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MicroRNAs (miRNAs) are short non-coding RNAs that play an important role in regulating gene expression. Since miRNAs are abnormally expressed in various cancers, they are considered to be promising biomarkers for early cancer diagnosis. However, the short length and strong sequence similarity among miRNAs make their reliable quantification very challenging. We developed a highly selective amplification-free miRNA detection method based on Förster resonance energy transfer (FRET)-aided single-molecule counting. miRNAs were selectively labeled with FRET probes using splinted ligation. When imaged with a single-molecule FRET setup, the miRNA molecules were accurately identified by the probe's FRET. miRNA concentrations were estimated from the count of molecules. The high sensitivity of the method in finding sparse molecules enabled us to achieve a limit of detection of 31-56 amol for miR-125b, miR-100, and miR-99a. Single nucleotide mismatch could be discriminated with a very high target-to-mismatch ratio. The method accurately measured the high expression of miR-125b in gastric cancer cells, which agreed well with previous reports. The high sensitivity and accuracy of this technique demonstrated its clinical potential as a robust miRNA detection method.

Silicon particles have garnered attention as promising biomedical probes for hyperpolarized 29Si magnetic resonance imaging and spectroscopy. However, due to the limited levels of hyperpolarization for nanosized silicon particles, microscale silicon particles have primarily been the focus of dynamic nuclear polarization (DNP) applications, including in vivo magnetic resonance imaging (MRI). To address these current challenges, we developed a facile synthetic method for partially 29Si-enriched porous silicon nanoparticles (NPs) (160 nm) and examined their usability in hyperpolarized 29Si MRI agents with enhanced signals in spectroscopy and imaging. Hyperpolarization characteristics, such as the build-up constant, the depolarization time (T1), and the overall enhancement of the 29Si-enriched silicon NPs (10 and 15%), were thoroughly investigated and compared with those of a naturally abundant NP (4.7%). During optimal DNP conditions, the 15% enriched silicon NPs showed more than 16-fold higher enhancements─far beyond the enrichment ratio─than the naturally abundant sample, further improving the signal-to-noise ratio in in vivo29Si MRI. The 29Si-enriched porous silicon NPs used in this work are potentially capable to serve as drug-delivery vehicles in addition to hyperpolarized 29Si in vivo, further enabling their potential future applicability as a theragnostic platform.

MicroRNA (miR), a key molecule involved in endogenous RNA interference, is a promising therapeutic agent. In vivo delivery of miR, however, is a major factor limiting its application because its po...

A novel method (i.e., continuous magnetic cell separation in a microfluidic channel) is demonstrated to be capable of inducing multifractionation of mixed cell suspensions into multiple outlet fractions. Here, multicomponent cell separation is performed with three different distinguishable magnetic nanoclusters (MnFe2O4, Fe3O4, and CoFe2O4), which are tagged on A431 cells. Because of their mass magnetizations, which can be ideally altered by doping with magnetic atom compositions (Mn, Fe, and Co), the trajectories of cells with each magnetic nanocluster in a flow are shown to be distinct when dragged under the same external magnetic field; the rest of the magnetic characteristics of the nanoclusters are identically fixed. This proof of concept study, which utilizes the magnetization-controlled nanoclusters (NCs), suggests that precise and effective multifractionation is achievable with high-throughput and systematic accuracy for dynamic cell separation.

It has been of high significance to devise a biochemical analytical tool kit enabling the detection of few circulating tumor cells (CTCs) for early diagnosis of cancer. Despite recent effort made to detect few CTCs, it is still challenging to sense such cells with their low concentration and/or the minute amount of marker proteins expressed on few CTCs. In this work, we report the label-free recognition of carcinoembryonic antigens (CEAs) expressed on few CTCs by using a carbon nanotube (CNT) sensor coupled with scanning probe microscopy imaging for cancer diagnosis. It is shown that a CNT-patterned surface is able to specifically capture the CEA molecules in the whole cell lysate of CTCs with their concentration even up to 10(-3) cells/mL. Our work sheds light on our bioassay based on a CNT-patterned surface for highly sensitive, label-free detection of marker proteins expressed on few tumor cells, which may open a new avenue in early diagnosis of cancer by providing a novel biochemical analysis tool kit.

We report smart nanoprobe, hyaluronic acid (HA)-based nanocontainers containing miR-34a beacons (bHNCs), for the intracellular recognition of miR-34a levels in metastatic breast cancer cells, which is distinct from the imaging of biomarkers such of cell membrane receptors such as HER2. In this study, we demonstrate that a nanoscale vesicle that couples a targeting endocytic route, CD44, and a molecular imaging probe enables the efficient detection of specific miRNAs. Furthermore, bHNCs showed no cytotoxicity and high stability due to the anchored HA molecules on the surface of nanocontainers, and enables the targeted delivery of beacons via CD44 receptor-mediated endocytosis. In vitro and in vivo optical imaging using bHNCs also allow the measurement of miR-34a expression levels due to the selective recognition of the beacons released from the internalized bHNCs. We believe that the technique described herein can be further developed as a cancer diagnostic as well as a miRNA-based therapy of metastatic cancer.

