Amino acid-functionalized dendrimers with heterobifunctional chemoselective peripheral groups for drug delivery applications

siRNA incorporated in slow-release injectable hydrogel continuously silences DDIT4 and regulates nucleus pulposus cell pyroptosis through the ROS/TXNIP/NLRP3 axis to alleviate intervertebral disc degeneration

Aims

In this investigation, we administered oxidative stress to nucleus pulposus cells (NPCs), recognized DNA-damage-inducible transcript 4 (DDIT4) as a component in intervertebral disc degeneration (IVDD), and devised a hydrogel capable of conveying small interfering RNA (siRNA) to IVDD.

Methods

An in vitro model for oxidative stress-induced injury in NPCs was developed to elucidate the mechanisms underlying the upregulation of DDIT4 expression, activation of the reactive oxygen species (ROS)-thioredoxin-interacting protein (TXNIP)-NLRP3 signalling pathway, and nucleus pulposus pyroptosis. Furthermore, the mechanism of action of small interfering DDIT4 (siDDIT4) on NPCs in vitro was validated. A triplex hydrogel named siDDIT4@G5-P-HA was created by adsorbing siDDIT4 onto fifth-generation polyamidoamine (PAMAM) dendrimer using van der Waals interactions, and then coating it with hyaluronic acid (HA). In addition, we established a rat puncture IVDD model to decipher the hydrogel's mechanism in IVDD.

Results

A correlation between DDIT4 expression levels and disc degeneration was shown with human nucleus pulposus and needle-punctured rat disc specimens. We confirmed that DDIT4 was responsible for activating the ROS-TXNIP-NLRP3 axis during oxidative stress-induced pyroptosis in rat nucleus pulposus in vitro. Mitochondria were damaged during oxidative stress, and DDIT4 contributed to mitochondrial damage and ROS production. In addition, siDDIT4@G5-P-HA hydrogels showed good delivery activity of siDDIT4 to NPCs. In vitro studies illustrated the potential of the siDDIT4@G5-P-HA hydrogel for alleviating IVDD in rats.

Conclusion

DDIT4 is a key player in mediating pyroptosis and IVDD in NPCs through the ROS-TXNIP-NLRP3 axis. Additionally, siDDIT4@G5-P-HA hydrogel has been found to relieve IVDD in rats. Our research offers an innovative treatment option for IVDD.

Specific Bifunctionalization on the Surface of Phosphorus Dendrimers Syntheses and Properties

Dendrimers are highly branched macromolecules possessing, in most cases, identical terminal functions. However, it is sometimes desirable to have two types of surface functions in order to fulfil specific properties. The stochastic functionalization is frequently used for such purposes, but the presence of an uncontrolled number of each type of terminal function, albeit acceptable for research purposes, has no practical use. Thus, it is highly desirable to find strategies suitable for the precise grafting of two different functional groups on the surface of dendrimers. The easiest way, and the most widely used, consists in using a bifunctional monomer to be grafted to all of the surface functions of the dendrimers. Two other strategies are known but are rarely used: the modification of an existing function, to generate two functions, and the sequential grafting of one function then of a second function. The three methods are illustrated in this review with polyphosphorhydrazone (PPH) dendrimers, together with their properties as catalysts, for materials, and as biological tools.

A Guideline for the Synthesis of Amino-Acid-Functionalized Monomers and Their Polymerizations

Amino acids have emerged as a sustainable source for the design of functional polymers. Besides their wide availability, especially their high degree of biocompatibility makes them appealing for a broad range of applications in the biomedical research field. In addition to these favorable characteristics, the versatility of reactive functional groups in amino acids (i.e., carboxylic acids, amines, thiols, and hydroxyl groups) makes them suitable starting materials for various polymerization approaches, which include step- and chain-growth reactions. This review aims to provide an overview of strategies to incorporate amino acids into polymers. To this end, it focuses on the preparation of polymerizable monomers from amino acids, which yield main chain or side chain-functionalized polymers. Furthermore, postpolymerization modification approaches for polymer side chain functionalization are discussed. Amino acids are presented as a versatile platform for the development of polymers with tailored properties.

