Combinatorial Surface Research Articles

Green Light Photoelectrocatalysis with Sulfur-Doped Carbon Nitride: Using Triazole-Purpald for Enhanced Benzylamine Oxidation and Oxygen Evolution Reactions.

Materials dictate carbon neutralindustrialchemicalprocesses. Visible-light photoelectrocatalysts from abundant resources will play a key role in exploiting solar irradiation. Anionic doping via pre-organization of precursors and further co-polymerization creates tuneable semiconductors. Triazole derivative-purpald, an unexplored precursor with sulfur (S) container, combined in different initial ratios with melamine during one solid-state polycondensation with two thermal steps yields hybrid S-doped carbon nitrides (C3 N4 ). The series of S-doped/C3 N4 -based materials show enhanced optical, electronic, structural, textural, and morphological properties and exhibit higher performance in organic benzylamine photooxidation, oxygen evolution, and similar energy storage (capacitor brief investigation). 50M-50P exhibits the highest photooxidation conversion (84±3%) of benzylamine to imine at 535nm - green light for 48h, due to a discrete shoulder (≈700)nm, high sulfur content, preservation of crystal size, new intraband energy states, structural defects by layer distortion, and 10-16nm pores with arbitrary depth. This work innovates by studying the concomitant relationships between: 1) the precursor decomposition while C3 N4 is formed, 2) the insertion of Simpurities, 3) the S-doped C3 N4 property-activity relationships, and 4) combinatorial surface, bulk, structural, optical, and electronic characterization analysis. This work contributes to the development of disordered long-visible-lightphotocatalysts for solar energy conversion and storage.

A green strategy to produce potential substitute resource for bear bile using engineered Saccharomyces cerevisiae

BackgroundBear bile powder is a precious natural material characterized by high content of tauroursodeoxycholic acid (TUDCA) at a ratio of 1.00–1.50 to taurochenodeoxycholic acid (TCDCA).ResultsIn this study, we use the crude enzymes from engineered Saccharomyces cerevisiae to directionally convert TCDCA from chicken bile powder to TUDCA at the committed ratio in vitro. This S. cerevisiae strain was modified with heterologous 7α-hydroxysteroid dehydrogenase (7α-HSDH) and 7β-hydroxysteroid dehydrogenase (7β-HSDH) genes. S. cerevisiae host and HSDH gene combinatorial optimization and response surface methodology was applied to get the best engineered strain and the optimal biotransformation condition, respectively, under which 10.99 ± 0.16 g/L of powder products containing 36.73 ± 6.68% of TUDCA and 28.22 ± 6.05% of TCDCA were obtained using 12.00 g/L of chicken bile powder as substrate.ConclusionThis study provides a healthy and environmentally friendly way to produce potential alternative resource for bear bile powder from cheap and readily available chicken bile powder, and also gives a reference for the green manufacturing of other rare and endangered animal-derived valuable resource.

Thermal Stability of Thiolated DNA SAMs in Buffer: Revealing the Influence of Surface Crystallography and DNA Coverage via In Situ Combinatorial Surface Analysis.

The thermal stability of thiol based DNA SAMs prepared on gold surfaces is an important parameter that is correlated to sensor lifetime. The thermal stability of DNA SAMs was evaluated in aqueous buffer through the use of fluorophore labeled DNA, a single crystal gold bead electrode, and microscopy. The stability of different crystallographic regions on the electrode was studied for thermal treatments up to 95 °C for 90 min. Using a in situ combinatorial surface analytical measurement showed that the crystallography of the underlying gold surface played a significant role, with the square or rectangular lattices (e.g., 110, 100, 210) having the highest stability. Surfaces with hexagonal lattices (e.g., 111, 311, 211) were less stable toward thermal treatments. These crystallographic trends were observed for both high and low coverage DNA SAMs. High coverage DNA SAMs were the most stable, with stability decreasing with decreasing coverage on average. Increasing DNA SAM coverage appears to slow the kinetics of thermal desorption, but the coordination to the underlying surface determined their relative stability. Preparing the DNA SAMs under nominally similar conditions were found to create surfaces that were similar at room temperature, but had significantly different thermal stability. Optimal DNA sensing with these surfaces most often requires low coverage DNA SAMs which results in poor thermal stability, which is predictive of a poor shelf life, making optimization of both parameters challenging. Furthermore, the crystallographically specific results should be taken into account when studying the typically used polycrystalline substrates since the underlying surface crystallography maybe different for different samples. It appears that preparing DNA SAMs with low coverage and significant thermal stability will be challenging using the current SAM preparation procedures.

