Biomimetic electrospun PVDF/self-assembling peptide piezoelectric scaffolds for neural stem cell transplantation in neural tissue engineering.

Piezoelectric materials can provide in situ electrical stimulation without external chemical or physical support, opening new frontiers for future bioelectric therapies. Polyvinylidene fluoride (PVDF) possesses piezoelectricity and biocompatibility, making it an electroactive biomaterial capable of enhancing bioactivity through instantaneous electrical stimulation, which indicates significant potential in tissue engineering. In this study, we developed electroactive and biomimetic scaffolds made of electrospun PVDF and self-assembling peptides (SAPs) to enhance stem cell transplantation for spinal cord injury regeneration. We investigated the morphology and crystalline polymorphs of the electrospun scaffolds. Morphological studies demonstrated the benefit of using mixed sodium dodecyl sulfate (SDS) and SAPs as additives to form thinner, uniform, and defect-free fibers. Regarding electroactive phases, ß and γ phases-evidence of electroactivity-were predominant in aligned scaffolds and scaffolds modified with SDS and SAPs. In vitro studies showed that neural stem cells (NSCs) seeded on electrospun PVDF with additives exhibited desirable proliferation and differentiation compared to the gold standard. Furthermore, the orientation of the fibers influenced scaffold topography, resulting in a higher degree of cell orientation in fiber-aligned scaffolds compared to randomly oriented ones.

In Situ Transglutaminase Cross-Linking Improves Mechanical Properties of Self-Assembling Peptides for Biomedical Applications.

The development of three-dimensional (3D) biomaterials that mimic natural tissues is required for efficiently restoring physiological functions of injured tissues and organs. In the field of soft hydrogels, self-assembled peptides (SAPs) stand out as distinctive biomimetic scaffolds, offering tunable properties. They have garnered significant attention in nanomedicine due to their innate ability to self-assemble, resulting in the creation of fibrous nanostructures that closely mimic the microenvironment of the extracellular matrix (ECM). This unique feature ensures their biocompatibility and bioactivity, making them a compelling area of study over the past few decades. As they are soft hydrogels, approaches are necessary to enhance the stiffness and resilience of the SAP materials. This work shows an enzymatic strategy to selectively increase the stiffness and resiliency of functionalized SAPs using transglutaminase (TGase) type 2, an enzyme capable of triggering the formation of isopeptide bonds. To this aim, we synthesized a set of SAP sequences and characterized their cross-linking via rheological experiments, atomic force microscopy (AFM), thioflavin-T binding assay, and infrared spectroscopy (ATR-FTIR) tests. The results showed an improvement of the storage modulus of cross-linked SAPs at no cost of the maximum stress-at-failure. Further, in in vitro tests, we examined and validated the TGase capability to cross-link SAPs without hampering seeded neural stem cells (hNSCs) viability and differentiation, potentially leaving the door open for safe in situ cross-linking reactions in vivo.

Multiparametric in vitro and in vivo analysis of the safety profile of self-assembling peptides.

Self-assembling peptides (SAPs) have gained significant attention in biomedicine because of their unique properties and ability to undergo molecular self-assembly driven by non-covalent interactions. By manipulating their composition and structure, SAPs can form well-ordered nanostructures with enhanced selectivity, stability and biocompatibility. SAPs offer advantages such as high chemical and biological diversity and the potential for functionalization. However, studies concerning its potentially toxic effects are very scarce, a limitation that compromises its potential translation to humans. This study investigates the potentially toxic effects of six different SAP formulations composed of natural amino acids designed for nervous tissue engineering and amenable to ready cross-linking boosting their biomechanical properties. All methods were performed in accordance with the relevant guidelines and regulations. A wound-healing assay was performed to evaluate how SAPs modify cell migration. The results in vitro demonstrated that SAPs did not induce genotoxicity neither skin sensitization. In vivo, SAPs were well-tolerated without any signs of acute systemic toxicity. Interestingly, SAPs were found to promote the migration of endothelial, macrophage, fibroblast, and neuronal-like cells in vitro, supporting a high potential for tissue regeneration. These findings contribute to the development and translation of SAP-based biomaterials for biomedical applications.

