Browsing by Subject "Peptide nanofibers"

Now showing 1 - 12 of 12

Open Access
Affinity of glycopeptide nanofibers to growth factors and their effects on cells
(2017-09) Haştar, Nurcan
The development of scaffolds for growth factor delivery is a promising approach for tissue regeneration applications due to their crucial roles during regeneration. Growth factor secretion and interactions with glycosaminoglycans are essential steps for the regulation of cellular behavior. Therefore, glycosaminoglycan-mimetic scaffolds provide a great opportunity to modulate the effects of growth factor actions on cell fate. In this thesis, sugar-bearing peptide amphiphile molecules were characterized and tested for VEGF, FGF-2 and NGF affinity. ELISA-based affinity analyses revealed that glycopeptide nanofibers had high affinity to NGF; however, glycopeptides alone were not enough to interact efficiently with VEGF and FGF-2. Since VEGF and NGF contain heparin-binding domains, the addition of a sulfonated peptide amphiphile increased the affinity of the nanofiber network to these growth factors. Glycopeptide-sulfonate nanofibers were also found to promote in vitro tube formation through their VEGF and FGF-2 affinity. VEGF release profiles of HUVECs indicated that increasing concentration of VEGF may provide autocrine signaling and enhance tube formation without any exogenous pro-angiogenic factor addition. In addition, when NGF-responsive PC-12 cells were cultured on glycopeptide nanofibers, they extended their neurites to an extent comparable with a widely-used positive control molecule (poly-L-lysine). These results suggest that glycosaminoglycan-mimetic glycopeptide nanofiber networks can be used as efficient growth factor presentation platforms for tissue regeneration applications to induce angiogenesis or peripheral nerve regeneration.
Open Access
Angiogenic peptide nanofibers repair cardiac tissue defect after myocardial infarction
(Acta Materialia Inc, 2017) Rufaihah, A. J.; Yasa, I. C.; Ramanujam, V. S.; Arularasu, S. C.; Kofidis, T.; Güler, Mustafa O.; Tekinay, A. B.
Myocardial infarction remains one of the top leading causes of death in the world and the damage sustained in the heart eventually develops into heart failure. Limited conventional treatment options due to the inability of the myocardium to regenerate after injury and shortage of organ donors require the development of alternative therapies to repair the damaged myocardium. Current efforts in repairing damage after myocardial infarction concentrates on using biologically derived molecules such as growth factors or stem cells, which carry risks of serious side effects including the formation of teratomas. Here, we demonstrate that synthetic glycosaminoglycan (GAG) mimetic peptide nanofiber scaffolds induce neovascularization in cardiovascular tissue after myocardial infarction, without the addition of any biologically derived factors or stem cells. When the GAG mimetic nanofiber gels were injected in the infarct site of rodent myocardial infarct model, increased VEGF-A expression and recruitment of vascular cells was observed. This was accompanied with significant degree of neovascularization and better cardiac performance when compared to the control saline group. The results demonstrate the potential of future clinical applications of these bioactive peptide nanofibers as a promising strategy for cardiovascular repair. Statement of Significance We present a synthetic bioactive peptide nanofiber system can enhance cardiac function and enhance cardiovascular regeneration after myocardial infarction (MI) without the addition of growth factors, stem cells or other biologically derived molecules. Current state of the art in cardiac repair after MI utilize at least one of the above mentioned biologically derived molecules, thus our approach is ground-breaking for cardiovascular therapy after MI. In this work, we showed that synthetic glycosaminoglycan (GAG) mimetic peptide nanofiber scaffolds induce neovascularization and cardiomyocyte differentiation for the regeneration of cardiovascular tissue after myocardial infarction in a rat infarct model. When the peptide nanofiber gels were injected in infarct site at rodent myocardial infarct model, recruitment of vascular cells was observed, neovascularization was significantly induced and cardiac performance was improved. These results demonstrate the potential of future clinical applications of these bioactive peptide nanofibers as a promising strategy for cardiovascular repair.
