Surface-initiated hyperbranched polyglycerol as an ultralow-fouling coating on glass, silicon, and porous silicon substrates

Microscopic Analysis of the Water/Glycerol/EO30PS System in Bulk and on a Solid Substrate

Surfactant systems are often employed in cosmetic formulations where they dry on skin as a surface, thereby becoming increasingly concentrated systems. To better understand this drying process, we focused on the difference of self-assembled structures of the water/glycerol/polyoxyethylene (30) phytosteryl ether (EO30PS) system in bulk and on a solid substrate because the interaction between the substrate and the surfactant may have a substantial effect on the self-assembly, which may be related to the bulk structure but in detail may also differ strongly from the bulk situation. In bulk, small-angle neutron scattering (SANS) experiments showed that with increasing loss of water, the degree of ordering increases but changes of the aggregate structure are rather small. The results indicate that ellipsoidal micelles of EO30PS are densely packed and simply become more ordered in bulk during the drying process. On the other hand, neutron reflectometry revealed that EO30PS molecules adsorb onto a Si surface in the form of bilayers and analysis indicates that at a high concentration (c = 20 wt %), there are on average two bilayers (a double bilayer) on the Si substrate. The adsorbed membrane structure of EO30PS is rather thin with respect to its hydrophobic part, indicating tilted molecules, containing only some solvent, and being not highly ordered. These experimental results then allow for a much deeper understanding of the structural properties of practical formulations as they are applied, for instance, in cosmetic lotions.

Design of Microstructure-Engineered Polymers for Energy and Environmental Conservation

With the ever-growing demand for sustainability, designing polymeric materials using readily accessible feedstocks provides potential solutions to address the challenges in energy and environmental conservation. Complementing the prevailing strategy of varying chemical composition, engineering microstructures of polymer chains by precisely controlling their chain length distribution, main chain regio-/stereoregularity, monomer or segment sequence, and architecture creates a powerful toolbox to rapidly access diversified material properties. In this Perspective, we lay out recent advances in utilizing appropriately designed polymers in a wide range of applications such as plastic recycling, water purification, and solar energy storage and conversion. With decoupled structural parameters, these studies have established various microstructure-function relationships. Given the progress outlined here, we envision that the microstructure-engineering strategy will accelerate the design and optimization of polymeric materials to meet sustainability criteria.

Attachment of endothelial colony-forming cells onto a surface bearing immobilized anti-CD34 antibodies: Specific CD34 binding versus nonspecific binding

Cardiovascular disease is a leading cause of death worldwide; however, despite substantial advances in medical device surface modifications, no synthetic coatings have so far matched the native endothelium as the optimal hemocompatible surface for blood-contacting implants. A promising strategy for rapid restoration of the endothelium on blood-contacting biomedical devices entails attracting circulating endothelial cells or their progenitors, via immobilized cell-capture molecules; for example, anti-CD34 antibody to attract CD34+ endothelial colony-forming cells (ECFCs). Inherent is the assumption that the cells attracted to the biomaterial surface are bound exclusively via a specific CD34 binding. However, serum proteins might adsorb in-between or on the top of antibody molecules and attract ECFCs via other binding mechanisms. Here, we studied whether a surface with immobilized anti-CD34 antibodies attracts ECFCs via a specific CD34 binding or a nonspecific (non-CD34) binding. To minimize serum protein adsorption, a fouling-resistant layer of hyperbranched polyglycerol (HPG) was used as a "blank slate," onto which anti-CD34 antibodies were immobilized via aldehyde-amine coupling reaction after oxidation of terminal diols to aldehydes. An isotype antibody, mIgG1, was surface-immobilized analogously and was used as the control for antigen-binding specificity. Cell binding was also measured on the HPG hydrogel layer before and after oxidation. The surface analysis methods, x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry, were used to verify the intended surface chemistries and revealed that the surface coverage of antibodies was sparse, yet the anti-CD34 antibody grafted surface-bound ECFCs very effectively. Moreover, it still captured the ECFCs after BSA passivation. However, cells also attached to oxidized HPG and immobilized mIgG1, though in much lower amounts. While our results confirm the effectiveness of attracting ECFCs via surface-bound anti-CD34 antibodies, our observation of a nonspecific binding component highlights the importance of considering its consequences in future studies.

