Biofunctional Nanofibrous Substrate Comprising Immobilized Antibodies and Selective Binding of Autologous Growth Factors

Functional recovery of injured cavernous nerves achieved through endogenous nerve growth factor-containing bioactive fibrous membrane

Radical prostatectomy is a highly successful treatment for prostate cancer, among the most prevalent manifestations of the illness. Damage of the cavernous nerve (CN) during prostatectomy is the main cause of postoperative erectile dysfunction (ED). In this study, the capability of a personalized bioactive fibrous membrane to regenerate injured CN was investigated. The fibrous membrane bioactivity is conferred by the selectively bound nerve growth factor (NGF) present in the rat urine. In a rat model of bilateral CN crush, the implanted bioactive fibrous membrane induces CN regeneration and restoration of erectile function, showing a significantly increased number of smooth muscle cells and content of endothelial and neuronal nitric oxide synthases (eNOS; nNOS). In addition, the bioactive fibrous membrane promotes nerve regeneration by increasing the number of myelinated axons and nNOS-positive cells, therefore reversing the CN fibrosis found in untreated rats or rats treated with a bare fibrous membrane. Therefore, this personalized regenerative strategy could overcome the recognized drawbacks of currently available treatments for CN injuries. It may constitute an effective treatment for prostate cancer patients suffering from ED after being subject to radical prostatectomy. STATEMENT OF SIGNIFICANCE: The present work introduces a unique strategy to address post-surgical ED resulting from CN injury during pelvic surgery (e.g., radical prostatectomy, radical cystoprostatectomy, abdominoperineal resection). It comprises a bioactive and cell-free fibrous implant, customized to enhance CN recovery. Pre-clinical results in a rat model of bilateral CN crush demonstrated that the bioactive fibrous implant can effectively heal injured CN, and restore penile structure and function. This implant selectively binds NGF from patient fluids (i.e. urine) due to its functionalized surface and high surface area. Moreover, its local implantation reduces adverse side effects. This tailored regenerative approach has the potential to revolutionize the treatment of ED in prostate cancer patients following radical prostatectomy, overcoming current treatment limitations.

Stimulation of Neurite Outgrowth Using Autologous NGF Bound at the Surface of a Fibrous Substrate

Peripheral nerve injury still remains a major clinical challenge, since the available solutions lead to dysfunctional nerve regeneration. Even though autologous nerve grafts are the gold standard, tissue engineered nerve guidance grafts are valid alternatives. Nerve growth factor (NGF) is the most potent neurotrophic factor. The development of a nerve guidance graft able to locally potentiate the interaction between injured neurons and autologous NGF would be a safer and more effective alternative to grafts that just release NGF. Herein, a biofunctional electrospun fibrous mesh (eFM) was developed through the selective retrieval of NGF from rat blood plasma. The neurite outgrowth induced by the eFM-NGF systems was assessed by culturing rat pheochromocytoma (PC12) cells for 7 days, without medium supplementation. The biological results showed that this NGF delivery system stimulates neuronal differentiation, enhancing the neurite growth more than the control condition.

Chondrogenic differentiation induced by extracellular vesicles bound to a nanofibrous substrate

Extracellular vesicles (EVs) are being increasingly studied owing to its regenerative potential, namely EVs derived from human bone marrow mesenchymal stem cells (hBM-MSCs). Those can be used for controlling inflammation, repairing injury, and enhancing tissue regeneration. Differently, the potential of EVs derived from human articular chondrocytes (hACs) to promote cartilage regeneration has not been thoroughly investigated. This work aims to develop an EVs immobilization system capable of selectively bind EVs present in conditioned medium obtained from cultures of hACs or hBM-MSC. For that, an anti-CD63 antibody was immobilized at the surface of an activated and functionalized electrospun nanofibrous mesh. The chondrogenic potential of bound EVs was further assessed by culturing hBM-MSCs during 28 days under basal conditions. EVs derived from hACs cultured under differentiation medium or from chondrogenically committed hBM-MSCs induced a chondrogenic phenotype characterized by marked induction of SOX9, COMP, Aggrecan and Collagen type II, and matrix glycosaminoglycans synthesis. Indeed, both EVs immobilization systems outperformed the currently used chondroinductive strategies. These data show that naturally secreted EVs can guide the chondrogenic commitment of hBM-MSCs in the absence of any other chemical or genetic chondrogenic inductors based in medium supplementation.

