Florencia Montini Ballarin

HMDSO-plasma coated electrospun fibers of poly(cyclodextrin)s for antifungal dressings

Electrospun mats containing cyclodextrin polymers (poly-αCD or poly-βCD) were developed to act as wound dressings showing tunable release rate of the antifungal agent fluconazole incorporated forming inclusion complexes. Poly-αCD and poly-βCD were prepared via cross-linking with epichlorohydrin (EPI) as water-soluble large molecular weight polymers. Then, polyCDs forming complexes with fluconazole were mixed with poly-(ε-caprolactone) (PCL) or poly(N-vinylpyrrolidone) (PVP) for electrospinning. Obtained bead-free fibers showed a random distribution, diameters in the 350-850nm range, and a variety of physical stability behaviors in aqueous environment. Mats were coated by hexamethyldisiloxane (HMDSO) plasma polymerization to create a hydrophobic layer that prevented rapid drug diffusion. HMDSO coating was evidenced by the Si content of mat surface (EDX analysis) and by the increase in the water contact angle (up to 130°). In physiological-mimicking medium, non-treated mats showed burst release of fluconazole, whereas HMDSO-coated mats sustained the release and delayed disintegration of PVP-based mats. Antifungal tests evidenced that both coated and non-coated mats efficiently inhibited the growth of Candida albicans.

Similarities of arterial collagen pressure-diameter relationship in ovine femoral arteries and PLLA vascular grafts.

Introduction: In-vivo implanted vascular grafts fail due to the mechanical mismatch between the native vessel and the implant. The biomechanical characterization of native vessels provides valuable information towards the development of synthetic grafts. Materials and Methods: Five samples of electrospun nanofibrous poly(L-lactic acid)(PLLA) tubular structures were subjected to physiological pulsating pressure using an experimental setup. Four ovine femoral arteries were also tested in the experimental setup under the same conditions. Instantaneous diameter and pressure signals were obtained using gold standard techniques, in order to estimate the dynamic pressure-strain elastic modulus (EPε) of both native vessels and grafts. Results: Synthetic grafts showed a significant increase of EPε (10.57±0.97 to 17.63±2.61 106 dyn/cm2) when pressure was increased from a range of 50-90 mmHg (elastin-response range) to a range of 100-130 mmHg (collagen-response range). Furthermore, femoral arteries also exhibited a significant increase of EPε (1.66±0.30 to 15.76±4.78 106 dyn/cm2) with the same pressure variation, showing that both native vessels and synthetic grafts have a similar behavior in the collagen-acting range. Conclusion: The mechanical behavior of PLLA vascular grafts was characterized In vitro. However, the procedure can be easily extrapolated to In vivo experiences in conscious and chronically instrumented animals.

Aligned ovine diaphragmatic myoblasts overexpressing human connexin-43 seeded on poly (l-lactic acid) scaffolds for potential use in cardiac regeneration

Diaphragmatic myoblasts (DMs) are precursors of type-1 muscle cells displaying high exhaustion threshold on account that they contract and relax 20 times/min over a lifespan, making them potentially useful in cardiac regeneration strategies. Besides, it has been shown that biomaterials for stem cell delivery improve cell retention and viability in the target organ. In the present study, we aimed at developing a novel approach based on the use of poly (L-lactic acid) (PLLA) scaffolds seeded with DMs overexpressing connexin-43 (cx43), a gap junction protein that promotes inter-cell connectivity. DMs isolated from ovine diaphragm biopsies were characterized by immunohistochemistry and ability to differentiate into myotubes (MTs) and transduced with a lentiviral vector encoding cx43. After confirming cx43 expression (RT-qPCR and Western blot) and its effect on inter-cell connectivity (fluorescence recovery after photobleaching), DMs were grown on fiber-aligned or random PLLA scaffolds. DMs were successfully isolated and characterized. Cx43 mRNA and protein were overexpressed and favored inter-cell connectivity. Alignment of the scaffold fibers not only aligned but also elongated the cells, increasing the contact surface between them. This novel approach is feasible and combines the advantages of bioresorbable scaffolds as delivery method and a cell type that on account of its features may be suitable for cardiac regeneration. Future studies on animal models of myocardial infarction are needed to establish its usefulness on scar reduction and cardiac function.

High pressure assessment of bilayered electrospun vascular grafts by means of an Electroforce Biodynamic System

Introduction: Tissue engineering offers the possibility of developing a biological substitute material in vitro with the inherent properties required in vivo. However, the inadequate performance in vascular replacement of small diameter vascular grafts (VG) reduces considerably the current alternatives in this field. In this study, a bilayered tubular VG was produced, where its mechanical response was tested at high pressure ranges and compared to a native femoral artery. Materials and Method: The VG was obtained using sequential electrospinning technique, by means of two blends of Poly(L-lactic acid) and segmented poly(ester urethane). Mechanical testing was performed in a biodynamic system and the pressure-strain relationship was used to determine the elastic modulus. Results: Elastic modulus assessed value of femoral artery at a high pressure range (33.02×106 dyn/cm2) was founded to be 36% the magnitude of VG modulus (91.47×106 dyn/cm2) at the same interval. Conclusion: A new circulating mock in combination with scan laser micrometry have been employed for the mechanical evaluation of bioresorbable bilayered VGs. At same pressure levels, graft elasticity showed a purely “collagenic” behavior with respect to a femoral artery response.

