Yu Hoshino

Peptide Imprinted Polymer Nanoparticles: A Plastic Antibody

A novel method for preparation of biomacromolecular imprinted nanoparticles is described. Combinations of functional monomers were polymerized in the presence of the imprinting peptide melittin in aqueous solution at room temperature to produce a small library of polymer nanoparticles. The template peptide and unreacted monomers are subsequently removed by dialysis. Nanoparticles (NPs) from the library were evaluated for their binding to melittin by 27 MHz QCM analysis. NPs prepared with optimized functional monomer combinations bind strongly to the target molecule. Nanoparticles that were polymerized in the absence of template peptide were found to have little affinity to the peptide. Binding affinity and the size of imprinted particles are comparable to those of natural antibodies. They interact specifically with the target peptide and show little affinity for other proteins. These NPs are of interest as inert and stable substitutes for antibodies. Extension of this approach to other targets of biological importance and the applications of these materials are currently being evaluated.

The rational design of a synthetic polymer nanoparticle that neutralizes a toxic peptide in vivo

Synthetic polymer nanoparticles (NPs) that bind venomous molecules and neutralize their function in vivo are of significant interest as “plastic antidotes.” Recently, procedures to synthesize polymer NPs with affinity for target peptides have been reported. However, the performance of synthetic materials in vivo is a far greater challenge. Particle size, surface charge, and hydrophobicity affect not only the binding affinity and capacity to the target toxin but also the toxicity of NPs and the creation of a “corona” of proteins around NPs that can alter and or suppress the intended performance. Here, we report the design rationale of a plastic antidote for in vivo applications. Optimizing the choice and ratio of functional monomers incorporated in the NP maximized the binding affinity and capacity toward a target peptide. Biocompatibility tests of the NPs in vitro and in vivo revealed the importance of tuning surface charge and hydrophobicity to minimize NP toxicity and prevent aggregation induced by nonspecific interactions with plasma proteins. The toxin neutralization capacity of NPs in vivo showed a strong correlation with binding affinity and capacity in vitro. Furthermore, in vivo imaging experiments established the NPs accelerate clearance of the toxic peptide and eventually accumulate in macrophages in the liver. These results provide a platform to design plastic antidotes and reveal the potential and possible limitations of using synthetic polymer nanoparticles as plastic antidotes.

Temperature-Responsive “Catch and Release” of Proteins by using Multifunctional Polymer-Based Nanoparticles†

Synthetic nanopartciles (NPs) with an intrinsic affinity for specific proteins are of considerable interest for their potential in biological/biomedical science and biotechnology.[1, 2, 3] In addition to their binding capability, synthetic materials offer the possibility for controlling binding affinity by external stimuli, including light, electromagnetic radiation and temperature;[4] a feature that can be used for remote modulation of capture or release of target proteins in a spatiotemporally controlled manner. In this communication, we report the synthesis and applications of a multifunctional polymer NP with selective protein affinity that can be modulated by external stimuli to “catch-and-release” the target protein.

Reversible Absorption of CO2 Triggered by Phase Transition of Amine-Containing Micro- and Nanogel Particles

Herein we report that an aqueous solution of temperature-responsive micro- and nanogel particles (GPs) consisting of N-isopropylacrylamide (NIPAm) and N-[3-(dimethylamino)propyl]methacrylamide (DMAPM) reversibly absorbs and desorbs CO(2) via a phase transition induced by cooling and heating cycles (30-75 °C). Below the phase-transition temperature, most of the amines in the swollen GPs are capable of forming ion pairs with absorbed bicarbonate ions. However, above the phase-transition temperature, shrinkage of the GPs lowers the pK(a) and the number of amine groups exposed to water, thereby resulting in almost complete desorption of CO(2). The GPs can reversibly absorb more than the DMAPM monomer and polymer without NIPAm, which indicates the importance of the temperature-responsive phase transition of polymers in determining the degree of absorption. The results show the potential of temperature-responsive polymer solutions as absorbents to sequester CO(2) at a low energy cost.

The evolution of plastic antibodies

Plastic antibodies, synthetic polymer nanoparticles with antibody-like functions, have emerged as potential alternatives to protein antibodies. This paper focuses on recent developments of plastic antibodies for biomacromolecules and their application as antitoxins.

Design of Synthetic Polymer Nanoparticles that Capture and Neutralize a Toxic Peptide

Designed polymer nanoparticles (NPs) capable of binding and neutralizing a biomacromolecular toxin are prepared. A library of copolymer NPs is synthesized from combinations of functional monomers. The binding capacity and affinity of the NPs are individually analyzed. NPs with optimized composition are capable of neutralizing the toxin even in a complex biological milieu. It is anticipated that this strategy will be a starting point for the design of synthetic alternatives to antibodies.

