Neutral Hydrophilic Surface Research Articles

Surface charge transition nano-theranostics based on ultra-small Fe3O4 nanoparticles for enhanced photodynamic and photothermal therapy against nasopharyngeal carcinoma

Platinum-based concurrent chemo-radiotherapy is the most common strategy for the treatment of Nasopharyngeal carcinoma. However, low efficacy and side effects are the two major problems associated with this approach. Therefore, it is urgent need to explore novel therapeutic modalities to meet clinically standards. Photothermal therapy (PTT) and photodynamic therapy (PDT) are non-invasive and light trigger modalities received great attention to overcome the limitations and significantly improved cancer therapy. Here, we developed acidity surface charge transformable nanocluster (NCs) composed of Indocyanine green (ICG), Fe3O4, and Palmitoyl ascorbic acid (PA) with pH-responsive PEG-b-PAEMA-PDMA for enhanced synergistic PDT/PTT. NCs has the neutral hydrophilic surface helps to prolong blood circulation and instantly transformed to positively charged surface at tumoral acidic pH (6.5), which promoted the cellular uptake. Under laser irradiation (808 nm, 1 W/cm2), NCs produced PTT effect, concurrently it converts singlet oxygen (1O2) into H2O2, which can be further involved in Fenton reaction and produce toxic hydroxyl radical (•OH) enhances therapy efficacy. In vitro experiments on HNE-1 cancer cells showed improved intracellular uptake of NCs at low pH and simultaneously induced higher cytotoxicity medicated by synergetic PDT/PTT effect. In vivo therapeutic study revealed that NCs treatment under laser irradiation showed superior inhibition of tumor growth in HNE-1 tumor bearing mice model. Taken together, the present findings suggest that NCs could be used as “all in one” nano theranostic agent for enhanced PDT/PTT of cancer therapy.

Fundamental Principles of the Thermodynamics and Kinetics of Protein Adsorption to Material Surfaces

Protein adsorption is important for essentially any process that involves the contact of a protein-containing solution and a material surface, with the resulting formation of the adsorbed layer of protein determined by the thermodynamics and kinetics of the system involved. This paper presents an overview of the fundamentals of these processes. First, the hierarchical structure of proteins and the types of bonding that stabilize a protein’s native-state structure are presented. This section is then followed by a section presenting the thermodynamic driving forces that influence the way that proteins adsorb and conformationally change for three characteristically different types of surface chemistries: nonpolar (hydrophobic) surfaces, neutral hydrophilic surfaces, and charged surfaces. The final section of this paper addresses how kinetics and thermodynamics combine together to influence protein adsorption behavior, followed by concluding remarks.

Overcoming multiple gastrointestinal barriers by bilayer modified hollow mesoporous silica nanocarriers.

Oral administration of nanocarriers remains a big challenge due to the multiple gastrointestinal barriers. In order to achieve both strong mucus permeation and efficient epithelial absorption, we modified the surface of silica nanoparticles with two layers: cell penetrating peptide (CPP) layer and succinylated casein (SCN) layer. The newly developed nanoformulations are demonstrated to have the following advantages: 1) versatile carrier with easy preparation, 2) high drug loading especially for poor soluble molecules, 3) reduced drug leakage in the stomach, 4) effective mucus penetration and transepithelial transport and 5) good biocompatibility, which in all indicate a great potential of this bilayer-modification strategy to facilitate the oral delivery of therapeutic agents.

Attractive double-layer forces between neutral hydrophobic and neutral hydrophilic surfaces

The interaction between surface patches of proteins with different surface properties has a vital role to play driving conformational changes in proteins in different salt solutions. We demonstrate the existence of ion-specific attractive double-layer forces between neutral hydrophobic and hydrophilic surfaces in the presence of certain salt solutions. This is performed by solving a generalized Poisson-Boltzmann equation for two unequal surfaces. In the calculations, we utilize parametrized ion-surface potentials and dielectric-constant profiles deduced from recent non-primitive-model molecular dynamics simulations that partially account for molecular structure and hydration effects.