Effect of poly (l-lactic acid) scaffolds seeded with aligned diaphragmatic myoblasts overexpressing connexin-43 on infarct size and ventricular function in sheep with acute coronary occlusion

Abstract Diaphragmatic myoblasts (DM) are stem cells of the diaphragm, a muscle displaying high resistance to stress and exhaustion. We hypothesized that DM modified to overexpress connexin-43 (cx43), seeded on aligned poly (l-lactic acid) (PLLA) sheets would decrease infarct size and improve ventricular function in sheep with acute myocardial infarction (AMI). Sheep with AMI received PLLA sheets without DM (PLLA group), sheets with DM (PLLA-DM group), sheets with DM overexpressing cx43 (PLLA-DMcx43) or no treatment (control group, n = 6 per group). Infarct size (cardiac magnetic resonance) decreased ∼25% in PLLA-DMcx43 [from 8.2 ± 0.6 ml (day 2) to 6.5 ± 0.7 ml (day 45), p < .01, ANOVA-Bonferroni] but not in the other groups. Ejection fraction (EF%) (echocardiography) at 3 days post-AMI fell significantly in all groups. At 45 days, PLLA-DM y PLLA-DMcx43 recovered their EF% to pre-AMI values (PLLA-DM: 61.1 ± 0.5% vs. 58.9 ± 3.3%, p = NS; PLLA-DMcx43: 64.6 ± 2.9% vs. 56.9 ± 2.4%, p = NS), but not in control (56.8 ± 2.0% vs. 43.8 ± 1.1%, p < .01) and PLLA (65.7 ± 2.1% vs. 56.6 ± 4.8%, p < .01). Capillary density was higher (p < .05) in PLLA-DMcx43 group than in the remaining groups. In conclusion, PLLA-DMcx43 reduces infarct size in sheep with AMI. PLLA-DMcx43 and PLLA-DM improve ventricular function similarly. Given its safety and feasibility, this novel approach may prove beneficial in the clinic.

Micro/nanofiber-based scaffolds for soft tissue engineering applications: Potential and current challenges

Bioresorbable micro/nanofiber-based structures are being studied as promising candidates for tissue engineering applications. Among the existing techniques for producing these matrices, electrospinning has attracted interest in many technological fields as a versatile and powerful processing technique. Electrospun micro/nanofibers possess high surface-area-to-volume ratio, high porosity and pore interconnectivity, and tunable fiber morphology and orientation. Moreover, submicron fibers are found in the extracellular matrix of natural organs and tissues. To date, many synthetic and natural polymers, biodegradable or non-biodegradable polymers, ceramics and composite materials, have been successfully electrospun using a plethora of techniques. Although in the beginning electrospinning was focused in producing two-dimensional structures, nowadays three-dimensional structures are also being developed. Besides the progress in the electrospinning process achieved in recent years, there still remain a number of challenges, such as mechanical, physical, and chemical biomimeticity, pore size enlargement, surface functionalization, therapeutic agent/cell loading, vascularization, and cell infiltration. This chapter reviews the research advances made in electrospun scaffolds for soft tissue engineering applications focusing on wound dressing, cartilage, muscle, cardiovascular, nerve, and skin tissues.

Nanofibras electrohiladas para usos terapéuticos.

Res_eng:Nanofibrous materials have a huge potential for the development of both extracellular matrices for tissue engineering applications and new systems for therapeutic agents delivery. In this chapter, the fundamentals for preparation of polymeric or composite nanofibrous matrices by electrospinning of solutions are briefly presented. Although electrospinning is a versatile technique for nanofiber production, the process is very complex and it depends on numerous processing parameters and intrinsic properties of the solution. The main variables that affect the process, the commercially available equipment and recent developments are described. In the biomedical field, several strategies for cell incorporation, techniques for pore enlargement and cellular infiltration improvement as well as cell behavior in nanofibrous structures, are presented. Among the main applications in the biomedical field, the ongoing research advances in tissue engineering (bone, cartilage, vascular, nerve and skin) and the development of multifunctional matrices for controlled release of therapeutic agents are discussed. Future perspectives on development and new applications of nanofibrous biomaterials are finally mentioned.

An In Vitro Set Up for the Assessment of Electrospun Nanofibrous Vascular Grafts

Introduction: An experimental setup, using gold standard and high resolution ultrasound techniques, was adapted to characterize electrospun vascular grafts in vitro. Materials and Methods: Grafts were subjected to near physio-logic pulsatile pressure conditions, following the criteria stated in the international standard for cardiovascular implants-tubular vascular prostheses. Results: Internal pressure and external diameter variations of Poly(L-lactic acid) (PLLA) vascular grafts were obtained, allowing the assessment of mechanical parameters. Dynamic compliance was observed to decrease significantly in most cases, as transmural pressure increases. Conclusion: Mechanical characterization of small diameter electrospun PLLA vascular grafts was adequately achieved.