Composite Foams as Tissue Scaffolds: Past, Present and Future

Composite Foams as Tissue Scaffolds: Past, Present and Futur

Proteins as Coating Materials on Bioactive Glass-based Composite Foams

Nowadays the replacement or repair of tissue damaged by disease or trauma, especially bone tissue, is one of the biggest challenges in the medical field and is faced by thousands of surgeons every day. Autografts are the current gold standard but they are strongly limited which turns the spotlight to the application of alloplastic grafts which consist of non-biological engineered materials like metals, ceramics or polymers [1]. Due to the high bioactivity, osteoconductivity and angiogenic effects, bioactive glasses, e.g. the 45S5 Bioglass® composition, are attracting increasingly attention as bone substitute materials. However, the brittle character of bioactive glass limits its application area in bone tissue engineering, particularly in load-bearing parts. To improve the mechanical properties of bioactive glass-based foams (scaffolds) fabricated by the foam replica technique [2], polymer coatings are applied to fill and bridge microcracks present on the surface of the scaffolds in order to increase the fracture strength [3]. Zein, a plant-derived protein from corn, offers biodegradability and biocompatibility and is widely used as coating material in the pharmaceutical and food industry [4]. 45S5 bioactive glass-based scaffolds, dip-coated in a solution with 8 wt.% zein in ethanol, showed enhanced mechanical performance after the coating procedure. Compressive strength increased from 0.04 ± 0.02 MPa for uncoated scaffolds to 0.21 ± 0.02 MPa for zein-coated scaffolds. In contrast, an animal-derived protein was also used as coating material to compare the potential of natural-derived proteins of different origins for further investigations in the field of bone tissue engineering. Collagen is the most abundant protein in mammals and has the ability to form a strong network [5]. By surface functionalization collagen type I can be covalently bonded to the bioactive glass surface. Additional chemical crosslinking with NHS and EDC further strengthen the collagen coating. Samples coated with collagen showed as well enhanced mechanical performance and exhibited values of 0.18 ± 0.02 MPa for compressive strength. For the evaluation of bioactivity, uncoated and polymer-coated scaffolds (zein and collagen) were immersed in simulated body fluid (SBF). Results showed no influence of the coating material on the bioactive behavior of the 45S5 bioactive glass-based foam. Therefore, both natural-derived proteins have the potential to be used as coating materials for tissue engineering appliations and are promising candidates for further comparative studies in this field. [1] García-Gareta E, Coathup MJ, Blunn GW. Osteoinduction of bone grafting materials for bone repair and regeneration. Bone 2015;81:112–21. [2] Chen QZ, Thompson ID, Boccaccini AR. 45S5 Bioglass®-derived glass-ceramic scaffolds for bone tissue engineering. Biomaterials 2006;27:2414–25. [3] Philippart A, Boccaccini AR, Fleck C, Schubert DW, Roether JA. Toughening and functionalization of bioactive ceramic and glass bone scaffolds by biopolymer coatings and infiltration: a review of the last 5 years. Expert Rev Med Devices 2015;12:93–111. [4] Shukla R, Cheryan M. Zein: the industrial protein from corn. Ind Crops Prod 2001;13:171–92. [5] Parenteau-Bareil R, Gauvin R, Berthod F. Collagen-Based Biomaterials for Tissue Engineering Applications. Materials (Basel) 2010;3:1863–87

Incorporation of Calcium Containing Mesoporous (MCM-41-Type) Particles in Electrospun PCL Fibers by Using Benign Solvents