Multifunctional Biomaterials: Combining Material Modification Strategies for Engineering of Cell-Contacting Surfaces

In the human body, cells in a tissue are exposed to signals derived from their specific extracellular matrix (ECM), such as architectural structure, mechanical properties, and chemical composition (proteins, growth factors). Research on biomaterials in tissue engineering and regenerative medicine aims to recreate such stimuli using engineered materials to induce a specific response of cells at the interface. Although traditional biomaterials design has been mostly limited to varying individual signals, increasing interest has arisen on combining several features in recent years to improve the mimicry of extracellular matrix properties. Tremendous progress in combinatorial surface modification exploiting, for example, topographical features or variations in mechanics combined with biochemical cues has enabled the identification of their key regulatory characteristics on various cell fate decisions. Gradients especially facilitated such research by enabling the investigation of combined continuous changes of different signals. Despite unravelling important synergies for cellular responses, challenges arise in terms of fabrication and characterization of multifunctional engineered materials. This review summarizes recent work on combinatorial surface modifications that aim to control biological responses. Modification and characterization methods for enhanced control over multifunctional material properties are highlighted and discussed. Thereby, this review deepens the understanding and knowledge of biomimetic combinatorial material modification, their challenges but especially their potential.

Rapid Buildup Arrays with Orthogonal Biochemistry Gradients via Light-Induced Thiol-Ene "Click" Chemistry for High-Throughput Screening of Peptide Combinations.

The concept of high-throughput screening sheds new light on fabrication and analysis of materials. Herein, a combinatorial surface-modified platform with biochemical gradients was developed through thiol-ene "click" chemistry by adjusting the intensity of ultraviolet (UV) irradiation. Contact angle, X-ray photoelectron spectroscopy, and ellipsometry measurement results demonstrated that the sulfhydryl molecules including polyethylene glycol and RGD (arginine-glycine-aspartic acid) and REDV (arginine-glutamic acid-aspartic acid-valine) peptides can be directly attached onto alkene-modified substrates, in which the graft density can be well controlled by the intensity of UV irradiation. The multistep attachment of different molecules onto substrates is archived via the multistep UV-initiated thiol-ene "click" reaction. The high-throughput arrays with the gradient density of single ligand and the orthogonal gradient density of two ligands were rapidly fabricated via the one-step UV gradient irradiation and the two-step orthogonal UV gradient-initiated thiol-ene "click" reaction. Endothelial cells (ECs) and smooth muscle cells (SMCs) were cocultured on the array with the orthogonal gradient density of RGD and REDV to screen the peptide combination with high EC selectivity, which is essential for in situ endothelialization during stent implant. From 64, 8 × 8, combinations investigated, a special combinatorial surface representing the really high competitiveness of ECs over SMCs was screened. This platform puts forward a facile, high-throughput method to study the combinatorial variation of biochemical signals to cell behavior.

