Electrospun PLLA nanofiber scaffolds for bladder smooth muscle reconstruction

Investigation of Cell Adhesion and Cell Viability of the Endothelial and Fibroblast Cells on Electrospun PCL, PLGA and Coaxial Scaffolds for Production of Tissue Engineered Blood Vessel

Endothelialization of artificial scaffolds is considered an effective strategy for increasing the efficiency of vascular transplantation. This study aimed to compare the biophysical/biocompatible properties of three different biodegradable fibrous scaffolds: Poly (ɛ-caprolactone) (PCL) alone, Poly Lactic-co-Glycolic Acid (PLGA) alone (both processed using Spraybase^® electrospinning machine), and Coaxial scaffold where the fiber core and sheath was made of PCL and PLGA, respectively. Scaffold structural morphology was assessed by scanning electron microscope and tensile testing was used to investigate the scaffold tension resistance over time. Biocompatibility studies were carried out with human umbilical vein endothelial cells (HUVEC) and human vascular fibroblasts (HVF) for which cell viability (and cell proliferation over a 4-day period) and cell adhesion to the scaffolds were assessed by cytotoxicity assays and confocal microscopy, respectively. Our results showed that all biodegradable polymeric scaffolds are a reliable host to adhere and promote proliferation in HUVEC and HVF cells. In particular, PLGA membranes performed much better adhesion and enhanced cell proliferation compared to control in the absence of polymers. In addition, we demonstrate here that these biodegradable membranes present improved mechanical properties to construct potential tissue-engineered vascular graft.

Development of New Bio-Composite of PEO/Silk Fibroin Blends Loaded with Piezoelectric Material

New bio-composite nanofibers composed of polyethylene oxide (PEO)/silk fibroin (SF)/barium titanate (BaTiO₃) are introduced in this study. The SF solution was added to the PEO solution to form a PEO/SF blend with different weight percentages (5, 10, 15, 20 wt.%). The PEO/15 wt.% SF blend was selected to continue the experimental plan based on the optimum nanofiber morphology. Different wt.% of BaTiO₃ particles (0.2, 0.4, 0.8, 1 wt.%) were added to the PEO/15 wt.% SF blend solution, and the suspensions obtained were introduced to an electrospinning device. The fabricated tissue was characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy. The zeta potential of the solution and the piezoelectric performance of the fabricated tissue were characterized. A newly designed pizoTester was used to investigate piezoelectric properties. The results showed that a well-organized, smooth PEO/15 wt.% SF/0.2 wt.% BaTiO₃ nanofiber composite with low bead contents was obtained. Improved properties and electrical coupling were achieved in the newly introduced material. Electrospun PEO/15 wt.% SF/0.2 wt.% BaTiO₃ mats increased the output voltage (1150 mV) compared to pristine PEO and PEO/SF composite fibers (410 and 290 mV, respectively) upon applying 20 N force at 5 Hz frequency. The observed enhancement in piezoelectric properties suggests that the prepared composite could be a promising material in cardiac tissue engineering (CTE).

In situ polydopamine functionalized poly-L-lactic acid nanofibers with near-infrared-triggered antibacterial and reactive oxygen species scavenging capability

The development of a new multi-functional poly(L)-lactide (PLLA) nanofibrous scaffold with excellent antibacterial and reactive oxygen species (ROS) scavenging capability is quite important in tissue engineering. In this study, polydopamine (PDA)/PLLA nanofibers were prepared by combining electrospinning and post in-situ polymerization. The post in-situ polymerization of PDA on the PLLA nanofiber enable PDA uniformly distribute on PLLA nanofiber surface. PDA/PLLA nanofibrous composites also achieved stronger mechanical strength, hydrophilicity, good oxidation resistance and enhanced near-infrared photothermal effect. The near-infrared photothermal effect from PDA made the PDA/PLLA a good antibacterial material. The in vitro ROS scavenging ability of the PDA made PDA/PLLA be beneficial to damaged tissue repair. These results indicate that PDA/PLLA nanofibrous scaffold can be used as a tissue engineering scaffold material with versatile biomedical applications.

