Browsing by Subject "Amyloid"

Now showing 1 - 5 of 5

Open Access
Gemcitabine integrated nano-prodrug carrier system
(American Chemical Society, 2017) Hamsici, S.; Ekiz, M. S.; Ciftci, G. C.; Tekinay, A. B.; Güler, Mustafa O.
Peptide nanomaterials have received a great deal of interest in drug-delivery applications due to their biodegradability, biocompatibility, suitability for large-scale synthesis, high drug-loading capacities, targeting ability, and ordered structural organization. The covalent conjugation of drugs to peptide backbones results in prolonged circulation time and improved stability of drugs. Therapeutic efficacy of gemcitabine, which is used for breast cancer treatment, is severely compromised due to its rapid plasma degradation. Its hydrophilic nature poses a challenge for both its efficient encapsulation into nanocarrier systems and its sustained release property. Here, we designed a new peptide prodrug molecule for the anticancer drug gemcitabine, which was covalently conjugated to the C-terminal of 9-fluorenylmethoxy carbonyl (Fmoc)-protected glycine. The prodrug was further integrated into peptide nanocarrier system through noncovalent interactions. A pair of oppositely charged amyloid-inspired peptides (Fmoc-AIPs) were exploited as components of the drug-carrier system and self-assembled into one-dimensional nanofibers at physiological conditions. The gemcitabine integrated nanoprodrug carrier system exhibited slow release and reduced the cellular viability of 4T1 breast cancer cell line in a time- and concentration-dependent manner.
Open Access
Microbial amyloids as functional biomaterials
(2021-01) Kehribar, Ebru Şahin
Amyloids are fibrillar aggregations of proteins, dominated by β-sheets in the structure. Although amyloids are historically associated with disorders, they emerged as outstanding biomaterials due to their high mechanical strength and rigidity that provides resistance to physical and chemical stress. Also, amyloids can easily be functionalized with peptide groups using genetic engineering approaches. Ease of functionalization in addition to aforementioned properties makes amyloid fibers excellent candidates for biomaterials with desired characteristics. In this thesis, we focused on recombinant production, characterization and functionalization of several amyloid proteins from different microorganisms. Binding behavior of amyloid fibrils on medically relevant surfaces are critical for controlling the coating characteristics and desired surface properties of biomaterials. For this reason, we firstly characterized the binding kinetics of CsgA and CsgB curli proteins on silica, gold and hydroxyapatite surfaces to precisely control their surface adhesion. According to the physicochemical properties of surfaces, CsgA, CsgB and their mixture displayed different binding behavior. Furthermore, functionalization of amyloid fibers to enhance their binding kinetics to surfaces and to organisms may hold great potentials for biomaterial applications. From this perspective, we hypothesized that glycosylation could enhance surface adhesiveness of curli fibers. For this purpose, TasA protein is engineered to obtain a glycosylation site and TasA fibers depicted an increased adhesiveness to gold surfaces upon glycosylation. Finally, we functionalized CsgA curli fibers with RGD peptide to increase adhesiveness to living cells. RGD peptide addition caused a significant increase in the adhesiveness of mammalian cells onto coated surfaces. In conclusion, amyloid proteins can serve as superior biomaterials with desired functions and characteristics. Physicochemical properties of surfaces and proteins can have essential impacts on their interaction. In order to diversify those properties, amyloid fibers can be functionalized for specific purposes such as improved surface and cell adhesion. Characterization of protein/surface interactions for amyloid proteins provides important clues for optimal biomaterial surface design and functionalization with different peptide groups can extend their application capacity as superior biomaterials.
