Fabrication and Characterization of PCL/PLGA Coaxial and Bilayer Fibrous Scaffolds for Tissue Engineering

Effect of adipose-derived stem cells seeding and surgical prefabrication on composite scaffold vascularization

The study aimed to evaluate an angiogenic effect of adipose-derived stem cells (ASCs) seeding and surgical prefabrication (placing a vascular pedicle inside the scaffold) on developed composite scaffolds made of poly-ε-caprolactone (PCL), β-tricalcium phosphate (β-TCP), and poly (lactic-co-glycolic acid) (PLGA) (PCL+β-TCP+PLGA). Moreover, we aimed to compare our data with previously tested PCL scaffolds to assess whether the new material has better angiogenic properties. The study included 18 inbred male WAG rats. There were three scaffold groups (six animals each): with non-seeded PCL+β-TCP+PLGA scaffolds, with PCL+β-TCP+PLGA scaffolds seeded with ASCs and with PCL+β-TCP+PLGA scaffolds seeded with ASCs and osteogenic-induced. Each rat was implanted with two scaffolds in the inguinal region (one prefabricated and one non-prefabricated). After 2 months from implantation, the scaffolds were explanted, and vessel density was determined by histopathological examination. Prefabricated ASC-seeded PCL+β-TCP+PLGA scaffolds promoted greater vessel formation than non-seeded scaffolds (19.73 ± 5.46 vs 12.54 ± 0.81; p = .006) and those seeded with osteogenic-induced ASCs (19.73 ± 5.46 vs 11.87±2.21; p = .004). The developed composite scaffold promotes vessel formation more effectively than the previously described PCL scaffold.

Recent Methods for Modifying Mechanical Properties of Tissue-Engineered Scaffolds for Clinical Applications

The limited regenerative capacity of the human body, in conjunction with a shortage of healthy autologous tissue, has created an urgent need for alternative grafting materials. A potential solution is a tissue-engineered graft, a construct which supports and integrates with host tissue. One of the key challenges in fabricating a tissue-engineered graft is achieving mechanical compatibility with the graft site; a disparity in these properties can shape the behaviour of the surrounding native tissue, contributing to the likelihood of graft failure. The purpose of this review is to examine the means by which researchers have altered the mechanical properties of tissue-engineered constructs via hybrid material usage, multi-layer scaffold designs, and surface modifications. A subset of these studies which has investigated the function of their constructs in vivo is also presented, followed by an examination of various tissue-engineered designs which have been clinically translated.

Biomechanical Behaviors and Degradation Properties of Multilayered Polymer Scaffolds: The Phase Space Method for Bile Duct Design and Bioengineering

This article reports the electrospinning technique for the manufacturing of multilayered scaffolds for bile duct tissue engineering based on an inner layer of polycaprolactone (PCL) and an outer layer either of a copolymer of D,L-lactide and glycolide (PLGA) or a copolymer of L-lactide and ε-caprolactone (PLCL). A study of the degradation properties of separate polymers showed that flat PCL samples exhibited the highest resistance to hydrolysis in comparison with PLGA and PLCL. Irrespective of the liquid-phase nature, no significant mass loss of PCL samples was found in 140 days of incubation. The PLCL- and PLGA-based flat samples were more prone to hydrolysis within the same period of time, which was confirmed by the increased loss of mass and a significant reduction of weight-average molecular mass. The study of the mechanical properties of developed multi-layered tubular scaffolds revealed that their strength in the longitudinal and transverse directions was comparable with the values measured for a decellularized bile duct. The strength of three-layered scaffolds declined significantly because of the active degradation of the outer layer made of PLGA. The strength of scaffolds with the PLCL outer layer deteriorated much less with time, both in the axial (p-value = 0.0016) and radial (p-value = 0.0022) directions. A novel method for assessment of the physiological relevance of synthetic scaffolds was developed and named the phase space approach for assessment of physiological relevance. Two-dimensional phase space (elongation modulus and tensile strength) was used for the assessment and visualization of the physiological relevance of scaffolds for bile duct bioengineering. In conclusion, the design of scaffolds for the creation of physiologically relevant tissue-engineered bile ducts should be based not only on biodegradation properties but also on the biomechanical time-related behavior of various compositions of polymers and copolymers.

