Doctor of Philosophy, University of Washington (2018)
Master of Science in Engr, Universitetet I Linkoping (2013)
Elastin-like Proteins to Support Peripheral Nerve Regeneration in Guidance Conduits.
ACS biomaterials science & engineering
2021; 7 (9): 4209-4220
Synthetic nerve guidance conduits (NGCs) offer an alternative to harvested nerve grafts for treating peripheral nerve injury (PNI). NGCs have been made from both naturally derived and synthesized materials. While naturally derived materials typically have an increased capacity for bioactivity, synthesized materials have better material control, including tunability and reproducibility. Protein engineering is an alternative strategy that can bridge the benefits of these two classes of materials by designing cell-responsive materials that are also systematically tunable and consistent. Here, we tested a recombinantly derived elastin-like protein (ELP) hydrogel as an intraluminal filler in a rat sciatic nerve injury model. We demonstrated that ELPs enhance the probability of forming a tissue bridge between the proximal and distal nerve stumps compared to an empty silicone conduit across the length of a 10 mm nerve gap. These tissue bridges have evidence of myelinated axons, and electrophysiology demonstrated that regenerated axons innervated distal muscle groups. Animals implanted with an ELP-filled conduit had statistically higher functional control at 6 weeks than those that had received an empty silicone conduit, as evaluated by the sciatic functional index. Taken together, our data support the conclusion that ELPs support peripheral nerve regeneration in acute complete transection injuries when used as an intraluminal filler. These results support the further study of protein engineered recombinant ELP hydrogels as a reproducible, off-the-shelf alternative for regeneration of peripheral nerves.
View details for DOI 10.1021/acsbiomaterials.0c01053
View details for PubMedID 34510904
Vibrational Sum-Frequency Scattering as a Sensitive Approach to Detect Structural Changes in Collagen Fibers Treated with Surfactants
2019; 35 (24): 7848-7857
Optimizing protocols so that the structure of the collagen fibers in the extracellular matrix remains intact during the decellularization process requires techniques with high structural sensitivity, especially for the surface region of the collagen fibers. Here, we demonstrate that vibrational sum-frequency scattering (SFS) spectroscopy in the protein-specific amide I region provides vibrational spectra and scattering patterns characteristic of protein fiber networks self-assembled in vitro from collagen type I, which are kept in aqueous environments during the analysis. At scattering angles away from the phase-matched direction, the relative strengths of various polarization combinations are highly reproducible, and changes in their ratios can be followed in real time during exposure to sodium dodecyl sulfate surfactant solutions. For the fibers in this work, a scattering angle of about 22° provided specificity for the surface region of the fibers, as it allowed monitoring of immediate structural changes during the surfactant exposure. With further development, we hypothesize that the information from the SFS characterization of collagen fibers may complement information from other techniques with sensitivity to the overall structure, such as second-harmonic generation imaging and infrared spectroscopy, and provide a more complete understanding of fiber molecular structures and interactions during exposure to various environments and conditions.
View details for DOI 10.1021/acs.langmuir.9b00412
View details for Web of Science ID 000472682600028
View details for PubMedID 31117724
View details for PubMedCentralID PMC6648693
- Stark Tuning Rates of Organic Carbonates Used in Electrochemical Energy Storage Devices JOURNAL OF PHYSICAL CHEMISTRY C 2019; 123 (18): 11484–92
- Operando Sum-Frequency Generation Detection of Electrolyte Redox Products at Active Si Nanoparticle Li-Ion Battery Interfaces CHEMISTRY OF MATERIALS 2018; 30 (4): 1239-1248
Nonlinear Optical Methods for Characterization of Molecular Structure and Surface Chemistry
Topics in Catalysis
2018; 61 (9-11): 1101-1124
View details for DOI 10.1007/s11244 018-0924-3
Label-free imaging of amyloids using their intrinsic linear and nonlinear optical properties
BIOMEDICAL OPTICS EXPRESS
2017; 8 (2): 743-756
The optical properties of amyloid fibers are often distinct from those of the source protein in its non-fibrillar form. These differences can be utilized for label-free imaging or characterization of such structures, which is particularly important for understanding amyloid fiber related diseases such as Alzheimer's and Parkinson's disease. We demonstrate that two amyloid forming proteins, insulin and β-lactoglobulin (β-LG), show intrinsic fluorescence with emission spectra that are dependent on the excitation wavelength. Additionally, a new fluorescence peak at about 430 nm emerges for β-LG in its amyloid state. The shift in emission wavelength is related to the red edge excitation shift (REES), whereas the additional fluorescence peak is likely associated with charge delocalization along the fiber backbone. Furthermore, the spherulitic amyloid plaque-like superstructures formed from the respective proteins were imaged label-free with confocal fluorescence, multiphoton excitation fluorescence (MPEF), and second-harmonic generation (SHG) microscopy. The latter two techniques in particular yield images with a high contrast between the amyloid fiber regions and the core of amorphously structured protein. Strong multiphoton absorption (MPA) for the amyloid fibers is a likely contributor to the observed contrast in the MPEF images. The crystalline fibrillar region provides even higher contrast in the SHG images, due to the inherently ordered non-centrosymmetric structure of the fibers together with their non-isotropic arrangement. Finally, we show that MPEF from the insulin spherulites exhibits a spectral dependence on the excitation wavelength. This behavior is consistent with the REES phenomenon, which we hypothesize is the origin of this observation. The presented results suggest that amyloid deposits can be identified and structurally characterized based on their intrinsic optical properties, which is important for probe-less and label-free identification and characterization of amyloid fibers in vitro and in complex biological samples.
