, produced from LLPS, accelerates dendrimer cross-linking, thereby yielding stable globular nanoparticles. These nanomaterials retain the host-guest properties of the initial dendrimers, indicating potential applications as nanocatalysts, extracting agents and drug carriers. Our work provides the basis for a new approach for obtaining dendrimer-based nanoassemblies by employing low-generation dendrimers as building blocks.

Vitamin D Level Between Calcium-Phosphorus Homeostasis and Immune System: New Perspective in Osteoporosis.

Vitamin D is a key molecule in calcium and phosphate homeostasis; however, increasing evidence has recently shown that it also plays a crucial role in the immune system, both innate and adaptive. A deregulation of vitamin D levels, due also to mutations and polymorphisms in the genes of the vitamin D pathway, determines severe alterations in the homeostasis of the organism, resulting in a higher risk of onset of some diseases, including osteoporosis. This review gives an overview of the influence of vitamin D levels on the pathogenesis of osteoporosis, between bone homeostasis and immune system.

Thermoregulated Coacervation, Metal-Encapsulation and Nanoparticle Synthesis in Novel Triazine Dendrimers.

The synthesis and solubility behaviors of four generation five (G5) triazine dendrimers are studied. While the underivatized cationic dendrimer is soluble in water, the acetylated and propanoylated derivatives undergo coacervation in water upon increasing temperature. Occurring around room temperature, this behavior is related to a liquid-liquid phase transition with a lower critical solution temperature (LCST) and is explained by differences in composition, notably, the hydrophobic nature of the terminal groups. Interestingly, the water solubility of the acetylated dendrimer is affected by the addition of selected metal ions. Titrating solutions of acetylated dendrimer at temperatures below the LCST with gold or palladium ions promoted precipitation, but platinum, iridium, and copper did not. Gold nanoparticles having diameters of 2.5 ± 0.8 nm can be obtained from solutions of the acetylated dendrimer at concentrations of gold less than that required to induce precipitation by treating the solution with sodium borohydride.

CD90+ liver cancer cells modulate endothelial cell phenotype through the release of exosomes containing H19 lncRNA.

BACKGROUND: CD90+ liver cancer cells have been described as cancer stem-cell-like (CSC), displaying aggressive and metastatic phenotype. Using two different in vitro models, already described as CD90+ liver cancer stem cells, our aim was to study their interaction with endothelial cells mediated by the release of exosomes. METHODS: Exosomes were isolated and characterized from both liver CD90+ cells and hepatoma cell lines. Endothelial cells were treated with exosomes, as well as transfected with a plasmid containing the full length sequence of the long non-coding RNA (lncRNA) H19. Molecular and functional analyses were done to characterize the endothelial phenotype after treatments. RESULTS: Exosomes released by CD90+ cancer cells, but not by parental hepatoma cells, modulated endothelial cells, promoting angiogenic phenotype and cell-to-cell adhesion. LncRNA profiling revealed that CD90+ cells were enriched in lncRNA H19, and released this through exosomes. Experiments of gain and loss of function of H19 showed that this LncRNA plays an important role in the exosome-mediated phenotype of endothelial cells. CONCLUSIONS: Our data indicate a new exosome-mediated mechanism by which CSC-like CD90+ cells could influence their tumor microenvironment by promoting angiogenesis. Moreover, we suggest the lncRNA H19 as a putative therapeutic target in hepatocellular carcinoma.

Unusual liquid-liquid phase transition in aqueous mixtures of a well-known dendrimer.

Liquid-liquid phase separation (LLPS) has been extensively investigated for polymer and protein solutions due to its importance in mixture thermodynamics, separation science and self-assembly processes. However, to date, no experimental studies have been reported on LLPS of dendrimer solutions. Here, it is shown that LLPS of aqueous solutions containing a hydroxyl-functionalized poly(amido amine) dendrimer of fourth generation is induced in the presence of sodium sulfate. Both the LLPS temperature and salt-dendrimer partitioning between the two coexisting phases at constant temperature were measured. Interestingly, our experiments show that LLPS switches from being induced by cooling to being induced by heating as the salt concentration increases. The two coexisting phases also show opposite temperature response. Thus, this phase transition exhibits a simultaneous lower and upper critical solution temperature-type behavior. Dynamic light-scattering and dye-binding experiments indicate that no appreciable conformational change occurs as the salt concentration increases. To explain the observed phase behavior, a thermodynamic model based on two parameters was developed. The first parameter, which describes dendrimer-dendrimer interaction energy, was determined by isothermal titration calorimetry. The second parameter describes the salt salting-out strength. By varying the salting-out parameter, it is shown that the model achieves agreement not only with the location of the experimental binodal at 25 °C but also with the slope of this curve around the critical point. The proposed model also predicts that the unusual temperature behavior of this phase transition can be described as the net result of two thermodynamic factors with opposite temperature responses: salt thermodynamic non-ideality and salting-out strength.

