Distinct skyrmion phases at room temperature in two-dimensional ferromagnet Fe3GaTe2.

Distinct skyrmion phases at room temperature hosted by one material offer additional degree of freedom for the design of topology-based compact and energetically-efficient spintronic devices. The field has been extended to low-dimensional magnets with the discovery of magnetism in two-dimensional van der Waals magnets. However, creating multiple skyrmion phases in 2D magnets, especially above room temperature, remains a major challenge. Here, we report the experimental observation of mixed-type skyrmions, exhibiting both Bloch and hybrid characteristics, in a room-temperature ferromagnet Fe3GaTe2. Analysis of the magnetic intensities under varied imaging conditions coupled with complementary simulations reveal that spontaneous Bloch skyrmions exist as the magnetic ground state with the coexistence of hybrid stripes domain, on account of the interplay between the dipolar interaction and the Dzyaloshinskii-Moriya interaction. Moreover, hybrid skyrmions are created and their coexisting phases with Bloch skyrmions exhibit considerably high thermostability, enduring up to 328 K. The findings open perspectives for 2D spintronic devices incorporating distinct skyrmion phases at room temperature.

Cation Chain Length of Nonhalogenated Ionic Liquids Matters in Enhancing SERS of Cytochrome c on Zr-Al-Co-O Nanotube Arrays.

Surface-enhanced Raman scattering (SERS) is a remarkably powerful analytical technique enabling trace-level detection of biological molecules. The interaction of a probe molecule with the SERS substrate shows important distinctions in the SERS spectra, providing inherent fingerprint information on the probe molecule. Herein, nonhalogenated phosphonium-based ionic liquids (ILs) containing cations with varying chain lengths were used as trace additives to amplify the interaction between the cytochrome c (Cyt c) and Zr-Al-Co-O (ZACO) nanotube arrays, strengthening the SERS signals. An increased enhancement factor (EF) by 2.5-41.2 times compared with the system without ILs was achieved. The improvement of the SERS sensitivity with the introduction of these ILs is strongly dependent on the cation chain length, in which the increasing magnitude of EF is more pronounced in the system with a longer alkyl chain length on the cation. Comparing the interaction forces measured by Cyt c-grafted atomic force microscopy (AFM) probes on ZACO substrates with those predicted by the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, the van der Waals forces became increasingly dominant as the chain length of the cations increased, associated with stronger Cyt c-ZACO XDLVO interaction forces. The major contributing component, van der Waals force, stems from the longer cation chains of the IL, which act as a bridge to connect Cyt c and the ZACO substrate, promoting the anchoring of the Cyt c molecules onto the substrate, thereby benefiting SERS enhancement.

Integrative studies of ionic liquid interface layers: bridging experiments, theoretical models and simulations.

Ionic liquids (ILs) are a class of salts existing in the liquid state below 100 °C, possessing low volatility, high thermal stability as well as many highly attractive solvent and electrochemical capabilities, etc., making them highly tunable for a great variety of applications, such as lubricants, electrolytes, and soft functional materials. In many applications, ILs are first either physi- or chemisorbed on a solid surface to successively create more functional materials. The functions of ILs at solid surfaces can differ considerably from those of bulk ILs, mainly due to distinct interfacial layers with tunable structures resulting in new ionic liquid interface layer properties and enhanced performance. Due to an almost infinite number of possible combinations among the cations and anions to form ILs, the diversity of various solid surfaces, as well as different external conditions and stimuli, a detailed molecular-level understanding of their structure-property relationship is of utmost significance for a judicious design of IL-solid interfaces with appropriate properties for task-specific applications. Many experimental techniques, such as atomic force microscopy, surface force apparatus, and so on, have been used for studying the ion structuring of the IL interface layer. Molecular Dynamics simulations have been widely used to investigate the microscopic behavior of the IL interface layer. To interpret and clarify the IL structure and dynamics as well as to predict their properties, it is always beneficial to combine both experiments and simulations as close as possible. In another theoretical model development to bridge the structure and properties of the IL interface layer with performance, thermodynamic prediction & property modeling has been demonstrated as an effective tool to add the properties and function of the studied nanomaterials. Herein, we present recent findings from applying the multiscale triangle "experiment-simulation-thermodynamic modeling" in the studies of ion structuring of ILs in the vicinity of solid surfaces, as well as how it qualitatively and quantitatively correlates to the overall ILs properties, performance, and function. We introduce the most common techniques behind "experiment-simulation-thermodynamic modeling" and how they are applied for studying the IL interface layer structuring, and we highlight the possibilities of the IL interface layer structuring in applications such as lubrication and energy storage.

