Browsing by Subject "peptide"

Now showing 1 - 3 of 3
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    Antimicrobial Effects of GL13K Peptide Coatings on S. mutans and L. casei
    (2015-07) Schnitt, Rebecca
    Background: Enamel breakdown around orthodontic brackets, so-called "white spot lesions"�, is the most common complication of orthodontic treatment. White spot lesions are caused by bacteria such as Streptococci and Lactobacilli, whose acidic byproducts cause demineralization of enamel crystals. Aims: The aim of this project was to develop an antimicrobial peptide coating for titanium alloy that is capable of killing acidogenic bacteria, specifically Streptococcus mutans and Lactobacillus casei. The long-term goal is to create an antimicrobial-coated orthodontic bracket with the ability to reduce or prevent the formation of white spot lesions in orthodontic patients thereby improving clinical outcomes. Methods: First, an alkaline etching method with NaOH was established to allow effective coating of titanium discs with GL13K, an antimicrobial peptide derived from human saliva. Coatings were verified by contact angle measures, and treated discs were characterized using scanning electron microscopy. Secondly, GL13K coatings were tested against hydrolytic, proteolytic and mechanical challenges to ensure robust coatings. Third, a series of qualitative and quantitative microbiology experiments were performed to determine the effects of GL13K-L and GL13K-D on S. mutans and L. casei, both in solution and coated on titanium. Results: GL13K-coated discs were stable after two weeks of challenges. GL13K-D was effective at killing S. mutans in vitro at low doses. GL13K-D also demonstrated a bactericidal effect on L. casei, however, in contrast to S. mutans, the effect on L. casei was not statistically significant. Conclusion: GL13K-D is a promising candidate for antimicrobial therapy with possible applications for prevention of white spot lesions in orthodontics.
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    Peptide-functionalized hydrogels for three-dimensional cell culture
    (2016-06) Scott, Carolyn
    Biomimetic scaffolds have played a major role in the advancements in tissue engineering. In addition to mimicking the stiffness, nanofibrous structure, and biochemistry of the native extracellular matrix (ECM), reproducing the three-dimensional (3D) environment of the ECM has been shown to be extremely important. To this end, we designed a co-assembling peptide-amphiphile hydrogel system containing the fibronectin-mimetic PR_g peptide-amphiphile and an E2 diluent peptide-amphiphile for the entrapment and culture of cells in 3D. The E2 diluent peptide amphiphile was designed to screen charges on the PR_g and increase the kinetics of self-assembly in physiologically relevant solutions. Our study investigated two weight percent formulations, 0.5 and 1.0 wt %, and found that in both, entrapped fibroblasts survived encapsulation, proliferated, and deposited collagen IV and fibronectin ECM proteins. The 0.5 wt % gels had a modulus of 429 Pa and supported significantly more fibroblasts proliferation than the 1.0 wt % gels, which had a modulus of 809 Pa. The 1.0 wt% gels though, supported significantly higher mRNA expression and production of ECM proteins. This result indicates by tuning the wt % of our peptide-amphiphile hydrogels, we can encourage either rapid proliferation or ECM deposition. While peptide-amphiphiles are an attractive material for the design of cell scaffolds due to their ability to self-assemble into nanofibrous hydrogels and incorporate multiple biomimetic peptides, there are some limitations associated with these physical hydrogels. One such limitation is that the kinetics of assembly and the mechanical properties of the resulting hydrogels are dependent upon the peptide sequence. We found that the modulus of multifunctional peptide-amphiphile hydrogels ranged from 1000 to 6500 Pa, which was too broad a range to deconvolute the effect of the peptide signal and the effect of mechanical properties. To simplify our system and study the effects of combining ECM protein-mimetic and growth factor-mimetic peptides on the proliferation and function of pancreatic β-cells, peptide mimetics were covalently immobilized on plates. This study found that β-cells proliferate more and secreted significantly more insulin on peptide-functionalized compared to non-functionalized controls. The specific peptide mimetic or combination of peptide mimetics did not significantly affect insulin secretions, but literature suggests that other signals, including cell-cell signaling may play a more significant role in insulin secretion than ECM protein or growth factor signaling. A poly(ethylene glycol) dimethacrylate (PEGDM) hydrogel was functionalized with the laminin-mimetic IKVAV peptide at a 20 µM concentration to match the modulus of non-functionalized hydrogels. This system was used to determine if peptide-functionalization also had an effect in 3D. We found β-cells in IKVAV-functionalized hydrogels proliferated significantly more than β-cells in non-functionalized scaffolds, but no differences in insulin secretion were observed. Together, these studies demonstrate the ability of peptide mimetics to enhance cell proliferation and function of cells in 2D and 3D culture.
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    Synthesis of peptide microstructures for nanogenerators
    (2017-05) Nguyen, Vu
    Electromechanical energy conversion at the small scale utilizing micro/nanomaterials can have significant technological impacts in various areas such as mechanical energy harvesting, tissue engineering, and sensing/actuation. The breakthrough discoveries over the last decade in piezoelectric micro/nanostructures, which converts minute material deformation directly into electrical signal, has spurred intense research in micro/nano scale mechanical energy harvester, also called nanogenerator. Although a variety of advanced inorganic piezoelectric micro/nanostructures have been fabricated, little progress has been made for bioinspired piezoelectric materials, which can enable biocompatible and biodegradable energy harvesting. Meanwhile, piezoelectricity has been widely observed in biological materials such as bone, collagen, viruses and other protein-based materials. Diphenylalanine (FF) peptide, which consists of two naturally occurring phenylalanine amino acids, has attracted significant research interest due to its exceptional mechanical and piezoelectric properties as well as rich biological properties. Thus FF is promising to become one of the most technologically important bioinspired materials for piezoelectric devices, such as mechanical energy harvester. However, many challenges exist in realizing the potential of piezoelectric FF peptide, such as the lack of scalable structural alignment, lack of controllability of polarizations and lack of prototyped device. This thesis aims to address those challenges to advance the applications of FF peptide towards piezoelectric nanogenerator (PENG) and beyond. As an alternative to PENG, which converts minute material deformation into electricity, triboelectric nanogenerator (TENG) has also been proposed recently to harvest energy from large motion through a combination of triboelectric effect and electrostatic induction. Since tiny material deformation and large motion are usually available together, advances in nanogenerator are needed to harvest them effectively. Due to the apparent complementary energy conversion mechanisms of piezoelectric and triboelectric effects, performance of TENG in various environmental conditions will be studied, and hybridization of PENG and TENG into one device will also be explored as an approach to enhance the outputs of the mechanical energy harvester. In overview, first this thesis will develop a novel low-temperature epitaxial growth process to address the challenge of synthesizing aligned piezoelectric FF peptide structures in a scalable and controllable manner. Second, the random orientation and unswitchability of its polarization will be addressed by modifying the growth parameters and including an applied external electric field during the growth. The improved FF microstructures will be used to demonstrate the first peptide PENG. Third, a standalone TENG will be studied for its operation in various environmental conditions, verifying its wide applicability. Finally, a hybrid nanogenerator structure will be proposed to constructively combine the outputs of FF peptide PENG with a TENG, and the hybrid energy conversion process will be experimentally verified.