Aptamer‐Conjugated Nanoparticles Efficiently Control the Activity of Thrombin

Thrombin‐binding aptamer‐conjugated gold nanoparticles (TBA‐Au NPs) for highly effective control of thrombin activity towards fibrinogen are demonstrated. While a 29‐base long oligonucleotide (TBA₂₉) has known no enzymatic inhibitory functions for thrombin‐mediated coagulation, the ultrahigh anticoagulant potency of TBA₂₉‐Au NPs can be demonstrated via the steric blocking effect, at two orders of magnitude higher than that of free TBA₂₉. The surface aptamer density on the Au NPs is important in determining their enzymatic inhibition of thrombin and their stability in the presence of nuclease. The practicality of 100TBA₂₉‐Au NPs (100 TBA₂₉ molecules per Au NP) for controlling thrombin‐mediated coagulation in plasma is found, and the 100TBA₂₉‐Au NPs has an ultra binding affinity towards thrombin (K_d = 2.7 × 10^?11M ) due to their high ligand density. The anticoagulant activity of TBA₂₉‐Au NPs is found to be suppressed by TBA₂₉ complementary sequence (cTBA₂₉) modified Au NPs (cTBA₂₉‐Au NPs), with a suppression rate 4.6‐fold higher than that of cTBA₂₉. The easily prepared and low‐cost TBA₂₉‐Au NPs and cTBA₂₉‐Au NPs show their potential in biomedical applications for treating various diseases related to blood clotting disorders. In principle, this study opens the possibility of regulation of molecule binding, protein recognizing, and enzyme activity by using aptamer‐functionalized nanomaterials.     

Tunable Förster Resonance Energy Transfer in Colloidal Nanoparticles Composed of Polycaprolactone‐Tethered Donors and Acceptors: Enhanced Near‐Infrared Emission and Compatibility for In Vitro and In Vivo Bioimaging

A near‐infrared (NIR) fluorescent donor/acceptor (D/A) nanoplatform based on Förster resonance energy transfer is important for applications such as deep‐tissue bioimaging and sensing. However, previously reported D/A nanoparticles (NPs) often show limitations such as aggregation‐induced fluorescence quenching and poor interfacial compatibility that reduces the efficiency of the energy transfer and also leads to leaching of the small molecular fluorophores from the NP matrix. Here highly NIR‐fluorescent D/A NPs with a fluorescence quantum yield as high as 46% in the NIR region (700–850 nm) and robust optical stability are reported. The hydrophobic core of each NP is composed of donor and acceptor moieties both of which are tethered with polycaprolactone (PCL), while the hydrophilic corona is composed of poly[oligo(ethylene glycol) methyl ether methacrylate] to offer colloidal stability and “stealthy” effect in aqueous media. The PCL matrix in each colloidal NP not only offers biocompatibility and biodegradability but also minimizes the aggregation‐caused fluorescence quenching of D/A chromophores and prevents the leakage of the NIR fluorophores from the NPs. In vivo imaging using these NIR NPs in live mice shows contrast‐enhanced imaging capability and efficient tumor‐targeting through enhanced permeability and retention effect.     

Highly Reproducible Surface‐Enhanced Raman Scattering on a Capillarity‐Assisted Gold Nanoparticle Assembly

A facile method based on capillarity‐assisted assembly is used to fabricate high‐performance surface‐enhanced Raman scattering (SERS) substrates employing clean Au nanoparticles (NPs). This method is better than micro‐channel way because the former may supply large‐area uniform assembly and overcome the uneven radial distribution. Such densely‐arranged assembly of Au NPs exhibits high reproducibility and large Raman enhancement factors of 3 × 10¹⁰, arising from strong electromagnetic field coupling induced by adjacent Au NPs. The spot‐to‐spot SERS signals show that the relative standard deviation (RSD) in the intensity of the main Raman vibration modes (1310, 1361, 1509, 1650 cm^?1) of Rhodamine 6G at a concentration of 1 × 10^?10 M are consistently less than 20%, demonstrating good spatial uniformity and reproducibility. The SERS signals of sudan dye at a 1 × 10^?8 M concentration also shows high reproducibility with a low RSD of <20%. Further, the assembly substrate is stable, retaining excellent uniformity and sensitivity after storage for months. This assembly strategy integrating the advantages of low‐cost production, high sensitivity, and reproducibility would significantly facilitate practical SERS detection.     

