Shinji Sakai

Osaka University | Handai · Department of Materials Engineering Science

This paper describes the hydrogels which are quickly degradable, even on-demand, by exposure to serum, as well as in situ gellable under mild conditions for cells. In addition, potential applications of these hydrogels to tissue engineering and regenerative medicine are also described. The hydrogels were produced from aqueous solution of amylopecti...

A phenolic hydroxyl group was incorporated into gelatin, using aqueous-phase carbodiimide activation chemistry, to obtain in situ gellable and injectable protein-based materials for drug delivery and tissue engineering applications. By this means, gelatin derivatives that were gellable via a peroxidase-catalyzed reaction were obtained. The enzymati...

Hydrogel sheaths were fabricated on the surfaces of individual mammalian cells through the cross-linking of polymer molecules catalyzed by horseradish peroxidase (HRP) in aqueous solution. For confining the progress of the cross-linking only on the cell surface, HRP was anchored to the cell membrane by soaking the cells in the solution containing t...

Extrusion-based 3D bioprinting has revolutionised tissue engineering, enabling complex biostructure manufacturing. However, extrusion imposes substantial shear stress on cells, compromising cell viability. Predicting and optimising cell viability remains challenging due to rheological modelling complexity and cell-type dependency. To address these...

An on-chip bubble-induced acoustic micromixer was developed for 3D bioprinting, achieving efficient mixing and excellent cell compatibility during the printing process.

Three-dimensional (3D) bioprinting has emerged as a promising technology in the field of tissue engineering. Notably, the advancement of multi-ink printing technology is crucial for further progress in 3D bioprinting. In this study, we developed a single-nozzle system with multiple inlets for multi-ink bioprinting that achieves high switching effic...

Access to clean water, hygiene, and sanitation is becoming an increasingly pressing global demand, particularly owing to rapid population growth and urbanization. Phytoremediation utilizes a highly conserved phytochelatin in plants, which captures hazardous heavy metal ions from aquatic environments and sequesters them in vacuoles. Herein, we repor...

The development of hydrogels that allow vascular endothelial cells to form capillary-like networks is critical for advancing tissue engineering and drug discovery. In this study, we developed hydrogels composed of phenolated hyaluronic acid (HA-Ph) with an average molecular weight of 490–159 kDa via sonication in an aqueous solution. These hydrogel...

In vitro network formation by endothelial cells serves as a fundamental model for studies aimed at understanding angiogenesis. The morphogenesis of these cells to form a network is intricately regulated by the mechanical and biochemical properties of the extracellular matrix. Here the effects of modulating these properties in hydrogels derived from...

Chitosan is a deacetylated polymer of chitin that is extracted mainly from the exoskeleton of crustaceans and is the second-most abundant polymer in nature. Chitosan hydrogels are preferred for a variety of applications in bio-related fields due to their functional properties, such as antimicrobial activity and wound healing effects; however, the e...

In this study, we introduce electrospun polydioxanone (PDO) nonwoven fabrics as a platform for the delivery of adeno-associated virus (AAV) vectors for transduction and genome editing by adhering them to organ surfaces, including the heart. AAV vectors were loaded onto the PDO fabrics by soaking the fabrics in a solution containing AAV vectors. In...

Adeno‐associated viral (AAV) vectors play a significant role in gene therapy, yet the typical delivery methods, like systemic and local AAV injections, often lead to unintended off‐target distribution and tissue damage due to injection. In this study, we propose a localized delivery approach for AAV vectors utilizing electrospun gelatin nanofiber m...

Access to clean water, hygiene, and sanitation is becoming an increasingly pressing global demand, particularly owing to rapid population growth and urbanization. “Phytoremediation” utilizes a highly conserved phytochelatin in plants, which captures hazardous heavy metal ions from aquatic environments and sequesters them in vacuoles. Herein, we rep...

