Resorbable polymer electrospun nanofibers: History, shapes and application for tissue engineering

Electrospinning and electrospun polysaccharide-based nanofiber membranes: A review

The electrospinning technology has set off a tide and given rise to the attention of a widespread range of research territories, benefiting from the enhancement of nanofibers which made a spurt of progress. Nanofibers, continuously produced via electrospinning technology, have greater specific surface area and higher porosity and play a non-substitutable key role in many fields. Combined with the degradability and compatibility of the natural structure characteristics of polysaccharides, electrospun polysaccharide nanofiber membranes gradually infiltrate into the life field to help filter air contamination particles and water pollutants, treat wounds, keep food fresh, monitor electronic equipment, etc., thus improving the life quality. Compared with the evaluation of polysaccharide-based nanofiber membranes in a specific field, this paper comprehensively summarized the existing electrospinning technology and focused on the latest research progress about the application of polysaccharide-based nanofiber in different fields, represented by starch, chitosan, and cellulose. Finally, the benefits and defects of electrospun are discussed in brief, and the prospects for broadening the application of polysaccharide nanofiber membranes are presented for the glorious expectation dedicated to the progress of the eras.

Nature-Inspired Wet Drug Delivery Platforms

Nature has created various organisms with unique chemical components and multi-scale structures (e.g., foot proteins, toe pads, suckers, setose gill lamellae) to achieve wet adhesion functions to adapt to their complex living environments. These organisms can provide inspirations for designing wet adhesives with mediated drug release behaviors in target locations of biological surfaces. They exhibit conformal and enhanced wet adhesion, addressing the bottleneck of weaker tissue interface adhesion in the presence of body fluids. Herein, it is focused on the research progress of different wet adhesion and bioinspired fabrications, including adhesive protein-based adhesion and inspired adhesives (e.g., mussel adhesion); capillarity and Stefan adhesion and inspired adhesive surfaces (e.g., tree frog adhesion); suction-based adhesion and inspired suckers (e.g., octopus' adhesion); interlocking and friction-based adhesion and potential inspirations (e.g., mayfly larva and teleost adhesion). Other secreted protein-induced wet adhesion is also reviewed and various suckers for other organisms and their inspirations. Notably, one representative application scenario of these bioinspired wet adhesives is highlighted, where they function as efficient drug delivery platforms on target tissues and/or organs with requirements of both controllable wet adhesion and optimized drug release. Finally, the challenges of these bioinspired wet drug delivery platforms in the future is presented.

Silk fibroin-derived electrospun materials for biomedical applications: A review

Electrospinning is a versatile technique for fabricating polymeric fibers with diameters ranging from micro- to nanoscale, exhibiting multiple morphologies and arrangements. By combining silk fibroin (SF) with synthetic and/or natural polymers, electrospun materials with outstanding biological, chemical, electrical, physical, mechanical, and optical properties can be achieved, fulfilling the evolving biomedical demands. This review highlights the remarkable versatility of SF-derived electrospun materials, specifically focusing on their application in tissue regeneration (including cartilage, cornea, nerves, blood vessels, bones, and skin), disease treatment (such as cancer and diabetes), and the development of controlled drug delivery systems. Additionally, we explore the potential future trends in utilizing these nanofibrous materials for creating intelligent biomaterials, incorporating biosensors and wearable sensors for monitoring human health, and also discuss the bottlenecks for its widespread use. This comprehensive overview illuminates the significant impact and exciting prospects of SF-derived electrospun materials in advancing biomedical research and applications.

Recent advances in nano-scaffolds for tissue engineering applications: Toward natural therapeutics

Among the promising methods for repairing or replacing tissue defects in the human body and the hottest research topics in medical science today are regenerative medicine and tissue engineering. On the other hand, nanotechnology has been expanded into different areas of regenerative medicine and tissue engineering due to its essential benefits in improving performance in various fields. Nanotechnology, a helpful strategy in tissue engineering, offers new solutions to unsolved problems. Especially considering the excellent physicochemical properties of nanoscale structures, their application in regenerative medicine has been gradually developed, and a lot of research has been conducted in this field. In this regard, various nanoscale structures, including nanofibers, nanosheets, nanofilms, nano-clays, hollow spheres, and different nanoparticles, have been developed to advance nanotechnology strategies with tissue repair goals. Here, we comprehensively review the application of the mentioned nanostructures in constructing nanocomposite scaffolds for regenerative medicine and tissue engineering. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement Diagnostic Tools > Biosensing.

From Poly(glycerol itaconate) Gels to Novel Nonwoven Materials for Biomedical Applications

Electrospinning is a process that has attracted significant interest in recent years. It provides the opportunity to produce nanofibers that mimic the extracellular matrix. As a result, it is possible to use the nonwovens as scaffolds characterized by high cellular adhesion. This work focused on the synthesis of poly(glycerol itaconate) (PGItc) and preparation of nonwovens based on PGItc gels and polylactide. PGItc gels were synthesized by a reaction between itaconic anhydride and glycerol. The use of a mixture of PGItc and PLA allowed us to obtain a material with different properties than with stand-alone polymers. In this study, we present the influence of the chosen ratios of polymers and the OH/COOH ratio in the synthesized PGItc on the properties of the obtained materials. The addition of PGItc results in hydrophilization of the nonwovens' surface without disrupting the high porosity of the fibrous structure. Spectral and thermal analyzes are presented, along with SEM imagining. The preliminary cytotoxicity research showed that nonwovens were non-cytotoxic materials. It also helped to pre-determine the potential application of PGItc + PLA nonwovens as subcutaneous tissue fillers or drug delivery systems.

