This document discusses the development of biomimetic materials through the continuous processing and surface modification of polycaprolactone (PCL) nanofibers. Specifically:
1) The goal is to introduce multiple orthogonal chemical modifications onto nanofibers to produce a surface capable of attaching various bioactive cues like peptides.
2) A coextrusion and photochemical modification procedure is used to introduce and spatially control functional groups on the fibers.
3) Initial results show the substrate with dual RGD and OGP peptide modifications is sufficient to induce bone cell differentiation and adhesion, demonstrating the potential of these biomimetic materials.
Network polymers derived from the integration of flexible organic polymers an...Berkay AKKOÇ
Network polymers derived from the integration of flexible organic polymers and rigid metal organic frameworks. My class notes about a kind of inorganic polymer. Review.
Design and Simulation of Photonic Crystal Fiber with Low Dispersion Coefficie...IJAEMSJORNAL
In this paper, a hexagonal solid state photonic crystal fiber at frequency 10 THz is presented. First, by finding the main conductive model and its dispersion rate to evaluate dispersion changes based on the fixed changes of fiber network in the main mode with the goal of achieving the lowest dispersion rate. In the next section, dispersion variations are measured and evaluated based on changes in the size of the radius of the cavities of the photonic crystal fiber area. Then the fiber-forming cavities of the fiber region have become elliptical geometry, and the size of the disintegration has been discussed for this change. Finally, by changing the refractive index of the fiber substrate region, the size of the disintegration has been investigated. For the geometries of all the steps that have the least disintegration, an optimized structure is obtained. In this way, the proposed structure has a dispersion rate of -75×〖10〗^(-3) ps/(nm km), which is a good fit for similar designs.
Photocatalytic Mechanism Control and Study of Carrier Dynamics in CdS@C3N5 Co...Pawan Kumar
We present a potential solution to the problem of extraction of photogenerated holes from CdS nanocrystals and nanowires. The nanosheet form of C3N5 is a low-band-gap (Eg = 2.03 eV), azo-linked graphenic carbon nitride framework formed by the polymerization of melem hydrazine (MHP). C3N5 nanosheets were either wrapped around CdS nanorods (NRs) following the synthesis of pristine chalcogenide or intercalated among them by an in situ synthesis protocol to form two kinds of heterostructures, CdS-MHP and CdS-MHPINS, respectively. CdS-MHP improved the photocatalytic degradation rate of 4-nitrophenol by nearly an order of magnitude in comparison to bare CdS NRs. CdS-MHP also enhanced the sunlight-driven photocatalytic activity of bare CdS NWs for the decolorization of rhodamine B (RhB) by a remarkable 300% through the improved extraction and utilization of photogenerated holes due to surface passivation. More interestingly, CdS-MHP provided reaction pathway control over RhB degradation. In the absence of scavengers, CdS-MHP degraded RhB through the N-deethylation pathway. When either hole scavenger or electron scavenger was added to the RhB solution, the photocatalytic activity of CdS-MHP remained mostly unchanged, while the degradation mechanism shifted to the chromophore cleavage (cycloreversion) pathway. We investigated the optoelectronic properties of CdS-C3N5 heterojunctions using density functional theory (DFT) simulations, finite difference time domain (FDTD) simulations, time-resolved terahertz spectroscopy (TRTS), and photoconductivity measurements. TRTS indicated high carrier mobilities >450 cm2 V–1 s–1 and carrier relaxation times >60 ps for CdS-MHP, while CdS-MHPINS exhibited much lower mobilities <150 cm2 V–1 s–1 and short carrier relaxation times <20 ps. Hysteresis in the photoconductive J–V characteristics of CdS NWs disappeared in CdS-MHP, confirming surface passivation. Dispersion-corrected DFT simulations indicated a delocalized HOMO and a LUMO localized on C3N5 in CdS-MHP. C3N5, with its extended π-conjugation and low band gap, can function as a shuttle to extract carriers and excitons in nanostructured heterojunctions, and enhance performance in optoelectronic devices. Our results demonstrate how carrier dynamics in core–shell heterostructures can be manipulated to achieve control over the reaction mechanism in photocatalysis.
Network polymers derived from the integration of flexible organic polymers an...Berkay AKKOÇ
Network polymers derived from the integration of flexible organic polymers and rigid metal organic frameworks. My class notes about a kind of inorganic polymer. Review.