Mechanical Desorption of Single Fibronectin Type III Module from Hydrophilic and Hydrophobic Surfaces

Protein-surface adsorption plays an important role in the biological response to any kind of material in contact with a biological fluid. The process of protein adsorption is influenced by numerous factors, including surface properties, protein sequence and conformation, and solvent conditions. Although it is generally found that protein adsorption is greater on more hydrophobic surfaces than neutral hydrophilic surfaces, certain functional groups not simply the degree of the hydrophobicity, influence adsorption. Furthermore, the folding conformation of surface-tethered proteins also may be influenced by the surface itself, leading to behavior that differ from the bulk. Fibronectin (FN) is a multimodular extracellular protein and its biological activity is determined by its orientation and/or unfolding on the surfaces, which remains poorly understood. Single molecule force spectroscopy (SMFS) has emerged as a powerful technique for watching single proteins fold and unfolding process. In this work, we report studies of the unfolding process of single FN 10th type III domain (FNIII10) on hydrophobic and hydrophilic gold surfaces accomplished using atomic force microscope-based SMFS.

Proteolytic cleaning of a surface-bound rubisco protein stain

We present a combined experimental and mathematical study of the proteolysis of a surface-bound rubisco protein stain. The adsorption and desorption of subtilisin A (SA) onto and from surface-bound rubisco films were found to be a strong function of the surface chemistry underlying the protein stain; the stain acted as a biosensor able to convey information about the underlying surface to the attacking protease. The apparent protease adsorption rate constants ( k a ) were 0.016 ± 0.007 , 0.014 ± 0.004 and 0.048 ± 0.005 min - 1 ppm - 1 while the apparent desorption rate constants ( k d ) were 1.60 ± 0.15 , 1.05 ± 0.02 and 1.75 ± 0.05 min - 1 for hydrophobic, neutral-hydrophilic and negatively charged hydrophilic surfaces, respectively. The apparent proteolysis rate constant of surface-bound rubisco and the enzyme deactivation rate constant were estimated to be 1.7 ± 0.1 m 2 mg - 1 min - 1 and 0.03 ± 0.01 min - 1 , respectively, independent of underlying surface chemistry. The results demonstrated higher protein removal from the charged hydrophilic surface relative to the other two surfaces. Rubisco cleanability from the charged and hydrophobic surfaces increased with increasing bulk enzyme concentration (and hence surface enzyme concentration) and was better for the charged surface, perhaps reflecting the higher k a value. Conversely, rubisco cleanability from the neutral hydrophilic surface was surprisingly insensitive to variation in bulk enzyme concentration. Overall cleaning efficiency was also substantially lower for the neutral hydrophilic surface when compared with the hydrophobic surface, even though k a values for each surface were similar. These findings indicate that surface proteolysis is significantly impaired at low values of k d , suggesting that enzyme mobility at the interface may be closely linked to cleaning performance. The model presented here is expected to be a useful tool in the detergent industries to screen and gauge the cleaning performance of detergent–enzyme formulations, and may also be able to facilitate the design of surface treatments that convey cleaning signals to attacking proteases.

Solid Surface Chemical and Physical Effects on the Adsorption of Recombinant Factor VIII

The adsorption of a recombinant Factor VIII to silica surfaces coated to present different hydrophilic/hydrophobic, electrostatic and steric characteristics was monitored in situ, with ellipsometry. rFVIII adsorption affinity was high for hydrophobic surfaces and hydrophilic, charged surfaces. A lower affinity was recorded between rFVIII and a neutral hydrophilic surface, with substantial reduction in rFVIII adsorption to electronically neutral surfaces presenting pendant poly[ethylene oxide] chains. We conclude that steric repulsion is a requirement for minimizing rFVIII adsorption at solid surfaces.

Theoretical analysis of adsorption thermodynamics for hydrophobic peptide residues on SAM surfaces of varying functionality.

At a fundamental level, protein adsorption to a synthetic surface must be strongly influenced by the interaction between the peptide residues presented by the protein's surface (primary protein structure) and the functional groups presented by the synthetic surface. In this study, semi-empirical molecular modeling was used along with experimental wetting data to theoretically approach protein adsorption at this primary structural level. Changes in enthalpy, entropy, and Gibbs free energy were calculated as a function of residue-surface separation distance for the adsorption of individual hydrophobic peptide residues (valine, leucine, phenylalanine) on alkanethiol self-assembled monolayers on gold [Au-S(CH(2))(15)-X; X = CH(3), OH, NH(3)(+), COO(-)]. The results predict that the adsorption of each type of hydrophobic residue is energetically favorable and entropy dominated on a methyl-terminated hydrophobic surface, energetically unfavorable and enthalpy dominated on a hydroxyl-terminated neutral hydrophilic surface, and very slightly favorable to unfavorable and enthalpy dominated on charged surfaces. These theoretical results provide a basis for understanding some of the fundamental effects governing protein adsorption to synthetic surfaces. This level of understanding is needed for the proactive design of surfaces to control protein adsorption and subsequent cellular response for both implant and tissue engineering applications.

