Loading and Release of Charged Dyes Using Ultrathin Hydrogels

The anionic dyes methyl orange (MO) and allura red (AR) were used as model drugs to assess the loading and release by layer-by-layer assembled ultrathin hydrogels prepared via the amide formation of poly(acrylic acid-co-N-isopropylacrylamide) with AAc contents of 5, 10, and 15 mol % plus poly(vinylamine hydrochloride). The amount of MO loaded was potentially controlled by changing the dye concentrations, film thickness, and AAc content of the copolymers. The release of AR was controlled by the NaCl concentration and pH. We conclude that the polymeric matrices of ultrathin hydrogels have great potential for the loading and release of charged drugs

Novel Synthetic Route to Peptide-Capped Gold Nanoparticles

A novel synthetic route to peptide-capped gold nanoparticles was demonstrated herein. Tetrachloroaurate ions were reduced with 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid (HEPES) under extremely mild conditions (pH 7.2, ambient temperature) in the presence of cysteine-terminal desired peptides, so that peptide-capped spherical nanoparticles were successfully synthesized. Model basic peptides containing the Arg-Pro-Thr-Arg sequence, which is an essential motif that specifically binds to film surfaces composed of isotactic poly(methyl methacrylate), were employed. Particle sizes were approximately 10 nm, and size distributions were narrow. Positive zeta potentials of nanoparticles suggested the presence of the Arg-Pro-Thr-Arg sequence on the outermost surface. Thermogravimetric analysis revealed that peptides were closely packed on the gold’s surface. Parameters affecting reaction rates such as peptide structures and concentrations were investigated. Native peptide functions were conserved on nanoparticles by introducing a certain spacer between cysteine and the Arg-Pro-Thr-Arg sequence, suggesting that designing suitable peptide structures is essential to conserve peptide functions

Adhesion of Two Physically Contacting Planar Substrates Coated with Layer-by-Layer Assembled Films

Adhesives composed of synthetic and low-cost molecules that are based on simple chemical principles are attractive because of their versatility. In this article, we report adhesion between two planar substrates coated with layer-by-layer (LbL) assembled films of cationic poly(diallyldimethylammonium chloride) (PDDA) and anionic poly(sodium styrenesulfonate) (PSS) and perform lap shear measurements of the adhered substrates. Films prepared on the substrates functioned as adhesives when one substrate coated with the PDDA−surface film contacted the other surface coated with the PSS−surface film under adequate pressure in the presence of water droplets, suggesting that two films adhered on the basis of polyion complex formation. Observations suggested that the adhesives failed at the substrate−film interface rather than at the bulk films. The adhesion was compared between film-coated substrates and noncoated ones. Confocal laser scanning microscopic observation of adhesives composed of fluorescently labeled poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) revealed that the labeled PAH assembled on one substrate was well dispersed, even in a nonlabeled film assembled on another substrate. It was therefore confirmed that after adhesion in the presence of the water component, the polyelectrolytes became intermixed between the glassy films, resulting in changes in the adhesive structure at the substrate−film interface

Rapid Deswelling of Porous Poly(<i>N</i>-isopropylacrylamide) Hydrogels Prepared by Incorporation of Silica Particles

Rapid Deswelling of Porous Poly(N-isopropylacrylamide) Hydrogels Prepared by Incorporation of Silica Particle

Identification of Water-Soluble Polymers through Machine Learning of Fluorescence Signals from Multiple Peptide Sensors

Recently, there has been growing concern about the discharge of water-soluble polymers (especially synthetic polymers) into the environment. Therefore, the identification of water-soluble polymers in water samples is becoming increasingly crucial. In this study, a chemical tongue system to simply and precisely identify water-soluble polymers using multiple fluorescently responsive peptide sensors was demonstrated. Fluorescence spectra obtained from the mixture of each peptide sensor and water-soluble polymer were changed depending on the combination of the polymer species and peptide sensors. Water-soluble polymers were successfully identified through the supervised or unsupervised machine learning of multidimensional fluorescence signals from the peptide sensors

Synthesis and Characterization of Poly(<i>N</i>-isopropylacrylamide)-Coated Polystyrene Microspheres with Silver Nanoparticles on Their Surfaces^†

