Mariacristina Gagliardi

Surface functionalisation regulates polyamidoamine dendrimer toxicity on blood–brain barrier cells and the modulation of key inflammatory receptors on microglia

Abstract Dendrimers are branched polymers with spherical morphology. Their tuneable chemistry and surface modification make them valuable nanomaterials for biomedical applications. In view of possible dendrimer uses as brain-aimed nanocarriers, the authors studied amine- and lipid-functionalised (G4) polyamidoamine (PAMAM) biocompatibility with cell population forming the blood–brain barrier (BBB). Both amine-PAMAM and lipid-PAMAM dendrimers were able to enter endothelial and primary neural cells. However, only amine-PAMAM damaged cell membranes in a dose-dependent manner. Transmission electron microscopy evidenced the ability of dendrimers to precipitate salts and serum components present in culture medium that slightly increased toxicity of the amine-PAMAM. Amine- and lipid-PAMAM were both able to cross the BBB and differently induced CD11b and CCR2 overexpression on primary CX3CR1-GFP murine microglia in vitro. These data emphasise the role of dendrimer surface functionalisation in toxicity and neural immune cell activation, raising concerns about possible neuroinflammatory reactions.

The effect of bioartificial constructs that mimic myocardial structure and biomechanical properties on stem cell commitment towards cardiac lineage

Despite the enormous progress in the treatment of coronary artery diseases, they remain the most common cause of heart failure in the Western countries. New translational therapeutic approaches explore cardiomyogenic differentiation of various types of stem cells in combination with tissue-engineered scaffolds. In this study we fabricated PHBHV/gelatin constructs mimicking myocardial structural properties. Chemical structure and molecular interaction between material components induced specific properties to the substrate in terms of hydrophilicity degree, porosity and mechanical characteristics. Viability and proliferation assays demonstrated that these constructs allow adhesion and growth of mesenchymal stem cells (MSCs) and cardiac resident non myocytic cells (NMCs). Immunofluorescence analysis demonstrated that stem cells cultured on these constructs adopt a distribution mimicking the three-dimensional cell alignment of myocardium. qPCR and immunofluorescence analyses showed the ability of this construct to direct initial MSC and NMC lineage specification towards cardiomyogenesis: both MSCs and NMCs showed the expression of the cardiac transcription factor GATA-4, fundamental for early cardiac commitment. Moreover NMCs also acquired the expression of the cardiac transcription factors Nkx2.5 and TBX5 and produced sarcomeric proteins. This work may represent a new approach to induce both resident and non-resident stem cells to cardiac commitment in a 3-D structure, without using additional stimuli.

Combined drug release from biodegradable bilayer coating for endovascular stents.

In this work, the characterization of a biodegradable bilayer system, used as controlled and combined drug delivery platform, is reported. For this aim, a bilayer system, composed of poly(lactic-co-glycolic acid) and poly(3-hydroxybutyric-co-3-hydroxyvaleric acid), was investigated under physicochemical and functional aspects by evaluating polymer/polymer and polymer/stent material interactions, the kinetic of in vitro degradation, and drug release properties, comparing results with the monolayer reference systems. Obtained results showed that the bilayer system allowed increasing the total amount of eluted Tacrolimus and Paclitaxel drugs with respect to the monolayer systems in the considered testing period and conditions. This evidence was associated to a faster degradation of the tested copolymers in the bilayered configuration, excluding a synergic effect of two drugs on delivery performance. In addition, a macromolecular relaxation process was identified to govern the PLX release from poly(lactic-co-glycolic acid), whereas a pure Fickian diffusion occurred in the delivery of Tacrolimus from poly(3-hydroxybutyric-co-3-hydroxyvaleric acid).

Chitosan-Based Macromolecular Biomaterials for the Regeneration of Chondroskeletal and Nerve Tissue

The use of materials, containing the biocompatible and bioresorbable biopolymer poly()-2-amino-2-deoxy--D-glucan, containing some N-acetyl-glucosamine units (chitosan, CHI) and/or its derivatives, to fabricate devices for the regeneration of bone, cartilage and nerve tissue, was reviewed. The CHI-containing devices, to be used for bone and cartilage regeneration and healing, were tested mainly for in vitro cell adhesion and proliferation and for insertion into animals; only the use of CHI in dental surgery has reached the clinical application. Regarding the nerve tissue, only a surgical repair of a 35 mm-long nerve defect in the median nerve of the right arm at elbow level with an artificial nerve graft, comprising an outer microporous conduit of CHI and internal oriented filaments of poly(glycolic acid), was reported. As a consequence, although many positive results have been obtained, much work must still be made, especially for the passage from the experimentation of the CHI-based devices, in vitro and in animals, to their clinical application.

Novel biodegradable, biomimetic and functionalised polymer scaffolds to prevent expansion of post-infarct left ventricular remodelling

Over the past decade, a large number of strategies and technologies have been developed to reduce heart failure progression. Among these, cardiac tissue engineering is one of the most promising. Aim of this study is to develop a 3D scaffold to treat cardiac failure. A new three-block copolymer, obtained from δ-valerolactone and polyoxyethylene, was synthesised under high vacuum without catalyst. Copolymer/gelatine blends were microfabricated to obtain a ECM-like geometry. Structures were studied under morphological, mechanical, degradation and biological aspects. To prevent left ventricular remodelling, constructs were biofunctionalises with molecularly imprinted nanoparticles towards the matrix metalloproteinase MMP-9. Results showed that materials are able to reproduce the ECM structure with high resolution, mechanical properties were in the order of MPa similar to those of the native myocardium and cell viability was verified. Nanoparticles showed the capability to rebind MMP-9 (specific rebinding 18.67) and to be permanently immobilised on the scaffold surface.