Nanoscale Graphene Doped with Highly Dispersed Silver Nanoparticles: Quick Synthesis,Facile Fabrication of 3D Membrane‐Modified Electrode,and Super Performance for Electrochemical Sensing

The performance of graphene‐based hybrid materials greatly depends on the dispersibility of nanoscale building blocks on graphene sheets. Here, a quick green synthesis of nanoscale graphene (NG) nanosheets decorated with highly dispersed silver nanoparticles (AgNPs) is demonstrated, and then the electrospinning technique to fabricate a novel nanofibrous membrane electrode material is utilized. With this technique, the structure, mechanical stability, biochemical functionality, and other properties of the fabricated membrane electrode material can be easily controlled. It is found that the orientations of NG and the dispersity of AgNPs on the surface of NG have significant effects on the properties of the fabricated electrode. A highly sensitive H₂O₂ biosensor is thus created based on the as‐prepared polymeric NG/AgNP 3D nanofibrous membrane‐modified electrode (MME). As a result, the fabricated biosensor has a linear detection range from 0.005 to 47 × 10^?3m (R = 0.9991) with a supralow detection limit of 0.56 × 10^?6m (S/N = 3). It is expected that this kind of nanofibrous MME has wider applications for the electrochemical detection and design of 3D functional nanomaterials in the future.     

Self‐Assembly of Nanoparticle‐Spiked Pillar Arrays for Plasmonic Biosensing

Plasmonic biosensors have demonstrated superior performance in detecting various biomolecules with high sensitivity through simple assays. Scaled‐up, reproducible chip production with a high density of hotspots in a large area has been technically challenging, limiting the commercialization and clinical translation of these biosensors. A new fabrication method for 3D plasmonic nanostructures with a high density, large volume of hotspots and therefore inherently improved detection capabilities is developed. Specifically, Au nanoparticle‐spiked Au nanopillar arrays are prepared by utilizing enhanced surface diffusion of adsorbed Au atoms on a slippery Au nanopillar arrays through a simple vacuum process. This process enables the direct formation of a high density of spherical Au nanoparticles on the 1 nm‐thick dielectric coated Au nanopillar arrays without high‐temperature annealing, which results in multiple plasmonic coupling, and thereby large effective volume of hotspots in 3D spaces. The plasmonic nanostructures show signal enhancements over 8.3 × 10⁸‐fold for surface‐enhanced Raman spectroscopy and over 2.7 × 10²‐fold for plasmon‐enhanced fluorescence. The 3D plasmonic chip is used to detect avian influenza‐associated antibodies at 100 times higher sensitivity compared with unstructured Au substrates for plasmon‐enhanced fluorescence detection. Such a simple and scalable fabrication of highly sensitive 3D plasmonic nanostructures provides new opportunities to broaden plasmon‐enhanced sensing applications.     

Evolution of Light Absorption and Emission Characteristics of Organic Perylene Nanoparticles through Hydrothermal Process: Application to Solar Cells

The evolution of the structural and optical characteristics of polymorphic organic perylene nanoparticles (NPs) is demonstrated by controlling the π–π interactions using a hydrothermal process. The light‐emission colors of the perylene NPs vary gradually from yellow to green to light blue with increasing hydrothermal temperature from 110 to 160 °C. An enhanced crystallinity of the NPs from 110 °C to a critical temperature T_c of 140 °C and a transition to the amorphous phase above T_c are observed. The evolution of the photo‐luminescence (PL) and optical‐absorption characteristics in terms of variations in the crystallinity and physical dimensions (size and shape) of the perylene NPs resulting from the hydrothermal process are analyzed. These results are confirmed by nanoscale PL measurements for single NPs using laser confocal microscopy. The photovoltaic characteristics of organic solar cells (OSCs) are improved through the use of the perylene NPs. It is found that the performance of the OSCs is strongly correlated with the optical‐absorption properties of the perylene NPs.     