Overview of Electrospinning for Tissue Engineering Applications

Tissue engineering (TE) is an emerging field of study that incorporates the principles of biology, medicine, and engineering for designing biological substitutes to maintain, restore, or improve tissue functions with the goal of avoiding organ transplantation. Amongst the various scaffolding techniques, electrospinning is one of the most widely used techniques to synthesise a nanofibrous scaffold. Electrospinning as a potential tissue engineering scaffolding technique has attracted a great deal of interest and has been widely discussed in many studies. The high surface-to-volume ratio of nanofibres, coupled with their ability to fabricate scaffolds that may mimic extracellular matrices, facilitates cell migration, proliferation, adhesion, and differentiation. These are all very desirable properties for TE applications. However, despite its widespread use and distinct advantages, electrospun scaffolds suffer from two major practical limitations: poor cell penetration and poor load-bearing applications. Furthermore, electrospun scaffolds have low mechanical strength. Several solutions have been offered by various research groups to overcome these limitations. This review provides an overview of the electrospinning techniques used to synthesise nanofibres for TE applications. In addition, we describe current research on nanofibre fabrication and characterisation, including the main limitations of electrospinning and some possible solutions to overcome these limitations.

Tissue-Engineered Nanomaterials Play Diverse Roles in Bone Injury Repair

Nanomaterials with bone-mimicking characteristics and easily internalized by the cell could create suitable microenvironments in which to regulate the therapeutic effects of bone regeneration. This review provides an overview of the current state-of-the-art research in developing and using nanomaterials for better bone injury repair. First, an overview of the hierarchical architecture from the macroscale to the nanoscale of natural bone is presented, as these bone tissue microstructures and compositions are the basis for constructing bone substitutes. Next, urgent clinical issues associated with bone injury that require resolution and the potential of nanomaterials to overcome them are discussed. Finally, nanomaterials are classified as inorganic or organic based on their chemical properties. Their basic characteristics and the results of related bone engineering studies are described. This review describes theoretical and technical bases for the development of innovative methods for repairing damaged bone and should inspire therapeutic strategies with potential for clinical applications.

Formulation and Characterization of Electrospun Nanofibers for Melatonin Ocular Delivery

The poor ocular bioavailability of melatonin (MEL) limits the therapeutic action the molecule could exert in the treatment of ocular diseases. To date, no study has explored the use of nanofiber-based inserts to prolong ocular surface contact time and improve MEL delivery. Here, the electrospinning technique was proposed to prepare poly (vinyl alcohol) (PVA) and poly (lactic acid) (PLA) nanofiber inserts. Both nanofibers were produced with different concentrations of MEL and with or without the addition of Tween^® 80. Nanofibers morphology was evaluated by scanning electron microscopy. Thermal and spectroscopic analyses were performed to characterize the state of MEL in the scaffolds. MEL release profiles were observed under simulated physiological conditions (pH 7.4, 37 °C). The swelling behavior was evaluated by a gravimetric method. The results confirmed that submicron-sized nanofibrous structures were obtained with MEL in the amorphous state. Different MEL release rates were achieved depending on the nature of the polymer. Fast (20 min) and complete release was observed for the PVA-based samples, unlike the PLA polymer, which provided slow and controlled MEL release. The addition of Tween^® 80 affected the swelling properties of the fibrous structures. Overall, the results suggest that membranes could be an attractive vehicle as a potential alternative to liquid formulations for ocular administration of MEL.

Biodegradable Polymer Electrospinning for Tendon Repairment

With the degradation after aging and the destruction of high-intensity exercise, the frequency of tendon injury is also increasing, which will lead to serious pain and disability. Due to the structural specificity of the tendon tissue, the traditional treatment of tendon injury repair has certain limitations. Biodegradable polymer electrospinning technology with good biocompatibility and degradability can effectively repair tendons, and its mechanical properties can be achieved by adjusting the fiber diameter and fiber spacing. Here, this review first briefly introduces the structure and function of the tendon and the repair process after injury. Then, different kinds of biodegradable natural polymers for tendon repair are summarized. Then, the advantages and disadvantages of three-dimensional (3D) electrospun products in tendon repair and regeneration are summarized, as well as the optimization of electrospun fiber scaffolds with different bioactive materials and the latest application in tendon regeneration engineering. Bioactive molecules can optimize the structure of these products and improve their repair performance. Importantly, we discuss the application of the 3D electrospinning scaffold's superior structure in different stages of tendon repair. Meanwhile, the combination of other advanced technologies has greater potential in tendon repair. Finally, the relevant patents of biodegradable electrospun scaffolds for repairing damaged tendons, as well as their clinical applications, problems in current development, and future directions are summarized. In general, the use of biodegradable electrospun fibers for tendon repair is a promising and exciting research field, but further research is needed to fully understand its potential and optimize its application in tissue engineering.

