Sacrificial Core-Based Electrospinning: a Facile and Versatile Approach to Fabricate Devices for Potential Cell and Tissue Encapsulation Applications

Manufacturing 3D Biomimetic Tissue: A Strategy Involving the Integration of Electrospun Nanofibers with a 3D-Printed Framework for Enhanced Tissue Regeneration

3D printing and electrospinning are versatile techniques employed to produce 3D structures, such as scaffolds and ultrathin fibers, facilitating the creation of a cellular microenvironment in vitro. These two approaches operate on distinct working principles and utilize different polymeric materials to generate the desired structure. This review provides an extensive overview of these techniques and their potential roles in biomedical applications. Despite their potential role in fabricating complex structures, each technique has its own limitations. Electrospun fibers may have ambiguous geometry, while 3D-printed constructs may exhibit poor resolution with limited mechanical complexity. Consequently, the integration of electrospinning and 3D-printing methods may be explored to maximize the benefits and overcome the individual limitations of these techniques. This review highlights recent advancements in combined techniques for generating structures with controlled porosities on the micro-nano scale, leading to improved mechanical structural integrity. Collectively, these techniques also allow the fabrication of nature-inspired structures, contributing to a paradigm shift in research and technology. Finally, the review concludes by examining the advantages, disadvantages, and future outlooks of existing technologies in addressing challenges and exploring potential opportunities.

Multifunctional embelin- poly (3-hydroxybutyric acid) and sodium alginate-based core-shell electrospun nanofibrous mat for wound healing applications

In this study, coaxial electrospinning is employed to make core-shell fibers, which represents a major advance in biomaterial innovation. Fibers that combine a protective shell and a therapeutic agent-loaded core, herald a revolutionary era in tissue engineering and wound care. Besides supporting cell growth, these fibers also preserve sterility, which makes them ideal for advanced wound dressings. We used embelin as the basis for this study because of its natural antibacterial properties. Its effectiveness in inhibiting the growth of bacteria made it the ideal candidate for our research. We have synthesized core-shell nanofibers that contain Sodium Alginate (SAL) in a Poly (ethylene oxide) (PEO) shell and Embelin in a Poly (3-hydroxybutyric acid) (PHB) core, which exhibit the homogeneity and flawless structure required for biomedical applications. When using SAL-PEO and EMB-PHB solutions dissolved in 1,1,1,3,3,3 hexafluoro-2-propanol (HFIP), high consistency in results can be achieved. A biocompatibility study was conducted using NIH-3T3 fibroblasts, which demonstrated remarkable adhesion and proliferation, with over 95 % growth supporting both PHB + SAL-PEO and EMB-PHB + SAL-PEO fibers. In addition, the scaffold loaded with Embelin shows strong antibacterial activity and cytocompatibility. The combined activity demonstrates the potential of EMB-PHB + SAL-PEO fibers in wound healing, where tissue regeneration and preservation of sterility are crucial. The optimized concentration of Embelin within these scaffolds demonstrates robust antibacterial efficacy while exhibiting minimal toxicity, thus positioning them as highly promising candidates for a wide range of biological applications, including wound healing.

Modeling human immune responses to vaccination in vitro

The human immune system is a complex network of coordinated components that are crucial for health and disease. Animal models, commonly used to study immunomodulatory agents, are limited by species-specific differences, low throughput, and ethical concerns. In contrast, in vitro modeling of human immune responses can enable species- and population-specific mechanistic studies and translational development within the same study participant. Translational accuracy of in vitro models is enhanced by accounting for genetic, epigenetic, and demographic features such as age, sex, and comorbidity. This review explores various human in vitro immune models, considers evidence that they may resemble human in vivo responses, and assesses their potential to accelerate and de-risk vaccine discovery and development.

