Various materials are developed and applied for drug delivery systems (DDS). Of these, photocatalytic materials are considered one of the attractive materials for DDS. Because titanium dioxide used as a photocatalyst is safe for living organisms and can be prepared the various modifications. Therefore, it is possible to apply some drugs or antibodies for the surface of photocatalytic materials. These materials can be delivered and be concentrated to targeting organs and cells by the combination with magnetic nano particles. Further, it is possible not only to control the drug releasing by photocatalytic reaction but also to kill target cells directly by photocatalytic reaction. In addition to the possibility of photocatalysts as DDS materials, photocatalyst is also the attractive materials as antibacterial/antiviral materials. The infection of SARS-CoV-2 is the serious problem in the world. Then, we introduce the antibacterial/antiviral test method using photocatalytic materials and its application including in water purification, because we expect to apply for antibacterial/antiviral. Thus, this paper introduces the potential of photocatalytic materials as follows; the potential of photocatalytic materials as DDS and cancer treatments, test methods for antibacterial/antiviral effects by photocatalytic reactions, the potential of photocatalytic materials as medical applications, the inactivation of SARS-CoV-2 by photocatalytic reaction, and water purification.

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Tissue engineering is the driving force behind advances in regenerative medicine. It is diversifying and different approaches are being developed. Our research group has established a technology that allows cells to be collected in sheets simply by lowering the temperature using a “temperature-responsive culture dish.” We have proposed a unique method “cell sheet-based tissue engineering” in which a single-layer cell sheet or laminated cell sheets is transplanted in the body. Regenerative therapies by cell sheet transplantation have already been clinically applied in seven areas. In addition, we have realized the construction of a functional three-dimensional tissue, especially beating cardiac tissue, by stacking cell sheets. We are also challenging the scale-up by introducing the vascular network. Furthermore, cell sheet engineering has been applied to the construction of tissue models necessary for drug discovery and disease research, and the production of cultured meat, which has become a hot topic in recent years. In this review, development and future of cell sheet-based tissue engineering are introduced and discussed.

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Antibody-drug conjugates (ADCs) are expected as next therapeutic antibodies, and the number of administrated ADCs has been increased. Antibodies are conjugated by potent toxic low-molecular weight compounds via linkers. The conjugated toxins are delivered to targeted region and released. ADCs expands safety-margin of low molecular compounds. For developing efficient ADCs, contribution from both synthetic organic chemistry and analytical chemistry are essential. By traditional protein conjugation methodology, numerous numbers of ADCs are generated. Now, second-generation ADCs with wider safety-margin is highly required. For the purpose, methodology of homogeneous ADC preparation is highly required. In order to develop efficient ADCs, variation of linker has been increased. In addition, the synthesized ADCs must be characterized for quality evaluation. Especially, high resolution MS and Ultra-Performance Liquid Chromatography (UPLC) analyses are useful for ADC characterization.

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There is an increasing trend in the number of approved oligonucleotide therapeutics in the world. Recently approved therapeutics include: gapmer-type antisense oligonucleotides, splice-switching antisense oligonucleotides, siRNA encapsulated in nanoparticles or conjugated with triantennary N-acetylgalactosamine (GalNAc), and CpG oligonucleotide. Except for the nanoparticle-formulated siRNA, all these therapeutics share the structural characteristics common to hydrophilic macromolecules, but differ in many aspects, including the location of the target molecule/target cells, administration route, and tissue distribution. Because only the fraction of the administered dose reaching the target exhibits therapeutic effects, the tissue distribution of oligonucleotide therapeutics is one of the most critical parameters that determines the success in the development. Protein binding is a most important characteristic for those administered subcutaneously or intravenously, but the binding characteristic has hardly been actively optimized. Protein binding is important not only for the tissue distribution but for the induction of adverse reactions. Ligand conjugation can increase the distribution of oligonucleotide therapeutics to target cells. GalNAc has been used as a ligand to deliver siRNA to hepatocytes that express GalNAc-recognizing asialoglycoprotein receptors. The cells that can be targeted with oligonucleotide therapeutics so far, however, are limited to hepatocytes and dystrophic muscle cells. In this article, the current status and perspectives of the delivery of oligonucleotide therapeutics are discussed, focusing on the possible role of drug delivery systems in widening their therapeutic application.

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In this article, our activatable (non-DDS) rapid fluorescent probes are showcased, which were developed by utilizing our original precise design strategies for fluorescent probes, and whose fluorescence characteristics are greatly altered only in the cancer site. Some of the developed probes have been found to be sufficiently effective in treating spontaneous cancers of actual patients beyond the level of animal experiments, and clinical development of several probes for use in actual clinical practice has been started, including the first in human study. It is highly anticipated that the day will soon come when surgeons will be able to clearly identify the site of cancer to be treated and will be able to perform precise fluorescence endoscopic or open surgery. This article also briefly summarizes the author's thoughts on the future of cancer care technology using a combination of non-DDS probe and DDS technologies.

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