Vitamin D3-loaded electrospun cellulose acetate/polycaprolactone nanofibers: Characterization, in-vitro drug release and cytotoxicity studies

Vitamin D deficiency is nowa global health problem; despite several drug delivery systems for carrying vitaminD due to low bioavailability and loss bioactivity. Developing a new drug delivery system to deliver vitamin D3 is a strong incentive in the current study. Hence, an implantable drug delivery system (IDDS) was developed from the electrospun cellulose acetate (CA) and ε-polycaprolactone (PCL) nanofibrous membrane, in which the core of implants consists of vitamin D3-loaded CA nanofiber (CAVD) and enclosed in a thin layer of the PCL membrane (CAVD/PCL). CA nanofibrousmat loadedwith vitaminD3 at the concentrations of 6, 12, and 20% (w/w) of vitamin D3 were produced using electrospinning. The smooth and bead-free fibers with diameters ranged from 324 to 428 nm were obtained. The fiber diameters increased with an increase in vitamin D3 content. The controlled drug release profile was observed over 30-days, which fit with the zero-order model (R2 > 0.96) in the first stage. The mechanical properties of IDDS were improved. Young's modulus and tensile strength of CAVD/PCL (dry) were161 ± 14 and 13.07 ± 2.5 MPa, respectively. CA and PCL nanofibers are non-cytotoxic based on the results of the in-vitro cytotoxicity studies. This study can further broaden in-vivo study and provide a reference for developing a new IDDS to carry vitamin D3 in the future

PHB-PEO electrospun fiber membranes containing chlorhexidine for drug delivery applications

Fiber meshes of poly(hydroxybutyrate) (PHB) and poly(hydroxybutyrate)/poly(ethylene oxide) (PHB/PEO) with different concentrations of chlorhexidine (CHX) were prepared by electrospinning for assessment as a polymer based drug delivery system. The electrospun fibers were characterized at morphological, molecular and mechanical levels. The bactericidal potential of PHB and PHB/PEO electrospun fibers, with and without CHX, was investigated against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) by disk diffusion susceptibility tests. Electrospun fibers containing CHX exhibited bactericidal activity. PHB/PEO-1%CHX displayed higher CHX release levels and equivalent antibacterial activity when compared to PHB/PEO with 5 and 10 wt% CHX. Bactericidal performance of samples with 1 wt% CHX was assessed by Colony Forming Units (CFU), where reductions of 100% and 99.69% against E. coli and S. aureus were achieved, respectively.This work was supported by FEDER through the COMPETE Program and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Project PEST-C/FIS/UI607/2011 and PEST-C/QUI/UIO686/2011. The authors also thank funding from Matepro - Optimizing Materials and Processes", ref. NORTE-07-0124-FEDER-000037", co-funded by the "Programa Operacional Regional do Norte" (ON.2 - O Novo Norte), under the "Quadro de Referencia Estrategico Nacional" (QREN), through the "Fundo Europeu de Desenvolvimento Regional" (FEDER). D.M.C, JP and VS thanks the FCT for the, SFRH/BD/82411/2011, SFRH/BD/64901/2009 and SFRH/BPD/63148/2009 grants respectively. The authors also thank support from the COST Action MP1003, 2010 'European Scientific Network for Artificial Muscles' and to the COST Action MP1206 'Electrospun Nano-fibres for Bio inspired Composite Materials and Innovative Industrial Applications'. The authors also thank prof. Jose Luis Gomez Ribelles from the Unversidad Politecnica de Valencia, Spain, for interesting discussions on these issues

Endothelial Differentiation of Human Stem Cells Seeded onto Electrospun Polyhydroxybutyrate/Polyhydroxybutyrate-Co-Hydroxyvalerate Fiber Mesh

Tissue engineering is based on the association of cultured cells with structural matrices and the incorporation of signaling molecules for inducing tissue regeneration. Despite its enormous potential, tissue engineering faces a major challenge concerning the maintenance of cell viability after the implantation of the constructs. The lack of a functional vasculature within the implant compromises the delivery of nutrients to and removal of metabolites from the cells, which can lead to implant failure. In this sense, our investigation aims to develop a new strategy for enhancing vascularization in tissue engineering constructs. This study's aim was to establish a culture of human adipose tissue-derived stem cells (hASCs) to evaluate the biocompatibility of electrospun fiber mesh made of polyhydroxybutyrate (PHB) and its copolymer poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHB-HV) and to promote the differentiation of hASCs into the endothelial lineage. Fiber mesh was produced by blending 30% PHB with 70% PHB-HV and its physical characterization was conducted using scanning electron microscopy analysis (SEM). Using electrospinning, fiber mesh was obtained with diameters ranging 300 nm to 1.3 µm. To assess the biological performance, hASCs were extracted, cultured, characterized by flow cytometry, expanded and seeded onto electrospun PHB/PHB-HV fiber mesh. Various aspects of the cells were analyzed in vitro using SEM, MTT assay and Calcein-AM staining. The in vitro evaluation demonstrated good adhesion and a normal morphology of the hASCs. After 7, 14 and 21 days of seeding hASCs onto electrospun PHB/PHB-HV fiber mesh, the cells remained viable and proliferative. Moreover, when cultured with endothelial differentiation medium (i.e., medium containing VEGF and bFGF), the hASCs expressed endothelial markers such as VE-Cadherin and the vWF factor. Therefore, the electrospun PHB/PHB-HV fiber mesh appears to be a suitable material that can be used in combination with endothelial-differentiated cells to improve vascularization in engineered bone tissues