Computing the Geometric Intersection Number of Curves

The geometric intersection number of a curve on a surface is the minimal number of self-intersections of any homotopic curve, i.e., of any curve obtained by continuous deformation. Given a curve c represented by a closed walk of length at most ℓ on a combinatorial surface of complexity n , we describe simple algorithms to (1) compute the geometric intersection number of c in O ( n + ℓ 2 ) time, (2) construct a curve homotopic to c that realizes this geometric intersection number in O ( n +ℓ 4 ) time, and (3) decide if the geometric intersection number of c is zero, i.e., if c is homotopic to a simple curve, in O ( n +ℓ log ℓ) time. The algorithms for (2) and (3) are restricted to orientable surfaces, but the algorithm for (1) is also valid on non-orientable surfaces. To our knowledge, no exact complexity analysis had yet appeared on those problems. An optimistic analysis of the complexity of the published algorithms for problems (1) and (3) gives at best a O ( n + g 2 ℓ 2 ) time complexity on a genus g surface without boundary. No polynomial time algorithm was known for problem (2) for surfaces without boundary. Interestingly, our solution to problem (3) provides a quasi-linear algorithm to a problem raised by Poincaré more than a century ago. Finally, we note that our algorithm for problem (1) extends to computing the geometric intersection number of two curves of length at most ℓ in O ( n + ℓ 2 ) time.

Combinatorial surface coating and greatly-improved soft magnetic performance of Fe/Fe3O4/resin composites

Structure-reinforced Fe/Fe3O4/resin soft magnetic composites (SMCs) have been fabricated through coating micron-sized Fe powders with high-purity Fe3O4 nanolayers and silicon resin films by combinatorial controlled oxidation and physical coating method. High magnetization Ms of 201 A m2 kg−1 can be reserved in the Fe/Fe3O4/resin SMCs due to high-purity ferrimagnetic Fe3O4 shells and low-content resin layers. The smooth Fe/Fe3O4 interfaces and uniform silicone resin coating layers in the Fe/Fe3O4/resin SMCs also lead to their low coercivity of 11.4 Oe and high compressed density of 7.50 g/cm3. For traditional metal-based SMCs fabricated by various common coating methods, their reduced core loss is usually achieved but accompanying with low magnetic induction and poor mechanical properties. In this work, high transverse rupture strength value of 92 MPa and greatly enhanced soft magnetic performance with both decreased core loss in accompany with high magnetic inductions are achieved for the fully densified Fe/Fe3O4/resin SMCs due to their well-structured composite interfaces, which promise their great latent applications for high-power and low-loss magnetic components.

Comparison of affinity ranking by target-directed dynamic combinatorial chemistry and surface plasmon resonance

Target-directed dynamic combinatorial chemistry (tdDCC) is a powerful method to screen ligands for pharmacologically relevant targets. Generating a dynamic library from reversibly reacting building blocks in the presence of a target protein leads to the amplification of the most potent library constituents. In previous studies on tdDCC, these compounds were identified in a qualitative “hit/no-hit”-manner. However, the precise relationship between the degree of amplification and the affinity of the library constituent has not yet been evaluated. To study the amplification–affinity relationship, we compared tdDCC experiments, employing reversible acylhydrazone formation and the bacterial adhesin FimH as a target, with affinities of the library constituents as determined by surface plasmon resonance.

In-Depth Characterization of Monocyte-Derived Macrophages using a Mass Cytometry-Based Phagocytosis Assay

Phagocytosis is a process in which target cells or particles are engulfed and taken up by other cells, typically professional phagocytes; this process is crucial in many physiological processes and disease states. The detection of targets for phagocytosis is directed by a complex repertoire of cell surface receptors. Pattern recognition receptors directly detect targets for binding and uptake, while opsonic and complement receptors detect objects coated by soluble factors. However, the importance of single and combinatorial surface marker expression across different phenotypes of professional phagocytes is not known. Here we developed a novel mass cytometry-based phagocytosis assay that enables the simultaneous detection of phagocytic events in combination with up to 40 other protein markers. We applied this assay to distinct monocyte derived macrophage (MDM) populations and found that prototypic M2-like MDMs phagocytose more E. coli than M1-like MDMs. Surface markers such as CD14, CD206, and CD163 rendered macrophages phagocytosis competent, but only CD209 directly correlated with the amount of particle uptake. Similarly, M2-like MDMs also phagocytosed more cancer cells than M1-like MDMs but, unlike M1-like MDMs, were insensitive to anti-CD47 opsonization. Our approach facilitates the simultaneous study of single-cell phenotypes, phagocytic activity, signaling and transcriptional events in complex cell mixtures.

