Hee-Kyung Na

Exosomes play critical roles in cancer diagnosis and treatment as they carry molecular information that reflects the epigenetic state of their parent cells. For the first time, nanoscale epigenetic profiling of individual exosomes derived from colorectal cancer cell lines is demonstrated via photo‐induced force microscopy (PiFM). Exosomes from three cell lines with distinct CpG island methylator phenotype (CIMP) status are analyzed at the single‐vesicle level. The nano‐IR method provides simultaneous high‐resolution topographical and spectroscopic data, revealing detailed vibrational signatures that distinguish CIMP‐high (HCT116 and HT29) exosomes from CIMP‐negative (SW480) ones. Notably, exosomes from CIMP‐high cells exhibit red‐shifted amide I and nucleic acid region compared to those from CIMP‐negative cells, a shift attributed to increased 5‐methylcytosine (5mC) modifications, as verified by quantum chemical calculations. Furthermore, these measurements reveal heterogeneity among individual exosomes, suggesting the presence of distinct subpopulations with unique epigenetic profiles, demonstrating the importance of single‐vesicle resolution to detect molecular variations that remain obscured in ensemble studies. These findings present the potential of PiFM‐based single‐vesicle analysis to identify epigenetic markers in exosomes, laying the groundwork for its application in refined cancer diagnostics and targeted therapeutic strategies.

Micro ribonucleic acids (miRNAs) are small, noncoding RNA molecules that are pivotal regulators of gene expression and have emerged as critical biomarkers for various diseases and therapeutic targets. Among these, circulating miRNAs in the bloodstream are particularly attractive because of their stability and potential for noninvasive diagnostics. To address the demand for a highly sensitive and straightforward miRNA quantification method, we developed a novel biochip sensor that integrates a three-dimensional (3D) Au nanostructure with a dual-signal amplification strategy. A 3D Au nanostructure was fabricated on a polyvinylidene fluoride membrane using vacuum deposition, which provided a robust and flexible platform with enhanced optical properties. The nanostructure facilitated efficient probe immobilization and supported metal-enhanced fluorescence. Upon target miRNA recognition by the immobilized probes, two sequential signal amplification mechanisms are activated: (1) concatemer-based amplification by multiplex binding of fluorescent probes and (2) enzyme-free target recycling based on toehold-mediated strand displacement reactions. This dual amplification strategy on the 3D Au nanostructure achieved exceptional sensitivity and specificity for miRNA detection, even at lower concentrations. The biochip demonstrated a high-throughput capability, reusability, and practical applicability in molecular diagnostics. This innovative platform represents a significant advancement in miRNA sensing technology and offers a versatile tool for biomarker research and clinical diagnostics.

The second near-infrared (NIR-II) window (1000-1700 nm) offers advantages in biomedical applications such as deeper tissue penetration and superior imaging contrast. Despite this potential, existing NIR-II probes are limited by biocompatibility concerns, photobleaching, and poor photostability, issues that constrain their clinical utility. This study introduces Janus-type gold nanodiscs having an asymmetrically integrated hierarchical polyaniline (PANI) structure, optimized for use as multifunctional agents for NIR-II photothermal therapy and multimodal imaging. By shifting the localized surface plasmon resonance of the gold nanodiscs─the foundation of the Janus structure─from NIR-I to NIR-II, the developed AuPANI nanodiscs achieve remarkable deep-tissue photoacoustic imaging, up to 15 mm, while also enabling highly sensitive positron emission tomography imaging through stable radiolabeling. The nanodiscs also exhibit superior photostability and notable efficacy as photoacoustic-guided photothermal therapy agents under 1064 nm irradiation. This study positions AuPANI nanodiscs as a versatile platform for NIR-II theranostics, addressing limitations of current probes and advancing their potential for precise and effective cancer treatment.

