Influence of the reducing-end anomeric configuration of the Man9 epitope on DC-SIGN recognition.

High-mannose (Man9GlcNAc2) is the main carbohydrate unit present in viral envelope glycoproteins such as gp120 of HIV and the GP1 of Ebola virus. This oligosaccharide comprises the Man9 epitope conjugated to two terminal N-acetylglucosamines by otherwise rarely-encountered ß-mannose glycosidic bond. Formation of this challenging linkage is the bottleneck of the few synthetic approaches described to prepare high mannose. Herein, we report the synthesis of the Man9 epitope with both alpha and beta configurations at the reducing end, and subsequent evaluation of the impact of this configuration on binding to natural receptor of high-mannose, DC-SIGN. Using fluorescence polarization assays, we demonstrate that both anomers bind to DC-SIGN with comparable affinity. These relevant results therefore indicate that the more synthetically-accesible Man9 alpha epitope may be deployed as ligand for DC-SIGN in both in vitro and in vivo biological assays.

Click chemistry with polymers, dendrimers, and hydrogels for drug delivery.

During the last decades, great efforts have been devoted to design polymers for reducing the toxicity, increasing the absorption, and improving the release profile of drugs. Advantage has been also taken from the inherent multivalency of polymers and dendrimers for the incorporation of diverse functional molecules of interest in targeting and diagnosis. In addition, polymeric hydrogels with the ability to encapsulate drugs and cells have been developed for drug delivery and tissue engineering applications. In the long road to this successful story, pharmaceutical sciences have been accompanied by parallel advances in synthetic methodologies allowing the preparation of precise polymeric materials with enhanced properties. In this context, the introduction of the click concept by Sharpless and coworkers in 2001 focusing the attention on modularity and orthogonality has greatly benefited polymer synthesis, an area where reaction efficiency and product purity are significantly challenged. The purpose of this Expert Review is to discuss the impact of click chemistry in the preparation and functionalization of polymers, dendrimers, and hydrogels of interest in drug delivery.

Click chemistry for drug delivery nanosystems.

The purpose of this Expert Review is to discuss the impact of click chemistry in nanosized drug delivery systems. Since the introduction of the click concept by Sharpless and coworkers in 2001, numerous examples of click reactions have been reported for the preparation and functionalization of polymeric micelles and nanoparticles, liposomes and polymersomes, capsules, microspheres, metal and silica nanoparticles, carbon nanotubes and fullerenes, or bionanoparticles. Among these click processes, Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) has attracted most attention based on its high orthogonality, reliability, and experimental simplicity for non-specialists. A renewed interest in the use of efficient classical transformations has been also observed (e.g., thiol-ene coupling, Michael addition, Diels-Alder). Special emphasis is also devoted to critically discuss the click concept, as well as practical aspects of application of CuAAC to ensure efficient and harmless bioconjugation.

Dendrimers reduce toxicity of Aß 1-28 peptide during aggregation and accelerate fibril formation.

The influence of a GATG (gallic acid-triethylene glycol) dendrimer decorated with 27 terminal morpholine groups ([G3]-Mor) on the aggregation process of Alzheimer's peptide has been investigated. Amyloid fibrils were formed from the Aß 1-28 peptide and the process was monitored by a ThT assay, changes in CD spectra, and transmission electron microscopy. In the presence of [G3]-Mor, more fibrils were built and the process significantly accelerated compared with a control. The cytotoxicity of (1) Aß and (2) the system [G3]-Mor/Aß was monitored at different stages of the aggregation process. Prefibrillar species were more toxic than mature fibrils. [G3]-Mor significantly reduced the toxicity of Aß, probably because of lowering the amount of prefibrillar forms in the system by speeding up the process of fibril formation. FROM THE CLINICAL EDITOR: In this study, GATG dendrimer decorated with 27 terminal morpholine groups was able to reduce beta-amyloid fibril formation, which might represent a new method to address the key pathology in Alzheimer's disease.

Aggregation-Induced Emission Properties in Fully π-Conjugated Polymers, Dendrimers, and Oligomers.