Open Access
Development of peptide based materials as a synthetic scaffold to mimic extracellular matrix
(2017-07) Sever, Melike
Biomaterials obtained through self-assembling process of peptide amphiphile (PA) molecules provide great potential to introduce new therapeutic approaches in regenerative medicine through mimicking the natural environments of different types of tissues. The ability of self-assembled PA nanofibers to mimic natural extracellular matrix (ECM) renders them attractive for regenerative medicine applications. The materials-cell interactions can be modulated through the surface modification of the materials such as introducing the bioactivity via short bioactive peptide sequences derived from natural ECM proteins, which regulate cell behavior through controlling of cellular activities such as proliferation and differentiation. Herein, I described my studies on the development of PA nanofibers in order to mimic natural ECM with differentiation and regeneration purposes. Heparan sulfate mimetic and laminin mimetic PA nanofibers were used as a potential therapeutic approach in Parkinson's disease (PD). These bioactive PA nanofibers were found to reduce the progressive cell loss in SH-SY5Y cells caused by 6-hydroxydopamine treatment in vitro, and improve neurochemical and behavioral consequences of Parkinsonism in rats and provide a promising new strategy for treatment of PD. These nanofibers also proved to be effective in enhancing the viability of Schwann cells and increase nerve growth factor (NGF) release from these cells in vitro. Since NGF has a crucial role in nerve injury repair and myelination in the regenerating nerve, the bioactive epitopes used in this study present also a promising approach as guidance cues for regenerating axons. Tenascin-C is another multifunctional ECM glycoprotein common in both nerve and bone tissue. By decorating peptide nanofibers with tenascin-C derived epitope and using in three-dimensional (3D) system, this tenascin-C mimetic 3D cell culture system was found to provide both the biochemical and physical aspects of the native environment of neural cells, thereby filling the gap between 2D cell culture models and in vivo environments and contributing to more tissue-like structure and more predictive approaches to organogenesis and tissue morphology. Within the scope of this thesis, tenascin-C mimetic nanofibers were also used for osteogenic differentiation of mesenchymal stem cells (MSCs). They were found to significantly enhance the attachment, proliferation, and osteogenic differentiation of MSCs even in the absence of any external bioactive factors and regardless of the suitable stiff mechanical properties normally required for osteogenic differentiation.
Open Access
Development of peptide nanomaterials for neural regeneration
(2015-05) Mammadov, Büşra
Nervous system consists of a dense network of cells and their connections and exhibits a high level of complexity. This complexity arises from the high variety of cell types with very specific functions, the high number of cells along with the abundance of connections between these cells. When combined with the nonproliferative nature of neural cells and inhibitory nature of the pathological extracellular matrix (ECM), this complexity leads to a very limited regenerative potential. Thus neurodegenerative disorders and traumatic injuries of neural tissues lead to lifelong disabilities due to the poor success of current therapies. Novel therapeutic approaches which can overcome barriers that impede neural regeneration are therefore required to be developed. Smartly designed nanomaterials that can direct cells towards desired functions can improve the regeneration of neural tissues. Herein, I have described my work on development of peptide nanofibers for neuroregeneration and biological applications of these nanomaterials. To achieve the regeneration of the nervous system, the composition of the neural ECM under healthy conditions and during early development was mimicked through structural resemblance and bioactive epitope presentation using nanofibers. Laminin derived IKVAV peptide sequence and glycosaminoglycan mimicking, growth factor-binding sulfonated peptide sequence were presented on peptide nanofiber scaffolds. Differentiation of PC-12 cells, a model cell system for neuroregenerative studies, was found to be improved on these nanofiber scaffolds when compared to the cells on epitope free control scaffolds. Cells could even extend neurites on these scaffolds in the presence of inhibitory chondroitin sulfate proteoglycans. These nanofibers also proved to be efficient in sciatic nerve regeneration after injury. When injected into the lumen of polymeric nerve guidance channels, this bioactive nanofiber system provided guidance to the elongating axons and resulted in better axonal regeneration that was evident both from histological analysis and electromyography results. Results of in vitro and in vivo experiments were correlated and indicated the neuroregenerative potential of these peptide nanofibers. In addition, semiconductive oligothiophene was encapsulated in peptide nanofibers without compromising the biocompatibility. These hybrid nanofiber scaffolds can potentially be used for electrical stimulation of neurons that can further boost regeneration.
