Electrospinning of biomimetic fibrous scaffolds for tissue engineering: a review

Biomimetic and non-biomimetic approaches in dura substitutes: the influence of mechanical properties

The dura mater, the furthest and strongest layer of the meninges, is crucial for protecting the brain and spinal cord. Its biomechanical behavior is vital, as any alterations can compromise biological functions. In recent decades, interest in the dura mater has increased due to the need for hermetic closure of dural defects prompting the development of several substitutes. Collagen-based dural substitutes are common commercial options, but they lack the complex biological and structural elements of the native dura mater, impacting regeneration and potentially causing complications like wound/postoperative infection and cerebrospinal fluid leakage. To face this issue, recent tissue engineering approaches focus on creating biomimetic dura mater substitutes. The objective of this review is to discuss whether mimicking the mechanical properties of native tissue or ensuring high biocompatibility and bioactivity is more critical in developing effective dural substitutes, or if both aspects should be systematically linked. After a brief description of the properties and architecture of the native cranial dura, we describe the advantages and limitations of biomimetic dura mater substitutes to better understand their relevance. In particular, we consider biomechanical properties' impact on dura repair's effectiveness. Finally, the obstacles and perspectives for developing the ideal dural substitute are explored.

Recent Advances in Functional Hydrogel for Repair of Abdominal Wall Defects: A Review

The abdominal wall plays a crucial role in safeguarding the internal organs of the body, serving as an essential protective barrier. Defects in the abdominal wall are common due to surgery, infection, or trauma. Complex defects have limited self-healing capacity and require external intervention. Traditional treatments have drawbacks, and biomaterials have not fully achieved the desired outcomes. Hydrogel has emerged as a promising strategy that is extensively studied and applied in promoting tissue regeneration by filling or repairing damaged tissue due to its unique properties. This review summarizes the five prominent properties and advances in using hydrogels to enhance the healing and repair of abdominal wall defects: (a) good biocompatibility with host tissues that reduces adverse reactions and immune responses while supporting cell adhesion migration proliferation; (b) tunable mechanical properties matching those of the abdominal wall that adapt to normal movement deformations while reducing tissue stress, thereby influencing regulating cell behavior tissue regeneration; (c) drug carriers continuously delivering drugs and bioactive molecules to sites optimizing healing processes enhancing tissue regeneration; (d) promotion of cell interactions by simulating hydrated extracellular matrix environments, providing physical support, space, and cues for cell migration, adhesion, and proliferation; (e) easy manipulation and application in surgical procedures, allowing precise placement and close adhesion to the defective abdominal wall, providing mechanical support. Additionally, the advances of hydrogels for repairing defects in the abdominal wall are also mentioned. Finally, an overview is provided on the current obstacles and constraints faced by hydrogels, along with potential prospects in the repair of abdominal wall defects.

The wound healing effect of polycaprolactone-chitosan scaffold coated with a gel containing Zataria multiflora Boiss. volatile oil nanoemulsions

AIMS

Thymus plant is a very useful herbal medicine with various properties such as anti-inflammatory and antibacterial. Therefore, the properties of this plant have made this drug a suitable candidate for wound healing. In this study, hydroxypropyl methylcellulose (HPMC) gel containing Zataria multiflora volatile oil nanoemulsion (neZM) along with polycaprolactone/chitosan (PCL-CS) nanofibrous scaffold was used, and the effect of three experimental groups on the wound healing process was evaluated. The first group, HPMC gel containing neZM, the second group, PCL-CS nanofibers, and the third group, HPMC gel containing neZM and bandaged with PCL-CS nanofibers (PCL-CS/neZM). Wounds bandaged with common sterile gas were considered as control.

METHODS

The nanoemulsion was synthesized by a spontaneous method and loaded into a hydroxypropyl methylcellulose (HPMC) gel. The DLS test investigated the size of these nanoemulsions. A PCL-CS nanofibrous scaffold was also synthesized by electrospinning method then SEM and contact angle tests investigated morphology and hydrophilicity/hydrophobicity of its surface. The animal study was performed on full-thickness skin wounds in rats, and the process of tissue regeneration in the experimental and control groups was evaluated by H&E and Masson's trichrome staining.

RESULTS

The results showed that the nanoemulsion has a size of 225±9 nm and has an acceptable dispersion. The PCL-CS nanofibers synthesized by the electrospinning method also show non-beaded smooth fibers and due to the presence of chitosan with hydrophilic properties, have higher surface hydrophobicity than PCL fibers. The wound healing results show that the PCL-CS/neZM group significantly reduced the wound size compared to the other groups on the 7th, 14th, and 21st days. The histological results also show that the PCL-CS/neZM group could significantly reduce the parameters of edema, inflammation, and vascularity and increase the parameters of fibrosis, re-epithelialization, and collagen deposition compared to other groups on day 21.

CONCLUSION

The results of this study show that the PCL-CS/neZM treatment can effectively improve wound healing.