Ti-Si-Zr-Zn Nanometallic Glass Substrate with a Tunable Zinc Composition for Surface-Enhanced Raman Scattering of Cytochrome c.

As a remarkably powerful analytical technique, surface-enhanced Raman scattering (SERS) continues to find applications from molecular biology and chemistry to environmental and food sciences. In search of reliable and affordable SERS substrates, the development has moved from noble metals to other diverse types of structures, e.g., nano-engineered semiconductor materials, but the cost of the enhancement factors (EF) substantially decreasing. In this work, we employ biocompatible thin films of Ti-Si-Zr-Zn nanometallic glasses as the SERS substrates, while tuning the Zn composition. Aided by quartz crystal microbalance, we find that the composition of 4.3% Zn (Ti-Si-Zr-Zn4.3) gives an ultrasensitive detection of Cytochrome c (Cyt c) with an EF of 1.38 × 104, 10-fold higher than the previously reported EF in the semiconducting metal oxide nanomaterials, such as TiO2, and even comparable to the reported noble-metal-assisted semiconducting tungsten oxide hydrate. Ti-Si-Zr-Zn4.3 exhibits a stronger adhesion force toward Cyt c, which ensures the strong binding of Cyt c to the surface, facilitating the Cyt c adsorption onto the surface and thus enhancing the SERS signal. The high separation efficiency of photoinduced electrons and holes in Ti-Si-Zr-Zn4.3 is also acknowledged for promoting the SERS activity.

Arsenic in groundwater of the Poyang Lake area (China): aqueous species and health risk assessment.

Arsenic is a pervasive pollutant in groundwater, affecting more than 100 million people in 50 countries, including China. Toxicological analysis of As is complicated because As exists in the environment in a variety of forms and redox states. Here, a thermodynamic equilibrium model was used to calculate As speciation, investigate pathways of As accumulation and assess the risk of adverse health effects from oral ingestion of dissolved As from shallow groundwater in the Poyang Lake area (China). The accumulation of As, Fe, and NH4+ in the studied shallow groundwater was found to be the result of the dissolution of As-containing Fe, and probably Mn, (oxyhydr)oxides under reducing conditions due to excess influx of organic matter into the shallow aquifer. Modeling showed that As(III), which is more toxic than As(V), predominated at nearly all sampling sites, regardless of redox conditions. Arsenic tends to accumulate in the highest concentrations as neutral species (As(OH)30, HAsO20) under Eh < 50 mV. In the lower reaches of the Ganjiang and Xiushui Rivers, an increased non-carcinogenic risk from oral ingestion of As from drinking water was observed. The elevated cancer risk was found to be present throughout the study area. The lower reaches of the Ganjiang and Xiushui Rivers that have been shown to have the highest risk of both non-carcinogenic and carcinogenic adverse health effects are associated with more toxic As(III) species. Given the As speciation and risk profile, it is recommended to introduce strategies to alter redox conditions in shallow groundwater by adopting safer irrigation practices and managing fertilizer applications to avoid the buildup of high As concentrations associated with adverse health effects.

Dehydration does not affect lipid-based hydration lubrication.

Phosphatidylcholine (PC) lipid bilayers at surfaces massively reduce sliding friction, via the hydration lubrication mechanism acting at their highly-hydrated phosphocholine headgroups, a central paradigm of biological lubrication, particularly at articular cartilage surfaces where low friction is crucial for joint well-being. Nanotribological measurements probed the effect on such lubrication of dehydration by dimethyl sulfoxide (DMSO), known to strongly dehydrate the phosphocholine headgroups of such PC bilayers, i.e. reduce the thickness of the inter-bilayer water layer, and thus expected to substantially degrade the hydration lubrication. Remarkably, and unexpectedly, we found that the dehydration has little effect on the friction. We used several approaches, including atomic force microscopy, small- and wide-angle X-ray scattering and all-atom molecular dynamics simulations to elucidate this. Our results show that while DMSO clearly removes hydration water from the lipid head-groups, this is offset by both higher areal head-group density and by rigidity-enhancement of the lipid bilayers, both of which act to reduce frictional dissipation. This sheds strong light on the robustness of lipid-based hydration lubrication in biological systems, despite the ubiquitous presence of bio-osmolytes which compete for hydration water.