Activation of KLF6 by titanate nanofibers and regulatory roles of KLF6 on ATF3 in the endothelial monolayer and mouse aortas

Although titanium (Ti)-based nanomaterials (NMs) were traditionally considered as biologically inert materials, it was recently reported that Ti-based NMs induce adverse vascular effects by inhibiting Kruppel-like factor 2 (KLF2) and/or KLF4, vasoprotective KLFs with well-documented regulatory activity in NO signaling. However, the potential roles of other KLFs are not clear. KLF6 was recently identified as an important KLF involved in regulating endothelial dysfunction, inflammation, and angiogenesis, therefore, this study investigated the influence of titanate nanofibers (TiNFs) on KLF6-mediated events. Ingenuity pathway analysis (IPA) showed that TiNFs altered the expression of a panel of KLF6-related genes: KLF6-mediated gene ontology (GO) terms were altered, categories including cytokine-mediated signaling pathways, transcription factor (TF) functions and membrane-bound organelles. Additionally, RT-PCR confirmed that TiNFs increased KLF6 activating transcription factor 3 (ATF3), a TF involved in endoplasmic reticulum (ER) stress, and ELISA confirmed the increase of soluble monocyte chemotactic protein 1 (sMCP-1), a KLF6-related inflammatory cytokine. Interestingly, the activation of klf6, atf3 and C-C motif chemokine ligand 2 (ccl2; mcp-1 encoding gene) was observed in aortas of mice following one-time intravenous injection but not intratracheal instillation of TiNFs (100 μg per mouse), indicating a need for direct contact with NMs to activate klf6-mediated pathways in vivo. In endothelial cells, KLF6 knockdown inhibited the expression of ATF3 but not CCL2, suggesting the regulatory role of KLF6 in ATF3 expression. Overall, this study uncovered a previously unknown role of KLF6 in TiNF-induced vascular effects both in vitro and in vivo.

Recent Advances in Metal-Organic Framework (MOF) Asymmetric Membranes/Composites for Biomedical Applications

Metal-organic frameworks (MOFs) are a new class of porous crystalline materials composed of metal and organic material. MOFs have fascinating properties, such as fine tunability, large specific surface area, and high porosity. MOFs are widely used for environmental protection, biosensors, regenerative medicine, medical engineering, cell therapy, catalysts, and drug delivery. Recent studies have reported various significant properties of MOFs for biomedical applications, such as drug detection and delivery. In contrast, MOFs have limitations such as low stability and low specificity in binding to the target. MOF-based membranes improve the stability and specificity of conventional MOFs by increasing the surface area and developing the possibility of MOF-ligand binding, while conjugated membranes dramatically increase the area of active functional groups. This special property makes them attractive for drug and biosensor fabrication, as both the spreading and solubility components of the porosity can be changed. Asymmetric membranes are a structure with high potential in the biomedical field, due to the different characteristics on its two surfaces, the possibility of adjusting various properties such as the size of porosity, transfer rate and selectivity, and surface properties such as hydrophilicity and hydrophobicity. MOF assisted asymmetric membranes can provide a platform with different properties and characteristics in the biomedical field. The latest version of MOF materials/membranes has several potential applications, especially in medical engineering, cell therapy, drug delivery, and regenerative medicine, which will be discussed in this review, along with their advantages, disadvantages, and challenges.

Curcumin-encapsulated hydrophilic gelatin nanoparticle to stabilize fish oil-loaded Pickering emulsion

Herein, pH-cycle method was explored to prepare curcumin-encapsulated hydrophilic bovine bone gelatin (BBG/Cur) nanoparticle and then the obtained nanoparticle was applied to stabilize fish oil-loaded Pickering emulsion. The nanoparticle had a high encapsulation efficiency (93.9 ± 0.5 %) and loading capacity (9.4 ± 0.1 %) for curcumin. The nanoparticle-stabilized emulsion had higher emulsifying activity index (25.1 ± 0.9 m²/g) and lower emulsifying stability index (161.5 ± 18.8 min) than BBG-stabilized emulsion. The pH affected the initial droplet sizes and creaming index values of the Pickering emulsions: pH 11.0 < pH 5.0 ≈ pH 7.0 ≈ pH 9.0 < pH 3.0. Curcumin provided obvious antioxidant effect for the emulsions, which was also dependent on pH. The work suggested pH-cycle method could be used to prepare hydrophobic antioxidant-encapsulated hydrophilic protein nanoparticle. It also provided basic information on the development of protein nanoparticles for Pickering emulsion stabilization.

Electrospinning Inorganic Nanomaterials to Fabricate Bionanocomposites for Soft and Hard Tissue Repair

Tissue engineering (TE) has attracted the widespread attention of the research community as a method of producing patient-specific tissue constructs for the repair and replacement of injured tissues. To date, different types of scaffold materials have been developed for various tissues and organs. The choice of scaffold material should take into consideration whether the mechanical properties, biodegradability, biocompatibility, and bioresorbability meet the physiological properties of the tissues. Owing to their broad range of physico-chemical properties, inorganic materials can induce a series of biological responses as scaffold fillers, which render them a good alternative to scaffold materials for tissue engineering (TE). While it is of worth to further explore mechanistic insight into the use of inorganic nanomaterials for tissue repair, in this review, we mainly focused on the utilization forms and strategies for fabricating electrospun membranes containing inorganic components based on electrospinning technology. A particular emphasis has been placed on the biological advantages of incorporating inorganic materials along with organic materials as scaffold constituents for tissue repair. As well as widely exploited natural and synthetic polymers, inorganic nanomaterials offer an enticing platform to further modulate the properties of composite scaffolds, which may help further broaden the application prospect of scaffolds for TE.

