Three-Dimensional Microfibrous Scaffold with Aligned Topography Produced via a Combination of Melt-Extrusion Additive Manufacturing and Porogen Leaching for In Vitro Skeletal Muscle Modeling.

Skeletal muscle tissue (SMT) has a highly hierarchical and anisotropic morphology, featuring aligned and parallel structures at multiple levels. Various factors, including trauma and disease conditions, can compromise the functionality of skeletal muscle. The in vitro modeling of SMT represents a useful tool for testing novel drugs and therapies. The successful replication of SMT native morphology demands scaffolds with an aligned anisotropic 3D architecture. In this work, a 3D PCL fibrous scaffold with aligned morphology was developed through the synergistic combination of Melt-Extrusion Additive Manufacturing (MEAM) and porogen leaching, utilizing PCL as the bulk material and PEG as the porogen. PCL/PEG blends with different polymer ratios (60/40, 50/50, 40/60) were produced and characterized through a DSC analysis. The MEAM process parameters and porogen leaching in bi-distilled water allowed for the development of a micrometric anisotropic fibrous structure with fiber diameters ranging from 10 to 100 µm, depending on PCL/PEG blend ratios. The fibrous scaffolds were coated with Gelatin type A to achieve a biomimetic coating for an in vitro cell culture and mechanically characterized via AFM. The 40/60 PCL/PEG scaffolds yielded the most homogeneous and smallest fibers and the greatest physiological stiffness. In vitro cell culture studies were performed by seeding C2C12 cells onto a selected scaffold, enabling their attachment, alignment, and myotube formation along the PCL fibers during a 14-day culture period. The resultant anisotropic scaffold morphology promoted SMT-like cell conformation, establishing a versatile platform for developing in vitro models of tissues with anisotropic morphology.

Biomimetic Electrospun Scaffold-Based In Vitro Model Resembling the Hallmarks of Human Myocardial Fibrotic Tissue.

Adverse remodeling post-myocardial infarction is hallmarked by the phenotypic change of cardiac fibroblasts (CFs) into myofibroblasts (MyoFs) and over-deposition of the fibrotic extracellular matrix (ECM) mainly composed by fibronectin and collagens, with the loss of tissue anisotropy and tissue stiffening. Reversing cardiac fibrosis represents a key challenge in cardiac regenerative medicine. Reliable in vitro models of human cardiac fibrotic tissue could be useful for preclinical testing of new advanced therapies, addressing the limited predictivity of traditional 2D cell cultures and animal in vivo models. In this work, we engineered a biomimetic in vitro model, reproducing the morphological, mechanical, and chemical cues of native cardiac fibrotic tissue. Polycaprolactone (PCL)-based scaffolds with randomly oriented fibers were fabricated by solution electrospinning technique, showing homogeneous nanofibers with an average size of 131 ± 39 nm. PCL scaffolds were then surface-functionalized with human type I collagen (C1) and fibronectin (F) by dihydroxyphenylalanine (DOPA)-mediated mussel-inspired approach (PCL/polyDOPA/C1F), in order to mimic fibrotic cardiac tissue-like ECM composition and support human CF culture. BCA assay confirmed the successful deposition of the biomimetic coating and its stability during 5 days of incubation in phosphate-buffered saline. Immunostaining for C1 and F demonstrated their homogeneous distribution in the coating. AFM mechanical characterization showed that PCL/polyDOPA/C1F scaffolds, in wet conditions, resembled fibrotic tissue stiffness with an average Young's modulus of about 50 kPa. PCL/polyDOPA/C1F membranes supported human CF (HCF) adhesion and proliferation. Immunostaining for α-SMA and quantification of α-SMA-positive cells showed HCF activation into MyoFs in the absence of a transforming growth factor ß (TGF-ß) profibrotic stimulus, suggesting the intrinsic ability of biomimetic PCL/polyDOPA/C1F scaffolds to sustain the development of cardiac fibrotic tissue. A proof-of-concept study making use of a commercially available antifibrotic drug confirmed the potentialities of the developed in vitro model for drug efficacy testing. In conclusion, the proposed model was able to replicate the main hallmarks of early-stage cardiac fibrosis, appearing as a promising tool for future preclinical testing of advanced regenerative therapies.