Self-Assembled Monolayers of Alkanethiolates on Thin Gold Films as Substrates for Surface Force Measurements. Long-Range Hydrophobic Interactions and Electrostatic Double-Layer Interactions

Surfaces prepared by self-assembly of alkanethiolates onto thin (10 nm) gold films supported on glass have been used as substrates for surface force measurements between macroscopic surfaces. Surface roughness, the order in the monomolecular film, wetting properties, and their stability in aqueous electrolyte solutions have been investigated using atomic force microscopy, infrared absorption spectroscopy, and contact angle measurements. Direct force measurements have been performed with a noninterferometric bimorph surface force apparatus, using surfaces with differently functionalized thiolates; measurements were made in air, water, and aqueous electrolyte solutions. Results from force measurements between hydrophobic and neutral hydrophilic surfaces in air and water are presented and discussed, as well as some results from measurements with surfaces exposing carboxylic groups in various aqueous electrolyte solutions. It is demonstrated that alkanethiol monolayers self-assembled onto thin gold films on m...

Human monocyte/macrophage adhesion and cytokine production on surface-modified poly(tetrafluoroethylene/hexafluoropropylene) polymers with and without protein preadsorption.

To study surface property-dependent human monocyte adhesion and cytokine (IL-1 beta, IL-6, TNF-alpha) production, poly(tetrafluoroethylene/hexafluoropropylene) (FEP) polymer was modified to exhibit neutral, anionic, or cationic properties by incorporating amide (CONH2) and/or carboxyl (COOH) or aminoethyl amide [CONH(CH2CH2NH)nCH2CH2NH2] groups on the surface. Monocyte adhesion on surface-modified FEP polymers and cytokines released by monocytes/macrophages (MC/MO) into the culture medium were compared to control tissue culture polystyrene (TCPS) at days 1 and 8. On day 1, the neutral surface FEP polymer with incorporated amide (NH2) groups showed the greatest inhibition of adhesion, 89% (P < .01), and cytokine production (IL-1 beta with 58%, IL-6 with 70%, and TNF-alpha with 39%) compared to control TCPS. In contrast, the highly cationic [CONH(CH2CH2NH)nCH2CH2NH2] surface did not show significant (P > .01) inhibition of monocyte adhesion and cytokine production. When fibrinogen or IgG was preadsorbed to the surface, the inhibitory effects of the neutral surface FEP polymer on monocyte adhesion and cytokine production were not altered. In addition, other surface-modified FEP polymers showed similar inhibition of monocyte adhesion and cytokine production compared to TCPS. Specifically, as the incorporation of carboxyl (COOH) group content increased on FEP polymer surfaces, monocyte adhesion and cytokine production were also increased on day 1 with IgG preadsorption. On day 8, all surface-modified FEP polymers showed significant (P < .01) inhibition of monocyte adhesion when fibrinogen or IgG was preadsorbed. However, without protein (fibrinogen or IgG) preadsorption, monocyte adhesion was not significantly inhibited compared to control TCPS. In addition, cytokine production detected by ELISAs on day 8 showed no detectable levels of IL-1 beta and significantly decreased levels of IL-6 compared to day 1 for all tested polymers, with or without protein preadsorption. Interestingly, the level of TNF-alpha production on day 8 remained high although not as high as on day 1. Based on these results, we suggest that FEP polymers with neutral hydrophilic surface properties may adhere and activate the least number of monocytes, which are important mediators of biocompatibility.

Theory of hydration forces. Nonlocal electrostatic interaction of neutral surfaces

The nonlocal electrostatic contribution to the hydration (structural) repulsion of neutral hydrophilic surfaces separated by thin water layer is considered. This contribution arises from the form of the image–charge interaction of alternating positively and negatively charged polar groups attached to one of the surfaces with nonpolar background of another surface. Characteristic features of this interaction are shown to be determined by the lateral ordering of the polar groups. Similar features were found previously in generalized free-field model of the interaction. Both models are in a good quantitative agreement with the experimental data on lipid membranes, and give consistent physical explanation to observable dependences of amplitude and decay length of the hydration force on the nature and structure of the surfaces. This similarity makes it impossible to distinguish any particular mediator of the hydration force at the present state of the knowledge. At the same time it provides a quite general picture of the role of lateral structure of the surfaces in the hydration force.