Recapitulation of Thymic Function by Tissue Engineering Strategies

The thymus is responsible for the development and selection of T lymphocytes, which in turn also participate in the maturation of thymic epithelial cells. These events occur through the close interactions between hematopoietic stem cells and developing thymocytes with the thymic stromal cells within an intricate 3D network. The complex thymic microenvironment and function, and the current therapies to induce thymic regeneration or to overcome the lack of a functional thymus are herein reviewed. The recapitulation of the thymic function using tissue engineering strategies has been explored as a way to control the body's tolerance to external grafts and to generate ex vivo T cells for transplantation. In this review, the main advances in the thymus tissue engineering field are disclosed, including both scaffold- and cell-based strategies. In light of the current gaps and limitations of the developed systems, the design of novel biomaterials for this purpose with unique features is also discussed.

The Effect of the Controlled Release of Platelet Lysate from PVA Nanomats on Keratinocytes, Endothelial Cells and Fibroblasts

Platelet lysate (PL) provides a natural source of growth factors and other bioactive molecules, and the local controlled release of these bioactive PL components is capable of improving the healing of chronic wounds. Therefore, we prepared composite nanofibrous meshes via the needleless electrospinning technique using poly(vinyl alcohol) (PVA) with a high molecular weight and with a high degree of hydrolysis with the incorporated PL (10% w/w). The morphology, wettability and protein release from the nanofibers was then assessed from the resulting composite PVA–PL nanomats. The bioactivity of the PVA–PL nanomats was proved in vitro using HaCaT keratinocytes, human saphenous endothelial cells (HSVECs) and 3T3 fibroblasts. The PVA–PL supported cell adhesion, proliferation, and viability. The improved phenotypic maturation of the HaCaT cells due to the PVA–PL was manifested via the formation of intermediate filaments positive for cytokeratin 10. The PVA–PL enhanced both the synthesis of the von Willebrand factor via HSVECs and HSVECs chemotaxis through membranes with 8 µm-sized pores. These results indicated the favorable effects of the PVA–PL nanomats on the three cell types involved in the wound healing process, and established PVA–PL nanomats as a promising candidate for further evaluation with respect to in vivo experiments.

Fibronectin-Functionalized Fibrous Meshes as a Substrate to Support Cultures of Thymic Epithelial Cells

Thymic epithelial cells (TECs) are the main regulators of T lymphocyte development and selection, requiring a three-dimensional (3D) environment to properly perform these biological functions. The aim of this work was to develop a 3D culture substrate that allows the survival and proliferation of TECs. Thus, electrospun fibrous meshes (eFMs) were functionalized with fibronectin, one of the major extracellular matrix (ECM) proteins of the thymus. For that, highly porous eFMs were activated using oxygen plasma treatment followed by amine insertion, which allows the immobilization of fibronectin through EDC/NHS chemistry. The medullary TECs presented increased proliferation, viability, and protein synthesis when cultured on fibronectin-functionalized eFMs (FN-eFMs). These cells showed a spread morphology, with increased migration toward the inner layers of FN-eFMs and the production of thymic ECM proteins, such as collagen type IV and laminin. These results suggest that FN-eFMs are an effective substrate for supporting thymic cell cultures.

The Body's Cellular and Molecular Response to Protein-Coated Medical Device Implants: A Review Focused on Fibronectin and BMP Proteins

Recent years have seen a marked rise in implantation into the body of a great variety of devices: hip, knee, and shoulder replacements, pacemakers, meshes, glucose sensors, and many others. Cochlear and retinal implants are being developed to restore hearing and sight. After surgery to implant a device, adjacent cells interact with the implant and release molecular signals that result in attraction, infiltration of the tissue, and attachment to the implant of various cell types including monocytes, macrophages, and platelets. These cells release additional signaling molecules (chemokines and cytokines) that recruit tissue repair cells to the device site. Some implants fail and require additional revision surgery that is traumatic for the patient and expensive for the payer. This review examines the literature for evidence to support the possibility that fibronectins and BMPs could be coated on the implants as part of the manufacturing process so that the proteins could be released into the tissue surrounding the implant and improve the rate of successful implantation.

