Patricia Alves | Ecole des Ponts ParisTech (original) (raw)

Papers by Patricia Alves

11O Congresso Internacional Da Rede Unida, Apr 30, 2014

The term "biomaterial" has been defined as "a material used in a medical device intended to inter... more The term "biomaterial" has been defined as "a material used in a medical device intended to interact with biological systems". The application of natural and synthetic polymers to medical problems has increased substantially in the last twenty years. There are numerous applications of these materials in medicine, e.g. orthopaedics, dialysis, ophthalmology, surgery, cardiology and controlled delivery systems. To be used as biomaterials, the polymers need to meet certain requirements, namely their biocompatibility, bio-acceptability and biodegradability. In this case, we can consider two important groups: biostable polymers and biodegradable polymers. The main polymers used in biomedical devices are the following: polyurethanes, silicones, polyacrylates, and biodegradable polymers. In order to be used as biomaterials, the polymeric materials have to be modified either chemically or physically. In this chapter, we will give examples of modified polymers used as drug delivery systems, hydrogels and bioadhesives. Here some emphasis will be given to surface modification methods of polymeric materials. This is particularly relevant for the use of polymers in bioapplications and particularly in some of the ones described below.

Polyurethanes are one of the most versatile families of polymers. They can be prepared from a wid... more Polyurethanes are one of the most versatile families of polymers. They can be prepared from a wide variety of materials exhibiting extremely different properties and therefore, a high variety of applications. This wide range of properties has attracted the attention of biomedical devices developers. They have been testing these polymers in several biomedical fields including pacemaker lead insulation, breast implants, heart valves, vascular prostheses and bioadhesives.Throughout this review, an overview of the synthesis and properties of polyurethanes, as well as some of their biomedical applications will be presented. Since the surface properties of a material are directly related to its performance in a biological environment, a description of some of the available methods for surface modification will be carried out.The surface characteristics of a material can be adapted to a specific application by surface modification techniques, without compromising the material bulk properti...

A wound may be defined as an injury to any of the body's tissues, especially one caused by ph... more A wound may be defined as an injury to any of the body's tissues, especially one caused by physical means and with interruption of continuity. Primary wound healing of a plan-to-plan oriented scar formation is usually accomplished by hand sewing or stapling the corresponding layers of each side of the incision. Both these methods have been associated to wound infection and granule formation due to their degradation in the organism. They also present other disadvantages, such as the need to be removed (in most cases) and the pain associated with their use. As a result of these shortcomings, surgeons have thought of an alternative way: the use of medical tissue adhesives. These adhesives consist on an attractive option to suturing or stapling since they can accomplish other tasks, such as haemostasis and the ability of sealing air leakages and also because they do not represent any risk of needlestick injury to medical staff. Also, the use of an adhesive would reduce the surgeries...

Journal of Coatings Technology and Research, 2015

ABSTRACT The performance of a material in a biological environment is mediated by its surface pro... more ABSTRACT The performance of a material in a biological environment is mediated by its surface properties and by the combination of physical and mechanical properties that are required for a specific application. The more relevant surface properties in these respects include its chemical structure (hydrophilicity and the presence of functional groups that could initiate reactions in biological systems) and the morphology (the distribution and abundance of hydrophilic/hydrophobic phases, crystalline/amorphous phases and surface topographical assets). In surface modification, one aims to tailor the surface characteristics of a material towards a specific application without detrimentally affecting the bulk properties. This strategy allows to increase the success of implants application by increasing their lifetime. In this review, several approaches to the surface modification of polymers are described as are a number of viable applications.