Synthesis of Multiarm Peptide Dendrimers for Dual Targeted Thrombolysis

Current thrombolytic agents generally possess low specificity and pose a high risk of intracranial hemorrhage. Here, various generations of multiarm polylactic acid-polyglutamic acid peptide dendrimers were synthesized, and then nattokinase-combining magnetic Fe₃O₄ nanoparticles and RGD-modified dendrimers (Fe₃O₄-(4-PLA(G₃)₄)-RGD) were fabricated for targeted thrombi dissolution. Their in vitro and in vivo thrombolytic properties were determined. In vitro determination indicated that Fe₃O₄-(4-PLA(G₃)₄)-RGD/nattokinase provided 3-fold higher blood clot dissolution than that obtained with free nattokinase. An in vivo thrombolytic examination revealed that most of the thrombi were dissolved under an external magnetic field. In addition, there were many nanoparticles in vascular endothelial cells, demonstrating the RGD and magnetic dual targeting capacity of Fe₃O₄-(4-PLA(G₃)₄)-RGD/nattokinase. These results demonstrated that Fe₃O₄-(4-PLA(G₃)₄)-RGD nanoparticles not only will deliver targeted thrombolytic agents to enhance the efficacy of site-specific thrombolytic treatment but also have potential in the diagnosis of thrombotic disease in its early stages.

Dendrimer nanoparticles for colorectal cancer applications

Cancer nanotechnology is a prolific field of research, where nanotools are employed to diagnose and treat cancer with unprecedented precision. Targeted drug delivery is fundamental for more efficient cancer treatments. For this, nanoparticles have been extensively used during the past few years in order to improve the specificity, selectivity and controlled release of drug delivery. It holds potential in minimizing systemic toxicity through the development of functionalized particles for targeted treatment. Among all the type of nanoparticles, dendrimers display several advantages, which make them ideal candidates for improved and targeted drug delivery in cancer research. Dendrimers can transport large amounts of drug into specific areas. In addition, they can be employed for monitoring the progress of the treatment process, with an unprecedented theranostic capability. Special emphasis is given to colorectal cancer and to the preferred employed strategies for producing drug-loaded/functionalized NPs for cancer therapy in the past few years.

Polymeric Nanoparticles Based on Tyrosine-Modified, Low Molecular Weight Polyethylenimines for siRNA Delivery

A major hurdle for exploring RNA interference (RNAi) in a therapeutic setting is still the issue of in vivo delivery of small RNA molecules (siRNAs). The chemical modification of polyethylenimines (PEIs) offers a particularly attractive avenue towards the development of more efficient non-viral delivery systems. Here, we explore tyrosine-modified polyethylenimines with low or very low molecular weight (P2Y, P5Y, P10Y) for siRNA delivery. In comparison to their respective parent PEI, they reveal considerably increased knockdown efficacies and very low cytotoxicity upon tyrosine modification, as determined in different reporter and wildtype cell lines. The delivery of siRNAs targeting the anti-apoptotic oncogene survivin or the serine/threonine-protein kinase PLK1 (polo-like kinase 1; PLK-1) oncogene reveals strong inhibitory effects in vitro. In a therapeutic in vivo setting, profound anti-tumor effects in a prostate carcinoma xenograft mouse model are observed upon systemic application of complexes for survivin or PLK1 knockdown, in the absence of in vivo toxicity. We thus demonstrate the tyrosine-modification of (very) low molecular weight PEIs for generating efficient nanocarriers for siRNA delivery in vitro and in vivo, present data on their physicochemical and biological properties, and show their efficacy as siRNA therapeutic in vivo, in the absence of adverse effects.

