Modifications of nonwoven polyethylene terephthalate fibrous matrices via NaOH hydrolysis: Effects on pore size, fiber diameter, cell seeding and proliferation

Cytotoxicity studies and antibacterial modification of poly(ethylene 2,5-furandicarboxylate) nonwoven

Novel poly(ethylene 2,5-furandicarboxylate) PEF nonwovens were produced by solution electrospinning and further modification. To improve the wettability of the hydrophobic nonwovens with water, they were treated with sodium hydroxide. Cytotoxicity tests carried out with human keratinocytes confirmed that the nonwovens did not have a toxic effect on healthy cells. The hydrophilicity of the sodium hydroxide treated nonwoven favored the adherence of the cells and their growth. In turn, the two-step modification of the nonwovens by reactions with (3-mercaptopropyl)methyldimethoxysilane and silver nitrate permitted to deposit silver particles on the fiber surfaces. The bacteria growth inhibition zones around the tested specimens were observed evidencing their antibacterial activity against Escherichia coli and Staphylococcus aureus.

Nano-Structured Ridged Micro-Filaments (≥100 µm Diameter) Produced Using a Single Step Strategy for Improved Bone Cell Adhesion and Proliferation in Textile Scaffolds

Textile scaffolds that are either 2D or 3D with tunable shapes and pore sizes can be made through textile processing (weaving, knitting, braiding, nonwovens) using microfilaments. However, these filaments lack nano-topographical features to improve bone cell adhesion and proliferation. Moreover, the diameter of such filaments should be higher than that used for classical textiles (10−30 µm) to enable adhesion and the efficient spreading of the osteoblast cell (>30 µm diameter). We report, for the first time, the fabrication of biodegradable nanostructured cylindrical PLLA (poly-L-Lactic acid) microfilaments of diameters 100 µm and 230 µm, using a single step melt-spinning process for straightforward integration of nano-scale ridge-like structures oriented in the fiber length direction. Appropriate drawing speed and temperature used during the filament spinning allowed for the creation of instabilities giving rise to nanofibrillar ridges, as observed by AFM (Atomic Force Microscopy). These micro-filaments were hydrophobic, and had reduced crystallinity and mechanical strength, but could still be processed into 2D/3D textile scaffolds of various shapes. Biological tests carried out on the woven scaffolds made from these nano-structured micro filaments showed excellent human bone cell MG 63 adhesion and proliferation, better than on smooth 30 µm- diameter fibers. Elongated filopodia of the osteoblast, intimately anchored to the nano-structured filaments, was observed. The filaments also induced in vitro osteogenic expression, as shown by the expression of osteocalcin and bone sialoprotein after 21 days of culture. This work deals with the fabrication of a new generation of nano-structured micro-filament for use as scaffolds of different shapes suited for bone cell engineering.

Incorporation of Elastin to Improve Polycaprolactone-Based Scaffolds for Skeletal Muscle via Electrospinning

Skeletal muscle regeneration is increasingly necessary, which is reflected in the increasing number of studies that are focused on improving the scaffolds used for such regeneration, as well as the incubation protocol. The main objective of this work was to improve the characteristics of polycaprolactone (PCL) scaffolds by incorporating elastin to achieve better cell proliferation and biocompatibility. In addition, two cell incubation protocols (with and without dynamic mechanical stimulation) were evaluated to improve the activity and functionality yields of the regenerated cells. The results indicate that the incorporation of elastin generates aligned and more hydrophilic scaffolds with smaller fiber size. In addition, the mechanical properties of the resulting scaffolds make them adequate for use in both bioreactors and patients. All these characteristics increase the biocompatibility of these systems, generating a better interconnection with the tissue. However, due to the low maturation achieved in biological tests, no differences could be found between the incubation with and without dynamic mechanical stimulation.