Multicolored Nanocolloidal Hydrogel Inks

Nanocolloidal gels are emerging as a promising class of materials with applications as inks in 2D and 3D printing. Polymer nanoparticles (NPs) offer many advantages as potential building blocks of nanocolloidal gels, due to the ability to control NP dimensions, charge, surface chemistry, and functionality; however, their applications as inks in printing are yet to be explored. Here, functional nanocolloidal hydrogels formed by percolating oppositely charged latex NPs with different dimensions and charge densities are reported. The shear-thinning and self-healing properties of the nanocolloidal gels and the mechanical properties of the resulting printed films are examined. NP functionality is achieved by covalently labeling them with different fluorescent dyes that emit at two distinct wavelengths. Using these NPs, a facile route for 3D printing of multicolored fluorescence patterns is shown, with each color being visualized under a specific, well-defined excitation wavelength.     

Spatial Extent of Fluorescence Quenching in Mixed Semiconductor–Metal Nanoparticle Gel Networks

In this work, mixing and co-gelation of Au nanoparticles (NPs) and highly luminescent CdSe/CdS core/shell nanorods (NRs) are used as tools to obtain noble metal particle-decorated macroscopic semiconductor gel networks. The hybrid nature of the macrostructures facilitates the control over the optical properties: while the holes are trapped in the CdSe cores, the connected CdSe/CdS NRs support the mobility of excited electrons throughout the porous, hyperbranched gel networks. Due to the presence of Au NPs in the mixed gels, electron trapping in the gold NPs leads to a suppressed radiative recombination, namely, quenches the fluorescence in certain fragments of the multicomponent gel. The extent of fluorescence quenching can be influenced by the quantity of the noble metal domains. The optical properties are monitored as a function of the NR:NP ratio of a model system CdSe/CdS:Au. By this correlation, it demonstrates that the spatial extent of quenching initiated by a single Au NP exceeds the dimensions of one NR, which the Au is connected to (with a length of 45.8 nm ± 4.1 nm) and can reach the number of nine NRs per Au NP, which roughly corresponds to 400 nm of total electron travel distance within the network structure.     

Assembly and Characterizations of Bifunctional Fluorescent and Magnetic Microneedles With One Decade Length Tunability

This report presents the fabrication of bifunctional magnetic and fluorescent microneedles (µNDs) made of a ternary mixture of magnetic nanoparticles (NPs), quantum dots (QDs), and polyelectrolyte. The assembly relies on the electrostatic complexation of negatively charged NPs with positively charged polymer strands and is controlled by the charge ratio between the nanoparticle building blocks and the polymer mortar. The resulting 1D objects can be actuated using an external magnetic field and can be imaged using fluorescence microscopy, thanks to the fluorescent and superparamagnetic properties inherited from their NP constituents. Using a combination of core and surface characterizations and a state‐of‐the‐art image analysis algorithm, the dependence of the brightness and length on the ternary composition is thoroughly investigated. In particular, statistics on hundreds of µNDs with a range of compositions show that the µNDs have a log‐lormal length distribution and that their mean length can be robustly tuned in the 5–50 µm range to match the relevant length scales of various applications in micromixing, bioassays or biomechanics.     

Generic Strategy of Preparing Fluorescent Conjugated‐Polymer‐Loaded Poly(DL‐lactide‐co‐Glycolide) Nanoparticles for Targeted Cell Imaging

A general strategy for the preparation of highly fluorescent poly(DL‐lactide‐co‐glycolide) (PLGA) nanoparticles (NPs) loaded with conjugated polymers (CPs) is reported. The process involves encapsulation of organic‐soluble CPs with PLGA using a modified solvent extraction/evaporation technique. The obtained NPs are stable in aqueous media with biocompatible and functionalizable surfaces. In addition, fluorescent properties of the CP‐loaded PLGA NPs (CPL NPs) could be fine‐tuned by loading different types of CPs into the PLGA matrix. Four types of CPL NPs are prepared with a volume‐average hydrodynamic diameter ranging from 243 to 272 nm. The application of CPL NPs for bio‐imaging is demonstrated through incubation with MCF‐7 breast cancer cells. Confocal laser scanning microscopy studies reveal that the CPL NPs are internalized in cytoplasm around the nuclei with intense fluorescence. After conjugation with folic acid, cellular uptake of the surface‐functionalized CPL NPs is greatly enhanced via receptor‐mediated endocytosis by MCF‐7 breast cancer cells, as compared to that for NIH/3T3 fibroblast cells, which indicates a selective targeting effect of the folate‐functionalized CPL NPs in cellular imaging. The merits of CPL NPs, such as low cytotoxicity, high fluorescence, good photostability, and feasible surface functionalization, will inspire extensive study of CPL NPs as a new generation of probes for specific biological imaging and detection.     

