Effect of low-temperature plasma treatment of electrospun polycaprolactone fibrous scaffolds on calcium carbonate mineralisation

Surface-Modified Diopside-Reinforced PCL Biopolymer Composites with Enhanced Interfacial Strength and Mechanical Properties for Orthopedic Applications

The phase separation of ceramics in a biopolymer matrix makes it challenging to achieve satisfactory mechanical properties required for orthopedic applications. It has been found that silane coupling agents can modify the surface of the bioceramic phase by forming a molecular bridge between the polymer and the ceramic, resulting in improved interfacial strength and adhesion. Therefore, in the present study, silane-modified diopside (DI) ceramic and ε-polycaprolactone (PCL) biopolymer composites were fabricated by injection molding method. The silane modification of DI resulted in their uniform dispersion in the PCL matrix, whereas agglomeration was found in composites containing unmodified DI. The thermal stability of the silane-modified DI-containing composites also increased. The Young's modulus of the composite containing 50% w/w DI modified by 3% w/w silane increased by 103% compared to composites containing 50% w/w unmodified DI. The biodegradation of the unmodified composites was significantly high, indicating their weak interfacial strength with the PCL matrix (p ≤ 0.001). The osteoconductive behavior of the composites was also validated by in vitro cell-material studies. Overall, our findings supported that the silane-modified composites have improved surface roughness, mechanical, and osteoconductive properties compared to the unmodified composite and have the potential for orthopedic applications.

The structure and selected properties of poly(ε-caprolactone)-based biodegradable composites with high calcium carbonate concentration

The article refers to new polycaprolactone (PCL) composites with high concentration of calcium carbonate (CC). The objective of the present study was the manufacturing of PCL-based biodegradable composites, containing from 24 to 75 % of CC by mass, along with analyses of changes in selected properties of the obtained PCL composites, occurring upon various amounts of CC. Importantly, in the study relatively cheap and unmodified kind of CC has been used to determine the changeover cost of produced composites. Qualitative and quantitative analyses in addition to structure analysis of the obtained composites, including the distribution of the filler particles and their average dimensions were conducted. Furthermore, the mechanical and thermal properties, mass melt flow rate and the density have been determined. Finally, a commercially important economic analysis has been presented. A significant influence of CC on the mechanical properties of PCL was found. Specifically, the reduction of its relative elongation at break and impact strength, as well as the increase of its flexural modulus and bending strength. An increase in the thermal stability of the produced composites was also observed, however the characteristic temperatures of phase transitions as well as the degree of crystallinity did not change significantly. Considering the results of the density tests, an increase in the CC content resulted in a significant decrease in the unit price of the produced composites. This is of particular application importance, because a lower cost material with new properties could be obtained.

Effect of Pore Characteristics and Alkali Treatment on the Physicochemical and Biological Properties of a 3D-Printed Polycaprolactone Bone Scaffold

Polycaprolactone scaffolds were designed and 3D-printed with different pore shapes (cube and triangle) and sizes (500 and 700 μm) and modified with alkaline hydrolysis of different ratios (1, 3, and 5 M). In total, 16 designs were evaluated for their physical, mechanical, and biological properties. The present study mainly focused on the pore size, porosity, pore shapes, surface modification, biomineralization, mechanical properties, and biological characteristics that might influence bone ingrowth in 3D-printed biodegradable scaffolds. The results showed that the surface roughness in treated scaffolds increased compared to untreated polycaprolactone scaffolds (R _a = 2.3-10.5 nm and R _q = 17- 76 nm), but the structural integrity declined with an increase in the NaOH concentration especially in the scaffolds with small pores and a triangle shape. Overall, the treated polycaprolactone scaffolds particularly with the triangle shape and smaller pore size provided superior performance in mechanical strength similar to that of cancellous bone. Additionally, the in vitro study showed that cell viability increased in the polycaprolactone scaffolds with cubic pore shapes and small pore sizes, whereas mineralization was enhanced in the designs with larger pore sizes. Based on the results obtained, this study demonstrated that the 3D-printed modified polycaprolactone scaffolds exhibit a favorable mechanical property, biomineralization, and better biological properties; therefore, they can be applied in bone tissue engineering.