Nouvelle Structure d’Estimateurs à Horizon Glissant.Application à l’Estimation de Trajectoires de Débris SpatiauxPendant la Rentrée Atmosphérique

Space debris tracking during atmospheric re-entries will be a crucial challenge in the coming years,emphasized through many projects on space debris mitigation established by space agenciesworldwide. However, this problem appears to be complex, due to model errors and difficulties toproperly initialize the estimation algorithms, as a result of unknown dynamics of the debris and theirdisintegrations during the re-entries. A-to-be used estimator for this problem must be robust againstthese factors. The Moving Horizon Estimator (MHE) is known in the literature to be robust to modelerrors and bad initialization, and the PhD work has proved its ability to satisfy performances requiredby the debris tracking during the re-entries. However, its optimization-based framework induces alarge computation time. To overcome this, a new MHE structure which requires smaller computationtime than the classical MHE has been developed. This strategy, so-called “Moving Horizon Estimatorwith Pre-Estimation (MHE-PE)” takes into account model errors by using an auxiliary estimator ratherthan by searching for estimates of the process noise sequence over the horizon as in the classicalstrategy. A theorem which guarantees the stability of the dynamics of the estimation errors of theMHE-PE has also been proposed. Finally, performances of this structure in the context of 3D spacedebris tracking during the re-entries have been shown to be better than those obtained with classicalestimators including the MHE. In particular, without degrading accuracy of the estimates andconvergence of the estimator, the MHE-PE estimator requires smaller computation time than theMHE thanks to its small number of optimization variables.L’estimation de trajectoires de débris spatiaux pendant la rentrée atmosphérique est un défi majeurpour les prochaines années, renforcé par plusieurs projets liés à l'enlèvement de débris établis pardes agences spatiales de plusieurs pays. Cependant, ce problème s’avère complexe du fait deserreurs de modèle et des difficultés d’initialisation des algorithmes d’estimation induites par unemauvaise connaissance de la dynamique des débris suite à leur désintégration pendant la phase derentrée atmosphérique. Tout estimateur choisi doit donc être robuste vis-à-vis de ces facteurs.L’estimateur à horizon glissant (MHE) est reconnu dans la littérature pour être robuste vis-à-visd’erreurs de modèle et de mauvaise initialisation, et les travaux de thèse ont montré qu’il étaitadapté en termes de performances à la problématique de l’estimation des débris en phase derentrée. En revanche, il se fonde sur une stratégie d’optimisation qui requiert de fait un temps decalcul important. Pour pallier ce problème, une nouvelle structure d’estimation à horizon glissant aété développée, impliquant un temps de calcul faible nécessaire à l’application envisagée. Cettestratégie, appelée « estimateur à horizon glissant avec pré-estimation (MHE-PE)», prend en compteles erreurs de modèle via un estimateur auxiliaire, plutôt que de chercher à obtenir les estimées dubruit d’état sur l’horizon d’estimation, comme le fait la structure de l’estimateur MHE standard. Unthéorème garantissant la stabilité de la dynamique de l’erreur d’estimation du MHE-PE a par ailleursété proposé. Enfin, les performances de cette structure dans le cadre de l’estimation en troisdimensions des trajectoires de débris pendant la phase de rentrée se sont avérées meilleures quecelles observées avec des estimateurs classiques. En particulier, sans dégrader la précision et laconvergence de l’estimation, l’estimateur MHE-PE requiert moins de temps de calcul du fait dunombre réduit de paramètres à optimiser

ROTATION MATRIX SAMPLING SCHEME FOR MULTIDIMENSIONAL PROBABILITY DISTRIBUTION TRANSFER

This paper address the problem of rotation matrix sampling used for multidimensional probability distribution transfer. The distribution transfer has many applications in remote sensing and image processing such as color adjustment for image mosaicing, image classification, and change detection. The sampling begins with generating a set of random orthogonal matrix samples by Householder transformation technique. The advantage of using the Householder transformation for generating the set of orthogonal matrices is the uniform distribution of the orthogonal matrix samples. The obtained orthogonal matrices are then converted to proper rotation matrices. The performance of using the proposed rotation matrix sampling scheme was tested against the uniform rotation angle sampling. The applications of the proposed method were also demonstrated using two applications i.e., image to image probability distribution transfer and data Gaussianization