Cytotoxicity of Dendrimers

Drug delivery systems are molecular platforms in which an active compound is packed into or loaded on a biocompatible nanoparticle. Such a solution improves the activity of the applied drug or decreases its side effects. Dendrimers are promising molecular platforms for drug delivery due to their unique properties. These macromolecules are known for their defined size, shape, and molecular weight, as well as their monodispersity, the presence of the void space, tailorable structure, internalization by cells, selectivity toward cells and intracellular components, protection of guest molecules, and controllable release of the cargo. Dendrimers were tested as carriers of various molecules and, simultaneously, their toxicity was examined using different cell lines. It was discovered that, in general, dendrimer cytotoxicity depended on the generation, the number of surface groups, and the nature of terminal moieties (anionic, neutral, or cationic). Higher cytotoxicity occurred for higher-generation dendrimers and for dendrimers with positive charges on the surface. In order to decrease the cytotoxicity of dendrimers, scientists started to introduce different chemical modifications on the periphery of the nanomolecule. Dendrimers grafted with polyethylene glycol (PEG), acetyl groups, carbohydrates, and other moieties did not affect cell viability, or did so only slightly, while still maintaining other advantageous properties. Dendrimers clearly have great potential for wide utilization as drug and gene carriers. Moreover, some dendrimers have biological properties per se, being anti-fungal, anti-bacterial, or toxic to cancer cells without affecting normal cells. Therefore, intrinsic cytotoxicity is a comprehensive problem and should be considered individually depending on the potential destination of the nanoparticle.

Fluorine polymer probes for magnetic resonance imaging: quo vadis?

Over the last few years, the development and relevance of 19F magnetic resonance imaging (MRI) for use in clinical practice has emerged. MRI using fluorinated probes enables the achievement of a specific signal with high contrast in MRI images. However, to ensure sufficient sensitivity of 19F MRI, fluorine probes with a high content of chemically equivalent fluorine atoms are required. The majority of 19F MRI agents are perfluorocarbon emulsions, which have a broad range of applications in molecular imaging, although the content of fluorine atoms in these molecules is limited. In this review, we focus mainly on polymer probes that allow higher fluorine content and represent versatile platforms with properties tailorable to a plethora of biomedical in vivo applications. We discuss the chemical development, up to the first imaging applications, of these promising fluorine probes, including injectable polymers that form depots that are intended for possible use in cancer therapy.

Highly biocompatible zwitterionic dendrimer-encapsulated platinum nanoparticles for sensitive detection of glucose in complex medium

The sensitive detection of glucose using zwitterionic dendrimer-encapsulated platinum nanoparticles was not affected by proteins.

Combinatorial Nanoparticle Delivery of siRNA and Antineoplastics for Lung Cancer Treatment

Recent developments in nanotechnology, especially in drug delivery systems, are advanced by featuring novel multifunctional nanoparticles that promise safe, specific, and efficient therapeutic delivery for cancer treatment. Multifunctional nanoparticle-based drug delivery systems enable simultaneous delivery of multiple therapeutic agents for effective combination therapy for cancer. In this chapter, we provide detailed protocols for development and application of a multifunctional nanoparticle system for combinatorial delivery of a chemotherapeutic (cisplatin) and small interfering RNA (siRNA) for human antigen R (HuR) mRNA in cancer cells using a polyamidoamine (PAMAM) dendrimer platform. Protocols for nanoparticle functionalization with folic acid (FA) for targeted delivery of therapeutics toward folate receptor (FR)-overexpressing cancer cells are also described. Further, methods employed for physiochemical and functional characterization of the multifunctional nanoparticle system are discussed in detail. Using the methods described in this chapter, researchers would be able to develop PAMAM dendrimer-based multifunctional nanoparticles for targeted delivery of chemotherapeutics and siRNA combinations. We also provide an example showing the dendrimer-polyethyleneimine-cis-diamminedichloroplatinum-siRNA-folic acid (Den-PEI-CDDP-siRNA-FA) nanoparticle system developed was therapeutically effective toward non-small cell lung cancer (NSCLC) cell lines (H1299 and A549) while exhibiting reduced toxicity to normal lung fibroblast (MRC9) cells.

