Browsing by Subject "Collagen"

Now showing 1 - 11 of 11

Open Access
Collagen peptide presenting nanofibrous scaffold for intervertebral disc regeneration
(American Chemical Society, 2019) Uysal, Özge; Arslan, Elif; Gülseren, Gülcihan; Kılınç, M. C.; Doğan, İ.; Özalp, H.; Çağlar, Y. Ş.; Güler, M. O.; Tekinay, Ayşe B.
Lower back pain (LBP) is a prevalent spinal symptom at the lumbar region of the spine, which severely effects quality of life and constitutes the number one cause of occupational disability. Degeneration of the intervertebral disc (IVD) is one of the well-known causes contributing to the LBP. Therapeutic biomaterials inducing IVD regeneration are promising candidates for IVD degeneration treatments. Here, we demonstrate a collagen peptide presenting nanofiber scaffold to mimic the structure and function of the natural extracellular matrix of the tissue for IVD regeneration. The collagen peptide presenting nanofiber was designed by using a Pro-Hyp-Gly (POG) peptide sequence on a self-assembling peptide amphiphile molecule, which assembled into nanofibers forming scaffolds. Injection of collagen peptide presenting peptide nanofiber scaffold into the degenerated rabbit IVDs induced more glycosaminoglycan and collagen deposition compared to controls. Functional recovery of the tissue was evaluated by degeneration index score, where the bioactive scaffold was shown to provide functional recovery of the IVD degeneration. These results showed that the collagen peptide presenting nanofiber scaffold can prevent the progression of IVD degeneration and provide further functional recovery of the tissue.
Open Access
Contact guidance enhances the quality of a tissue engineered corneal stroma
(John Wiley & Sons, Inc., 2008) Vrana, E.; Builles, N.; Hindie, M.; Damour O.; Aydınlı, Atilla; Hasirci, V.
Corneal stroma is a very complex structure, composed of 200 lamellae of oriented collagen fibers. This highly complex nature of cornea is known to be important for its transparency and mechanical integrity. Thus, an artificial cornea design has to take into account this complex structure. In this study, behavior of human corneal keratocytes on collagen films patterned with parallel channels was investigated. Keratocytes proliferated well on films and reached confluency after 7 days in the incubation medium. Nearly all of the cells responded to the patterns and were aligned in contrast to the cells on unpatterned surfaces. Collagen type I and keratan sulfate secreted by keratocytes on patterned films appeared to be aligned in the direction of the patterns. The films showed an intermediate degradation over the course of a month. On the whole, transparency of the films increased with degradation and decreased by the presence of the cells. The decrease was, however, low and transparency level was maintained on the patterned films while on the unpatterned films a sharp decrease in transparency was followed by an improvement. This was due to the more organized distribution of cells and the oriented secretion of extracellular matrix molecules on patterned collagen films. Thus, these results suggest that application of contact guidance in cornea tissue engineering may facilitate the remodeling process, hence decrease the rehabilitation period.
Open Access
Cornea engineering on polyester carriers
(John Wiley & Sons, Inc., 2006) Zorlutuna, P.; Tezcaner, A.; Kiyat, I.; Aydınlı, Atilla; Hasirci, V.
In this study, biodegradable polyester based carriers were designed for tissue engineering of the epithelial and the stromal layers of the cornea, and the final construct was tested in vitro. In the construction of the epithelial layer, micropatterned films were prepared from blends of biodegradable and biocompatible polyesters of natural (PHBV) and synthetic (P(L/DL)LA) origin, and these films were seeded with D407 (retinal pigment epithelial) cells. To improve cell adhesion and growth, the films were coated with fibronectin. To serve as the stromal layer of the cornea, highly porous foams of P(L/DL)LA-PHBV blends were seeded with 3T3 fibroblasts. Cell numbers on the polyester carriers were significantly higher than those on the tissue culture polystyrene control. The cells and the carriers were characterized scanning electron micrographs showed that the foam was highly porous and the pores were interconnected. 3T3 Fibroblasts were distributed quite homogeneously at the seeding site, but probably because of the high thickness of the carrier (∼6 mm); they could not sufficiently populate the core (central parts of the foam) during the test duration. The D407 cells formed multilayers on the micropatterned polyester film. Immunohistochemical studies showed that the cells retained their phenotype during culturing; D407 cells formed tight junctions characteristic of epithelial cells, and 3T3 cells deposited collagen type I into the foams. On the basis of these results, we concluded that the micropatterned films and the foams made of P(L/DL)LA-PHBV blends have a serious potential as tissue engineering carriers for the reconstruction of the epithelial and stromal layers of the cornea.
