Construction of dual active sites on the CuAg plasmonic aerogel for simultaneously efficient photocatalytic CO2 reduction and H2 production.

Photocatalytic CO2 reduction and H2 production are a competitive reaction, and existing active sites cannot take into account the simultaneous gas-solid and liquid-solid reaction processes. Hence, a metallic aerogel (CuAg2.5) with dual active sites was constructed via straightforward in-situ reduction process. CuAg2.5 aerosol has larger porosity and CO2 adsorption capacity, which enables H2O and CO2 to fully contact it. The CuAg2.5 can also construct the cooperative dual active sites, which can conduct CO2 reduction reaction on Ag surface and proton reduction reaction on Cu surface, respectively, thereby efficiently guiding the rapid migration of photogenerated carriers. The yields of CO (18533 µmol g-1) and H2 (20340 µmol g-1) for CuAg2.5 are much higher than those of single metals. The ratio of CO and H2 can also regulated via changing the ratio of Ag and Cu. This work gives new insights into the fabrication of unique high-efficiency plasmonic photocatalysts.

Fast synthesis of porous iron doped CeO2 with oxygen vacancy for effective CO2 photoreduction.

The activity of photocatalytic CO2 conversion to carbon-containing products is determined by the adsorption and activation of CO2 molecules on the surface of catalyst. Here, iron doped porous CeO2 with oxygen vacancy (PFeCe) was prepared by one-step combustion method. The amount of CO2 adsorbed via using the porous structure has been significantly increased in the case of a relatively small specific surface area and CO2 molecules are more easily captured and undergo a reduction reaction with photoinduced carriers. In addition, oxygen vacancies are formed in the iron doped CeO2 lattice as the active sites for CO2 reduction, which can form strong interactions with CO2 molecules, thereby effectively activating CO2 molecules. The reduction products of CO2 over PFeCe composite are CO and CH4, which is approximately 9.0 and 7.7 folds than that of CeO2. This work offers insights for the construction of efficient ceria-based photocatalysts to further achieve robust solar CO2 conversion.

A Universal Positioning System for Coupling Characterization of SEM and AFM.

Hyphenated techniques, providing comprehensive information in various aspects such as constituent, structure, functional group, and morphology, play an important role in scientific research. Nowadays, coupling characterization of the same position in microscale is in great need in the field of nanomaterial research and exploration. In this article, a new hyphenated technique was developed to facilitate the coupling characterization of atomic force microscope (AFM) and scanning electron microscope (SEM) by designing a universal positioning system. The system consisted of a specimen holder with coordinate grids and a software for converting the coordinate values of the same point to fit SEM, specimen holder, and AFM system. In working condition, the coordinates of the labeled points and target position were firstly extracted from the SEM operation software, then converted into the numerical values adapted to the specimen holder itself, and finally transformed into the coordinates matching the AFM system. The experimental result showed that a retrieving rate of 96% was achieved for a spherical target with a diameter of 1 µm in a 30 µm × 30 µm square. The hyphenated technique is a universal, accurate, efficient, and financially feasible method in microanalysis field and has great application potential.

Strong adsorption of tetracycline hydrochloride on magnetic carbon-coated cobalt oxide nanoparticles.

The overuse of antibiotics, including tetracycline hydrochloride (TC), seriously threatens human health and ecosystems. In this work, magnetic carbon-coated cobalt oxide nanoparticles (CoO@C) were prepared by one-step annealing method and used as an adsorbent for efficient removal of TC from aqueous solution. The characteristic of the materials was studied by SEM, TEM, and XRD, revealing CoO nanoparticles (≤10 nm) were coated by carbon layer. Several influencial parameters, such as annealing temperature and pH on adsorption of TC, were explored, and found that the maximum adsorption capacity of CoO@C on TC reached as high as 769.43 mg g-1. Furthermore, CoO@C displayed excellent stability and reusability. After four repeated use of the adsorbent, the adsorption capacity still remained at 90% of the initial capacity. The pseudo-second order model and Temkin model proved that it was an exothermic chemical adsorption process. Furthermore, after analysis of FT-IR, Zeta-potential, XPS, the positive charge on the surface of CoO@C forms a strong electrostatic interaction with TC, and in addition, a surface bond is formed between the adsorbent and the TC molecule. This work provides a novel and efficient adsorbent for the purification of TC-containing wastewater.

Blood Circulation-Prolonging Peptides for Engineered Nanoparticles Identified via Phage Display.