Cell sheets have immense potential for medical and pharmaceutical applications including tissue regeneration, drug testing, and disease modelling. In this study, composite hydrogels were prepared from a mixture of phenolated hyaluronic acid (HA-Ph) and gelatin (Gelatin-Ph), with a controlled degree of polymer crosslinking and degradation, to fabric...

In the past decades, the microencapsulation of mammalian cells into microparticles has been extensively studied for various in vitro and in vivo applications. The aim of this study was to demonstrate the viability of bacterial polyglucuronic acid (PGU), an exopolysaccharide derived from bacteria and composed of glucuronic acid units, as an effectiv...

Herein, we report the hydrogelation of sugar beet pectin (SBP) via visible light-mediated photocrosslinking and its applications in extrusion-based 3D bioprinting. Rapid hydrogelation (<15 s) was achieved by applying 405 nm visible light to an SBP solution in the presence of tris(bipyridine)ruthenium(II) chloride hexahydrate ([Ru(bpy)3]2+) and sodi...

The absolute shortage of compatible liver donors and the growing number of potential recipients have led scientists to explore alternative approaches to providing tissue/ organ substitutes from bioengineered sources. Bioartificial regeneration of a fully functional tissue/organ replacement is highly dependent on the right combination of engineering...

Human-hepatoblastoma-derived cell line, HepG2, has been widely used in liver and liver cancer studies. HepG2 spheroids produced in a three-dimensional (3D) culture system provide a better biological model than cells cultured in a two-dimensional (2D) culture system. Since cells at the center of spheroids exhibit specific behaviors attributed to hyp...

In the field of tissue engineering, fibroblast growth factor-2 (FGF-2) effectively regenerates damaged tissue and restores its biological function. However, FGF-2 readily diffuses and degrades under physiological conditions. Therefore, methods for the sustained and localized delivery of FGF-2 are needed. Drug delivery systems using hydrogels as car...

The study of the capillary-like network formation of human umbilical vein endothelial cells (HUVECs) in vitro is important for understanding the factors that promote or inhibit angiogenesis. Here, we report the behavior of HUVECs on the composite hydrogels containing hyaluronic acid (HA) and gelatin with different degrees of degradation, inducing t...

The fabrication of mature engineered cardiac tissue is one of the major challenges in cardiac tissue engineering. For this purpose, we attempted to apply the 3D bioprinting approach. Aiming to construct an oriented tissue, a fine fiber-shaped scaffold with a support structure was first designed using CAD software. Then, a 3D bioprinter and cell-adh...

The delivery of nucleic acids is indispensable for tissue engineering and gene therapy. However, the current approaches involving DNA/RNA delivery by systemic and local injections face issues such as clearance, off-target distribution, and tissue damage. In this study, we report plasmid DNA (pDNA) delivery using gelatin electrospun nanofibers obtai...

Non-adherent cells, such as hematopoietic cells and lymphocytes, are important research subjects in medical and biological fields. Therefore, a system that enables the handling of non-adherent cells in solutions in the same manner as that of adhering cells during medium exchange, exposure to chemicals, washing, and staining in imaging applications...

Background Hydrogels based on organic/inorganic composites have been at the center of attention for the fabrication of engineered bone constructs. The establishment of a straightforward 3D microenvironment is critical to maintaining cell-to-cell interaction and cellular function, leading to appropriate regeneration. Ionic cross-linkers, Ca2+, Ba2+,...

Engineering skeletal muscle tissue in vitro is important to study the mechanism of myogenesis, which is crucial for regenerating muscle cells. The physicochemical properties of the cellular microenvironment are known to govern various cell behaviours. Yet, most studies utilised synthetic materials to model the extracellular matrix that suffers from...

Engineering the surfaces of biological organisms allows the introduction of novel functions and enhances their native functions. However, studies on surface engineering remained limited to unicellular organisms. Herein, nematode surfaces are engineered through in situ hydrogelation mediated by horseradish peroxidase (HRP) anchored to nematode cutic...

