Afterglow Luminescent Particles for Photomedicinal Applications

Abstract

Recently, afterglow luminescent particles (ALPs) have attracted great attention for exploring their optical characteristics in afterglow luminescence, mechanoluminescence (ML), and mechanical quenching (MQ) due to their potential applications. These unique phenomena play a crucial role in delivering visible light tailored for specific applications in photonics, biophotonics, and biomedicine. However, these optical phenomena need to be more clearly explained for their specific application in photonics. Additionally, challenges such as photo-stability, dispersibility, and biocompatibility hinder their photomedicinal applications. To mitigate these limitations, extensive efforts have been made to elucidate these optical phenomena and develop methods to enhance the performance of ALPs with excellent biocompatibility. This thesis describes the synthesis, characterization, and photomedicinal applications of various ALPs while analyzing these distinctive optical phenomena. In part I, we present a comprehensive review of afterglow luminescent particles (ALPs) from the underlying physical principles to their photomedicinal applications. We first discuss the background and some technical challenges of current limitations of ALPs. Subsequently, we discuss the optical phenomenon of ALPs, trap states and their contribution to the optical process, as well as some strategies to optimize afterglow luminescent emission. Next, we review a few promising directions in which ALPs can make a lasting transformative impact on photomedicinal applications from the perspectives in photochemical tissue bonding and photodynamic wound healing. In part II, we design ALPs for the development of a wearable and rewritable photonic display system as a communication toolbox under dark conditions or underwater environments with limited communication. This display system demonstrates long-lasting MQ after short ML along the handwritten trajectories with mechanical pressure and the written content can be easily erased by short ultraviolet (UV) light irradiation, preserving the system integrity with the high reproducibility of ML and MQ responses. We assess the effect of trapped electrons and recharging process on the ML and MQ, which provides insights into their underlying mechanisms. In addition, this display system exhibits remarkable resistance to humidity, and retains its rewritable and photonic capabilities underwater for a long-term period. Furthermore, we demonstrate the rewritable property of display system on a human skin, confirming their effectiveness as a wearable photonic display system. Taken together, this research would pave a new big avenue to develop biophotonic materials for various photomedicinal applications with mechano-optical conversions. In part III, we develop controlled afterglow luminescent particles (ALPs) of ZnS:Ag,Co with strong and persistent green luminescence for photochemical tissue bonding (PTB). The co-doping of Ag+ and Co2+ ions into ZnS:Ag,Co particles with the proper vacancy formation of host ions results in high luminescence intensity and long-term afterglow. In addition, the ALPs of ZnS:Ag,Co could be recharged rapidly under short ultraviolet (UV) irradiation, which effectively activates rose bengal (RB) in hyaluronate-RB (HA-RB) conjugates for the crosslinking of dissected collagen layers without additional light irradiation. The remarkable PTB of ZnS:Ag,Co particles with HA-RB conjugates is confirmed by in vitro collagen fibrillogenesis assay, in vivo animal wound closure rate analysis, and in vivo tensile strength evaluation of incised skin tissues. Taken together, we could confirm the feasibility of controlled ALPs for various biophotonic applications. In part IV, we present the versatile attributes of afterglow luminescent particles (ALPs) embedded in dopamine-modified hyaluronate (HA-DOPA) patches for accelerated wound healing. ALPs enhance the viscoelastic properties of the patches, and the photoluminescence (PL) and afterglow luminescence (AL) of ALPs maximize singlet oxygen generation and collagen fibrillogenesis for effective healing in the infected wounds. The patches are optimized to achieve the strong and rapid adhesion in the wound sites. In addition, the swelling and shrinking properties of adhesive patches contribute to a non-linear behavior in the wound recovery, playing an important role as a strain-programmed patch. The protective patch prevents secondary infection and skin adhesion, and the patch seamlessly detaches during wound healing, enabling efficient residue clearance. In vitro, in vivo, and ex vivo model tests confirm the biocompatibility, antibacterial effect, hemostatic capability, and collagen restructuring for the accelerated wound healing. Taken together, this research collectively demonstrates the feasibility of HA-DOPA/ALP patches as a versatile and promoting solution for advanced accelerated wound healing, particularly in scenarios involving bleeding and bacterial infections. In summary, during my Ph.D. thesis, various ALPs have been successfully synthesized and characterized for photonic and biomedical applications to display system, photochemical tissue bonding and photodynamic wound healing. These efforts would greatly contribute to open a new big avenue for the development of biophotonic materials for various photomedicinal applications.