Click Chemistry for Drug Delivery Nanosystems

This is a post-peer-review, pre-copyedit version of an article published in Pharmaceutical Research. The final authenticated version is available online at: https://doi.org/10.1007/s11095-011-0568-5The 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 bioconjugationThis work was financially supported by the Spanish Ministry of Science and Innovation (CTQ2009-10963 and CTQ2009-14146-C02-02) and the Xunta de Galicia (10CSA209021PR)S

PEG-dendritic block copolymers for biomedical applications

The incorporation of poly(ethylene glycol) (PEG) chains at the focal point of dendrimers results in customizable platforms where the careful selection of the PEG length, the nature of the peripheral groups, and the structure and generation of the dendritic block entail materials for specific applications in the biomedical field. In this focus article, the synthesis, properties, and biomedical applications of PEG-dendritic block copolymers are discussed with examples in drug and gene delivery, tissue repair, and diagnosisThis work was financially supported by the Spanish MICINN (CTQ2009-10963 and CTQ2009-14146-C02-02) and the Xunta de Galicia (10CSA209021PR and CN2011/037).S

GATG Dendrimers and PEGylated Block Copolymers: from Synthesis to Bioapplications

This is a post-peer-review, pre-copyedit version of an article published in The AAPS Journal. The final authenticated version is available online at: https://doi.org/10.1208/s12248-014-9642-3Dendrimers 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 fieldsThe authors wish to acknowledge past and present lab members who have contributed to the development of dendrimers in our group. This work was financially supported by the Spanish Government (CTQ2009-10963, CTQ2012-34790, CTQ2009-14146-C02-02, CTQ2012-33436) and the Xunta de Galicia (10CSA209021PR and CN2011/037)S

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 hybridsC.S.E. and A.G.-F. thank to the European Commission BIOCAPS (316265, FP7/REGPOT-2012-2013.1) and Xunta de Galicia (Agrupamento INBIOMED and Grupo con potencial crecimiento). A.S.-H. and E.F.-M. thank the Spanish Government (CTQ2012-34790) and the Xunta de Galicia (CN2011/037)S

The Effect of PEGylation on Multivalent Binding: A Surface Plasmon Resonance and Isothermal Titration Calorimetry Study with Structurally Diverse PEG‐Dendritic GATG Copolymers

This is the peer-reviewed version of the following article: Fernandez-Villamarin, M., Sousa-Herves, A., Correa, J., Munoz, E., Taboada, P., Riguera, R., & Fernandez-Megia, E. (2016). The Effect of PEGylation on Multivalent Binding: A Surface Plasmon Resonance and Isothermal Titration Calorimetry Study with Structurally Diverse PEG-Dendritic GATG Copolymers. Chemnanomat, 2(5), 437-446, which has been published in final form at https://doi.org/10.1002/cnma.201600008. This article may be used for non-commercial purposes in accordance with Wiley-VCH Terms and Conditions for Self-ArchivingA general synthetic strategy to polyethylene glycol (PEG)‐dendritic block copolymers of the GATG (gallic acid–triethylene glycol) family is described from commercially available PEG of different molecular weights and architectures. Glycosylation of the resulting azide‐terminated copolymers with fucose by copper‐catalyzed azide–alkyne cycloaddition (CuAAC) afforded a toolbox to study the effect of PEG on the multivalent binding with the lectin UEA‐I by surface plasmon resonance (SPR, on surface) and isothermal titration calorimetry (ITC, in solution). Our results indicate that PEG reduces the affinity of glycodendrimers towards lectins by steric hindrance in a molecular‐weight‐dependent fashion. Great differences were observed as a function of the PEG architecture, with diblock PEG‐dendritic copolymers benefiting from a positive entropic contribution (PEG folding), not seen in the dendritic‐PEG‐dendritic systems. The self‐inflicted steric stabilization of the PEGylated copolymers onto lectin clusters reveals the necessity of additional competitive experiments to fully assess the antiadhesive properties of PEG in biological environmentsSpanish Government. Grant Numbers: CTQ2015-69021-R, CTQ2012-34790, CTQ2014-61470-EXP Xunta de Galicia. Grant Number: GRC2014/040S

A dendrimer–hydrophobic interaction synergy improves the stability of polyion complex micelles

This work was financially supported by the Spanish Ministry of Economy, Industry and Competitiveness (MINECO) (CTQ2015‐ 69021‐R), the Consellería de Cultura, Educación e Ordenación Universitaria (GRC2014/040 and Centro Singular de Investigación de Galicia Accreditation 2016‐2019, ED431G/09), and the European Regional Development Fund (ERDF). M.F.‐V. thanks the Spanish Government for a FPU FellowshipPolyion complex (PIC) micelles incorporating PEG-dendritic copolymers display an unprecedented stability towards ionic strength that is amplified via hydrophobic interactions. The tridimensional orientation of peripheral hydrophobic linkers between charged groups and the globular/rigid dendritic scaffold maximizes this stabilization compared to PIC micelles from linear polymers. As a result, micelles stable at concentrations higher than 3 M NaCl are obtained, which represents the highest saline concentration attained with PIC micelles. Advantages of this stabilizing dendritic effect have been taken for the design of a robust, pH-sensitive micelle for the controlled intracellular release of the anticancer drug doxorubicin. This micelle displays a slightly higher toxicity, and distinctive mechanisms of cell uptake and intracellular trafficking relative to the free drug. The preparation of mixed PIC micelles by combining differently functionalized PEG-dendritic block copolymers has allowed the fine-tuning of their stability, paving the way towards the facile modulation of properties like biodegradability, drug loading, or the response to external stimuliS

Dendrimers reduce toxicity of Aβ 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 Aβ 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) Aβ and (2) the system [G3]-Mor/Aβ was monitored at different stages of the aggregation process. Prefibrillar species were more toxic than mature fibrils. [G3]-Mor significantly reduced the toxicity of Aβ, probably because of lowering the amount of prefibrillar forms in the system by speeding up the process of fibril formationThis work was funded by the project “Biological Properties and Biomedical Applications of Dendrimers” operated within Foundation for Polish Science TEAM programme, cofinanced by the European Regional Development Fund. Financial support is also acknowledged from the Spanish MICINN (CTQ2009-10963 and CTQ2009-14146-C02-02) and the Xunta de Galicia (10CSA209021PR and CN2011/037). M.F-V. thanks the Spanish Ministry of Education for a FPU fellowship. The research was performed within the frame of the COST Action TD0802 “Dendrimers for biomedical applications.”S

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 proteinThe authors gratefully acknowledge support from the Spanish Ministry of Science and Innovation (SAF2004‐09230‐004‐01, CTQ2006‐12222/BQU, and CTQ2009‐10963) and the Xunta de Galicia (10CSA209021PR). M. Raviña and A. Sousa‐Herves also acknowledge fellowships from the Spanish Government (FPI and FPU, respectively)S

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

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