Silk fibroin (SF) is an attractive material for composing bioinks suitable for three-dimensional (3D) bioprinting. However, the low viscosity of SF solutions obtained through common dissolution methods limits 3D-bioprinting applications without the addition of thickeners or partial gelation beforehand. Here, we report a method of 3D bioprinting low...

Gelatin electrospun nanofiber mats are gaining interest for applications in biomaterials science, such as tissue engineering and delivery systems. In this study, we report the use of electrospun gelatin nanofiber mats for plasmid DNA (pDNA) delivery. Gelatin nanofiber mats were insolubilized via cross-linking with glutaraldehyde. On the cross-linke...

Mucin‐containing bio‐synthetic hybrid hydrogel is successfully formed under physiological conditions upon mixing aqueous solutions of native mucin and synthetic polymers carrying boronic acids. The mechanical properties and stability of the hydrogel in physiological solutions, e.g., cell culture media, are tunable depending on the boronic acid cont...

The cell cycle is known to be regulated by features such as the mechanical properties of the surrounding environment and interaction of cells with the adhering substrates. Here, we investigated the possibility of regulating cell-cycle progression of the cells on gelatin/hyaluronic acid composite hydrogels obtained through hydrogen peroxide (H2O2)-m...

Ultrasound transmission gel has been normally used as a material fills the gap between the transducer of the ultrasound and patient’s skin. Alternatively, however, it can be used as a trial bioink for the 3D bio-printer, which is identified as one material for checking its printability at the preliminary phase. The purpose of this study was to clar...

With the development of the life science field, there is an increasing demand for measuring cell characteristics. In this background, we have developed a small microhand system that uses two end-effectors like chopsticks to grasp and carry micro-objects. We have also succeeded in measuring the stiffness of cells by installing a micro force sensor o...

In recent years, with the development of the life science field, there has been an increasing demand for the measurement of cell characteristics. In our laboratory, we developed a micro hand system that uses two end-effectors like chopsticks to grasp and manipulate objects. We also succeeded in measuring the stiffness of cells by installing a force...

Freeform bioprinting, realized by extruding ink-containing cells into supporting materials to provide physical support during printing, has fostered significant advances toward the fabrication of cell-laden soft hydrogel constructs with desired spatial control. For further advancement of freeform bioprinting, we aimed to propose a method in which t...

The addition of nano-hydroxyapatite (nHA) and collagen (Col) to the alginate (Alg) microcapsule hydrogel reduced swelling and degradation ratios while the compressive strength increased compared to Alg, Alg-Col, and Alg-nHA groups. MTT assay and Calcein-AM staining revealed an enhanced MG-63 osteoblasts viability in the Alg-nHA-Col hydrogel compare...

In this present work, we developed a phenol grafted polyglucuronic acid (PGU) and investigated the usefulness in tissue engineering field by using this derivative as a bioink component allowing gelation in extrusion-based 3D bioprinting. The PGU derivative was obtained by conjugating with tyramine, and the aqueous solution of the derivative was cur...

The present invention relates generally to polymeric compounds of glucuronic acid and a method of hydrogelation of such compounds. The present invention also relates to the use of the hydrogel structures (particles, films or 3D-structures) obtained by this method, notably as three-dimensional cell culture material to support biological molecules us...

Three-dimensional bioprinting has attracted much attention for biomedical applications, including wound dressing and tissue regeneration. The development of functional and easy-to-handle inks is expected to expand the applications of this technology. In this study, aqueous solutions of chitosan derivatives containing sodium persulfate (SPS) and Tri...

Hydrogen peroxide (H2O2) is widely used for the gelation of aqueous solutions of gelatin derivatives with phenolic hydroxyl groups (Gelatin- Ph) catalyzed by horseradish peroxidase (HRP). Apart from this, H2O2 is known to cause degradation/depolymerization of various polymers. Here, we prepared Gelatin-Ph hydrogels from solutions containing Gelatin...