Recent Advances in the Development of Biomimetic Materials.

In this review, we focused on recent efforts in the design and development of materials with biomimetic properties. Innovative methods promise to emulate cell microenvironments and tissue functions, but many aspects regarding cellular communication, motility, and responsiveness remain to be explained. We photographed the state-of-the-art advancements in biomimetics, and discussed the complexity of a "bottom-up" artificial construction of living systems, with particular highlights on hydrogels, collagen-based composites, surface modifications, and three-dimensional (3D) bioprinting applications. Fast-paced 3D printing and artificial intelligence, nevertheless, collide with reality: How difficult can it be to build reproducible biomimetic materials at a real scale in line with the complexity of living systems? Nowadays, science is in urgent need of bioengineering technologies for the practical use of bioinspired and biomimetics for medicine and clinics.

Biomimetic Electrospun Self-Assembling Peptide Scaffolds for Neural Stem Cell Transplantation in Neural Tissue Engineering.

Spinal cord regeneration using stem cell transplantation is a promising strategy for regenerative therapy. Stem cells transplanted onto scaffolds that can mimic natural extracellular matrix (ECM) have the potential to significantly improve outcomes. In this study, we strived to develop a cell carrier by culturing neural stem cells (NSCs) onto electrospun 2D and 3D constructs made up of specific crosslinked functionalized self-assembling peptides (SAPs) featuring enhanced biomimetic and biomechanical properties. Morphology, architecture, and secondary structures of electrospun scaffolds in the solid-state and electrospinning solution were studied step by step. Morphological studies showed the benefit of mixed peptides and surfactants as additives to form thinner, uniform, and defect-free fibers. It has been observed that ß-sheet conformation as evidence of self-assembling has been predominant throughout the process except for the electrospinning solution. In vitro NSCs seeded on electrospun SAP scaffolds in 2D and 3D conditions displayed desirable proliferation, viability, and differentiation in comparison to the gold standard. In vivo biocompatibility assay confirmed the permissibility of implanted fibrous channels by foreign body reaction. The results of this study demonstrated that fibrous 2D/3D electrospun SAP scaffolds, when shaped as micro-channels, can be suitable to support NSC transplantation for regeneration following spinal cord injury.

Star poly(ε-caprolactone)-based electrospun fibers as biocompatible scaffold for doxorubicin with prolonged drug release activity.

In this work, a novel drug delivery system consisting of poly(ε-caprolactone) (PCL) electrospun fibers containing an ad-hoc-synthesized star polymer made up of a poly(amido-amine) (PAMAM) core and PCL branches (PAMAM-PCL) was developed. The latter system which was synthesized via the ring opening polymerization of ε-caprolactone, starting from a hydroxyl-terminated PAMAM dendrimer and characterized by means of 1H NMR, IR and DSC, was found to be compatible with both the polymer matrix and a hydrophilic chemotherapeutic drug, doxorubicin (DOXO), the model drug used in this work. The preparation of the dendritic PCL star product with an average arm length of 2000g/mol was characterized using IR and 1H NMR measurements. The prepared star polymer possessed a higher crystallinity and a lower melting temperature than that of the used linear PCL. Electrospun fibers were prepared starting from solutions containing the neat PCL as well as the PCL/PAMAM-PCL mixture. Electrospinning conditions were optimized in order to obtain defect free fibers, which was proven by the structural FE-SEM study. PAMAM moieties enhanced the hydrophilicity of the fibers, as proved by comparing the water absorption for the PCL/PAMAM-PCL fibers to that neat PCL fibers. The drug-loaded system PCL/PAMAM-PCL was prepared by directly introducing DOXO into the electrospinning solutions. The DOXO-loaded PCL/PAMAM-PCL showed a prolonged release of the drug with respect to the DOXO-loaded PCL fibers and elicited effective controlled toxicity over A431 epidermoid carcinoma, HeLa cervical cancer cells and drug resistant MCF-7 breast cancer cells. On the contrary, the drug-free PCL/PAMAM-PCL scaffold demonstrated no toxic effects on human dermal fibroblasts, suggesting the biocompatibility of the proposed system which can be used in cellular scaffold applications.