Quantitative Analysis of Intestinal Stem Cell Dynamics Using Microfabricated Cell Culture Arrays.

Regeneration of intestinal epithelium is fueled by a heterogeneous population of rapidly proliferating stem cells (ISCs) found in the base of the small intestine and colonic crypts. ISCs populations can be enriched by fluorescence-activated cell sorting (FACS) based on expression of combinatorial cell surface markers, and fluorescent transgenes. Conventional ISC culture is performed by embedding single ISCs or whole crypt units in a matrix and culturing in conditions that stimulate or repress key pathways to recapitulate ISC niche signaling. Cultured ISCs form organoid, which are spherical, epithelial monolayers that are self-renewing, self-patterning, and demonstrate the full complement of intestinal epithelial cell lineages. However, this conventional "bulk" approach to studying ISC biology is often semiquantitative, low throughput, and masks clonal effects and ISC phenotypic heterogeneity. Our group has recently reported the construction, long-term biocompatibility, and use of microfabricated cell raft arrays (CRA) for high-throughput analysis of single ISCs and organoids. CRAs are composed of thousands of indexed and independently retrievable microwells, which in combination with time-lapse microscopy and/or gene-expression analyses are a powerful tool for studying clonal ISC dynamics and micro-niches. In this protocol, we describe how CRAs are used as an adaptable experimental platform to study the effect of exogenous factors on clonal stem cell behavior.

Comparative surface energetic study of Matrigel® and collagen I interactions with endothelial cells

Understanding of the surface energetic aspects of the spontaneously deposited proteins on biomaterial surfaces and how this influences cell adhesion and differentiation is an area of regenerative medicine that has not received adequate attention. Current controversies surround the role of the biomaterial substratum surface chemistry, the range of influence of said substratum, and the effects of different surface energy components of the protein interface. Endothelial cells (ECs) are a highly important cell type for regenerative medicine applications, such as tissue engineering, and In-vivo they interact with collagen I based stromal tissue and basement membranes producing different behavioral outcomes. The surface energetic properties of these tissue types and how they control EC behavior is not well known. In this work we studied the surface energetic properties of collagen I and Matrigel® on various previously characterized substratum polyurethanes (PU) via contact angle analysis and examined the subsequent EC network forming characteristics. A combinatorial surface energy approach was utilized that compared Zisman’s critical surface tension, Kaelble’s numerical method, and van Oss-Good-Chaudhury theory (vOGCT). We found that the unique, rapid network forming characteristics of ECs on Matrigel® could be attributed to the apolar or monopolar basic interfacial characteristics according to Zisman/Kaelble or vOGCT, respectively. We also found a lack of significant substratum influence on EC network forming characteristics for Matrigel® but collagen I showed a distinct influence where more apolar PU substrata tended to produce higher Lewis acid character collagen I interfaces which led to a greater interaction with ECs. Collagen I interfaces on more polar PU substrata lacked Lewis acid character and led to similar EC network characteristics as Matrigel®. We hypothesized that bipolar character of the protein film favored cell-substratum over cell-cell adhesive interactions which resulted in less rapidly forming but more stable networks.

Interfacial energetics approach for analysis of endothelial cell and segmental polyurethane interactions