A hyperbranched polyglycerol-functionalized polymer polar stationary phase

A polymer polar stationary phase functionalized with hyperbranched polyglycerol for hydrophilic interaction chromatography (HILIC) is described. It is prepared via surface-initiated ring-opening polymerization of hyperbranched polyglycerol onto hydrolzed poly(glycidyl methacrylate-divinylbenzene) microspheres. The capacity of the functional groups can be maniputed by repeating hyperbranch layers. The phase showed typical HILIC character with good separation performance towards tested polar analytes. It also exhibited wider pH tolerance range (e.g. at least 2 to 12) and as well negligible bleed level under gradient elution mode (even to 50% fraction of water).

Effect of Branching Degree of Dendritic Polyglycerols on Plasma Protein Adsorption: Relationship between Hydration States and Surface Morphology

This study focuses on dendritic glycerols and investigates the construction of biocompatible surfaces by understanding how differences in the branching of these molecules change the interactions with the biological components. The two molecules, polyglycerol dendrimer (PGD), which has a completely branched structure, and hyperbranched polyglycerol (HPG), which has an incompletely branched structure, are compared and the differences in branching are evaluated. It is shown that PGD has a little bit more intermediate water than HPG, which reflects the differences in the branching. The effect of surface state on the adsorption of the plasma proteins, human serum albumin (HSA), fibrinogen (Fib), and fibronectin (FN), is discussed by modifying a glass surface using these molecules with different hydration states. The adsorption of HSA decreases to several percent for HPG and 10% for PGD compared to unmodified substrate. Although the adsorption of Fib decreases to 5% for HPG, an increase to 150% is observed for PGD. Since this specific Fib adsorption observed only onto PGD is suppressed in the cases of a mixed solution of HSA and Fib or sequentially using HSA solution and then Fib solution, it is thought that the Vroman effect is suppressed on the PGD-modified surface. Furthermore, when AFM measurements are performed in PBS to understand the surface roughness, PGD is found to be more highly non-uniform. Because of this, the nanometer scale roughness that is significantly observed only on the PGD-modified surface is thought to have an effect on the characteristic adsorption properties of Fib. Thus, although both PGD and HPG with different branching have intermediate water, the proportion differs between PGD and HPG. Therefore, it is found that differences occur in the plasma protein adsorption mechanisms depending on the coordinates and density of hydroxyl groups within the molecules.

Review on Interfacial Bonding Mechanism of Functional Polymer Coating on Glass in Atomistic Modeling Perspective

Atomistic modeling methods are successfully applied to understand interfacial interaction in nanoscale size and analyze adhesion mechanism in the organic-inorganic interface. In this paper, we review recent representative atomistic simulation works, focusing on the interfacial bonding, adhesion strength, and failure behavior between polymer film and silicate glass. The simulation works are described under two categories, namely non-bonded and bonded interaction. In the works for non-bonded interaction, three main interactions, namely van der Waals interaction, polar interaction, and hydrogen bonds, are investigated, and the contributions to interfacial adhesion energy are analyzed. It is revealed that the most dominant interaction for adhesion is hydrogen bonding, but flexibility of the polymer film and modes of adhesion measurement test do affect adhesion and failure behavior. In the case of bonded interactions, the mechanism of covalent silane bond formation through condensation and hydrolysis process is reviewed, and surface reactivity, molecular density, and adhesion properties are calculated with an example of silane functionalized polymer. Besides interfacial interactions, effects of external conditions, such as surface morphology of the glass substrate and relative humidity on the adhesion and failure behavior, are presented, and modeling techniques developed for building interfacial system and calculating adhesion strengths are briefly introduced.