Biomimetic design of bioartificial scaffolds for the in vitro modelling of human cardiac fibrosis.

In vitro models of pathological cardiac tissue have attracted interest as predictive platforms for preclinical validation of therapies. However, models reproducing specific pathological features, such as cardiac fibrosis size (i.e., thickness and width) and stage of development are missing. This research was aimed at engineering 2D and 3D models of early-stage post-infarct fibrotic tissue (i.e., characterized by non-aligned tissue organization) on bioartificial scaffolds with biomimetic composition, design, and surface stiffness. 2D scaffolds with random nanofibrous structure and 3D scaffolds with 150 µm square-meshed architecture were fabricated from polycaprolactone, surface-grafted with gelatin by mussel-inspired approach and coated with cardiac extracellular matrix (ECM) by 3 weeks culture of human cardiac fibroblasts. Scaffold physicochemical properties were thoroughly investigated. AFM analysis of scaffolds in wet state, before cell culture, confirmed their close surface stiffness to human cardiac fibrotic tissue. Following 3 weeks culture, biomimetic biophysical and biochemical scaffold properties triggered the activation of myofibroblast phenotype. Upon decellularization, immunostaining, SEM and two-photon excitation fluorescence microscopy showed homogeneous decoration of both 2D and 3D scaffolds with cardiac ECM. The versatility of the approach was demonstrated by culturing ventricular or atrial cardiac fibroblasts on scaffolds, thus suggesting the possibility to use the same scaffold platforms to model both ventricular and atrial cardiac fibrosis. In the future, herein developed in vitro models of cardiac fibrotic tissue, reproducing specific pathological features, will be exploited for a fine preclinical tuning of therapies.

Development of an Innovative Soft Piezoresistive Biomaterial Based on the Interconnection of Elastomeric PDMS Networks and Electrically-Conductive PEDOT:PSS Sponges.

A deeply interconnected flexible transducer of polydimethylsiloxane (PDMS) and poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) was obtained as a material for the application of soft robotics. Firstly, transducers were developed by crosslinking PEDOT:PSS with 3-glycidyloxypropryl-trimethoxysilane (GPTMS) (1, 2 and 3% v/v) and using freeze-drying to obtain porous sponges. The PEDOT:PSS sponges were morphologically characterized, showing porosities mainly between 200 and 600 µm2; such surface area dimensions tend to decrease with increasing degrees of crosslinking. A stability test confirmed a good endurance for up to 28 days for the higher concentrations of the crosslinker tested. Consecutively, the sponges were electromechanically characterized, showing a repeatable and linear resistance variation by the pressure triggers within the limits of their working range (∆RR0 max = 80% for 1-2% v/v of GPTMS). The sponges containing 1% v/v of GPTMS were intertwined with a silicon elastomer to increase their elasticity and water stability. The flexible transducer obtained with this method exhibited moderately lower sensibility and repeatability than the PEDOT:PSS sponges, but the piezoresistive response remained stable under mechanical compression. Furthermore, the transducer displayed a linear behavior when stressed within the limits of its working range. Therefore, it is still valid for pressure sensing and contact detection applications. Lastly, the flexible transducer was submitted to preliminary biological tests that indicate a potential for safe, in vivo sensing applications.

Tissue-Engineered Models of the Human Brain: State-of-the-Art Analysis and Challenges.