[Antibiotic Pollution Characteristics and Ecological Risk Assessment in Jinjiang River Basin, Jiangxi Province].

The concentration and distribution characteristics of 27 antibiotics, including 8 sulfonamides, 9 quinolones, 4 tetracyclines, 4 macrolides, and 2 nitroimidazoles, in the surface water, groundwater, and wastewater of the Jinjiang River basin in Jiangxi province were determined using solid-phase extraction combined with ultra-performance liquid chromatography-tandem triple quadrupole mass spectrometry. The results showed that there was antibiotic pollution in the waters of the Jinjiang River basin. A total of 20 antibiotics were detected in the surface water, with a concentration range of 32.3-280 ng·L-1. There were 15 types of antibiotics detected in the groundwater, and the concentration range was 28.4-55.8 ng·L-1. Twenty-one types of antibiotics were detected in the wastewater, with a concentration range of 231-8.71×104 ng·L-1. A comparison with the concentrations of eight common antibiotics in rivers and lakes in China and abroad showed that the pollution level in the Jinjiang River basin was at a medium level. By comparing the concentrations of sulfamethoxazole in groundwater from domestic and international samples, the groundwater pollution in the Jinjiang River basin was clearly in the middle and lower range. A comparison of the concentrations of the three antibiotics in the aquaculture wastewater from domestic and abroad samples indicated that the pollution level of sulfadiazine in the aquaculture wastewater from the Jinjiang River basin was relatively high. The ecological risk assessment results showed that there were nine medium- and high-risk antibiotics, which were clarithromycin, erythromycin, ciprofloxacin, sulfathiazole, roxithromycin, tetracycline, ofloxacin, enrofloxacin, and sulfamethoxazole; the rest were low-risk or no-risk antibiotics.

Phosphonium-Based Ionic Liquid Significantly Enhances SERS of Cytochrome c on TiO2 Nanotube Arrays.

Surface-enhanced Raman scattering (SERS) is an attractive technique for studying trace detection. It is of utmost importance to further improve the performance and understand the underlying mechanisms. An ionic liquid (IL), the anion of which is derived from biomass, [P6,6,6,14][FuA] was synthesized and used as a trace additive to improve the SERS performance of cytochrome c (Cyt c) on TiO2 nanotube arrays (TNAs). An increased and better enhancement factor (EF) by four to five times as compared to the system without an IL was obtained, which is better than that from using the choline-based amino acid IL previously reported by us. Dissociation of the ILs improved the ionic conductivity of the system, and the long hydrophobic tails of the [P6,6,6,14]+ cation contributed to a strong electrostatic interaction between Cyt c and the TNA surface, thereby enhancing the SERS performance. Atomic force microscopy did verify strong electrostatic interactions between the Cyt c molecules and TNAs after the addition of the IL. This work demonstrates the importance of introducing the phosphonium-based IL to enhance the SERS performance, which will stimulate further development of more effective ILs on SERS detection and other relevant applications in biology.

Molecular interactions of ionic liquids with SiO2 surfaces determined from colloid probe atomic force microscopy.

Ionic liquids (ILs) interact strongly with many different types of solid surfaces in a wide range of applications, e.g. lubrication, energy storage and conversion, etc. However, due to the nearly immeasurable large number of potential ILs available, identifying the appropriate ILs for specific solid interfaces with desirable properties is a challenge. Theoretical studies are highly useful for effective development of design and applications of these complex molecular systems. However, obtaining reliable force field models and interaction parameters is highly demanding. In this work, we apply a new methodology by deriving the interaction parameters directly from the experimental data, determined by colloid probe atomic force microscopy (CP-AFM). The reliability of the derived interaction parameters is tested by performing molecular dynamics simulations to calculate translational self-diffusion coefficients and comparing them with those obtained from NMR diffusometry.

Complementary Powerful Techniques for Investigating the Interactions of Proteins with Porous TiO2 and Its Hybrid Materials: A Tutorial Review.

Understanding the adsorption and interaction between porous materials and protein is of great importance in biomedical and interface sciences. Among the studied porous materials, TiO2 and its hybrid materials, featuring distinct, well-defined pore sizes, structural stability and excellent biocompatibility, are widely used. In this review, the use of four powerful, synergetic and complementary techniques to study protein-TiO2-based porous materials interactions at different scales is summarized, including high-performance liquid chromatography (HPLC), atomic force microscopy (AFM), surface-enhanced Raman scattering (SERS), and Molecular Dynamics (MD) simulations. We expect that this review could be helpful in optimizing the commonly used techniques to characterize the interfacial behavior of protein on porous TiO2 materials in different applications.