Enhanced glucose detection using dendrimer encapsulated gold nanoparticles benefiting from their zwitterionic surface

The application of ultrasmall gold nanoparticles as enzyme mimics has been drawing great attention. Herein, we developed zwitterionic dendrimer encapsulated gold nanoparticles (Au-G5MC NPs) for highly sensitive and simple colorimetric detection of glucose. Au-G5MC NPs showed peroxidase-like property, which could efficiently catalyze oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H₂O₂, producing a blue color product (oxTMB). This peroxidase-like reaction follows a typical Michaelis-Menten kinetics. The K_m towards TMB exhibited a lower value (0.194 mM) than that of horseradish peroxidase (HRP, 0.434 mM). Furthermore, the peroxidase-like properties of Au-G5MC NPs enable colorimetric detection of the concentration of glucose with high selectivity. The linear concentration range of this method was from 14 μM to 166 μM with the detection limit down to 3.8 μM. More importantly, the detection was not interfered by proteins due to the single zwitterionic layer on the Au-G5MC NPs surface. These excellent properties are attributed to the ultrasmall size of gold nanoparticles and high stability of Au-G5MC NPs in complex medium. This catalytic system might have great potential applications for glucose detection in medical diagnostics and biochemistry in the future.

Self-Assembled Thermoresponsive Polymeric Nanogels for 19F MR Imaging

Magnetic resonance imaging using fluorinated contrast agents (¹⁹F MRI) enables to achive highcontrast in images due to the negligible fluorine background in living tissues. In this pilot study, we developed new biocompatible, temperature-responsive, and easily synthesized polymeric nanogels containing a sufficient concentration of magnetically equivalent fluorine atoms for ¹⁹F MRI purposes. The structure of the nanogels is based on amphiphilic copolymers containing two blocks, a hydrophilic poly[ N-(2-hydroxypropyl)methacrylamide] (PHPMA) or poly(2-methyl-2-oxazoline) (PMeOx) block, and a thermoresponsive poly[ N(2,2difluoroethyl)acrylamide] (PDFEA) block. The thermoresponsive properties of the PDFEA block allow us to control the process of nanogel self-assembly upon its heating in an aqueous solution. Particle size depends on the copolymer composition, and the most promising copolymers with longer thermoresponsive blocks form nanogels of suitable size for angiogenesis imaging or the labeling of cells (approximately 120 nm). The in vitro ¹⁹F MRI experiments reveal good sensitivity of the copolymer contrast agents, while the nanogels were proven to be noncytotoxic for several cell lines.

Highly stable and biocompatible zwitterionic dendrimer-encapsulated palladium nanoparticles that maintain their catalytic activity in bacterial solution

This study offers a method for constructing an artificial enzyme (Pd_n-G5MC), which maintains its catalytic efficiency in bacterial solution.

Chemo-biologic combinatorial drug delivery using folate receptor-targeted dendrimer nanoparticles for lung cancer treatment

Co-administration of functionally distinct anti-cancer agents has emerged as an efficient strategy in lung cancer treatment. However, a specially designed drug delivery system is required to co-encapsulate functionally different agents, such as a combination of siRNA and chemotherapy, for targeted delivery. We developed a folic acid (FA)-conjugated polyamidoamine dendrimer (Den)-based nanoparticle (NP) system for co-delivery of siRNA against HuR mRNA (HuR siRNA) and cis-diamine platinum (CDDP) to folate receptor-α (FRA) -overexpressing H1299 lung cancer cells. The co-delivery of HuR siRNA and CDDP using the FRA-targeted NP had a significantly greater therapeutic effect than did individual therapeutics. Further, the FRA-targeted NP exhibited improved cytotoxicity compared to non-targeted NP against lung cancer cells. Finally, the NP showed negligible toxicity towards normal MRC9 lung fibroblast cells. Thus, the present study demonstrates FRA-targeted Den nanoparticle system as a suitable carrier for targeted co-delivery of siRNA and chemotherapy agents in lung cancer cells.

