Polymer nanostructures for bioapplications induced by laser treatment

Modification of polymer substrates can essentially change the properties of material and thereby it allows their usage in attractive fields of material research. Laser treatment can be successfully applied for change in physico-chemical surface properties and/or for selective change of surface morphology with pattern construction. Three major applications of laser induced structures were described, cytocompatibility control, application as anti-bacterial substrate and plasmonic-based detection system. The construction of a second generation antibacterials using the synergic effect of either nanopatterning of polymers by application of a laser or noble metals deposition and consequent modification of nanostructures was presented.     

Amplified electrochemical aptasensor for thrombin based on bio-barcode method

In the present study, an electrochemical aptasensor for highly sensitive detection of thrombin was developed based on bio-barcode amplification assay. For this proposed aptasensor, capture DNA aptamerI was immobilized on the Au electrode. The functional Au nanoparticles (DNA–AuNPs) are loaded with barcode binding DNA and aptamerII. Through the specific recognition for thrombin, a sandwich format of Au/aptamerI/thrombin/DNA–AuNPs was fabricated. After hybridization with the PbSNPs-labeled barcode DNA, the assembled sensor was obtained. The concentration of thrombin was monitored based on the concentration of lead ions dissolved through differential pulse anodic stripping voltammetric (DPASV). Under optimum conditions, a detection limit of 6.2 × 10⁻¹⁵ mol L⁻¹ (M) thrombin was achieved. In addition, the sensor exhibited excellent selectivity against other proteins.     

A mediator-free amperometric hydrogen peroxide biosensor based on HRP immobilized on a nano-Au/poly 2,6-pyridinediamine-coated electrode

A mediator-free amperometric hydrogen peroxide biosensor was prepared by immobilizing horseradish peroxidase (HRP) enzyme on colloidal Au modified platinum (Pt) wire electrode, which was modified by poly 2,6-pyridinediamine (pPA). The modified process was characterized by electrochemical impedance spectroscopy (EIS), and the electrochemical characteristics of the biosensor were studied by cyclic voltammetry, linear sweep voltammetry and chronoamperometry. The biosensor displayed an excellent electrocatalytical response to reduction of H₂O₂ without the aid of an electron mediator, the linear range was 4.2 × 10⁻⁷–1.5 × 10⁻³ mol/L (r = 0.9977), with a detection limit of 1.4 × 10⁻⁷ mol/L. Moreover, the performance and factors influencing the resulted biosensor were studied in detail. The studied biosensor exhibited permselectivity, good stability and good fabrication reproducibility.     

Importance of Metal–Adsorbate Interactions for the Surface-enhanced Raman Scattering of Molecules Adsorbed on Plasmonic Nanoparticles

The interaction between adsorbates of different nature and plasmonic nanoparticles is reviewed here on the basis of the work done in our laboratory in the past few years. The paper is structured for analyzing the interaction of adsorbates with metal nanoparticles as function of the interacting atom (O, N, or S) and the adsorbate conformation. In the study of the adsorption of molecular species on metals, it is necessary to take into account that different interaction mechanisms are possible, leading to the existence of different molecular forms (isomers or conformers). These forms can be evidenced by changing the excitation wavelength, due to a resonant selection of these wavelengths. Charge-transfer complexes and electrostatic interactions are the usual driving forces involved in the interaction of adsorbates on metal surfaces when these metallic systems are used in wet conditions. The understanding of the metal–adsorbate interaction is crucial in the surface functionalization of metal surfaces, which has a growing importance in the development of sensing systems or optoelectronic devices. In relation to this, special attention is paid in this work to the study of the adsorption of calixarene host molecules on plasmonic nanoparticles.     

Designable nanoplasmonic biomarkers for direct microscopy cytopathology diagnostics

Direct microscopy interpretation of fine‐needle biopsy cytological samples is routinely used by practicing cytopathologists. Adding possibility to identify selective and multiplexed biomarkers on the same samples and with the same microscopy technique can greatly improve diagnostic accuracy. In this article, we propose to use biomarkers based on designable plasmonic nanoparticles (NPs) with unique optical properties and excellent chemical stability that can satisfy the above‐mentioned requirements. By finely controlling the size and composition of gold‐silver alloy NPs and gold nanorods, the NPs plasmonic resonance properties, such as scattering efficiency and resonance peak spectral position, are adjusted in order to provide reliable identification and chromatic differentiation by conventional direct microscopy. Efficient darkfield NPs imaging is performed by using a novel circular side illumination adaptor that can be easily integrated into any microscopy setup while preserving standard cytopathology visualization method. The efficiency of the proposed technology for fast visual detection and differentiation of three spectrally distinct NP‐markers is demonstrated in different working media, thus confirming the potential application in conventional cytology preparations. It is worth emphasizing that the presented technology does not interfere with standard visualization with immunohistochemical staining, but should rather be considered as a second imaging modality to confirm the diagnostics.      

