Polylactic acid core-shell fibres by coaxial electrospinning

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: The work presented in this dissertation describes the use of coaxial electrospinning of two miscible polymer solutions in the preparation of core-shell fibres with a semicrystalline core of poly(L-lactic acid) and an amorphous shell of poly(D,L-lactic acid). Additionally it describes using these fibres in the production of single polymer composite yarns and films. These materials can potentially be used in applications that require biodegradable and fibre-reinforced composite materials e.g. suture yarns. Traditional methods, such as TEM, when used to analyse the core-shell fibre structure were not successful with the polymer system used. A method was developed to validate core-shell fibre structure by selective dissolution of the shell material and correlating analyses of the separated components using differential scanning calorimetry (DSC) and optical rotation. The effects of solution concentration and flow rate on resultant core-shell fibre diameters were investigated. Core-solution flow rate was shown to be the most significant variable affecting the core and core-shell fibre diameters. A thermal processing window exists between the glass transition temperature of the amorphous PDLLA shell material and the crystalline melting temperature of the semicrystalline PLLA core material. Heating these core-shell fibres within this processing window resulted in flow and fusion of overlapping shells of these core-shell fibres at their surfaces while the fibrous core components remained intact and reinforced the resulting composite material. This approach was used to produce single polymer composite yarns and films. Thermal treatments on yarns were shown to increase crystallinity of the cores and therefore the modulus and yield strength of the fibres when compared to untreated yarns.AFRIKAANSE OPSOMMING: Die werk wat in hierdie tesis voorgelê word, beskryf die gebruik van koaksiale elektro-spinnery van twee wedersydsoplosbare polimeeroplossings in die vervaardiging van kern-skilvesels met ‘n gedeeltelik-kristallyne kern van poli-Lmelksuur (PLLA) en ‘n amorfe skil van poli-D,L-melksuur (PDLLA). Verder beskryf dit die gebruik van hierdie vesels in die vervaardiging van enkel-polimeer saamgestelde-materiaalgarings en -films. Hierdie materiale kan moontlik gebruik word in toepassings wat bio-afbreekbare en veselversterkte saamgestelde materiale vereis, soos byvoorbeeld chirurgiese steke. Die polimeervesels wat in hierdie studie gebruik is, kon nie gekaraktiseer word met behulp van transmissie-elektronmikroskopie (TEM), wat gewoonklik gebruik word in die bestudering van kern-skilvesels, nie. ‘n Alternatiewe karakteriseringsmetode is ontwikkel om te bevestig dat die gevormde vesels wel ‘n kern-skilstruktuur het. Hierdie metode het behels dat die skil van die kern-skilvesel selektief opgelos is, waarna beide komponente (d.i. kern en skilmateriale) bestudeer is met behulp van differensiële skanderingskalorimetrie en optiese rotasie. Die invloed van polimeeroplossingskonsentrasie en –vloeitempo op die gevormde kern-skilvesels is daarna ondersoek en die vloeitempo van die kernoplossing is geïdentifiseer as die prosesinsetwaarde wat die mees beduidende invloed het op die deursnee van die vesels. Daar bestaan ‘n temperatuurinterval tussen die glasoorgangstemperatuur van die amorfe PDLLA skilmateriaal en die kristallyne smeltpunt van die gedeeltelikkristallyne PLLA kernmateriaal. Verwerking van die kern-skilvesels by ‘n temperatuur binne hierdie interval het gelei tot vervloeiing en samesmelting van die oorvleuelende skille van die kern-skilvesels, terwyl die veselagtige kernkomponente van die vesels heel gebly het en opgetree het as versterking binne-in die saamgestelde materiaal wat gevorm het. Hierdie benadering is gebruik om enkelpolimeersaamgestelde- materiaalgarings en –films te vervaardig. ‘n Vergelykende studie tussen onbehandelde en hitte-behandelde enkel-polimeer-saamgesteldemateriaalgarings het aangetoon dat die hittebehandeling gelei het tot ‘n verhoging in die kristalliniteit van die veselkerne en daarom ook ‘n verhoging in die modulus en breeksterkte van die garings tot gevolg gehad het