High-Resolution and Stable Ruddlesden–Popper Quasi-2D Perovskite Flexible Photodetectors Arrays for Potential Applications as Optical Image Sensor

The development of an efficient fabrication route to achieve high-resolution perovskite pixel array is key for large-scale flexible image sensor devices. Herein, a high-resolution and stable 10 × 10 flexible PDs array based on formamidinium(FA⁺) and phenylmethylammonium (PMA⁺) quasi-2D (PMA)₂FAPb₂I₇ (n = 2) perovskite is demonstrated by developing SiO₂-assisted hydrophobic and hydrophilic treatment process on polyethylene terephthalate substrate. By introducing Au nanoparticles (Au NPs),  the perovskite film quality is improved and grain boundaries are reduced. The mechanism by which Au NPs upgrade the photoelectric quality of perovskite is mainly revealed by glow discharge-optical emission spectroscopy (GD-OES) and grazing-incidence wide-angle X-ray scattering (GIWAXS). To further improve the photoelectric performance of the devices, a post-treatment strategy with formamidinium chloride (FACl) is used . The optimized flexible PDs arrays show excellent optoelectronic properties with a high responsivity of 4.7 A W⁻¹, a detectivity of 6.3 × 10¹² Jones, and a broad spectral sensitivity. The device also exhibits excellent electrical stability even under severe bending and excellent flexural strength, as well as excellent environmental stability. Finally, the integrated flexible PDs arrays are used as sensor pixels in an imaging system to obtain high-resolution imaging patterns, demonstrating the imaging capability of the PDs arrays.     

Near‐Field Enhanced Plasmonic‐Magnetic Bifunctional Nanotubes for Single Cell Bioanalysis

Near‐field enhanced bifunctional plasmonic‐magnetic (PM) nanostructures consisting of silica nanotubes with embedded solid nanomagnets and uniformly dual‐surface‐coated plasmonic Ag nanoparticles (NPs) are rationally synthesized. The solid embedded sections of nanotubes provide single‐molecule sensitivity with an enhancement factor up to 7.2 × 10⁹ for surface‐enhanced Raman scattering (SERS). More than 2× SERS enhancement is observed from the hollow section compared to the solid section of the same nanotube. The substantial SERS enhancement on the hollow section is attributed to the dual‐sided coating of Ag NPs as well as the near‐field optical coupling of Ag NPs across the nanotube walls. Experimentation and modeling are carried out to understand the dependence of SERS enhancement on the NP sizes, junctions, and the near field effects. By tuning the aspect ratio of the embedded nanomagnets, the magnetic anisotropy of nanotubes can be readily controlled to be parallel or vertical to the long directions for nano‐manipulation. Leveraging the bifunctionality, a nanotube is magnetically maneuvered to a single living mammalian cell amidst many and its membrane composition is analyzed via SERS spectroscopy.     

Use of Reversal Nanoimprinting of Nanoparticles to Prepare Flexible Waveguide Sensors Exhibiting Enhanced Scattering of the Surface Plasmon Resonance

A flexible surface plasmon resonance (SPR)‐based scattering waveguide sensor is prepared by directly imprinting hollow gold nanoparticles (NPs) and solid gold NPs onto flexible polycarbonate (PC) plates—without any surface modification—using a modified reversal nanoimprint lithography technology. Controlling the imprinting conditions, including temperature and pressure, allows for the fine adjustment of the depths of the embedded metal NPs and their SPR properties. This patterning approach exhibits a resolution down to the submicrometer level. A 3D finite‐difference time domain simulation is used to examine the optical behavior of light propagating parallel to the air/substrate interface within the near‐field regime. Consistent with the simulations, almost an order of magnitude enhancement in the scattering signal after transferring the metal NPs from the glass mold to the PC substrate is obtained experimentally. The enhanced signal is attributed to the particles' strong scattering of the guiding‐mode waves (within the waveguide) and the evanescent wave (above the waveguide) simultaneously. Finally, the imprinting conditions are optimized to obtain a strongly scattering bio/chemical waveguide sensor.     