Open Access
Development of bioactive peptide nanofibers for intervertebral disc regeneration
(2017-08) Uysal, Özge
Lower back pain (LBP) and neck problems are the most common orthopedic diseases worldwide, and the main reason behind LBP is intervertebral disc degeneration (IVDD). Therefore, specialized therapeutic applications to induce intervertebral disc (IVD) regeneration is a necessity. Here, we report the use of a collagen-mimetic bioactive peptide nanofiber scaffold (Col-PA/E-PA) for the improvement of disc regeneration by recapitulating the structure and function of the natural extracellular matrix (ECM) of intervertebral connective tissue. Following two weeks of degeneration, the bioactive nanofiber scaffold was topically applied and the IVD regeneration process was observed through histochemical analyses. The collagen-mimetic bioactive peptide nanofiber system was found to significantly promote glycosaminoglycan and collagen deposition at the site of injury compared to control nanofiber system and saline groups. In addition, the bioactive scaffold was consistently associated with lower values in degeneration scoring analyses, confirming the functional recovery of the tissue. Overall, the collagen-mimetic peptide nanofiber scaffold was able to prevent the progression of IVD degeneration and provide further functional recovery to the tissue.
Open Access
Diabetic wound regeneration using heparin-mimetic peptide amphiphile gel in db/db mice
(Royal Society of Chemistry, 2017) Senturk, Berna; Demircan, Burak M.; Ozkan, Alper D.; Tohumeken, Sehmus; Delibasi, T.; Güler, Mustafa O.; Tekinay, Ayse B.
There is an urgent need for more efficient treatment of chronic wounds in diabetic patients especially with a high risk of leg amputation. Biomaterials capable of presenting extracellular matrix-mimetic signals may assist in the recovery of diabetic wounds by creating a more conducive environment for blood vessel formation and modulating the immune system. In a previous study, we showed that glycosaminoglycan-mimetic peptide nanofibers are able to increase the rate of closure in STZ-induced diabetic rats by induction of angiogenesis. The present study investigates the effect of a heparin-mimetic peptide amphiphile (PA) nanofiber gel on full-thickness excisional wounds in a db/db diabetic mouse model, with emphasis on the ability of the PA nanofiber network to regulate angiogenesis and the expression of pro-inflammatory cytokines. Here, we showed that the heparin-mimetic PA gel can support tissue neovascularization, enhance the deposition of collagen and expression of alpha-smooth muscle actin (α-SMA), and eliminate the sustained presence of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) in the diabetic wound site. As the absence of neovascularization and overexpression of pro-inflammatory markers are a hallmark of diabetes and interfere with wound recovery by preventing the healing process, the heparin-mimetic PA treatment is a promising candidate for acceleration of diabetic wound healing by modulating angiogenesis and local immune response. © 2017 The Royal Society of Chemistry.
Open Access
Effect of double growth factor release on cartilage tissue engineering
(2013) Ertan, A.B.; Yilgor P.; Bayyurt, B.; Çalikoǧlu, A.C.; Kaspar Ç.; Kök F.N.; Kose G.T.; Hasirci V.
The effects of double release of insulin-like growth factor I (IGF-I) and growth factor β1 (TGF-β1) from nanoparticles on the growth of bone marrow mesenchymal stem cells and their differentiation into cartilage cells were studied on PLGA scaffolds. The release was achieved by using nanoparticles of poly(lactic acid-co-glycolic acid) (PLGA) and poly(N-isopropylacrylamide) (PNIPAM) carrying IGF-I and TGF-β1, respectively. On tissue culture polystyrene (TCPS), TGF-β1 released from PNIPAM nanoparticles was found to have a significant effect on proliferation, while IGF-I encouraged differentiation, as shown by collagen type II deposition. The study was then conducted on macroporous (pore size 200-400μm) PLGA scaffolds. It was observed that the combination of IGF-I and TGF-β1 yielded better results in terms of collagen type II and aggrecan expression than GF-free and single GF-containing applications. It thus appears that gradual release of a combination of growth factors from nanoparticles could make a significant contribution to the quality of the engineered cartilage tissue. © 2011 John Wiley & Sons, Ltd.