Open Access
Extracellular matrix mimetic peptide scaffolds for neural stem cell culture and differentiation
(Humana Press, 2014) Mammadov, Busra; Güler, Mustafa O.; Tekinay, Ayşe B.
Self-assembled peptide nanofibers form three-dimensional networks that are quite similar to fibrous extracellular matrix (ECM) in their physical structure. By incorporating short peptide sequences derived from ECM proteins, these nanofibers provide bioactive platforms for cell culture studies. This protocol provides information about preparation and characterization of self-assembled peptide nanofiber scaffolds, culturing of neural stem cells (NSCs) on these scaffolds, and analysis of cell behavior. As cell behavior analyses, viability and proliferation of NSCs as well as investigation of differentiation by immunocytochemistry, qRT-PCR, western blot, and morphological analysis on ECM mimetic peptide nanofiber scaffolds are described.
Open Access
Improving pancreatic islet in vitro functionality and transplantation efficiency by using heparin mimetic peptide nanofiber gels
(Elsevier, 2015) Uzunalli, Gözde; Tumtas, Yasin; Delibasi, T.; Yasa, Oncay; Mercan, S.; Güler, Mustafa O.; Tekinay, Ayse B.
Pancreatic islet transplantation is a promising treatment for type 1 diabetes. However, viability and functionality of the islets after transplantation are limited due to loss of integrity and destruction of blood vessel networks. Thus, it is important to provide a proper mechanically and biologically supportive environment for enhancing both in vitro islet culture and transplantation efficiency. Here, we demonstrate that heparin mimetic peptide amphiphile (HM-PA) nanofibrous network is a promising platform for these purposes. The islets cultured with peptide nanofiber gel containing growth factors exhibited a similar glucose stimulation index as that of the freshly isolated islets even after 7 days. After transplantation of islets to STZ-induced diabetic rats, 28 day-long monitoring displayed that islets that were transplanted in HM-PA nanofiber gels maintained better blood glucose levels at normal levels compared to the only islet transplantation group. In addition, intraperitoneal glucose tolerance test revealed that animals that were transplanted with islets within peptide gels showed a similar pattern with the healthy control group. Histological assessment showed that islets transplanted within peptide nanofiber gels demonstrated better islet integrity due to increased blood vessel density. This work demonstrates that using the HM-PA nanofiber gel platform enhances the islets function and islet transplantation efficiency both in vitro and in vivo.
Open Access
Investigating the effects of bioactive peptide nanofibers on the growth and differentiation behaviour of nervous system cells
(2017-07) Yılmaz, Canelif
Peripheral nerve regeneration is a tightly regulated process that entails the degeneration, proliferation, alignment and remyelination of Schwann cells. Tuning the bioactivity is important to support all of these processes and achieving successful regeneration. Extracellular matrix (ECM) proteins are important molecules for controlling cell behavior and differentiation. Mimicking the natural ECM proteins is a promising approach for promoting regeneration in peripheral nerve injury. In this study, we investigated the biocompatibility and bioactivity of two natural ECM mimicking peptide amphiphile (PA) molecules, heparan sulfate-mimicking PA (HM-PA) and laminin-mimicking PA (LN-PA), and showed that they self-assemble into ECM-like nanofibrous networks. These bioactive nanofibers promote the viability, proliferation and spreading of Schwann cells, and that the combination of the two bioactive epitopes supports both early and late neuroregenerative responses of Schwann cells. We have also shown that these nanofibers support the attachment and neurite extension of dorsal root ganglion neurons, and promotes neurite alignment and assembly in DRG-Schwann cell co-cultures.
