With the worldwide use of mRNA-lipid nanoparticle, one concern regarding the most commonly used material, polyethylene glycol （PEG）, in the field of drug delivery has made a small wave. Although this wave is not directly related to the main purpose of improving efficacy of therapeutics in DDS society, however, I think, it is necessary for DDS society to understand the current situation. This roundtable discussion will be an opportunity for industry and academia to discuss not only the perspective of DDS material, but also the perspectives of pharmaceutical filed and biomaterial filed and to declare what we should do in the future based on knowledge from the past to the present, and we hope to make a big wave from Japan.

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Polyvinylpyrrolidone（PVP） is used as an antithrombogenic polymer in artificial kidneys and other devices. We investigated the factors that affect the antithrombogenic properties of PVP and developed a new polymer that has higher antithrombogenic properties than PVP. It was found that in the case of the novel polymer, platelets are less likely to adhere when the mobility of the water around the polymer（adsorbed water） is close to that of the water around the proteins. The new polymer swells more in water than PVP, and quasielastic neutron scattering measurements indicate that the hydration constraints around the new polymer are more relaxed than PVP, resulting in larger space for movement. This polymer is applied and commercialized into medical materials such as various types of artificial kidneys, and the current status will also be introduced.

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Phosphorus is one of the six most important elements for all life. The aim of this review is to describe the utilized ability of two phosphorus-containing polymers inspired by the structures of phospholipids and nucleic acids, to design drug carriers. It is well known that phospholipid-inspired MPC polymers inhibit nonspecific protein adsorption. This phenomenon is effective in creating stealth-rich drug carriers. MPC polymers also act as suitable solubilizer for lipophilic drugs. On the other hand, polyphosphate esters（PPEs）, which are inspired from nucleic acids, are attracting attention as new degradable polymeric biomaterials. Bone-targeted and transdermal drug delivery by using PPEs are also presented.

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Zwitterionic polymers, characterized by the presence of both positively and negatively charged groups within the same monomer unit, exhibit unique hydration properties and biocompatibility. These properties enable to suppress nonspecific interactions with biomolecules such as proteins, polysaccharides, and nucleic acids. This review highlights recent advances in the understanding of zwitterionic polymer-biomolecule interactions, particularly focusing on hydration structures, protein adsorption, and surface functionalization. The discussion includes how structural factors affect hydration behavior and antifouling performance. Furthermore, the application of zwitterionic polymers in drug delivery systems（DDS） is also explored, including their use in protein conjugation, pH-responsive nanocarriers, and self-assembling micelles and vesicles. Recent studies have shown that the integration of computational and experimental approaches has provided design principles for constructing nanocarriers that are efficient, bioadaptive, and low in immunogenicity. The convergence of materials science, molecular interaction analysis, and computational modeling plays a key role in advancing the development of next-generation DDS based on zwitterionic polymers.

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Polysarcosine（PSar） is a promising polymeric material for drug delivery systems（DDS）, characterized by its non-ionic nature, high hydrophilicity, and low immunogenicity. This review introduces the chemical structure, biocompatibility, synthesis methods, and applications of PSar, with a particular focus on the authors’ studies using lactosomes and liposomes to evaluate immune responses. Through these studies, it was demonstrated that structural parameters—such as chain length, surface density, and linkage—significantly influence the immunogenicity of PSar-modified nanocarriers. These findings provide a rational basis for the molecular design of PSar-based DDS with controlled immune responses and enhanced stealth properties. PSar has thus been shown to offer not only functional versatility but also the structural tunability necessary for next-generation nanomedicine.

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Photoimmunotherapy（PIT） is a novel therapeutic strategy that combines targeted delivery of an antibody-photosensitizer conjugate with localized light illumination to selectively kill cancer cells. The first approved drug for this therapy is Akalux^Ⓡ（development code：RM-1929/ASP-1929）, which targets epidermal growth factor receptor and is used in combination with the BioBlade^Ⓡ laser system. This combination was approved in Japan in 2020—the first such approval in the world—for the treatment of unresectable locally advanced or recurrent head and neck cancer. The treatment, commonly referred to as Alluminox treatment for Head and Neck cancer, has since been adopted in clinical practice, primarily in departments of head and neck surgery and also in oral and maxillofacial surgery. Real-world data have shown favorable outcomes in terms of tumor control, safety, and quality of life preservation. In addition to expanding the application of ASP-1929 to other cancer types, efforts are ongoing to develop novel antibody-photosensitizer conjugates targeting the tumor immune microenvironment. These advances are expected to further broaden the clinical utility and impact of PIT in oncology.

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