The electrospinning technique is a versatile method for the production of fibrous scaffolds able to resemble the morphology of the native extra cellular matrix. In the present paper, electrospinning is used to fabricate novel SiO2 particles (type MCM-41) containing poly(epsilon-caprolactone) (PCL) fibers. The main aims of the present work are both the optimization of the particle synthesis and the fabrication of composite fibers, obtained using benign solvents, suitable as drug delivery systems and scaffolds for soft tissue engineering applications. The optimized synthesis and characterization of calcium-containing MCM-41 particles are reported. Homogeneous bead-free composite electrospun mats were obtained by using acetic acid and formic acid as solvents; neat PCL electrospun mats were used as control. Initially, an optimization of the electrospinning environmental parameters, like relative humidity, was performed. The obtained composite nanofibers were characterized from the morphological, chemical and mechanical points of view, the acellular bioactivity of the composite nanofibers was also investigated. Positive results were obtained in terms of mesoporous particle incorporation in the fibers and no significant differences in terms of average fiber diameter were detected between the neat and composite electrospun fibers. Even if the Ca-containing MCM-41 particles are bioactive, this property is not preserved in the composite fibers. In fact, during the bioactivity assessment, the particles were released confirming the potential application of the composite fibers as a drug delivery system. Preliminary in vitro tests with bone marrow stromal cells were performed to investigate cell adhesion on the fabricated composite mats, the positive obtained results confirmed the suitability of the composite fibers as scaffolds for soft tissue engineerin

Fibronectin Functionalized Electrospun Fibers by Using Benign Solvents: Best Way to Achieve Effective Functionalization

The aim of this study is to demonstrate the feasibility of different functionalization methods for electrospun fibers developed using benign solvents. In particular three different approaches were investigated to achieve the functionalization of poly(epsilon caprolactone) (PCL) electrospun fibers with fibronectin. Protein surface entrapment, chemical functionalization and coaxial electrospinning were performed and compared. Moreover, bilayered scaffolds, with a top patterned and functionalized layer with fibronectin and a randomly oriented not functionalized layer were fabricated, demonstrating the versatility of the use of benign solvents for electrospinning also for the fabrication of complex graded structures. Besides the characterization of the morphology of the obtained scaffolds, ATR-FTIR and ToF-SIMS were used for the surface characterization of the functionalized fibers. Cell adhesion and proliferation were also investigated by using ST-2 cells. Positive results were obtained from all functionalized scaffolds and the most promising results were obtained with bilayered scaffolds, in terms of cells infiltration inside the fibrous structure

Comparative Study of the Antimicrobial Activity of Selenium Nanoparticles With Different Surface Chemistry and Structure

Although selenium nanoparticles (SeNPs) have gained attention in the scientific community mostly through investigation of their anticancer activity, a great potential of this nanomaterial was recognized recently regarding its antimicrobial activity. The particle form, size, and surface chemistry have been recognized as crucial parameters determining the interaction of nanomaterials with biological entities. Furthermore, considering a narrow boundary between beneficial and toxic effects for selenium per se, it is clear that investigations of biomedical applications of SeNPs are very demanding and must be done with great precautions. The goal of this work is to evaluate the effects of SeNPs surface chemistry and structure on antimicrobial activity against several common bacterial strains, including Staphylococcus aureus (ATCC 6538), Enterococcus faecalis (ATCC 29212), Bacillus subtilis (ATCC 6633), and Kocuria rhizophila (ATCC 9341), as well as Escherichia coli (ATCC 8739), Salmonella Abony (NCTC 6017), Klebsiella pneumoniae (NCIMB 9111) and Pseudomonas aeruginosa (ATCC 9027), and the standard yeast strain Candida albicans (ATCC 10231). Three types of SeNPs were synthesized by chemical reduction approach using different stabilizers and reducing agents: (i) bovine serum albumin (BSA) + ascorbic acid, (ii) chitosan + ascorbic acid, and (iii) with glucose. A thorough physicochemical characterization of the obtained SeNPs was performed to determine the effects of varying synthesis parameters on their morphology, size, structure, and surface chemistry. All SeNPs were amorphous, with spherical morphology and size in the range 70–300 nm. However, the SeNPs obtained under different synthesis conditions, i.e. by using different stabilizers as well as reducing agents, exhibited different antimicrobial activity as well as cytotoxicity which are crucial for their applications. In this paper, the antimicrobial screening of the selected systems is presented, which was determined by the broth microdilution method, and inhibitory influence on the production of monomicrobial and dual-species biofilm was evaluated. The potential mechanism of action of different systems is proposed. Additionally, the cytotoxicity of SeNPs was examined on the MRC-5 cell line, in the same concentration interval as for antimicrobial testing. It was shown that formulation SeNPs-BSA expressed a significantly lower cytotoxic effect than the other two formulations

