Aggregate Science - Part 1

For centuries, molecular science has been guided by reductionism, with researchers focusing primarily on the properties of matter at the level of individual molecules. Yet, recent advances in aggregation-induced emission (AIE) research have introduced a transformative paradigm: aggregate science. This emerging field shifts the focus toward collective behaviors and emergent properties arising from interacting molecular systems, offering a more holistic framework for scientific exploration. By moving beyond reductionist constraints, aggregate science unlocks new frontiers of discovery. This seminar series will highlight its far-reaching implications across disciplines — from nanomaterials and optoelectronics to biomedical theranostics and beyond. Through a multidimensional lens, we seek to propel this integrative approach, fostering a paradigm shift in scientific research and revealing deeper insights into complex systems. Opening Remarks Molecular Precision in Dynamic Self-Assembly: How Discrete PEG Lipids Shape Lipid Nanoparticle Identity Dynamic self-assembly provides a powerful means of organizing molecular components into functional structures with properties that cannot be predicted from the individual building blocks alone. While considerable attention has been devoted to molecular composition and intermolecular interactions, the influence of molecular dispersity on dynamic assembly remains poorly understood. Poly(ethylene glycol) (PEG) lipids provide a particularly relevant example. Conventional PEG lipids comprise distributions of chain lengths, yet they are commonly treated as single molecular components defined only by their average molecular weight. In this talk, I will discuss how replacing conventional polydisperse PEG lipids with molecularly defined analogues reshapes the assembly and biological identity of lipid nanoparticles. PEG dispersity propagates across multiple length scales, influencing lipid incorporation, mRNA loading, particle-to-particle variability, internal organization and PEG-layer structure. These assembly-level differences subsequently alter protein-corona formation, intracellular trafficking and interactions with the immune system. Molecularly defined PEG lipids reduce structural heterogeneity and provide a more controlled nano–bio interface, with important implications for repeated mRNA delivery. Together, these findings extend the concept of dynamic self-assembly from the regulation of chemical reactivity to the construction of functional nanomedicines. They demonstrate that molecular precision is not merely a matter of chemical purity, but a fundamental design parameter governing how multicomponent assemblies form, evolve and function in biological environments. Light Meets Nature: Cellulose Cluster as a Natural Photoantimicrobial Agent Antibiotic resistance continues to outpace our therapeutic options, driving the search for antimicrobial strategies that bacteria cannot easily evade. Antimicrobial photodynamic therapy (aPDT) is one such strategy: it uses reactive oxygen species to attack bacterial membranes, proteins, and nucleic acids simultaneously, leaving little room for resistance to develop. Its promise, however, has been limited by photosensitizers that aggregate and lose efficiency (aggregation-caused quenching) and often show poor biocompatibility. In this talk, I will show how cluster-triggered emission (CTE) turns an unexpected material into a photosensitizer: cellulose derivatives. We demonstrate that these FDA-approved materials exhibit pronounced CTE, generating singlet oxygen in suspension through long-lived excitonic states, and that they display strong photoantimicrobial activity against Gram-positive bacteria such as Staphylococcus aureus. These results redefine cellulose: from a passive formulation excipient into an active photodynamic material with previously unrecognized capabilities. Research Overview on Through-Space Conjugation Traditional organic luminescent materials typically rely on through-bond conjugation (TBC) within rigid structures to promote π-electron delocalization, thereby achieving high fluorescence quantum yields and tunable emission wavelengths. However, in recent years, anomalous visible-light emission has been observed in non-TBC systems lacking π-electrons, such as polyethylene glycol and polyethylenimine, overturning the conventional understanding of organic luminescence mechanisms. To address this scientific challenge, our team has designed and synthesized a new class of multiarylalkane systems, systematically exploring a novel luminescence mechanism driven by through-space conjugation (TSC). In this talk, the underlying mechanism and structure–property relationships of TSC will be elaborated, followed by demonstrations of how this principle enables the construction of new organic luminophores, including the development of the smallest known near-infrared organic emitter to date.