Design and Simulation of Photonic Crystal Fiber with Low Dispersion Coefficie...IJAEMSJORNAL
In this paper, a hexagonal solid state photonic crystal fiber at frequency 10 THz is presented. First, by finding the main conductive model and its dispersion rate to evaluate dispersion changes based on the fixed changes of fiber network in the main mode with the goal of achieving the lowest dispersion rate. In the next section, dispersion variations are measured and evaluated based on changes in the size of the radius of the cavities of the photonic crystal fiber area. Then the fiber-forming cavities of the fiber region have become elliptical geometry, and the size of the disintegration has been discussed for this change. Finally, by changing the refractive index of the fiber substrate region, the size of the disintegration has been investigated. For the geometries of all the steps that have the least disintegration, an optimized structure is obtained. In this way, the proposed structure has a dispersion rate of -75×〖10〗^(-3) ps/(nm km), which is a good fit for similar designs.
Photocatalytic Mechanism Control and Study of Carrier Dynamics in CdS@C3N5 Co...Pawan Kumar
We present a potential solution to the problem of extraction of photogenerated holes from CdS nanocrystals and nanowires. The nanosheet form of C3N5 is a low-band-gap (Eg = 2.03 eV), azo-linked graphenic carbon nitride framework formed by the polymerization of melem hydrazine (MHP). C3N5 nanosheets were either wrapped around CdS nanorods (NRs) following the synthesis of pristine chalcogenide or intercalated among them by an in situ synthesis protocol to form two kinds of heterostructures, CdS-MHP and CdS-MHPINS, respectively. CdS-MHP improved the photocatalytic degradation rate of 4-nitrophenol by nearly an order of magnitude in comparison to bare CdS NRs. CdS-MHP also enhanced the sunlight-driven photocatalytic activity of bare CdS NWs for the decolorization of rhodamine B (RhB) by a remarkable 300% through the improved extraction and utilization of photogenerated holes due to surface passivation. More interestingly, CdS-MHP provided reaction pathway control over RhB degradation. In the absence of scavengers, CdS-MHP degraded RhB through the N-deethylation pathway. When either hole scavenger or electron scavenger was added to the RhB solution, the photocatalytic activity of CdS-MHP remained mostly unchanged, while the degradation mechanism shifted to the chromophore cleavage (cycloreversion) pathway. We investigated the optoelectronic properties of CdS-C3N5 heterojunctions using density functional theory (DFT) simulations, finite difference time domain (FDTD) simulations, time-resolved terahertz spectroscopy (TRTS), and photoconductivity measurements. TRTS indicated high carrier mobilities >450 cm2 V–1 s–1 and carrier relaxation times >60 ps for CdS-MHP, while CdS-MHPINS exhibited much lower mobilities <150 cm2 V–1 s–1 and short carrier relaxation times <20 ps. Hysteresis in the photoconductive J–V characteristics of CdS NWs disappeared in CdS-MHP, confirming surface passivation. Dispersion-corrected DFT simulations indicated a delocalized HOMO and a LUMO localized on C3N5 in CdS-MHP. C3N5, with its extended π-conjugation and low band gap, can function as a shuttle to extract carriers and excitons in nanostructured heterojunctions, and enhance performance in optoelectronic devices. Our results demonstrate how carrier dynamics in core–shell heterostructures can be manipulated to achieve control over the reaction mechanism in photocatalysis.
Role of Environmental Factors on the Structure and Spectroscopic ResponseAngela Mammana
We have explored the utility,
strength, and limitation of throughspace
exciton-coupled circular dichroism
in determination of the secondary
structure of optically active chromophoric
nanoarrays using the example of
end-capped porphyrin– and metalloporphyrin–
oligodeoxynucleotide conjugates.
We put special emphasis on the
explanation of the origin and significance
of the distinctive multiple bands
in the CD spectra (trisignate and tetrasignate
CD bands). Such CD profiles
are often observed in chiral aggregates
or multichromophoric arrays but have
never before been studied in detail. We
found that variation of temperature
and ionic strength has a profound
effect on the geometry of the porphyrin–
DNA conjugates and thus the
nature of electronic interactions. At
lower temperatures and in the absence
of NaCl all three 5’-DNA–porphyrin
conjugates display negative bisignate
CD exciton couplets of variable intensity
in the Soret region resulting from
through-space interaction between the
electric transition dipole moments of
the two end-capped porphyrins. As the
temperature is raised these exciton
couplets are transformed into single
positive bands originating from the
porphyrin–single-strand DNA interactions.
