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Josh Smith, Kayla G Sprenger, Rick Liao, Andrea Joseph, Elizabeth Nance, Jim Pfaendtner
Enzymes play a critical role in many applications in biology and medicine as potential therapeutics. One specific area of interest is enzyme encapsulation in polymer nanostructures, which have applications in drug delivery and catalysis. A detailed understanding of the mechanisms governing protein/polymer interactions is crucial for optimizing the performance of these complex systems for different applications. Using a combined computational and experimental approach, this study aims to quantify the relative importance of molecular and mesoscale driving forces to protein release from polymeric nanoparticles...
May 19, 2017: Biointerphases
Luisa A Scudeller, Selvi Srinivasan, Alexandre M Rossi, Patrick S Stayton, Gary P Drobny, David G Castner
Adsorption isotherms, circular dichroism (CD) spectroscopy, x-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used to investigate the adsorption of human osteocalcin (hOC) and decarboxylated (i.e., Gla converted back to Glu) hOC (dhOC) onto various calcium phosphate surfaces as well as silica surfaces. The adsorption isotherms and XPS nitrogen signals were used to track the amount of adsorbed hOC and dhOC. The intensities of key ToF-SIMS amino acid fragments were used to assess changes in the structure of adsorbed hOC and dhOC...
May 18, 2017: Biointerphases
Tigran M Abramyan, David L Hyde-Volpe, Steven J Stuart, Robert A Latour
The use of standard molecular dynamics simulation methods to predict the interactions of a protein with a material surface have the inherent limitations of lacking the ability to determine the most likely conformations and orientations of the adsorbed protein on the surface and to determine the level of convergence attained by the simulation. In addition, standard mixing rules are typically applied to combine the nonbonded force field parameters of the solution and solid phases the system to represent interfacial behavior without validation...
May 17, 2017: Biointerphases
James W Bauer, Li-Chong Xu, Erwin A Vogler, Christopher A Siedlecki
Studies of the activation of FXII in both platelet poor plasma and in neat buffer solutions were undertaken for a series of mixed thiol self-assembled monolayers spanning a broad range of water wettability. A wide spectrum of carboxyl/methyl-, hydroxyl/methyl-, and amine/methyl-thiol modified surfaces were prepared, characterized, and then utilized as the procoagulant materials in a series of FXII activation studies. X-ray photoelectron spectroscopy was utilized to verify the sample surface's thiol composition and contact angles measured to determine the sample surface's wettability...
May 17, 2017: Biointerphases
Rebecca Eells, Marilia Barros, Kerry M Scott, Ioannis Karageorgos, Frank Heinrich, Mathias Lösche
The structural characterization of peripheral membrane proteins represents a tremendous challenge in structural biology due to their transient interaction with the membrane and the potential multitude of protein conformations during this interaction. Neutron reflectometry is uniquely suited to address this problem because of its ability to structurally characterize biological model systems nondestructively and under biomimetic conditions that retain full protein functionality. Being sensitive to only the membrane-bound fraction of a water-soluble peripheral protein, neutron reflectometry obtains a low-resolution average structure of the protein-membrane complex that is further refined using integrative modeling strategies...
May 16, 2017: Biointerphases
Xia Han, Hsiang-Chieh Hung, Priyesh Jain, Fang Sun, Xuewei Xu, Wei Yang, Tao Bai, Shaoyi Jiang
Terminal sterilization of hydrogel-based biomaterials is crucial for their clinically relevant applications. The authors synthesized nonfouling zwitterionic hydrogels consisting of carboxybetaine (CB) acrylamide monomer and a carboxybetaine dimethacrylate crosslinker. The mechanical and biological stability of nonfouling hydrogels were investigated using three main terminal sterilization techniques, i.e., steam autoclave, ethylene oxide gas, and gamma irradiation. It was found that CB hydrogels are very stable at high temperature and pressure and in oxidative gas environments without changing their stress, modulus, and nonfouling properties...
May 16, 2017: Biointerphases
Katherine D Krause, Sandra Roy, Dennis K Hore
Atomistic molecular dynamics simulations were used to study the influence of interfacial water on the orientation and conformation of a facewise amphipathic α-helical peptide adsorbed to hydrophilic and hydrophobic substrates. Water behavior beneath the peptide adsorbed to a hydrophilic surface was observed to vary with the height of the peptide above the surface. In general, the orientation of water close to the peptide (with the oxygen atom pointing up toward the peptide) was complementary to that observed near the hydrophilic surface in the absence of peptide...