Biomaterials assisted reconstructive urology: The pursuit of an implantable bioengineered neo-urinary bladder

Urinary bladder is a dynamic organ performing complex physiological activities. Together with ureters and urethra, it forms the lower urinary tract that facilitates urine collection, low-pressure storage, and volitional voiding. However, pathological disorders are often liable to cause irreversible damage and compromise the normal functionality of the bladder, necessitating surgical intervention for a reconstructive procedure. Non-urinary autologous grafts, primarily derived from gastrointestinal tract, have long been the gold standard in clinics to augment or to replace the diseased bladder tissue. Unfortunately, such treatment strategy is commonly associated with several clinical complications. In absence of an optimal autologous therapy, a biomaterial based bioengineered platform is an attractive prospect revolutionizing the modern urology. Predictably, extensive investigative research has been carried out in pursuit of better urological biomaterials, that overcome the limitations of conventional gastrointestinal graft. Against the above backdrop, this review aims to provide a comprehensive and one-stop update on different biomaterial-based strategies that have been proposed and explored over the past 60 years to restore the dynamic function of the otherwise dysfunctional bladder tissue. Broadly, two unique perspectives of bladder tissue engineering and total alloplastic bladder replacement are critically discussed in terms of their status and progress. While the former is pivoted on scaffold mediated regenerative medicine; in contrast, the latter is directed towards the development of a biostable bladder prosthesis. Together, these routes share a common aspiration of designing and creating a functional equivalent of the bladder wall, albeit, using fundamentally different aspects of biocompatibility and clinical needs. Therefore, an attempt has been made to systematically analyze and summarize the evolution of various classes as well as generations of polymeric biomaterials in urology. Considerable emphasis has been laid on explaining the bioengineering methodologies, pre-clinical and clinical outcomes. Some of the unaddressed challenges, including vascularization, innervation, hollow 3D prototype fabrication and urinary encrustation, have been highlighted that currently delay the successful commercial translation. More importantly, the rapidly evolving and expanding concepts of bioelectronic medicine are discussed to inspire future research efforts towards the further advancement of the field. At the closure, crucial insights are provided to forge the biomaterial assisted reconstruction as a long-term therapeutic strategy in urological practice for patients' care.

Preparation and characterization of polyurethane/chitosan/CNT nanofibrous scaffold for cardiac tissue engineering

Myocardial infarction of cardiomyocytes is a leading cause of heart failure (HF) worldwide. Since heart has very limited regeneration capacity, cardiac tissue engineering (TE) to produce a bioactive scaffold is considered. In this study, a series of polyurethane solutions (5-7%wt) in aqueous acetic acid were prepared using electrospinning. A variety of Polyurethane (PU)/Chitosan (Cs)/carbon nanotubes (CNT) composite nanofibrous scaffolds with random and aligned orientation were fabricated to structurally mimic the extracellular matrix (ECM). Electrospun nanofibers were then characterized using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), water contact angle, degradation studies, tensile tests, electrical resistance measurement and cell viability assay. The biocompatibility of electrospun random and aligned nanofibrous scaffolds with H9C2 Cells was confirmed. The results revealed that fabricated PU/Cs/CNT composite nanofibrous scaffolds were electro-conductive and aligned nanofibers could be considered as promising scaffolds with nano-scale features for regeneration of infarcted myocardium.