Tubular Fibrous Scaffolds Functionalized with Tropoelastin as a Small-Diameter Vascular Graft

Cardiovascular disorders are a healthcare problem in today's society. The clinically available synthetic vascular grafts are thrombogenic and could induce intimal hyperplasia. Rapid endothelialization and matched mechanical properties are two major requirements to be considered when designing functional vascular grafts. Herein, an electrospun tubular fibrous (eTF) scaffold was biofunctionalized with tropoelastin at the luminal surface. The luminal surface functionalization was confirmed by an increase of the zeta potential and by the insertion of NH₂ groups. Tropoelastin was immobilized via its -NH₂ or -COOH groups at the activated or aminolysed eTF scaffolds, respectively, to study the effect of exposed functional groups on human endothelial cells (ECs) behavior. Tensile properties demonstrated that functionalized eTF scaffolds presented strength and stiffness within the range of those of native blood vessels. Tropoelastin immobilized on activated eTF scaffolds promoted higher metabolic activity and proliferation of ECs, whereas when immobilized on aminolysed eTF scaffolds, significantly higher protein synthesis was observed. These biofunctional eTF scaffolds are a promising small-diameter vascular graft that promote rapid endothelialization and have compatible mechanical properties.

Enhanced performance of chitosan/keratin membranes with potential application in peripheral nerve repair

Although surgical management of peripheral nerve injuries (PNIs) has improved over time, autografts are still the current "gold standard" treatment for PNIs, which presents numerous limitations. In an attempt to improve natural biomaterial-based nerve guidance conduits (NGCs), chitosan (CHT), a derivative of the naturally occurring biopolymer chitin, has been explored for peripheral nerve regeneration (PNR). In addition to CHT, keratin has gained enormous attention as a biomaterial and tissue engineering scaffolding. In this study, biomimetic CHT/keratin membranes were produced using a solvent casting technique. These membranes were broadly characterized in terms of their surface topography and physicochemical properties, with techniques such as Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), contact angle, weight loss and water uptake measurements, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Biological in vitro assays were also performed, where a preliminary cytotoxicity screening with the L929 fibroblast cell line revealed that the membranes and respective materials are suitable for cell culture. In addition, Schwann cells, fibroblasts and endothelial cells were directly seeded in the membranes. Quantitative and qualitative assays revealed that the addition of keratin enhanced cell viablity and adhesion. Based on the encouraging in vitro results, the in vivo angiogenic/antiangiogenic potential of CHT and CHT/keratin membranes was assessed, using an optimized chick embryo chorioallantoic membrane assay, where higher angiogenic responses were seen in keratin-enriched materials. Overall, the obtained results indicate the higher potential of CHT/keratin membranes for guided tissue regeneration applications in the field of PNR.

Spatial immobilization of endogenous growth factors to control vascularization in bone tissue engineering

An engineered biofunctional system comprises endogenous BMP-2 and VEGF bound in a parallel pattern. It successfully enabled obtaining the spatial osteogenic and angiogenic differentiation of human hBM-MSCs under basal culture conditions.

A glance on the role of fibronectin in controlling cell response at biomaterial interface

The bioactivity of biomaterials is closely related to cell response in contact with them. However, shortly after their insertion, materials are soon covered with proteins that constitute the biological fluids, and which render the direct surface recognition by cells almost impossible. The control of protein adsorption at the interface is therefore desirable. Extracellular matrix proteins are of particular interest in this sense, due to their well-known ability to modulate cell behavior. Particularly, fibronectin plays a leading role, being present in both healthy and injured tissues undergoing healing and regeneration. The aim of the present work is to give an overview on fibronectin and on its involvement in the control of cell behavior providing evidence of its pivotal role in the control of cell adhesion, spreading, migration, proliferation and differentiation. A deep insight into methods to enrich biomaterials surface with fibronectin will be then discussed, as well as new cues on the possibility to design tailored platforms able to specifically retain fibronectin from the surrounding extracellular milieu.