Recently, with the development of life sciences, measurement of cell characteristics has been carried out to evaluate life phenomenon. The cell stiffness is one example of these characteristics and has much attentions. It is known that cell stiffness changes depending on the status of the cell. Thus, stiffness measurement is one of the important pa...

In this study, we developed a polysaccharide hydrogel for 3D bioprinting. 3D bioprinting is printing hydrogel containing cells or biocompatible materials by using 3D printer and it can be applied to tissue regeneration. It is important to develop a new hydrogel for bioprinting. Polysaccharide based hydrogel has high biocompatibility and it may have...

Here, we investigated the usefulness of silk fibroin nanofibers obtained via mechanical grinding of degummed silkworm silk fibers as an additive in bioinks for extrusion three-dimensional (3D) bioprinting of cell-laden constructs. The nanofibers could be sterilized by autoclaving, and addition of the nanofibers improved the shear thinning of polyme...

Gelatin-based water-insoluble nanofibers with a diameter of 160 nm were obtained from electrospinning aqueous solutions containing gelatin with phenolic hydroxyl (Ph) moieties (Gelatin-Ph) and horseradish peroxidase (HRP). The water insolubility of the nanofibers was accomplished through HRP-catalyzed cross-linking of the Ph moieties by exposing th...

We report an extrusion-based bioprinting approach, in which stabilization of extruded bioink is achieved through horseradish peroxidase (HRP)-catalyzed cross-linking consuming hydrogen peroxide (H2O2) supplied from HRP and glucose. The bioinks containing living cells, HRP, glucose, alginate possessing phenolic hydroxyl (Ph) groups, and cellulose na...

A simple fabrication method for cell micropatterns on hydrogel substrates was developed using an inkjet printing system that induced hydrogel micropatterns. The hydrogel micropatterns were created from inks resulting in cell-adhesive and non-cell-adhesive printed regions by horseradish peroxidase-catalyzed reaction onto non-cell-adhesive and cell-a...

Composite hydrogels of hyaluronic acid and gelatin attract great attention in biomedical fields. In particular, the composite hydrogels obtained through processes that are mild for cells are useful in tissue engineering. In this study, hyaluronic acid/gelatin composite hydrogels obtained through a blue light-induced gelation that is mild for mammal...

Three-dimensional (3D) bioprinting technology is now one of the best ways to generate new biomaterial for potential biomedical applications. Significant progress in this field since two decades ago has pointed the way toward use of natural biopolymers such as polysaccharides. Generally, these biopolymers such as alginate possess specific reactive g...

Boronic acid‐diol or boronate‐diol interactions have been used to construct molecular‐scale self‐assemblies. Nakahata et al. regard boronic acid as a functional cross‐linker to bridge different materials. Beginning from fundamental properties of boronic acids, recent research on functional nanomaterials cross‐linked with boronic acids is summarized...

In the present work, three kinds of reducing sugars: glucose, galactose, and mannose, are applied to horseradish peroxidase (HRP)-catalyzed hydrogelation of an aqueous solution containing natural polymers modified with phenolic hydroxyl moieties. In this system, HRP consumes hydrogen peroxide that generated from the oxidation of thiol groups in HRP...

Biofabrication is an emerging multidisciplinary field that makes a revolutionary impact on the researches on life science, biomedical engineering, and both basic and clinical medicine, has progressed tremendously over the past few years. Recently, there has been a big boom in three-dimensional (3D) printing or additive manufacturing (AM) research w...

Hydrogel microcapsules having the ability to promote cell adhesion and proliferation are a useful tool for fabricating tissue in vitro. The present study explored the effects of two anionic polysaccharide hydrogel membranes which have an impact on the adhesiveness, morphology and growth of cells. Microcapsules were made by coating a cell-laden gela...

Boronic acids are not only a substrate for metal‐catalyzed cross‐coupling but also a molecular recognition tool. Especially, boronic acid‐diol or boronate‐diol interactions have been used to construct molecular‐scale self‐assemblies. This focus review summarizes recent research using boronic acids as a bridge between similar or dissimilar (macro)mo...