Recent progress on electrospun nanofibrous polymer membranes for water and air purification: A review

Developing new polymer membranes with excellent thermal, mechanical, and chemical stability has shown great potential for various environmental remediation applications such as wastewater treatment and air filtration. Polymer membranes have been widely investigated over the past years and utilized to overcome severe ecological issues. Membrane-based technologies play a critical role in water purification and air filtration with the ability to act efficiently and sustainably. Electrospun nanofiber membranes have displayed excellent performance in removing various contaminants from water, such as bacteria, dyes, heavy metals, and oil. These nanofibrous membranes have shown good potential to filter the air from tiny particles, volatile organic compounds, and toxic gases. The performance of polymer membranes can be enhanced by fine-tuning polymer structure, varying surface properties, and strengthening overall membrane porosity. In this review, we discuss the involvement of electrospun nanofibrous membranes in different environmental remediation applications. It further reviews the recent progress of polymer membrane development by utilizing nanoparticles and naturally occurring polymers.

Preparation of Cross-Linked Bovine Tendon Acellular Fibers and Study of Their Biophysical and Chemical Properties

To explore the effect of glutaraldehyde (GA) and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) cross-linking on the biophysical and chemical properties of acellular scaffold to better provide suitable donor materials for tendon reconstruction. GA and EDC with different concentrations and action time gradients were used to cross-link the acellular scaffold. By detecting the collagen content in the cross-linked scaffold and the cytotoxicity, the cross-linking scheme with minimal damage to the scaffold and minimal cytotoxicity was explored for subsequent studies. The biomechanical properties (durability, elastic modulus, stressmax) of the scaffolds in GA, EDC, acellular scaffold, and tendon groups were compared, and the scaffold rat models were constructed to further evaluate their in vivo histocompatibility. Under different concentration gradients, the collagen content of the scaffolds in the GA and EDC groups had no obvious difference. When 0.5% GA was cross-linked for 24 h, and the mass ratio of EDC (1:2) was cross-linked for 4 h, the inhibition rate of the scaffold extract on fibroblasts was the lowest. In the mechanical property test, the Stressmax, durability, and elastic modulus of the cross-linked acellular scaffolds were significantly improved than those before cross-linking, and the elastic modulus of the EDC acellular scaffold was similar to that of the bovine tendon. In the compatibility test, compared with the acellular scaffold group, fibroblast activity in the GA group decreased obviously, and the scaffold implanted in rat models led to a persistent chronic inflammatory reaction. However, cells in the EDC group could maintain good activity. Moreover, the scaffold had good compatibility with rats and did not cause an obvious inflammatory reaction. EDC cross-linking scheme will not damage the acellular scaffold, and the cytotoxicity of the obtained scaffold is controllable. Additionally, EDC cross-linked acellular scaffold has mechanical properties similar to normal tendons and excellent histocompatibility.

Electrospun Fibers: Versatile Approaches for Controlled Release Applications

Electrospinning has been one of the most attractive methods of fiber fabrication in the last century. A lot of studies have been conducted, especially in tissue engineering and drug delivery using electrospun fibers. Loading many different drugs and bioactive agents on or within these fibers potentiates the efficacy of such systems; however, there are still no commercial products with this technology available in the market. Various methods have been developed to improve the mechanical and physicochemical behavior of structures toward more controllable delivery systems in terms of time, place, or quantity of release. In this study, most frequent methods used for the fabrication of controlled release electrospun fibers have been reviewed. Although there are a lot of achievements in the fabrication of controlled release fibers, there are still many challenges to be solved to reach a qualified, reproducible system applicable in the pharmaceutical industry.

Natural and Synthetic Polymer Scaffolds Comprising Upconversion Nanoparticles as a Bioimaging Platform for Tissue Engineering

Modern biocompatible materials of both natural and synthetic origin, in combination with advanced techniques for their processing and functionalization, provide the basis for tissue engineering constructs (TECs) for the effective replacement of specific body defects and guided tissue regeneration. Here we describe TECs fabricated using electrospinning and 3D printing techniques on a base of synthetic (polylactic-co-glycolic acids, PLGA) and natural (collagen, COL, and hyaluronic acid, HA) polymers impregnated with core/shell β-NaYF₄:Yb³⁺,Er³⁺/NaYF₄ upconversion nanoparticles (UCNPs) for in vitro control of the tissue/scaffold interaction. Polymeric structures impregnated with core/shell β-NaYF₄:Yb³⁺,Er³⁺/NaYF₄ nanoparticles were visualized with high optical contrast using laser irradiation at 976 nm. We found that the photoluminescence spectra of impregnated scaffolds differ from the spectrum of free UCNPs that could be used to control the scaffold microenvironment, polymer biodegradation, and cargo release. We proved the absence of UCNP-impregnated scaffold cytotoxicity and demonstrated their high efficiency for cell attachment, proliferation, and colonization. We also modified the COL-based scaffold fabrication technology to increase their tensile strength and structural stability within the living body. The proposed approach is a technological platform for "smart scaffold" development and fabrication based on bioresorbable polymer structures impregnated with UCNPs, providing the desired photoluminescent, biochemical, and mechanical properties for intravital visualization and monitoring of their behavior and tissue/scaffold interaction in real time.

Effect of extraction methods on the properties of tilapia scale gelatins

Three types of tilapia scale gelatins (hot water-pretreated gelatin, HWG; acetic acid-pretreated gelatin, AAG; and pepsin enzyme-pretreated gelatin, PEG) were extracted and their gel strength, foaming properties, and emulsifying properties were analyzed. They had different gel strength values: AAG (370 ± 10 g Bloom) > HWG (320 ± 10 g Bloom) > PEG (280 ± 10 g Bloom). The creaming index values of tilapia scale gelatin-stabilized fish oil-loaded emulsions were dependent on gelatin type (HWG ≈ AAG > PEG) at low gelatin concentration (2 mg/mL), whereas they were similar and low (8-10 %) at high gelatin concentration (10 mg/mL). Extraction methods had no consistently significant effects on the gelatin foaming properties. In summary, tilapia scale gelatins had better gel strength and foaming properties and similar or even better emulsifying properties than mammalian gelatins. Therefore, tilapia scales could be a potential source of gelatins to replace mammalian gelatins.