Effect of Gelatin Coating and GO Incorporation on the Properties and Degradability of Electrospun PCL Scaffolds for Bone Tissue Regeneration

Polymer-based nanocomposites such as polycaprolactone/graphene oxide (PCL/GO) have emerged as alternatives for bone tissue engineering (BTE) applications. The objective of this research was to investigate the impact of a gelatin (Gt) coating on the degradability and different properties of PCL nanofibrous scaffolds fabricated by an electrospinning technique with 1 and 2 wt% GO. Uniform PCL/GO fibers were obtained with a beadless structure and rough surface. PCL/GO scaffolds exhibited an increase in their crystallization temperature (Tc), attributed to GO, which acted as a nucleation agent. Young's modulus increased by 32 and 63% for the incorporation of 1 and 2 wt% GO, respectively, in comparison with neat PCL. A homogeneous Gt coating was further applied to these fibers, with incorporations as high as 24.7 wt%. The introduction of the Gt coating improved the hydrophilicity and degradability of the scaffolds. Bioactivity analysis revealed that the hydroxyapatite crystals were deposited on the Gt-coated scaffolds, which made them different from their uncoated counterparts. Our results showed the synergic effect of Gt and GO in enhancing the multifunctionality of the PCL, in particular the degradability rate, bioactivity, and cell adhesion and proliferation of hGMSC cells, making it an interesting biomaterial for BTE.

Cardiac regeneration - Past advancements, current challenges, and future directions

Cardiovascular disease is the leading cause of mortality and morbidity worldwide. Despite improvements in the standard of care for patients with heart diseases, including innovation in pharmacotherapy and surgical interventions, none have yet been proven effective to prevent the progression to heart failure. Cardiac transplantation is the last resort for patients with severe heart failure, but donor shortages remain a roadblock. Cardiac regenerative strategies include cell-based therapeutics, gene therapy, direct reprogramming of non-cardiac cells, acellular biologics, and tissue engineering methods to restore damaged hearts. Significant advancements have been made over the past several decades within each of these fields. This review focuses on the advancements of: 1) cell-based cardiac regenerative therapies, 2) the use of noncoding RNA to induce endogenous cell proliferation, and 3) application of bioengineering methods to promote retention and integration of engrafted cells. Different cell sources have been investigated, including adult stem cells derived from bone marrow and adipose cells, cardiosphere-derived cells, skeletal myoblasts, and pluripotent stem cells. In addition to cell-based transplantation approaches, there have been accumulating interest over the past decade in inducing endogenous CM proliferation for heart regeneration, particularly with the use of noncoding RNAs such as miRNAs and lncRNAs. Bioengineering applications have focused on combining cell-transplantation approaches with fabrication of a porous, vascularized scaffold using biomaterials and advanced bio-fabrication techniques that may offer enhanced retention of transplanted cells, with the hope that these cells would better engraft with host tissue to improve cardiac function. This review summarizes the present status and future challenges of cardiac regenerative therapies.

Magnetic Nanofibrous Hydrogels for Dynamic Control of Stem Cell Differentiation

The extracellular matrix in tissue consists of complex heterogeneous soft materials with hierarchical structure and dynamic mechanical properties dictating cell and tissue level function. In many natural matrices, there are nanofibrous structures that serve to guide cell activity and dictate the form and function of tissue. Synthetic hydrogels with integrated nanofibers can mimic the structural properties of native tissue; however, model systems with dynamic mechanical properties remain elusive. Here we demonstrate modular nanofibrous hydrogels that can be reversibly stiffened in response to applied magnetic fields. Iron oxide nanoparticles were incorporated into gelatin nanofibers through electrospinning, followed by chemical stabilization and fragmentation. These magnetoactive nanofibers can be mixed with virtually any hydrogel material and reversibly stiffen the matrix at a low fiber content (≤3%). In contrast to previous work, where a large quantity of magnetic material disallowed cell encapsulation, the low nanofiber content allows matrix stiffening with cells in 3D. Using adipose derived stem cells, we show how nanofibrous matrices are beneficial for both osteogenesis and adipogenesis, where stiffening the hydrogel with applied magnetic fields enhances osteogenesis while discouraging adipogenesis. Skeletal myoblast progenitors were used as a model of tissue morphogenesis with matrix stiffening augmenting myogenesis and multinucleated myotube formation. The ability to reversibly stiffen fibrous hydrogels through magnetic stimulation provides a useful tool for studying nanotopography and dynamic mechanics in cell culture, with a scope for stimuli responsive materials for tissue engineering.

Extracellular Matrix-Based and Electrospun Scaffolding Systems for Vaginal Reconstruction

Congenital vaginal anomalies and pelvic organ prolapse affect different age groups of women and both have significant negative impacts on patients' psychological well-being and quality of life. While surgical and non-surgical treatments are available for vaginal defects, their efficacy is limited, and they often result in long-term complications. Therefore, alternative treatment options are urgently needed. Fortunately, tissue-engineered scaffolds are promising new treatment modalities that provide an extracellular matrix (ECM)-like environment for vaginal cells to adhere, secrete ECM, and be remodeled by host cells. To this end, ECM-based scaffolds or the constructs that resemble ECM, generated by self-assembly, decellularization, or electrospinning techniques, have gained attention from both clinicians and researchers. These biomimetic scaffolds are highly similar to the native vaginal ECM and have great potential for clinical translation. This review article aims to discuss recent applications, challenges, and future perspectives of these scaffolds in vaginal reconstruction or repair strategies.

