Papers by Akihiro Kishimura
Journal of Materials Chemistry B, Dec 31, 2023
In nanomedicine, PEGylation of nanomaterials poses a dilemma since it inhibits their interaction ... more In nanomedicine, PEGylation of nanomaterials poses a dilemma since it inhibits their interaction with target cells and enables their retention in target tissues despite its biocompatibility and nonspecific internalisation suppression. PEGylated polypeptide-based polyion complexes (PICs) are fabricated via the self-assembly of PEGylated aniomers and homocatiomers based on electrostatic interactions. We propose that various parameters like block copolymer design and PIC domain characteristics can enhance the cell-PEGylated PIC interactions. Remarkably, the properties of the PIC domain were tuned by the matched/mismatched ionomer chain lengths, PIC domain crosslinking degree, chemical modification of cationic species after crosslinking, PIC morphologies (vesicles/micelles) and polyethylene glycol (PEG) chain lengths. Cellular internalisation of the prepared PICs was evaluated using HeLa cells. Consequently, mismatched ionomer chain lengths and vesicle morphology enhanced cell-PIC interactions, and the states of ion pairing, particularly cationic residues, affected the internalisation behaviours of PICs via acetylation or guanidinylation of amino groups on catiomers. This treatment attenuated the cell-PIC interactions, possibly because of reduced interaction of PICs with negatively charged species on the cell-surface, glycosaminoglycans. Moreover, morphology and PEG length were correlated with PIC internalisation, in which PICs with longer and denser PEG were internalised less effectively. Cell line dependency was tested using RAW 264.7 macrophage cells; PIC recognition could be maintained after capping amino groups on catiomers, indicating that the remaining anionic groups were still effectively recognised by the scavenger receptors of macrophages. Our strategy for tuning the physicochemical properties of the PEGylated PIC nanocarriers is promising for overcoming the PEG issue.
Drug Delivery System, Jul 25, 2019
Nanomedicine: Nanotechnology, Biology and Medicine, Jul 1, 2018
Polymer Journal, Oct 9, 2013
Much attention has been devoted to precise control of the size and morphology in nanosized molecu... more Much attention has been devoted to precise control of the size and morphology in nanosized molecular assemblies for a wide range of materials applications. Recently, we reported observing submicron/nanosized polyion complex vesicles (Nano-PICsomes) with a narrow size distribution, synthesized using specific types of homocatiomers and polyethylene glycol (PEG)-based block aniomers. However, only one example of Nano-PICsomes has been reported to date. Here, the role of the chemical composition of PEG-based block aniomers and the chemical structures of the side chains of homocatiomers were carefully examined to better understand the formation of Nano-PICsomes. Transmission electron microscopy and dynamic light scattering analyses of Nano-PICsomes revealed that a longer length of ionic segments in the block aniomers or a PEG weight fraction (f PEG) o10%, is required for the selective formation of Nano-PICsomes, whereas polymer combinations with f PEG 410% produced spherical micelles. In addition, the homocatiomers containing longer aliphatic side chains (e.g., five or six carbon atoms) favored the formation of Nano-PICsomes, whereas those containing shorter aliphatic side chains produced irregularly shaped PIC micelles. Accordingly, f PEG and the length of the side chain were found to be the key factors that control the morphologies of Nano-PICsomes. Insights gained from this study can broaden the spectrum of the design of Nano-PICsomes for use in a diverse range of material applications.
Chemistry Letters, Nov 5, 2022
Chemical Communications, 2020
A photo-responsive nanovesicle is fabricated by polyion complex (PIC) formation between poly(ethy... more A photo-responsive nanovesicle is fabricated by polyion complex (PIC) formation between poly(ethylene glycol) (PEG)-block-polypeptides and photo-reactive oligodeoxynucleotides (PROs)/anti-sense oligonucleotides (ASOs). The ultraviolet (UV) light triggers reversible crosslinking between PROs and ASOs in the vesicular membrane, providing the nanovesicle with switchable stability under physiological conditions. The resulting nanovesicle allows efficient cellular internalization, leading to significant UV-triggered gene knockdown in cultured cells.
Biomacromolecules, Sep 14, 2020
For the simultaneous delivery of antisense oligonucleotides and their effector enzymes into cells... more For the simultaneous delivery of antisense oligonucleotides and their effector enzymes into cells, nanosized vesicular polyion complexes (PICs) were fabricated from oppositely charged polyionpairs of oligonucleotides and poly(ethylene glycol) (PEG)-b-polypeptides. First, the polyion component structures were carefully designed to facilitate multimolecular (or secondary) association of unit PICs for non-covalent (or chemical crosslinking-free) stabilization of vesicular PICs. Chemically modified, single-stranded oligonucleotides (SSOs) dramatically stabilized the multimolecular associates under physiological conditions, compared to control SSOs without chemical modifications and duplex oligonucleotides. In addition, a high degree of guanidino groups in the polypeptide segment was also crucial for the high stability of multimolecular associates. Dynamic light scattering and transmission electron microscopy revealed the stabilized multimolecular associates to have a 100 nm-sized vesicular architecture with a narrow size distribution. The loading number of SSOs per nanovesicle was determined to be ~2,500 by using fluorescence correlation spectroscopic analyses with fluorescently labeled SSOs. Furthermore, the nanovesicle stably encapsulated ribonuclease H (RNase H) as an effector enzyme at ~10 per nanovesicle through simple vortex-mixing with preformed nanovesicles. Ultimately, the RNase H-encapsulated nanovesicle efficiently delivered SSOs with RNase H into cultured cancer cells, thereby eliciting the significantly higher gene knockdown compared with empty nanovesicles (without RNase H) or a mixture of nanovesicles with RNase H without encapsulation. These results demonstrate the great potential of non-covalently stabilized nanovesicles for the codelivery of two varying biomacromolecule payloads for ensuring their cooperative biological activity.