May 15, 2017: Biointerphases
David C Florian, Michael A Melia, Fritz W Steuer, Bruce F Briglia, Michael K Purzycki, John R Scully, James M Fitz-Gerald
As a lightweight metal with mechanical properties similar to natural bone, Mg and its alloys are great prospects for biodegradable, load bearing implants. However, rapid degradation and H2 gas production in physiological media has prevented widespread use of Mg alloys. Surface heterogeneities in the form of intermetallic particles dominate the corrosion response. This research shows that surface homogenization significantly improved the biological corrosion response observed during immersion in simulated body fluid (SBF)...
May 11, 2017: Biointerphases
Justin P Jahnke, Austin M Smith, Nicole E Zander, Victoria Wiedorn, Kenneth E Strawhecker, Jessica L Terrell, Dimitra N Stratis-Cullum, Xuanhong Cheng
The potential advantages of cell-based biohybrid devices over conventional nonliving systems drive the interest to control the behavior of the underlying biological cells in microdevices. Here, the authors studied how shear influenced the geometry and elongation of fimbriated filaments on affinity substrates. The cells were engineered to express FimH, which binds to mannose with a high affinity. A microfluidic channel was functionalized with RNAse B, which is rich in mannose residues, and the device was used to control the hydrodynamic force on live Escherichia coli under filamentous growth...
May 10, 2017: Biointerphases
Mikkel Vestergaard, Mikkel Christensen, Sara K Hansen, Dennis Grønvall, Lisbeth R Kjølbye, Thomas Vosegaard, Birgit Schiøtt
Many antimicrobial peptides function by forming pores in the plasma membrane of the target cells. Intriguingly, some of these peptides are very short, and thus, it is not known how they can span the membrane, or whether other mechanisms of cell disruption are dominant. Here, the conformation and orientation of the 14-residue peptaibol SPF-5506-A4 (SPF) are investigated in lipid environments by atomistic and coarse grained molecular dynamics (MD) simulations, circular dichroism, and nuclear magnetic resonance (NMR) experiments...
May 5, 2017: Biointerphases
Thaddeus W Golbek, Johannes Franz, J Elliott Fowler, Karl F Schilke, Tobias Weidner, Joe E Baio
Cationic amphiphilic peptides have been engineered to target both Gram-positive and Gram-negative bacteria while avoiding damage to other cell types. However, the exact mechanism of how these peptides target, bind, and disrupt bacterial cell membranes is not understood. One specific peptide that has been engineered to selectively capture bacteria is WLBU2 (sequence: RRWVRRVRRWVRRVVRVVRRWVRR). It has been suggested that WLBU2 activity stems from the fact that when interacting with bacterial cell membranes the peptide assumes an α-helical structure and inserts itself into the membrane...
May 5, 2017: Biointerphases
Jaroslav Kristof, Hideto Miyamoto, An Nhat Tran, Marius Blajan, Kazuo Shimizu
A study of the transdermal delivery of Cyclosporine A by atmospheric plasma irradiation was realized on the epidermal layer of the Hairless Yucatan micropig. Drug flux and the amount of drug penetrated through the skin were determined by a Franz cell diffusion experiment. After treatment of the skin by atmospheric plasma jet or microplasma dielectric barrier discharge, an increase in the permeability of the skin was observed. The authors did not observe drug penetration for samples that were not treated with plasma...
May 4, 2017: Biointerphases
Patrick N Charron, Sarah E Blatt, Canaan McKenzie, Rachael A Oldinski
Intervertebral disk degeneration is one of the most significant contributors to low back pain. Thus, there is significant interest in designing new treatments and nucleus pulposus (NP) tissue replacements. Herein, the authors propose a biosynthetic material, comprised of a polyvinyl alcohol (PVA) and gelatin theta-gel, as an acellular NP tissue replacement. Theta-gels form during the solidification of PVA and gelatin (phase I), and the phase separation of a disklike short-chain polyethylene glycol (PEG, phase II)...
May 3, 2017: Biointerphases
Brittany E Givens, Nina D Diklich, Jennifer Fiegel, Vicki H Grassian
Bovine serum albumin (BSA) adsorbed on amorphous silicon dioxide (SiO2) nanoparticles was studied as a function of pH across the range of 2 to 8. Aggregation, surface charge, surface coverage, and protein structure were investigated over this entire pH range. SiO2 nanoparticle aggregation is found to depend upon pH and differs in the presence of adsorbed BSA. For SiO2 nanoparticles truncated with hydroxyl groups, the largest aggregates were observed at pH 3, close to the isoelectric point of SiO2 nanoparticles, whereas for SiO2 nanoparticles with adsorbed BSA, the aggregate size was the greatest at pH 3...
