Electrospun PCL Fiber Mats Incorporating Multi-Targeted B and Co Co-Doped Bioactive Glass Nanoparticles for Angiogenesis

Physical properties of zinc, silver, or cerium ion doped borate glass incorporated PCL/gelatin electrospun fibers and their interaction with NG108-15 neural cells

In this study, 1393-B3 based borate bioactive glasses (BGs) undoped and doped with 1 wt% zinc (ZnBG), cerium (CeBG), or silver (AgBG) were prepared and were incorporated into gelatin/PCL (GEL/PCL) electrospun fibers for neural tissue engineering applications. Particle sizes of the prepared BGs were 3.1, 10.6, 14.6, and 3.7 µm for undoped BG, ZnBG, AgBG, and CeBG, respectively. Aligned electrospun fibers were prepared with 5 wt% of BG particles to produce 5BG/PCL/GEL, 5ZnBG/PCL/GEL, 5AgBG/PCL/GEL and 5CeBG/PCL/GEL fibers. Random 5CeBG/PCL/GEL fibers were also prepared for comparison. A rise in fiber diameter was measured for BG-incorporated fibers compared to PCL/GEL fibers. Mechanical tests on the fibers indicated ultimate tensile strength values of 1-3.5 MPa, the range of mechanical properties of neural tissue. Cell culture studies were carried out with the NG108-15 cell line. Cell alignment was observed on the electrospun fibers on day 2. On days 1 and 2, the optical density was higher for ZnBG/PCL/GEL, CeBG/PCL/GEL, and AgBG/PCL/GEL than for BG/PCL/GEL fibers. On day 4, undoped BG-containing nanofibers had higher optical density compared to those containing doped BGs. This result could be due to a slower release rate of boron from the pure BG/PCL/GEL fiber mat. Overall, within the studied range, all fiber mats were found to be suitable for neural tissue engineering in terms of neural cell compatibility and mechanical properties. In the future, a wider range of ion doping must be considered to fully comprehend the potential of such ion-releasing fibers for neural regeneration.

Strategies in Electrospun Polymer and Hybrid Scaffolds for Enhanced Cell Integration and Vascularization for Bone Tissue Engineering and Organoids

Addressing the demand for bone substitutes, tissue engineering responds to the high prevalence of orthopedic surgeries worldwide and the limitations of conventional tissue reconstruction techniques. Materials, cells, and growth factors constitute the core elements in bone tissue engineering, influencing cellular behavior crucial for regenerative treatments. Scaffold design, including architectural features and porosity, significantly impacts cellular penetration, proliferation, differentiation, and vascularization. This review discusses the hierarchical structure of bone and the process of neovascularization in the context of biofabrication of scaffolds. We focus on the role of electrospinning and its modifications in scaffold fabrication to improve scaffold properties to enhance further tissue regeneration, for example, by boosting oxygen and nutrient delivery. We highlight how scaffold design impacts osteogenesis and the overall success of regenerative treatments by mimicking the extracellular matrix (ECM). Additionally, we explore the emerging field of bone organoids-self-assembled, three-dimensional (3D) structures derived from stem cells that replicate native bone tissue's architecture and functionality. While bone organoids hold immense potential for modeling bone diseases and facilitating regenerative treatments, their main limitation remains insufficient vascularization. Hence, we evaluate innovative strategies for pre-vascularization and discuss the latest techniques for assessing and improving vascularization in both scaffolds and organoids presenting the most commonly used cell lines and biological models. Moreover, we analyze cutting-edge techniques for assessing vascularization, evaluating their advantages and drawbacks to propose complex solutions. Finally, by integrating these approaches, we aim to advance the development of bioactive materials that promote successful bone regeneration.

Stimulated Full-Thickness Cutaneous Wound Healing with Bioactive Dressings of Zinc and Cobalt Ion-Doped Bioactive Glass-Coated Eggshell Membranes in a Diabetic Rabbit Model