Science and Technology of Advanced Materials, Jun 20, 2015
Introduction of ligands into 100 nm scaled hollow capsules has great potential for diagnostic and... more Introduction of ligands into 100 nm scaled hollow capsules has great potential for diagnostic and therapeutic applications in drug delivery systems. Polyethylene glycol-conjugated (PEGylated) polyion complex vesicles (PICsomes) are promising hollow nano-capsules that can survive for long periods in the blood circulation and can be used to deliver water-soluble macromolecules to target tissues. In this study, cyclic RGD (cRGD) peptide, which is specifically recognized by α V β 3 and α v β 5 integrins that are expressed at high levels in the neovascular system, was conjugated onto the distal end of PEG strands on PICsomes for active neovascular targeting. Density-tunable cRGD-conjugation was achieved using PICsomes with definite fraction of endfunctionalized PEG, to substitute 20, 40, and 100% of PEG distal end of the PICsomes to cRGD moieties. Compared with control-PICsomes without cRGD, cRGD-PICsomes exhibited increased uptake into human umbilical vein endothelial cells. Intravital confocal laser scanning microscopy revealed that the 40%-cRGD-PICsomes accumulated mainly in the tumor
Journal of the American Chemical Society, Feb 7, 2019
Vesicular polyion complexes (PICs) were fabricated through self-assembly of rigid cylindrical mol... more Vesicular polyion complexes (PICs) were fabricated through self-assembly of rigid cylindrical molecules, small interfering RNAs (siRNAs), with flexible block catiomers of poly(ethylene glycol) (2 kDa) and cationic polyaspartamide derivative (70 units) bearing a 5-aminopentyl side chain. 100 nm-sized siRNA-assembled vesicular PICs, termed siRNAsomes, were fabricated in specific mixing ranges between siRNA and block catiomer. The siRNAsome membrane was revealed to consist of PIC units fulfilling a simple molar ratio (1:2 or 2:3) of block catiomer and siRNA. These ratios correspond to the minimal integer molar ratio to maximally compensate the charge imbalance of PIC, because the numbers of charges per block catiomer and siRNA are +70 and -40, respectively. Accordingly, the ζ-potentials of siRNAsomes prepared at 1:2 and 2:3 were negative and positive, respectively. Cross-section transmission electron microscopic observation clarified that the membrane thicknesses of 1:2 and 2:3 siRNAsomes were 11.0 and 17.2 nm, respectively. Considering that a calculated long-axial length of siRNA is 5.9 nm, these thickness values correspond to the membrane models of two (11.8 nm) and three (17.7 nm) tandemly aligned siRNAs associating with one and two block catiomers, respectively. For biological application, siRNAsomes were stabilized through membrane-cross-linking with glutaraldehyde. The positively charged and cross-linked siRNAsome facilitated siRNA internalization into cultured cancer cells, eliciting significant gene silencing with negligible cytotoxicity. The siRNAsome stably encapsulated dextran as a model cargo macromolecule in the cavity by simple vortex mixing. Confocal laser scanning microscopic observation displayed that both of the payloads were internalized together into cultured cells. These results demonstrate the potential of siRNAsomes as a versatile platform for codelivery of siRNA with other cargo macromolecules.
Drug Delivery System, Jan 25, 2022
Answering to social issues-How can we build and utilize a backcasting-approach-based open innovat... more Answering to social issues-How can we build and utilize a backcasting-approach-based open innovation platform? In the present article, we propose a new style of open innovation as an approach to solve unsolved issues "不 (Fu) " of Japanese companies as well as societal issues in Japan ("Fu" of Japanese society) based on a backcasting approach. Also, we introduce the Open Science Platform promoted by Kyushu University as an practical example of such a new open innovation platform.