Molecular Imaging, 2007

Gold nanoparticles exhibit intense and narrow optical extinction bands due to the phenomenon of p... more Gold nanoparticles exhibit intense and narrow optical extinction bands due to the phenomenon of plasmon resonance making them useful as contrast agents for light-based imaging techniques. Localized heating results from the absorbed light energy, which shows potential for these particles in photothermal therapy as well. The bioconjugation of gold nanoparticles to appropriate antibodies targeted to tumors in vivo, could make

Colloids and surfaces. B, Biointerfaces, 2014

The physicochemical characterization of polymer liposome complexes (PLCs) prepared with lipids of... more The physicochemical characterization of polymer liposome complexes (PLCs) prepared with lipids of lactic acid bacteria and poly(N,N-dimethylaminoethyl methacrylate) covalently bound to cholesterol (CHO-PDMAEMA) was carried out in an integrated approach, including their stability upon preservation and incorporation into eukaryotic cells. PLCs were prepared with different polymer:lipid molar ratios (0, 0.05 and 0.10). Zeta potential, particle size distribution and polydispersity index were determined. The optimal polymer:lipid ratio and the stability of both bare liposomes and PLCs were evaluated at 37 °C and at different pHs, as well as after storage at 4 °C, -80 °C and freeze-drying in the presence or absence of trehalose 250 mM. Internalization of PLCs by eukaryotic cells was assessed to give a complete picture of the system. Incorporation of CHO-PDMAEMA onto bacterial lipids (ratio 0.05 and 0.10) led to stabilization at 37 °C and pH 7. A slight decrease of pH led to their strong d...

Advanced Structured Materials, 2012

The EPMA journal, 2010

Advanced drug delivery systems (DDS) present indubitable benefits for drug administration. Over t... more Advanced drug delivery systems (DDS) present indubitable benefits for drug administration. Over the past three decades, new approaches have been suggested for the development of novel carriers for drug delivery. In this review, we describe general concepts and emerging research in this field based on multidisciplinary approaches aimed at creating personalized treatment for a broad range of highly prevalent diseases (e.g., cancer and diabetes). This review is composed of two parts. The first part provides an overview on currently available drug delivery technologies including a brief history on the development of these systems and some of the research strategies applied. The second part provides information about the most advanced drug delivery devices using stimuli-responsive polymers. Their synthesis using controlled-living radical polymerization strategy is described. In a near future it is predictable the appearance of new effective tailor-made DDS, resulting from knowledge of di...

Science and Technology of Advanced Materials, 2013

The voice is produced by the vibration of vocal cords which are located in the larynx. Therefore,... more The voice is produced by the vibration of vocal cords which are located in the larynx. Therefore, one of the major consequences for patients subjected to laryngectomy is losing their voice. In these cases, a synthetic one-way valve set (voice prosthesis) can be implanted in order to allow restoration of speech. Most voice prostheses are produced with silicone-based materials such as polydimethylsiloxane (PDMS). This material has excellent properties, such as optical transparency, chemical and biological inertness, non-toxicity, permeability to gases and excellent mechanical resistance that are fundamental for its application in the biomedical field. However, PDMS is very hydrophobic and this property causes protein adsorption which is followed by microbial adhesion and biofilm formation. To overcome these problems, surface modification of materials has been proposed in this study. A commercial silicone elastomer, Sylgard TM 184 was used to prepare membranes whose surface was modified by grafting 2-hydroxyethylmethacrylate and methacrylic acid by low-pressure plasma treatment. The hydrophilicity, hydrophobic recovery and surface energy of the produced materials were determined. Furthermore, the cytotoxicity and antibacterial activity of the materials were also assessed. The results obtained revealed that the PDMS surface modification performed did not affect the material's biocompatibility, but decreased their hydrophobic character and bacterial adhesion and growth on its surface.