Hydrogels were prepared by contacting air containing 10-50 ppm H2O2 with an aqueous solution containing polymer(s) possessing phenolic hydroxyl (Ph) moieties (polymer-Ph) and horseradish peroxidase (HRP). In this system, HRP catalyzes cross-linking of the Ph moieties by consuming H2O2 diffused from the air. The hydrogelation rate and mechanical pro...

Visible light-induced hydrogelation is attractive for various biomedical applications. In this study, hydrogels of alginate with phenolic hydroxyl groups (Alg-Ph) were obtained by irradiating a solution containing the polymer, ruthenium II trisbipyridyl chloride ([Ru(bpy)3]2+) and sodium persulfate (SPS), with visible light. The hydrogelation kinet...

Front Cover: Horseradish-peroxidase-catalyzed hydrogelation is combined with inkjet bioprinting technology for fabricating 3D cell-laden hydrogel constructs. The constructs are obtained by sequentially dropping a bioink containing hydrogen peroxide onto droplets of another bioink containing the enzyme and cells. Further details can be found in arti...

A cytocompatible inkjet bioprinting approach that enables the use of a variety of bioinks to produce hydrogels with a wide range of characteristics is developed. Stabilization of bioinks is caused by horseradish peroxidase (HRP)-catalyzed cross-linking consuming hydrogen peroxide (H2O2). 3D cell-laden hydrogels are fabricated by the sequential drop...

Gelling together: Horseradish peroxidase catalyzes crosslinking of phenol derivatives using hydrogen peroxide as the oxidant. In the aqueous solution containing polymer-possessing phenol moieties, enzyme-mediated crosslinking induces hydrogelation. The hydrogelation proceeds under mild reaction conditions for mammalian cells, at room temperature an...

Hydrogelation of aqueous solution of biocompatible macromolecules by mild chemical reaction is promising to be a universal technique in the field of biomaterials. This work demonstrates that the hydrogelation is achieved through dual enzymatic reactions using various kinds of oxidases (L-amino acid oxidase (L-AAOx), choline oxidase (ChOx), and gala...

In recent years, research subjects in tissue engineering and regenerative medicine have been shifting from simple tissues such as skin and cartilage to more complex tissues. Important biological tissues and organs are complicated structures in which various kinds of cells are densely arranged and capillary vessels are stretched. Currently, the deve...

Bioprinting has a great potential to fabricate three-dimensional (3D) functional tissues and organs. In particular, the technique enables fabrication of 3D constructs containing stem cells while maintaining cell proliferation and differentiation abilities, which is believed to be promising in the fields of tissue engineering and regenerative medici...

Horseradish peroxidase (HRP)-catalyzed hydrogelation has attracted much attention due to the ease of handling, high biocompatibility, and processability. This review summarizes recent developments including cutting-edge research using HRP-mediated hydrogelation toward biomedical, biopharmaceutical, and biofabrication applications. From the viewpoin...

Quantitative determination of toxic cyanide anions (CN⁻) in biological samples is an important subject. We synthesized a naphthalimide–coumarin conjugate with a simple imine linker (1), which behaves as a fluorescent receptor for ratiometric quantification of CN⁻. It exhibits green naphthalimide fluorescence at 533 nm, originating from the excited-...

Hydrogel fibers with biodegradable and biocompatible features are useful for the fabrication of filament-like tissues. We developed cell-laden hyaluronic acid (HA)-based hollow hydrogel fibers to create single and bundled filament-like tissues. The cell-laden fibers were fabricated by crosslinking phenolic-substituted hyaluronic acid (HA-Ph) in an...

Hydrogels were obtained from aqueous solution containing polymer(s) possessing phenolic hydroxyl moieties through horseradish peroxidase (HRP)-catalyzed reaction without direct addition of H2O2. In this hydrogelation process, H2O2 was generated from HRP and glucose contained in the aqueous solution, that is, HRP functioned not only as a catalyst, b...