At higher ionic strengths and low
temperatures, multisignate CD bands
are observed in the porphyrin Soret
region. These CD signature bands originate
from a combination of intermolecular,
end-to-end porphyrin–porphyrin
stacking between duplexes and porphyrin–
DNA interactions. The intermolecular
aggregation was confirmed
by fluorescence and absorption spectroscopy
and resonance light scattering.
DeVoe theoretical CD calculations, in
conjunction with molecular dynamics
simulations and Monte Carlo conformational
searches, were used to mimic
the observed bisignate exciton-coupled
CD spectra as well as multiple CD
bands. Calculations correctly predicted
the sign and shape of the experimentally
observed CD spectra. These studies
reveal that the exciton-coupled circular
dichroism is a very useful technique for
the determination of the structure of
optically active arrays.
Peter Budd (University of Manchester) - Organic Mixed Matrix Membrane Technologies (ORGMENT) for Post-Combustion CO2 Capture - UKCCSRC Cranfield Biannual 21-22 April 2015
Protein structure determination from hybrid NMR data.Mark Berjanskii
Protein structure determination from hybrid NMR data. Presentation is related to: biochemistry, bioinformatics, biology, biophysics, mark berjanskii, molecular biology, molecular dynamics, molecular modeling, nmr spectroscopy, protein nmr, public speaking, python programming, sparse data, structural biology, structure determination, teaching, web design, web development, web programming, Wishart group, hybrid data, SAXS, WAXS, X-ray crystallography, FRET, CryoEM, EPR, Mass Spectrometry
Dr. Patrick Bradshaw presents an overview of his program, Human Performance and Biosystems, at the AFOSR 2013 Spring Review. At this review, Program Officers from AFOSR Technical Divisions will present briefings that highlight basic research programs beneficial to the Air Force.
Role of Environmental Factors on the Structure and Spectroscopic ResponseAngela Mammana
We have explored the utility,
strength, and limitation of throughspace
exciton-coupled circular dichroism
in determination of the secondary
structure of optically active chromophoric
nanoarrays using the example of
end-capped porphyrin– and metalloporphyrin–
oligodeoxynucleotide conjugates.
We put special emphasis on the
explanation of the origin and significance
of the distinctive multiple bands
in the CD spectra (trisignate and tetrasignate
CD bands). Such CD profiles
are often observed in chiral aggregates
or multichromophoric arrays but have
never before been studied in detail. We
found that variation of temperature
and ionic strength has a profound
effect on the geometry of the porphyrin–
DNA conjugates and thus the
nature of electronic interactions. At
lower temperatures and in the absence
of NaCl all three 5’-DNA–porphyrin
conjugates display negative bisignate
CD exciton couplets of variable intensity
in the Soret region resulting from
through-space interaction between the
electric transition dipole moments of
the two end-capped porphyrins. As the
temperature is raised these exciton
couplets are transformed into single
positive bands originating from the
porphyrin–single-strand DNA interactions.
At higher ionic strengths and low
temperatures, multisignate CD bands
are observed in the porphyrin Soret
region. These CD signature bands originate
from a combination of intermolecular,
end-to-end porphyrin–porphyrin
stacking between duplexes and porphyrin–
DNA interactions. The intermolecular
aggregation was confirmed
by fluorescence and absorption spectroscopy
and resonance light scattering.
DeVoe theoretical CD calculations, in
conjunction with molecular dynamics
simulations and Monte Carlo conformational
searches, were used to mimic
the observed bisignate exciton-coupled
CD spectra as well as multiple CD
bands. Calculations correctly predicted
the sign and shape of the experimentally
observed CD spectra. These studies
reveal that the exciton-coupled circular
dichroism is a very useful technique for
the determination of the structure of
optically active arrays.