Preliminary osteogenic and antibacterial investigations of wood derived antibiotic-loaded bone substitute for the treatment of infected bone defects.

Introduction: The development of reliable treatments for infected or potentially infected bone loss resulting from open fractures and non-unions is extremely urgent, especially to reduce the prolonged courses of antimicrobial therapy to which affected patients are subjected. Numerous bone graft substitutes have been used over the years, but there are currently no effective solutions to treat critical bone loss, especially in the presence of infection. The present study evaluated the use of the biomorphic calcium phosphate bone scaffold b. Bone™, based on a next-generation resorbable biomimetic biomaterial, in bone reconstruction surgery in cases of infection. Methods: Using an "in vitro 3D bone fracture model" to predict the behavior of this drug delivery system during critical bone loss at an infected (or potentially infected) site, the effects of scaffolds loaded with gentamicin or vancomycin on the viability and differentiation capacity of human mesenchymal stem cells (hMSCs) were evaluated. Results: This scaffold, when loaded with gentamicin or vancomycin, exhibits a typical drug release curve that determines the inhibitory effects on the growth of Staphylococcus aureus, Enterococcus faecalis, and Escherichia coli, as well as relative biofilm formation. Discussion: The study demonstrates that b.bone scaffolds can effectively address key challenges in orthopedic surgery and patient care by inhibiting bacterial growth and biofilm formation through rapid, potent antibiotic release, reducing the risk of treatment failure due to resistance, and providing a promising solution for bone infections and improved patient outcomes. Future studies could explore the combination of different antibiotics on these scaffolds for more tailored and effective treatments against post-traumatic osteomyelitis pathogens.

Synthesis of large dendrimers with the dimensions of small viruses.

The dendrimer chemistry reported offers a route to synthetic target molecules with spherical shape, well-defined surface chemistries, and dimensions that match the size of virus particles. The largest target, a generation-13 dendrimer comprising triazines linked by diamines, is stable across ranges of concentration, pH, temperature, solvent polarity and in the presence of additives. This dendrimer theoretically presents 16,384 surface groups and has a molecular weight exceeding 8.4 MDa. Transmission electron and atomic force microscopies, dynamic light scattering, and computations reveal a diameter of ~30 nm. The target was synthesized through an iterative divergent approach using a monochlorotriazine macromonomer providing two generations of growth per synthetic cycle. Fidelity in the synthesis is supported by evidence from NMR spectroscopy, mass spectrometry, and high-pressure liquid chromatography.

Design, synthesis and biological assessment of a triazine dendrimer with approximately 16 Paclitaxel groups and 8 PEG groups.

The synthesis and characterization of a generation three triazine dendrimer that displays a phenolic group at the core for labeling, up to eight 5 kDa PEG chains for solubility, and 16 paclitaxel groups is described. Three different diamine linkers--dipiperidine trismethylene, piperazine, and aminomethylpiperidine--were used within the dendrimer. To generate the desired stoichiometric ratio of 8 PEG chains to 16 paclitaxel groups, a monochlorotriazine was prepared with two paclitaxel groups attached through their 2'-hydroxyls using a linker containing a labile disulfide. This monochlorotriazine was linked to a dichlorotriazine with aminomethylpiperidine. The resulting dichlorotriazine bearing two paclitaxel groups could be reacted with the eight amines of the dendrimer. NMR and MALDI-TOF confirm successful reaction. The eight monochlorotriazines of the resulting material are used as the site for PEGylation affording the desired 2:1 stoichiometry. The target and intermediates were amenable to characterization by (1)H and (13)C NMR, and mass spectrometry. Analysis revealed that 16 paclitaxel groups were installed along with 5-8 PEG chains. The final construct is 63% PEG, 22% paclitaxel, and 15% triazine dendrimer. Consistent with previous efforts and computational models, 5 kDa PEG groups were essential for making the target water-soluble. Molecular dynamics simulations showed a high degree of hydration of the core, and a radius of gyration of 2.8 ± 0.2 nm. The hydrodynamic radius of the target was found to be 15.8 nm by dynamic light scattering, an observation indicative of aggregation. Drug release studies performed in plasma showed slow and identical release in mouse and rat plasma (8%, respectively). SPECT/CT imaging was used to follow biodistribution and tumor uptake. Using a two component model, the elimination and distribution half-lives were 2.65 h and 38.2 h, respectively. Compared with previous constructs, this dendrimer persists in the vasculature longer (17.33 ± 0.88% ID/g at 48 h postinjection), and showed higher tumor uptake. Low levels of dendrimer were observed in lung, liver, and spleen (~6% ID/g). Tumor saturation studies of small prostate cancer tumors (PC3) suggest that saturation occurs at a dose between 23.2 mg/kg and 70.9 mg/kg.