Development of photo-crosslinkable collagen hydrogel building blocks for vascular tissue engineering applications: A superior alternative to methacrylated gelatin?

The present work targets the development of collagen-based hydrogel precursors, functionalized with photo-crosslinkable methacrylamide moieties (COL-MA), for vascular tissue engineering (vTE) applications. The developed materials were physico-chemically characterized in terms of crosslinking kinetics, degree of modification/conversion, swelling behavior, mechanical properties and in vitro cytocompatibility. The collagen derivatives were benchmarked to methacrylamide-modified gelatin (GEL-MA), due to its proven track record in the field of tissue engineering.

Heparin-Modified Collagen Gels for Controlled Release of Pleiotrophin: Potential for Vascular Applications.

A fast re-endothelialization, along with the inhibition of neointima hyperplasia, are crucial to reduce the failure of vascular bypass grafts. Implants modifications with molecules capable of speeding up the re-endothelialization process have been proposed over the last years. However, clinical trials of angiogenic factor delivery have been mostly disappointing, underscoring the need to investigate a wider array of angiogenic factors.

Fibronectin promotes elastin deposition, elasticity and mechanical strength in cellularised collagen-based scaffolds.

One of the tightest bottlenecks in vascular tissue engineering (vTE) is the lack of strength and elasticity of engineered vascular wall models caused by limited elastic fiber deposition. In this study, flat and tubular collagen gel-based scaffolds were cellularised with vascular smooth muscle cells (SMCs) and supplemented with human plasma fibronectin (FN), a known master organizer of several extracellular matrix (ECM) fiber systems. The consequences of FN on construct maturation was investigated in terms of geometrical contraction, viscoelastic mechanical properties and deposition of core elastic fiber proteins.

Increasing Cell Seeding Density Improves Elastin Expression and Mechanical Properties in Collagen Gel-Based Scaffolds Cellularized with Smooth Muscle Cells.

Vascular tissue engineering combines cells with scaffold materials in vitro aiming the development of physiologically relevant vascular models. For natural scaffolds such as collagen gels, where cells can be mixed with the material solution before gelation, cell seeding density is a key parameter that can affect extracellular matrix deposition and remodeling. Nonetheless, this parameter is often overlooked and densities sensitively lower than those of native tissues, are usually employed.

Antibacterial Coatings Based on Chitosan for Pharmaceutical and Biomedical Applications.

The risk of bacterial colonization of abiotic surfaces of biomedical devices poses important challenges for the pharmaceutical and biomaterials science fields. In this scenario, antibacterial coatings have been developed, using a number of different molecules and materials. Among them, chitosan is a non-cytotoxic, biocompatible biopolymer with an inherent antimicrobial activity that has been already used in a wide variety of healthcare and industrial applications.

A Cost-Effective Culture System for the In Vitro Assembly, Maturation, and Stimulation of Advanced Multilayered Multiculture Tubular Tissue Models.

The development of tubular engineered tissues is a challenging research area aiming to provide tissue substitutes but also in vitro models to test drugs, medical devices, and even to study physiological and pathological processes. In this work, the design, fabrication, and validation of an original cost-effective tubular multilayered-tissue culture system (TMCS) are reported. By exploiting cellularized collagen gel as scaffold, a simple moulding technique and an endothelialization step on a rotating system, TMCS allowed to easily prepare in 48 h, trilayered arterial wall models with finely organized cellular composition and to mature them for 2 weeks without any need of manipulation.

Cellularizing hydrogel-based scaffolds to repair bone tissue: How to create a physiologically relevant micro-environment?

Tissue engineering is a promising alternative to autografts or allografts for the regeneration of large bone defects. Cell-free biomaterials with different degrees of sophistication can be used for several therapeutic indications, to stimulate bone repair by the host tissue. However, when osteoprogenitors are not available in the damaged tissue, exogenous cells with an osteoblast differentiation potential must be provided.

Biomimetic coating of cross-linked gelatin to improve mechanical and biological properties of electrospun PET: A promising approach for small caliber vascular graft applications.

Electrospun PET (ePET) is a promising material for small caliber vascular graft applications owing to its tunable mechanical properties, biocompatibility, and nanofibrous structure that mimic the morphology of natural extracellular matrix. However, the inherent inertness of PET impairs the adhesion and proliferation of endothelial cells on the inner surface of ePET tubular grafts, hindering the formation of a functional endothelium. Gelatin coatings, owing to their ability to promote endothelialization, are a valuable approach to overcome the limitations of ePET.