Impact of carboxylation and hydrolysis functionalisations on the anti-oil staining behaviour of textiles grafted with poly(N-isopropylacrylamide) hydrogel

Novel hydrogel-modified textiles have been prepared through photografting poly(N-isopropylacrylamide) (PNIPAAm) onto pristine and functionalised polyethylene terephthalate (PET) surfaces. In this work, two types of functionalisation, carboxylation (CPET) and hydrolysis (HPET), were performed to scrutinise the hydrogel grafting efficiency. Basic characterisation of the pristine, functionalised and grafted textiles was carried out via fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) analyses. Then, the functional characteristics of these samples were determined based on the oil staining performance. Functionalisation of the PET textiles via hydrolysis and carboxylation gives rise to different chemical reactivity and interactions on the PET surface. Impressively, the surface formed via hydrolysis functionalisation of PET was found to be more efficient compared to that formed via carboxylation, and the untreated one. The HPET surface was remarkably more hydrophilised and rougher than both the UPET and CPET surfaces. The accessibility of the –OH groups for hydrogen abstraction from HPET has a great impact on the hydrogel grafting onto the HPET surface. All the grafted textiles (PNIPAAm-g-UPET, PNIPAAm-g-CPET and PNIPAAm-g-HPET) demonstrated anti-oil staining behaviour at 27 °C. In particular, PNIPAAm-g-HPET textiles with a high degree of grafting (DG) exhibited the fastest rate for oil to de-stain from the surface. Moreover, the reversible transition of PNIPAAm hydrogels around the lower critical solution temperature (LCST) ∼ 32 °C from hydrophilic to hydrophobic generates switchable surfaces of the textiles with regard to the oil wettability. Specifically, PNIPAAm-g-HPET textiles also displayed the highest degree of wettability switching as a result of having the highest DG. Taken together, the PNIPAAm hydrogels grafted onto PET textiles were significantly enhanced though hydrolysis functionalisation and possessed excellent switchable surfaces toward oil-staining, having great potential to be used for applications in oil and water separation as well as smart textiles.

Functionalisation, especially via hydrolysis, has created efficient PNIPAAm hydrogels grafted onto PET textiles with superior anti-oil staining performance.

Layer-by-Layer Assembly of Polyelectrolyte Multilayer onto PET Fabric for Highly Tunable Dyeing with Water Soluble Dyestuffs

Poly(ethyleneterephthalate) (PET) is a multi-purpose and widely used synthetic polymer in many industrial fields because of its remarkable advantages such as low cost, light weight, high toughness and resistance to chemicals, and high abrasion resistance. However, PET suffers from poor dyeability due to its non-polar nature, benzene ring structure as well as high crystallinity. In this study, PET fabrics were firstly treated with an alkaline solution to produce carboxylic acid functional groups on the surface of the PET fabric, and then was modified by polyelectrolyte polymer through the electrostatic layer-by-layer self-assembly technology. The polyelectrolyte multilayer-deposited PET fabric was characterized using scanning electron microscopy SEM, contact angle, Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). The dyeability of PET fabrics before and after surface modification was systematically investigated. It showed that the dye-uptake of the polyelectrolyte multilayer-deposited PET fabric has been enhanced compared to that of the pristine PET fabric. In addition, its dyeability is strongly dependent on the surface property of the polyelectrolyte multilayer-deposited PET fabric and the properties of dyestuffs.

Tuning surface properties of poly(butylene terephthalate) melt blown fibers by alkaline hydrolysis and fluorination

The wetting properties of poly(butylene terephthalate) (PBT) melt blown fibers were tuned by alkaline hydrolysis and subsequent fluorination. Fiber mats were exposed to a NaOH methanol solution for controlled periods of time at several temperatures, resulting in surface hydrolysis (h-PBT). Subsequent simple solution chemistry was applied to the h-PBT fibers, leading to fluorination of the surface (f-PBT) and the transformation of the wetting properties of the material. Electron microscopy revealed that hydrolysis leads to a textured surface that is retained in the fluorinated product. Sessile drop wetting measurements demonstrated superhydrophilicity for the h-PBT fiber mats and sticky superhydrophobicity with the f-PBT fiber mat.

Composite PLA scaffolds reinforced with PDO fibers for tissue engineering

Novel composite scaffolds were produced using long continuous bidirectional fibers embedded in an electrospun matrix, with the aim of using them in soft tissue engineering applications. The fibers are of polydioxanone and the matrix of polylactic acid. The novel manufacturing method consists of direct electrospinning performed on both sides of a collector that supports the already arranged fibers. The scaffolds were tested in vitro using 3T3 mouse fibroblasts as-obtained or functionalized with biotin or poly (dopamine). Functionalization did not significantly affect cells attachment, metabolic activity, or proliferation, but poly (dopamine) was proven to be effective in inducing hydrophilicity to the surface.