Open Access
Investigation of the effects of bioactive peptide nanofibers on acute muscle injury regeneration
(2016-10) Eren Çimenci, Çağla
Skeletal muscle constitutes a large part of the human body. It is a hierarchically organized heterogeneous tissue and is composed of muscle fiber bundles, muscle fibers, myofibrils and myofilaments. Since muscle cells are terminally differentiated, they have limited capacity to renew themselves. Only new cells can fuse with muscle fibers and increase the size and volume of skeletal muscle. Myosatellite cells or satellite cells are small, mononuclear progenitor cells with virtually no cytoplasm. They are located in between the sarcolemma and basement membrane of terminally-differentiated muscle fibers. Satellite cells are precursors to skeletal muscle cells, and are able to give rise to satellite cells or differentiated skeletal muscle cells. They are normally found in silent state in adult muscle, but act as a reserve cell population that is able to proliferate in response to injury and give rise to regenerated muscle and to more satellite cells. Formation of the new muscular tissue is called myogenesis. During this event, satellite cells differentiate into myoblasts, and then myoblasts fuse with each other in order to form myofibers. There are many genes that regulate the myogenesis process and each of them is activated in a different step of myogenesis. Increased or decreased levels of gene expression determine the differentiation capacity. Peptide nanofibers are supramolecular structures formed via self-assembly and they are promising molecules in regenerative medicine and tissue engineering. Peptide-based molecules for tissue regeneration is a widely studied area and currently used in the treatment-investigation of many different tissues such as bone, cartilage, skin and nerve. Since laminin is one of the most abundant proteins found in the basal membrane of the skeletal muscle; in this thesis, we designed and synthesized a laminin-mimetic bioactive (LM/E-PA) molecule functionalized with bioactive groups for mimicking laminin activities and capable of accelerating satellite cell activation. Our research group had previously shown that LM/E-PA containing nanofibers can support muscle differentiation in vitro. In this thesis, the clinical relevance was demonstrated further by assessing laminin-mimetic bioactive scaffold in acute muscle injury in an in vivo rat model. Our findings revealed that this scaffold system significantly promotes satellite cell activation in skeletal muscle and accelerates regeneration following acute muscle injury. In addition, our findings show that the regeneration capacity of the skeletal muscle was increased and consequently regeneration time was reduced. This study is one of the first examples of molecular level and tissue level regeneration of skeletal muscle by using bioactive peptide nanofibers following acute muscle injury, and shows that laminin mimetic nanofiber system is a promising material for development of new therapeutic curatives for acute skeletal muscle injuries.
Open Access
Peptide nanofiber scaffolds for multipotent stromal cell culturing
(Humana Press Inc., 2013) Üstün, Seher; Kocabey, Samet; Güler, Mustafa O.; Tekinay, Ayse B.
Self-assembled peptide nanofibers are versatile materials providing suitable platforms for regenerative medicine applications. This chapter describes the use of peptide nanofibers as extracellular matrix mimetic scaffolds for two-dimensional (2D) and three-dimensional (3D) multipotent stromal cell culture systems and procedures for in vitro experiments using these scaffolds. Preparation of 2D and 3D peptide nanofiber scaffolds and cell culturing procedures are presented as part of in vitro experiments including cell adhesion, viability, and spreading analysis. Analysis of cellular differentiation on peptide nanofiber scaffolds is described through immunocytochemistry, qRT-PCR, and other biochemical experiments towards osteogenic and chondrogenic lineage. © Springer Science+Business Media New York 2013.
Open Access
Peptide nanofibers for controlled growth factor release
(Future Science Ltd., 2013) Tekinay, A. B.; Güler, Mustafa O.; Mumcuoglu, D.; Ustun S.
