Cell-membrane-inspired polymers for constructing biointerfaces with efficient molecular recognition

UCST-Type Thermoresponsive Sol-Gel Transition Triblock Copolymer Containing Zwitterionic Polymer Blocks

Thermoresponsive sol-gel transition polymers are of significant interest because of their fascinating biomedical applications, including as drug reservoirs for drug delivery systems and scaffolds for tissue engineering. Although extensive research has been conducted on lower critical solution temperature (LCST)-type sol-gel transition polymers, there have been few reports on upper critical solution temperature (UCST)-type sol-gel transition polymers. In this study, we designed an ABA-type triblock copolymer composed of a poly(ethylene glycol) (PEG) block and zwitterionic polymer blocks that exhibit UCST-type thermoresponsive phase transitions. A sulfobetaine (SB) monomer with both ammonium and sulfonate (-SO3) groups in its side chain or a sulfabetaine (SaB) monomer with both ammonium and sulfate (-OSO3) groups in its side chain was polymerized from both ends of the PEG block via reversible addition-fragmentation chain-transfer (RAFT) polymerization to obtain PSB-PEG-PSB and PSaB-PEG-PSaB triblock copolymers, respectively. Although an aqueous solution containing the PSB-PEG-PSB triblock copolymer showed an increase in viscosity upon cooling, it did not undergo a sol-to-gel transition. In contrast, a sol-to-gel transition was observed when a phosphate-buffered saline containing PSaB-PEG-PSaB was cooled from 80 °C to 25 °C. The PSaB blocks with -OSO3 groups exhibited a stronger dipole-dipole interaction than conventional SB with -SO3 groups, leading to intermolecular association and the formation of a gel network composed of PSaB assemblies bridged with PEG. The fascinating UCST-type thermoresponsive sol-gel transition properties of the PSaB-PEG-PSaB triblock copolymer suggest that it can provide a useful platform for designing smart biomaterials, such as drug delivery reservoirs and cell culture scaffolds.

Biomaterial-Mediated Exogenous Facile Coating of Natural Killer Cells for Enhancing Anticancer Efficacy toward Hepatocellular Carcinoma

Natural killer (NK) cells exhibit a good therapeutic efficacy against various malignant cancer cells. However, the therapeutic efficacy of plain NK cells is relatively low due to inadequate selectivity for cancer cells. Therefore, to enhance the targeting selectivity and anticancer efficacy of NK cells, we have rationally designed a biomaterial-mediated ex vivo surface engineering technique for the membrane decoration of cancer recognition ligands onto NK cells. Our designed lipid conjugate biomaterial contains three major functional moieties: (1) 1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE) lipid for cell membrane anchoring, (2) polyethylene glycol for intracellular penetration blocker, and (3) lactobionic acid (LBA) for cancer recognition. The biomaterial was successfully applied to NK cell surfaces (LBA-NK) to enhance recognition and anticancer functionalities, especially toward asialoglycoprotein receptor (ASGPR)-overexpressing hepatocellular carcinoma. Highly efficient and homogeneous NK cell surface editing was achieved with a simple coating process while maintaining intrinsic properties of NK cells. LBA-NK cells showed potential ASGPR-mediated tumor cell binding (through LBA-ASGPR interaction) and thereby significantly augmented anticancer efficacies against HepG2 liver cancer cells. Thus, LBA-NK cells can be a novel engineering strategy for the treatment of liver cancers via facilitated immune synapse interactions in comparison with currently available cell therapies.

Biomimetic-Engineered Silicone Hydrogel Contact Lens Materials

Contact lenses are one of the most successful applications of biomaterials. The chemical structure of the polymers used in contact lenses plays an important role in determining the function of contact lenses. Different types of contact lenses have been developed based on the chemical structure of polymers. When designing contact lenses, materials scientists consider factors such as mechanical properties, processing properties, optical properties, histocompatibility, and antifouling properties, to ensure long-term wear with minimal discomfort. Advances in contact lens materials have addressed traditional issues such as oxygen permeability and biocompatibility, improving overall comfort, and duration of use. For example, silicone hydrogel contact lenses with high oxygen permeability were developed to extend the duration of use. In addition, controlling the surface properties of contact lenses in direct contact with the cornea tissue through surface polymer modification mimics the surface morphology of corneal tissue while maintaining the essential properties of the contact lens, a significant improvement for long-term use and reuse of contact lenses. This review presents the material science elements required for advanced contact lenses of the future and summarizes the chemical methods for achieving these goals.