Open Access
Heparin mimetic peptide nanofiber gel promotes regeneration of full thickness burn injury
(Elsevier Ltd, 2017) Yergoz, F.; Hastar, N.; Cimenci, C. E.; Ozkan, A. D.; Güler, Mustafa O.; Tekinay, A. B.; Tekinay, T.; Güler, Mustafa O.
Burn injuries are one of the most common types of trauma worldwide, and their unique physiology requires the development of specialized therapeutic materials for their treatment. Here, we report the use of synthetic, functional and biodegradable peptide nanofiber gels for the improved healing of burn wounds to alleviate the progressive loss of tissue function at the post-burn wound site. These bioactive nanofiber gels form scaffolds that recapitulate the structure and function of the native extracellular matrix through signaling peptide epitopes, which can trigger angiogenesis through their affinity to basic growth factors. In this study, the angiogenesis-promoting properties of the bioactive scaffolds were utilized for the treatment of a thermal burn model. Following the excision of necrotic tissue, bioactive gels and control solutions were applied topically onto the wound area. The wound healing process was evaluated at 7, 14 and 21 days following injury through histological observations, immunostaining and marker RNA/protein analysis. Bioactive peptide nanofiber-treated burn wounds formed well-organized and collagen-rich granulation tissue layers, produced a greater density of newly formed blood vessels, and exhibited increased re-epithelialization and skin appendage development with minimal crust formation, while non-bioactive peptide nanofibers and the commercial wound dressing 3M™ Tegaderm™ did not exhibit significant efficiency over sucrose controls. Overall, the heparin-mimetic peptide nanofiber gels increased the rate of repair of burn injuries and can be used as an effective means of facilitating wound healing.
Open Access
A hybrid nanofiber matrix to control the survival and maturation of brain neurons
(Elsevier BV, 2012) Sur, S.; Pashuck, E. T.; Güler, Mustafa O.; Ito, M.; Stupp, S. I.; Launey, T.
Scaffold design plays a crucial role in developing graft-based regenerative strategies, especially when intended to be used in a highly ordered nerve tissue. Here we describe a hybrid matrix approach, which combines the structural properties of collagen (type I) with the epitope-presenting ability of peptide amphiphile (PA) nanofibers. Self-assembly of PA and collagen molecules results in a nanofibrous scaffold with homogeneous fiber diameter of 20-30 nm, where the number of laminin epitopes IKVAV and YIGSR can be varied by changing the PA concentrations over a broad range of 0.125-2 mg/ml. Granule cells (GC) and Purkinje cells (PC), two major neuronal subtypes of cerebellar cortex, demonstrate distinct response to this change of epitope concentration. On IKVAV hybrid constructs, GC density increases three-fold compared with the control collagen substrate at a PA concentration of ≥0.25 mg/ml, while PC density reaches a maximum (five-fold vs. control) at 0.25 mg/ml of PA and rapidly decreases at higher PA concentrations. In addition, adjustment of the epitope number allowed us to achieve fine control over PC dendrite and axon growth. Due to the ability to modulate neuron survival and maturation by easy manipulation of epitope density, our design offers a versatile test bed to study the extracellular matrix (ECM) contribution in neuron development and the design of optimal neuronal scaffold biomaterials. © 2011 Elsevier Ltd.