Sustaining blood retention for theranostic nanoparticles is a big challenge. Various approaches have been attempted and have demonstrated some success but limitations remain. We hypothesized that peptides capable of increasing blood residence time for M13 bacteriophage, a rod-shaped nanoparticle self-assembled from proteins and nucleic acids, should also prolong blood circulation for engineered nanoparticles. Here we demonstrate the feasibility of this approach by identifying a series of blood circulation-prolonging (BCP) peptides through in vivo screening of an M13 peptide phage display library. Intriguingly, the majority of the identified BCP peptides contained an arginine-glycine-aspartic acid (RGD) motif, which was necessary but insufficient for the circulation-prolonging activity. We further demonstrated that the RGD-mediated specific binding to platelets was primarily responsible for the enhanced blood retention of BCP1. The utility of the BCP1 peptide was demonstrated by fusion of the peptide to human heavy-chain ferritin (HFn), leading to significantly improved pharmacokinetic profile, enhanced tumor cell uptake and optimum anticancer efficacy for doxorubicin encapsulated in the HFn nanocage. Our results provided a proof-of-concept for an innovative yet simple strategy, which utilizes phage display to discover novel peptides with the capability of substantially prolonging blood circulation for engineered theranostic nanoparticles.

Surface characteristics and biocompatibility of sandblasted and acid-etched titanium surface modified by ultraviolet irradiation: an in vitro study.

Sandblasting with large grit and acid-etching (SLA) treatment is considered to be a reliable modification to achieve excellent titanium surface. However, contamination of hydrocarbons would make SLA surface hydrophobic and influence its bioactivity. Thus, appropriate methods of preservation or further treatments could be used for improvement. In present study, preservation in deionized water (dH(2)O) and ultraviolet (UV) irradiation were, respectively, applied to achieve modSLA and UV-SLA surfaces. Surface characteristics were assessed by scanning electron microscopy, optical profilometer and x-ray photoelectron spectroscopy as well as wettability by optical contact angle analyzer. Additionally, biocompatibility was evaluated by the response to osteoblast-like MG63 cells. Prevented from further contamination, modSLA surface with fewer hydrocarbons (25.31%) remained hydrophilic and showed better affinity to mineralization of MG63 cells than hydrophobic polluted SLA surface (p < 0.01). Furthermore, with the lowest content of hydrocarbons (14.26%) and super-hydrophilicity, UV-SLA surface, which had the hydrocarbons effectively decomposed by photocatalysis and meanwhile acquired abundant hydroxyl groups, had most greatly promoted the attachment, proliferation, differentiation, and mineralization of MG63 cells (p < 0.05). Therefore, hydrocarbons were found to be an important influencing factor to compatibility of biomaterials. In addition, UV irradiation was recognized as a trustworthy method for surface cleaning without change of topography and roughness and could ever lead to greater biocompatibility of sandblasted and acid-etched titanium surface.

Characterization and biocompatibility of nanohybrid scaffold prepared via in situ crystallization of hydroxyapatite in chitosan matrix.

Hydroxyapatite (HAP) precursor solution was first mixed with an acetic acid chitosan (CS) solution. The mixture was then lyophilized to form the original scaffold, which stored the HAP precursors. The nano HAP crystallized homogeneously from the CS matrix during the alkaline treatment to form a nanohybrid scaffold. Scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) were used to investigate the fabrication process of the nanohybrid scaffold. XRD results showed that the in situ deposited mineral (HAP) in the scaffold has phase structure similar to natural bone. FTIR and XPS results indicated that CS's hydroxyl group, amino and amide regulated the nano HAP crystallization process, which resulted in the nano homogeneous distribution of nano HAP and provided nano topographical features for the nanohybrid scaffold. MTT testing and SEM images of human bone mesenchymal stem cells (hBMSCs) cultures revealed the attachment and growth of hBMSCs in the biocomposite scaffold. Cell morphology and viability data showed that the nanohybrid composite scaffold is suitable for use in bioapplications.

[Studies on poly-D, L-lactide acid scaffolds modified by conjugation of bioactive peptides via ammonia plasma treatment].

