Chitosan-polycaprolactone Mixtures as Biomaterials: Influence of Surface Morphology on Cellular Activity

Chitosan, a naturally occurring polysaccharide has excellent biocompatibility, positive charge and reactive functional groups that help regulate cellular activity, antibacterial properties, and low cost. However, inadequate mechanical strength and incomplete understanding of cell-material interactions have limited its success. Polycaprolactone (PCL) is synthetic polyester that is easy to process, with excellent mechanical properties and tailorable physicochemical properties but lacks bioregulatory properties. Chitosan and PCL were homogenously dissolved in a unique acetic-acid water mixture to obtain a composite that has good biomechanical properties. Uniform membranes were obtained by drying the solutions at 50°C and several processes were explored for forming porous scaffolds, including freeze-extraction and freeze-drying. Membranes were tested for tensile properties under dry/wet, and monotonic/cyclical loading conditions. Support for adhesion and growth of eukaryotes (mouse embryonic fibroblasts) and prokaryotes (Streptococcus mutans and Actinobacillus actinomycetemcomitans) were evaluated in vitro. Cytocompatibility and support for vasculature of scaffolds was tested using CAM assay. Degradation characteristics were evaluated in PBS over 4 weeks. Physicochemical properties and interactions in these mixtures were characterized by DSC, DMTA, FTIR, WAXD, SEM, AFM and EFM. Findings and Conclusions: Hydrophilic chitosan and hydrophobic PCL were successfully mixed in different mass ratios by dissolution in a unique water-acetic acid mixture. There was no chemical reaction between chitosan and PCL in the prepared mixtures. However, the crystallinity was reduced suggesting partial miscibility between these polymers. Tensile properties of mixture membranes were comparable or better than those of chitosan membranes. These membranes also showed improved viability and spreading of mouse embryonic fibroblasts as well as Gram-positive and Gram-negative bacteria. 3D scaffolds were non-toxic and supported blood vessel formation on CAMs. Evaluation of surface showed increased roughness and positive charge density on the mixtures. Observed changes in biological activity of chitosan were attributed to surface characteristics due to absence of other physical or chemical changes. Therefore, it maybe concluded that higher roughness and cationic charge density favor cellular colonization.School of Chemical Engineerin

Aortic Dissection with Hemopericardium and Thrombosed Left Common Iliac Artery Presenting as Acute Limb Ischemia: A Case Report and Review

Abstract Aim: An aortic dissection is an uncommon serious condition, which usually presents with chest pain or upper back pain. Symptoms of aortic dissection may mimic those of other diseases, often leading to delay in diagnosis. Methods: We report an unusual case of aortic dissection with hemopericardium and thrombosed left common iliac artery presenting as acute limb ischemia. Conclusion: Maintaining a high index of clinical suspicion for aortic pathology could possibly lead to identification and timely management of a greater number of patients who have atypical presentations. This would be especially true for patients who have catastrophic presentations with unexplained symptoms

Sclerosing Encapsulating Peritonitis (Abdominal Cocoon) after Abdominal Hysterectomy

Sclerosing encapsulating peritonitis (SEP) is a poorly understood and rarely documented cause of small bowel obstruction. Although recurrent peritonitis has been reported as the main contributory factor leading to secondary SEP, the pathogenesis of primary (idiopathic) SEP is still uncertain

Surface modification of a biodegradable composite by UV laser ablation : in vitro biological performance

Melt blends of chitosan and biodegradable aliphatic polyester have been physically and biologically studied, presenting great potential for biomedical applications. Structurally, poly(butylene succinate)–chitosan (PBS/Cht) composite scaffolds are covered by a thin PBS layer, preventing the desired interaction of cells/tissues with the chitosan particules. In the present work, a selective and controlled ablation of this skin layer was induced by UV laser processing. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF–SIMS) data demonstrated an increment of chitosan components and others resulting from the laser ablation process. The biological activity (i.e. cell viability and proliferation) on the inner regions of the composite scaffolds is not significantly different from those of the external layer, despite the observed differences in surface roughness (determined by interferometric optical profilometry) and wettability (water contact angle). However, the morphology of human osteoblastic cells was found to be considerably different in the case of laser-processed samples, since the cells tend to aggregate in multilayer columnar structures, preferring the PBS surface and avoiding the chitosan-rich areas. Thus, UV laser ablation can be considered a model technique for the physical surface modification of biomaterials without detrimental effects on cellular activity.This work was partially supported by the European Union Integrated Project GENOSTEM (LSH-STREP-CT-2003-503161), the European Union Network of Excellence EXPERTISSUES (NMP3-CT-2004-500283), the Interreg III Project PROTEUS (SP1P151/03) and Xunta de Galicia (Consolidacion 2006/12). The Portuguese Foundation for Science and Technology is also acknowledged for a PhD grant to A.M. (SFRH/BD/24382/2005). The authors wish to thank C. Serra from CACTI of the University of Vigo for the XPS and ToF-SIMS measurements

