Effects of Solution Viscosity on PLLA Porous Microtubes Fabricated by Core-Sheath Electrospinning

2021 ◽  
Author(s):  
Yingge Zhou ◽  
Imtiaz Qavi ◽  
George Z. Tan
Keyword(s):  
Lactic Acid ◽  
Product Development ◽  
Biomedical Applications ◽  
Viscosity Ratio ◽  
Tube Wall ◽  
Solution Viscosity ◽  
Outer Diameter ◽  
The Core ◽  
Core Solution ◽  
Fenestrated Capillary

Abstract Core-sheath electrospinning is a rapid microfabrication process for creating multi-layer polymer microfibers. This paper presents a process based on core-sheath electrospinning to fabricate poly(L-lactic acid) (PLLA) microtubes with nanopores on the tube wall. The morphology of the microtubes mimics human fenestrated capillary vessels. This study investigates the effects of the viscosities of the core and the sheath solutions on the microtube outer diameter and the nanopore size. The core solution shows a dominating influence on the microtube diameter. At the same core solution viscosity level, the microtube diameter is negatively correlated to the core-to-sheath viscosity ratio. The pore size is positively correlated to the microtube diameter. Understanding the effects of solution viscosity on microtube morphology is the prerequisite for process control and microtube product development for future biomedical applications.

scholarly journals Fabrication of Nanopores Polylactic Acid Microtubes by Core-Sheath Electrospinning for Capillary Vascularization

Biomimetics ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 15
Author(s):  
Yingge Zhou ◽  
Dilshan Sooriyaarachchi ◽  
George Z. Tan
Keyword(s):  
Polylactic Acid ◽  
Electrospinning Process ◽  
Medical Applications ◽  
Vascular Networks ◽  
The Core ◽  
Pump Rate ◽  
Core Solution ◽  
Substantial Progress ◽  
Vascular Channels ◽  
Fenestrated Capillary

There has been substantial progress in tissue engineering of biological substitutes for medical applications. One of the major challenges in development of complex tissues is the difficulty of creating vascular networks for engineered constructs. The diameter of current artificial vascular channels is usually at millimeter or submillimeter level, while human capillaries are about 5 to 10 µm in diameter. In this paper, a novel core-sheath electrospinning process was adopted to fabricate nanoporous microtubes to mimic the structure of fenestrated capillary vessels. A mixture of polylactic acid (PLA) and polyethylene glycol (PEO) was used as the sheath solution and PEO was used as the core solution. The microtubes were observed under a scanning electron microscope and the images were analyzed by ImageJ. The diameter of the microtubes ranged from 1–8 microns. The diameter of the nanopores ranged from 100 to 800 nm. The statistical analysis showed that the microtube diameter was significantly influenced by the PEO ratio in the sheath solution, pump rate, and the viscosity gradient between the sheath and the core solution. The electrospun microtubes with nanoscale pores highly resemble human fenestrated capillaries. Therefore, the nanoporous microtubes have great potential to support vascularization in engineered tissues.

scholarly journals Towards Manufacturing of Ultrafine-Laminated Structures in Metallic Tubes by Accumulative Extrusion Bonding

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 389
Author(s):  
Matthew R. Standley ◽  
Marko Knezevic
Keyword(s):  
Solid State ◽  
Wall Thickness ◽  
Complex Geometry ◽  
Tube Wall ◽  
Film Theory ◽  
Radial Strain ◽  
Surface Preparation ◽  
Grain Structure ◽  
Outer Diameter ◽  
Laminated Structures