Electrospun nanofibers for medical face mask with protection capabilities against viruses: State of the art and perspective for industrial scale-up

Face masks have proven to be a useful protection from airborne viruses and bacteria, especially in the recent years pandemic outbreak when they effectively lowered the risk of infection from Coronavirus disease (COVID-19) or Omicron variants, being recognized as one of the main protective measures adopted by the World Health Organization (WHO). The need for improving the filtering efficiency performance to prevent penetration of fine particulate matter (PM), which can be potential bacteria or virus carriers, has led the research into developing new methods and techniques for face mask fabrication. In this perspective, Electrospinning has shown to be the most efficient technique to get either synthetic or natural polymers-based fibers with size down to the nanoscale providing remarkable performance in terms of both particle filtration and breathability. The aim of this Review is to give further insight into the implementation of electrospun nanofibers for the realization of the next generation of face masks, with functionalized membranes via addiction of active material to the polymer solutions that can give optimal features about antibacterial, antiviral, self-sterilization, and electrical energy storage capabilities. Furthermore, the recent advances regarding the use of renewable materials and green solvent strategies to improve the sustainability of electrospun membranes and to fabricate eco-friendly filters are here discussed, especially in view of the large-scale nanofiber production where traditional membrane manufacturing may result in a high environmental and health risk.

Effect of porosity on mechanical and biological properties of bioprinted scaffolds

Treatment of tissue defects commonly represents a major problem in clinics due to difficulties involving a shortage of donors, inappropriate sizes, abnormal shapes, and immunological rejection. While many scaffold parameters such as pore shape, porosity percentage, and pore connectivity could be adjusted to achieve desired mechanical and biological properties. These parameters are crucial scaffold parameters that can be accurately produced by 3D bioprinting technology based on the damaged tissue. In the present research, the effect of porosity percentage (40%, 50%, and 60%) and different pore shapes (square, star, and gyroid) on the mechanical (e.g., stiffness, compressive and tensile behavior) and biological (e.g., biodegradation, and cell viability) properties of porous polycaprolactone (PCL) scaffolds coated with gelatin have been investigated. Moreover, human foreskin fibroblast cells were cultured on the scaffolds in the in-vitro procedures. MTT assay (4, 7, and 14 days) was utilized to determine the cytotoxicity of the porous scaffolds. It is revealed that the porous scaffolds produced by the bioprinter did not produce a cytotoxic effect. Among all the porous scaffolds, scaffolds with a pore size of about 500 μm and porosity of 50% showed the best cell proliferation compared to the controls after 14 days. The results demonstrated that the pore shape, porosity percentage, and pore connectivity have an important role in improving the mechanical and biological properties of porous scaffolds. These 3D bioprinted biodegradable scaffolds exhibit potential for future application as polymeric scaffolds in hard tissue engineering applications.

Electrohydrodynamic 3D Printing of Aqueous Solutions

Among the various electrohydrodynamic (EHD) processing techniques, electrowriting (EW) produces the most complex 3D structures. Aqueous solution EW similarly retains the potential for additive manufacturing well-resolved 3D structures, while providing new opportunities for processing biologically derived polymers and eschewing organic solvents. However, research on aqueous-based EHD processing is still limited. To summarize the field and advocate for increased use of aqueous bio-based materials, this review summarizes the most significant contributions of aqueous solution processing. Special emphasis has been placed on understanding the effects of different printing parameters, the prospects for 3D processing new materials, and future challenges.

Polyurethane/Liquid Crystal Microfibers with pDNA Polyplex Loadings for the Optimal Release and Promotion of HUVEC Proliferation

Fiber structures with connected pores resemble the natural extracellular matrix (ECM) in tissues, and show high potential for promoting the formation of natural functional tissue. The geometry of composite fibers produced by electrospinning is similar to that of the living-tissue ECM, in terms of structural complexity. The introduction of liquid crystals does not affect the morphology of fibers. The composite mat shows better hydrophilicity, with higher content of liquid crystal. At the same time, the higher the content of liquid crystal, the lower the modulus and tensile strength, and the higher the breaking energy and the elongation at break. Additionally, the factors affecting fibers are also investigated in this study. The addition of liquid crystals to the fibers' matrix can slow down the release of pDNA, which is the most common vehicle for genetic engineering, and the encapsulation of pDNA polymer into the fiber matrix can maintain biological activity. The continued release of the pDNA complex was achieved in this study through liquid crystals, and the effective release is controllable. In addition, the integration of liquid crystals into fibers with pDNA polymers can cause a faster transfection rate and promote HUVEC (Human Umbilical Vein Endothelial Cells) growth. It is possible to combine electrospun fibers containing LC (liquid crystal) with pDNA condensation technology to achieve the goal of a sustained release. The production of inductable tissue-building equipment can manipulate the required signals at an effective level in the local tissue microenvironment.