Surface chemical reactions on self-assembled silane based monolayers

In this review, we aim to update our review "Chemical modification of self-assembled silane-based monolayers by surface reactions" which was published in 2010 and has developed into an important guiding tool for researchers working on the modification of solid substrate surface properties by chemical modification of silane-based self-assembled monolayers. Due to the rapid development of this field of research in the last decade, the utilization of chemical functionalities in self-assembled monolayers has been significantly improved and some new processes were introduced in chemical surface reactions for tailoring the properties of solid substrates. Thus, it is time to update the developments in the surface functionalization of silane-based molecules. Hence, after a short introduction on self-assembled monolayers, this review focuses on a series of chemical reactions, i.e., nucleophilic substitution, click chemistry, supramolecular modification, photochemical reaction, and other reactions, which have been applied for the modification of hydroxyl-terminated substrates, like silicon and glass, which have been reported during the last 10 years.

Hyperbranched Polyglycerols as Robust Up-Conversion Nanoparticle Coating Layer for Feasible Cell Imaging

Owing to the wide spectrum of excitation wavelengths of up-conversion nanoparticles (UCNPs) by precisely regulating the percentage of doping elements, UCNPs have been emerging as bioimaging agents. The key drawback of UCNPs is their poor dispersibility in aqueous solution and it is hard to introduce the chemical versatility of function groups. In our study, we present a robust and feasible UCNP modification approach by introducing hyperbranched polyglycerols (hbPGs) as a coating layer. When grafted by hbPGs, the solubility and biocompatibility of UCNPs are significantly improved. Moreover, we also systematically investigated and optimized the chemical modification approach of amino acids or green fluorescence protein (GFP), respectively, grafting onto hbPGs and hbPGs-g-UCNP by oxidizing the vicinal diol to be an aldehyde group, which reacts more feasibly with amino-containing functional molecules. Then, we investigated the drug-encapsulating properties of hbPGs-Arg with DOX and cell imaging of GFP-grafted hbPGs-g-UCNP, respectively. The excellent cell imaging in tumor cells indicated that hbPG-modification of UCNPs displayed potential for applications in drug delivery and disease diagnosis.

Functionalization of Magnetic Nanoparticles by Folate as Potential MRI Contrast Agent for Breast Cancer Diagnostics

In recent years, the intrinsic magnetic properties of magnetic nanoparticles (MNPs) have made them one of the most promising candidates for magnetic resonance imaging (MRI). This study aims to evaluate the effect of different coating agents (with and without targeting agents) on the magnetic property of MNPs. In detail, iron oxide nanoparticles (IONPs) were prepared by the polyol method. The nanoparticles were then divided into two groups, one of which was coated with silica (SiO2) and hyperbranched polyglycerol (HPG) (SPION@SiO2@HPG); the other was covered by HPG alone (SPION@HPG). In the following section, folic acid (FA), as a targeting agent, was attached on the surface of nanoparticles. Physicochemical properties of nanostructures were characterized using Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and a vibrating sample magnetometer (VSM). TEM results showed that SPION@HPG was monodispersed with the average size of about 20 nm, while SPION@SiO2@HPG had a size of about 25 nm. Moreover, HPG coated nanoparticles had much lower magnetic saturation than the silica coated ones. The MR signal intensity of the nanostructures showed a relation between increasing the nanoparticle concentrations inside the MCF-7 cells and decreasing the signal related to the T2 relaxation time. The comparison of coating showed that SPION@SiO2@HPG (with/without a targeting agent) had significantly higher r2 value in comparison to Fe3O4@HPG. Based on the results of this study, the Fe3O4@SiO2@HPG-FA nanoparticles have shown the best magnetic properties, and can be considered promising contrast agents for magnetic resonance imaging applications.

Review of Techniques to Achieve Optical Surface Cleanliness and Their Potential Application to Surgical Endoscopes

A clear visualization of the operative field is of critical importance in endoscopic surgery. During surgery the endoscope lens can get fouled by body fluids (eg, blood), ground substance, rinsing fluid, bone dust, or smoke plumes, resulting in visual impairment. As a result, surgeons spend part of the procedure on intermittent cleaning of the endoscope lens. Current cleaning methods that rely on manual wiping or a lens irrigation system are still far from ideal, leading to longer procedure times, dirtying of the surgical site, and reduced visual acuity, potentially reducing patient safety. With the goal of finding a solution to these issues, a literature review was conducted to identify and categorize existing techniques capable of achieving optically clean surfaces, and to show which techniques can potentially be implemented in surgical practice. The review found that the most promising method for achieving surface cleanliness consists of a hybrid solution, namely, that of a hydrophilic or hydrophobic coating on the endoscope lens and the use of the existing lens irrigation system.