Selective Separation of Highly Similar Proteins on Ionic Liquid-Loaded Mesoporous TiO2.

Separating proteins from their mixtures is an important process in a great variety of applications, but it faces difficult challenges as soon as the proteins are simultaneously of similar sizes and carry comparable net charges. To develop both efficient and sustainable strategies for the selective separation of similar proteins and to understand the underlying molecular mechanisms to enable the separation are crucial. In this work, we propose a novel strategy where the cholinium-based amino acid [Cho][Pro] ionic liquid (IL) is used as the trace additive and loaded physically on a mesoporous TiO2 surface for separating two similar proteins (lysozyme and cytochrome c). The observed selective adsorption behavior is explained by the hydration properties of the [Cho][Pro] loaded on the TiO2 surface and their partially dissociated ions under different pH conditions. As the pH is increased from 5.0 to 9.8, the degree of hydration of IL ions also increases, gradually weakening the interaction strength of the proteins with the substrates, more for lysozymes, leading to their effective separation. These findings were further used to guide the detection of the retention behavior of a binary mixture of proteins in high-performance liquid chromatography, where the introduction of ILs did effectively separate the two similar proteins. Our results should further stimulate the use of ILs in the separation of proteins with a high degree of mutual similarity.

NLRP3 promotes immune escape by regulating immune checkpoints: A pan-cancer analysis.

NLRP3 plays a pathogenic role in tumorigenesis by regulating innate and acquired immunity, apoptosis, differentiation, and intestinal microbes in tumors. Our research aimed to investigate the role of NLRP3 in pan-cancers based on multi-omics data in the TCGA database. Most types of tumors showed increased expression of NLRP3. Among them, the overexpressed NLRP3 in liver hepatocellular carcinoma (LIHC) and ovarian cancer (OV) indicated worse overall survival (OS). Further analysis also confirmed overexpressed NLRP3 in colon cancer (COAD) indicated a high probability of microsatellite instability (MSI) and low tumor mutational burden (TMB), which indicated a better response to immune checkpoint inhibitors (ICIs). Interestingly, overexpression of NLRP3 was closely related to high infiltration of immune cells (T cells, B cells, etc.) and overexpressed immune checkpoints (PD-1, PD-L1, LAG3, etc.). These results demonstrated NLRP3 promoted immune escape in cancers. Finally, we investigated the expression of various immune checkpoints by treating NLRP3 inhibitor MCC950 during the co-culture of peripheral blood mononuclear cells (PBMC) and LIHC cell line Hep3B. MCC950 significantly repressed the expression of PD-L1 and LAG3, and promoted the apoptosis rate of Hep3B. In conclusion, our research demonstrated the role of NLRP3 in pan-cancer, especially in LIHC. Inhibition of NLRP3 promoted the killing effect of T cells to cancer cells by repressing the expression of immune checkpoints.

Value of Neutrophil to Lymphocyte Ratio, Platelet to Lymphocyte Ratio, and Red Blood Cell Distribution Width in Evaluating the Prognosis of Children with Severe Pneumonia.

OBJECTIVE: To investigate the value of neutrophil to lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR), and red blood cell distribution width (RDW) in evaluating the prognosis of children with severe pneumonia (SP). METHODS: A retrospective analysis of the data of 91 children with SP admitted to our hospital from March 2018 to March 2021. According to the survival status after 28 days of treatment, all children were divided into the survival group (n = 59) and the death group (n = 32). The clinical data and laboratory indicators of the patients were recorded. Multivariate logistic regression was used to analyze the risk factors of prognosis, and the ROC curve was used to analyze the predictive value of each index. RESULTS: The Acute Physiology and Chronic Health Evaluation II (APACHE II) score and CURB-65 score of the death group were higher than those of the survival group (P < 0.05). The RDW, NLR, PLR, and high-sensitivity C-reactive protein, procalcitonin blood lactic acid (Lac) of the death group, were higher than those of the survival group, and LYM was lower than the survival group (P < 0.05). Multivariate regression analysis showed that APACHE II score, RDW, NLR, PLR, and Lac were all independent risk factors for poor prognosis in children with SP (P < 0.05). The AUC of NLR, PLR, and RDW for evaluating the prognosis of children with SP were 0.798, 0.781, and 0.777, respectively. The sensitivity was 56.25%, 90.63%, and 56.25%, respectively, and the specificity was 89.83%, 55.93%, and 91.53%, respectively. The AUC of NLR, PLR, and RDW combined to evaluate the prognosis of children with SP was 0.943. When the best cut-off value was 0.8528, the sensitivity was 93.75%, and the specificity was 91.53%. CONCLUSION: NLR, PLR, and RDW have certain predictive value for the prognosis of children with SP; the combination of the three indicators has a higher value in evaluating the prognosis of children with SP, which can better guide the prognostic treatment.