Electrospinning: Application and Prospects for Urologic Tissue Engineering

Functional disorders and injuries of urinary bladder, urethra, and ureter may necessitate the application of urologic reconstructive surgeries to recover normal urine passage, prevent progressive damages of these organs and upstream structures, and improve the quality of life of patients. Reconstructive surgeries are generally very invasive procedures that utilize autologous tissues. In addition to imperfect functional outcomes, these procedures are associated with significant complications owing to long-term contact of urine with unspecific tissues, donor site morbidity, and lack of sufficient tissue for vast reconstructions. Thanks to the extensive advancements in tissue engineering strategies, reconstruction of the diseased urologic organs through tissue engineering have provided promising vistas during the last two decades. Several biomaterials and fabrication methods have been utilized for reconstruction of the urinary tract in animal models and human subjects; however, limited success has been reported, which inspires the application of new methods and biomaterials. Electrospinning is the primary method for the production of nanofibers from a broad array of natural and synthetic biomaterials. The biomimetic structure of electrospun scaffolds provides an ECM-like matrix that can modulate cells' function. In addition, electrospinning is a versatile technique for the incorporation of drugs, biomolecules, and living cells into the constructed scaffolds. This method can also be integrated with other fabrication procedures to achieve hybrid smart constructs with improved performance. Herein, we reviewed the application and outcomes of electrospun scaffolds in tissue engineering of bladder, urethra, and ureter. First, we presented the current status of tissue engineering in each organ, then reviewed electrospun scaffolds from the simplest to the most intricate designs, and summarized the outcomes of preclinical (animal) studies in this area.

Fabrication and Plasma Modification of Nanofibrous Tissue Engineering Scaffolds

This paper provides a comprehensive overview of nanofibrous structures for tissue engineering purposes and the role of non-thermal plasma technology (NTP) within this field. Special attention is first given to nanofiber fabrication strategies, including thermally-induced phase separation, molecular self-assembly, and electrospinning, highlighting their strengths, weaknesses, and potentials. The review then continues to discuss the biodegradable polyesters typically employed for nanofiber fabrication, while the primary focus lies on their applicability and limitations. From thereon, the reader is introduced to the concept of NTP and its application in plasma-assisted surface modification of nanofibrous scaffolds. The final part of the review discusses the available literature on NTP-modified nanofibers looking at the impact of plasma activation and polymerization treatments on nanofiber wettability, surface chemistry, cell adhesion/proliferation and protein grafting. As such, this review provides a complete introduction into NTP-modified nanofibers, while aiming to address the current unexplored potentials left within the field.

Regenerative medicine and drug delivery: Progress via electrospun biomaterials

Worldwide research on electrospinning enabled it as a versatile technique for producing nanofibers with specified physio-chemical characteristics suitable for diverse biomedical applications. In the case of tissue engineering and regenerative medicine, the nanofiber scaffolds' characteristics are custom designed based on the cells and tissues specific needs. This fabrication technique is also innovated for the production of nanofibers with special micro-structure and secondary structure characteristics such as porous fibers, hollow structure, and core- sheath structure. This review attempts to critically and succinctly capture the vast number of developments reported in the literature over the past two decades. We then discuss their applications as scaffolds for induction of cells growth and differentiation or as architecture for being used as graft for tissue engineering. The special nanofibers designed for improving regeneration of several tissues including heart, bone, central nerve system, spinal cord, skin and ocular tissue are introduced. We also discuss the potential of the electrospinning in drug delivery applications, which is a critical factor for cell culture, tissue formation and wound healing applications.

3D printed mesh reinforcements enhance the mechanical properties of electrospun scaffolds

Background

There is substantial interest in electrospun scaffolds as substrates for tissue regeneration and repair due to their fibrous, extracellular matrix-like composition with interconnected porosity, cost-effective production, and scalability. However, a common limitation of these scaffolds is their inherently low mechanical strength and stiffness, restricting their use in some clinical applications. In this study we developed a novel technique for 3D printing a mesh reinforcement on electrospun scaffolds to improve their mechanical properties.

Methods

A poly (lactic acid) (PLA) mesh was 3D-printed directly onto electrospun scaffolds composed of a 40:60 ratio of poly(ε-caprolactone) (PCL) to gelatin, respectively. PLA grids were printed onto the electrospun scaffolds with either a 6 mm or 8 mm distance between the struts. Scanning electron microscopy was utilized to determine if the 3D printing process affected the archtitecture of the electrospun scaffold. Tensile testing was used to ascertain mechanical properties (strength, modulus, failure stress, ductility) of both unmodified and reinforced electrospun scaffolds. An in vivo bone graft model was used to assess biocompatibility. Specifically, reinforced scaffolds were used as a membrane cover for bone graft particles implanted into rat calvarial defects, and implant sites were examined histologically.

