Author Correction: Preparation and modeling of three‐layered PCL/PLGA/PCL fibrous scaffolds for prolonged drug release (original) (raw)
Preparation and modeling of three‐layered PCL/PLGA/PCL fibrous scaffolds for prolonged drug release
Scientific Reports
The authors present the preparation procedure and a computational model of a three‐layered fibrous scaffold for prolonged drug release. The scaffold, produced by emulsion/sequential electrospinning, consists of a poly(d,l-lactic-co-glycolic acid) (PLGA) fiber layer sandwiched between two poly(ε-caprolactone) (PCL) layers. Experimental results of drug release rates from the scaffold are compared with the results of the recently introduced computational finite element (FE) models for diffusive drug release from nanofibers to the three-dimensional (3D) surrounding medium. Two different FE models are used: (1) a 3D discretized continuum and fibers represented by a simple radial one-dimensional (1D) finite elements, and (2) a 3D continuum discretized by composite smeared finite elements (CSFEs) containing the fiber smeared and surrounding domains. Both models include the effects of polymer degradation and hydrophobicity (as partitioning) of the drug at the fiber/surrounding interface. Th...
A Computational Model for Drug Release from PLGA Implant
Materials, 2018
Due to the relative ease of producing nanofibers with a core–shell structure, emulsion electrospinning has been investigated intensively in making nanofibrous drug delivery systems for controlled and sustained release. Predictions of drug release rates from the poly (d,l-lactic-co-glycolic acid) (PLGA) produced via emulsion electrospinning can be a very difficult task due to the complexity of the system. A computational finite element methodology was used to calculate the diffusion mass transport of Rhodamine B (fluorescent drug model). Degradation effects and hydrophobicity (partitioning phenomenon) at the fiber/surrounding interface were included in the models. The results are validated by experiments where electrospun PLGA nanofiber mats with different contents were used. A new approach to three-dimensional (3D) modeling of nanofibers is presented in this work. The authors have introduced two original models for diffusive drug release from nanofibers to the 3D surrounding medium ...
Heart Mechanical Model Based on Holzapfel Experiments
Learning and Analytics in Intelligent Systems
We have formulated orthotropic material model for human heart tissue based on experimental investigation of passive material properties of myocardium [1]. The Cauchy stress/stretch and shear stress/amount of shear relation curves are used, which are established experimentally under different loading conditions: biaxial extension and triaxial shear. The averaged curves obtained from all considered specimens in [1] are reconstructed and used in our FE computational model. A computational procedure for determination of stresses for current stretches and amounts of shear at integration points of the FE model is implemented in the code PAK. Compressibility condition is imposed to couple the normal stresses using a penalty formulation. Applicability and reliability of this material model is tested on simple 3D models and on a heart wall segment under passive conditions. This numerical model offers an accurate description of the ventricular mechanics and can be used in studying heart problems in order to improve medical treatment of heart diseases.
Frontiers in Bioengineering and Biotechnology
Mass transport represents the most fundamental process in living organisms. It includes delivery of nutrients, oxygen, drugs, and other substances from the vascular system to tissue and transport of waste and other products from cells back to vascular and lymphatic network and organs. Furthermore, movement is achieved by mechanical forces generated by muscles in coordination with the nervous system. The signals coming from the brain, which have the character of electrical waves, produce activation within muscle cells. Therefore, from a physics perspective, there exist a number of physical fields within the body, such as velocities of transport, pressures, concentrations of substances, and electrical potential, which is directly coupled to biochemical processes of transforming the chemical into mechanical energy and further internal forces for motion. The overall problems of mass transport and electrophysiology coupled to mechanics can be investigated theoretically by developing appropriate computational models. Due to the enormous complexity of the biological system, it would be almost impossible to establish a detailed computational model for the physical fields related to mass transport, electrophysiology, and coupled fields. To make computational models feasible for applications, we here summarize a concept of smeared physical fields, with coupling among them, and muscle mechanics, which includes dependence on the electrical potential. Accuracy of the smeared computational models, also with coupling to muscle mechanics, is illustrated with simple example, while their applicability is demonstrated on a liver model with tumors present. The last example shows that the introduced methodology is applicable to large biological systems.