Temperature-Responsive Microgel Films as Reversible Carbon Dioxide Absorbents in Wet Environment†

Hydrogel films composed of temperature-responsive microgel particles (GPs) containing amine groups work as stimuli-responsive carbon dioxide absorbent with a high capacity of approximately 1.7 mmol g(-1). Although the dried films did not show significant absorption, the reversible absorption capacity dramatically increased by adding a small amount of water (1 mL g(-1)). The absorption capacity was independent of the amount of added water beyond 1 mL g(-1), demonstrating that the GP films can readily be used under wet conditions. The amount of CO2 absorbed by the GP films was proportional to their thickness up to 200-300 μm (maximum capacity of about 2 L m(-2) . Furthermore, the films consisting of GPs showed faster and greater absorption and desorption of CO2 than that of monolithic hydrogel films. These results indicated the importance of a fast stimulus response rate of the films that are composed of GPs in order to achieve long-range and fast diffusion of bicarbonate ions. Our study revealed the potential of stimuli-responsive GP films as energy-efficient absorbents to sequester CO2 from high-humidity exhaust gases.

Polymer Nanoparticle–Protein Interface. Evaluation of the Contribution of Positively Charged Functional Groups to Protein Affinity

Cationic-functionalized polymer nanoparticles (NPs) show strikingly distinct affinities to proteins depending on the nature of the cationic functional group. N-Isopropylacrylamide (NIPAm) polymer NPs incorporating three types of positively charged functional groups (guanidinium, primary amino, and quaternary ammonium groups) were prepared by precipitation polymerization. The affinities to fibrinogen, a protein with an isoelectric point (pI) of 5.5, were compared using UV-vis spectrometry and a quartz crystal microbalance (QCM). Guanidinium-containing NPs showed the highest affinity to fibrinogen. The observation is attributed to strong, specific interactions with carboxylate groups on the protein surface. The affinity of the positively charged NPs to proteins with a range of pIs revealed that protein-NP affinity is due to a combination of ionic, hydrogen bonding, and hydrophobic interactions. Protein affinity can be modulated by varying the composition of these functional monomers in the acrylamide NPs. Engineered NPs containing the guanidinium group with hydrophobic and hydrogen bonding functional groups were used in an affinity precipitation for the selective separation of fibrinogen from a plasma protein mixture. Circular dichroism (CD) revealed that the protein was not denatured in the process of binding or release.

Polymer-modified gold nanoparticles via RAFT polymerization: A detailed study for a biosensing application

Glycopolymers of polyacrylamide derivatives with mannose were prepared via the living radical polymerization of a reversible addition–fragmentation chain transfer reagent. The polymers obtained showed narrow polydispersities. The polymer terminal group was reduced to a thiol, and the resulting polymers were mixed with gold nanoparticles to prepare glycopolymer-substituted gold nanoparticles. The mannose density was adjusted by varying the copolymer preparation and the glycopolymer–polyacrylamide mixture. The colloidal stability of the polymer-coated gold nanoparticles is dependent on the mannose density. Polymer-coated nanoparticles with low mannose densities showed better colloidal stabilities. The molecular recognition abilities of the polymer were investigated using UV-vis spectroscopy. The polymer-coated nanoparticles showed strong protein recognition abilities because of multivalent binding effects. Polymers with high mannose densities showed stronger recognition abilities. The molecular recognition abilities of the glycopolymer–polyacrylamide mixed nanoparticles are dependent on the mannose density. An immunochromatographic assay was performed using the polymer-coated nanoparticles. The color was detected from the gold nanoparticles in the nanoparticle systems with strong molecular recognition and good colloid stability.

Selective Protein Separation Using Siliceous Materials with a Trimethoxysilane-Containing Glycopolymer

A copolymer with α-D-mannose (Man) and trimethoxysilane (TMS) units was synthesized for immobilization on siliceous matrices such as a sensor cell and membrane. Immobilization of the trimethoxysilane-containing copolymer on the matrices was readily performed by incubation at high heat. The recognition of lectin by poly(Man-r-TMS) was evaluated by measurement with a quartz crystal microbalance (QCM) and adsorption on an affinity membrane, QCM results showed that the mannose-binding protein, concanavalin A, was specifically bound on a poly(Man-r-TMS)-immobilized cell with a higher binding constant than bovine serum albumin. The amount of concanavalin A adsorbed during permeation through a poly(Man-r-TMS)-immobilized membrane was higher than that through an unmodified membrane. Moreover, the concanavalin A adsorbed onto the poly(Man-r-TMS)-immobilized membrane was recoverable by permeation of a mannose derivative at high concentration.