Recent Progress in Electrospun Polyacrylonitrile Nanofiber-Based Wound Dressing

Bleeding control plays a very important role in worldwide healthcare, which also promotes research and development of wound dressings. The wound healing process involves four stages of hemostasis, inflammation, proliferation and remodeling, which is a complex process, and wound dressings play a huge role in it. Electrospinning technology is simple to operate. Electrospun nanofibers have a high specific surface area, high porosity, high oxygen permeability, and excellent mechanical properties, which show great utilization value in the manufacture of wound dressings. As one of the most popular reactive and functional synthetic polymers, polyacrylonitrile (PAN) is frequently explored to create nanofibers for a wide variety of applications. In recent years, researchers have invested in the application of PAN nanofibers in wound dressings. Research on spun nanofibers is reviewed, and future development directions and prospects of electrospun PAN nanofibers for wound dressings are proposed.

Aloe vera incorporated starch-64S bioactive glass-quail egg shell scaffold for promotion of bone regeneration

Simultaneous promotion of osteoconductive and osteoinductive characteristics through combining bioactive glasses with natural polymers is still a challenge in bone tissue engineering. Starch, 64S bioactive glass (BG), aloe vera (AV) and quail eggshell powder (QE) were utilized to achieve biodegradable, bioactive, biocompatible and mechanically potent multifunctional scaffolds, using freeze-drying mechanism. Cell viability for starch-BG-AV-QE scaffolds at 3 and 7 day intervals was reported to be over 95 %. Acridine orange staining was employed to study live/dead cells cultured on the scaffolds. The high sufficiency of starch-BG-AV-QE scaffolds in osteogenic differentiation and extracellular matrix mineralization was confirmed through alkaline phosphatase activity and alizarin red staining assessments after 7 and 14 days of cell culture. High compressive strength, managed biodegradability and expression of osteocalcin and osteopontin as late markers of osteogenic differentiation were also reached in the range of 30-75 % for starch-BG-AV-QE scaffolds. Hence, starch-BG-AV-QE scaffolds with ideal physico-mechanical and biological characteristics can be considered as promising candidates for promotion of bone regeneration.

Electrospun-Fibrous-Architecture-Mediated Non-Viral Gene Therapy Drug Delivery in Regenerative Medicine

Gene-based therapy represents the latest advancement in medical biotechnology. The principle behind this innovative approach is to introduce genetic material into specific cells and tissues to stimulate or inhibit key signaling pathways. Although enormous progress has been achieved in the field of gene-based therapy, challenges connected to some physiological impediments (e.g., low stability or the inability to pass the cell membrane and to transport to the desired intracellular compartments) still obstruct the exploitation of its full potential in clinical practices. The integration of gene delivery technologies with electrospun fibrous architectures represents a potent strategy that may tackle the problems of stability and local gene delivery, being capable to promote a controlled and proficient release and expression of therapeutic genes in the targeted cells, improving the therapeutic outcomes. This review aims to outline the impact of electrospun-fibrous-architecture-mediated gene therapy drug delivery, and it emphatically discusses the latest advancements in their formulation and the therapeutic outcomes of these systems in different fields of regenerative medicine, along with the main challenges faced towards the translation of promising academic results into tangible products with clinical application.

Characterization of Electrospun Poly(ε-caprolactone) Nano/Micro Fibrous Membrane as Scaffolds in Tissue Engineering: Effects of the Type of Collector Used

Electrospinning is an electrohydrodynamic technique that transforms a polymer solution into nano/microscopic diameter fibers under the influence of a high-voltage electric field. Its use in the fabrication of nano/micro fibrous membranes as scaffolds for tissue engineering has increased rapidly in recent years due to its efficiency and reproducibility. The objective of this study is to show how the use of the same polymeric solution (polycaprolactone 9% w/v in chloroform: isopropanol 50:50) and identical electrohydrodynamic deposition parameters produces fibers with different characteristics using a flat collector platform with movements in the X and Y axes vs. a conventional rotary collector. The manufactured nano/microfibers show significant differences in most of their characteristics (morphology, roughness, hydrophilicity, and mechanical properties). Regarding the diameter and porosity of the fibers, the results were similar. Given that scaffolds must be designed to guarantee adequate survival and the proliferation and migration of a certain cell type, in this study we analyze how the variations in the characteristics of the fibers obtained are essential to defining their potential application.

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.

Study on the Influence of Shear Stress and Pulse Electrical Stimulation to the Growth of Cardiomyocytes

Engineered myocardial tissue is expected to be used in the treatment of myocardial defects and other diseases, and one of the keys is to construct a suitable environment for the culture of myocardial tissue in vitro. In this study, flow shear stress and pulse electrical stimulation were applied to cardiomyocytes with a self-designed device by simulating the mechanical and electrical physiological microenvironment of myocardial tissue. The strength and duration of pulse electrical stimulation as well as the intensity of shear stress were studied in detail to optimize the experimental parameters. Concretely, 100 mV pulse electrical stimulation (1 Hz and 10 ms pulse width) and 10 dyn/cm² shear stress were used for studying the influence of combined mechanical-electrical stimulation to the growth of cardiomyocytes. The mechanical factor of the combined stimulation promoted the expression of α-cardiac actin mRNA, the electrical factor caused an increase in Cx-43 mRNA expression, and shear stress and pulse electrical stimulation showed a synergistic action on the expression of GATA-4 mRNA. It indicated that combined mechanical-electrical stimulation had a better effect on the functionalized culture of cardiomyocytes, which provided an important theoretical basis for the further construction of in vitro engineered myocardial tissue.