Peter Budd (University of Manchester) - Organic Mixed Matrix Membrane Technologies (ORGMENT) for Post-Combustion CO2 Capture - UKCCSRC Cranfield Biannual 21-22 April 2015
Protein structure determination from hybrid NMR data.Mark Berjanskii
Protein structure determination from hybrid NMR data. Presentation is related to: biochemistry, bioinformatics, biology, biophysics, mark berjanskii, molecular biology, molecular dynamics, molecular modeling, nmr spectroscopy, protein nmr, public speaking, python programming, sparse data, structural biology, structure determination, teaching, web design, web development, web programming, Wishart group, hybrid data, SAXS, WAXS, X-ray crystallography, FRET, CryoEM, EPR, Mass Spectrometry
Dr. Patrick Bradshaw presents an overview of his program, Human Performance and Biosystems, at the AFOSR 2013 Spring Review. At this review, Program Officers from AFOSR Technical Divisions will present briefings that highlight basic research programs beneficial to the Air Force.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
1. Extracellular matrix (ECM) inspired biomimetic materials
The extra cellular matrix is a complex environment that
provides chemical and physical support cells. A key component
of biologically functional scaffolds is the need to introduce
chemical or biochemical cues that allow for cellular adhesion
proliferation, and differentiation, In biological systems, multiple
cues are needed to direct cell biology.
Continuous Processing of PCLNanofibers through Extrusion
Multifunctional and spatially controlled
bioconjugation to melt coextruded
nanofibers
Abigail A. Advincula1, Si-Eun Kim1, Emily C. Harker1, Jon Pokorski1*
1Department of Macromolecular Science & Engineering, Case Western Reserve University
2100 Adelbert Road, Cleveland, Ohio,d 44106
jon.pokorski@case.edu
Our goal for this project is to introduce multiple orthogonal
chemical modifications onto nanofibers in order to produce a
surface capable of attaching various bioactive cues.
We have recently reported a new class of fibrous
biomaterials using coextrusion and a photochemical
modification procedure to introduce functional groups onto the
fibers.
This project extends our methodology to control surface
modification density, describe methods to synthesize
multifunctional fibers, and provide methods to spatially control
functional group modification.
We investigate the effect of fiber modification with multiple
cell-responsive peptides, the RGD sequence and osteogenic
growth peptide (OGP), on substrates for osteoblast
differentiation.
Goal
Results
Introduction
Acknowledgements
The bioavailability of multiple peptides by our substrate
was sufficient to induce both bone differentiation and
cellular adhesion.
Utilizing multiple ‘click’ types of chemistry allows for the
covalent attachment of several different types of
molecules. This is a useful strategy if the CuAAC
reaction is not appropriate or if orthogonal chemistry may
be needed.
We report a simple method for surface modification that
enables the manipulation of surface concentration based
on UV fluence.
We have demonstrated control over modulus, fiber
alignment, and the deposition of multiple chemical
functionalities in a spatially controlled manner.
Results
Experimental
Conclusions
Synthetic scheme for multiple functional fiber variants
Oxime coupling of doxorubicin
Coextruded SEM images of coextruded PCL fibers
• Produce 1,024 (256×4) layer system with PEO surface layer
No organic solvent
Aligned fibers
Scalable
High Surface Area
(A) Digital images of fibers functionalized with AF488
under varying UV irradiation times. (B) UV-Vis spectra
of AF488 functionalized fibers following dissolution.
Dual gradient modification results Fiber modification with AF488
(A) Bifunctional gradient modification scheme. (B)
Fluorescent images of PCL bundles. Top: red channel to
visualize TAMARA, Middle: green channel to visualize
AF488, Bottom: overlaid green and red channels.
(A) Schematic for reversible oxime coupling of DOX. (B) ATR
FT-IR spectra of PCL (black) and PCL-Alkoxyamine (red). (C)
Doxorubicin kinetic release profile, measured using UV-Vis
absorbance at 490 nm in pH 4.5 MES buffer in increments of 10
minutes.
Relative ALP activity for peptide modified substrates
XPS spectra of peptide modified fiber scaffolds
Dual indicates modification with both OGP and RGD.
I would like to thank Professor Jonathan Pokorski for his
guidance on this project. I would also like to thank Si-Eun
Kim and Emily Harker for their help with sample
preparation and characterization.
Scanning electron micrograph of aligned fibers
following PEO dissolution. Scale bar – 10 μm.