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

Estado emocional del interno ante la privación de libertad

Prisionalization requires an adaptation, both physical and psychological, that the inmate in a penitentiary institution must carry out for his adaptation to the prison context since, when he is deprived of liberty, there is an extremely abrupt change in his life. Thus, many and varied are the psychological effects suffered by subjects after a time residing in a penitentiary institution. In this sense, this study aims to analyze both the effects of imprisonment arouses, fundamentally in terms of the emotional states, in the individual and the impact that this experience generates on his development. For this, an ad hoc questionnaire of own elaboration has been used, made up of 46 items (multiple choice, Likert type and dichotomous), applied to a sample (n=45) made up of subjects residing in a Social Insertion Center, that is, a center with an open regime (an intermediate state between the execution of custodial sentences and reincorporation into society) whose objective is to enhance the subject capacities for social insertion. The results reveal that, compared to an ordinary closed penitentiary, the open regime implies a more positive perspective for users, reflecting on both factors such as social support, emotional control, and also on emotional states such as perceived levels of anxiety, stress and fear.La prisionalización requiere una adaptación, tanto física como psicológica, que el interno en una institución penitenciaria debe realizar para su adecuación al contexto carcelario puesto que, al verse privado de libertad, se produce un cambio sumamente brusco en su vida. Así, muchos y variados son los efectos psicológicos que padecen los sujetos tras un periodo de tiempo residiendo en una institución penitenciaria. En tal sentido, este estudio pretende analizar los efectos de la prisionalización, fundamentalmente en cuanto a los estados emocionales que suscita en el individuo y el impacto que genera esta experiencia en su desarrollo. Para ello, se ha utilizado un cuestionario ad hoc de elaboración propia, conformado por 46 ítems (de opción múltiple, tipo Likert y dicotómicos), aplicado a una muestra (n= 45) constituida por sujetos residentes en un Centro de Inserción Social (CIS), esto es, un centro de régimen abierto, estado intermedio entre la ejecución de las penas privativas de libertad y la reincorporación a la sociedad, cuyo objetivo es potenciar las capacidades de inserción social de los sujetos. Los resultados revelan que frente a un centro penitenciario cerrado ordinario, el régimen abierto conlleva una perspectiva más positiva en los usuarios, reflejándose en factores como el apoyo social, el control emocional y en estados emocionales como los niveles percibidos de ansiedad, estrés y miedo.&nbsp

Biodegradable PEG–dendritic block copolymers: synthesis and biofunctionality assessment as vectors of siRNA

One important drawback of most of the currently used dendrimers for biomedical applications is their high stability under physiological conditions that can result in cytotoxicity or complications induced by the accumulation of non-degradable synthetic materials in the organism. Particularly in the gene therapy field, vector stability can further hinder the intracellular release of the nucleic acid from the dendriplex, consequently leading to low transfection efficiencies. Therefore, biodegradable cationic dendritic structures have been eagerly awaited. However, the development of these dendritic nanocarriers is challenging because of the undesired and/or premature degradation observed during their synthesis and/or application. Here, we report new hybrid-biodegradable, biocompatible, non-toxic, and water-soluble azide-terminated PEG–GATGE dendritic block copolymers, based on a gallic acid (GA) core and triethylene glycol (TG) butanoate arms, incorporating ester bonds (E) at the dendritic arms/shell. Their successful functionalization by “click” chemistry with unprotected alkynated amines allowed complexation and delivery of siRNA. The hydrophobic character of the GATGE building unit confers to these hydrolyzable dendritic bionanomaterials a great ability to complex, protect and mediate the cellular internalization of siRNA. Moreover, the localization of the degradation points at the dendritic periphery, close to the complexed siRNA, was found to be important for nucleic acid release from the nanoparticles, rendering a significant improvement of the transfection efficiency compared to their hydrolytically stable PEG–GATG copolymer counterparts. The present study puts forward these biodegradable PEG–dendritic block copolymers not only as suitable vectors for nucleic acids, but also as new avenues for further developments exploring their use in theranosticsThe authors would like to acknowledge the FEDER funds through the Programa Operacional Factores de Competitividade – COMPETE and the Portuguese funds through FCT – Fundação para a Ciência e a Tecnologia (PTDC/CTM-NAN/112428/2009 and PTDC/CTM-NAN/3547/2014) that supported this work and the FCT / MEC through National Funds and, when applicable, co-financed by the FEDER via the PT2020 Partnership Agreement under the 4293 Unit I&D. V. Leiro acknowledges the support by FCT (SFRH/BPD/69110/2010) and by the project NORTE-01-0145-FEDER-000012, financed by Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF). P.M.D. Moreno acknowledges the support from the Marie Curie Actions of the European Community’s Seventh Framework Program (PIEF-GA-2011-300485) and FCT fellowship (SFRH/BPD/108738/2015). This work was also financially supported by the Spanish Government (MINECO: CTQ2012-34790, CTQ2012-33436) 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

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

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

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

O106 / #796 FEASIBILITY OF TRANSCUTANEOUS SPINAL CORD STIMULATION COMBINED WITH ROBOTIC-ASSISTED GAIT TRAINING (LOKOMAT) FOR GAIT REHABILITATION FOLLOWING INCOMPLETE SPINAL CORD INJURY. A CASE SERIES STUDY

Transcutaneous electrical spinal cord stimulation (tSCS) is a non-invasive technique for neuromodulation with therapeutic potential for motor rehabilitation following spinal cord injury (SCI). The aim of the present study was to analyze the feasibility of a program of 20 sessions of 30-Hz tSCS combined with robotic-assisted gait training in incomplete SCI. The results of the present work partially belong to a randomized clinical trial that is in progress