Finite Element Models with Smeared Fields Within Tissue – A Review of the Current Developments
Learning and Analytics in Intelligent Systems
In this review we present the current stage and developments in the finite element modeling of mass transport by the smeared concept, introduced and conducted by the first author over several years. The basis of this methodology represents the formulation of a composite smeared finite element (CSFE). The CSFE consists of domains which can be at different length scale, where we have separate physical fields for each of the domains and with the corresponding governing laws. The continuum domains within the CSFE also include 1D transport represented in a continuum form by the appropriate transport tensors. The fields are coupled by the connectivity elements at each node, representing transport properties of the walls separating the domains. Formulation of this methodology and applications on various biomedical problems have been published in a number of recent publications. Here, we give an overview of these achievements and show some results of the current research.
Preparation and characterization of composites based on textile waste
The aim of this work was investigation of the possibilities of reusing of cotton textile waste, generated during the manufacture in textile industry, as reinforcement in production of composite materials.. The materials used as reinforcement for phenol phormaldehyde resin as matrix have been cotton fabric and cotton textile waste. The composites containing 60 % wt. reinforcement were manufactured by coventional process of compression molding (at pressure of 75 bar and temperature 160 o C). The mechanical and thermal properties of the produced materials based on textile waste were analyzed and compared to those of commonly used continuous fiber reinforced composites based on cotton fabric and phenolic resin. It was found that the composites based on cotton textile waste are more sensitive to processing cycles with respect to continuous fiber reinforced composites. Тhe mechanical properties of the composites based on cotton textile waste were lower for about 25%, although the thermal stability (determined by Martens method) for both composites reinforced with cotton fabric and with cotton textile waste was similar. The obtained results have shown that cotton textile waste could be reused for production of composites with acceptable mechanical properties, and they could be applied in many industries as construction material with moderate mechanical properties.
Variability of Milk Traits in Progeny Testing of the Simmental Bulls
2017
The data of the Institute for Animal Husbandry, Belgrade-Zemun have been used to investigate the variability of the properties that are observed in the progeny testing of Simmental bulls. The analysis is based on a sample of 7,845 first-calving heifers in the period 2007-2010. The tests included the following milk properties in the standard first lactation (305 days): milk yield (kg), milk fat content (%) and milk fat yield (kg). An analysis of the production traits of the first-calving heifers under control showed that their average milk yield was 4346.49 kg milk with 3.93% milk fat and yield of 171.11 kg of milk fat. Sires, years and calving season exhibited a highly significant impact (p<0.01) on all the milk properties observed in the progeny testing. Based on the BLUP solution, the rank of bulls for each trait was formed, and then the correlation coefficients of the rank, ranging from 0.402 (relationship between the yield of milk and milk fat content) to 0.989 (the relations...
European Journal of Pharmaceutical Sciences, 2018
Antibiotic containing polycaprolactone (PCL) fibers were produced by using three electrospinning methods: blend, emulsion and co-axial electrospinning (labeled as S1, S2 and S3, respectively). The profiles of drug release from three different systems were studied and antimicrobial properties of produced materials were evaluated. Morphology of the produced fibers was characterized and revealed that cefazolin-loaded PCL fibers had smaller diameter compared to neat PCL fibers, while the chemical interaction between the antibiotic and PCL showed that cefazolin neither had reacted with PCL phase, nor had degraded during the electrospinning process. The crystallinity and thermal characterization of fabricated fibers showed that the addition of cefazolin decreased the crystallinity of PCL. The results of the drug release behavior of the blend and co-axial electrospun fibers was on a higher level (~ 68 % and ~ 43 %, respectively) compared to the emulsion electrospun fibers (~ 5 %), after a period of 30 days. The obtained data had the best fitting with the first order model and the Higuchi model, while the Korsmeyer-Peppas model showed a Pseudo-Fickian diffusion of the drug. Antibacterial evaluations showed that cefazolin-loaded PCL fibers had better effects on Staphylococcus aureus compared to Escherichia coli during the treatment period and that the effect of the emulsion fibers was notably weaker than the other two studied systems. The aim of the study was to test different systems for control drug release of different dynamics, which will be applied for prevent bacterial accumulation when indwelling urinary catheters, applied for different periods of time.