Eggshell membrane-based biomedical applications have recently received great attention for their wound-healing properties. However, there are limited studies on diabetic wound healing. In this regard, we devised four types of composite eggshell membrane mats with nanoscale coatings of bioactive glass/Zn/Co-doped bioactive glass (ESM + BAG, ESM + ZnBAG, ESM + CoBAG, and ESM + ZnCoBAG) as wound-dressing materials for chronic nonhealing diabetic wounds. A detailed study of the physicochemical properties of the mats was conducted. In vitro studies demonstrated cytocompatibility and viability of human dermal fibroblasts on all four types of mats. The cells also attached finely on the mats with the help of cellular extensions, as evident from scanning electron microscopy (SEM) and rhodamine-phalloidin and Hoechst 33342 staining of cellular components. Endowed with bioactive properties, these mats influenced all aspects of full-thickness skin wound healing in diabetic animal model studies. All of the mats, especially the ESM + ZnCoBAG mat, showed the earliest wound closure, effective renewal, and restructuring of the extracellular matrix in terms of an accurate and timely accumulation of collagen, elastin, and reticulin fibers. Hydroxyproline and sulfated glycosaminoglycans were significantly (p < 0.01, p < 0.05) higher in ESM-ZnCoBAG-treated wounds in comparison to ESM-BAG-treated wounds, which suggests that these newly developed mats have potential as an affordable diabetic wound care solution in biomedical research.

A Bioactive Injectable Hydrogel Regulates Tumor Metastasis and Wound Healing for Melanoma via NIR-Light Triggered Hyperthermia

Surgical resection remains the mainstream treatment for malignant melanoma. However, challenges in wound healing and residual tumor metastasis pose significant hurdles, resulting in high recurrence rates in patients. Herein, a bioactive injectable hydrogel (BG-Mngel) formed by crosslinking sodium alginate (SA) with manganese-doped bioactive glass (BG-Mn) is developed as a versatile platform for anti-tumor immunotherapy and postoperative wound healing for melanoma. The incorporation of Mn2+ within bioactive glass (BG) can activate the cGAS-STING immune pathway to elicit robust immune response for cancer immunotherapy. Furthermore, doping Mn2+ in BG endows system with excellent photothermal properties, hence facilitating STING activation and reversing the tumor immune-suppressive microenvironment. BG exhibits favorable angiogenic capacity and tissue regenerative potential, and Mn2+ promotes cell migration in vitro. When combining BG-Mngel with anti-PD-1 antibody (α-PD-1) for the treatment of malignant melanoma, it shows enhanced anti-tumor immune response and long-term immune memory response. Remarkably, BG-Mngel can upregulate the expression of genes related to blood vessel formation and promote skin tissue regeneration when treating full-thickness wounds. Overall, BG-MnGel serves as an effective adjuvant therapy to regulate tumor metastasis and wound healing for malignant melanoma.

Gelatin Methacryloyl (GelMA)-Based Biomaterial Inks: Process Science for 3D/4D Printing and Current Status

Tissue engineering for injured tissue replacement and regeneration has been a subject of investigation over the last 30 years, and there has been considerable interest in using additive manufacturing to achieve these goals. Despite such efforts, many key questions remain unanswered, particularly in the area of biomaterial selection for these applications as well as quantitative understanding of the process science. The strategic utilization of biological macromolecules provides a versatile approach to meet diverse requirements in 3D printing, such as printability, buildability, and biocompatibility. These molecules play a pivotal role in both physical and chemical cross-linking processes throughout the biofabrication, contributing significantly to the overall success of the 3D printing process. Among the several bioprintable materials, gelatin methacryloyl (GelMA) has been widely utilized for diverse tissue engineering applications, with some degree of success. In this context, this review will discuss the key bioengineering approaches to identify the gelation and cross-linking strategies that are appropriate to control the rheology, printability, and buildability of biomaterial inks. This review will focus on the GelMA as the structural (scaffold) biomaterial for different tissues and as a potential carrier vehicle for the transport of living cells as well as their maintenance and viability in the physiological system. Recognizing the importance of printability toward shape fidelity and biophysical properties, a major focus in this review has been to discuss the qualitative and quantitative impact of the key factors, including microrheological, viscoelastic, gelation, shear thinning properties of biomaterial inks, and printing parameters, in particular, reference to 3D extrusion printing of GelMA-based biomaterial inks. Specifically, we emphasize the different possibilities to regulate mechanical, swelling, biodegradation, and cellular functionalities of GelMA-based bio(material) inks, by hybridization techniques, including different synthetic and natural biopolymers, inorganic nanofillers, and microcarriers. At the close, the potential possibility of the integration of experimental data sets and artificial intelligence/machine learning approaches is emphasized to predict the printability, shape fidelity, or biophysical properties of GelMA bio(material) inks for clinically relevant tissues.