Neurological disorders affect billions of people across the world, making the discovery of effective treatments an important challenge. The evaluation of drug efficacy is further complicated because of the lack of in vitro models able to reproduce the complexity of the human brain structure and functions. Some limitations of 2D preclinical models of the human brain have been overcome by the use of 3D cultures such as cell spheroids, organoids and organs-on-chip. However, one of the most promising approaches for mimicking not only cell structure, but also brain architecture, is currently represented by tissue-engineered brain models. Both conventional (particularly electrospinning and salt leaching) and unconventional (particularly bioprinting) techniques have been exploited, making use of natural polymers or combinations between natural and synthetic polymers. Moreover, the use of induced pluripotent stem cells (iPSCs) has allowed the co-culture of different human brain cells (neurons, astrocytes, oligodendrocytes, microglia), helping towards approaching the central nervous system complexity. In this review article, we explain the importance of in vitro brain modeling, and present the main in vitro brain models developed to date, with a special focus on the most recent advancements in tissue-engineered brain models making use of iPSCs. Finally, we critically discuss achievements, main challenges and future perspectives.

In situ Forming Hyperbranched PEG-Thiolated Hyaluronic Acid Hydrogels With Honey-Mimetic Antibacterial Properties.

The rapidly increasing resistance of bacteria to currently approved antibiotic drugs makes surgical interventions and the treatment of bacterial infections increasingly difficult. In recent years, complementary strategies to classical antibiotic therapy have, therefore, gained importance. One of these strategies is the use of medicinal honey in the treatment of bacterially colonized wounds. One of the several bactericidal effects of honey is based on the in situ generation of hydrogen peroxide through the activity of the enzyme glucose oxidase. The strategy underlying this work is to mimic this antibacterial redox effect of honey in an injectable, biocompatible, and rapidly forming hydrogel. The hydrogel was obtained by thiol-ene click reaction between hyperbranched polyethylene glycol diacrylate (HB PEGDA), synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization, and thiolated hyaluronic acid (HA-SH). After mixing 500 µL HB PEGDA (10%, w/w) and 500 µL HA-SH (1%, w/w) solutions, hydrogels formed in ∼60 s (HB PEGDA/HA-SH 10.0-1.0), as assessed by the tube inverting test. The HB PEGDA/HA-SH 10.0-1.0 hydrogel (200 µL) was resistant to in vitro dissolution in water for at least 64 days, absorbing up to 130 wt% of water. Varying glucose oxidase (GO) amounts (0-500 U/L) and constant glucose content (2.5 wt%) were loaded into HB PEGDA and HA-SH solutions, respectively, before hydrogel formation. Then, the release of H2O2 was evaluated through a colorimetric pertitanic acid assay. The GO content of 250 U/L was selected, allowing the formation of 10.8 ± 1.4 mmol H2O2/L hydrogel in 24 h, under static conditions. The cytocompatibility of HB PEGDA/HA-SH 10.0-1.0 hydrogels loaded with different GO activities (≤ 500 U/L) at a constant glucose amount (2.5 wt%) was investigated by in vitro assays at 24 h with L929 and HaCaT cell lines, according to DIN EN ISO 10993-5. The tests showed cytocompatibility for GO enzyme activity up to 250 U/L for both cell lines. The antibacterial activity of HB PEGDA/HA-SH 10.0-1.0 hydrogels loaded with increasing amounts of GO was demonstrated against various gram-positive bacteria (S. aureus and S. epidermidis), antibiotic-resistant gram-positive bacteria (MRSA and MRSE), gram-negative bacteria (P. aeruginosa, E. coli, and A. baumanii), and antibiotic-resistant gram-negative strains (P. aeruginosa and E. coli) using agar diffusion tests. For all gram-positive bacterial strains, increasing efficacy was measured with increasing GO activity. For the two P. aeruginosa strains, efficacy was shown only from an enzyme activity of 125 U/L and for E. coli and A. baumanii, efficacy was shown only from 250 U/L enzyme activity. HB PEGDA/HA-SH 10.0-1.0 hydrogels loaded with ≤250 U/L GO and 2.5 wt% glucose are promising formulations due to their fast-forming properties, cytocompatibility, and ability to produce antibacterial H2O2, warranting future investigations for bacterial infection treatment, such as wound care.