Functionalization of surfaces with branched polymers

This review summarizes recent developments in the field of surfaces functionalized with branched polymers, including the fabrication methods, morphologies, properties and applications.

Exploiting a new glycerol-based copolymer as a route to wound healing: Synthesis, characterization and biocompatibility assessment

The use of biocompatible materials based on naturally derived monomers plays a key role in pharmaceutical and cosmetic industries. In this paper we describe the synthesis of a new low molecular weight copolymer, based on glycerol and l-tartaric acid, useful to develop biocompatible dermal patches with drug delivery properties. The copolymer's chemical composition was assessed by FT-IR (Fourier transform infrared spectroscopy), (1)H NMR ((1)H Nuclear Magnetic Resonance) and XPS (X-ray photoelectron spectroscopy), while its molecular weight distribution was estimated by SEC (size exclusion chromatography). Copolymer thermal properties were studied by TGA (thermogravimetric analysis). Biological evaluations by MTT assay and SEM (scanning electron microscopy) observations performed with murine fibroblasts and human keratinocytes (HaCaT) revealed a good compatibility of the proposed copolymer. Ciprofloxacin was selected as model drug and its release was evaluated by HPLC (high performance liquid chromatography), showing that the new copolymer supplied promising results as drug delivery system for wound healing applications. Furthermore, investigations on Skin-Mesenchymal stem cells (S-MSCs) behaviour and gene expression showed that the copolymer and its combination with ciprofloxacin did not affect their stemness. In this regard, the fabrication of dermal patches with new, low cost materials for local treatment of skin infections represents an attractive strategy in order to bypass the worrying side effects of systemic antibiotic therapy. Overall, the performed physico-chemical characterization, drug release test and biological evaluations showed that this new copolymer could be a promising tool for the in situ delivery of bioactive molecules during skin lesions treatment.

Human aortic endothelial cell morphology influenced by topography of porous silicon substrates

Porous silicon has received much attention because of its optical properties and for its usefulness in cell-based biosensing, drug delivery, and tissue engineering applications. Surface properties of the biomaterial are associated with cell adhesion and with proliferation, migration, and differentiation. The present article analyzes the behavior of human aortic endothelial cells in macro- and nanoporous collagen-modified porous silicon samples. On both substrates, cells are well adhered and numerous. Confocal microscopy and scanning electron microscopy were employed to study the effects of porosity on the morphology of the cells. On macroporous silicon, filopodia is not observed but the cell spreads on the surface, increasing the lamellipodia surface which penetrates the macropore. On nanoporous silicon, multiple filopodia were found to branch out from the cell body. These results demonstrate that the pore size plays a key role in controlling the morphology and growth rate of human aortic endothelial cells, and that these forms of silicon can be used to control cell development in tissue engineering as well as in basic cell biology research.

Non-cell-adhesive substrates for printing of arrayed biomaterials

Cellular microarrays have become extremely useful in expediting the investigation of large libraries of (bio)materials for both in vitro and in vivo biomedical applications. An exceedingly simple strategy is developed for the fabrication of non-cell-adhesive substrates supporting the immobilization of diverse (bio)material features, including both monomeric and polymeric adhesion molecules (e.g., RGD and polylysine), hydrogels, and polymers.

A shape memory copolymer based on 2-(dimethylamino)ethyl methacrylate and methyl allyl polyethenoxy ether for potential biological applications

This study reports a novel shape memory copolymer synthesized with 2-(dimethylamino)-ethyl-methacrylate (DMAEMA) and methyl-allyl-polyethenoxy-ether (TPEG) for potential biological applications.

Polyglycerol coated polypropylene surfaces for protein and bacteria resistance

Polyglycerol coated polypropylene films were prepared in two steps by plasma bromination and grafting of polyglycerol. Films were characterized and their bioinertness against proteins and bacteria was investigated.