A severe plastic deformation process, termed accumulative extrusion bonding (AEB), is conceived to steady-state bond metals in the form of multilayered tubes. It is shown that AEB can facilitate bonding of metals in their solid-state, like the process of accumulative roll bonding (ARB). The AEB steps involve iterative extrusion, cutting, expanding, restacking, and annealing. As the process is iterated, the laminated structure layer thicknesses decrease within the tube wall, while the tube wall thickness and outer diameter remain constant. Multilayered bimetallic tubes with approximately 2 mm wall thickness and 25.25 mm outer diameter of copper-aluminum are produced at 52% radial strain per extrusion pass to contain eight layers. Furthermore, tubes of copper-copper are produced at 52% and 68% strain to contain two layers. The amount of bonding at the metal-to-metal interfaces and grain structure are measured using optical microscopy. After detailed examination, only the copper-copper bimetal deformed to 68% strain is found bonded. The yield strength of the copper-copper tube extruded at 68% improves from 83 MPa to 481 MPa; a 480% increase. Surface preparation, as described by the thin film theory, and the amount of deformation imposed per extrusion pass are identified and discussed as key contributors to enact successful metal-to-metal bonding at the interface. Unlike in ARB, bonding in AEB does not occur at ~50% strain revealing the significant role of more complex geometry of tubes relative to sheets in solid-state bonding.

scholarly journals Stereocomplex Polylactide for Drug Delivery and Biomedical Applications: A Review

Molecules ◽  
2021 ◽  
Vol 26 (10) ◽  
pp. 2846
Author(s):  
Seung Hyuk Im ◽  
Dam Hyeok Im ◽  
Su Jeong Park ◽  
Justin Jihong Chung ◽  
Youngmee Jung ◽  
...  
Keyword(s):  
Drug Delivery ◽  
Lactic Acid ◽  
Self Assembly ◽  
Biomedical Applications ◽  
Drug Carrier ◽  
Micelle Formation ◽  
Weak Stability ◽  
Critical Fields ◽  
Physical Strength ◽  
Anti Cancer

Polylactide (PLA) is among the most common biodegradable polymers, with applications in various fields, such as renewable and biomedical industries. PLA features poly(D-lactic acid) (PDLA) and poly(L-lactic acid) (PLLA) enantiomers, which form stereocomplex crystals through racemic blending. PLA emerged as a promising material owing to its sustainable, eco-friendly, and fully biodegradable properties. Nevertheless, PLA still has a low applicability for drug delivery as a carrier and scaffold. Stereocomplex PLA (sc-PLA) exhibits substantially improved mechanical and physical strength compared to the homopolymer, overcoming these limitations. Recently, numerous studies have reported the use of sc-PLA as a drug carrier through encapsulation of various drugs, proteins, and secondary molecules by various processes including micelle formation, self-assembly, emulsion, and inkjet printing. However, concerns such as low loading capacity, weak stability of hydrophilic contents, and non-sustainable release behavior remain. This review focuses on various strategies to overcome the current challenges of sc-PLA in drug delivery systems and biomedical applications in three critical fields, namely anti-cancer therapy, tissue engineering, and anti-microbial activity. Furthermore, the excellent potential of sc-PLA as a next-generation polymeric material is discussed.

Polyurethane/poly(d,l-lactic acid) scaffolds based on supercritical fluid technology for biomedical applications: Studies with L929 cells

2019 ◽  
Vol 96 ◽  
pp. 539-551 ◽  
Author(s):  
Michele Savaris ◽  
Charlene Silvestrin Celi Garcia ◽  
Mariana Roesch-Ely ◽  
João Antonio Pêgas Henriques ◽  
Venina dos Santos ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Supercritical Fluid ◽  
Biomedical Applications ◽  
L929 Cells ◽  
Supercritical Fluid Technology

scholarly journals Microbiological aspects of biogenic amines formation in ripening cheeses

2007 ◽  
Vol 55 (4) ◽  
pp. 23-28
Author(s):  
Olga Cwiková ◽  
Vlastimil Dohnal ◽  
Tomáš Komprda
Keyword(s):  
Lactic Acid ◽  
Lactic Acid Bacteria ◽  
Biogenic Amines ◽  
Starter Cultures ◽  
Part C ◽  
The Core ◽  
Edge Part ◽  
Core Part ◽  
Hard Cheese ◽  
Microbiological Aspects