Materials Science and Engineering: C, 2012

ABSTRACT The design and production of scaffolds for bone tissue regeneration is yet unable to com... more ABSTRACT The design and production of scaffolds for bone tissue regeneration is yet unable to completely reproduce the native bone properties. In the present study new alginate microparticle and microfiber aggregated scaffolds were produced to be applied in this area of regenerative medicine. The scaffolds mechanical properties were characterized by thermo mechanical assays. Their morphological characteristics were evaluated by isothermal nitrogen adsorption and scanning electron microscopy. The density of both types of scaffolds was determined by helium pycnometry and mercury intrusion porosimetry. Furthermore, scaffolds cytotoxic profiles were evaluated in vitro by seeding human osteoblast cells in their presence. The results obtained showed that scaffolds have good mechanical and morphological properties compatible with their application as bone substitutes. Moreover, scaffolds biocompatibility was confirmed by the observation of cell adhesion and proliferation after 5 days of being seeded in their presence and by non-radioactive assays.

Journal of Microencapsulation, 2008

Journal of Biomedical Materials Research Part A, 2011

Depending on the final application envisaged for a given biomaterial, many surfaces must be modif... more Depending on the final application envisaged for a given biomaterial, many surfaces must be modified before use. The material performance in a biological environment is mainly mediated by its surface properties that can be improved using suitable modification methods. The aim of this work was to coat poly(dimethyl siloxane) (PDMS) surfaces with biosurfactants (BSs) and to evaluate how these compounds affect the PDMS surface properties. BSs isolated from four probiotic strains (Lactococcus lactis, Lactobacillus paracasei, Streptococcus thermophilus A, and Streptococcus thermophilus B) were used. Bare PDMS and PDMS coated with BSs were characterized by contact angle measurements, infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The influence of the surface modifications on the materials blood compatibility was studied through thrombosis and hemolysis assays. The cytotoxicity of these materials was tested against rat peritoneal macrophages. AFM results demonstrated the successful coating of the surfaces. Also, by contact angle measurements, an increase of the coated surfaces hydrophilicity was seen. Furthermore, XPS analysis indicated a decrease of the silicon content at the surface, and ATR-FTIR results showed the presence of BS characteristic groups as a consequence of the modification. All the studied materials revealed no toxicity and were found to be nonhemolytic. The proposed approach for the modification of PDMS surfaces was found to be effective and opens new possibilities for the application of these surfaces in the biomedical field.

Journal of Applied Polymer Science, 2011

According to the gas used in the plasma treatment, plasma can by itself introduce groups at the s... more According to the gas used in the plasma treatment, plasma can by itself introduce groups at the surface or can be used to activate surface for subsequent linkage of water soluble polymer chains that are known to suppress biofouling. In this work, a commercial polyurethane was ...

International Journal of Biological Macromolecules, 2013

Gamma radiation was used as the initiator/crosslinker agent for the synthesis of thermo-sensitive... more Gamma radiation was used as the initiator/crosslinker agent for the synthesis of thermo-sensitive hydrogel networks, under the form of membranes, using dextran and N-isopropylacrylamide. The prepared membranes were loaded with Ondansetron TM , a potent antiemetic drug and tested as drug delivery systems.

International Journal of Biological Macromolecules, 2011

In the present study, small-sized porous scaffolds were obtained from the freeze-drying of sodium... more In the present study, small-sized porous scaffolds were obtained from the freeze-drying of sodium hyaluronate/chitosan polyelectrolyte complexes. The obtained materials were characterized by a set of techniques including attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, swelling determination and weight loss studies. The morphology of the scaffolds was observed using scanning electron microscopy. Thermal characterization of the scaffolds was also performed by dynamic mechanical thermal analysis and thermogravimetric analysis. Finally, the cytotoxic profile of the prepared scaffolds was evaluated in vitro, using mesenchymal stem cells. The results obtained showed that cells adhered to scaffolds and proliferated. This study also confirmed that the degradation by-products of sodium hyaluronate/chitosan scaffold are noncytotoxic, which is fundamental for its application in the biomedical field.

Conservation Genetics, 2010

Page 1. ORIGINAL PAPER Understanding the effects of isolation on seed and pollen flow, spatial ge... more Page 1. ORIGINAL PAPER Understanding the effects of isolation on seed and pollen flow, spatial genetic structure and effective population size of the dioecious tropical tree species Myracrodruon urundeuva Ana PSC Gaino ...