Results

We determined that the tensile strength and elastic modulus were markedly increased, and ductility reduced, by the addition of the PLA meshes to the electrospun scaffolds. Furthermore, the scaffolds maintained their matrix-like structure after being reinforced with the 3D printed PLA. There was no indication at the graft/tissue interface that the reinforced electrospun scaffolds elicited an immune or foreign body response upon implantation into rat cranial defects.

Conclusion

3D-printed mesh reinforcements offer a new tool for enhancing the mechanical strength of electrospun scaffolds while preserving the advantageous extracellular matrix-like architecture. The modification of electrospun scaffolds with 3D-printed reinforcements is expected to expand the range of clinical applications for which electrospun materials may be suitable.

New approach to modification of poly (l-lactic acid) with nano-hydroxyapatite improving functionality of human adipose-derived stromal cells (hASCs) through increased viability and enhanced mitochondrial activity

The aim of this study was to determine the cytocompatibility of poly (l-lactide) (PLLA) scaffolds fabricated using co-rotating twin screw extrusion technique and functionalized with different concentrations of nano-hydroxyapatite (nHAp). The efforts were aimed on the designing bioactive scaffolds improving the viability and metabolic activity of human adipose-derived multipotent stromal cells (hASCs). The in vitro study was designed to determine the optimal nHAp concentration, based on analysis of hASCs morphology, adhesion rate, as well as metabolic and proliferative potential. Initially, the PLLA filled with three different concentrations of the nHAp were tested i.e. 5%, 10% and 15 wt%. The obtained results indicated that the 10 wt% nHAp in the PLLA (10% nHAp/PLLA) matrices improved the adhesion and proliferation of the hASCs, what was in good agreement with the results of tensile properties of the composites. Further, we performed profound studies regarding the cytotoxicity of 10% nHAp/PLLA. The analysis included the evaluation of the biomaterial influence on viability, apoptosis-related markers expression profile and mitochondrial function. The cytocompatibility of 10% nHAp/PLLA scaffolds toward the hASCs was confirmed. The hASCs propagated on 10% nHAp/PLLA were more viable then those propagated on the plain PLLA. The level of pro-apoptotic markers, i.e. caspase-3 and Bax in cultures on 10% nHAp/PLLA was significantly decreased. Obtained results correlated with higher mitochondrial membrane potential of hASCs in those cultures. The obtained composites may improve therapeutic potential of hASCs via directing their adhesion, enhancing proliferation and viability as well as increasing mitochondrial potential, thus may find potential application in tissue engineering.

Novel electro-conductive nanocomposites based on electrospun PLGA/CNT for biomedical applications

Electro-conductive nanocomposites have several applications in biomedical field. Development of a biocompatible electro-conductive polymeric materials is therefore of prime importance. In this study, electro-conductive nanofibrous mats of PLGA/CNT were fabricated through different methods including blend electrospinning, simultaneous PLGA electrospinning and CNT electrospraying and ultrasound-induced adsorption of CNTs on the electrospun PLGA nanofibers. The morphology and diameter of fibers were characterized by SEM and TEM, showing the lowest average diameters of 477 ± 136 nm for PLGA/MWCNT blend nanocomposites. MWCNT-sprayed PLGA specimens showed significant lower water contact angle (83°), electrical resistance (3.0 × 10⁴ Ω) and higher mechanical properties (UTS: 5.50 ± 0.46 MPa) compared to the untreated PLGA scaffolds. Also, results of PC12 cell study demonstrated highest viability percentage on the MWCNT-sprayed PLGA nanofibers. We propose that the conductive nanocomposites have capability to use as tool for the neural regeneration and biosensors.