Incorporation of Calcium Containing Mesoporous (MCM-41-Type) Particles in Electrospun PCL Fibers by Using Benign Solvents

The electrospinning technique is a versatile method for the production of fibrous scaffolds able to resemble the morphology of the native extra cellular matrix. In the present paper, electrospinning is used to fabricate novel SiO2 particles (type MCM-41) containing poly(epsilon-caprolactone) (PCL) fibers. The main aims of the present work are both the optimization of the particle synthesis and the fabrication of composite fibers, obtained using benign solvents, suitable as drug delivery systems and scaffolds for soft tissue engineering applications. The optimized synthesis and characterization of calcium-containing MCM-41 particles are reported. Homogeneous bead-free composite electrospun mats were obtained by using acetic acid and formic acid as solvents; neat PCL electrospun mats were used as control. Initially, an optimization of the electrospinning environmental parameters, like relative humidity, was performed. The obtained composite nanofibers were characterized from the morphological, chemical and mechanical points of view, the acellular bioactivity of the composite nanofibers was also investigated. Positive results were obtained in terms of mesoporous particle incorporation in the fibers and no significant differences in terms of average fiber diameter were detected between the neat and composite electrospun fibers. Even if the Ca-containing MCM-41 particles are bioactive, this property is not preserved in the composite fibers. In fact, during the bioactivity assessment, the particles were released confirming the potential application of the composite fibers as a drug delivery system. Preliminary in vitro tests with bone marrow stromal cells were performed to investigate cell adhesion on the fabricated composite mats, the positive obtained results confirmed the suitability of the composite fibers as scaffolds for soft tissue engineering

Comparative Study of the Antimicrobial Activity of Selenium Nanoparticles With Different Surface Chemistry and Structure

Although selenium nanoparticles (SeNPs) have gained attention in the scientific community mostly through investigation of their anticancer activity, a great potential of this nanomaterial was recognized recently regarding its antimicrobial activity. The particle form, size, and surface chemistry have been recognized as crucial parameters determining the interaction of nanomaterials with biological entities. Furthermore, considering a narrow boundary between beneficial and toxic effects for selenium per se, it is clear that investigations of biomedical applications of SeNPs are very demanding and must be done with great precautions. The goal of this work is to evaluate the effects of SeNPs surface chemistry and structure on antimicrobial activity against several common bacterial strains, including Staphylococcus aureus (ATCC 6538), Enterococcus faecalis (ATCC 29212), Bacillus subtilis (ATCC 6633), and Kocuria rhizophila (ATCC 9341), as well as Escherichia coli (ATCC 8739), Salmonella Abony (NCTC 6017), Klebsiella pneumoniae (NCIMB 9111) and Pseudomonas aeruginosa (ATCC 9027), and the standard yeast strain Candida albicans (ATCC 10231). Three types of SeNPs were synthesized by chemical reduction approach using different stabilizers and reducing agents: (i) bovine serum albumin (BSA) + ascorbic acid, (ii) chitosan + ascorbic acid, and (iii) with glucose. A thorough physicochemical characterization of the obtained SeNPs was performed to determine the effects of varying synthesis parameters on their morphology, size, structure, and surface chemistry. All SeNPs were amorphous, with spherical morphology and size in the range 70–300 nm. However, the SeNPs obtained under different synthesis conditions, i.e. by using different stabilizers as well as reducing agents, exhibited different antimicrobial activity as well as cytotoxicity which are crucial for their applications. In this paper, the antimicrobial screening of the selected systems is presented, which was determined by the broth microdilution method, and inhibitory influence on the production of monomicrobial and dual-species biofilm was evaluated. The potential mechanism of action of different systems is proposed. Additionally, the cytotoxicity of SeNPs was examined on the MRC-5 cell line, in the same concentration interval as for antimicrobial testing. It was shown that formulation SeNPs-BSA expressed a significantly lower cytotoxic effect than the other two formulations