A Concise Review on Electrospun Scaffolds for Kidney Tissue Engineering

Chronic kidney disease is one of the deadliest diseases globally and treatment methods are still insufficient, relying mostly on transplantation and dialysis. Engineering of kidney tissues in vitro from induced pluripotent stem cells (iPSCs) could provide a solution to this medical need by restoring the function of damaged kidneys. However, implementation of such approaches is still challenging to achieve due to the complexity of mature kidneys in vivo. Several strategies have been defined to obtain kidney progenitor endothelial and epithelial cells that could form nephrons and proximal tube cells, but these lack tissue maturity and vascularisation to be further implemented. Electrospinning is a technique that has shown promise in the development of physiological microenvironments of several tissues and could be applied in the engineering of kidney tissues. Synthetic polymers such as polycaprolactone, polylactic acid, and poly(vinyl alcohol) have been explored in the manufacturing of fibres that align and promote the proliferation and cell-to-cell interactions of kidney cells. Natural polymers including silk fibroin and decellularised extracellular matrix have also been explored alone and in combination with synthetic polymers promoting the differentiation of podocytes and tubular-specific cells. Despite these attempts, further work is still required to advance the applications of electrospun fibres in kidney tissue engineering and explore this technique in combination with other manufacturing methods such as bioprinting to develop more organised, mature and reproducible kidney organoids.

Prospects and Challenges of Electrospun Cell and Drug Delivery Vehicles to Correct Urethral Stricture

Current therapeutic modalities to treat urethral strictures are associated with several challenges and shortcomings. Therefore, significant strides have been made to develop strategies with minimal side effects and the highest therapeutic potential. In this framework, electrospun scaffolds incorporated with various cells or bioactive agents have provided promising vistas to repair urethral defects. Due to the biomimetic nature of these constructs, they can efficiently mimic the native cells’ niches and provide essential microenvironmental cues for the safe transplantation of multiple cell types. Furthermore, these scaffolds are versatile platforms for delivering various drug molecules, growth factors, and nucleic acids. This review discusses the recent progress, applications, and challenges of electrospun scaffolds to deliver cells or bioactive agents during the urethral defect repair process. First, the current status of electrospinning in urethral tissue engineering is presented. Then, the principles of electrospinning in drug and cell delivery applications are reviewed. Finally, the recent preclinical studies are summarized and the current challenges are discussed.

Polysaccharides, as biological macromolecule-based scaffolding biomaterials in cornea tissue engineering: A review

Corneal-related diseases and injuries are the leading causes of vision loss, estimated to affect over 10 million people worldwide. Currently, cadaveric corneal grafts are considered the gold standard of treatment to restore cornea-related vision. However, this treatment modality faces different challenges such as donor shortage and graft failure. Therefore, the need for alternative solutions continues to grow. Tissue engineering has dramatically progressed to produce artificial cornea implants in order to repair, regenerate, or replace the damaged cornea. In this regard, a variety of polysaccharides such as cellulose, chitosan, alginate, agarose, and hyaluronic acid have been widely explored as scaffolding biomaterials for the production of tissue-engineered cornea. These polymers are known for their excellent biocompatibility, versatile properties, and processability. Recent progress and future perspectives of polysaccharide-based biomaterials in cornea tissue engineering is reviewed here.

A Review of Recent Advances in Natural Polymer-Based Scaffolds for Musculoskeletal Tissue Engineering

The musculoskeletal (MS) system consists of bone, cartilage, tendon, ligament, and skeletal muscle, which forms the basic framework of the human body. This system plays a vital role in appropriate body functions, including movement, the protection of internal organs, support, hematopoiesis, and postural stability. Therefore, it is understandable that the damage or loss of MS tissues significantly reduces the quality of life and limits mobility. Tissue engineering and its applications in the healthcare industry have been rapidly growing over the past few decades. Tissue engineering has made significant contributions toward developing new therapeutic strategies for the treatment of MS defects and relevant disease. Among various biomaterials used for tissue engineering, natural polymers offer superior properties that promote optimal cell interaction and desired biological function. Natural polymers have similarity with the native ECM, including enzymatic degradation, bio-resorb and non-toxic degradation products, ability to conjugate with various agents, and high chemical versatility, biocompatibility, and bioactivity that promote optimal cell interaction and desired biological functions. This review summarizes recent advances in applying natural-based scaffolds for musculoskeletal tissue engineering.

Cold atmospheric plasma modification and electrical conductivity induction in gelatin/polyvinylidene fluoride nanofibers for neural tissue engineering

BACKGROUND

This research follows some investigations through neural tissue engineering, including fabrication, surface treatment, and evaluation of novel self-stimuli conductive biocompatible and degradable nanocomposite scaffolds.