3D Fabrication and Characterisation of Electrically Receptive PCL-Graphene Scaffolds for Bioengineered In Vitro Tissue Models

Polycaprolactone (PCL) is a well-established biomaterial, offering extensive mechanical attributes along with low cost, biocompatibility, and biodegradability; however, it lacks hydrophilicity, bioactivity, and electrical conductivity. Advances in 3D fabrication technologies allow for these sought-after attributes to be incorporated into the scaffolds during fabrication. In this study, solvent-free Fused Deposition Modelling was employed to fabricate 3D scaffolds from PCL with increasing amounts of graphene (G), in the concentrations of 0.75, 1.5, 3, and 6% (w/w). The PCL+G scaffolds created were characterised physico-chemically, electrically, and biologically. Raman spectroscopy demonstrated that the scaffold outer surface contained both PCL and G, with the G component relatively uniformly distributed. Water contact angle measurement demonstrated that as the amount of G in the scaffold increases (0.75-6% w/w), hydrophobicity decreases; mean contact angle for pure PCL was recorded as 107.22 ± 9.39°, and that with 6% G (PCL+6G) as 77.56 ± 6.75°. Electrochemical Impedance Spectroscopy demonstrated a marked increase in electroactivity potential with increasing G concentration. Cell viability results indicated that even the smallest addition of G (0.75%) resulted in a significant improvement in electroactivity potential and bioactivity compared with that for pure PCL, with 1.5 and 3% exhibiting the highest statistically significant increases in cell proliferation.

Metronidazole Delivery Nanosystem Able To Reduce the Pathogenicity of Bacteria in Colorectal Infection

Metronidazole (MTZ) is a drug potentially used for the treatment of intestinal infections, namely, the ones caused by colorectal surgery. The traditional routes of administration decrease its local effectiveness and present off-site effects. To circumvent such limitations, herein a drug delivery system (DDS) based on MTZ-loaded nanoparticles (NPs) immobilized at the surface of electrospun fibrous meshes is proposed. MTZ at different concentrations (1, 2, 5, and 10 mg mL^-1) was loaded into chitosan-sodium tripolyphosphate NPs. The MTZ loaded into NPs at the highest concentration showed a quick release in the first 12 h, followed by a gradual release. This DDS was not toxic to human colonic cells. When tested against different bacterial strains, a significant reduction of Escherichia coli and Staphylococcus aureus was observed, but no effect was found against Enterococcus faecalis. Therefore, this DDS offers high potential to locally prevent the occurrence of infections after colorectal anastomosis.

Properties of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/Polycaprolactone Polymer Mixtures Reinforced by Cellulose Nanocrystals: Experimental and Simulation Studies

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/polycaprolactone (PHBV/PCL) polymer mixtures reinforced by cellulose nanocrystals (CNCs) have been obtained. To improve the CNC compatibility with the hydrophobic PHBV/PCL matrix, the CNC surface was modified by amphiphilic polymers, i.e., polyvinylpyrrolidone (PVP) and polyacrylamide (PAM). The polymer composites were characterized by FTIR, DSC, TG, XRD, microscopy, BET surface area, and tensile testing. The morphological, sorption, thermal, and mechanical properties of the obtained composites have been studied. It was found out that with an increase in the CNC content in the composites, the porosity of the films increased, which was reflected in an increase in their specific surface areas and water sorption. An analysis of the IR spectra confirms that hydrogen bonds can be formed between the CNC hydroxyl- and the -CO- groups of PCL and PHBV. The thermal decomposition of CNC in the PHBV/PCL/CNC composites starts at a much higher temperature than the decomposition of pure CNC. It was revealed that CNCs can either induce crystallization and the polymer crystallite growth or act as a compatibilizer of a mixture of the polymers causing their amorphization. The CNC addition significantly reduces the elongation and strength of the composites, but changes Young's modulus insignificantly, i.e., the mechanical properties of the composites are retained under conditions of small linear deformations. A molecular-dynamics simulation of several systems, starting from simplest binary (solvent-polymer) and finishing with multi-component (CNC-polymer mixture-solvent) systems, has been made. It is concluded that the surface modification of CNCs with amphiphilic polymers makes it possible to obtain the CNC composites with hydrophobic polymer matrices.

Optical sensors based on electrospun membranes – principles, applications, and prospects for chemistry and biology

Electrospun membranes are promising substrates for receptor layer immobilization in optical sensors. Either colorimetric, luminescence, or Raman scattering signal can be used to detect the analyte.