Understanding the physicochemical interactions between endothelial cells and biomaterials is vital for regenerative medicine applications. Particularly, physical interactions between the substratum interface and spontaneously deposited biomacromolecules as well as between the induced biomolecular interface and the cell in terms of surface energetics are important factors to regulate cellular functions. In this study, we examined the physical interactions between endothelial cells and segmental polyurethanes (PUs) using l-tyrosine based PUs to examine the structure-property relations in terms of PU surface energies and endothelial cell organization. Since, contact angle analysis used to probe surface energetics provides incomplete interpretation and understanding of the physical interactions, we sought a combinatorial surface energetics approach utilizing water contact angle, Zisman’s critical surface tension (CST), Kaelble’s numerical method, and van Oss-Good-Chaudhury theory (vOGCT), and applied to both substrata and serum adsorbed matrix to correlate human umbilical vein endothelial cell (HUVEC) behavior with surface energetics of l-tyrosine based PU surfaces. We determined that, while water contact angle of substratum or adsorbed matrix did not correlate well with HUVEC behavior, overall higher polarity according to the numerical method as well as Lewis base character of the substratum explained increased HUVEC interaction and monolayer formation as opposed to organization into networks. Cell interaction was also interpreted in terms of the combined effects of substratum and adsorbed matrix polarity and Lewis acid-base character to determine the effect of PU segments.

Robust Prediction of Personalized Cell Recognition from a Cancer Population by a Dual Targeting Nanoparticle Library

Nanomaterials are used increasingly in diagnostics and therapeutics, particularly for malignancies. Efficient targeting of nanoparticles to specific cells is an important requirement for the development of successful nanoparticle‐based theranostics and personalized medicines. Gold nanoparticles are surface modified using a library of small organic molecules, and optionally folate, to investigate their ability to target four cell lines from common cancers, three having high levels of folate receptors expression. Uptake of these nanoparticles varies widely with surface chemistriy and cell lines. Sparse machine learning methods are used to computationally model surface chemistry–uptake relationships, to make quantitative predictions of uptake for new nanoparticle surface chemistries, and to elucidate molecular aspects of the interactions. The combination of combinatorial surface chemistry modification and machine learning models will facilitate the rapid development of targeted theranostics.

Discrete Systolic Inequalities and Decompositions of Triangulated Surfaces

How much cutting is needed to simplify the topology of a surface? We provide bounds for several instances of this question, for the minimum length of topologically non-trivial closed curves, pants decompositions, and cut graphs with a given combinatorial map in triangulated combinatorial surfaces (or their dual cross-metric counterpart). Our work builds upon Riemannian systolic inequalities, which bound the minimum length of non-trivial closed curves in terms of the genus and the area of the surface. We first describe a systematic way to translate Riemannian systolic inequalities to a discrete setting, and vice-versa. This implies a conjecture by Przytycka and Przytycki (Graph structure theory. Contemporary Mathematics, vol. 147, 1993), a number of new systolic inequalities in the discrete setting, and the fact that a theorem of Hutchinson on the edge-width of triangulated surfaces and Gromov's systolic inequality for surfaces are essentially equivalent. We also discuss how these proofs generalize to higher dimensions. Then we focus on topological decompositions of surfaces. Relying on ideas of Buser, we prove the existence of pants decompositions of length $$O(g^{3/2}n^{1/2})$$O(g3/2n1/2) for any triangulated combinatorial surface of genus $$g$$g with $$n$$n triangles, and describe an $$O(gn)$$O(gn)-time algorithm to compute such a decomposition. Finally, we consider the problem of embedding a cut graph (or more generally a cellular graph) with a given combinatorial map on a given surface. Using random triangulations, we prove (essentially) that, for any choice of a combinatorial map, there are some surfaces on which any cellular embedding with that combinatorial map has length superlinear in the number of triangles of the triangulated combinatorial surface. There is also a similar result for graphs embedded on polyhedral triangulations.

402 Isolation and Characterization of Intestinal Stem Cells Using Combinatorial Surface Markers and Robust Clonal Assay

402 Isolation and Characterization of Intestinal Stem Cells Using Combinatorial Surface Markers and Robust Clonal Assay

Multiplexed Orientation and Structure Analysis by Imaging Near-Edge X-ray Absorption Fine Structure (MOSAIX) for Combinatorial Surface Science

Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, as a technique, offers detailed information about the bonding environment of molecules at a surface. However, because it is a synchrotron based method, beam-time is limited and users must typically prioritize and narrowly define the scopes of experiments. In this study, we demonstrate a novel method that opens up the possibility of the use of large area NEXAFS imaging to pursue combinatorial studies. To explore the capabilities of the NIST full field NEXAFS microscope available at the National Synchrotron Light Source as a high throughput imaging instrument, we collected NEXAFS images from a sample array consisting of 144 different elements with a periodic sequence of different surface modifications. NEXAFS images collected from this model system illustrate how hyperspectral NEXAFS data can be used for parallel analysis of large numbers of samples either directly from the overall image or by extracting spectra from regions of interest.