Polylactic acid core-shell fibres by coaxial electrospinning

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: The work presented in this dissertation describes the use of coaxial electrospinning of two miscible polymer solutions in the preparation of core-shell fibres with a semicrystalline core of poly(L-lactic acid) and an amorphous shell of poly(D,L-lactic acid). Additionally it describes using these fibres in the production of single polymer composite yarns and films. These materials can potentially be used in applications that require biodegradable and fibre-reinforced composite materials e.g. suture yarns. Traditional methods, such as TEM, when used to analyse the core-shell fibre structure were not successful with the polymer system used. A method was developed to validate core-shell fibre structure by selective dissolution of the shell material and correlating analyses of the separated components using differential scanning calorimetry (DSC) and optical rotation. The effects of solution concentration and flow rate on resultant core-shell fibre diameters were investigated. Core-solution flow rate was shown to be the most significant variable affecting the core and core-shell fibre diameters. A thermal processing window exists between the glass transition temperature of the amorphous PDLLA shell material and the crystalline melting temperature of the semicrystalline PLLA core material. Heating these core-shell fibres within this processing window resulted in flow and fusion of overlapping shells of these core-shell fibres at their surfaces while the fibrous core components remained intact and reinforced the resulting composite material. This approach was used to produce single polymer composite yarns and films. Thermal treatments on yarns were shown to increase crystallinity of the cores and therefore the modulus and yield strength of the fibres when compared to untreated yarns.AFRIKAANSE OPSOMMING: Die werk wat in hierdie tesis voorgelê word, beskryf die gebruik van koaksiale elektro-spinnery van twee wedersydsoplosbare polimeeroplossings in die vervaardiging van kern-skilvesels met ‘n gedeeltelik-kristallyne kern van poli-Lmelksuur (PLLA) en ‘n amorfe skil van poli-D,L-melksuur (PDLLA). Verder beskryf dit die gebruik van hierdie vesels in die vervaardiging van enkel-polimeer saamgestelde-materiaalgarings en -films. Hierdie materiale kan moontlik gebruik word in toepassings wat bio-afbreekbare en veselversterkte saamgestelde materiale vereis, soos byvoorbeeld chirurgiese steke. Die polimeervesels wat in hierdie studie gebruik is, kon nie gekaraktiseer word met behulp van transmissie-elektronmikroskopie (TEM), wat gewoonklik gebruik word in die bestudering van kern-skilvesels, nie. ‘n Alternatiewe karakteriseringsmetode is ontwikkel om te bevestig dat die gevormde vesels wel ‘n kern-skilstruktuur het. Hierdie metode het behels dat die skil van die kern-skilvesel selektief opgelos is, waarna beide komponente (d.i. kern en skilmateriale) bestudeer is met behulp van differensiële skanderingskalorimetrie en optiese rotasie. Die invloed van polimeeroplossingskonsentrasie en –vloeitempo op die gevormde kern-skilvesels is daarna ondersoek en die vloeitempo van die kernoplossing is geïdentifiseer as die prosesinsetwaarde wat die mees beduidende invloed het op die deursnee van die vesels. Daar bestaan ‘n temperatuurinterval tussen die glasoorgangstemperatuur van die amorfe PDLLA skilmateriaal en die kristallyne smeltpunt van die gedeeltelikkristallyne PLLA kernmateriaal. Verwerking van die kern-skilvesels by ‘n temperatuur binne hierdie interval het gelei tot vervloeiing en samesmelting van die oorvleuelende skille van die kern-skilvesels, terwyl die veselagtige kernkomponente van die vesels heel gebly het en opgetree het as versterking binne-in die saamgestelde materiaal wat gevorm het. Hierdie benadering is gebruik om enkelpolimeersaamgestelde- materiaalgarings en –films te vervaardig. ‘n Vergelykende studie tussen onbehandelde en hitte-behandelde enkel-polimeer-saamgesteldemateriaalgarings het aangetoon dat die hittebehandeling gelei het tot ‘n verhoging in die kristalliniteit van die veselkerne en daarom ook ‘n verhoging in die modulus en breeksterkte van die garings tot gevolg gehad het

Dataset for the validation and use of DiameterJ an open source nanofiber diameter measurement tool

DiameterJ is an open source image analysis plugin for ImageJ. DiameterJ produces ten files for every image that it analyzes. These files include the images that were analyzed, the data to create histograms of fiber radius, pore size, fiber orientation, and summary statistics, as well as images to check the output of DiameterJ. DiameterJ was validated with 130 in silico-derived, digital, synthetic images and 24 scanning electron microscope (SEM) images of steel wire samples with a known diameter distribution. Once validated, DiameterJ was used to analyze SEM images of electrospun polymeric nanofibers, including a comparison of different segmentation algorithms. In this article, all digital synthetic images, SEM images, and their segmentations are included. Additionally, DiameterJ’s raw output files, and processed data is included for the reader. The data provided herein was used to generate the figures in DiameterJ: A Validated Open Source Nanofiber Diameter Measurement Tool [1], where more discussion can be found

Cell response to sterilized electrospun poly(-caprolactone) scaffolds to aid tendon regeneration in vivo

The functional replacement of tendon represents an unmet clinical need in situations of tendon rupture, tendon grafting, and complex tendon reconstruction, as usually there is a finite source of healthy tendon to use as donors. The microfibrous architecture of tendon is critical to the function of tendon. This study investigates the use of electrospun poly(ɛ‐caprolactone) scaffolds as potential biomaterial substitutes for tendon grafts. We assessed the performance of two electrospinning manufacturers (small‐ and large‐scale) and the effect of two sterilization techniques—gamma irradiation and ethanol submersion—on cell response to these electrospun scaffolds after their implantation into a murine tendon model. Cell infiltration and proliferation analyses were undertaken to determine the effect on cell response within the implant over a 6‐week period. Immunohistochemical analysis was performed to characterize inflammatory response and healing characteristics (proliferation, collagen deposition, myofibroblast activity, and apoptosis). Neither the sterilization techniques nor the manufacturer was observed to significantly affect the cell response to the scaffold. At each time point, cell response was similar to the autograft control. This suggests that ethanol submersion can be used for research purposes and that the scaffold can be easily reproduced by a large‐scale manufacturer. These results further imply that this electrospun scaffold may provide an alternative to autograft, thus eliminating the need for sourcing healthy tendon tissue from a secondary site. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 389–397, 2017