In Situ-Forming Polyamidoamine Dendrimer Hydrogels with Tunable Properties Prepared via Aza-Michael Addition Reaction

In this work, we describe synthesis and characterization of novel in situ-forming polyamidoamine (PAMAM) dendrimer hydrogels (DHs) with tunable properties prepared via highly efficient aza-Michael addition reaction. PAMAM dendrimer G5 was chosen as the underlying core and functionalized with various degrees of acetylation using acetic anhydride. The nucleophilic amines on the dendrimer surface reacted with α, β-unsaturated ester in acrylate groups of polyethylene glycol diacrylate (PEG-DA, Mn = 575 g/mol) via aza-Michael addition reaction to form dendrimer hydrogels without the use of any catalyst. The solidification time, rheological behavior, network structure, swelling, and degradation properties of the hydrogel were tuned by adjusting the dendrimer surface acetylation degree and dendrimer concentration. The DHs were shown to be highly cytocompatible and support cell adhesion and proliferation. We also prepared an injectable dendrimer hydrogel formulation to deliver the anticancer drug 5-fluorouracil (5-FU) and demonstrated that the injectable formulation efficiently inhibited tumor growth following intratumoral injection. Taken together, this new class of dendrimer hydrogel prepared by aza-Michael addition reaction can serve as a safe tunable platform for drug delivery and tissue engineering.

Highly stable and biocompatible dendrimer-encapsulated gold nanoparticle catalysts for the reduction of 4-nitrophenol

The enhanced properties of dendrimer-encapsulated gold nanoparticles were attributed to the single zwitterionic layer on the new dendrimer template.

Synthesis and Biological Activity of Highly Cationic Dendrimer Antibiotics

The development of pathogenic bacteria resistant to current treatments is a major issue facing the world today. Here, the synthesis and biological activity of fourth generation poly(amidoamine) dendrimers decorated with 1-hexadecyl-azoniabicylo[2.2.2]octane (C₁₆-DABCO), a quaternary ammonium compound known to have antibacterial activity, are described. This highly cationic dendrimer antibiotic was tested against several Gram positive and Gram negative strains of pathogenic bacteria and exhibited activity against both. Higher activity toward the Gram positive strains that were tested was observed. After the antimicrobial activity was assessed, E. coli and B. cereus were subjected to a resistance selection study. This study demonstrated that a multivalent approach to antimicrobial design significantly reduces the likelihood of developing bacterial resistance. Highly cationic dendrimers were also used as pretreatment of a membrane to prevent biofilm formation.

Synthesis and characterization of a PAMAM-OH derivative containing an acid-labile β-thiopropionate bond for gene delivery

The present report describes the synthesis of a hydroxyl terminal PAMAM dendrimer (PAMAM-OH) derivative (PAMSPF). The hydroxyls of PAMAM-OH were attached to S-Methyl-l-cysteine (SMLC) via an acid-labile ester bond, named as β-thiopropionate bond, followed by modification with folic acid (FA) through a polyethylene glycol (PEG) linker. The degrees of attachment of SMLC and FA to the PAMAM-OH backbone were 83.9% and 12.8%, respectively. PAMSPF could condense DNA to form spherical nanoparticles with particle sizes of ∼200nm and remain stable in the presence of heparin and nuclease. The β-thiopropionate bond in PAMSPF was hydrolyzed completely and the DNA release rate was 95.8±3.3% after incubation under mildly acidic conditions at 37°C for 3h. PAMSPF/DNA was less cytotoxic to KB and HepG2 cells and exhibited a higher gene transfection efficiency than native PAMAM/DNA. The uptake assays showed that PAMSPF/DNA entered KB cells within 0.5h through folate receptor-mediated endocytosis and escaped from endosomes within 2h. In addition, PAMSPF/DNA displayed long circulation time along with excellent targeting of tumor sites in vivo. These findings demonstrate that PAMSPF is an excellent carrier for safe and effective gene delivery.