Utilizing Radio Frequency Plasma Treatment to Modify Polymeric Materials for Biomedical Applications

Studies that utilize radio frequency plasma modification as a strategy to tune the surface properties of polymeric constructs with the goal of enhancing their use as biomedical devices have grown considerably in number over the past decade. In this Review, we present the importance of plasma surface treatment to biomedical applications, including tissue engineering and wound healing. First, we introduce several key polymeric materials of interest for use as biomaterials, including those that are naturally derived and synthetic. We, then, provide an overview of possible outcomes of plasma modification, such as surface activation, etching, and deposition of a thin film, all of which can be used to alter the surface properties of a given polymer. Following this discussion, we review the methods used to characterize plasma-treated polymer surface properties, as well as the techniques used to evaluate their interactions with biological species of interest such as mammalian cells, bacteria, and blood components. To close, we provide a perspective on future outlooks of this exciting and rapidly evolving field.

Biocompatible Electrospun Polycaprolactone-Polyaniline Scaffold Treated with Atmospheric Plasma to Improve Hydrophilicity

Conductive polymers (CPs) have recently been applied in the development of scaffolds for tissue engineering applications in attempt to induce additional cues able to enhance tissue growth. Polyaniline (PANI) is one of the most widely studied CPs, but it requires to be blended with other polymers in order to be processed through conventional technologies. Here, we propose the fabrication of nanofibers based on a polycaprolactone (PCL)-PANI blend obtained using electrospinning technology. An extracellular matrix-like fibrous substrate was obtained showing a good stability in the physiological environment (37 °C in PBS solution up 7 days). However, since the high hydrophobicity of the PCL-PANI mats (133.5 ± 2.2°) could negatively affect the biological response, a treatment with atmospheric plasma was applied on the nanofibrous mats, obtaining a hydrophilic surface (67.1 ± 2°). In vitro tests were performed to confirm the viability and the physiological-like morphology of human foreskin fibroblast (HFF-1) cells cultured on the plasma treated PCL-PANI nanofibrous scaffolds.

Applications and challenges of low temperature plasma in pharmaceutical field

Low temperature plasma (LTP) technology has shown an outstanding application value in the pharmaceutical filed in recent ten years. This paper reviews the research advances in LTP, including its effects on enhancing or inhibiting drug activity, its combined use with drugs to treat cancers, its effects on the improvement of drug delivery system, its use in preparation of new inactivated virus vaccines, its use with mass spectrometry for rapid detection of drug quality, and the anti-tumor and sterilization effects of plasma-activated liquids. The paper also analyzes the challenges of LTP in the pharmaceutical filed, hoping to promote related research.

Basic Principles of Emulsion Templating and Its Use as an Emerging Manufacturing Method of Tissue Engineering Scaffolds

Tissue engineering (TE) aims to regenerate critical size defects, which cannot heal naturally, by using highly porous matrices called TE scaffolds made of biocompatible and biodegradable materials. There are various manufacturing techniques commonly used to fabricate TE scaffolds. However, in most cases, they do not provide materials with a highly interconnected pore design. Thus, emulsion templating is a promising and convenient route for the fabrication of matrices with up to 99% porosity and high interconnectivity. These matrices have been used for various application areas for decades. Although this polymer structuring technique is older than TE itself, the use of polymerised internal phase emulsions (PolyHIPEs) in TE is relatively new compared to other scaffold manufacturing techniques. It is likely because it requires a multidisciplinary background including materials science, chemistry and TE although producing emulsion templated scaffolds is practically simple. To date, a number of excellent reviews on emulsion templating have been published by the pioneers in this field in order to explain the chemistry behind this technique and potential areas of use of the emulsion templated structures. This particular review focusses on the key points of how emulsion templated scaffolds can be fabricated for different TE applications. Accordingly, we first explain the basics of emulsion templating and characteristics of PolyHIPE scaffolds. Then, we discuss the role of each ingredient in the emulsion and the impact of the compositional changes and process conditions on the characteristics of PolyHIPEs. Afterward, current fabrication methods of biocompatible PolyHIPE scaffolds and polymerisation routes are detailed, and the functionalisation strategies that can be used to improve the biological activity of PolyHIPE scaffolds are discussed. Finally, the applications of PolyHIPEs on soft and hard TE as well as in vitro models and drug delivery in the literature are summarised.