Room‐Temperature Metallic Fusion‐Induced Layer‐by‐Layer Assembly for Highly Flexible Electrode Applications

To fabricate flexible electrodes, conventional silver (Ag) nanomaterials have been deposited onto flexible substrates, but the formed electrodes display limited electrical conductivity due to residual bulky organic ligands, and thus postsintering processes are required to improve the electrical conductivity. Herein, an entirely different approach is introduced to produce highly flexible electrodes with bulk metal–like electrical conductivity: the room‐temperature metallic fusion of multilayered silver nanoparticles (NPs). Synthesized tetraoctylammonium thiosulfate (TOAS)‐stabilized Ag NPs are deposited onto flexible substrates by layer‐by‐layer assembly involving a perfect ligand‐exchange reaction between bulky TOAS ligands and small tris(2‐aminoethyl)amine linkers. The introduced small linkers substantially reduce the separation distance between neighboring Ag NPs. This shortened interparticle distance, combined with the low cohesive energy of Ag NPs, strongly induces metallic fusion between the close‐packed Ag NPs at room temperature without additional treatments, resulting in a high electrical conductivity of ≈1.60 × 10⁵ S cm^?1 (bulk Ag: ≈6.30 × 10⁵ S cm^?1). Furthermore, depositing the TOAS–Ag NPs onto cellulose papers through this approach can convert the insulating substrates into highly flexible and conductive papers that can be used as 3D current collectors for energy‐storage devices.     

Silica‐Coated Manganese Oxide Nanoparticles as a Platform for Targeted Magnetic Resonance and Fluorescence Imaging of Cancer Cells

Monodisperse silica‐coated manganese oxide nanoparticles (NPs) with a diameter of ～35 nm are synthesized and are aminated through silanization. The amine‐functionalized core–shell NPs enable the covalent conjugation of a fluorescent dye, Rhodamine B isothiocyanate (RBITC), and folate (FA) onto their surface. The formed Mn₃O₄@SiO₂(RBITC)–FA core–shell nanocomposites are water‐dispersible, stable, and biocompatible when the Mn concentration is below 50 µg mL^?1 as confirmed by a cytotoxicity assay. Relaxivity measurements show that the core–shell NPs have a T₁ relaxivity (r₁) of 0.50 mM ^?1 s^?1 on the 0.5 T scanner and 0.47 mM ^?1 s^?1 on the 3.0 T scanner, suggesting the possibility of using the particles as a T₁ contrast agent. Combined flow cytometry, confocal microscopy, and magnetic resonance imaging studies show that the Mn₃O₄@SiO₂(RBITC)–FA nanocomposites can specifically target cancer cells overexpressing FA receptors (FARs). Findings from this study suggest that the silica‐coated Mn₃O₄ core–shell NPs could be used as a platform for bimodal imaging (both magnetic resonance and fluorescence) in various biological systems.     

Surface carrier wave amplification in InSb at X-band

Experiments have been conducted with slabs (1.5 × 2.5 × 0.3 mm³) of n-InSb to determine the propagation of surface waves in the presence of drifting carriers. Interdigital transducers of 10 fingers each with finger width of 7.5 µ (periodicity 30 µ) are used to excite slow surface waves with phase velocity on the order of the electron drift velocity of 2 × 10⁷cm/s. Integrated coplanar strip lines are used to carry to and from the transducers to X-band waveguides at each end. A nonsaturable unidirectional electronic gain of 11 dB/mm has been observed in the presence of counterstreaming electron-hole plasma created under pulsed high fields and a transverse magnetic field of 10 kG. The experimental results are explained on the basis of a surface plasma wave propagation model including the surface properties of the material through the surface recombination velocity. Rougher surfaces are shown to result in enhanced interaction but suffer from the susceptibility to oscillations. Reasonably well prepared but not exceptionally smooth surfaces are found to be better from the point of view of stable amplification.     