Size matters for in vitro gene delivery: investigating the relationships among complexation protocol, transfection medium, size and sedimentation.

Although branched and linear polyethylenimines (bPEIs and lPEIs) are gold standard transfectants, a systematic analysis of the effects of the preparation protocol of polyplexes and the composition of the transfection medium on their physicochemical behaviour and effectiveness in vitro have been much neglected, undermining in some way the identification of precise structure-function relationships. This work aimed to address these issues. bPEI/DNA and lPEI/DNA, prepared using two different modes of addition of reagents, gave rise to polyplexes with exactly the same chemical composition but differing in dimensions.

A planar model of the vessel wall from cellularized-collagen scaffolds: focus on cell-matrix interactions in mono-, bi- and tri-culture models.

The acquisition of new thorough knowledge on the interactions existing between vascular cells would represent a step forward in the engineering of vascular tissues. In this light, herein we designed a physiological-like tri-culture in vitro vascular wall model using a planar cellularized collagen gel as the scaffold. The model can be obtained in 24 h and features multi-layered hierarchical organization composed of a fibroblast-containing adventitia-like layer, a media-like layer populated by smooth muscle cells and an intima-like endothelial cell monolayer.

Characterization and Investigation of Redox-Sensitive Liposomes for Gene Delivery.

A number of smart nonviral gene delivery vectors relying on bioresponsiveness have been introduced in the past few years to overcome the limits of the first generation of gene carriers. Among them, redox-sensitive lipidic and polymeric vectors exploit the presence of disulfide bonds in their structure to take advantage of the highly reductive intracellular milieu and to promote complex unpacking and nucleic acids release after cellular uptake (disulfide linker strategy). Glutathione (GSH) has been often identified as the leading actor in the intracellular reduction of bioreducible vectors but their actual mechanisms of action have been rarely investigated in depth and doubts about the real effectiveness of the disulfide linker strategy have been raised.

Unraveling the role of mechanical stimulation on smooth muscle cells: A comparative study between 2D and 3D models.

A thorough understanding of cell response to combined culture configuration and mechanical cues is of paramount importance in vascular tissue engineering applications. Herein, we investigated and compared the response of vascular smooth muscle cells (vSMCs) cultured in different culture environments (2D cell monolayers and 3D cellularized collagen-based gels) in combination with mechanical stimulation (7% uniaxial cyclic strain, 1 Hz) for 2 and 5 days. When cyclic strain was applied, two different responses, in terms of cell orientation and expression of contractile-phenotype proteins, were observed in 2D and 3D models.

Data in support of Gallium (Ga(3+)) antibacterial activities to counteract E. coli and S. epidermidis biofilm formation onto pro-osteointegrative titanium surfaces.

This paper contains original data supporting the antibacterial activities of Gallium (Ga(3+))-doped pro-osteointegrative titanium alloys, obtained via Anodic Spark Deposition (ASD), as described in "The effect of silver or gallium doped titanium against the multidrug resistant Acinetobacter baumannii" (Cochis et al. 2016) [1]. In this article we included an indirect cytocompatibility evaluation towards Saos2 human osteoblasts and extended the microbial evaluation of the Ga(3+) enriched titanium surfaces against the biofilm former Escherichia coli and Staphylococcus epidermidis strains.

The study of polyplex formation and stability by time-resolved fluorescence spectroscopy of SYBR Green I-stained DNA.

Polyplexes are nanoparticles formed by the self-assembly of DNA/RNA and cationic polymers specifically designed to deliver exogenous genetic material to cells by a process called transfection. There is a general consensus that a subtle balance between sufficient extracellular protection and intracellular release of nucleic acids is a key factor for successful gene delivery. Therefore, there is a strong need to develop suitable tools and techniques for enabling the monitoring of the stability of polyplexes in the biological environment they face during transfection.

Synthesis of multifunctional PAMAM-aminoglycoside conjugates with enhanced transfection efficiency.

The development of multifunctional vectors for efficient and safe gene delivery is one of the major challenges for scientists working in the gene therapy field. In this context, we have designed a novel type of aminoglycoside-rich dendrimers with a defined structure based on polyamidoamine (PAMAM) in order to develop efficient, nontoxic gene delivery vehicles. Three different conjugates, i.

Lipid-based nanoparticles as nonviral gene delivery vectors.

Efficient delivery of nucleic acids into cells is a promising technique to modulate cellular gene expression for therapeutic and research applications. Cationic lipid-based liposomes represent one of the most intensively studied and employed nonviral vectors. They are positively charged at physiological pH and spontaneously self-assemble with polyanionic nucleic acids forming nanoscaled complexes named lipoplexes.