The effects of cross-linked/uncross-linked electrospun fibrinogen/polycaprolactone nanofibers on the proliferation of normal human epidermal keratinocytes

The aim of this study was an investigation on the proliferation rate of normal human epidermal keratinocytes (NHEK) on the cross-linked and uncross-linked fibrinogen/polycaprolactone (Fbg/PCL) nanofibers to determine a suitable scaffold for skin tissue engineering. Nanofibrous scaffolds were prepared by electrospinning of different weight ratios of Fbg to PCL and were analyzed as morphology, surface chemical properties and cytocompatibility by scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, respectively. The diameters of the blended uncross-linked scaffolds were in the range of 124±43 nm–209±155 nm. Cross-linking of scaffolds with glutaraldehyde did not make a significant change in the diameter of blended scaffolds in 16 h. Cross-linking also improved the tensile strength and weight loss rate of scaffolds. However, cross-linking demonstrated an unfavorable effect on the attachment and proliferation of NHEK cells. The proliferation study revealed that uncross-linked scaffolds containing 50% and 70% Fbg provide a better environment for the growth of NHEK cells, and can be considered promising scaffolds in tissue engineering applications.

Nanofibers as Bioinstructive Scaffolds Capable of Modulating Differentiation through Mechanosensitive Pathways for Regenerative Engineering

Bioinstructive scaffolds encode information in the physical shape and size of materials to direct cell responses. Electrospinning nanofibers is a process that offers control over scaffold architecture and fiber diameter, while providing extended linear length of fibers. This review summarizes tissue engineering literature that has utilized nanofiber scaffolds to direct stem cell differentiation for various tissues including musculoskeletal, vascular, immunological and nervous system tissues. Nanofibers are also considered for their extracellular matrix mimetic characteristics that can preserve stem cell differentiation capacity. These topics are considered in the context of focal adhesion and integrin signaling. Regenerative engineering will be enhanced by construction of scaffolds encoded with shape information to cause an attached cell to create the intended tissue at that region. Nanofibers are likely to be a bioinstructive scaffold in future regenerative engineering development as we pursue the Grand Challenges of engineering tissues.

Preparation of collagen/polyurethane/knitted silk as a composite scaffold for tendon tissue engineering

The main objective of this study was to prepare a hybrid three-dimensional scaffold that mimics natural tendon tissues. It has been found that a knitted silk shows good mechanical strength; however, cell growth on the bare silk is not desirable. Hence, electrospun collagen/polyurethane combination was used to cover knitted silk. A series of collagen and polyurethane solutions (4%-7% w/v) in aqueous acetic acid were prepared and electrospun. According to obtained scanning electron microscopy images from pure collagen and polyurethane nanofibers, concentration was set constant at 5% (w/v) for blend solutions of collagen/polyurethane. Afterward, blend solutions with the weight ratios of 75/25, 50/50 and 25/75 were electrospun. Scanning electron microscopy images demonstrated the smooth and uniform morphology for the optimized nanofibers. The least fibers diameter among three weight ratios was found for collagen/polyurethane (25/75) which was 100.86 ± 40 nm and therefore was selected to be electrospun on the knitted silk. Attenuated total reflectance-Fourier transform infrared spectra confirmed the chemical composition of obtained electrospun nanofibers on the knitted silk. Tensile test of the specimens including blend nanofiber, knitted silk and commercial tendon substitute examined and indicated that collagen/polyurethane-coated knitted silk has appropriate mechanical properties as a scaffold for tendon tissue engineering. Then, Alamar Blue assay of the L929 fibroblast cell line seeded on the prepared scaffolds demonstrated appropriate viability of the cells with a significant proliferation on the scaffold containing more collagen content. The results illustrate that the designed structure would be promising for being used as a temporary substitute for tendon repair.

The Current Use of Stem Cells in Bladder Tissue Regeneration and Bioengineering

Many pathological processes including neurogenic bladder and malignancy necessitate bladder reconstruction, which is currently performed using intestinal tissue. The use of intestinal tissue, however, subjects patients to metabolic abnormalities, bladder stones, and other long-term sequelae, raising the need for a source of safe and reliable bladder tissue. Advancements in stem cell biology have catapulted stem cells to the center of many current tissue regeneration and bioengineering strategies. This review presents the recent advancements in the use of stem cells in bladder tissue bioengineering.