Investigation of Cell Adhesion and Cell Viability of the Endothelial and Fibroblast Cells on Electrospun PCL, PLGA and Coaxial Scaffolds for Production of Tissue Engineered Blood Vessel

Endothelialization of artificial scaffolds is considered an effective strategy for increasing the efficiency of vascular transplantation. This study aimed to compare the biophysical/biocompatible properties of three different biodegradable fibrous scaffolds: Poly (ɛ-caprolactone) (PCL) alone, Poly Lactic-co-Glycolic Acid (PLGA) alone (both processed using Spraybase^® electrospinning machine), and Coaxial scaffold where the fiber core and sheath was made of PCL and PLGA, respectively. Scaffold structural morphology was assessed by scanning electron microscope and tensile testing was used to investigate the scaffold tension resistance over time. Biocompatibility studies were carried out with human umbilical vein endothelial cells (HUVEC) and human vascular fibroblasts (HVF) for which cell viability (and cell proliferation over a 4-day period) and cell adhesion to the scaffolds were assessed by cytotoxicity assays and confocal microscopy, respectively. Our results showed that all biodegradable polymeric scaffolds are a reliable host to adhere and promote proliferation in HUVEC and HVF cells. In particular, PLGA membranes performed much better adhesion and enhanced cell proliferation compared to control in the absence of polymers. In addition, we demonstrate here that these biodegradable membranes present improved mechanical properties to construct potential tissue-engineered vascular graft.

Potential nanocarrier-mediated miRNA-based therapy approaches for multiple sclerosis

Multiple sclerosis (MS) is an autoimmune neuroinflammatory disorder attributed to neurodegeneration and demyelination, resulting in neurological impairment. miRNA has a significant role in biological processes in MS. In this review, we focus on the feasibility of delivering miRNAs through nanoformulations for managing MS. We provide a brief discussion of miRNA synthesis and evidence for miRNA dysregulation in MS. We also highlight formulation strategies and resulting technologies for the effective delivery of miRNAs through nanocarrier systems for achieving high therapeutic benefits.

A review on biodegradable biliary stents: materials and future trends

Biliary stricture is defined as the reduction and narrowing of the bile duct lumen, which can be caused by many factors such as cancer and inflammation. Biliary stent placement can effectively alleviate benign and malignant biliary strictures. However, the commonly used plastic or metallic biliary stents are far from ideal and do not satisfy all clinical requirements，although several types of biodegradable biliary stents have been developed and used clinically. In this review, we summarized current development status of biodegradable stents with the emphasis on the stent materials. We also presented the future development trends based on the published literature.

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Summary of current development status of bioresorbable biliary stents with the emphasis on the stent materials.

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The future development trends based on the published literature.

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The advantages of bioresorbable biliary stents compared with metallic and plastic biliary stents.

Study of the Filtration Performance of Multilayer and Multiscale Fibrous Structures

As the incidence of small-diameter particles in the air has increased in recent decades, the development of efficient filtration systems is both urgent and necessary. Nanotechnology, more precisely, electrospun nanofibres, has been identified as a potential solution for this issue, since it allows for the production of membranes with high rates of fibres per unit area, increasing the probability of nanoparticle collision and consequent retention. In the present study, the electrospinning technique of polyamide nanofibre production was optimized with the variation of parameters such as polymer concentration, flow rate and needle diameter. The optimized polyamide nanofibres were combined with polypropylene and polyester microfibres to construct a multilayer and multiscale system with an increased filtration efficiency. We observed that the penetration value of the multilayer system with a PA membrane in the composition, produced for 20 min in the electrospinning, is 2.7 times smaller than the penetration value of the system with the absence of micro and nano fibers.