METHODS

Gelatin as a biobased material and polyvinylidene fluoride (PVDF) as a mechanical, electrical, and piezoelectric improvement agent were co-electrospun. In addition, polyaniline/graphene (PAG) nanoparticles were synthesized and added to gelatin solutions in different percentages to induce electrical conductivity. After obtaining optimum PAG percentage, cold atmospheric plasma (CAP) treatment was applied over the best samples by different plasma variable parameters. Finally, the biocompatibility of the scaffolds was analyzed and approved by in vitro tests using two different PC12 and C6 cell lines. In the present study the morphology, FTIR, dynamic light scattering, mechanical properties, wettability, contact angle tests, differential scanning calorimetric, rate of degradation, conductivity, biocompatibility, gene expression, DAPI staining, and cell proliferation were investigated.

RESULTS

The PAG percentage optimization results revealed fiber diameter reduction, conductivity enhancement, young's modulus improvement, hydrophilicity devaluation, water uptake decrement, and degradability reduction in electrospun nanofibers by increasing the PAG concentration. Furthermore, ATR-FTIR, FE-SEM, AFM, and contact angle tests revealed that helium CAP treatment improves scaffold characterizations for 90 seconds in duration time. Furthermore, the results of the MTT assay, FE-SEM, DAPI staining, and RT-PCR revealed that samples containing 2.5% w/w of PAG are the most biocompatible, and CAP treatment increases cell proliferation and improves neural gene expression in the differentiation medium.

CONCLUSIONS

According to the results, the samples with the 2.5% w/w of PAG could provide a suitable matrix for neural tissue engineering in terms of physicochemical and biological.

Bone morphogenetic protein (BMP)-modified graphene oxide-reinforced polycaprolactone-gelatin nanofiber scaffolds for application in bone tissue engineering

In this study, blend nanofibrous scaffolds were electrospun from polycaprolactone/gelatin (PCL/Gel) blend solutions reinforced by bone morphogenetic protein (BMP)-modified graphene oxide (GO). SEM results showed that uniform and bead-less nanofibers with 270 nm average diameter were obtained from electrospun of PCL/Gel blend solutions. Tensile strength test and contact angle measurement demonstrated that addition of PCL led to higher mechanical and physical properties of the resulting nanofibers. The addition of PCL as well as GO in the blend supports the suitable mechanical strength in the body media. The loading of BMP-modified graphene in the Gel/PCL structure caused the formation of nanofibrous substrate with great resemblance to bone tissue. Gel/PCL-G hybrid nanofibers revealed good biocompatibility in the presence of human osteosarcoma cells, and no trace of cellular toxicity was observed. The cells grown on the scaffolds exhibited a spindle-like and broad morphology and almost uniformly covered the entire nanofiber scaffold. Gel/PCL nanofibers reinforced by graphene oxide-immobilized bone morphogenetic protein was prepared as a promising safe and biocompatible nanofiber with high antibacterial activity for bone tissue engineering.

Electrospun Nanofibers Revisited: An Update on the Emerging Applications in Nanomedicine

Electrospinning (ES) has become a straightforward and customizable drug delivery technique for fabricating drug-loaded nanofibers (NFs) using various biodegradable and non-biodegradable polymers. One of NF's pros is to provide a controlled drug release through managing the NF structure by changing the spinneret type and nature of the used polymer. Electrospun NFs are employed as implants in several applications including, cancer therapy, microbial infections, and regenerative medicine. These implants facilitate a unique local delivery of chemotherapy because of their high loading capability, wide surface area, and cost-effectiveness. Multi-drug combination, magnetic, thermal, and gene therapies are promising strategies for improving chemotherapeutic efficiency. In addition, implants are recognized as an effective antimicrobial drug delivery system overriding drawbacks of traditional antibiotic administration routes such as their bioavailability and dosage levels. Recently, a sophisticated strategy has emerged for wound healing by producing biomimetic nanofibrous materials with clinically relevant properties and desirable loading capability with regenerative agents. Electrospun NFs have proposed unique solutions, including pelvic organ prolapse treatment, viable alternatives to surgical operations, and dental tissue regeneration. Conventional ES setups include difficult-assembled mega-sized equipment producing bulky matrices with inadequate stability and storage. Lately, there has become an increasing need for portable ES devices using completely available off-shelf materials to yield highly-efficient NFs for dressing wounds and rapid hemostasis. This review covers recent updates on electrospun NFs in nanomedicine applications. ES of biopolymers and drugs is discussed regarding their current scope and future outlook.