Synthesis, nanoprecipitation and pH sensitivity of amphiphilic linear-dendritic hybrid polymers and hyperbranched-polydendrons containing tertiary amine functional dendrons

The combination of linear polymers with dendritic chain-ends has led to numerous studies of linear-dendritic polymer hybrid materials. Interchain branching within the linear segment of these materials has recently extended this concept to the formation of soluble hyperbranched-polydendrons. Here, the introduction of amphiphilicity into hyperbranched-polydendrons has been achieved for the first time through the use of tertiary amine functional dendritic chain-ends and branched hydrophobic polymer segments. The synthesis and aqueous nanoprecipitation of these branched materials is compared with their linear-dendritic polymer analogues, showing that chain-end chemistry/generation, precipitation medium pH and polymer architecture are all capable of influencing the ability to generate nanoparticles, the resulting nanoparticle diameter and dispersity, and subsequent response to changes in pH.

Designing Dendrimer and Miktoarm Polymer Based Multi-Tasking Nanocarriers for Efficient Medical Therapy

To address current complex health problems, there has been an increasing demand for smart nanocarriers that could perform multiple complimentary biological tasks with high efficacy. This has provoked the design of tailor made nanocarriers, and the scientific community has made tremendous effort in meeting daunting challenges associated with synthetically articulating multiple functions into a single scaffold. Branched and hyper-branched macromolecular architectures have offered opportunities in enabling carriers with capabilities including location, delivery, imaging etc. Development of simple and versatile synthetic methodologies for these nanomaterials has been the key in diversifying macromolecule based medical therapy and treatment. This review highlights the advancement from conventional "only one function" to multifunctional nanomedicine. It is achieved by synthetic elaboration of multivalent platforms in miktoarm polymers and dendrimers by physical encapsulation, covalent linking and combinations thereof.

On the Possibility of Facilitated Diffusion of Dendrimers Along DNA

We investigate the electrostatics, energetics, and dynamics of dendrimer-DNA interactions that mimic protein-DNA complexes as a means to design facilitated mechanisms by which dendrimers can slide and search DNA for targets. By using all-atom molecular dynamics simulations, we calculated the free energy profiles of dendrimer-binding around the DNA via umbrella sampling. We also calculated electrostatic interaction maps in comparison to proteins, as well as the dynamical changes induced by DNA-dendrimer interactions via NMR-measurable order parameters. Our results show that for dendrimers to go around DNA, there is a free-energy barrier of 8.5 kcal/mol from the DNA major groove to DNA minor groove, with a minimum in the major groove. This barrier height makes it unlikely for an all-amine dendrimer to slide along DNA longitudinally, but following a helical path may be possible along the major groove. Comparison of the nonbonded interaction energy and the interaction free-energy profiles reveal a considerable entropic cost as the dendrimer binds to DNA. This is also supported by the mobility patterns obtained from NMR-measurable order parameter values, which show a decreased mobility of the dendrimer N-H bond vectors in the DNA-binding mode.

A series of codendrimers from polyamidoamine (PAMAM) and oligoethylene glycols (OEG) dendrons as drug carriers: the effect of OEG dendron decoration degree

To evaluate the effect of OEG dendron decoration degree and find a suitable carrier, a series of codendrimers are prepared and utilized to transport methotrexate.

Advances in combination therapies based on nanoparticles for efficacious cancer treatment: an analytical report

The main objective of nanomedicine research is the development of nanoparticles as drug delivery systems or drugs per se to tackle diseases as cancer, which are a leading cause of death with developed nations. Targeted treatments against solid tumors generally lead to dramatic regressions, but, unfortunately, the responses are often short-lived due to resistant cancer cells. In addition, one of the major challenges of combination drug therapy (called "cocktail") is the crucial optimization of different drug parameters. This issue can be solved using combination nanotherapy. Nanoparticles developed in oncology based on combination nanotherapy are either (a) those designed to combat multidrug resistance or (b) those used to circumvent resistance to clinical cancer drugs. This review provides an overview of the different nanoparticles currently used in clinical treatments in oncology. We analyze in detail the development of combinatorial nanoparticles including dendrimers for dual drug delivery via two strategic approaches: (a) use of chemotherapeutics and chemosensitizers to combat multidrug resistance and (b) use of multiple cytotoxic drugs. Finally, in this review, we discuss the challenges, clinical outlook, and perspectives of the nanoparticle-based combination therapy in cancer.