Open Access
Monitoring molecular assembly of biofilms using quartz crystal microbalance with dissipation
(Springer, 2022) Yuca, E.; Şeker, Urartu Özgür Şafak; Arluison, Véronique; Wien, Frank; Marcoleta, Andrés
The structure and the functionality of biofilm proteins, the main components of the extracellular matrix, can be tuned by protein engineering. The use of binding kinetics data has been demonstrated in the characterization of recombinantly produced biofilm proteins to control their behavior on certain surfaces or under certain conditions. Quartz crystal microbalance with dissipation monitoring (QCM-D) allows measuring the change in resonance frequency and the energy loss and distribution upon the interaction of molecules with the surface. The characterization of the molecular assembly of curli biofilm proteins on different surfaces using QCM-D is presented here as a detailed protocol. The experimental procedure detailed in this chapter can be applied and modified for other biofilm proteins or subunits to determine their surface adsorption and kinetic binding characteristics.
Open Access
Peptide based ligand discovery to prevent protein aggregation in neurodegenerative disease conditions
(2019-09) Beğli, Özge
Neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease and Huntington’s disease are cognitively and physically debilitating and progressive diseases due to the gradual and irreversible loss of discrete neuronal populations in the brain. In addition to millions of people worldwide suffering from them, the prevalence of the neurodegenerative diseases dramatically increases with the increasing lifespan of the population. Most of the current therapeutic strategies either target toxic aggregates in neurons or support the healthy cells in diseased region. However, these interventions provide only symptomatic relief and deceleration of disease progression. Besides, aggregation involves a locking phase in which irreversible transition of soluble monomeric and oligomeric molecules into insoluble fibrous structures occurs. During aggregation, fragmentation of mature fibrils leads to the formation of new oligomeric structures possessing seeding activity. The seeds behaving as a nucleation unit trigger other structures to join the accumulated proteins. Synthetic biology is an emerging field that suggests therapeutic solutions for several diseases. Development of synthetic proteins such as artificial transcription factors and improved antibodies, artificial cell transplants with controlled secretion, designed inhibitory RNA molecules and antisense oligonucleotides, gene circuits and logic gates, synthetic viruses as an advanced delivery system and genome editing technologies using programmable nucleases are revolutionary approaches for the diagnosis and treatment of diseases. With the utilization of a variety of advanced tools, synthetic biology is extremely promising to treat neurodegenerative disorders too. In this study, biotechnological approaches and tools such as gene cloning, yeast surface display and phage display library have been used to target neurodegenerative proteins before aggregation takes place. Neurodegenerative proteins were cloned into a plasmid DNA within bacteria and displayed on the surface of Saccharomyces cerevisiae cells. A phage display library has been screened against those neurodegenerative proteins and binding peptides of these proteins have been selected following recursive rounds of binding and washing steps. Peptides that bind to neurodegenerative proteins with high affinity possess the potential to block them and prevent the initiation of aggregation. Beside to the promising results of neuroprotective and neurorestorative interventions, this strategy can provide prevention of aggregation which is the underlying cause of neurodegeneration.
Open Access
Synthetic biogenesis of bacterial amyloid nanomaterials with tunable inorganic-organic interfaces and electrical conductivity
(American Chemical Society, 2017) Seker U.O.S.; Chen, A. Y.; Citorik, R. J.; Lu, T. K.
Amyloids are highly ordered, hierarchal protein nanoassemblies. Functional amyloids in bacterial biofilms, such as Escherichia coli curli fibers, are formed by the polymerization of monomeric proteins secreted into the extracellular space. Curli is synthesized by living cells, is primarily composed of the major curlin subunit CsgA, and forms biological nanofibers with high aspect ratios. Here, we explore the application of curli fibers for nanotechnology by engineering curli to mediate tunable biological interfaces with inorganic materials and to controllably form gold nanoparticles and gold nanowires. Specifically, we used cell-synthesized curli fibers as templates for nucleating and growing gold nanoparticles and showed that nanoparticle size could be modulated as a function of curli fiber gold-binding affinity. Furthermore, we demonstrated that gold nanoparticles can be preseeded onto curli fibers and followed by gold enhancement to form nanowires. Using these two approaches, we created artificial cellular systems that integrate inorganic-organic materials to achieve tunable electrical conductivity. We envision that cell-synthesized amyloid nanofibers will be useful for interfacing abiotic and biotic systems to create living functional materials.