Dispersion copolymerization of styrene and a poly(N-isopropylacrylamide) macromonomer in ethanol−water media has been successfully carried out in the presence of AgNO3. Nearly monodisperse polystyrene microspheres with diameters ranging from 530 to 1250 nm were obtained. Nanoscopic silver particles were generated on their surfaces via in situ reduction of Ag+ by radicals generated from the initiator, 2,2‘-azobisisobutyronitrile (AIBN). The particle sizes of both polystyrene microspheres and silver nanoparticles were affected by the initial AIBN, AgNO3, and macromonomer concentrations. The diameters of the silvered microspheres and silver nanoparticles followed the relationships Dn ∝ [AIBN]0-0.107 [AgNO3]00.083[macromonomer]0-0.533 and dn ∝ [AIBN]00.027 [AgNO3]00.173 [macromonomer]0-0.137, respectively. Over 95.8% of the silver ions are converted into zerovalent metal and immobilized on the microspheres, according to atomic absorption spectroscopy measurements. The silvered microspheres were characterized by transmission electron microscopy, atomic force microscopy, and FTIR, UV−visible, and X-ray photoelectron spectroscopy. The surface-grafted PNIPAAm chains were found not only to serve as steric stabilizers to prevent the flocculation of the polystyrene particles but also to adsorb the Ag nanoparticles onto the surface of the microspheres. A mechanism for the formation of silvered polystyrene microspheres in dispersion copolymerization was presented

Biological Identification of Peptides that Specifically Bind to Poly(phenylene vinylene) Surfaces: Recognition of the Branched or Linear Structure of the Conjugated Polymer

Peptides that bind to poly(phenylene vinylene) (PPV) were identified by the phage display method. Aromatic amino acids were enriched in these peptide sequences, suggesting that a π−π interaction is the key interaction between the peptides and PPV. The surface plasmon resonance (SPR) experiments using chemically synthesized peptides demonstrated that the Hyp01 peptide, with the sequence His-Thr-Asp-Trp-Arg-Leu-Gly-Thr-Trp-His-His-Ser, showed an affinity constant (7.7 × 105 M−1) for the target, hyperbranched PPV (hypPPV) film. This value is 15-fold greater than its affinity for linear PPV (linPPV). In contrast, the peptide screened for linPPV (Lin01) showed the reverse specificity for linPPV. These results suggested that the Hyp01 and Lin01 peptides selectively recognized the linear or branched structure of PPVs. The Ala-scanning experiment, circular dichroism (CD) spectrometry, and molecular modeling of the Hyp01 peptide indicated that adequate location of two Trp residues by forming the polyproline type II (PII) helical conformation allowed the peptide to specifically interact with hypPPV

Affinity-Based Functionalization of Biomedically Utilized Micelles Composed of Triblock Copolymers through Polymer-Binding Peptides

Polymeric micelles and vesicles that are self-assembled from amphiphilic block copolymers are frequently used in biomedical applications. Poly­(ethylene oxide) (PEO)–poly­(propylene oxide) (PPO)–PEO, so-called Pluronic, is a Food and Drug Administration approved triblock copolymer utilized in biomedical applications. However, the control of drug loading and surface functionalization of micelles remain challenging due to structural limitations. In this study, Pluronic micelles with various structures were rationally functionalized via the PPO-binding peptide, which was previously identified using a biologically constructed peptide library displayed on filamentous phages. The interactions between the peptide and Pluronic micelles were characterized in detail based on fluorescence changes in an extrinsic fluorescence dye, and a sufficient PPO chain length of Pluronic was essential for the interactions. Furthermore, enzymatic degradation of the model substrate-conjugated peptide loaded into Pluronic micelles showed stable loading of the peptide. Importantly, the exposure level of the conjugated molecules to the peptide was dependent on the PEO chain length of Pluronic, suggesting controllable functionalization of polymeric micelles. Anticancer drug-conjugated peptide-loaded Pluronic micelles with suitable polymeric structures were applied in a cell culture assay. The anticancer efficacy of the loaded drugs can be controlled by the molecular design of the binding peptide and polymers. These results demonstrate that an affinity-based functionalization strategy may facilitate polymeric micelles for various biomedical applications

Identification of Water-Soluble Polymers through Discrimination of Multiple Optical Signals from a Single Peptide Sensor

The pollution of water environments is a worldwide concern. Not only marine pollution by plastic litter, including microplastics, but also the spillage of water-soluble synthetic polymers in wastewater have recently gained increasing attention due to their potential risks to soil and water environments. However, conventional methods to identify polymers dissolved in water are laborious and time-consuming. Here, we propose a simple approach to identify synthetic polymers dissolved in water using a peptide-based molecular sensor with a fluorophore unit. Supervised machine learning of multiple fluorescence signals from the sensor, which specifically or nonspecifically interacted with the polymers, was applied for polymer classification as a proof of principle demonstration. Aqueous solutions containing different polymers or multiple polymer species with different mixture ratios were identified successfully. We found that fluorophore-introduced biomolecular sensors have great potential to provide discriminative information regarding water-soluble polymers. Our approach based on the discrimination of multiple optical signals of water-soluble polymers from peptide-based molecular sensors through machine learning will be applicable to next-generation sensing systems for polymers in wastewater or natural environments

Template Polymerization Using Artificial Double Strands

Template Polymerization Using Artificial Double Strand