Electrospun strong, bioactive, and bioabsorbable silk fibroin/poly (L-lactic-acid) nanoyarns for constructing advanced nanotextile tissue scaffolds

Bio-textiles have aroused attractive attentions in tissue engineering and regenerative medicine, and developing robust, bio-absorbable, and extracellular matrix (ECM) fibril-mimicking nanofibrous textiles is urgently required for the renewal of existing microfibrous textile-based scaffolds and grafts. In this study, an integrated electrospinning system consisting of one nanoyarn-forming unit and one hot stretching unit is reported to fabricate silk fibroin (SF)/poly (L-lactic-acid) (PLLA) nanofibrous yarns (nanoyarns). The hot stretching process is demonstrated to significantly improve the fiber alignment, crystallinity, and mechanical properties of SF/PLLA nanoyarns, compared to the unstretched controls. For instance, the fiber alignment degree of hot stretched 50/50 SF/PLLA nanoyarn has increased by 25%, and the failure strength has increased by 246.5%, compared with the corresponding un-stretched control. Increasing the SF/PLLA mass ratio is found to significantly decrease the crystallinity and mechanical properties, but notably increase the degradation rate and surface hydrophilicity of SF/PLLA nanoyarns. Different SF/PLLA nanoyarns are further meticulously interwoven with warp and weft directions to obtain several nanofibrous woven textiles. The results from in vitro cell characterization and in vivo subcutaneous implantation show that increasing the SF/PLLA mass ratio significantly improves the biological properties and effectively reduces the inflammatory response of nanoyarn-constructed textiles. Overall, this study demonstrates that our SF/PLLA nanoyarns with controllable physical, mechanical and biological performances are fantastic candidates for the designing and development of advanced nanoarchitectured textile tissue scaffolds.

Bioengineering approaches to treat the failing heart: from cell biology to 3D printing

Successfully engineering a functional, human, myocardial pump would represent a therapeutic alternative for the millions of patients with end-stage heart disease and provide an alternative to animal-based preclinical models. Although the field of cardiac tissue engineering has made tremendous advances, major challenges remain, which, if properly resolved, might allow the clinical implementation of engineered, functional, complex 3D structures in the future. In this Review, we provide an overview of state-of-the-art studies, challenges that have not yet been overcome and perspectives on cardiac tissue engineering. We begin with the most clinically relevant cell sources used in this field and discuss the use of topological, biophysical and metabolic stimuli to obtain mature phenotypes of cardiomyocytes, particularly in relation to organized cytoskeletal and contractile intracellular structures. We then move from the cellular level to engineering planar cardiac patches and discuss the need for proper vascularization and the main strategies for obtaining it. Finally, we provide an overview of several different approaches for the engineering of volumetric organs and organ parts - from whole-heart decellularization and recellularization to advanced 3D printing technologies.

Bioinspired NEMS—Prospective of Collaboration with Nature

The fields of micro- and nanomechanics are strongly interconnected with the development of micro-electro-mechanical (MEMS) and nano-electro-mechanical (NEMS) devices, their fabrication and applications. This article highlights the biomimetic concept of designing new nanodevices for advanced materials and sensing applications.

Electrospun Methacrylated Gelatin/Poly(L-Lactic Acid) Nanofibrous Hydrogel Scaffolds for Potential Wound Dressing Application

Electrospun nanofiber mats have attracted intense attention as advanced wound dressing materials. The objective of this study was to fabricate methacrylated gelatin (MeGel)/poly(L-lactic acid) (PLLA) hybrid nanofiber mats with an extracellular matrix (ECM) mimicking nanofibrous structure and hydrogel-like properties for potential use as wound dressing materials. MeGel was first synthesized via the methacryloyl substitution of gelatin (Gel), a series of MeGel and PLLA blends with various mass ratios were electrospun into nanofiber mats, and a UV crosslinking process was subsequently utilized to stabilize the MeGel components in the nanofibers. All the as-crosslinked nanofiber mats exhibited smooth and bead-free fiber morphologies. The MeGel-containing and crosslinked nanofiber mats presented significantly improved hydrophilic properties (water contact angle = 0°; 100% wettability) compared to the pure PLLA nanofiber mats (~127°). The swelling ratio of crosslinked nanofiber mats notably increased with the increase of MeGel (143.6 ± 7.4% for PLLA mats vs. 875.0 ± 17.1% for crosslinked 1:1 MeGel/PLLA mats vs. 1135.2 ± 16.0% for crosslinked MeGel mats). The UV crosslinking process was demonstrated to significantly improve the structural stability and mechanical properties of MeGel/PLLA nanofiber mats. The Young's modulus and ultimate strength of the crosslinked nanofiber mats were demonstrated to obviously decrease when more MeGel was introduced in both dry and wet conditions. The biological tests showed that all the crosslinked nanofiber mats presented great biocompatibility, but the crosslinked nanofiber mats with more MeGel were able to notably promote the attachment, growth, and proliferation of human dermal fibroblasts. Overall, this study demonstrates that our MeGel/PLLA blend nanofiber mats are attractive candidates for wound dressing material research and application.

Electrospun Medicated Nanofibers for Wound Healing: Review

With the increasing demand for wound care and treatment worldwide, traditional dressings have been unable to meet the needs of the existing market due to their limited antibacterial properties and other defects. Electrospinning technology has attracted more and more researchers' attention as a simple and versatile manufacturing method. The electrospun nanofiber membrane has a unique structure and biological function similar to the extracellular matrix (ECM), and is considered an advanced wound dressing. They have significant potential in encapsulating and delivering active substances that promote wound healing. This article first discusses the common types of wound dressing, and then summarizes the development of electrospun fiber preparation technology. Finally, the polymers and common biologically active substances used in electrospinning wound dressings are summarized, and portable electrospinning equipment is also discussed. Additionally, future research needs are put forward.