Open Access
Investigating physical properties of hybrid hyaluronic acid and collagen compositions of GelMA microgels toward tissue engineering and organ-on-chip applications
(American Chemical Society, 2023-10-13) Çınar, Aslı Gizem; Munir, Iqra
Microgels are promising tools in biomedical sciences to be utilized as 3D cell culture scaffolds and cell-delivery or drug-delivery vehicles. Carrying the desired properties of hydrogels, they can be fabricated from various materials in different shapes and sizes. Additionally, due to their increased surface-to-volume ratio, they provide fast nutrient, waste, and species transport with altered solute–material interactions. Despite their micrometer size and the differentiated behaviors that come with these properties, the characterization methods utilized so far to investigate their physical and morphological properties are majorly carried out on their bulk versions, resulting in inaccurate estimates and somewhat missed information. Here, in this work, swelling, degradation, and morphological examination assays curated for microgels are proposed to reflect the actual behavior of microgels. Accordingly, gelatin methacryloyl, complemented with hyaluronic acid methacrylate and collagen to set an example of different types of polymer networks, was fabricated into microgels using a droplet microfluidic platform with in situ photopolymerization. An easy washing and drying process is proposed as a substitution for the harsh conditions of lyophilization for morphological analysis, resulting in a much more accurate picture of the porous structures. Swelling and enzymatic degradation assays, usually done by immersing a bulk hydrogel in a medium for an extended period, are substituted with swelling and degrading individual microgels in a custom-made platform that enables real-time, statistically significant data acquisition. Results showed that, due to their small size, swelling occurs in a matter of minutes, with different temporal profiles depending on the medium and microgel compositions, and enzymatic degradation takes place in a couple of hours with varying behaviors, changing due to the polymers, enzyme type, and concentration. Overall, this work highlights the necessity and importance of characterizing microgels in their respective sizes, hopefully advancing their utilization in microphysiological systems and biomedical applications.
Open Access
A new tool for differentiating hepatocellular cancer cells: patterned carbon nanotube arrays
(Elsevier, 2015) Kucukayan-Dogu, G.; Gozen, D.; Bitirim, V.; Akcali, K. C.; Bengu, E.
We aimed to develop a new approach to detect the invasiveness and metastatic degree of hepatocellular carcinoma cells (HCC) based on their epithelial mesenchymal transition (EMT) status by using patterned carbon nanotubes (CNT) without any further surface functionalization. We used well differentiated HUH7 and poorly differentiated SNU182 cells to examine and compare their adhesive features on patterned CNTs. We found that the well differentiated HUH7 cells attached significantly more on the patterned CNTs than the poorly differentiated SNU182 cells due to the difference in epithelial and mesenchymal phenotypes of these cells. Collagen coated patterned CNTs having less roughness resulted in a decrease in the number of attached cells compared to non-coated patterned surfaces indicating that surface topography playing also a vital role on the cell attachment. LDH testing indicated no adverse, or thereof toxic effect of collagen coated or non-coated patterned surfaces on the HCC cells. The results of this study clearly suggest that patterned CNT surfaces can be used as a diagnostic tool to determine the invasiveness and metastatic level of HCCs. Hence, CNTs could be considered as a promising diagnostic tool for the detection of differentiation and invasiveness of the HCC cells. © 2015 Elsevier B.V. All rights reserved.
Open Access
Patterned carbon nanotubes as a new three-dimensional scaffold for mesenchymal stem cells
(Elsevier, 2013) Bitirim, Verda Ceylan; Küçükayan-Doğu, Gökçe; Bengü, Erman; Akçalı, Kamil Can
We investigated the cellular adhesive features of mesenchymal stem cells (MSC) on non-coated and collagen coated patterned and vertically aligned carbon nanotube (CNT) structures mimicking the natural extra cellular matrix (ECM). Patterning was achieved using the elasto-capillary induced by water treatment on the CNT arrays. After confirmation with specific markers both at transcript and protein levels, MSCs from different passages were seeded on either collagen coated or non-coated patterned CNTs. Adhesion and growth of MSCs on the patterned CNT arrays were examined using scanning electron microscopy image analysis and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-tetrazolium bromide (MTT) assays. The highest MSC count was observed on the non-coated patterned CNTs at passage zero, while decreasing numbers of MSCs were found at the later passages. Similarly, MTT assay results also revealed a decrease in the viability of the MSCs for the later passages. Overall, the cell count and viability experiments indicated that MSCs were able to better attach to non-coated patterned CNTs compared to those coated with collagen. Therefore, the patterned CNT surfaces can be potentially used as a scaffold mimicking the ECM environment for MSC growth which presents an alternative approach to MSC-based transplantation therapy applications.