Mussel-inspired antimicrobial coating on PTFE barrier membranes for guided tissue regeneration.

Guided tissue regeneration procedures to treat periodontitis lesions making use of polytetrafluoroethylene (PTFE) membranes exhibit large variability in their surgical outcomes, due to bacterial infection following implantation. This work reports on a facile method to obtain antimicrobial coatings for such PTFE membranes, by exploiting a mussel-inspired approach andin-situformation of silver nanoparticles (AgNPs). PTFE films were initially coated with self-polymerized 3,4-dihydroxy-DL-phenylalanine (DOPA) (PTFE-DOPA), then incubated with AgNO3solution. In the presence of catechol moieties, Ag+ions reduced into Ag0, forming AgNPs of around 68 nm in the polyDOPA coating on PTFE membranes (PTFE-DOPA-Ag). The x-ray photoelectron spectroscopy, atomic force microscopy and scanning electron microscopy analyses indicated that the AgNPs were distributed quite homogeneously in the polymeric membrane. The antimicrobial ability of PTFE-DOPA-Ag membranes againstStaphylococcus aureusandEscherichia coliwas assessed.In vitrocell assay using NIH 3T3 fibroblasts showed that, although cells were adhered to PTFE-DOPA-Ag membranes, their viability and proliferation were limited demonstrating again the antibacterial activities of PTFE-DOPA-Ag membranes. This work provides proof-of-concept study of a new versatile approach for AgNPs coating, which may be easily applied to many other types of polymeric or metallic implants through exploiting the adhesive behavior of mussel-inspired coatings.

PLGA Membranes Functionalized with Gelatin through Biomimetic Mussel-Inspired Strategy.

Electrospun membranes have been widely used as scaffolds for soft tissue engineering due to their extracellular matrix-like structure. A mussel-inspired coating approach based on 3,4-dihydroxy-DL-phenylalanine (DOPA) polymerization was proposed to graft gelatin (G) onto poly(lactic-co-glycolic) acid (PLGA) electrospun membranes. PolyDOPA coating allowed grafting of gelatin to PLGA fibers without affecting their bulk characteristics, such as molecular weight and thermal properties. PLGA electrospun membranes were dipped in a DOPA solution (2 mg/mL, Tris/HCl 10 mM, pH 8.5) for 7 h and then incubated in G solution (2 mg/mL, Tris/HCl 10 mM, pH 8.5) for 16 h. PLGA fibers had an average diameter of 1.37 ± 0.23 µm. Quartz crystal microbalance with dissipation technique (QCM-D) analysis was performed to monitor DOPA polymerization over time: after 7 h the amount of deposited polyDOPA was 71 ng/cm2. After polyDOPA surface functionalization, which was, also revealed by Raman spectroscopy, PLGA membranes maintained their fibrous morphology, however the fiber size and junction number increased. Successful functionalization with G was demonstrated by FTIR-ATR spectra, which showed the presence of G adsorption bands at 1653 cm-1 (Amide I) and 1544 cm-1 (Amide II) after G grafting, and by the Kaiser Test, which revealed a higher amount of amino groups for G functionalized membranes. Finally, the biocompatibility of the developed substrates and their ability to induce cell growth was assessed using Neonatal Normal Human Dermal Fibroblasts.

DLP 3D Printing Meets Lignocellulosic Biopolymers: Carboxymethyl Cellulose Inks for 3D Biocompatible Hydrogels.