Synthesis and characterization of CN-modified protein analogues as potential vibrational contrast agents

A recombinant VH single-domain antibody recognizing staphylococcal protein A was functionalized on reactive lysine residues with N-hydroxysuccimidyl-activated 4-cyanobenzoate. Surface plasmon resonance analysis of antibody-antigen binding revealed that modified and unmodified antibodies bound protein A with similar affinities. Raman imaging of the modified antibodies indicated that the benzonitrile group provides vibrational contrast enhancement in a region of the electromagnetic spectrum that is transparent to cellular materials. Thus, the modified single-domain antibody may be amenable to detecting protein A from samples of the human pathogen Staphylococcus aureus using vibronic detection schemes such as Raman and coherent anti-Stokes Raman scattering. The generality of this labeling strategy should make it applicable to modifying an array of proteins with varied structure and function.     

Ultrasensitive chemiluminescence assay for cimetidine detection based on the synergistic improving effect of Au nanoclusters and graphene quantum dots

A novel and sensitive chemiluminescence (CL) procedure based on the synergetic catalytic effects of gold nanoclusters (Au NCs) and graphene quantum dots (GQDs) was developed for the reliable measurement of cimetidine (CM). The initial experiments showed that the KMnO₄‐based oxidation of alkaline rhodamine B (RhoB) generated a very weak CL emission, which was intensively enhanced in the simultaneous presence of Au NCs and GQDs. CL intermediates can be adsorbed and gathered on the surface of Au NCs, becoming more stable. GQDs participate in the energy transferring processes and facilitate them. These improving effects were simultaneously obtained by adding both Au NCs and GQDs into the RhoB‐KMnO₄ reaction. Consequently, the increasing effect of the Au NCs/GQDs mixture was more than that of pure Au NCs or GQDs, and a new nano‐assisted powerful CL system was achieved. Furthermore, a marked quenching in the emission of the introduced CL system was observed in the presence of CM, so the system was examined to design a sensitive sensor for CM. After optimization of influencing parameters, the linear lessening in CL emission intensity of KMnO₄‐RhoB‐Au NCs/GQDs was verified for CM concentrations in the range 0.8–200 ng ml^?1. The limit of detection (3S_b/m) was 0.3 ng ml^?1. Despite being a simple CL method, good sensitivity was obtained for CM detection with reliable results for CM determination in human urine samples.     

对硝基苯硫酚分子内嵌的星形表面增强拉曼散射金 "套娃 "纳米颗粒用于肿瘤拉曼影像的初步研究

目的:制备对硝基苯硫酚(4-Nitrobenzenethiol,4-NBT)分子内嵌的星形表面增强拉曼散射(Surface enhanced Raman Scattering,SERS)金"套娃"纳米颗粒,测定其拉曼增强效果和应用于细胞以及活体肿瘤拉曼影像的可行性。方法:以种子介导法先后制备金纳米星及星形SERS金"套娃"纳米颗粒,采用透射电镜观察其形貌,激光粒度分析仪测定其粒径及Zeta电位,拉曼光谱仪测定其拉曼光谱,考察其对A549细胞的拉曼成像效果,建立A549皮下瘤模型,考察其对活体皮下瘤的成像效果。结果:制备并优化的金纳米星粒径较小,为60.5 nm,其针尖密度较高,以此为核心制备的星形SERS金"套娃"纳米颗粒形态规整,粒径约为66.7nm,Zeta电位约为-16.6 m V,拉曼增强效果提升至其前驱体金纳米星的5.3倍,能够实现对A549细胞及A549皮下瘤的拉曼成像。结论:所制备的星形SERS金"套娃"纳米颗粒形态规整均一,拉曼增强效果较好,能实现对细胞及活体肿瘤的拉曼影像。     

Synthesis of Large Surface‐Area g‐C3N4 Comodified with MnOx and Au‐TiO2 as Efficient Visible‐Light Photocatalysts for Fuel Production

Herein, this study successfully fabricates porous g‐C₃N₄‐based nanocomposites by decorating sheet‐like nanostructured MnO_x and subsequently coupling Au‐modified nanocrystalline TiO₂. It is clearly demonstrated that the as‐prepared amount‐optimized nanocomposite exhibits exceptional visible‐light photocatalytic activities for CO₂ conversion to CH₄ and for H₂ evolution, respectively by ≈28‐time (140 µmol g^?1 h^?1) and ≈31‐time (313 µmol g^?1 h^?1) enhancement compared to the widely accepted outstanding g‐C₃N₄ prepared with urea as the raw material, along with the calculated quantum efficiencies of ≈4.92% and 2.78% at 420 nm wavelength. It is confirmed mainly based on the steady‐state surface photovoltage spectra, transient‐state surface photovoltage responses, fluorescence spectra related to the produced ?OH amount, and electrochemical reduction curves that the exceptional photoactivities are comprehensively attributed to the large surface area (85.5 m² g^?1) due to the porous structure, to the greatly enhanced charge separation and to the introduced catalytic functions to the carrier‐related redox reactions by decorating MnO_x and coupling Au‐TiO₂, respectively, to modulate holes and electrons. Moreover, it is suggested mainly based on the photocatalytic experiments of CO₂ reduction with isotope ¹³CO₂ and D₂O that the produced ?CO₂ and ?H as active radicals would be dominant to initiate the conversion of CO₂ to CH₄.