Colloids and Surfaces B: Biointerfaces, 2013

The development of new polymer-liposome complexes (PLCs) as delivery systems is the key issue of ... more The development of new polymer-liposome complexes (PLCs) as delivery systems is the key issue of this work. Three main areas are dealt with: polymer synthesis/characterization, liposome formulation/characterization and evaluation of the PLCs uptake by eukaryotic cells. Poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) with low molecular weight and narrow polydispersity was synthesized by Atom Transfer Radical Polymerization (ATRP). The polymers were synthesized using two different bromide initiators (cholesteryl-2-bromoisobutyrate and ethyl 2-bromoisobutyrate) as a route to afford PDMAEMA and CHO-PDMAEMA. Both synthesized polymers (PDMAEMA and CHO-PDMAEMA) were incorporated in the preparation of lecithin liposomes (LEC) to obtain PLCs. Three polymer/lipid ratios were investigated: 5, 10 and 20%. Physicochemical characterization of PLCs was carried out by determining the zeta potential, particle size distribution, and the release of fluorescent dyes (carboxyfluorescein CF and calcein) at different temperatures and pHs. The leakage experiments showed that CHO covalently bound to PDMAEMA strongly stabilizes PLCs. The incorporation of 5% CHO-PDMAEMA to LEC (LEC_CHO-PD5) appeared to be the stablest preparation at pH 7.0 and at 37°C. LEC_CHO-PD5 destabilized upon slight changes in pH and temperature, supporting the potential use of CHO-PDMAEMA incorporated to lecithin liposomes (LEC_CHO-PDs) as stimuli-responsive systems. In vitro studies on Raw 264.7 and Caco-2/TC7 cells demonstrated an efficient incorporation of PLCs into the cells. No toxicity of the prepared PLCs was observed according to 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. These results substantiate the efficiency of CHO-PDMAEMA incorporated onto LEC to assist for the release of the liposome content in mildly acidic environments, like those found in early endosomes where pH is slightly lower than the physiologic. In summary, the main achievements of this work are: (a) novel synthesis of CHO-PDMAEMA by ATRP, (b) stabilization of LEC by incorporation of CHO-PDMAEMA at neutral pH and destabilization upon slight changes of pH, (c) efficient uptake of LEC_CHO-PDs by phagocytic and non-phagocytic eukaryotic cells.

Colloids and Surfaces B: Biointerfaces, 2011

The material performance, in a biological environment, is mainly mediated by its surface properti... more The material performance, in a biological environment, is mainly mediated by its surface properties and by the combination of chemical, physical, biological, and mechanical properties required, for a specific application. In this study, the surface of a thermoplastic polyurethane (TPU) material (Elastollan(®)1180A50) was activated either by plasma or by ultra-violet (UV) irradiation. After surface activation, methacrylic acid (MAA) was linked to the surface of TPU in order to improve its reactivity and to reduce cell adhesion. Grafted surfaces were evaluated by X-ray photoelectron spectroscopy (XPS), by atomic force microscopy (AFM) and by contact angle measurements. Blood compatibility studies and cell adhesion tests with human bone marrow cells (HBMC) were also performed. If was found that UV grafting method led to better results than the plasma activation method, since cell adhesion was reduced when methacrylic acid was grafted to the TPU surface by UV.

Colloids and Surfaces B: Biointerfaces, 2010

Poly(dimethyl siloxane) elastomer, (PDMS) is widely used as a biomaterial. However, PDMS is very ... more Poly(dimethyl siloxane) elastomer, (PDMS) is widely used as a biomaterial. However, PDMS is very hydrophobic and easily colonized by several bacteria and yeasts. Consequently, surface modification has been used to improve its wettability and reduce bacterial adhesion.