The development of new bio-based inks is a stringent request for the expansion of additive manufacturing towards the development of 3D-printed biocompatible hydrogels. Herein, methacrylated carboxymethyl cellulose (M-CMC) is investigated as a bio-based photocurable ink for digital light processing (DLP) 3D printing. CMC is chemically modified using methacrylic anhydride. Successful methacrylation is confirmed by 1H NMR and FTIR spectroscopy. Aqueous formulations based on M-CMC/lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) photoinitiator and M-CMC/Dulbecco's Modified Eagle Medium (DMEM)/LAP show high photoreactivity upon UV irradiation as confirmed by photorheology and FTIR. The same formulations can be easily 3D-printed through a DLP apparatus to produce 3D shaped hydrogels with excellent swelling ability and mechanical properties. Envisaging the application of the hydrogels in the biomedical field, cytotoxicity is also evaluated. The light-induced printing of cellulose-based hydrogels represents a significant step forward in the production of new DLP inks suitable for biomedical applications.

In-vitro Characterization of a Hernia Mesh Featuring a Nanostructured Coating.

Abdominal hernia repair is a frequently performed surgical procedure worldwide. Currently, the use of polypropylene (PP) surgical meshes for the repair of abdominal hernias constitutes the primary surgical approach, being widely accepted as superior to primary suture repair. Surgical meshes act as a reinforcement for the weakened or damaged tissues and support tissue restoration. However, implanted meshes could suffer from poor integration with the surrounding tissues. In this context, the present study describes the preliminary evaluation of a PCL-Gel-based nanofibrous coating as an element to develop a multicomponent hernia mesh device (meshPCL-Gel) that could overcome this limitation thanks to the presence of a nanostructured biomimetic substrate for enhanced cell attachment and new tissue formation. Through the electrospinning technique, a commercial PP hernia mesh was coated with a nanofibrous membrane from a polycaprolactone (PCL) and gelatin (Gel) blend (PCL-Gel). Resulting PCL-Gel nanofibers were homogeneous and defect-free, with an average diameter of 0.15 ± 0.04 µm. The presence of Gel decreased PCL hydrophobicity, so that membranes average water contact angle dropped from 138.9 ± 1.1° (PCL) to 99.9 ± 21.6°, while it slightly influenced mechanical properties, which remained comparable to those of PCL (E = 15.7 ± 2.7 MPa, σ R = 7.7 ± 0.6 ε R = 118.8 ± 13.2%). Hydrolytic and enzymatic degradation was conducted on PCL-Gel up to 28 days, with maximum weight losses around 20 and 40%, respectively. The meshPCL-Gel device was obtained with few simple steps, with no influences on the original mechanical properties of the bare mesh, and good stability under physiological conditions. The biocompatibility of meshPCL-Gel was assessed by culturing BJ human fibroblasts on the device, up to 7 days. After 24 h, cells adhered to the nanofibrous substrate, and after 72 h their metabolic activity was about 70% with respect to control cells. The absence of detectable lactate dehydrogenase in the culture medium indicated that no necrosis induction occurred. Hence, the developed nanostructured coating provided the meshPCL-Gel device with chemical and topographical cues similar to the native extracellular matrix ones, that could be exploited for enhancing the biological response and, consequently, mesh integration, in abdominal wall hernia repair.

Medical-Grade Silicone Coated with Rhamnolipid R89 Is Effective against Staphylococcus spp. Biofilms.

Staphylococcus aureus and Staphylococcus epidermidis are considered two of the most important pathogens, and their biofilms frequently cause device-associated infections. Microbial biosurfactants recently emerged as a new generation of anti-adhesive and anti-biofilm agents for coating implantable devices to preserve biocompatibility. In this study, R89 biosurfactant (R89BS) was evaluated as an anti-biofilm coating on medical-grade silicone. R89BS is composed of homologues of the mono- (75%) and di-rhamnolipid (25%) families, as evidenced by mass spectrometry analysis. The antimicrobial activity against Staphylococcus spp. planktonic and sessile cells was evaluated by microdilution and metabolic activity assays. R89BS inhibited S. aureus and S. epidermidis growth with minimal inhibitory concentrations (MIC99) of 0.06 and 0.12 mg/mL, respectively and dispersed their pre-formed biofilms up to 93%. Silicone elastomeric discs (SEDs) coated by R89BS simple adsorption significantly counteracted Staphylococcus spp. biofilm formation, in terms of both built-up biomass (up to 60% inhibition at 72 h) and cell metabolic activity (up to 68% inhibition at 72 h). SEM analysis revealed significant inhibition of the amount of biofilm-covered surface. No cytotoxic effect on eukaryotic cells was detected at concentrations up to 0.2 mg/mL. R89BS-coated SEDs satisfy biocompatibility requirements for leaching products. Results indicate that rhamnolipid coatings are effective anti-biofilm treatments and represent a promising strategy for the prevention of infection associated with implantable devices.

