Alexandra Muñoz-Bonilla

Hybrid materials achieved by polypeptide grafted magnetite nanoparticles through a dopamine biomimetic surface anchored initiator

Herein we report the preparation of well-defined hybrid materials based on magnetite nanoparticles coated with a polypeptide shell attached covalently through dopamine. Highly crystalline and hydrophobic magnetite nanoparticles have been modified at the surface using a biomimetic adhesive, dopamine, which provides the magnetite particles with primary amine groups. Hybrid magnetite–polypeptide systems have been, then, obtained by ring opening polymerization (ROP) of γ-benzyl-L-glutamate N-carboxyanhydride. These core–shell nanoparticles, magnetite–polypeptide, constitute an interesting alternative to other magnetite–polymer structures (PEG or dextran) because they present the following advantages: (1) the stability provided by a polypeptide shell covalently bonded to the magnetite surface through a dopamine anchor molecule instead of other non-covalent interactions; (2) the posterior chain deprotection of a poly(γ-benzyl-L-glutamate) (PBLG) shell transforms the system into magnetite–poly(glutamic acid) nanoparticles (PLGA), with high stability in aqueous solutions and a large amount of carboxylic acid groups; and (3) the easiness to incorporate compounds with biological activity into the PBLG structure, for instance, by loading procaine by aminolysis reaction. Therefore, the magnetite–PBLG nanoparticles depicted herein can be potentially employed as magnetic drug carriers or as scaffolds to engineer more complex hybrid materials. The structure and composition of these systems have been extensively characterized.

Biodegradable Polycaprolactone-Titania Nanocomposites: Preparation, Characterization and Antimicrobial Properties

Nanocomposites obtained from the incorporation of synthesized TiO2 nanoparticles (≈10 nm average primary particle size) in different amounts, ranging from 0.5 to 5 wt.%, into a biodegradable polycaprolactone matrix are achieved via a straightforward and commercial melting processing. The resulting nanocomposites have been structurally and thermally characterized by transmission electron microscopy (TEM), wide/small angle X-ray diffraction (WAXS/SAXS, respectively) and differential scanning calorimetry (DSC). TEM evaluation provides evidence of an excellent nanometric dispersion of the oxide component in the polymeric matrix, with aggregates having an average size well below 100 nm. Presence of these TiO2 nanoparticles induces a nucleant effect during polymer crystallization. Moreover, the antimicrobial activity of nanocomposites has been tested using both UV and visible light against Gram-negative Escherichia coli bacteria and Gram-positive Staphylococcus aureus. The bactericidal behavior has been explained through the analysis of the material optical properties, with a key role played by the creation of new electronic states within the polymer-based nanocomposites.

Control of the chemistry outside the pores in honeycomb patterned films

We report the selective functionalization of the external surface in honeycomb structured porous films while maintaining the functionality of the pores. For this purpose, we describe the preparation of polymer films from blends of polystyrene (PS) and polystyrene-b-poly(2,3,4,5,6-pentafluorostyrene) (PS-b-P5FS) by the breath figures approach. The diblock copolymer resulted to be homogeneously distributed along the whole surface of the films as a consequence of the reorientation towards the solution–air interface. The porous films obtained have a wetting behavior that can be described by the Cassie–Baxter state equations. This particular effect allowed us to modify the chemical composition of the film surface whilst the interior of the pores does not vary. As a proof of concept, we report the modification of the surface using “click” chemistry. Thiolated glucose molecules were attached specifically to the poly(2,3,4,5,6-pentafluorostyrene) domains via thiol-para fluorine “click” reaction. The kinetics of this reaction and the possibility to participate in recognition processes have been evaluated by contact angle measurements, X-ray photoelectron spectroscopy and fluorescence microscopy.

Glycoparticles and bioactive films prepared by emulsion polymerization using a well-defined block glycopolymer stabilizer

A well-defined amphiphilic diblock glycopolymer of poly(2-{[(D-glucosamin-2-N-yl)carbonyl]oxy}ethyl methacrylate)-b-poly(butyl methacrylate) (PHEMAGl-b-PBMA) was synthesized via atom transfer radical polymerization (ATRP). Due to its capability to form micelles in aqueous solution, the obtained block glycopolymer was used as polymeric surfactant in the emulsion polymerization of butyl methacrylate in order to prepare glycosylated polymer particles. Core–shell particles consisting of a soft core of poly(butyl methacrylate) covered with glycopolymer bearing glucose moieties were obtained. Then these latex particles were employed to prepare polymer films with active surface. The surface bioactivity of this polymer coating was examined using the specific lectin Concanavalin A, Canavalia ensiformis. The specific and successful binding to the Concanavalin A was demonstrated by both fluorescence microscopy and spectroscopy being more intense with increasing concentration of block glycopolymer surfactant. The good accessibility of the glucose moieties at the surface of the coating makes this method a powerful tool to achieve potential materials for biomedical applications involving molecular recognition processes.

Synthesis and lectin recognition studies of glycosylated polystyrene microspheres functionalized via thiol–para-fluorine “click” reaction

The preparation of cross-linked polymeric micrometer sized particles of styrene and pentafluorostyrene functionalized at the surface with carbohydrate moieties is described. The particles were synthesized via precipitation polymerization consisting of the radical copolymerization of pentafluorostyrene, styrene and divinylbenzene. The amount of divinylbenzene is maintained constant for all the experiments whereas the proportion of the styrene and pentafluorostyrene was varied. Therefore, different fluorinated particles with high cross-linking density were obtained where the content of the active para-fluorine groups varies accordingly with the feed composition. Afterwards, the carbohydrate moieties were attached to the particles in two steps by the so-called thiol–para-fluorine “click” reaction based on the coupling of acetylated β-D-thioglucopyranose onto pentafluorostyrene via a nucleophilic substitution of para-fluorine, followed by the deprotection of the acetate-protected thioglucose. The obtained glycoparticles were characterized by infrared spectroscopy and contact angle measurements, which confirmed the increasing amount of the glucose moieties in the particles as the composition of the feed on pentafluorostyrene comonomer increases. The synthesized glucose-modified particles are packed into cartridges and their binding abilities with specific proteins, such as Concanavalin A, are subsequently tested. Fluorescence spectroscopy and microscopy experiments evidenced that the glycoparticles packed into the columns are able to retain specifically Concanavalin A. Other proteins such as bovine serum albumin were tested and did not interact with the particle surface.