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

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

Codendrimer from polyamidoamine (PAMAM) and oligoethylene dendron as a thermosensitive drug carrier

The efficient synthesis of codendrimer PAMAM-co-OEG (PAG) and its properties in aqueous solution, including particle size and thermosensitivity, are described. PAG is synthesized with well-defined structure through the "attach to" route. In the aqueous solutions, PAG forms unimer and multimolecular aggregates with the respective particle sizes of approximately 8 and 200 nm, depending on the concentration. PAG shows thermosensitive behavior with sharp and fast transition, and the lower critical solution temperature is 38.2 °C. The suitability of codendrimer PAG as the thermosensitive carrier is evaluated with methotrexate (MTX) as the model drug. MTX is encapsulated in PAG with the drug-loading capacity of 39%, among which 30% of MTX is encapsulated in PAMAM core. The release behavior of MTX mediated by temperature is investigated with focus on the effects around the LCST of PAG.

Comparative anti-inflammatory activity of poly(amidoamine) (PAMAM) dendrimer-dexamethasone conjugates with dexamethasone-liposomes

Lipophilicity vs hydrophicility physicochemical traits are extremely important variables that are active considerations for optimizing drug delivery systems. The comparative anti-inflammatory delivery potential of dexamethasone (dex) in an encapsulation-based (liposome-lipophilic) and poly (amidoamine) (PAMAM) dendrimer prodrug conjugation-based delivery systems (hydrophilic) was performed in this work. Dendrimer prodrug conjugates were characterized by (1)H NMR. The drug encapsulation efficiency for drug in liposomes was observed to be 14.02% and this was correlated with a dose-dependent tumor necrosis factor (TNF)-α inhibition (39-57% inhibition). The biological evaluation of nanocarriers for drug was demonstrated in a standard, conventionally used in vitro cell-based system for TNF-α inhibition. This served as a comparative tool to demonstrate a quantitatively higher TNF-α inhibition (67-71.48%) produced by the dendrimer-dex drug conjugate. The structure activity relationship (dose-for-dose) was inferred by relatively lesser inhibition of TNF-α by variants of PAMAM G4 (NH2) dendrimer-dex conjugates and was compared with liposomes carrying dex. In vitro results suggest that the prodrug conjugates of PAMAM dendrimer deliver dex to be more efficient in comparison with liposome-based dex in terms of higher TNF-α inhibition. This study has implications in designing efficient prodrug nanocarrier systems for delivering dex.

Dendrimer-based postnatal therapy for neuroinflammation and cerebral palsy in a rabbit model

Cerebral palsy (CP) is a chronic childhood disorder with no effective cure. Neuroinflammation, caused by activated microglia and astrocytes, plays a key role in the pathogenesis of CP and disorders such as Alzheimer's disease and multiple sclerosis. Targeting neuroinflammation can be a potent therapeutic strategy. However, delivering drugs across the blood-brain barrier to the target cells for treating diffuse brain injury is a major challenge. We show that systemically administered polyamidoamine dendrimers localize in activated microglia and astrocytes in the brain of newborn rabbits with CP, but not healthy controls. We further demonstrate that dendrimer-based N-acetyl-l-cysteine (NAC) therapy for brain injury suppresses neuroinflammation and leads to a marked improvement in motor function in the CP kits. The well-known and safe clinical profile for NAC, when combined with dendrimer-based targeting, provides opportunities for clinical translation in the treatment of neuroinflammatory disorders in humans. The effectiveness of the dendrimer-NAC treatment, administered in the postnatal period for a prenatal insult, suggests a window of opportunity for treatment of CP in humans after birth.