Is selective protein adsorption on biomaterials a viable option to promote periodontal regeneration?

Periodontitis is an inflammatory condition that can induce significant destruction of the periodontium, the set of specialized tissues that provide nourishment and support to the teeth. According to the guided tissue regeneration principles, the periodontium can be regenerated if the spatiotemporal control of wound healing is obtained, namely the tune control of cell response. After material implantation, protein adsorption at the interface is the first occurring biological event, which influences subsequent cell response. With the regard of this, we hypothesize that the control of selective adsorption of biological cues from the surrounding milieu may be a key-point to control selective cell colonization of scaffolds for periodontal tissue regeneration.

Biofunctional Nanofibrous Substrate for Local TNF-Capturing as a Strategy to Control Inflammation in Arthritic Joints

Rheumatoid arthritis (RA) is an autoimmune disease that affects the synovial cavity of joints, and its pathogenesis is associated with an increased expression of pro-inflammatory cytokines, namely tumour necrosis factor-alpha (TNF-α). It has been clinically shown to have an adequate response to systemic administration of TNF-α inhibitors, although with many shortcomings. To overcome such limitations, the immobilization of a TNF-α antibody on a nanofibrous substrate to promote a localized action is herein proposed. By using this approach, the antibody has its maximum therapeutic efficacy and a prolonged therapeutic benefit, avoiding the systemic side-effects associated with conventional biological agents' therapies. To technically achieve such a purpose, the surface of electrospun nanofibers is initially activated and functionalized, allowing TNF-α antibody immobilization at a maximum concentration of 6 µg/mL. Experimental results evidence that the biofunctionalized nanofibrous substrate is effective in achieving a sustained capture of soluble TNF-α over time. Moreover, cell biology assays demonstrate that this system has no deleterious effect over human articular chondrocytes metabolism and activity. Therefore, the developed TNF-capturing system may represent a potential therapeutic approach for the local management of severely affected joints.

Calcium sequestration by fungal melanin inhibits calcium-calmodulin signalling to prevent LC3-associated phagocytosis

LC3-associated phagocytosis (LAP) is a non-canonical autophagy pathway regulated by Rubicon, with an emerging role in immune homeostasis and antifungal host defence. Aspergillus cell wall melanin protects conidia (spores) from killing by phagocytes and promotes pathogenicity through blocking nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-dependent activation of LAP. However, the signalling regulating LAP upstream of Rubicon and the mechanism of melanin-induced inhibition of this pathway remain incompletely understood. Herein, we identify a Ca²⁺ signalling pathway that depends on intracellular Ca²⁺ sources from endoplasmic reticulum, endoplasmic reticulum-phagosome communication, Ca²⁺ release from phagosome lumen and calmodulin (CaM) recruitment, as a master regulator of Rubicon, the phagocyte NADPH oxidase NOX2 and other molecular components of LAP. Furthermore, we provide genetic evidence for the physiological importance of Ca²⁺-CaM signalling in aspergillosis. Finally, we demonstrate that Ca²⁺ sequestration by Aspergillus melanin inside the phagosome abrogates activation of Ca²⁺-CaM signalling to inhibit LAP. These findings reveal the important role of Ca²⁺-CaM signalling in antifungal immunity and identify an immunological function of Ca²⁺ binding by melanin pigments with broad physiological implications beyond fungal disease pathogenesis.