This study investigates the applicability of six transition metal dichalcogenides to efficient therapeutic drug monitoring of ten antiepileptic drugs using laser desorption/ionization-mass spectrometry. We found that molybdenum ditelluride and tungsten ditelluride are suitable for the sensitive quantification of therapeutic drugs. The contribution of tellurium to the enhanced efficiency of laser desorption ionization was validated through theoretical calculations utilizing an integrated model that incorporates transition-metal dichalcogenides and antiepileptic drugs. The results of our theoretical calculations suggest that the relatively low surface electron density for the tellurium-containing transition metal dichalcogenides induces stronger Coulombic interactions, which results in enhanced laser desorption and ionization efficiency. To demonstrate applicability, up to 120 patient samples were analyzed to determine drug concentrations, and the results were compared with those of immunoassay and liquid chromatography-tandem mass spectrometry. Agreements among these methods were statistically evaluated using the Passing-Bablok regression and Bland-Altman analysis. Furthermore, our method has been shown to be applicable to the simultaneous detection and multiplexed quantification of antiepileptic drugs.

Digital holography requires precise phase analysis without wavefront aberration from defocusing errors. While the auto-contrast method is generally advantageous for refocusing, its accuracy suffers in low contrast conditions. Here, we suggest a simple phase analysis approach applying phase-detection autofocusing (PDAF) using a Fourier operation and the angular spectrum method to achieve fast and accurate refocusing even with high transmittance samples. The speed and sub-nano accuracy of the proposed method along with its quantitative autofocusing capability make it well suited for numerical digital holography reconstruction. Phase analysis with the PDAF technique has sensitivity to 0.1 nm changes in the focusing distance within the light source wavelength. In the reconstruction process, this method causes no wavefront distortion. The refocus calculation time using the focus calibration function obtained through the PDAF method is 0.012 s, enabling a real-time refocus correction of 83 fps in digital video holography. We performed refractive index measurements of Boro33 plates with high transmittance to interpret the physical meaning of the corrected focal distances and obtained a refractive index accuracy of 0.001. We then applied a real-time digital holographic measurement system and found that the PDAF technique removed dynamic phase fluctuation, an issue that cannot be solved by phase unwrapping.

ViSiON (visualization materials composed of silicon‐based optical nanodisks) is presented, which offers a unique optical combination of near‐infrared (NIR) optical properties and biodegradability. Initially, numerical simulations are conducted to calculate the total extinction and scattering effects of ViSiON by the diameter‐to‐thickness ratio, predicting precise control over its scattering properties in the NIR region. A top‐down patterning technique is employed to synthesize ViSiON with accurate diameter and thickness control. ViSiON with a 50 nm thickness exhibits scattering properties over 400 times higher than that of 30 nm, rendering it suitable as a contrast agent for optical coherence tomography (OCT), especially in ophthalmic applications. Furthermore, ViSiON possesses inherent biodegradability in media, with ≈95% degradation occurring after 48 h, and the degradation rate can be finely tuned based on the quantity of protein coating applied to the surface. Subsequently, the OCT imaging capability is validated even within vessels smaller than 300 µm, simulating retinal vasculature using a retinal phantom. Then, using an ex ovo chick embryo model, it is demonstrated that ViSiON enhances the strength of protein membranes by 6.17 times, thereby presenting the potential for ViSiON as an OCT imaging probe capable of diagnosing retinal diseases.

The need exists for biosensing technologies capable of sensitively and accurately detecting various biomarkers. In response, the development of nanozymes is actively underway; they have advantages in stability, cost, performance, and functionalization over natural enzymes commonly used for signal amplification in sensing technologies. However, the performance of nanozymes is interdependent with factors such as shape, size, and surface functional moiety, making it challenging to perform quantitative performance comparisons based on the nanozyme material. In this study, we propose a physical synthetic approach to fabricate double-layered bimetallic nanozymes with identical shapes, sizes, and surfaces but different material compositions. These Janus nanozymes consist of a nanozymatic layer responsible for catalytic activity and a gold layer responsible for quantification and efficient surface modification. Based on their identical physicochemical properties, the synthesized double-layered bimetallic nanozymes allow, for the first time, a quantitative comparison of nanozymatic activities in terms of various kinetic parameters. We compared several candidates and found that the Ir-Au nanozyme exhibited the best performance. Subsequently, we applied this nanozyme to detect neutralizing antibodies against SARS-CoV-2 based on a surrogate virus neutralization test. The results demonstrated a limit of detection as low as 2 pg/mL and selectivity specifically toward MERS-CoV. The performance of this assay was further validated using vaccinated samples, demonstrating the potential of our approach as a cost-effective, rapid, and sensitive diagnostic tool for neutralizing antibody detection against viruses such as SARS-CoV-2.