Self‐Assembly of Mechanoplasmonic Bacterial Cellulose–Metal Nanoparticle Composites

Nanocomposites of metal nanoparticles (NPs) and bacterial nanocellulose (BC) enable fabrication of soft and biocompatible materials for optical, catalytic, electronic, and biomedical applications. Current BC–NP nanocomposites are typically prepared by in situ synthesis of the NPs or electrostatic adsorption of surface functionalized NPs, which limits possibilities to control and tune NP size, shape, concentration, and surface chemistry and influences the properties and performance of the materials. Here a self‐assembly strategy is described for fabrication of complex and well‐defined BC–NP composites using colloidal gold and silver NPs of different sizes, shapes, and concentrations. The self‐assembly process results in nanocomposites with distinct biophysical and optical properties. In addition to antibacterial materials and materials with excellent senor performance, materials with unique mechanoplasmonic properties are developed. The homogenous incorporation of plasmonic gold NPs in the BC enables extensive modulation of the optical properties by mechanical stimuli. Compression gives rise to near‐field coupling between adsorbed NPs, resulting in tunable spectral variations and enhanced broadband absorption that amplify both nonlinear optical and thermoplasmonic effects and enables novel biosensing strategies.     

Conjugated Polymer Based Nanoparticles as Dual‐Modal Probes for Targeted In Vivo Fluorescence and Magnetic Resonance Imaging

A facile strategy is developed to synthesize dual‐modal fluorescent‐magnetic nanoparticles (NPs) with surface folic acid by co‐encapsulation of a far‐red/near‐infrared (FR/NIR)‐emissive conjugated polymer (PFVBT) and lipid‐coated iron oxides (IOs) into a mixture of poly(lactic‐co‐glycolic‐acid)‐poly(ethylene glycol)‐folate (PLGA‐PEG‐FOL) and PLGA. The obtained NPs exhibit superparamagnetic properties and high fluorescence, which indicates that the lipid coated on IOs is effective at separating the conjugated polymer from IOs to minimize fluorescence quenching. These NPs are spherical in shape with an average diameter of ≈180 nm in water, as determined by laser light scattering. In vitro studies reveal that these dual‐modal NPs can serve as an effective fluorescent probe to achieve targeted imaging of MCF‐7 breast cancer cells without obvious cytotoxicity. In vivo fluorescence and magnetic resonance imaging results suggest that the NPs are able to preferentially accumulate in tumor tissues to allow dual‐modal detection of tumors in a living body. This demonstrates the potential of conjugated polymer based dual‐modal nanoprobes for versatile in vitro and in vivo applications in future.     

金纳米微粒的光学性质及其在生物成像和光热疗法中的应用

作为生物探针,纳米微粒以其独特的光学性质,易控的表面化学能力,在基于生物成像和诊断的分子生物学和医学领域中引起越来越广泛的关注.贵金属,尤其是金纳米微粒,由于其表面等离子体共振(SPR)等强吸收和发光特性,在生物组织成像,癌症的诊断和治疗中存在着巨大的应用前景.结合配体的金纳米微粒能够特异性地标记癌症细胞上的受体,并提供特定分子的特有信息,进行生物成像和癌症检测.另外,金纳米微粒能够有效地吸收光能量进行局部加热,导致蛋白质变性,并致细胞死亡.主要回顾各种不同尺寸和形状的金纳米微粒的光学特性,以及选择性标记的金纳米微粒在生物成像,癌症诊断和光热疗法中的研究进展.     

Investigations on the Structural Damage in Human Erythrocytes Exposed to Silver,Gold, and Platinum Nanoparticles

Human erythrocytes or red blood cells (RBCs), which constitute 99% of blood cells, perform an important function of oxygen transport and can be exposed to nanoparticles (NPs) entering into the human body during therapeutical applications involving such NPs. Hence, the haemocompatibility of the Ag, Au, and Pt NPs on human RBCs is investigated. The parameters monitored include haemolysis, haemagglutination, erythrocyte sedimentation rate, membrane topography, and lipid peroxidation. The findings suggest that platinum and gold NPs are haemocompatible compared to Ag NPs. Erythrocytes exhibit significant lysis, haemagglutination, membrane damage, detrimental morphological variation, and cytoskeletal distortions following exposure to Ag NPs at a concentration of 100 µg mL^?1. Exposure of Ag⁺ to RBCs shows no lysis or deterioration, implying that the observed toxicity is solely due to NPs. The haemolyzed erythrocyte fraction has the ability to induce DNA damage in nucleated cells. Additionally, multiple pits and depressions are observed on RBC membrane following exposure to Ag NPs (50 µg mL^?1 onwards). Hence, it is apparent that Ag NPs exhibit toxicity on RBCs and on other cells that are exposed to NP‐mediated haemolyzed fractions.