Anhydride structures affect the acylation modification and emulsion stabilization ability of mammalian and fish gelatins

In this work, ring-like anhydrides (C4, C5, and C6) with different sizes and succinic anhydrides (C4, C10, C12, C14, and C16) with different side chain lengths were used to modify bovine bone gelatin (BBG) and cold-water fish skin gelatin (CFG), and the effect of acylated gelatins on fish oil-loaded emulsions stability was explored. The results showed that the degree of N-acylation decreased with increased ring sizes or side chain lengths, and the surface hydrophobicity of acylated gelatins increased with increased anhydride carbon numbers. Acylated CFGs had higher droplet stability and lower liquid-gel transition time than acylated BBGs. Only BBG-C12 had a slight increase on the creaming stability among these acylated gelatins. These results demonstrated that the gelatins could be modified by all the anhydrides and their emulsion stabilization ability was dependent on the gelatin type and anhydride structure. The results could be beneficial for protein-based emulsifier development and application.

Recent Progress in Electrospun Nanofiber-Based Degenerated Intervertebral Disc Repair

Annulus fibrosus fissure and fibrosis of nucleus pulposus are severe morphological characteristics of intervertebral disc degeneration. Currently, surgery or drugs are used to relieve pain in such cases. Tissue engineering is a new multidisciplinary strategy with great potential for use in joint replacement and organ regeneration. Based on the natural anatomy of intervertebral discs, intervertebral disc scaffolds are fabricated by exploiting the special arrangement of extracellular matrix fibers. Electrospun nanofibers possess clear advantages in repairing degenerated intervertebral discs. This article reviews and summarizes recently developed methods for improving and fabricating electrospun nanofiber annulus fibrosus scaffolds in terms of nanofiber alignment, material selection, loading additives, and the progress made in combining other advanced technologies with electrospun nanofibers. In addition, the improvement in mechanical properties and biocompatibility of nucleus pulposus scaffolds by electrospun nanofiber-reinforced hydrogels is discussed. Finally, complete intervertebral disc scaffolds can be fabricated using the disc-like angle-ply structure and other emerging fabrication methods. Taken together, electrospun nanofiber intervertebral disc scaffolds are promising for clinical applications.

Development and Characterization of pH-Dependent Cellulose Acetate Phthalate Nanofibers by Electrospinning Technique

The aim of this work was to obtain pH-dependent nanofibers with an electrospinning technique as a novel controlled release system for the treatment of periodontal disease (PD). Cellulose acetate phthalate (CAP) was selected as a pH-sensitive and antimicrobial polymer. The NF was optimized according to polymeric dispersion variables, polymer, and drug concentration, and characterized considering morphology, diameter, entrapment efficiency (EE), process efficiency (PE), thermal properties, and release profiles. Two solvent mixtures were tested, and CHX-CAP-NF prepared with acetone/ethanol at 12% w/v of the polymer showed a diameter size of 934 nm, a uniform morphology with 42% of EE, and 55% of PE. Meanwhile, CHX-CAP-NF prepared with acetone/methanol at 11% w/v of polymer had a diameter of 257 nm, discontinuous nanofiber morphology with 32% of EE, and 40% of PE. EE and PE were dependent on the polymer concentration and the drug used in the formulation. Studies of differential scanning calorimetry (DSC) showed that the drug was dispersed in the NF matrix. The release profiles of CHX from CHX-CAP-NF followed Fickian diffusion dependent on time (t^0.43−0.45), suggesting a diffusion–erosion process and a matrix behavior. The NF developed could be employed as a novel drug delivery system in PD.

Phenylalanine-based poly(ester urea)s composite films with nitric oxide-releasing capability for anti-biofilm and infected wound healing applications

Infected wounds show delayed and incomplete healing processes and even render patients at a high risk of death due to the formed bacterial biofilms in the wound site, which protect bacteria against antimicrobial treatments and immune response. Nitric oxide based therapy is considered a promising strategy for eliminating biofilms and enhancing wound healing, which encounters a significant challenge of controlling the NO release behavior at the wound site. Herein, a kind of phenylalanine based poly(ester urea)s with high thermal stability are synthesized and fabricated to electrospun films as NO loading vehicle for infected wound treatment. The resultant films can continuously and stably release nitric oxide for 360 h with a total concentration of 1.15 μmol L^-1, which presents obvious advantages in killing the bacteria and removing biofilms. The results exhibit the films have no cytotoxicity and may accelerate the wound repair without causing inflammation, hemolysis, or cytotoxic reactions as well as stimulate the proliferation of fibroblasts and increase the synthesis of collagen. Therefore, the films may be a suitable NO releasing dressing for removing biofilms and repairing infected wounds.

Research progress, models and simulation of electrospinning technology: a review

In recent years, nanomaterials have aroused extensive research interest in the world's material science community. Electrospinning has the advantages of wide range of available raw materials, simple process, small fiber diameter and high porosity. Electrospinning as a nanomaterial preparation technology with obvious advantages has been studied, such as its influencing parameters, physical models and computer simulation. In this review, the influencing parameters, simulation and models of electrospinning technology are summarized. In addition, the progresses in applications of the technology in biomedicine, energy and catalysis are reported. This technology has many applications in many fields, such as electrospun polymers in various aspects of biomedical engineering. The latest achievements in recent years are summarized, and the existing problems and development trends are analyzed and discussed.