Extracellular matrix extraction techniques and applications in biomedical engineering

The concept of tissue engineering involves regeneration and repair of damaged tissue and organs using various combinations of cells, growth factors and scaffolds. The extracellular matrix (ECM) forms the integral part of the scaffold to induce cell proliferation thereby leading to new tissue formation. Decellularization technique provides decellularized ECM (dECM), free of cells while preserving the in vivo biomolecules. In this review, we focus on the detailed methodology of diverse decellularization techniques for various organs of different animals, and the biomedical applications employing the dECM. A culmination of different methods of decellularization is optimized, which offers a suitable microenvironment mimicking the native in vivo topography for in vitro organ regeneration. A detailed assessment of the dECM provides information on the microarchitecture, presence of ECM proteins, biocompatibility and cell proliferation. dECM has also been processed as scaffolds and drug-delivery vehicles, and utilized for regeneration.

Hot or cold: Bioengineering immune contextures into in vitro patient-derived tumor models

In the past decade, immune checkpoint inhibitors (ICI) have proven to be tremendously effective for a subset of cancer patients. However, it is difficult to predict the response of individual patients and efforts are now directed at understanding the mechanisms of ICI resistance. Current models of patient tumors poorly recapitulate the immune contexture, which describe immune parameters that are associated with patient survival. In this Review, we discuss parameters that influence the induction of different immune contextures found within tumors and how engineering strategies may be leveraged to recapitulate these contextures to develop the next generation of immune-competent patient-derived in vitro models.

Electrohydrodynamic jet 3D printing in biomedical applications

Electrohydrodynamic Jet 3D Printing (e-jetting) is a promising technique developed from electrospinning, which enables precise fiber deposition in a layer-by-layer fashion with customized designs. Several studies have verified that e-jetted scaffolds were able to support cell attachment, proliferation, and extracellular matrix formation, as well as cell infiltration into the scaffold due to the well-defined pores. Besides, e-jetting has also been combined with other techniques to incorporate biomaterials (e.g., hydrogels and cell spheroids) that could not be e-jetted, to promote the biological performance of the scaffold. In the recent decade, applying e-jetting in the fabrication of tissue-engineered scaffolds has drawn a lot of interest. Moreover, efforts have been put to develop varied scaffolds for some specific biomedical applications such as cartilage, tendon, and blood vessel, which exhibited superior mechanical properties and promoted cell behaviors including cellular alignment and differentiation. This review article also provides the reader with some crucial considerations and major limitations of e-jetting, such as scaffold design, printability of large-scale constructs, applicable biomaterials, and cell behaviors. Overall, this review article expounds on perspectives in the context of development and biomedical applications of this technique. STATEMENT OF SIGNIFICANCE: E-jetting technique is able to produce fibers with diameter in micrometer scale, which has been considered as a promising 3D printing technique. This technique has shown promise for regeneration of tissue engineered scaffolds with well-defined structures, which has been reported to apply in regeneration of different tissue types. The superior controllability of the process endows the feasibility of constructing multi-scale scaffolds with great biological mimicry and cellular infiltration. The incorporation of other biomaterials into the e-jetted networks further reinforces the scope of applications as compared to e-jetted scaffolds only. There is no doubt that e-jetting will be a great tool for tissue engineered scaffolding, and this review article will give overall perspectives in this topic.

Multi-scale hierarchical scaffolds with aligned micro-fibers for promoting cell alignment

Cell alignment plays an essential role in cytoskeleton reorganization, extracellular matrix remodeling, and biomechanical properties regulation of tissues such as vascular tissues, cardiac muscles, and tendons. Based on the natural-oriented features of cells in native tissues, various biomimetic scaffolds have been reported with the introduction of well-arranged ultrafine fibers to induce cell alignment. However, it is still a challenge to fabricate scaffolds with suitable mechanical properties, biomimetic microenvironment, and ability to promote cell alignment. In this paper, we propose an integrated 3D printing system to fabricate multi-scale hierarchical scaffolds combined with meso-, micro-, and nano-fibrous filaments, in which the meso-, micro-, and nano-fibers fabricated via fused deposition modeling, melt electrospining writing, and solution electrospining can provide structural support, promote cell alignment, and create a biomimetic microenvironment to facilitate cell function, respectively. The plasma surface modification was performed improve the surface wettability of the scaffolds by measuring the contact angle. The obtainedin vitrobiological results validate the ability of multi-scale hierarchical scaffolds to enhance cell adhesion and proliferation, and promote cell alignment with the guidance of the aligned microfibers produced via melt electrospining writing in hierarchical scaffolds.