View details for DOI 10.1364/BOE.8.000743
View details for Web of Science ID 000394182100021
View details for PubMedID 28270981
View details for PubMedCentralID PMC5330564
Experimental design and analysis of activators regenerated by electron transfer-atom transfer radical polymerization experimental conditions for grafting sodium styrene sulfonate from titanium substrates
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
2015; 33 (5): 05E131
A 24 factorial design was used to optimize the activators regenerated by electron transfer-atom transfer radical polymerization (ARGET-ATRP) grafting of sodium styrene sulfonate (NaSS) films from trichlorosilane/10-undecen-1-yl 2-bromo-2-methylpropionate (ester ClSi) functionalized titanium substrates. The process variables explored were: (1) ATRP initiator surface functionalization reaction time; (2) grafting reaction time; (3) CuBr2 concentration; and (4) reducing agent (vitamin C) concentration. All samples were characterized using x-ray photoelectron spectroscopy (XPS). Two statistical methods were used to analyze the results: (1) analysis of variance with [Formula: see text], using average [Formula: see text] XPS atomic percent as the response; and (2) principal component analysis using a peak list compiled from all the XPS composition results. Through this analysis combined with follow-up studies, the following conclusions are reached: (1) ATRP-initiator surface functionalization reaction times have no discernable effect on NaSS film quality; (2) minimum (≤24 h for this system) grafting reaction times should be used on titanium substrates since NaSS film quality decreased and variability increased with increasing reaction times; (3) minimum (≤0.5 mg cm-2 for this system) CuBr2 concentrations should be used to graft thicker NaSS films; and (4) no deleterious effects were detected with increasing vitamin C concentration.
View details for DOI 10.1116/1.4929506
View details for Web of Science ID 000361229000031
View details for PubMedID 26396463
View details for PubMedCentralID PMC4570287
Electronic polymers in lipid membranes
2015; 5: 11242
Electrical interfaces between biological cells and man-made electrical devices exist in many forms, but it remains a challenge to bridge the different mechanical and chemical environments of electronic conductors (metals, semiconductors) and biosystems. Here we demonstrate soft electrical interfaces, by integrating the metallic polymer PEDOT-S into lipid membranes. By preparing complexes between alkyl-ammonium salts and PEDOT-S we were able to integrate PEDOT-S into both liposomes and in lipid bilayers on solid surfaces. This is a step towards efficient electronic conduction within lipid membranes. We also demonstrate that the PEDOT-S@alkyl-ammonium:lipid hybrid structures created in this work affect ion channels in the membrane of Xenopus oocytes, which shows the possibility to access and control cell membrane structures with conductive polyelectrolytes.
View details for DOI 10.1038/srep11242
View details for Web of Science ID 000356090400002
View details for PubMedID 26059023
View details for PubMedCentralID PMC4462020
Vibrational Sum-Frequency Scattering for Detailed Studies of Collagen Fibers in Aqueous Environments
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2014; 136 (39): 13598-13601
Protein fibers play a crucial role in many disease related phenomena and biological systems. A structural analysis of fibrous proteins often requires labeling approaches or disruptive sample preparation while it lacks chemical specificity. Here we demonstrate that the technique of vibrational sum-frequency scattering (SFS) provides a label-free pathway for the chemical and structural analysis of protein fibers in solution. By examining collagen, the most abundant protein in mammals, we demonstrate that the SFS signal of fibers can be detected in the NH, CH stretching and bending, and amide I regions. SFS spectra were found to depend on the scattering angle, which implies the possibility to selectively probe various features of the fibers. The fitting of the data and maximum entropy method analysis revealed a different phase for side-chains and carbonyl contributions, which helps to identify these otherwise overlapping spectral peaks and provides the possibility to perform orientational analysis. Our findings suggest that SFS allows for the greater understanding of protein fibers in solution, which is important when, for example, designing scaffolds in tissue engineering or developing cures for diseases associated with protein fibers.
View details for DOI 10.1021/ja508190d
View details for Web of Science ID 000342608800033
View details for PubMedID 25225785
View details for PubMedCentralID PMC4183644