International Journal of Pharmaceutics, 2020
Biological & Pharmaceutical Bulletin, Sep 1, 2020
Enhancing blood flow to tumors is a prominent strategy for improving the tumor accumulation of ma... more Enhancing blood flow to tumors is a prominent strategy for improving the tumor accumulation of macromolecular drugs through the enhanced permeability and retention (EPR) effect. IRL-1620 is an agonist of the endothelin B receptor, and is a promising molecule to enhance tumor blood flow by activating endothelial nitric oxide synthase. However, contradictory effects on tumor blood flow modulation have been reported because the effects of IRL-1620 may differ in different animal models. Here, we examined for the first time the effect of IRL-1620 on the EPR effect for PEGylated liposomes in a CT-26 murine colon cancer model. Co-injection of IRL-1620 at an optimum dose (3 nmol/kg) nearly doubled the tumor accumulation of liposomes compared with controls, indicating that IRL-1620 enhanced the EPR effect in the present colon cancer model. Co-injection of IRL-1620 is a promising strategy to improve the therapeutic effects of macromolecular drugs while reducing their side effects.
55th Society of Polymer Science Japan Symposium on Macromolecules, 2006
Journal of Biomaterials Science-polymer Edition, Jun 19, 2015
We synthesized polymeric gene carriers consisting of poly-L-lysine (PLL) main chain modified both... more We synthesized polymeric gene carriers consisting of poly-L-lysine (PLL) main chain modified both with substrate peptide for protein kinase Cα (PKCα) and alkanethiol (pentadecanethiol). Due to the grafted substrate peptide, the polyplex prepared from these carriers are expected to show gene expression triggered by the phosphorylation of the peptide by intracellular PKCα. The modified alkanethiol on the main chain stabilized the polyplex both via disulfide crosslinking and hydrophobic interaction. The polyplex found to show gene expression in vitro when the alkanethiol content in the main chain was enough low (4-mol%-modification of PLL&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s ε-amine group) to minimize cytotoxic effect. Even though the low content of alkanethiol, the polyplex had significant stability in a model serum solution and showed longer blood circulation in vivo. The polyplex clearly accumulated in tumor after intravenous injection.
Macromolecular Rapid Communications, Jun 16, 2022
Developing nanovehicles for delivering antibiotics is a promising approach to overcome the issue ... more Developing nanovehicles for delivering antibiotics is a promising approach to overcome the issue of antibiotic resistance. This study aims to utilize a polyion complex (PICs) system for developing novel nanovehicles for polymyxin‐type antibiotics, which are known as last resort drugs. The formation of antibiotic‐based PIC nanostructures is investigated using colistimethate sodium (CMS), an anionic cyclic short peptide, and a series of block catiomers bearing different amounts of guanidinium moieties on their side chains. In addition, only the modified catiomer, and not the unmodified catiomer, self‐assembles with CMS, implying the importance of the guanidine moieties for enhancing the interaction between the catiomer and CMS via the formation of multivalent hydrogen bonding. Moreover, micellar and vesicular PIC nanostructures are selectively formed depending on the ratio of the guanidine residues. Size‐exclusion chromatography reveals that the encapsulation efficiency of CMS is dependent on the guanidinium modification ratio. The antimicrobial activity of the PIC nanostructures is also confirmed, indicating that the complexation of CMS in the PICs and further release from the PICs successfully occurs.
Physical Chemistry Chemical Physics, 2018
Contrast-variation small-angle neutron scattering (CV-SANS), small-angle X-ray scattering (SAXS),... more Contrast-variation small-angle neutron scattering (CV-SANS), small-angle X-ray scattering (SAXS), nuclear magnetic resonance (NMR) measurements of diffusion and isothermal titration calorimetry (ITC) are used to gain insight into the aggregation of an alkyl-C 60 derivative, molecule 1, in n-hexane, n-decane and toluene as a function of concentration and temperature. Results point to an associative mechanism of aggregation similar to other commonly associating molecules, including non-ionic surfactants or asphaltenes in non-aqueous solvents. Little aggregation is detected in toluene, but small micelle-like structures form in n-alkane solvents, which have a C 60-rich core and alkyl-rich shell. The greatest aggregation extent is found in n-hexane, and at 0.1 M the micelles of 1 comprise around 6 molecules at 25 1C. These micelles become smaller when the concentration is lowered, or if the solvent is changed to n-decane. The solution structure is also affected by temperature, with a slightly larger aggregation extent at 10 1C than at 25 1C. At higher concentrations, for example in solutions of 1 above 0.3 M in n-decane, a bicontinuous network becomes apparent. Overall, these findings aid our understanding of the factors driving the assembly of alkyl-p-conjugated hydrophobic amphiphiles such as 1 in solution and thereby represent a step towards the ultimate goal of exploiting this phenomenon to form materials with well-defined order.
Bioconjugate Chemistry, Jan 11, 2017
We developed a strategy to modify cell membranes with an artificial transmembrane receptor. Coulo... more We developed a strategy to modify cell membranes with an artificial transmembrane receptor. Coulomb force on the receptor, caused by the membrane potential, was used to achieve membrane penetration. A hydrophobically modified cationic peptide was used as a membrane potential sensitive region that was connected to biotin through a transmembrane oligoethylene glycol (OEG) chain. This artificial receptor gradually disappeared from the cell membrane via penetration despite the presence of a hydrophilic OEG chain. However, when the receptor was bound to streptavidin (SA), it remained on the cell membrane because of the large and hydrophilic nature of SA.
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Papers by Akihiro Kishimura