In Vitro Strategies to Vascularize 3D Physiologically Relevant Models

Vascularization of 3D models represents a major challenge of tissue engineering and a key prerequisite for their clinical and industrial application. The use of prevascularized models built from dedicated materials could solve some of the actual limitations, such as suboptimal integration of the bioconstructs within the host tissue, and would provide more in vivo-like perfusable tissue and organ-specific platforms. In the last decade, the fabrication of vascularized physiologically relevant 3D constructs has been attempted by numerous tissue engineering strategies, which are classified here in microfluidic technology, 3D coculture models, namely, spheroids and organoids, and biofabrication. In this review, the recent advancements in prevascularization techniques and the increasing use of natural and synthetic materials to build physiological organ-specific models are discussed. Current drawbacks of each technology, future perspectives, and translation of vascularized tissue constructs toward clinics, pharmaceutical field, and industry are also presented. By combining complementary strategies, these models are envisioned to be successfully used for regenerative medicine and drug development in a near future.

Electrospun natural rubber latex biocomposite for scaffolds in tissue engineering

Fibrous scaffold along with seed cells are essential players for engineered tissue regeneration. Recently, PLGA/epoxidized poly(isoprene) dense membranes have been evaluated for cell growth and have shown satisfactory results. However, porous and fibrous structures suitable for obtaining 3D supports have not yet been evaluated for the PLGA/epoxidized poly(isoprene). The present work aimed to establish the electrospinning conditions for obtaining electrospun membranes with a smaller diameter of fibers and adequate morphology, which were characterized in vitro by their physical, chemical and biological properties. The best electrospun fibers were obtained from the following conditions: an applied voltage of 15 kV, a needle-collector distance of 20 cm and, a flow rate of 5 mL/h. The functional groups of the polymers involved in the blend did not show any changes. The mechanical properties of the electrospun membranes are within the lower limits known to human skin and some soft tissues. The in vitro degradation test showed a loss of mass of approximately 20% in 28 days. Significant adhesion and proliferation of human adipose–derived mesenchymal stem cells were demonstrated, indicating that there was cellular penetration into the scaffold and proliferation. Therefore, the preliminary results suggest that the electrospun PLGA/epoxidized poly(isoprene) membranes have high potential for application as a 3D tissue engineering scaffold.

A Review on Silver Nanoparticles: Classification, Various Methods of Synthesis, and Their Potential Roles in Biomedical Applications and Water Treatment

Recent developments in nanoscience have appreciably modified how diseases are prevented, diagnosed, and treated. Metal nanoparticles, specifically silver nanoparticles (AgNPs), are widely used in bioscience. From time to time, various synthetic methods for the synthesis of AgNPs are reported, i.e., physical, chemical, and photochemical ones. However, among these, most are expensive and not eco-friendly. The physicochemical parameters such as temperature, use of a dispersing agent, surfactant, and others greatly influence the quality and quantity of the synthesized NPs and ultimately affect the material’s properties. Scientists worldwide are trying to synthesize NPs and are devising methods that are easy to apply, eco-friendly, and economical. Among such strategies is the biogenic method, where plants are used as the source of reducing and capping agents. In this review, we intend to debate different strategies of AgNP synthesis. Although, different preparation strategies are in use to synthesize AgNPs such as electron irradiation, optical device ablation, chemical reduction, organic procedures, and photochemical methods. However, biogenic processes are preferably used, as they are environment-friendly and economical. The review covers a comprehensive discussion on the biological activities of AgNPs, such as antimicrobial, anticancer anti-inflammatory, and anti-angiogenic potentials of AgNPs. The use of AgNPs in water treatment and disinfection has also been discussed in detail.

Silver carp scale gelatins for the stabilization of fish oil-loaded emulsions

Herein, three types of silver carp scale gelatins were extracted, and their molecular weight distribution, structural properties, functional properties and emulsifying properties were investigated and discussed. Acetic acid-extracted gelatin (AAG), hot water-extracted gelatin (HWG), and pepsin enzyme-extracted gelatin (PEG) showed similar and four clear bands in sodium dodecyl sulfate-polyacrylamide gel electrophoresis pattern, whereas they showed different β chain amounts and β-sheet percentages. The water-holding capacity values (g/g of gelatin) were: AAG (16.8 ± 1.1) > HWG (14.0 ± 0.7) ≈ PEG (13.5 ± 1.6). The fat-binding capacity values (g/g of gelatin) were: AAG (11.8 ± 0.3) > HWG (9.5 ± 1.3) > PEG (5.3 ± 0.4). Emulsion droplet sizes and creaming index values decreased with the increase of gelatin concentrations for all the fish oil-loaded emulsions stabilized by three types of gelatins. Compared with PEG, AAG and HWG show similar and higher emulsion stability at high gelatin concentration (10 mg/mL). The stabilization mechanism of fish oil-loaded silver carp scale gelatin-stabilized emulsions involved an "extraction method-protein molecular weight distribution-protein molecular structure-molecular interaction-emulsibility-droplet structure-emulsion stability" route. This work would be beneficial for the research on the relationship of structure and function of gelatin and to the comprehensive utilization of aquatic products.