Tailored functionalization of poly(L-lactic acid) substrates at the nanoscale to enhance cell response.

Poly(L-lactic) acid (PLLA) has been widely employed in tissue engineering due to its mechanical properties, biodegradability and biocompatibility. The layer-by-layer (LbL) technique was here proposed as a simple method to impart bioactivity to the surface of PLLA substrates. Aminolysis treatment was applied to introduce amino groups on the surface of PLLA solvent cast films. Then, PLLA films were coated with heparin (HE)/chitosan (CH) multilayer by the LbL technique. Each functionalization step was characterized through physico-chemical and morphological analyses. Aminolysis treatment increased film surface wettability (64.8° ± 2.4° against 74.6° ± 1.3° for untreated PLLA) due to the formation of surface amino groups, which were quantified by acid orange colorimetric assay (0.05 nmol/mm2). After the deposition of 9 layers, the static contact angle varied between values close to 40° C (HE-based layer) and 60 °C (CH-based layer), showing the typical alternate trend of LbL coating. The successful HE/CH deposition was confirmed by ATR-FTIR and X-ray photoelectron spectroscopy (XPS) analyses. Particularly, XPS spectra of coated samples showed the presence of nitrogen (indicative of HE and CH deposition), and sulfur (indicative of HE deposition). The amount of deposited HE was quantified by Taylor's Blue colorimetric method: after the deposition of 19 and 20 layers the HE concentration was around 33 µg/cm2. Finally, in vitro studies performed using HaCaT immortalized human skin keratinocytes, C2C12 immortalized mouse myoblasts and human fibroblasts demonstrated that HE/CH multilayer-coated PLLA is a promising substrate for soft tissue engineering, as cell response may be modulated by changing the surface chemical properties.

Quartz Crystal Microbalance With Dissipation Monitoring: A Powerful Method to Predict the in vivo Behavior of Bioengineered Surfaces.

The Quartz Crystal Microbalance with dissipation monitoring (QCM-D) is a tool to measure mass and viscosity in processes occurring at or near surfaces, or within thin films. QCM-D is able to detect extremely small chemical, mechanical, and electrical changes taking place on the sensor surface and to convert them into electrical signals which can be investigated to study dynamic process. Surface nanotopography and chemical composition are of pivotal importance in biomedical applications since interactions of medical devices with the physiological environment are mediated by surface features. This review is intended to provide readers with an up-to-date summary of QCM-D applications in the study of cell behavior and to discuss the future trends for the use of QCM-D as a high-throughput method to study cell/surface interactions overcoming the current challenges in the design of biomedical devices.

Surface functionalization of polyurethane scaffolds mimicking the myocardial microenvironment to support cardiac primitive cells.