Aggregation-Induced Emission (AIE) in organic molecules has recently attracted the attention of the scientific community because of their potential applications in different fields. Compared to small molecules, little attention has been paid to polymers and oligomers that exhibit AIE, despite having excellent properties such as high emission efficiency in aggregate and solid states, signal amplification effect, good processability and the availability of multiple functionalization sites. In addition to these features, if the molecular structure is fully conjugated, intramolecular electronic interactions between the composing chromophores may appear, thus giving rise to a wealth of new photophysical properties. In this review, we focus on selected fully conjugated oligomers, dendrimers and polymers, and briefly summarize their synthetic routes, fluorescence properties and potential applications. An exhaustive comparison between spectroscopic results in solution and aggregates or in solid state has been collected in almost all examples, and an opinion on the future direction of the field is briefly stated.

Polyglutamic acid-based crosslinked doxorubicin nanogels as an anti-metastatic treatment for triple negative breast cancer.

Treatment of triple negative breast cancer (TNBC)-associated metastasis represents an unmet clinical need, and we lack effective therapeutics for a disease that exhibits high relapse rates and associates with poor patient outcomes. Advanced nanosized drug delivery systems may enhance the efficacy of first-line chemotherapeutics by altering drug pharmacokinetics and enhancing tumor/metastasis targeting to significantly improve efficacy and safety. Herein, we propose the application of injectable poly-amino acid-based nanogels (NGs) as a versatile hydrophilic drug delivery platform for the treatment of TNBC lung metastasis. We prepared biocompatible and biodegradable cross-linked NGs from polyglutamic acid (PGA) loaded with the chemotherapeutic agent doxorubicin (DOX). Our optimized synthetic procedures generated NGs of ~100 nm in size and 25 wt% drug loading content that became rapidly internalized in TNBC cell lines and displayed IC50 values comparable to the free form of DOX. Importantly, PGA-DOX NGs significantly inhibited lung metastases and almost completely suppressed lymph node metastases in a spontaneously metastatic orthotopic mouse TNBC model. Overall, our newly developed PGA-DOX NGs represent a potentially effective therapeutic strategy for the treatment of TNBC metastases.

Dendrimers as potential inhibitors of the dimerization of the capsid protein of HIV-1.

Assembly of the mature human immunodeficiency virus type 1 capsid involves the oligomerization of the capsid protein, CA. The C-terminal domain of CA, CTD, participates both in the formation of CA hexamers and in the joining of hexamers through homodimerization. Intact CA and the isolated CTD are able to homodimerize in solution with similar affinity (dissociation constant in the order of 10 microM); CTD homodimerization involves mainly an alpha-helical region. In this work, we show that first-generation gallic acid-triethylene glycol (GATG) dendrimers bind to CTD. The binding region is mainly formed by residues involved in the homodimerization interface of CTD. The dissociation constant of the dendrimer-CTD complexes is in the range of micromolar, as shown by ITC. Further, the affinity for CTD of some of the dendrimers is similar to that of synthetic peptides capable of binding to the dimerization region, and it is also similar to the homodimerization affinity of both CTD and CA. Moreover, one of the dendrimers, with a relatively large hydrophobic moiety at the dendritic branching (a benzoate), was able to hamper the assembly in vitro of the human immunodeficiency virus capsid. These results open the possibility of considering dendrimers as lead compounds for the development of antihuman immunodeficiency virus drugs targeting capsid assembly.

Matrix Metalloproteinase-sensitive Multistage Nanogels Promote Drug Transport in 3D Tumor Model.