Opportunities for Bioactive Glass in Gastrointestinal Conditions: A Review of Production Methodologies, Morphology, Composition, and Performance

Bioactive glasses (BGs) are widely used in orthopedic and dental applications for their ability to stimulate endogenous bone formation and regeneration. BG applications more recently broadened to include soft tissue conditions, based on their ability to stimulate angiogenesis, soft tissue regeneration, and wound healing. Sol-gel synthesis has helped facilitate this expansion, allowing formulators to tailor the morphological characteristics of the BG matrix. The effectiveness of BGs in skin wound healing is viewed as a gateway for their use as both a therapeutic and drug delivery platform in other soft tissue applications, notably gastrointestinal (GI) applications, which form the focus of this review. Recent changes in international guidelines for GI conditions shifted clinical objectives from symptom management to mucosal wound healing. The additional scrutiny of proton pump inhibitor (PPI) safety, increasing burden of disease, and financial costs associated with gastroesophageal reflux disease (GERD), peptic ulcer disease (PUD), and inflammatory bowel disease (IBD) open new clinical possibilities for BG. This narrative literature review intersects materials engineering, formulation science, and clinical practice, setting it apart from prior literature. Broadly, current evidence for BG applications in GI conditions is sparse and under-developed, which this review directly addresses. It explores and synthesizes evidence that supports the potential use of sol-gel-derived BG for the efficacious treatment of soft tissue applications, with specific reference to GI conditions. An overview with comparative analysis of current BG synthesis techniques and associated challenges is presented, and influences of composition, biologically active ions, and morphological characteristics in soft tissue applications are explored. To contextualize this, sol-gel-derived BGs are proposed as a dual, tailorable therapeutic and drug delivery platform for upper and lower GI conditions. Future directions for this largely untapped area of translational research are also proposed, based on extant literature.

Processing and characterization of aligned electrospun gelatin/polycaprolactone nanofiber mats incorporating borate glass (13-93B3) microparticles

Aligned biodegradable fibers incorporating bioactive glass particles are being highly investigated for tissue engineering applications. In this study, 5, 7 and 10 wt% melt-derived 1393B3 borate glass (BG) microparticles (average size: 3.15 µm) were incorporated in 83 wt% polycaprolactone (PCL) and 17 wt% gelatin (GEL) (83PCL/17GEL) solutions to produce aligned electrospun composite nanofiber mats. Addition of 5 wt% BG particles significantly increased the alignment of the nanofibers. However, further incorporation of BG particles led to reduced degree of alignment, likely due to an increase of viscosity. Mechanical tests indicated a tensile modulus and tensile strength of approximately 51 MPa and 3.4 MPa, respectively, for 5 wt% addition of 1393B3 BG microparticles, values considered suitable for soft tissue engineering applications. However, with the increasing amount of 1393B3 BG, the nanofiber mats became brittle. Contact angle was reduced after the addition of 5 wt% of 1393B3 BG particles from∼45° to∼39°. Cell culture studies with normal human dermal fibroblast (NHDF) cells indicated that 5 wt% 1393B3 BG incorporated nanofiber mats were cytocompatible whereas higher doping with 1393B3 BGs reduced biocompatibility. Overall, 5 wt% 1393B3 BG doped PCL/GEL nanofiber mats were aligned with high biocompatibility exhibiting desirable mechanical properties for soft tissue engineering, which indicates their potential for applications requiring aligned nanofibers, such as peripheral neural regeneration.

Angiogenic Modification of Microfibrous Polycaprolactone by pCMV-VEGF165 Plasmid Promotes Local Vascular Growth after Implantation in Rats

Insufficient vascular growth in the area of artificial-material implantation contributes to ischemia, fibrosis, the development of bacterial infections, and tissue necrosis around the graft. The purpose of this study was to evaluate angiogenesis after implantation of polycaprolactone microfiber scaffolds modified by a pCMV-VEGF165-plasmid in rats. Influence of vascularization on scaffold degradation was also examined. We investigated flat microfibrous scaffolds obtained by electrospinning polycaprolactone with incorporation of the pCMV-VEGF-165 plasmid into the microfibers at concentrations of 0.005 ng of plasmid per 1 mg of polycaprolactone (0.005 ng/mg) (LCGroup) and 0.05 ng/mg (HCGroup). The samples were subcutaneously implanted in the interscapular area of rats. On days 7, 16, 33, 46, and 64, the scaffolds were removed, and a histological study with a morphometric evaluation of the density and diameter of the vessels and microfiber diameter was performed. The number of vessels was increased in all groups, as well as the resorption of the scaffold. On day 33, the vascular density in the HCGroup was 42% higher compared to the control group (p = 0.0344). The dose-dependent effect of the pCMV-VEGF165-plasmid was confirmed by enhanced angiogenesis in the HCGroup compared to the LCGroup on day 33 (p-value = 0.0259). We did not find a statistically significant correlation between scaffold degradation rate and vessel growth (the Pearson correlation coefficient was ρ = 0.20, p-value = 0.6134). Functionalization of polycaprolactone by incorporation of the pCMV-VEGF165 plasmid provided improved vascularization within 33 days after implantation, however, vessel growth did not seem to correlate with scaffold degradation rate.