Preparation of amphiphilic glycopolymers with flexible long side chain and their use as stabilizer for emulsion polymerization.

A glycomonomer was synthesized from poly(ethylene glycol) methacrylate (PEGMA). The terminal hydroxyl moieties were activated with ester groups and subsequently the glucosamine was incorporated forming urethane linkages. The obtained glycomonomer was copolymerized with methyl acrylate by free radical polymerization varying the initial feed composition to produce different amphiphilic glycopolymers. The glycopolymers were then characterized and compared with the homologous glycopolymers based on 2-{[(D-glucosamin-2-N-yl)carbonyl]oxy}ethyl methacrylate. Both series of glycopolymers were used in emulsion polymerization of methyl acrylate as stabilizers without the addition of any cosurfactant. Although high conversions were not achieved with any of the employed surfactant, the glycopolymers provide good colloidal stability, spherical, monodisperse and small latex particles in comparison with the surfactant-free emulsion polymerization. The latex particles stabilized with the glycosurfactant based on PEGMA, containing a flexible spacer between the backbone and the glucosamine, lead to smooth films whereas the short side chain surfactant from 2-hydroxyethyl methacrylate (HEMA), with higher glass transition temperature, restricts the coalescence of particles and, therefore, the film formation. Moreover, the surface bioactivity of these polymer coatings was examined by analyzing their specific interaction with the lectin, Concanavalin A, Canavalia ensiformis. The specific and successful binding to the Concanavalin A was demonstrated by fluorescence microscopy for both series being more intense with increasing amount of glycounits in the glycopolymer stabilizers. Interestingly, the incorporation of a flexible spacer in the glycopolymer structures enhances the binding activity.

Surface modification of magnetite hybrid particles with carbohydrates and gold nanoparticles via “click” chemistry

An efficient method is described to synthesize magnetic particles based on divinylbenzene-co-pentafluorostyrene suitable for further chemical modification and incorporation of active groups, in particular, carbohydrates and gold nanoparticles. The magnetic hybrid particles were prepared via seeded precipitation polymerization consisting of the radical copolymerization of pentafluorostyrene and divinylbenzene in the presence of modified magnetite nanoparticles as seeds. Magnetite nanoparticles were first prepared by a thermal decomposition process followed by their modification with the bioinspired dopamine methacrylamide to incorporate vinyl groups at the particle surface. Then, pentafluorostyrene and divinylbenzene are polymerized through the interface of the magnetite nanoparticles to form the crosslinked polymeric shell. Afterwards, carbohydrate moieties were attached to the particles by the so-called thiol-para-fluorine “click” reaction based on the coupling of acetylated β-D-thioglucopyranose onto pentafluorostyrene via nucleophilic substitution of para-fluorine. Moreover, the fluorinated hybrid particles reacted with 1,2-ethanedithiol in order to introduce thiol groups at the surface that were used further as platforms to stabilize the nucleation and growth of gold nanoparticles. The resultant functional particles with potential interest in recognition processes and catalysis amongst others are responsive to external magnetic fields, making the particles easy to remove from the media.

Amphiphilic polymers bearing gluconolactone moieties: synthesis and long side-chain crystalline behavior.

The synthesis and characterization of amphiphilic polymers bearing gluconolactone moieties has been described. In a first step, an unprotected glycomonomer 2-[({[4-(d-gluconamid-N-yl)butyl]amino}carbonyl)oxy]ethyl acrylate, HEAG, has been synthesized. Posterior, this glycomonomer has been copolymerized with methyl methacrylate at different compositions and the kinetic behavior has been also studied calculating the monomer reactivity ratios by Kelen-Tüdös extended equation. In addition, the long side-chain crystalline behavior of these carbohydrate-based copolymers with high composition of glycomonomer has been examined by using conventional and modulated differential scanning calorimetry and X-ray diffraction measurements. At the same time, the phase separation behavior of carbohydrate-based copolymers with lower HEAG content has been determined by their glass transition temperature measurements. Finally, the thermal stability of all these amphiphilic copolymers has been evaluated by thermogravimetric analysis.

Honeycomb structured porous interfaces as templates for protein adhesion

We prepared breath figure patterns decorated with a statistical glycopolymer, (styrene-co-2-{[(D-glucosamin-2-N-yl)carbonyl]oxy}ethyl methacrylate, S-HEMAGl). The preparation of the glycopolymer occurs in one single step by using styrene and S-HEMAGl. Blends of this copolymer and high molecular weight polystyrene were spin coated from THF solutions leading to the formation of surfaces with both controlled functionality and topography. AFM studies revealed that both the composition of the blend and the relative humidity play a key role on the size and distribution of the pores at the interface. The porous films shows the hydrophilic glycomonomer units are oriented towards the pore interface since upon soft annealing in water, the holes are partially swelled. The self-organization of the glycopolymer within the pores was additionally confirmed both by reaction of carbohydrate hydroxyl groups with rhodamine-isocyanate and by means of the lectin binding test using Concanavalin A (Con A).