Physiological barriers inside of tumor tissue often result in poor interstitial penetration and heterogeneous intratumoral distribution of nanoparticle-based drug delivery systems (DDS). Novel, matrix metalloproteinase (MMP)-sensitive peptide-crosslinked nanogels (pNGs) as multistage DDS are reported with a beneficial size reduction property to promote the process of deep tissue penetration. Methods: The presented pNGs are based on a dendritic polyglycerol (dPG) scaffold crosslinked by a modified MMP-sensitive fluorogenic peptide. The crosslinker integrates degradability in response to proteases present in the tumor microenvironment. Surfactant-free, inverse nanoprecipitation is employed to prepare the nanogels using strain-promoted click chemistry. The size and crosslinking density of the pNGs are controlled by the functionalization degree of dPG with cyclooctyne groups and by the peptide crosslinker fraction. The intrinsic reporter moiety of the crosslinker was used to study the influence of pNG compositions on the degradation profile. The therapeutic drug Doxorubicin was conjugated through a pH-sensitive linkage to dPG to form a multistage DDS. The penetration behavior of the pNGs was studied using agarose matrix and multicellular tumor spheroids (MCTS). Results: Nanogel sizes were controlled in the range of 150-650 nm with narrow size distributions and varying degrees of crosslinking. The pNGs showed stability in PBS and cell media but were readily degraded in the presence of MMP-7. The crosslinking density influenced the degradation kinetic mediated by MMP-7 or cells. Stable conjugation of DOX at physiological pH and controlled drug release at acidic pH were observed. The digestions of nanogels lead to a size reduction to polymer-drug fragments which efficiently penetrated into agarose gels. Moreover, the degradable multistage pNGs demonstrated deeper penetration into MCTS as compared to their non-degradable counterparts. Thus, degradable pNGs were able to deliver their cargo and efficiently reduce the cell viability in MCTS. Conclusion: The triggered size reduction of the pNGs by enzymatic degradation can facilitate the infiltration of the nanocarrier into dense tissue, and thereby promote the delivery of its cargo.

Synthesis and supramolecular assembly of clicked anionic dendritic polymers into polyion complex micelles.

Remarkably stable polyion complex micelles with narrow size distribution result from the supramolecular assembly of clicked anionic PEG-dendritic block copolymers with oppositely charged polymers.

Co-targeting the tumor endothelium and P-selectin-expressing glioblastoma cells leads to a remarkable therapeutic outcome.

Glioblastoma is a highly aggressive brain tumor. Current standard-of-care results in a marginal therapeutic outcome, partly due to acquirement of resistance and insufficient blood-brain barrier (BBB) penetration of chemotherapeutics. To circumvent these limitations, we conjugated the chemotherapy paclitaxel (PTX) to a dendritic polyglycerol sulfate (dPGS) nanocarrier. dPGS is able to cross the BBB, bind to P/L-selectins and accumulate selectively in intracranial tumors. We show that dPGS has dual targeting properties, as we found that P-selectin is not only expressed on tumor endothelium but also on glioblastoma cells. We delivered dPGS-PTX in combination with a peptidomimetic of the anti-angiogenic protein thrombospondin-1 (TSP-1 PM). This combination resulted in a remarkable synergistic anticancer effect on intracranial human and murine glioblastoma via induction of Fas and Fas-L, with no side effects compared to free PTX or temozolomide. This study shows that our unique therapeutic approach offers a viable alternative for the treatment of glioblastoma.

One-pot synthesis of doxorubicin-loaded multiresponsive nanogels based on hyperbranched polyglycerol.

Doxorubicin-loaded nanogels with multiresponsive properties are prepared using hyperbranched polyglycerol as a biocompatible scaffold. The nanogels are synthesized in a single step combining free-radical polymerization and a mild nanoprecipitation technique. The nanogels respond to different biological stimuli such as low pH and reductive environments, resulting in a more efficient cell proliferation inhibition in A549 cells.

In situ nanofabrication of hybrid PEG-dendritic-inorganic nanoparticles and preliminary evaluation of their biocompatibility.

An in situ template fabrication of inorganic nanoparticles using carboxylated PEG-dendritic block copolymers of the GATG family is described as a function of the dendritic block generation, the metal (Au, CdSe) and metal molar ratio. The biocompatibility of the generated nanoparticles analysed in terms of their aggregation in physiological media, cytotoxicity and uptake by macrophages relates to the PEG density of the surface of the hybrids.

Dendritic polyglycerol sulfate as a novel platform for paclitaxel delivery: pitfalls of ester linkage.

