Browsing by Subject "Gels"

Now showing 1 - 8 of 8

Open Access
Controlled enzymatic stability and release characteristics of supramolecular chiral peptide amphiphile nanofiber gels
(Elsevier B.V., 2017) Zengin, A.; Cinar, G.; Güler, Mustafa O.
Supramolecular bioarchitectures formed by assembly of achiral or chiral building blocks play important roles in various biochemical processes. Stereochemistry of amino acids is important for structural organization of peptide and protein assemblies and structure-microenvironment interactions. In this study, oppositely charged peptide amphiphile (PA) molecules with L-, D- and mixture of L- and D-amino acid conformations are coassembled into supramolecular nanofibers and formed self-supporting gels at pH 7.4 in water. The enzymatic stability of the PA nanofiber gels was studied in the presence of proteinase K enzyme, which digest a broad spectrum of proteins and peptides. The structural changes on the chiral PA nanofibers were also analyzed at different time periods in the presence of enzymatic activity. Controlled release of a model cargo molecule through the chiral PA nanofiber gels was monitored. The diffusivity parameters were measured for all gel systems. Release characteristics and the enzymatic stability of the peptide nanofiber gels were modulated depending on organization of the chiral PA molecules within the supramolecular assemblies.
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
Lithium salt-nonionic surfactant lyotropic liquid crystalline gel-electrolytes with redox couple for dye sensitized solar cells
(Royal Society of Chemistry, 2016) Yılmaz, E.; Olutaş, E. B.; Barım, G.; Bandara, J.; Dag, Ö.
Lithium salt (LiCl, LiBr, LiI, or LiNO3) and a non-ionic surfactant (such as 10-lauryl ether, C12E10) form lyotropic liquid crystalline (LLC) mesophases in the presence of a small amount of water. The mesophases can be prepared as gels by mixing all the ingredients in one pot or in the solution phase that they can be prepared by coating over any substrate where the LLC phase is formed by evaporating excess solvent. The second method is easier and produces the same mesophase as the first method. A typical composition of the LLC phases consists of 2-3 water per salt species depending on the counter anion. The LiI-C12E10 mesophases can also be prepared by adding I2 to the media to introduce an I-/I3 - redox couple that may be used as a gel-electrolyte in a dye-sensitized solar cell. Even though the mesophases contain a large amount of water in the media, this does not affect the cell performance. The water molecules in the mesophase are in the hydration sphere of the ions and do not act like bulk water, which is harmful to the anode of the dye-sensitized solar cells (DSSC). There are two major drawbacks of the salt-surfactant LLC mesophases in the DSSCs; one is the diffusion of the gels into the pores of the anode electrode and the other is the low ionic conductivity. The first issue was partially overcome by introducing the gel content as a solution and the gelation was carried in/over the pores of the dye modified titania films. To increase the ionic conductivity of the gels, other salts (such as LiCl, LiBr, and LiNO3) with better ionic conductivity were added to the media, however, those gels behave less effectively than pure LiI/I2 systems. Overall, the DSSCs constructed using the LLC electrolyte display high short circuit current (Isc of around 10 mA), high open circuit voltage (Voc of 0.81 V) and good fill factor (0.69) and good efficiency (3.3%). There is still room for improvement in addressing the above issues in order to enhance the cell efficiency by developing new methods of introducing the gel-electrolytes into the mesopores of the anode electrode.
Open Access
Local delivery of doxorubicin through supramolecular peptide amphiphile nanofiber gels
(Royal Society of Chemistry, 2017) Cinar, G.; Ozdemir, A.; Hamsici, S.; Gunay, G.; Dana, A.; Tekinay, A. B.; Güler, Mustafa O.
Peptide amphiphiles (PAs) self-assemble into supramolecular nanofiber gels that provide a suitable environment for encapsulation of both hydrophobic and hydrophilic molecules. The PA gels have significant advantages for controlled delivery applications due to their high capacity to retain water, biocompatibility, and biodegradability. In this study, we demonstrate injectable supramolecular PA nanofiber gels for drug delivery applications. Doxorubicin (Dox), as a widely used chemotherapeutic drug for breast cancer treatment, was encapsulated within the PA gels prepared at different concentrations. Physical and chemical properties of the gels were characterized, and slow release of the Dox molecules through the supramolecular PA nanofiber gels was studied. In addition, the diffusion constants of the drug molecules within the PA nanofiber gels were estimated using fluorescence recovery after the photobleaching (FRAP) method. The PA nanofiber gels did not show any cytotoxicity and the encapsulation strategy enhanced the activity of drug molecules on cellular viability through prolonged release compared to direct administration under in vitro conditions. Moreover, the local in vivo injection of the Dox encapsulated PA nanofiber gels (Dox/PA) to the tumor site demonstrated the lowest tumor growth rate compared to the direct Dox injection and increased the apoptotic cells within the tumor tissue for local drug release through the PA nanofiber gels under in vivo conditions.