OBJECTIVE: To study the feasibility of preparation of the poly-D, L-lactide acid (PDLLA) scaffolds treated by ammonia plasma and subsequent conjugation of Gly-Arg-Gly-Asp-Ser (GRGDS) peptides via amide linkage formation. METHODS: PDLLA scaffolds (8 mm diameter, 1 mm thickness) were prepared by solvent casting/particulate leaching procedure and then treated by ammonia plasma. The consequent scaffolds were labeled as aminated PDLLA (A/PDLLA). The pore size, porosity, and surface water contact angle of groups 0 (un-treated control), 5, 10, and 20 minutes A/PDLLA were measured. A/PDLLA scaffolds in groups above were immersed into the FITC labelled GRGDS aqueous solution which contain 1-[3-(dimethylamino) propyl]-3-ethylcarbodiimide hydrochloride (EDC-HCl) and N-hydroxysuccinimide (NHS), the molar ratio of peptides/EDC*HCL/NHS was 1.5 : 1.5 : 1.0, then brachytely slashed for 24 hours in room temperature. The consequent scaffolds were labelled as peptides conjugated A/PDLLA (PA/PDLLA). The scaffolds in groups 0, 5, 10, and 20 minutes A/PDLLA and groups correspondingly conjugation of peptides were detected using X-ray photoelectron spectroscopy (XPS). The scaffolds in groups of conjugation of peptides were measured by confocal laser scanning microscope and high performance liquid chromatography (HPLC), un-treated and un-conjugated scaffolds employed as control. Bone marrow mesenchymal stem cells (BMSCs) from SD rats were isolated and cultured by whole bone marrow adherent culture method. BMSCs at the 3rd-6th passages were seeded to the scaffolds as follows: 20 minutes ammonia plasma treatment (group A/PDLLA), 20 minutes ammonia plasma treatment and conjugation of GRGDS (group PA/PDLLA), and untreated PDLLA control (group PDLLA). After 16 hours of culture, the adhesive cells on scaffolds and the adhesive rate were calculated. After 4 and 8 days of culture, the BMSCs/scaffold composites was observed by scanning electron microscope (SEM). RESULTS: No significant difference in pore size and porosity of PDLLA were observed between before and after ammonia plasma treatments (P > 0.05). With increased time of ammonia plasma treatment, the water contact angle of A/PDLLA scaffolds surface was decreased, and the hydrophilicity in the treated scaffolds was improved gradually, showing significant differences when these groups were compared with each other (P < 0.001). XPS results indicated that element nitrogen appeared on the surface of PDLLA treated by ammonia plasma. With time passing, the peak N1s became more visible, and the ratio of N/C increased more obviously. After PDLLA scaffolds treated for 0, 5, 10, and 20 minutes with ammonia plasma and subsequent conjugation of peptides, the ratio of N/C increased and the peak of S2p appeared on the surface. The confocal laser scanning microscope observation showed that the fluorescence intensity of PA/PDLLA scaffolds increased obviously with treatment time. The amount of peptides conjugated for 10 minutes and 20 minutes PA/PDLLA was detected by HPLC successfully, showing significant differences between 10 minutes and 20 minutes groups (P < 0.001). However, the amount of peptides conjugated in un-treated control and 0, 5 minutes PA/PDLLA scaffolds was too small to detect. After 16 hours co-culture of BMSCs/scaffolds, the adhesive cells and the adhesive rates of A/PDLLA and PA/PDLLA scaffolds were higher than those of PDLLA scaffolds, showing significant difference between every 2 groups (P < 0.01). Also, SEM observation confirmed that BMSCs proliferation in A/PDLLA and PA/PDLLA groups was more detectable than that in PDLLA group, especially in PA/PDLLA group. CONCLUSION: Ammonia plasma treatment will significantly increase the amount of FITC-GRGDS peptides conjugated to surface of PDLLA via amide linkage formation. This new type of biomimetic bone has stabilized bioactivities and has proved to promote the adhesion and proliferation of BMSCs in PDLLA.

A study on the performance of hyaluronic acid immobilized chitosan film.

In order to improve hydrophilicity and biocompatibility of chitosan, hyaluronic acid was immobilized onto the surface of chitosan film. The structure of films was characterized by Fourier transformed infrared spectroscopy with attenuated total reflectance (ATR-FTIR), x-ray photoelectron spectroscopy (XPS) and zeta potential. Results confirmed that hyaluronic acid was successfully immobilized on chitosan film. Transparency, water absorption percentage and contact angle of films were characterized. Results showed that there was no significant variation in transparency (p < 0.05) before and after immobilization, the maximum was up to 99% which was enough for corneal regeneration in clinical applications. After the immobilization, the time-dependent contact angle declined sharply (from 91.8 degrees to 67.7 degrees at 100 s). The hydrophilicity was significantly improved. The methylthiazol tetrazolium (MTT) (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay was used to assess cell viability and proliferation. Results showed that human cornea epithelial cells (HCEC) grew better on hyaluronic acid immobilized chitosan films than on chitosan films. The hyaluronic acid immobilized chitosan film could be a promising candidate material for corneal regeneration.

Surface characterization of the chitosan membrane after oxygen plasma treatment and its aging effect.

Chitosan has received considerable attention for biomedical applications in recent years because of its biocompatibility and biodegradability. In this paper, angle-resolved x-ray photoelectron spectroscopy (ARXPS) was carried out to investigate the chemical groups' spatial orientation on the chitosan membrane surface. Oxygen plasma treatment was also employed to improve the surface hydrophilicity of the chitosan membrane. The results of ARXPS revealed the distribution of surface polar groups, such as-OH and O=CNH(2) toward the membrane bulk, which was the origin of the chitosan membrane surface hydrophobicity. The contact angle measurements and XPS results indicated that oxygen plasma treatment can markedly improve the surface hydrophilicity and surface energy of the chitosan membrane by incorporating oxygen-containing polar groups. With the existence of the aging process, the influence of plasma treatment was not permanent, it faded with storage time. The ARXPS result discovered that the reorientation of polar functional groups generated by plasma treatment toward the membrane bulk was primarily responsible for the aging effect.