Three-Dimensional Printer-Assisted Electrospinning for Fabricating Intricate Biological Tissue Mimics

Although regenerative medicine necessitates advanced three-dimensional (3D) scaffolds for organ and tissue applications, creating intricate structures across scales, from nano- to meso-like biological tissues, remains a challenge. Electrospinning of nanofibers offers promise due to its capacity to craft not only the dimensions and surfaces of individual fibers but also intricate attributes, such as anisotropy and porosity, across various materials. In this study, we used a 3D printer to design a mold with polylactic acid for gel modeling. This gel template, which was mounted on a metal wire, facilitated microfiber electrospinning. After spinning, these structures were treated with EDTA to remove the template and were then cleansed and dried, resulting in 3D microfibrous (3DMF) structures, with average fiber diameters of approximately 1 µm on the outer and inner surfaces. Notably, these structures matched their intended design dimensions without distortion or shrinkage, demonstrating the adaptability of this method for various template sizes. The cylindrical structures showed high elasticity and stretchability with an elastic modulus of 6.23 MPa. Furthermore, our method successfully mimicked complex biological tissue structures, such as the inner architecture of the voice box and the hollow partitioned structure of the heart's tricuspid valve. Achieving specific intricate shapes required multiple spinning sessions and subsequent assemblies. In essence, our approach holds potential for crafting artificial organs and forming the foundational materials for cell culture scaffolds, addressing the challenges of crafting intricate multiscale structures.

Macromolecular crowding transforms regenerative medicine by enabling the accelerated development of functional and truly three-dimensional cell assembled micro tissues

Scaffold-free in vitro organogenesis exploits the innate ability of cells to synthesise and deposit their own extracellular matrix to fabricate tissue-like assemblies. Unfortunately, cell-assembled tissue engineered concepts require prolonged ex vivo culture periods of very high cell numbers for the development of a borderline three-dimensional implantable device, which are associated with phenotypic drift and high manufacturing costs, thus, hindering their clinical translation and commercialisation. Herein, we report the accelerated (10 days) development of a truly three-dimensional (338.1 ± 42.9 μm) scaffold-free tissue equivalent that promotes fast wound healing and induces formation of neotissue composed of mature collagen fibres, using human adipose derived stem cells seeded at only 50,000 cells/cm2 on an poly (N-isopropylacrylamide-co-N-tert-butylacrylamide (PNIPAM86-NTBA14) temperature-responsive electrospun scaffold and grown under macromolecular crowding conditions (50 μg/ml carrageenan). Our data pave the path for a new era in scaffold-free regenerative medicine.

Strategies to Tune Electrospun Scaffold Porosity for Effective Cell Response in Tissue Engineering

Tissue engineering aims to develop artificial human tissues by culturing cells on a scaffold in the presence of biochemical cues. Properties of scaffold such as architecture and composition highly influence the overall cell response. Electrospinning has emerged as one of the most affordable, versatile, and successful approaches to develop nonwoven nano/microscale fibrous scaffolds whose structural features resemble that of the native extracellular matrix. However, dense packing of the fibers leads to small-sized pores which obstruct cell infiltration and therefore is a major limitation for their use in tissue engineering applications. To this end, a variety of approaches have been investigated to enhance the pore properties of the electrospun scaffolds. In this review, we collect state-of-the-art modification methods and summarize them into six classes as follows: approaches focused on optimization of packing density by (a) conventional setup, (b) sequential or co-electrospinning setups, (c) involving sacrificial elements, (d) using special collectors, (e) post-production processing, and (f) other specialized methods. Overall, this review covers historical as well as latest methodologies in the field and therefore acts as a quick reference for those interested in electrospinning matrices for tissue engineering and beyond.

The Relationships between Process Parameters and Polymeric Nanofibers Fabricated Using a Modified Coaxial Electrospinning

The concrete relationship between the process parameters and nanoproduct properties is an important challenge for applying nanotechnology to produce functional nanomaterials. In this study, the relationships between series of process parameters and the medicated nanofibers’ diameter were investigated. With an electrospinnable solution of hydroxypropyl methylcellulose (HPMC) and ketoprofen as the core fluid, four kinds of nanofibers were prepared with ethanol as a sheath fluid and under the variable applied voltages. Based on these nanofibers, a series of relationships between the process parameters and the nanofibers’ diameters (D) were disclosed, such as with the height of the Taylor cone (H, D = 125 + 363H), with the angle of the Taylor cone (α, D = 1576 − 19α), with the length of the straight fluid jet (L, D = 285 + 209L), and with the spreading angle of the instable region (θ, D = 2342 − 43θ). In vitro dissolution tests verified that the smaller the diameters, the faster ketoprofen (KET) was released from the HPMC nanofibers. These concrete process-property relationships should provide a way to achieve new knowledge about the electrostatic energy-fluid interactions, and to meanwhile improve researchers’ capability to optimize the coaxial process conditions to achieve the desired nanoproducts.