Scaffolds populated with human cardiac progenitor cells (CPCs) represent a therapeutic opportunity for heart regeneration after myocardial infarction. In this work, square-grid scaffolds are prepared by melt-extrusion additive manufacturing from a polyurethane (PU), further subjected to plasma treatment for acrylic acid surface grafting/polymerization and finally grafted with laminin-1 (PU-LN1) or gelatin (PU-G) by carbodiimide chemistry. LN1 is a cardiac niche extracellular matrix component and plays a key role in heart formation during embryogenesis, while G is a low-cost cell-adhesion protein, here used as a control functionalizing molecule. X-ray photoelectron spectroscopy analysis shows nitrogen percentage increase after functionalization. O1s and C1s core-level spectra and static contact angle measurements show changes associated with successful functionalization. ELISA assay confirms LN1 surface grafting. PU-G and PU-LN1 scaffolds both improve CPC adhesion, but LN1 functionalization is superior in promoting proliferation, protection from apoptosis and expression of differentiation markers for cardiomyocytes, endothelial and smooth muscle cells. PU-LN1 and PU scaffolds are biodegraded into non-cytotoxic residues. Scaffolds subcutaneously implanted in mice evoke weak inflammation and integrate with the host tissue, evidencing a significant blood vessel density around the scaffolds. PU-LN1 scaffolds show their superiority in driving CPC behavior, evidencing their promising role in myocardial regenerative medicine.

Biomimetic engineering of the cardiac tissue through processing, functionalization, and biological characterization of polyester urethanes.

Three-dimensional (3D) tissue models offer new tools in the study of diseases. In the case of the engineering of cardiac muscle, a realistic goal would be the design of a scaffold able to replicate the tissue-specific architecture, mechanical properties, and chemical composition, so that it recapitulates the main functions of the tissue. This work is focused on the design and preliminary biological validation of an innovative polyester urethane (PUR) scaffold mimicking cardiac tissue properties. The porous scaffold was fabricated by thermally induced phase separation (TIPS) from poly(ε-caprolactone) diol, 1,4-butanediisocyanate, and l-lysine ethyl ester. Morphological and mechanical scaffolds characterization was accomplished by confocal microscopy, and micro-tensile and compression techniques. Scaffolds were then functionalized with fibronectin by plasma treatment, and the surface treatment was studied by x-ray photoelectron spectroscopy, attenuated total reflectance Fourier transform infrared spectra, and contact angle measurements. Primary rat neonatal cardiomyocytes were seeded on scaffolds, and their colonization, survival, and beating activity were analyzed for 14 days. Signal transduction pathways and apoptosis involved in cells, the structural development of the heart, and its metabolism were analyzed. PUR scaffolds showed a porous-aligned structure and mechanical properties consistent with that of the myocardial tissue. Cardiomyocytes plated on the scaffolds showed a high survival rate and a stable beating activity. Serine/threonine kinase (AKT) and extracellular signal-regulated kinases (ERK) phosphorylation was higher in cardiomyocytes cultured on the PUR scaffold compared to those on tissue culture plates. Real-time polymerase chain reaction analysis showed a significant modulation at 14 days of cardiac muscle (MYH7, prepro-ET-1), hypertrophy-specific (CTGF), and metabolism-related (SLC2a1, PFKL) genes in PUR scaffolds.

Silk fibres grafted with 2-hydroxyethyl methacrylate (HEMA) and 4-hydroxybutyl acrylate (HBA) for biomedical applications.

Silk fibroin may be chemically modified by grafting, with the purpose of improving its properties according to the desired function. In this study, silk fabrics from Bombyx mori silk fibres were grafted with 2-hydroxyethyl methacrylate (HEMA), as well as a binary mixture of HEMA and 4-hydroxybutyl acrylate (HBA). The samples were then electrospun from trifluoroacetic acid and treated with aqueous methanol. The% weight gains ascribable to HEMA and HBA were successfully determined through Raman spectroscopy. PolyHEMA made the fibres more hydrophilic and hindered crystallization into ß-sheet only upon electrospinning and treatment with aqueous methanol; the presence of the HBA component in the grafting mixture did not further decrease the ability of silk fibroin to rearrange into ß-sheet, due to its low contents (below 5%) under the used experimental conditions. Fibrillation partially occurred in the grafted fabrics; the electrospun samples maintained their nanostructured morphology. The surface of the substrates under investigation was compatible with cell attachment and growth, which were higher for the nanofibres. Cell adhesion and proliferation may be modulated by varying the surface chemistry and topography of the fabrics; grafting improved the surface properties of silk fibroin for enhanced functional performance in view of biomedical applications.