Modern World Applications for Nano-Bio Materials: Tissue Engineering and COVID-19

Over the past years, biomaterials-based nano cues with multi-functional characteristics have been engineered with high interest. The ease in fine tunability with maintained compliance makes an array of nano-bio materials supreme candidates for the biomedical sector of the modern world. Moreover, the multi-functional dimensions of nano-bio elements also help to maintain or even improve the patients' life quality most securely by lowering or diminishing the adverse effects of in practice therapeutic modalities. Therefore, engineering highly efficient, reliable, compatible, and recyclable biomaterials-based novel corrective cues with multipurpose applications is essential and a core demand to tackle many human health-related challenges, e.g., the current COVID-19 pandemic. Moreover, robust engineering design and properly exploited nano-bio materials deliver wide-ranging openings for experimentation in the field of interdisciplinary and multidisciplinary scientific research. In this context, herein, it is reviewed the applications and potential on tissue engineering and therapeutics of COVID-19 of several biomaterials. Following a brief introduction is a discussion of the drug delivery routes and mechanisms of biomaterials-based nano cues with suitable examples. The second half of the review focuses on the mainstream applications changing the dynamics of 21st century materials. In the end, current challenges and recommendations are given for a healthy and foreseeable future.

Synthesis and Characterization of Electrospun Composite Scaffolds Based on Chitosan-Carboxylated Graphene Oxide with Potential Biomedical Applications

This research study reports the development of chitosan/carboxylated graphene oxide (CS/GO-COOH) composite scaffolds with nanofibrous architecture using the electrospinning method. The concept of designed composite fibrous material is based on bringing together the biological properties of CS, mechanical, electrical, and biological characteristics of GO-COOH with the versatility and efficiency of ultra-modern electrospinning techniques. Three different concentrations of GO-COOH were added into a chitosan (CS)-poly(ethylene oxide) (PEO) solution (the ratio between CS/PEO was 3/7 (w/w)) and were used in the synthesis process of composite scaffolds. The effect of GO-COOH concentration on the spinnability, morphological and mechanical features, wettability, and biological properties of engineered fibrous scaffolds was thoroughly investigated. FTIR results revealed the non-covalent and covalent interactions that could take place between the system's components. The SEM micrographs highlighted the nanofibrous architecture of scaffolds, and the presence of GO-COOH sheets along the composite CS/GO-COOH nanofibers. The size distribution graphs showed a decreasing trend in the mean diameter of composite nanofibers with the increase in GO-COOH content, from 141.40 nm for CS/PG 0.1% to 119.88 nm for CS/PG 0.5%. The dispersion of GO-COOH led to composite scaffolds with increased elasticity; the Young's modulus of CS/PG 0.5% (84 ± 4.71 MPa) was 7.5-fold lower as compared to CS/PEO (662 ± 15.18 MPa, p < 0.0001). Contact angle measurements showed that both GO-COOH content and crosslinking step influenced the surface wettability of scaffolds, leading to materials with ~1.25-fold higher hydrophobicity. The in vitro cytocompatibility assessment showed that the designed nanofibrous scaffolds showed a reasonable cellular proliferation level after 72 h of contact with the fibroblast cells.

Electrospun Janus Beads-On-A-String Structures for Different Types of Controlled Release Profiles of Double Drugs

A side-by-side electrospinning process characterized by a home-made eccentric spinneret was established to produce the Janus beads-on-a-string products. In this study, ketoprofen (KET) and methylene blue (MB) were used as model drugs, which loaded in Janus beads-on-a-string products, in which polyvinylpyrrolidone K90 (PVP K90) and ethyl cellulose (EC) were exploited as the polymer matrices. From SEM images, distinct nanofibers and microparticles in the Janus beads-on-a-string structures could be observed clearly. X-ray diffraction demonstrated that all crystalline drugs loaded in Janus beads-on-a-string products were transferred into the amorphous state. ATR-FTIR revealed that the components of prepared Janus nanostructures were compatibility. In vitro dissolution tests showed that Janus beads-on-a-string products could provide typical double drugs controlled-release profiles, which provided a faster immediate release of MB and a slower sustained release of KET than the electrospun Janus nanofibers. Drug releases from the Janus beads-on-a-string products were controlled through a combination of erosion mechanism (linear MB-PVP sides) and a typical Fickian diffusion mechanism (bead KET-EC sides). This work developed a brand-new approach for the preparation of the Janus beads-on-a-string nanostructures using side-by-side electrospinning, and also provided a fresh idea for double drugs controlled release and the potential combined therapy.

Combination Therapy of PTH and Antiresorptive Drugs on Osteoporosis: A Review of Treatment Alternatives

Antiresorptive drugs have been widely used for osteoporosis. Intermittent parathyroid hormone (PTH), an anabolic agent, increases osteoblast production rate and inhibits apoptosis of osteoblasts, thus increasing skeletal mass besides improving bone microarchitecture and strength. Combination therapy for osteoporosis produced great interests and controversies. Therefore, we performed a systematic literature search from PubMed, EMBASE, Scopus, Web of Science, CINDHL, and the Cochrane Database of Systematic Reviews using the search terms PTH or teriparatide combined with bisphosphonate, alendronate, ibandronate, risedronate, raloxifene, denosumab, and zoledronic acid with the limit osteoporosis. At last, 36 related articles were included for further analysis. Findings from previous studies revealed that combination therapy in different conditions of naive or previous bisphosphonate treatment might have different outcomes. The use of combination therapy, however, may be an alternative option among osteoporotic patients with a history of bisphosphonate use. Combined teriparatide with denosumab appear to show the most substantial and clinically relevant skeletal benefits to osteoporotic patients. Additional research is necessary to define optimal methods of developing sequential and/or cyclical combinations of PTH and antiresorptive agents.