Counts of lactic acid bacteria (LAB), total anaerobes and enterococci were determined in the course of ripening in the edge part (E) and the core part (C) of Dutch-type semi-hard cheese produced with different fat content (30 and 45 %) by two different producers (H and R) using two different starter cultures (L and Y). Counts of LAB at the beginning of ripening (day 0) in H producer´s samples were higher (P < 0,01) in comparison with the R producer´s ones. Count of enterococci was the highest (P < 0,05) at the end of the ripening (176th day) in sample R30YE. Higher (P < 0,01) enterococci counts were in R producer´s cheeses (in comparison with the H producer´s ones). Enterococci contamination was higher (P < 0,05) in E-samples than C-samples. Content of the sum of all BA in cheese was negatively correlated (P < 0,05) with counts of lactic acid bacteria (r = –0,24) and counts of total anaerobes (r = –0,23). No correlation between the sum of BA content and enterococci counts was found.

scholarly journals Phonon Abundance-Stiffness-Lifetime Transition from the Mode of Heavy Water to Its Confinement and Hydration

2018 ◽  
Author(s):  
Chang Sun
Keyword(s):  
Molecular Dynamics ◽  
Heavy Water ◽  
Surface Stress ◽  
Vibration Mode ◽  
Hydration Shell ◽  
Solution Viscosity ◽  
The Core ◽  
Spatially Resolved ◽  
Skin Formation ◽  
Phonon Lifetime

<div>A combination of the temporally- and spatially-resolved phonon spectroscopy has enabled calibration of hydrogen bond transition from the vibration mode of heavy water to the core-shelled nanodroplet and the sub-nanosized ionic hydration shell in terms of phonon abundance-lifetime-stiffness. It is uncovered that charge injection by salt solvation and skin formation by molecular undercoordination (often called confinement) share the same supersolidity of H–O (D–O as a probe) bond contraction, O:H elongation, and electron polarization. The bond transition stems the solution viscosity, surface stress, and slows down the molecular dynamics. The skin reflection further hinders phonon energy dissipation and thus lengthens the phonon lifetime of the nanodroplet.</div>

Solvent Assisted Coaxial-Electrospun Poly Methyl Methacrylate Polymer and Study of Resultant Fibers

2020 ◽  
Vol 18 (12) ◽  
pp. 905-909
Author(s):  
Arjun Satheesh ◽  
A. A. Alagiriswamy ◽  
S. Devanand ◽  
S. Nithiyanantham
Keyword(s):  
Methyl Methacrylate ◽  
Sem Analysis ◽  
Fiber Formation ◽  
Dimethyl Formamide ◽  
Poly Methyl Methacrylate ◽  
The Core ◽  
Pure Solvent ◽  
Core Solution ◽  
Polymer Dispersions

Electrospinning of dispersions with higher viscosity and limited flow may be carried out, based on the solvent assisted coaxial technique, where the flow of the core dispersion is supported by a free flowing sheath solvent. In the present work, the sheath solvents used are chloroform, toluene and dimethyl formamide and we discuss the fiber formation of Poly Methyl Methacrylate (PMMA) (dispersion-25 wt%). PMMA dispersed in chloroform is taken as the core solution and the sheath is pure solvent. The In-Situ effect of different sheath solvents in fiber formation at two different tip to collector distances are studied. The fibers formed are subjected to SEM analysis and the characteristics are analysed. The fiber formation of high viscos polymer dispersions makes the same materials subjectable to electrospinning and further applications.

scholarly journals Stability of Engineered Micro or Nanobubbles for Biomedical Applications

Pharmaceutics ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 1089
Author(s):  
Beomjin Park ◽  
Semi Yoon ◽  
Yonghyun Choi ◽  
Jaehee Jang ◽  
Soomin Park ◽  
...  
Keyword(s):  
Drug Delivery ◽  
Biomedical Applications ◽  
Ultrasonic Field ◽  
Nanometer Scale ◽  
Factors Affecting ◽  
The Core ◽  
Bubble Structure ◽  
The Stability ◽  
The Relationship

A micro/nanobubble (MNB) refers to a bubble structure sized in a micrometer or nanometer scale, in which the core is separated from the external environment and is normally made of gas. Recently, it has been confirmed that MNBs can be widely used in angiography, drug delivery, and treatment. Thus, MNBs are attracting attention as they are capable of constructing a new contrast agent or drug delivery system. Additionally, in order to effectively use an MNB, the method of securing its stability is also being studied. This review highlights the factors affecting the stability of an MNB and the stability of the MNB within the ultrasonic field. It also discusses the relationship between the stability of the bubble and its applicability in vivo.

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