Interleukin-6 Neutralization by Antibodies Immobilized at the Surface of Polymeric Nanoparticles as a Therapeutic Strategy for Arthritic Diseases

Arthritic diseases are disabling conditions affecting millions of patients worldwide. Pro-inflammatory cytokines, particularly interleukin-6 (IL-6), plays a crucial role in inflammation and cartilage destruction. Although the beneficial effects of antibody therapy, its efficacy is limited. Therefore, this work proposes the immobilization of antibodies at the surface of biodegradable polymeric nanoparticles (NPs) to capture and neutralize IL-6. Our system is intended to protect, extend and enhance the therapeutic efficacy after delivery. Chitosan-hyaluronic acid NPs are synthesized as a stable monodisperse population. After determining the maximum immobilization capacity (10 μg/mL), the capture ability was confirmed. Biological assays demonstrate the NPs cytocompatibility with human articular chondrocytes (hACs) and human macrophages. hACs stimulated with macrophage conditioned medium shows the beneficial role of IL-6 capture and neutralization. Biofunctionalized NPs exhibit a prolonged action and stronger efficacy than the free antibody. In conclusion, this system can be an effective and long lasting treatment for arthritic diseases.

Blood derivatives awaken in regenerative medicine strategies to modulate wound healing

Blood components play key roles in the modulation of the wound healing process and, together with the provisional fibrin matrix ability to selectively bind bioactive molecules and control its spatial-temporal presentation, define the complex microenvironment that characterize this biological process. As a biomimetic approach, the use of blood derivatives in regenerative strategies has awakened as a source of multiple therapeutic biomolecules. Nevertheless, and despite their clinical relevance, blood derivatives have been showing inconsistent therapeutic results due to several factors, including proper control over their delivery mechanisms. Herein, we highlight recent trends on the use biomaterials to protect, sequester and deliver these pools of biomolecules in tissue engineering and regenerative medicine approaches. Particular emphasis is given to strategies that enable to control their spatiotemporal delivery and improve the selectivity of presentation profiles of the biomolecules derived from blood derivatives rich in platelets. Finally, we discussed possible directions for biomaterials design to potentiate the aimed regenerative effects of blood derivatives and achieve efficient therapies.

The functionalization of natural polymer-coated gold nanoparticles to carry bFGF to promote tissue regeneration

A schematic of the preparation of natural polymer-coated AuNPs for monitoring tissue regeneration stimulated by bFGF.

The Use of Electrospinning Technique on Osteochondral Tissue Engineering

Electrospinning, an electrostatic fiber fabrication technique, has attracted significant interest in recent years due to its versatility and ability to produce highly tunable nanofibrous meshes. These nanofibrous meshes have been investigated as promising tissue engineering scaffolds since they mimic the scale and morphology of the native extracellular matrix. The sub-micron diameter of fibers produced by this process presents various advantages like the high surface area to volume ratio, tunable porosity, and the ability to manipulate the nanofiber composition in order to get desired properties and functionality. Electrospun fibers can be oriented or arranged randomly, giving control over both mechanical properties and the biological response to the fibrous scaffold. Moreover, bioactive molecules can be integrated with the electrospun nanofibrous scaffolds in order to improve the cellular response. This chapter presents an overview of the developments on electrospun polymer nanofibers including processing, structure, and their applications in the field of osteochondral tissue engineering.

Development of VEGF-loaded PLGA matrices in association with mesenchymal stem cells for tissue engineering

The association of bioactive molecules, such as vascular endothelial growth factor (VEGF), with nanofibers facilitates their controlled release, which could contribute to cellular migration and differentiation in tissue regeneration. In this research, the influence of their incorporation on a polylactic-co-glycolic acid (PLGA) scaffold produced by electrospinning on cell adhesion and viability and cytotoxicity was carried out in three groups: 1) PLGA/BSA/VEGF; 2) PLGA/BSA, and 3) PLGA. Morphology, fiber diameter, contact angle, loading efficiency and controlled release of VEGF of the biomaterials, among others, were measured. The nanofibers showed smooth surfaces without beads and with interconnected pores. PLGA/BSA/VEGF showed the smallest water contact angle and VEGF released for up to 160 h. An improvement in cell adhesion was observed for the PLGA/BSA/VEGF scaffolds compared to the other groups and the scaffolds were non-toxic for the cells. Therefore, the scaffolds were shown to be a good strategy for sustained delivery of VEGF and may be a useful tool for tissue engineering.