Manuka honey and bioactive glass impart methylcellulose foams with antibacterial effects for wound-healing applications

Wound dressings able to deliver topically bioactive molecules represent a new generation of wound-regeneration therapies. In this article, foams based on methylcellulose cross-linked with Manuka honey were used as a platform to deliver borate bioactive glass particles doped additionally with copper. Borate bioactive glasses are of great interest in wound-healing applications due to a combination of favorable features, such as angiogenic and antibacterial properties. The multifunctional composite providing the dual effect of the bioactive glass and Manuka honey was produced by freeze-drying, and the resulting foams exhibit suitable morphology characterized by high porosity. Moreover, the performed tests showed improved wettability and mechanical performance with the addition of bioactive glass particles. Dissolution studies using simulated body fluid and cell biology tests using relevant skin cells further proved the excellent bioactivity and positive effects of the foams on cell proliferation and migration. Most interestingly, by the dual release of Manuka honey and ions from the copper-doped bioactive glass, an antibacterial effect against E. coli and S. aureus was achieved. Therefore, the multifunctional foams showed promising outcomes as potential wound dressings for the treatment of infected wounds

When Electrospun Fiber Support Matters: In Vitro Ovine Long-Term Folliculogenesis on Poly (Epsilon Caprolactone) (PCL)-Patterned Fibers

Current assisted reproduction technologies (ART) are insufficient to cover the slice of the population needing to restore fertility, as well as to amplify the reproductive performance of domestic animals or endangered species. The design of dedicated reproductive scaffolds has opened the possibility to better recapitulate the reproductive 3D ovarian environment, thus potentially innovating in vitro folliculogenesis (ivF) techniques. To this aim, the present research has been designed to compare ovine preantral follicles in vitro culture on poly(epsilon-caprolactone) (PCL)-based electrospun scaffolds designed with different topology (Random vs. Patterned fibers) with a previously validated system. The ivF performances were assessed after 14 days under 3D-oil, Two-Step (7 days in 3D-oil and on scaffold), or One-Step PCL protocols (14 days on PCL-scaffold) by assessing morphological and functional outcomes. The results show that Two- and One-Step PCL ivF protocols, when performed on patterned scaffolds, were both able to support follicle growth, antrum formation, and the upregulation of follicle marker genes leading to a greater oocyte meiotic competence than in the 3D-oil system. In conclusion, the One-Step approach could be proposed as a practical and valid strategy to support a synergic follicle-oocyte in vitro development, providing an innovative tool to enhance the availability of matured gametes on an individual basis for ART purposes

Polymer (PCL) fibers with Zn‐doped mesoporous bioactive glass nanoparticles for tissue regeneration

Abstract Composite fibrous membranes based on poly(ɛ‐caprolactone) (PCL) and mesoporous bioactive glass nanoparticles (MBGNs) were fabricated by electrospinning. MBGNs and Zn‐doped MBGNs prepared by microemulsion sol–gel method were successfully incorporated inside the polymeric fibers of 240 and 385 nm in diameter for undoped and Zn‐doped PCL_MBGNs fibers, respectively. Thermal analysis showed that the concentration of MBGNs reached a maximum of around 21 wt% for Zn‐doped MBGNs. Both PCL_MBGNs and PCL_MBGNs_Zn composite membrane exhibited bioactivity after immersion in simulated body fluid (SBF). X‐ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) showed the evolution of composite membranes, confirming the formation of hydroxyapatite (HAp). However, the degradation products of membranes did not affect the viability and proliferation of murine stromal cells (ST‐2) and thus the new fiber structures represent a suitable environment for cell adhesion. Therefore, the incorporation of mesoporous glass nanoparticles doped with therapeutically active Zn2+ ions inside the PCL fibers offers the possibility to create a multifunctional biomaterial suitable for drug delivery and tissue engineering