Molecular Mechanistic Insights into the Ionic-Strength-Controlled Interfacial Behavior of Proteins on a TiO2 Surface.

By adjusting the ionic strengths through changing the concentration of the buffer ions, the molecular force and the interfacial behavior of cytochrome c (Cyt c) and TiO2 are systematically studied. The molecular forces determined by combining the adhesion force and adsorption capacity are found to first increase and then decrease with the increasing ionic strength, with a peak obtained at an ionic strength between 0.8 and 1.0 M. The mechanism is explained based on the dissociation and hydration of ions at the interfaces, where the buffer ions could be completely dissociated at ionic strengths of <0.8 M but were partially associated when the ionic strength increased to a high value (>1.2 M), and the strongest hydration was observed around 1.0 M. The hydrodynamic size and the zeta potential value representing the effective contact area and protein stability of the Cyt c molecule, respectively, are also affected by the hydration and are proportional to the molecular forces. The interfacial behavior of Cyt c molecules on the TiO2 surface, determined through surface-enhanced Raman scattering (SERS), is extremely affected by the ionic strength of the solution as the ion dissociation and hydration also increase the electron transfer ability, where the best SERS enhancement is observed at the ionic strength of around 1.0 M, corresponding to the largest molecular force. Our results provide a detailed understanding at the nanoscale on controlling the protein interfacial behavior with solid surfaces, adjusted by the buffer ions.

Hydrated Ionic Liquids Boost the Trace Detection Capacity of Proteins on TiO2 Support.

Trace detection based on surface-enhanced Raman scattering (SERS) has attracted considerable attention, and exploiting efficient strategies to stretch the limit of detection and understanding the mechanisms on molecular level are of utmost importance. In this work, we use ionic liquids (ILs) as trace additives in a protein-TiO2 system, allowing us to obtain an exceptionally low limit of detection down to 10-9 M. The enhancement factors (EFs) were determined to 2.30 × 104, 6.17 × 104, and 1.19 × 105, for the three systems: one without ILs, one with ILs in solutions, and one with ILs immobilized on the TiO2 substrate, respectively, corresponding to the molecular forces of 1.65, 1.32, and 1.16 nN quantified by the atomic force microscopy. The dissociation and following hydration of ILs, occurring in the SERS system, weakened the molecular forces but instead improved the electron transfer ability of ILs, which is the major contribution for the observed excellent detection. The weaker diffusion of the hydrated IL ions immobilized on the TiO2 substrate did provide a considerably greater EF value, compared to the ILs in the solution. This work clearly demonstrates the importance of the hydration of ions, causing an improved electron transfer ability of ILs and leading to an exceptional SERS performance in the field of trace detection. Our results should stimulate further development to use ILs in SERS and related applications in bioanalysis, medical diagnosis, and environmental science.

Nitrogen transformation and pathways in the shallow groundwater-soil system within agricultural landscapes.

The present study considers the behavior of nitrogen compounds in the shallow groundwater-soil system as necessary for the functioning of the nitrogen cycle within agricultural landscapes and one of the first steps of the formation of groundwater chemical composition. Data were collected in 2011-2018 within the Poyang Lake area (Jiangxi Province, China), where agricultural landscapes prevail. The soil and groundwater samples were taken in different periods of an agricultural season at the beginning of the agricultural season (spring) and after harvesting (autumn). The combined geochemical data on the chemical and microbiological composition of the soils and shallow groundwater and isotopic data on dissolved nitrate allowed researchers to resolve that nitrogen enters the system in the form of organic compounds, particularly, due to the soil fertilization at the beginning of the agricultural season. Organic nitrogen compounds transform into nitrate under the influence of nitrifiers in the soil before getting the shallow aquifer, where the occurrence of denitrification is suggested. Within the Ganjiang and Xiushui interfluve, reducing conditions, together with the formation of clay minerals from the aqueous solution, may serve a geochemical barrier for the accumulation of nitrogen compounds preventing the transformation of ammonium to nitrate and providing its sorption. It also should be noted that bacterial diversity in the shallow groundwater has a strong relation with the amount of nitrate in the system, whereas in the soil, it is connected with sampling depth.