We report the scanning probe microscope (SPM)-based single-molecule recognition of biomolecular interactions between protein kinase and small ligands (i.e., ATP and Imatinib). In general, it is difficult to sense and detect the small ligands bound to protein kinase (at single-molecule resolution) using a conventional atomic force microscope (AFM) due to the limited resolution of conventional AFM for detecting the miniscule changes in molecular size driven by ligand binding. In this study, we have demonstrated that Kelvin probe force microscopy (KPFM) is able to articulate the surface potential of biomolecules interacting with ligands (i.e., the protein kinase-ATP interactions and inhibition phenomena induced by antagonistic molecules) in a label-free manner. Furthermore, measured surface potentials for biomolecular interactions enable quantitative descriptions on the ability of protein kinase to interact with small ligands such as ATP or antagonistic molecules. Our study sheds light on KPFM that allows the precise recognition of single-molecule interactions, which opens a new avenue for the design and development of novel molecular therapeutics.

We fabricate the high-performance probes based on Au nanoparticles (AuNP) for detection of live cancer cell. AuNP were synthesized with narrow sized distribution (ca. 10 nm) by Au salt reduction method and deposited onto the aminated substrate as a cross-linker and hot spot. Herein, AuNP has enabled the easy and efficient immobilization of the antibody (Cetuximab), which can selectively interact with epidermal growth factor receptor (EGFR) on the surface of epidermal cancer, as detecting moiety onto the AuNP-deposited substrate without nanolithography process. After conjugation of Cetuximab with AuNP-deposited substrate, Cetuximab-conjugated probe as a live cancer cell detector (LCCD) could detect EGFR-highexpressed A431 cells related to epithelial cancer with 54-times larger specificity and sensitivity in comparison with EGFR-deficient MCF7 cells. This implies that AuNP-based probes demonstrate abundant potentials for detection and separation of small biomolecules, cells and other chemicals.

Diagnosis of cancer in the early stages requires sensitive magnetic resonance (MR) probes to detect low concentrations of magnetic substances. In this study, ultrasensitive magnetic resonance contrast agents (UMRCAs) composed of magnetic nanocrystals and amphiphilic block copolymers were synthesized for cancer detection using polyethylene glycol and fatty acid. The chemical structures and the compositions of PEGylated magnetic nanoparticles were analyzed. UMRCAs displayed remarkable colloidal stability and high sensitivity as MR probes. Furthermore, UMRCAs exhibited low cytotoxicity and excellent cancer detection ability in an in vivo animal model.

The unique properties of magnetic nanocrystals provide them with high potential as key probes and vectors in the next generation of biomedical applications. Although superparamagnetic iron oxide nanocrystals have been extensively studied as excellent magnetic resonance imaging (MRI) probes for various cell trafficking, gene expression, and cancer diagnosis, further development of in vivo MRI applications has been very limited. Here, we describe in vivo diagnosis of cancer, utilizing a well-defined magnetic nanocrystal probe system with multiple capabilities, such as small size, strong magnetism, high biocompatibility, and the possession of active functionality for desired receptors. Our magnetic nanocrystals are conjugated to a cancer-targeting antibody, Herceptin, and subsequent utilization of these conjugates as MRI probes has been successfully demonstrated for the monitoring of in vivo selective targeting events of human cancer cells implanted in live mice. Further conjugation of these nanocrystal probes with fluorescent dye-labeled antibodies enables both in vitro and ex vivo optical detection of cancer as well as in vivo MRI, which are potentially applicable for an advanced multimodal detection system. Our study finds that high performance in vivo MR diagnosis of cancer is achievable by utilizing improved and multifunctional material properties of iron oxide nanocrystal probes.

In nanomaterials synthesis, Ostwald ripening is a postsynthetic problem that is one obstacle for common utilization of nanomaterials. Herein, we report an unprecedented Ostwald ripening mechanism resulting from the simple combination of hydrogen peroxide (H2O2) and cetyltrimethylammonium bromide (CTAB)-stabilized gold nanoparticles (AuNPs) at room temperature. In this ripening process, H2O2 redox induces simultaneous dissolution and growth of AuNPs where bromide (Br–) from CTAB helps to form AuBr2– in aqueous solution at room temperature. This understanding will provide basic strategies for advanced designs and development of various nanomaterials.

Since the use of magnetic nanocrystals as probes for biomedical system is attractive, it is important to develop optimal synthetic protocols for high-quality magnetic nanocrystals and to have the systematic understanding of their nanoscale properties. Here we present the development of a synthetically controlled magnetic nanocrystal model system that correlates the nanoscale tunabilities in terms of size, magnetism, and induced nuclear spin relaxation processes. This system further led to the development of high-performance nanocrystal-antibody probe systems for the diagnosis of breast cancer cells via magnetic resonance imaging.