Macromolecular composition and drug-loading effect on the delivery of paclitaxel and folic acid from acrylic matrices

Drug delivery systems based on synthetic polymers are widely employed in the treatment of several pathologies. In particular, the use of implantable devices able to release one or more active principles in a topic site with a controlled delivery kinetic represents an important improvement in this field. However, the release kinetic, that could be affected by different parameters, like polymer composition or chemical nature and initial drug loading, represents one of the problems related to the implantation of delivery systems. In this study, acrylic membranes with different macromolecular composition were prepared and studied analyzing delivery kinetic properties. Drug delivery systems were prepared using as matrix the copolymer poly(methylmethacrylate-co-butylmethacrylate) in three different compositions and folic acid (less hydrophobic) or Paclitaxel (more hydrophobic) as drugs, to evaluate the effect of macromolecular composition and hydrophilicity degree on the release properties. In addition, the effect of the initial drug loading was considered, loading drug delivery systems with four different initial drug percentages. Results showed a direct dependence of kinetics from macromolecular composition, hydrophilicity degree of solutes, and initial drug loading, allowing one to conclude that it is possible to design and to develop drug delivery systems starting from poly(methylmethacrylate-co-butylmethacrylate) matrices with specific properties by varying these three parameters.

Chemical synthesis of a biodegradable PEGylated copolymer from ε-caprolactone and γ-valerolactone: evaluation of reaction and functional properties

This paper reports the chemical synthesis of methoxy poly(ethyleneglycol)-block-poly(ε-caprolactone-co-4-hydroxyvalerate) from ε-caprolactone and γ-valerolactone, a five-membered ring rarely used in chemical synthesis due to its low reactivity. This procedure enabled production of copolymers with controlled ratios of repeating units and molecular weights, as demonstrated by GPC, FT-IR and NMR characterization. Copolymer degradation rate was found to depend on macromolecular composition, and finely tuneable in a wide range of values. Similarly, hydrophilicity was dependent on γ-valerolactone content, and could be accurately controlled by varying the composition of the reaction feed. Importantly, this copolymer showed lower levels of acidic degradation products than other biodegradable polymers, thus resulting in improved biocompatibility. These encouraging results demonstrate the feasibility of the chemical synthesis of a novel and versatile material with interesting properties that fill a gap in the range of commercially available biodegradable polymers.

Micro- and Macrostructured PLGA/Gelatin Scaffolds Promote Early Cardiogenic Commitment of Human Mesenchymal Stem Cells In Vitro

The biomaterial scaffold plays a key role in most tissue engineering strategies. Its surface properties, micropatterning, degradation, and mechanical features affect not only the generation of the tissue construct in vitro, but also its in vivo functionality. The area of myocardial tissue engineering still faces significant difficulties and challenges in the design of bioactive scaffolds, which allow composition variation to accommodate divergence in the evolving myocardial structure. Here we aimed at verifying if a microstructured bioartificial scaffold alone can provoke an effect on stem cell behavior. To this purpose, we fabricated microstructured bioartificial polymeric constructs made of PLGA/gelatin mimicking anisotropic structure and mechanical properties of the myocardium. We found that PLGA/gelatin scaffolds promoted adhesion, elongation, ordered disposition, and early myocardial commitment of human mesenchymal stem cells suggesting that these constructs are able to crosstalk with stem cells in a precise and controlled manner. At the same time, the biomaterial degradation kinetics renders the PLGA/gelatin constructs very attractive for myocardial regeneration approaches.

A poly(ether-ester) copolymer for the preparation of nanocarriers with improved degradation and drug delivery kinetics

This paper reports the synthesis and the physicochemical, functional and biological characterisations of nanocarriers made of a novel di-block biodegradable poly(ether-ester) copolymer. This material presents tunable, fast biodegradation rates, but its products are less acidic than those of other biosorbable polymers like PLGA, thus presenting a better biocompatibility profile and the possibility to carry pH-sensitive payloads. A method for the production of monodisperse and spherical nanoparticles is proposed; drug delivery kinetics and blood protein adsorption were measured to evaluate the functional properties of these nanoparticles as drug carriers. The copolymer was labelled with a fluorescent dye for internalisation tests, and rhodamine B was used as a model cargo to study transport and release inside cultured cells. Biological tests demonstrated good cytocompatibility, significant cell internalisation and the possibility to vehiculate non-cell penetrating moieties into endothelial cells. Taken together, these results support the potential use of this nanoparticulate system for systemic administration of drugs.

Acrylic copolymers as candidates for drug-eluting coating of vascular stents.

The aim of the present work is the synthesis and characterization of polymer materials showing good adhesion, drug loading, and delivery properties, for potential cardiovascular application. In particular, poly(methylmethacrylate-co-acrylic acid) copolymers are prepared in different compositions by a radical polymerization and investigated as potential materials to coat metallic stents and to carry out a local drug release. Films obtained by dissolving the copolymer in an appropriate organic solvent (also loaded with an anti-restenosis drug, such as tacrolimus) are investigated: physicochemical properties, adhesiveness to metallic stent material, and kinetics of drug release in physiological environment are studied.