Fabrication and Plasma Surface Activation of Aligned Electrospun PLGA Fiber Fleeces with Improved Adhesion and Infiltration of Amniotic Epithelial Stem Cells Maintaining their Teno-inductive Potential

Electrospun PLGA microfibers with adequate intrinsic physical features (fiber alignment and diameter) have been shown to boost teno-differentiation and may represent a promising solution for tendon tissue engineering. However, the hydrophobic properties of PLGA may be adjusted through specific treatments to improve cell biodisponibility. In this study, electrospun PLGA with highly aligned microfibers were cold atmospheric plasma (CAP)-treated by varying the treatment exposure time (30, 60, and 90 s) and the working distance (1.3 and 1.7 cm) and characterized by their physicochemical, mechanical and bioactive properties on ovine amniotic epithelial cells (oAECs). CAP improved the hydrophilic properties of the treated materials due to the incorporation of new oxygen polar functionalities on the microfibers' surface especially when increasing treatment exposure time and lowering working distance. The mechanical properties, though, were affected by the treatment exposure time where the optimum performance was obtained after 60 s. Furthermore, CAP treatment did not alter oAECs' biocompatibility and improved cell adhesion and infiltration onto the microfibers especially those treated from a distance of 1.3 cm. Moreover, teno-inductive potential of highly aligned PLGA electrospun microfibers was maintained. Indeed, cells cultured onto the untreated and CAP treated microfibers differentiated towards the tenogenic lineage expressing tenomodulin, a mature tendon marker, in their cytoplasm. In conclusion, CAP treatment on PLGA microfibers conducted at 1.3 cm working distance represent the optimum conditions to activate PLGA surface by improving their hydrophilicity and cell bio-responsiveness. Since for tendon tissue engineering purposes, both high cell adhesion and mechanical parameters are crucial, PLGA treated for 60 s at 1.3 cm was identified as the optimal construct.

Fabrication and Plasma Modification of Nanofibrous Tissue Engineering Scaffolds

This paper provides a comprehensive overview of nanofibrous structures for tissue engineering purposes and the role of non-thermal plasma technology (NTP) within this field. Special attention is first given to nanofiber fabrication strategies, including thermally-induced phase separation, molecular self-assembly, and electrospinning, highlighting their strengths, weaknesses, and potentials. The review then continues to discuss the biodegradable polyesters typically employed for nanofiber fabrication, while the primary focus lies on their applicability and limitations. From thereon, the reader is introduced to the concept of NTP and its application in plasma-assisted surface modification of nanofibrous scaffolds. The final part of the review discusses the available literature on NTP-modified nanofibers looking at the impact of plasma activation and polymerization treatments on nanofiber wettability, surface chemistry, cell adhesion/proliferation and protein grafting. As such, this review provides a complete introduction into NTP-modified nanofibers, while aiming to address the current unexplored potentials left within the field.

Phase-contrast 3D tomography of HeLa cells grown in PLLA polymer electrospun scaffolds using synchrotron X-rays

Advanced imaging is useful for understanding the three-dimensional (3D) growth of cells. X-ray tomography serves as a powerful noninvasive, nondestructive technique that can fulfill these purposes by providing information about cell growth within 3D platforms. There are a limited number of studies taking advantage of synchrotron X-rays, which provides a large field of view and suitable resolution to image cells within specific biomaterials. In this study, X-ray synchrotron radiation microtomography at Diamond Light Source and advanced image processing were used to investigate cellular infiltration of HeLa cells within poly L-lactide (PLLA) scaffolds. This study demonstrates that synchrotron X-rays using phase contrast is a useful method to understand the 3D growth of cells in PLLA electrospun scaffolds. Two different fiber diameter (2 and 4 µm) scaffolds with different pore sizes, grown over 2, 5 and 8 days in vitro, were examined for infiltration and cell connectivity. After performing visualization by segmentation of the cells from the fibers, the results clearly show deeper cell growth and higher cellular interconnectivity in the 4 µm fiber diameter scaffold. This indicates the potential for using such 3D technology to study cell-scaffold interactions for future medical use.