In this study, dendritic polyglycerol sulfate (dPGS) is evaluated as a delivery platform for the anticancer, tubulin-binding drug paclitaxel (PTX). The conjugation of PTX to dPGS is conducted via a labile ester linkage. A non-sulfated dendritic polyglycerol (dPG) is used as a control, and the labeling with an indocarbocyanine dye (ICC) renders multifunctional conjugates that can be monitored by fluorescence microscopy. The conjugates are characterized by (1)H NMR, UV-vis measurements, and RP-HPLC. In vitro cytotoxicity of PTX and dendritic conjugates is evaluated using A549 and A431 cell lines, showing a reduced cytotoxic efficacy of the conjugates compared to PTX. The study of uptake kinetics reveals a linear, non saturable uptake in tumor cells for dPGS-PTX-ICC, while dPG-PTX-ICC is hardly taken up. Despite the marginal uptake of dPG-PTX-ICC, it prompts tubulin polymerization to a comparable extent as PTX. These observations suggest a fast ester hydrolysis and premature drug release, as confirmed by HPLC measurements in the presence of plasma enzymes.

GATG dendrimers and PEGylated block copolymers: from synthesis to bioapplications.

Dendrimers are synthetic macromolecules composed of repetitive layers of branching units that emerge from a central core. They are characterized by a tunable size and precise number of peripheral groups which determine their physicochemical properties and function. Their high multivalency, functional surface, and globular architecture with diameters in the nanometer scale makes them ideal candidates for a wide range of applications. Gallic acid-triethylene glycol (GATG) dendrimers have attracted our attention as a promising platform in the biomedical field because of their high tunability and versatility. The presence of terminal azides in GATG dendrimers and poly(ethylene glycol) (PEG)-dendritic block copolymers allows their efficient functionalization with a variety of ligands of biomedical relevance including anionic and cationic groups, carbohydrates, peptides, or imaging agents. The resulting functionalized dendrimers have found application in drug and gene delivery, as antiviral agents and for the treatment of neurodegenerative diseases, in diagnosis and as tools to study multivalent carbohydrate recognition and dendrimer dynamics. Herein, we present an account on the preparation and recent applications of GATG dendrimers in these fields.

Polypeptides and polyaminoacids in drug delivery.

INTRODUCTION: Advances achieved over the last few years in drug delivery have provided novel and versatile possibilities for the treatment of various diseases. Among the biomaterials applied in this field, it is worth highlighting the increasing importance of polyaminoacids and polypeptides. The appealing properties of these polymers are very promising for the design of novel compositions in a variety of drug delivery applications. AREAS COVERED: This review provides an overview on the general characteristics of polyaminoacids and polypeptides and briefly discusses different synthetic pathways for their production. This is followed by a detailed description of different drug delivery applications of these polymers, emphasizing those examples that already reached advanced preclinical development or have entered clinical trials. EXPERT OPINION: Polyaminoacids and polypeptides are gaining much attention in drug delivery due to their exceptional properties. Their application as polymers for drug delivery purposes has been sped up by the significant achievements related to their synthesis. Certainly, cancer therapy has benefited the most from these advances, although other fields such as vaccine delivery and alternative administration routes are also being successfully explored. The design of new entities based on polyaminoacids and polypeptides and the improved insight gained in drug delivery guarantee exciting findings in the near future.

Exploring the efficiency of gallic acid-based dendrimers and their block copolymers with PEG as gene carriers.

The synthesis of a new family of amino-functionalized gallic acid-triethylene glycol (GATG) dendrimers and their block copolymers with polyethylene glycol (PEG) has recently being disclosed. In addition, these dendrimers have shown potential for gene delivery applications, as they efficiently complex nucleic acids and form small and homogeneous dendriplexes. On this basis, the present study aimed to explore the interaction of the engineered dendriplexes with blood components, as well as their stability, cytotoxicity and ability to enter and transfect mammalian cells. Results show that GATG dendrimers can form stable dendriplexes, protect the associated pDNA from degradation, and are biocompatible with HEK-293T cells and erythrocytes. More importantly, dendriplexes are effectively internalized by HEK-293T cells, which are successfully transfected. Besides, PEGylation has a marked influence on the properties of the resulting dendriplexes. While PEGylated GATG dendrimers have improved biocompatibility, the long PEG chains limit their uptake by HEK-293T cells, and thus, their ability to transfect them. As a consequence, the degree of PEGylation in dendriplexes containing dendrimer/block copolymer mixtures emerges as an important parameter to be modulated in order to obtain an optimized stealth formulation able to effectively induce the expression of the encoded protein.