Abstract A gold nanoparticle‐based colorimetric antibody structure and activity evaluation method is developed without using complicated and expensive instrumentation. In this assay, a minimum number of antibodies to stabilize nanoparticles are conjugated to gold nanoparticles to prepare minimally stable nanoparticle probes, and the addition of salt rapidly induced particle aggregation and a color change of the solution from red to blue (25‐min assay time). It is found that the solution color change is affected by the degree of structural denaturation of antibodies, and the conformational change of antibodies affects the modification of antibodies to nanoparticles and particle stability. Importantly, the colorimetric method can be applied to different types of antibodies (IgG, IgA, and IgM) and it shows comparable or better structural sensitivity than conventional circular dichroism spectroscopy. Moreover, immunoassay results show that these structural changes of antibodies are highly correlated with their antigen‐binding activities. Rapid particle aggregation and high structural sensitivity are achieved in this assay because particles are modified with a minimum number of antibodies to stabilize particles in solution. This nanoparticle‐based colorimetric method could be useful in evaluating the structural and activity changes of an array of antibodies in an easy, rapid, and sensitive manner.
Here, we highlight the strategies for the synthesis and tuning of a variety of metal nanostructures and nanoassemblies with oligonucleotides and their applications. We have discussed the importance of and need for various metal nanostructures and the role and suitability of DNA in building these nanostructures and nanoassemblies. A large part of this article is devoted to the discussion of DNA-mediated synthetic methods for metal nanostructures. The synthetic strategies are categorized into two groups – strategy 1 that uses DNA as the ligand for metal nanoparticles and subsequent assembly or modification and strategy 2 that uses DNA template-directed assemblies of metal nanoparticles.
Herein, plasmonic metal tripod nanoframes with three-fold symmetry were synthesized in a high yield (∼83%), and their electric field distribution and single-particle surface-enhanced Raman scattering (SERS) were studied. We realized such complex frame morphology by synthesizing analogous tripod nanoframes through multiple transformations. The precise control of the Au growth pattern led to uniform tripod nanoframes embedded with circle or line-shaped hot spots. The linear-shaped nanogaps ("Y"-shaped hot-zone) of the frame structures can strongly and efficiently confine the electric field, allowing for strong SERS signals. Coupled with a high synthetic yield of the targeted frame structure, strong and uniform SERS signals were obtained inside the nanoframe gaps. Remarkably, quite reproducible SERS signals were obtained with these structures-the SERS enhancement factors with an average value of 7.9 × 107 with a distribution of enhancement factors from 2.2 × 107 to 2.2 × 108 for 45 measured individual particles.
A highly sensitive multiplexed DNA detection assay uses restriction-enzyme-encoded, DNA-modified magnetic microparticle and gold nanoparticle probes combined with dark-field nanoparticle imaging analysis (see picture). A sensitivity of 100 fM and high specificity of the detection targets are achieved.
Abstract Viruses are small agents that can infect living creatures and cause harmful diseases. Rapid, sensitive virus detection would be beneficial for public health, and recent studies have shown that nanoparticles may have applications in virus detection. In particular, the unique properties of metal nanoparticles, originating from localized surface plasmons, allow for detection of virus through various methods. Additionally, the high surface‐to‐volume ratio and ease of surface modification of these nanoparticles provide advantages for bio‐applications. In this Focus Review, we describe currently available and recent advances in virus detection methods with metal nanoparticles. First, we outline several features of traditional virus detection methods and provide a brief explanation of metal nanoparticles. Then, we discuss solution‐based or substrate‐based virus detection according to the main operating phase of the detection elements. Finally, we evaluate the use of clinical samples for virus detection with metal nanoparticles.
A transparent, nanoporous, and transferable (TNT) membrane-based cell co-culture platform is developed by K. Char, J.-M. Nam, and co-workers on page 1893 for systematic investigation and control of paracrine signaling between cancerous and stromal cells. With the high degree of freedom in tuning nanopores, analyzing cells of interest, and manipulating the TNT membranes, the paracrine signaling between metastatic cancer cells and three different types of stromal cells is studied and controlled.
The electrical manipulation of a patterned lipid membrane is employed for the highly reliable, straightforward, and sensitive detection of membrane receptor–ligand interactions in an array platform. Target-binding modulates lipid fluidity and membrane phase, and the difference in membrane fluidity with different target concentrations is clearly distinguished in an amplifiable manner. This is achieved by locally concentrating charged, fluorescent lipids during electrophoresis. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.
The plasmonic properties of metal nanostructures have been heavily utilized for surface-enhanced Raman scattering (SERS) and metal-enhanced fluorescence (MEF), but the direct photoluminescence (PL) from plasmonic metal nanostructures, especially with plasmonic coupling, has not been widely used as much as SERS and MEF due to the lack of understanding of the PL mechanism, relatively weak signals, and the poor availability of the synthetic methods for the nanostructures with strong PL signals. The direct PL from metal nanostructures is beneficial if these issues can be addressed because it does not exhibit photoblinking or photobleaching, does not require dye-labeling, and can be employed as a highly reliable optical signal that directly depends on nanostructure morphology. Herein, we designed and synthesized plasmonic cube-in-cube (CiC) nanoparticles (NPs) with a controllable interior nanogap in a high yield from Au nanocubes (AuNCs). In synthesizing the CiC NPs, we developed a galvanic void formation (GVF) process, composed of replacement/reduction and void formation steps. We unraveled the super-radiant character of the plasmonic coupling-induced plasmon mode which can result in highly enhanced PL intensity and long-lasting PL, and the PL mechanisms of these structures were analyzed and matched with the plasmon hybridization model. Importantly, the PL intensity and quantum yield (QY) of CiC NPs are 31 times and 16 times higher than those of AuNCs, respectively, which have shown the highest PL intensity and QY reported for metallic nanostructures. Finally, we confirmed the long-term photostability of the PL signal, and the signal remained stable for at least 1 h under continuous illumination.
Recent advances of plasmonic nanoparticles include fascinating developments in the fields of energy, catalyst chemistry, optics, biotechnology, and medicine. The plasmonic photothermal properties of metallic nanoparticles are of enormous interest in biomedical fields because of their strong and tunable optical response and the capability to manipulate the photothermal effect by an external light source. To date, most biomedical applications using photothermal nanoparticles have focused on photothermal therapy; however, to fully realize the potential of these particles for clinical and other applications, the fundamental properties of photothermal nanoparticles need to be better understood and controlled, and the photothermal effect-based diagnosis, treatment, and theranostics should be thoroughly explored. This Progress Report summarizes recent advances in the understanding and applications of plasmonic photothermal nanoparticles, particularly for sensing, imaging, therapy, and drug delivery, and discusses the future directions of these fields.
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