Yongjae Jeong

Photoacoustic imaging is a noninvasive imaging modality with considerable potential for theranostic applications, providing high-resolution visualization of molecular and physiological responses to treatment. Among the diverse materials investigated for constructing theranostic nanoplatforms, hyaluronic acid has attracted substantial interest because of its biocompatibility, hydrophilicity, chemical modifiability, and affinity for CD44 receptors, which are frequently overexpressed in various cancer cells. Moreover, appropriately engineered hyaluronic acid-based formulations offer opportunities for localized and transdermal delivery, potentially reducing the need for systemic administration and expanding the applicability of noninvasive phototherapy, particularly for superficial lesions. In this review, we summarize recent advances in hyaluronic acid-based nanoplatforms for photoacoustic imaging-monitored phototherapy, categorized into photothermal therapy, photodynamic therapy, and their combination. We further discuss their material design, targeting and delivery mechanisms, photoacoustic monitoring capabilities, therapeutic performance, and key challenges for clinical translation.

Optical-resolution photoacoustic microscopy has become an important biomedical imaging modality for visualizing optical absorption contrast with micrometer-scale spatial resolution in superficial tissues. Because this modality relies on tightly focused laser illumination, precise optical alignment is essential, and free-space-to-fiber laser coupling is one of the most critical alignment steps. This issue becomes particularly important in transportable optical-resolution photoacoustic microscopy systems, where repetitive manual readjustment is required. Although our previous automated coupling approach based on motorized mirror control reduced the need for manual beam-path alignment, its optimization capability was limited when the focal position relative to the fiber core is not actively controlled. In this study, we propose an upgraded automated fiber-coupling module that integrates beam steering and fiber-side focusing alignment. In addition to the incident beam path control using motorized mirrors, a piezo-driven three-axis stage carries the coupling objective lens to align the focused beam with the fiber core. The coupled light was divided into imaging and monitoring paths, enabling real-time feedback-based optimization. The proposed module was validated by achieving high-quality photoacoustic images of both phantom and biological tissue through automated coupling. By extending automated coupling from mirror-based beam steering alone to combined beam steering and three-axis fiber-core alignment, the proposed coupling module provides a practical solution for improving the robustness, usability, and transportability of optical-resolution photoacoustic microscopy platforms and other fiber-coupled optical imaging systems.

Photoacoustic imaging is an advanced biomedical imaging technique that has been widely developed and applied in diverse biomedical studies. By generating optical-absorption-based signals with ultrasound resolution, it enables in vivo visualization of molecular functional information in biological tissues. Extensive research has been conducted to develop the multispectral light sources required for functional photoacoustic imaging. Among the various approaches, multispectral light sources generated using stimulated Raman scattering have shown considerable promise, particularly in photoacoustic microscopy, where achieving multispectral illumination remains challenging. This review summarizes photoacoustic imaging systems that employ stimulated Raman scattering for multispectral light sources and delves into their configurations and applications in the functional analyses of biological tissues. In addition, the review discusses the future directions of multispectral light sources by comparing different technologies based on key factors such as wavelength tunability, repetition rate, and power, which critically affect the accuracy and quality of multispectral photoacoustic imaging.