Solution-Based Processing for Scaffold Fabrication in Tissue Engineering Applications: A Brief Review

The fabrication of 3D scaffolds is under wide investigation in tissue engineering (TE) because of its incessant development of new advanced technologies and the improvement of traditional processes. Currently, scientific and clinical research focuses on scaffold characterization to restore the function of missing or damaged tissues. A key for suitable scaffold production is the guarantee of an interconnected porous structure that allows the cells to grow as in native tissue. The fabrication techniques should meet the appropriate requirements, including feasible reproducibility and time- and cost-effective assets. This is necessary for easy processability, which is associated with the large range of biomaterials supporting the use of fabrication technologies. This paper presents a review of scaffold fabrication methods starting from polymer solutions that provide highly porous structures under controlled process parameters. In this review, general information of solution-based technologies, including freeze-drying, thermally or diffusion induced phase separation (TIPS or DIPS), and electrospinning, are presented, along with an overview of their technological strategies and applications. Furthermore, the differences in the fabricated constructs in terms of pore size and distribution, porosity, morphology, and mechanical and biological properties, are clarified and critically reviewed. Then, the combination of these techniques for obtaining scaffolds is described, offering the advantages of mimicking the unique architecture of tissues and organs that are intrinsically difficult to design.

Bismuth subsalicylate incorporated in polycaprolactone-gelatin membranes by electrospinning to prevent bacterial colonization

Periodontitis is a chronic, multifactorial, inflammatory disease characterized by the progressive destruction of the periodontal tissues. Guided tissue regeneration (GTR), involving the use of barrier membranes, is one of the most successful clinical procedures for periodontal therapy. Nevertheless, rapid degradation of the membranes and membrane-related infections are considered two of the major reasons for GTR clinical failure. Recently, integration of non-antibiotic, antimicrobial materials to the membranes has emerged as a novel strategy to face the bacterial infection challenge, without increasing bacterial resistance. In this sense, bismuth subsalicylate (BSS) is a non-antibiotic, metal-based antimicrobial agent effective against different bacterial strains, that has been long safely used in medical treatments. Thus, the aim of the present work was to fabricate fibrillar, non-rapidly bioresorbable, antibacterial GTR membranes composed of polycaprolactone (PCL), gelatin (Gel), and BSS as the antibacterial agent. PCL-G-BSS membranes with three different BSS concentrations (2 wt./v%, 4 wt./v%, and 6 wt./v%) were developed by electrospinning and their morphology, composition, water wettability, mechanical properties, Bi release and degradation rate were characterized. The Cytotoxicity of the membranes was studiedin vitrousing human osteoblasts (hFOB) and gingival fibroblasts (HGF-1), and their antibacterial activity was tested againstAggregatibacter actinomycetemcomitans, Escherichia coli, Porphyromonas gingivalisandStaphylococcus aureus.The membranes obtained exhibited adequate mechanical properties for clinical application, and appropriate degradation rates for allowing periodontal defects regeneration. The hFOB and HGF-1 cells displayed adequate viability when in contact with the lixiviated products from the membranes, and, in general, displayed antibacterial activity against the four bacteria strains tested. Thus, the PCL-G-BSS membranes showed to be appropriate as potential barrier membranes for periodontal GTR treatments.

Using Humidity to Control the Morphology and Properties of Electrospun BioPEGylated Polyhydroxybutyrate Scaffolds

Electrospinning produces nanofibrous scaffolds with potential for tissue engineering and wound repair. Spinning parameters control scaffold morphology and properties. BioPEGylation of polyhydroxybutyrate (PHB) introduces terminal hydrophilic groups into the hydrophobic chain, making this natural-synthetic hybrid copolymer more susceptible to humidity. Varying the humidity from 10 to 50% RH during electrospinning had a relatively little effect on polyhydroxybutyrate (PHB) average fiber and pore diameters, which remained around 3.0 and 8.7 μm, respectively. In contrast, fiber and pore diameters for electrospun bioPEGylated PHB scaffolds varied significantly with humidity, peaking at 30% RH (5.5 and 14.1 μm, respectively). While scaffolds showed little change, hydrophobicity decreased linearly with humidity during electrospinning. Compared to solvent-cast films, electrospun scaffolds showed significantly greater average cell spread. A 108% increase for olfactory ensheathing cells (OECs) cultivated on bioPEGylated PHB scaffolds was proportionally greater than their counterparts on electrospun PHB scaffolds, (70%). OECS grown on BioPEGylated PHB scaffolds were over twice the size, 260 ± 20 μm diameter, than those on PHB electrospun scaffolds, 110 ± 18 μm diameter. Electrospun scaffolds also promoted cell health compared to their solvent-cast counterparts, with increases in the mitochondrial activity of 165 ± 13 and 196 ± 13% for PHB and bioPEGylated PHB, respectively. OECS cultivated on electrospun scaffolds of bioPEGylated PHB had significantly better membrane integrities compared to their counterparts on solvent-cast films, 47 ± 5% reducing to 17 ± 6%. The combination of bioPEGylation and humidity during electrospinning permitted significant controllable changes to scaffold morphology and properties. These changes resulted in the significantly greater promotion of cell growth on electrospun bioPEGylated PHB scaffolds compared to their solvent-cast counterparts and electrospun PHB.