May 3, 2017: Biointerphases
Håkan Nygren, Narmin Bigdeli, Lars Ilver, Per Malmberg
The different capacities of magnesium in the metallic form (Mg-metal) and magnesium oxide (MgO) to stimulate bone healing are possible clues in the search for products that may promote bone healing. Since both Mg-metal and MgO can be assumed to release comparable amounts of Mg(2+) ions during their reactions in the tissue where they have been implanted, it is of some importance to follow this process and analyze the resulting mineral formation in the tissue at the implantation site. Implants of MgO were inserted into rat tibia, and the bone healing was compared with sham-operated controls...
May 2, 2017: Biointerphases
Andreas Skallberg, Caroline Brommesson, Kajsa Uvdal
Combined photoemission electron microscopy (PEEM) and imaging x-ray photoelectron spectroscopy (XPS), i.e., electron spectroscopy for chemical analysis in the nanoregion, has been used for surface characterization of bio-relevant and biological samples. In the first example, the authors prepared a gold patterned silicon substrate, stepwise surface modified by self-assembled monolayers followed by quantum dot (QDot) specific linking and investigated by means of work function mapping and elemental imaging in the submicrometer range...
May 2, 2017: Biointerphases
Thomas E Winkler, Sarah L Lederer, Eunkyoung Kim, Hadar Ben-Yoav, Deanna L Kelly, Gregory F Payne, Reza Ghodssi
Selectivity presents a crucial challenge in direct electrochemical sensing. One example is schizophrenia treatment monitoring of the redox-active antipsychotic clozapine. To accurately assess efficacy, differentiation from its metabolite norclozapine-similar in structure and redox potential-is critical. Here, the authors leverage biomaterials integration to study, and effect changes in, diffusion and electron transfer kinetics of these compounds. Specifically, the authors employ a catechol-modified chitosan film, which the authors have previously presented as the first electrochemical detection mechanism capable of quantifying clozapine directly in clinical serum...
May 1, 2017: Biointerphases
Kenan P Fears, Corey T Love, Delbert E Day
Biomaterials with nanostructured surfaces influence cellular response in a significantly different, and often beneficial, manner compared to materials with coarser features. Hydroxyapatite [HA, Ca10(PO4)6(OH)2] and strontium-apatite [Sr10(PO4)6(OH)2] microspheres that present nanotopographies similar to biological apatites were incubated in albumin solutions, at physiological conditions (40 mg ml(-1); 37 °C), for up to 72 h. Electronic and vibrational circular dichroism spectroscopies revealed spectral signatures characteristic of stacked β-sheet regions in higher ordered structures (e...
May 1, 2017: Biointerphases
Colin D Eichinger, Vladimir Hlady
As platelets encounter damaged vessels or biomaterials, they interact with a complex milieu of surface-bound agonists, from exposed subendothelium to adsorbed plasma proteins. It has been shown that an upstream, surface-immobilized agonist is capable of priming platelets for enhanced adhesion downstream. In this study, binary agonists were integrated into the upstream position of flow cells and the platelet priming response was measured by downstream adhesion in flowing whole blood. A nonadditive response was observed in which platelets transiently exposed to two agonists exhibited greater activation and downstream adhesion than that from the sum of either agonist alone...
April 28, 2017: Biointerphases
Abdullah Alghunaim, Eric T Brink, Eli Y Newby, Bi-Min Zhang Newby
Silane coupling agents are commonly employed to link an organic polymer to an inorganic substrate. One of the widely utilized coupling agents is 3-aminopropyltriethoxy silane (APTES). In this study, the authors investigated the ability of APTES to retain thermo-responsive poly(N-isopropylacrylamide) (pNIPAAm) on hydroxylated surfaces such as glass. For comparison purposes, the authors also evaluated the retention behaviors of (1) polystyrene, which likely has weaker van der Waals interactions and acid-base interactions (contributed by hydrogen-bonding) with APTES, on APTES as well as (2) pNIPAAm on two other silane coupling agents, which have similar structures to APTES, but exhibit less interaction with pNIPAAm...
April 27, 2017: Biointerphases
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