Enhancement of Mechanical and Thermal Properties of Polycaprolactone/Chitosan Blend by Calcium Carbonate Nanoparticles

This study investigates the effects of calcium carbonate (CaCO3) nanoparticles on the mechanical and thermal properties and surface morphology of polycaprolactone (PCL)/chitosan nanocomposites. The nanocomposites of PCL/chitosan/CaCO3 were prepared using a melt blending technique. Transmission electron microscopy (TEM) results indicate the average size of nanoparticles to be approximately 62 nm. Tensile measurement results show an increase in the tensile modulus with CaCO3 nanoparticle loading. Tensile strength and elongation at break show gradual improvement with the addition of up to 1 wt% of nano-sized CaCO3. Decreasing performance of these properties is observed for loading of more than 1 wt% of nano-sized CaCO3. The thermal stability was best enhanced at 1 wt% of CaCO3 nanoparticle loading. The fractured surface morphology of the PCL/chitosan blend becomes more stretched and homogeneous in PCL/chitosan/CaCO3 nanocomposite. TEM micrograph displays good dispersion of CaCO3 at lower nanoparticle loading within the matrix

Bioactive glass/polymer composite scaffolds mimicking bone tissue

The aim of this work was the preparation and characterization of scaffolds with mechanical and functional properties able to regenerate bone. Porous scaffolds made of chitosan/gelatin (POL) blends containing different amounts of a bioactive glass (CEL2), as inorganic material stimulating biomineralization, were fabricated by freeze-drying. Foams with different compositions (CEL2/POL 0/100; 40/60; 70/30 wt %/wt) were prepared. Samples were crosslinked using genipin (GP) to improve mechanical strength and thermal stability. The scaffolds were characterized in terms of their stability in water, chemical structure, morphology, bioactivity, and mechanical behavior. Moreover, MG63 osteoblast-like cells and periostealderived stem cells were used to assess their biocompatibility. CEL2/POL samples showed interconnected pores having an average diameter ranging from 179 6 5 lm for CEL2/POL 0/100 to 136 6 5 lm for CEL2/POL 70/30. GP-crosslinking and the increase of CEL2 amount stabilized the composites to water solution (shown by swelling tests). In addition, the SBF soaking experiment showed a good bioactivity of the scaffold with 30 and 70 wt % CEL2. The compressive modulus increased by increasing CEL2 amount up to 2.1 6 0.1 MPa for CEL2/POL 70/30. Dynamical mechanical analysis has evidenced that composite scaffolds at low requencies showed an increase of storage and loss modulus with increasing frequency; furthermore, a drop of E0 and E00 at 1 Hz was observed, and for higher frequencies both moduli increased again. Cells displayed a good ability to interact with the different tested scaffolds which did not modify cell metabolic activity at the analyzed points. MTT test proved only a slight difference between the two cytotypes analyze

Marine Polysaccharides in Pharmaceutical Applications: An Overview

The enormous variety of polysaccharides that can be extracted from marine plants and animal organisms or produced by marine bacteria means that the field of marine polysaccharides is constantly evolving. Recent advances in biological techniques allow high levels of polysaccharides of interest to be produced in vitro. Biotechnology is a powerful tool to obtain polysaccharides from a variety of micro-organisms, by controlling the growth conditions in a bioreactor while tailoring the production of biologically active compounds. Following an overview of the current knowledge on marine polysaccharides, with special attention to potential pharmaceutical applications and to more recent progress on the discovering of new polysaccharides with biological appealing characteristics, this review will focus on possible strategies for chemical or physical modification aimed to tailor the final properties of interest

Saddle pulmonary embolism: right ventricular strain an indicator for early surgical approach

Current mainstay treatment for pulmonary embolism (PE) includes oral anticoagulation, thrombolytic therapy, catheter embolectomy and acute surgical embolectomy. Surgical embolectomy is reserved for hemodynamically unstable patients (cardiogenic shock, cardiac arrest) and contraindication to thrombolytic therapy. We report a case of saddle PE in a young female with echocardiographic signs of right ventricular (RV) dysfunction who underwent early acute surgical embolectomy with a positive outcome. It would be beneficial to use bedside echocardiography even in hemodynamically stable patients to determine RV strain as this could act as an early indicator suggesting the escalation of therapy