Fabrication of Two-Dimensional Gradient Layer-by-Layer Films for Combinatorial Biosurface Studies

We have developed a novel gradient fabrication method for combinatorial surface studies that provides the equivalent of 5000 individual polyelectrolyte multilayer (PEM) film physicochemical conditions in a single 7 cm square film. A simple, inexpensive, and versatile automated layering instrument was built, which can generate a gradient of physical properties on a film in 1 dimension laterally by simultaneously changing both the location of polyelectrolyte adsorption and the layering conditions, such as pH or salt concentration of the polyelectrolyte dipping solutions. By rotating the substrate 90° after each deposition cycle, full 2-dimensional gradient combinatorial films were fabricated over many layers, spanning virtually all previous combinations of stable deposition pH and salt conditions for both poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA), a process which previously required more than 10 000 separate film samples. Surface spatial profiles of film thickness, surface energy (wettability), density (refractive index), and stiffness (modulus) were generated and correlated to assembly conditions. Additionally, step gradient films were generated first by varying the number of bilayers along one axis and pH along the other, which enabled us to measure their combined effect on thickness. To test for biocompatibility, we incubated HEK 293 cells on step gradient films and 2D combinatorial films for 48 h and determined that film assembly conditions played a major role, especially in controlling the stiffness and the density, which could be tailored with deposition pH over a wide range. Optimal growth conditions were discovered not at the extremes of fabrication pH, but instead near PAH pHs of 4–6 and PAA pH around 4, demonstrating that these PEM biosurfaces and this technique are suitable for optimizing high-throughput cellular screening.

A plate-based definition of discrete surfaces

By the use of certain discrete plates in the role of polygonal faces we mimic the definition of a combinatorial surface to produce, for each adjacency pair (k,k¯)≠(6,6), k,k¯∈{6,18,26}, a new family Skk¯ of discrete surfaces, termed (k,k¯)-surfaces, in the grid Z3 that strictly contains several well-known families of surfaces, such as the strong and simplicity surfaces, as well as other objects considered as surfaces in the literature. Moreover, the number of possible configurations in the 26-neighbourhood of a (26,6)-surface voxel is estimated to rise up to 10,580. In addition, we show that Skk¯ is the largest set of discrete surfaces that can be defined within the framework for Digital Topology in (Ayala et al., 2002).

Finding one tight cycle

A cycle on a combinatorial surface is tight if it as short as possible in its (free) homotopy class. We describe an algorithm to compute a single tight, noncontractible, essentially simple cycle on a given orientable combinatorial surface in O ( n log n ) time. The only method previously known for this problem was to compute the globally shortest noncontractible or nonseparating cycle in O (min{ g 3 , n }, n log n ) time, where g is the genus of the surface. As a consequence, we can compute the shortest cycle freely homotopic to a chosen boundary cycle in O ( n log n ) time, a tight octagonal decomposition in O ( gn log n ) time, and a shortest contractible cycle enclosing a nonempty set of faces in O ( n log 2 n ) time.

Computing the Shortest Essential Cycle

An essential cycle on a surface is a simple cycle that cannot be continuously deformed to a point or a single boundary. We describe algorithms to compute the shortest essential cycle in an orientable combinatorial surface in O(n 2log n) time, or in O(nlog n) time when both the genus and number of boundaries are fixed. Our results correct an error in a paper of Erickson and Har-Peled (Discrete Comput. Geom. 31(1):37–59, 2004).