A Novel Bilayer Polycaprolactone Membrane for Guided Bone Regeneration: Combining Electrospinning and Emulsion Templating

Guided bone regeneration is a common dental implant treatment where a barrier membrane (BM) is used between epithelial tissue and bone or bone graft to prevent the invasion of the fast-proliferating epithelial cells into the defect site to be able to preserve a space for infiltration of slower-growing bone cells into the periodontal defect site. In this study, a bilayer polycaprolactone (PCL) BM was developed by combining electrospinning and emulsion templating techniques. First, a 250 µm thick polymerised high internal phase emulsion (polyHIPE) made of photocurable PCL was manufactured and treated with air plasma, which was shown to enhance the cellular infiltration. Then, four solvent compositions were investigated to find the best composition for electrospinning a nanofibrous PCL barrier layer on PCL polyHIPE. The biocompatibility and the barrier properties of the electrospun layer were demonstrated over four weeks in vitro by histological staining. Following in vitro assessment of cell viability and cell migration, cell infiltration and the potential of PCL polyHIPE for supporting blood vessel ingrowth were further investigated using an ex-ovo chick chorioallantoic membrane assay. Our results demonstrated that the nanofibrous PCL electrospun layer was capable of limiting cell infiltration for at least four weeks, while PCL polyHIPE supported cell infiltration, calcium and mineral deposition of bone cells, and blood vessel ingrowth through pores.

Porous Alginate Scaffolds Assembled Using Vaterite CaCO3 Crystals

Formulation of multifunctional biopolymer-based scaffolds is one of the major focuses in modern tissue engineering and regenerative medicine. Besides proper mechanical/chemical properties, an ideal scaffold should: (i) possess a well-tuned porous internal structure for cell seeding/growth and (ii) host bioactive molecules to be protected against biodegradation and presented to cells when required. Alginate hydrogels were extensively developed to serve as scaffolds, and recent advances in the hydrogel formulation demonstrate their applicability as "ideal" soft scaffolds. This review focuses on advanced porous alginate scaffolds (PAS) fabricated using hard templating on vaterite CaCO3 crystals. These novel tailor-made soft structures can be prepared at physiologically relevant conditions offering a high level of control over their internal structure and high performance for loading/release of bioactive macromolecules. The novel approach to assemble PAS is compared with traditional methods used for fabrication of porous alginate hydrogels. Finally, future perspectives and applications of PAS for advanced cell culture, tissue engineering, and drug testing are discussed.

Plasma-Coated Polycaprolactone Nanofibers with Covalently Bonded Platelet-Rich Plasma Enhance Adhesion and Growth of Human Fibroblasts

Biodegradable nanofibers are extensively employed in different areas of biology and medicine, particularly in tissue engineering. The electrospun polycaprolactone (PCL) nanofibers are attracting growing interest due to their good mechanical properties and a low-cost structure similar to the extracellular matrix. However, the unmodified PCL nanofibers exhibit an inert surface, hindering cell adhesion and negatively affecting their further fate. The employment of PCL nanofibrous scaffolds for wound healing requires a certain modification of the PCL surface. In this work, the morphology of PCL nanofibers is optimized by the careful tuning of electrospinning parameters. It is shown that the modification of the PCL nanofibers with the COOH plasma polymers and the subsequent binding of NH2 groups of protein molecules is a rather simple and technologically accessible procedure allowing the adhesion, early spreading, and growth of human fibroblasts to be boosted. The behavior of fibroblasts on the modified PCL surface was found to be very different when compared to the previously studied cultivation of mesenchymal stem cells on the PCL nanofibrous meshes. It is demonstrated by X-ray photoelectron spectroscopy (XPS) that the freeze-thawed platelet-rich plasma (PRP) immobilization can be performed via covalent and non-covalent bonding and that it does not affect biological activity. The covalently bound components of PRP considerably reduce the fibroblast apoptosis and increase the cell proliferation in comparison to the unmodified PCL nanofibers or the PCL nanofibers with non-covalent bonding of PRP. The reported research findings reveal the potential of PCL matrices for application in tissue engineering, while the plasma modification with COOH groups and their subsequent covalent binding with proteins expand this potential even further. The use of such matrices with covalently immobilized PRP for wound healing leads to prolonged biological activity of the immobilized molecules and protects these biomolecules from the aggressive media of the wound.