Excellent Protein Immobilization and Stability on Heterogeneous C-TiO2 Hybrid Nanostructures: A Single Protein AFM Study.

Enhancing molecular interaction is critical for improving the immobilization and stability of proteins on TiO2 surfaces. In this work, mesoporous TiO2 materials with varied pore geometries were decorated with phenyl phosphoric acid (PPA), followed by a thermal treatment to obtain chemically heterogeneous C-TiO2 samples without changing the geometry and crystalline structure, which can keep the advantages of both carbon and TiO2. The molecular interaction force between the protein and the surfaces was measured using atomic force microscopy by decomposing from the total adhesion forces, showing that the surface chemistry determines the interaction strength and depends on the amount of partial carbon coverage on the TiO2 surface (∼40-80%). Samples with 58.3% carbon coverage provide the strongest molecular interaction force, consistent with the observation from the detected friction force. Surface-enhanced Raman scattering and electrochemical biosensor measurements for these C-TiO2 materials were further conducted to illustrate their practical implications, implying their promising applications such as in protein detection and biosensing.

Mechanistic Study of Protein Adsorption on Mesoporous TiO2 in Aqueous Buffer Solutions.

Protein adsorption is of fundamental importance for bioseparation engineering applications. In this work, a series of mesoporous TiO2 with various geometric structures and different aqueous buffer solutions were prepared as platforms to investigate the effects of the surface geometry and ionic strength on the protein adsorptive behavior. The surface geometry of the TiO2 was found to play a dominant role in the protein adsorption capacity when the ionic strength of buffer solutions is very low. With the increase in ionic strength, the effect of the geometric structure on the protein adsorption capacity reduced greatly. The change of ionic strength has the highest significant effect on the mesoporous TiO2 with large pore size compared with that with small pore size. The interaction between the protein and TiO2 measured with atomic force microscopy further demonstrated that the adhesion force induced by the surface geometry reduced with the increase in the ionic strength. These findings were used to guide the detection of the retention behavior of protein by high-performance liquid chromatography, providing a step forward toward understanding the protein adsorption for predicting and controlling the chromatographic separation of proteins.

Determination of the small amount of proteins interacting with TiO2 nanotubes by AFM-measurement.

Detecting the small amounts of proteins interacting effectively with the solid film electrodes surface still remains a challenge. To address this, in this work, a new approach was proposed by the combination of the adhesion forces and the molecular interaction measured with AFM. Cytochrome c (Cyt C) interacting effectively with TiO2 nanotube arrays (TNAs) was chosen as a probe. The amounts of Cyt C molecules interacting effectively on TNAs surface (CTNA) range from 5.5×10-12 to 7.0×10-12 mol/cm2 (68.2-86.8 ng/cm2) and they are comparable with the values obtained by the electrochemistry method in the literature, in evidence of the accuracy of this AFM-based approach. The reliability of the proposed approach was further verified by conducting Surface Enhanced Raman Scattering (SERS) measurements and estimating the enhancement factor (EF). This interaction-based AFM approach can be used to accurately obtain the small amounts of adsorbed substances on the solid film electrodes surface in the applications such as biosensors, biocatalysis, and drug delivery, etc.

Molecular Interactions of Protein with TiO2 by the AFM-Measured Adhesion Force.

Understanding the interactions between porous materials and biosystems is of great important in biomedical and environmental sciences. Upon atomic force microscopy (AFM) adhesion measurement, a new experimental approach was presented here to determine the molecular interaction force between proteins and mesoporous TiO2 of various surface roughnesses. The interaction force between each protein molecule and the pure anatase TiO2 surface was characterized by fitting the adhesion and adsorption capacity per unit contact area, and it was found that the adhesion forces were approximately 0.86, 2.63, and 4.41 nN for lysozyme, myoglobin, and BSA, respectively. Moreover, we reported that the molecular interaction force was independent of the surface topography of the material but the protein type is a factor of the interaction. These experimental results on the molecular level provide helpful insights for stimulating model calculation and molecular simulation studies of protein interaction with surfaces.