A novel antibacterial modification treatment of titanium capable to improve osseointegration.

Background: Among the different causes of orthopedic and dental implant failure, infection remains the most serious and devastating complication associated with biomaterial devices.

Purpose: The aim of this study was to develop an innovative osteointegrative and antibacterial biomimetic coating on titanium and to perform a chemical-physical and in vitro biological characterization of the coating using the SAOS-2 cell line. We also studied the antibacterial properties of the coating against both Gram-positive and Gram-negative bacteria strains.

The yin of exofacial protein sulfhydryls and the yang of intracellular glutathione in in vitro transfection with SS14 bioreducible lipoplexes.

Although redox-sensitive transfectants have been considered hitherto as the Holy Grail of gene delivery because of their ability to restrict the release of nucleic acids to intracellular compartments, the reasons for their sometimes lackluster performance do not seem likewise clear. To ascertain the possible influence of extracellular soluble thiols, exofacial protein sulfhydryls (EPTs) and glutathione (GSH) on the overall efficacy of bioreducible lipoplexes, we utilized a cationic gemini surfactant--SS14--in which the two single-chain amphiphiles are held together by a suitable redox-sensitive linkage. We herein draw a big picture whereby the interaction of bioreducible lipoplexes with cells and their internalization are tightly coupled events that ultimately do affect transfection.

We still have a long way to go to effectively deliver genes!

Gene therapy is emerging as a revolutionary alternative to conventional therapeutic approaches. However, its clinical application is still hampered by the lack of safe and effective gene delivery techniques. Among the plethora of diverse approaches used to ferry nucleic acids into target cells, non-viral vectors represent promising and safer alternatives to viruses and physical techniques.

Chitosan-graft-branched polyethylenimine copolymers: influence of degree of grafting on transfection behavior.

Background: Successful non-viral gene delivery currently requires compromises to achieve useful transfection levels while minimizing toxicity. Despite high molecular weight (MW) branched polyethylenimine (bPEI) is considered the gold standard polymeric transfectant, it suffers from high cytotoxicity. Inversely, its low MW counterpart is less toxic and effective in transfection.

Bioreducible liposomes for gene delivery: from the formulation to the mechanism of action.

Background: A promising strategy to create stimuli-responsive gene delivery systems is to exploit the redox gradient between the oxidizing extracellular milieu and the reducing cytoplasm in order to disassemble DNA/cationic lipid complexes (lipoplexes). On these premises, we previously described the synthesis of SS14 redox-sensitive gemini surfactant for gene delivery. Although others have attributed the beneficial effects of intracellular reducing environment to reduced glutathione (GSH), these observations cannot rule out the possible implication of the redox milieu in its whole on transfection efficiency of bioreducible transfectants leaving the determinants of DNA release largely undefined.

Comparative chondrogenesis of human cells in a 3D integrated experimental-computational mechanobiology model.

We present an integrated experimental-computational mechanobiology model of chondrogenesis. The response of human articular chondrocytes to culture medium perfusion, versus perfusion associated with cyclic pressurisation, versus non-perfused culture, was compared in a pellet culture model, and multiphysic computation was used to quantify oxygen transport and flow dynamics in the various culture conditions. At 2 weeks of culture, the measured cell metabolic activity and the matrix content in collagen type II and aggrecan were greatest in the perfused+pressurised pellets.

A dimerizable cationic lipid with potential for gene delivery.

Background: Despite the use of currently optimized lipofection conditions, including transfection in serum-depleted media, the efficiency of gene transfer is low and high transfection rates often induce cytotoxicity. A lipid formulation with transfection efficiency not inhibited by serum would provide an advance towards in vivo applications.

Methods: We explored the ability of the cationic lipid SH-14 to dimerize upon DNA and form lipoplexes, and potentially release nucleic acids in the intracellular reducing milieu.

Growth hormone secretion and bone histomorphometric study in thalassaemic patients with acquired skeletal dysplasia secondary to desferrioxamine.

An auxological and endocrinological study was performed in 21 thalassaemic patients with growth retardation and skeletal dysplasia secondary to desferrioxamine. Bone metaphyseal proximal tibial or iliac crest biopsy was performed in six patients with severe genu valgum or non-traumatic vertebral compression. GH insufficiency/deficiency (GH deficiency: peak after stimulation test below 6 ng/ml) was found in 72% of our thalassaemic patients with skeletal dysplasia, but in only 41% of patients without skeletal dysplasia.