[No abstract available]
Open Access
Peripheral nerve regeneration by synthetic peptide nanofibers
(2016-09) Geçer, Mevhibe
The peripheral nervous system (PNS) has a complex structure that consists of high numbers of nerve cells and communication networks between the central nervous system and the body parts. Unlike the central nervous system, the PNS exhibits a considerable capacity for regeneration; however, peripheral nerve injuries can nevertheless cause lifelong disability. Various methods are currently available for the treatment of nerve injuries, but autologous nerve grafting is considered as ‘the gold standard’. Donor site morbidity, neuroma formation and failure of functional recovery are some limitations of this technique, especially when used for the repair of long nerve gaps. Polymeric nerve conduits are clinically available alternatives to nerve grafting, and function by guiding the axonal growth and isolating the regenerating axon from the inhibitory environment present in the post-injury neuroma. In this thesis, we used peptide amphiphile molecules (PAs) that can self-assemble into the nanofibers and mimic both the structure and function of healthy ECM of nerve cells for sciatic nerve regeneration. Two bioactive PAs, LN-PA (derived from laminin) and GAG-PA (derived from glycosaminoglycan), were tested for their ability to induce neural regeneration in a rat sciatic nerve model. Hollow nerve conduits were filled with peptide nanofiber gels, and electrophysiology and histology results were compared with autologous graft treated groups. Our results show that bioactive peptide nanofibers are able to boost regeneration and functional motor and sensory recovery. Electromyography results demonstrated that better signal transmission was observed in peptide nanofiber treated groups compared with empty conduits and autograft treated groups. Histological assessments also confirmed that bioactive peptide nanofiber treated groups exhibited better axonal regeneration. These results suggest that these biologically active PA nanofiber gels may be used as a biomaterial for peripheral nerve regeneration in clinical practice.
Open Access
Programming microenvironmental signals with bioactive peptide amphiphiles for skeletal and cardiac myogenesis
(2014) Garip, İmmihan Ceren
The extracellular matrix (ECM) is crucial for the coordination and regulation of various cellular processes, including cell adhesion, recruitment, differentiation and death. ECM components structurally support tissue function and regeneration by acting as a substrate for cell migration and differentiation. In addition, by facilitating the fine localization of signals within their structural framework, these components activate receptors on the cell membrane for the initiation of signal transduction cascades. As such, cell-matrix interactions and matrix-associated signals are important for the normal functioning of cells, as well as for natural or artificially assisted tissue regeneration. In keeping with this ECM-centric approach, we designed and synthesized peptide amphiphiles with bioactive epitopes to resemble the native microenvironment of muscle tissue and to examined their potential in the induction of progenitor cell differentiation into skeletal myotubes and cardiac myocytes. The formation of skeletal myotubes was promoted through the use of basal laminamimetic peptide nanofibers inspired by the chemical structures of laminin and fibronectin, two proteins strongly represented in the skeletal muscle extracellular matrix. We demonstrated that our basal lamina mimetic peptide nanofiber system actively interacts with the cells it contains and enhances their differentiation within 3 days. Morphological analysis and immunocytochemical stainings indicated the formation of differentiated myotubes.We also designed glycosaminoglycan-mimetic peptide amphiphiles to mimic the glycosaminoglycans found in the myocardium. Glycosaminoglycans have been reported to play substantial roles in growth factor binding and the induction of angiogenesis, and their mimicry through peptide amphiphile nanofibers is promising as a combined approach for generating multifunctional cardiovascular tissue engineering scaffolds. We demonstrated that peptide nanofibers enhance the adhesion of cells to the surface and induce cardiac myoblast cells to differentiate into cardiomyocytes through both gene expression analysis and immunostainings. In summary, myogenic platforms were developed by programming signal rich environment from self-assembled peptide nanofibers inspired from the components of the ECM to induce the differentiation of cells. These bioactive nanofiber systems serve as promising platforms for muscle tissue engineering applications.