[Solubilization of Poorly Water-soluble Drugs with Amphiphilic Phospholipid Polymers]

Most drug candidates developed in recent years are poorly water-soluble, which is a key challenge in pharmaceutical science. Various solubilization methods have been investigated thus far, most of which require solubilizers that provide a local hydrophobic environment wherein a drug can dissolve or induce interactions with drug molecules. We have focused on amphiphilic 2-methacryloyloxyethyl phosphoryl choline (MPC) polymers. In addition to the ease of molecular design of amphiphilic MPC polymers owing to their chemical structures, they have been reported to possess high biocompatibility in various biomaterial applications. Additionally, amphiphilic MPC polymers have been applied in the pharmaceutical field, especially in solubilization. We have qualitatively and quantitatively evaluated the effects of the chemical structure and physical properties of the solubilizer on the MPC polymers. In particular, MPC polymers with different chemical structures were designed and synthesized. The inner polarity and molecular mobility in the polymer aggregates were evaluated, indicating that the intrinsic properties reflect the chemical structure of the polymer. Additionally, amphiphilic MPC polymers were used to improve the solubility of poorly water-soluble drugs and as solid dispersion carriers, and they exhibited superior solubilizing abilities compared to a commonly used polymer. Furthermore, the solubility of biopharmaceuticals, such as peptides, was improved. It is possible to design and synthesize optimal structures based on the polarity of the hydrophobic environment and the intermolecular interaction with a drug. This research provides a unified interpretation of drugs and efficiently summarizes knowledge about drug development, which will facilitate the efficient and rapid development of drug formulations.

Molecular Machines and Microrobots: Nanoarchitectonics Developments and On-Water Performances

This review will focus on micromachines and microrobots, which are objects at the micro-level with similar machine functions, as well as nano-level objects such as molecular machines and nanomachines. The paper will initially review recent examples of molecular machines and microrobots that are not limited to interfaces, noting the diversity of their functions. Next, examples of molecular machines and micromachines/micro-robots functioning at the air-water interface will be discussed. The behaviors of molecular machines are influenced significantly by the specific characteristics of the air-water interface. By placing molecular machines at the air-water interface, the scientific horizon and depth of molecular machine research will increase dramatically. On the other hand, for microrobotics, more practical and advanced systems have been reported, such as the development of microrobots and microswimmers for environmental remediations and biomedical applications. The research currently being conducted on the surface of water may provide significant basic knowledge for future practical uses of molecular machines and microrobots.

Improvement of Oral Absorption of Poorly Water-Soluble Drugs by Solid Dispersions with Amphiphilic Phospholipid Polymer

Solid dispersions are one of methods for solubilizing water-insoluble drugs. To enhance the bioavailability, maintenance of the supersaturated state and absorption of the dissolved drug in the gastrointestinal tract are important. We designed and synthesized amphiphilic 2-methacryloyloxyethyl phosphorylcholine (MPC) copolymers as carriers for solid dispersions and evaluated the dissolution behavior in test solutions with different pH and additives. Solid dispersion of troglitazone with amphiphilic MPC copolymers having both aromatic rings and urethane bonds in the side chains showed rapid dissolution and excellent supersaturation maintenance. It was indicated that the balance between the interactions with drug molecules and the water affinity of the polymer should be considered when carriers for solid dispersions are designed. In addition, cell membrane permeability of the solid dispersion with the amphiphilic MPC copolymer was evaluated by the Dissolution / Permeation system, which consists of two liquid chambers and a monolayer of epithelial cells that mimics the intestinal dissolution and permeation process. Further, blood concentration of the drug when solid dispersions were orally administered in mice was also evaluated. The cell membrane permeability and oral absorbability were significantly improved, compared to the solid dispersions with poly(N-vinylpyrrolidone) and suspension or solution of crystalline troglitazone.

Biomimetic materials based on zwitterionic polymers toward human-friendly medical devices

This review summarizes recent research on the design of polymer material systems based on biomimetic concepts and reports on the medical devices that implement these systems. Biomolecules such as proteins, nucleic acids, and phospholipids, present in living organisms, play important roles in biological activities. These molecules are characterized by heterogenic nature with hydrophilicity and hydrophobicity, and a balance of positive and negative charges, which provide unique reaction fields, interfaces, and functionality. Incorporating these molecules into artificial systems is expected to advance material science considerably. This approach to material design is exceptionally practical for medical devices that are in contact with living organisms. Here, it is focused on zwitterionic polymers with intramolecularly balanced charges and introduce examples of their applications in medical devices. Their unique properties make these polymers potential surface modification materials to enhance the performance and safety of conventional medical devices. This review discusses these devices; moreover, new surface technologies have been summarized for developing human-friendly medical devices using zwitterionic polymers in the cardiovascular, cerebrovascular, orthopedic, and ophthalmology fields.