Intermolecular interactions between B. mori silk fibroin and poly(l-lactic acid) in electrospun composite nanofibrous scaffolds.

In this study, composite nanofibrous scaffolds were obtained by electrospinning a trifluoroacetic acid solution containing B. mori silk fibroin (SF) and poly(l-lactic acid) (PLLA) in a 1:1 weight ratio. SF, PLLA and SF/PLLA nanofibres were prepared with average diameter sizes of 360±90nm, 470±240nm and 580±220nm, respectively, as assessed by SEM analysis. Vibrational and thermal analyses showed that upon blending in the SF/PLLA nanofibres, the crystallisation of PLLA was hindered by the presence of SF, which crystallized preferentially and underwent conformational changes that did not significantly change its prevailing ß-sheet structure. The two components were thermodynamically compatible and the intermolecular interactions between them were revealed for the first time. Human keratinocytes were cultured on nanofibres and their viability and proliferation were determined. Preliminary in vitro tests showed that the incorporation of SF into the PLLA component enhanced cell adhesion and proliferation with respect to the unfunctionalised material. SF has been successfully used to modify the biomaterial properties and confirmed to be an efficient bioactive protein to mediate cell-biomaterial interaction.

Lipopeptides from Bacillus subtilis AC7 inhibit adhesion and biofilm formation of Candida albicans on silicone.

Candida albicans is the major fungus that colonises medical implants, causing device-associated infections with high mortality. Antagonistic bacterial products with interesting biological properties, such as biosurfactants, have recently been considered for biofilm prevention. This study investigated the activity of lipopeptide biosurfactant produced by Bacillus subtilis AC7 (AC7 BS) against adhesion and biofilm formation of C. albicans on medical-grade silicone elastomeric disks (SEDs). Chemical analysis, stability, surface activities of AC7 BS crude extract and physicochemical characterisation of the coated silicone disk surfaces were also carried out. AC7 BS showed a good reduction of water surface tension, low critical micelle concentration, good emulsification activity, thermal resistance and pH stability. Co-incubation with 2 mg ml(-1) AC7 BS significantly reduced adhesion and biofilm formation of three C. albicans strains on SEDs in a range of 67-69 % and of 56-57 %, respectively. On pre-coated SEDs, fungal adhesion and biofilm formation were reduced by 57-62 % and 46-47 %, respectively. Additionally, AC7 BS did not inhibit viability of C. albicans strains in both planktonic and sessile form. Chemical analysis of the crude extract revealed the presence of two families of lipopeptides, principally surfactin and a lower percentage of fengycin. The evaluation of surface wettability indicated that AC7 BS coating of SEDs surface was successful although uneven. AC7 BS significantly prohibits the initial deposition of C. albicans and slows biofilm growth, suggesting a potential role of biosurfactant coatings for preventing fungal infection associated with silicone medical devices.

An overview of poly(lactic-co-glycolic) acid (PLGA)-based biomaterials for bone tissue engineering.

Poly(lactic-co-glycolic) acid (PLGA) has attracted considerable interest as a base material for biomedical applications due to its: (i) biocompatibility; (ii) tailored biodegradation rate (depending on the molecular weight and copolymer ratio); (iii) approval for clinical use in humans by the U.S. Food and Drug Administration (FDA); (iv) potential to modify surface properties to provide better interaction with biological materials; and (v) suitability for export to countries and cultures where implantation of animal-derived products is unpopular. This paper critically reviews the scientific challenge of manufacturing PLGA-based materials with suitable properties and shapes for specific biomedical applications, with special emphasis on bone tissue engineering. The analysis of the state of the art in the field reveals the presence of current innovative techniques for scaffolds and material manufacturing that are currently opening the way to prepare biomimetic PLGA substrates able to modulate cell interaction for improved substitution, restoration, or enhancement of bone tissue function.