Development of 3D Printed Electrospun Scaffolds for the Fabrication of Porous Scaffolds for Vascular Applications

Over the past two decades, electrospinning has emerged as a common technique to produce biomedical scaffolds composed of ultrafine fibers formed from many natural and synthetic polymers. A major advantage of this technique is the ability to produce scaffolds that resemble the native extracellular matrix in physical, chemical, and topological properties. However, scaffolds fabricated via electrospinning are not formed with a controlled architecture and typically do a poor job of directing cell growth into prescribed structures for tissue/organ development. To address these weaknesses, 3D bioprinting has recently been used to develop scaffolds that have a highly organized and precise global topology. Unfortunately, these 3D bioprinted scaffolds do not typically resemble the native extracellular matrix in physical properties, such as porosity, fiber diameter, and pore size (e.g., the microarchitecture). Thus, the goal of the current study was to develop a technique that harnesses the intrinsic advantages of both conventional electrospinning and 3D bioprinting techniques to produce scaffolds that have the potential to be used within biomedical applications. The physical properties of formed 3D printed electrospun scaffolds were compared with conventional electrospun and 3D printed scaffolds. Further, we conducted initial proof-of-concept biocompatibility studies to illustrate the applicability of the scaffolds within vascular applications. Our results illustrate that 3D printed electrospun scaffolds can be developed, via our technique, that have highly tailored and organized arbitrary geometries with scaffold properties in the range of the innate extracellular matrix. In addition, these scaffolds were shown to support endothelial cell growth. Therefore, we illustrate the development and testing of a novel bioscaffold fabrication technique that may be used for many tissue engineering and regenerative medicine applications, which allows for the direct printing of electrospun scaffolds into well-defined macro-scale geometries that also retain the micro-structures commonly observed in electrospun scaffolds.

Bioactive glass-based fibrous wound dressings

Since the discovery of silicate bioactive glass (BG) by Larry Hench in 1969, different classes of BGs have been researched over decades mainly for bone regeneration. More recently, validating the beneficial influence of BGs with tailored compositions on angiogenesis, immunogenicity and bacterial infection, the applicability of BGs has been extended to soft tissue repair and wound healing. Particularly, fibrous wound dressings comprising BG particle reinforced polymer nanofibers and cotton-candy-like BG fibers have been proven to be successful for wound healing applications. Such fibrous dressing materials imitate the physical structure of skin's extracellular matrix and release biologically active ions e.g. regenerative, pro-angiogenic and antibacterial ions, e.g. borate, copper, zinc, etc., that can provoke cellular activities to regenerate the lost skin tissue and to induce new vessels formation, while keeping an anti-infection environment. In the current review, we discuss different BG fibrous materials meant for wound healing applications and cover the relevant literature in the past decade. The production methods for BG-containing fibers are explained and as fibrous wound dressing materials, their wound healing and bactericidal mechanisms, depending on the ions they release, are discussed. The present gaps in this research area are highlighted and new strategies to address them are suggested.

Topographical and Biomechanical Guidance of Electrospun Fibers for Biomedical Applications

Electrospinning is gaining increasing interest in the biomedical field as an eco-friendly and economic technique for production of random and oriented polymeric fibers. The aim of this review was to give an overview of electrospinning potentialities in the production of fibers for biomedical applications with a focus on the possibility to combine biomechanical and topographical stimuli. In fact, selection of the polymer and the eventual surface modification of the fibers allow selection of the proper chemical/biological signal to be administered to the cells. Moreover, a proper design of fiber orientation, dimension, and topography can give the opportunity to drive cell growth also from a spatial standpoint. At this purpose, the review contains a first introduction on potentialities of electrospinning for the obtainment of random and oriented fibers both with synthetic and natural polymers. The biological phenomena which can be guided and promoted by fibers composition and topography are in depth investigated and discussed in the second section of the paper. Finally, the recent strategies developed in the scientific community for the realization of electrospun fibers and for their surface modification for biomedical application are presented and discussed in the last section.