Open Access
Nano-structured organically modified silica thin films for functional surfaces
(2011) Bayındır, Mehmet; Yıldırım, Adem; Budunoglu, Hülya; Yaman, Mecit; Deniz, Hakan; Güler, Mustafa O.
We report a template-free sol-gel method for preparation of nanoporous ormosil thin films at ambient conditions. The thin films are coated to the surfaces by using colloidal suspensions of ormosil gels. Gels are synthesized by using a trifunctional organosilane monomer, methyltrimethoxysilane (MTMS), with a two-step acid base reaction. We prepared several ormosil thin films on glass, metal, plastic and paper surfaces with different functionalities like superhydrophobic, antireflective, antifogging and ice retarding properties, from gels prepared in different conditions. Also films on flexible substrates exhibits durable surface properties after several bending cycles. In addition, we also demonstrate that these thin films can be used for fluorescent sensing of explosives by doping them with fluorescent dyes.
Open Access
One-Step Fabrication of Biocompatible Multifaceted Nanocomposite Gels and Nanolayers
(American Chemical Society, 2017) Topuz, F.; Bartneck, M.; Pan, Y.; Tacke, F.
Nanocomposite gels are a fascinating class of polymeric materials with an integrative assembly of organic molecules and organic/inorganic nanoparticles, offering a unique hybrid network with synergistic properties. The mechanical properties of such networks are similar to those of natural tissues, which make them ideal biomaterial candidates for tissue engineering applications. Existing nanocomposite gel systems, however, lack many desirable gel properties, and their suitability for surface coatings is often limited. To address this issue, this article aims at generating multifunctional nanocomposite gels that are injectable with an appropriate time window, functional with bicyclononynes (BCN), biocompatible and slowly degradable, and possess high mechanical strength. Further, the in situ network-forming property of the proposed system allows the fabrication of ultrathin nanocomposite coatings in the submicrometer range with tunable wettability and roughness. Multifunctional nanocomposite gels were fabricated under cytocompatible conditions (pH 7.4 and T = 37 °C) using laponite clays, isocyanate (NCO)-terminated sP(EO-stat-PO) macromers, and clickable BCN. Several characterization techniques were employed to elucidate the structure-property relationships of the gels. Even though the NCO-sP(EO-stat-PO) macromers could form a hydrogel network in situ on contact with water, the incorporation of laponite led to significant improvement of the mechanical properties. BCN motifs with carbamate links were used for a metal-free click ligation with azide-functional molecules, and the subsequent gradual release of the tethered molecules through the hydrolysis of carbamate bonds was shown. The biocompatibility of the hydrogels was examined through murine macrophages, showing that the material composition strongly affects cell behavior.
Open Access
Template-free synthesis of organically modified silica mesoporous thin films for TNT sensing
(American Chemical Society, 2010) Yildirim, A.; Budunoglu, H.; Deniz, H.; Güler, Mustafa O.; Bayındır, Mehmet
In this paper, we present a facile, template-free sol−gel method to produce fluorescent and highly mesoporous organically modified silica (ORMOSIL) thin films for vapor phase sensing of TNT. An alkyltrifunctional, methyltrimethoxysilane MTMS precursor was used to impart hydrophobic behavior to gel network in order to form the spring back effect. In this way, porous films (up to 74% porosity) are obtained at ambient conditions. Fluorescent molecules are physically encapsulated in the ORMOSIL network during gelation. Fluorescence of the films was found to be stable even after 3 months, proving the successful fixing of the dye into the ORMOSIL network. The functional ORMOSIL thin films exhibited high fluorescence quenching upon exposition to TNT and DNT vapor. Fluorescence quenching responses of the films are thickness-dependent and higher fluorescence quenching efficiency was observed for the thinnest film (8.6% in 10 s). The prepared mesoporous ORMOSIL thin films have great potential in new sensor and catalysis applications.
Open Access
Three-Dimensional Laminin Mimetic Peptide Nanofiber Gels for In Vitro Neural Differentiation
(Wiley-VCH Verlag, 2017) Gunay, Gokhan; Sever, Melike; Tekinay, Ayse B.; Güler, Mustafa O.
The extracellular matrix (ECM) provides biochemical signals and structural support for cells, and its functional imitation is a fundamental aspect of biomaterial design for regenerative medicine applications. The stimulation of neural differentiation by a laminin protein-derived epitope in two-dimensional (2D) and three-dimensional (3D) environments is investigated. The 3D gel system is found to be superior to its 2D counterpart for the induction of neural differentiation, even in the absence of a crucial biological inducer in nerve growth factor (NGF). In addition, cells cultured in 3D gels exhibits a spherical morphology that is consistent with their form under in vivo conditions. Overall, the present study underlines the impact of bioactivity, dimension, and NGF addition, as well as the cooperative effects thereof, on the neural differentiation of PC-12 cells. These results underline the significance of 3D culture systems in the development of scaffolds that closely replicate in vivo environments for the formation of cellular organoid models in vitro. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim