A penicillinase-modified poly(N-isopropylacrylamide-co-acrylamide) smart hydrogel biosensor with superior recyclability for sensitive and colorimetric detection of penicillin G.

Antibiotics are widely used for treating bacterial infections. However, excessive or improper use of antibiotics can pose a serious threat to human health and water environments, and thus, developing cost-effective, portable and effective strategies to analyze and detect antibiotics is highly desired. Herein, we reported a responsive photonic hydrogel (RPH)-based optical biosensor (PPNAH) with superior recyclability for sensitive and colorimetric determination of a typical ß-lactam antibiotic penicillin G (PG) in water. This sensor was composed of poly(N-isopropylacrylamide-co-acrylamide) smart hydrogel with incorporated penicillinase and Fe3O4@SiO2 colloidal photonic crystals (CPCs). The sensor could translate PG concentration signals into changes in the diffraction wavelength and structural color of the hydrogel. It possessed high sensitivity and selectivity to PG and excellent detection performances for other two typical ß-lactam antibiotics. Most importantly, due to the unique thermosensitivity of the poly(N-isopropylacrylamide) moieties in the hydrogel, the PG-responded PPNAH sensor could be facilely regenerated via a simple physical method at least fifty times while without compromising its response performance. Besides, our sensor was suitable for monitoring the PG-contaminated environmental water and displayed satisfactory detection performances. Such a sensor possessed obvious advantages of superior recyclability, highly chemical stability, low production cost, easy fabrication, wide range of visual detection, simple and intuitive operation for PG detection, and environmental-friendliness, which holds great potential in sensitive and colorimetric detection of the PG residues in polluted water.

A K+-sensitive photonic crystal hydrogel sensor for efficient visual monitoring of hyperkalemia/hypokalemia.

Potassium ions (K+) play crucial roles in many biological processes. Abnormal K+ levels in the body are usually associated with physiological disorders or diseases, and thus, developing K+-sensitive sensors/devices is of great importance for disease diagnosis and health monitoring. Herein, we report a K+-sensitive photonic crystal hydrogel (PCH) sensor with bright structural colors for efficient monitoring of serum potassium. This PCH sensor consists of a poly(acrylamide-co-N-isopropylacrylamide-co-benzo-15-crown-5-acrylamide) (PANBC) smart hydrogel with embedded Fe3O4 colloidal photonic crystals (CPCs), which could strongly diffract visible light and endow the hydrogel with brilliant structural colors. The rich 15-crown-5 (15C5) units appended on the polymer backbone could selectively bind K+ ions to form stable 2 : 1 [15C5]2/K+ supramolecular complexes. These bis-bidentate complexes served as physical crosslinkers to crosslink the hydrogel and contracted its volume, and thus reduced the lattice spacing of Fe3O4 CPCs and blue-shifted the light diffraction, and finally reported on the K+ concentrations by a color change of the PCH. Our fabricated PCH sensor possessed high K+ selectivity and pH- and thermo-sensitive response performances to K+. Most interestingly, the K+-responding PANBC PCH sensor could be conveniently regenerated via simple alternate flushing with hot/cold water due to the excellent thermosensitivity of the introduced PNIPAM moieties into the hydrogel. Such a PCH sensor provides a simple, low-cost and efficient strategy for visualized monitoring of hyperkalemia/hypokalemia, which will significantly promote the development of biosensors.

A chiral magnetic molybdenum disulfide nanocomposite for direct enantioseparation of RS-propranolol.

We herein report a novel chiral magnetic molybdenum disulfide nanocomposite (MMoS2/PNG-CD) with a high enantioselectivity and excellent thermosensitivity and magnetism. The prepared MMoS2/PNG-CD shows temperature-dependent chiral discrimination and enantioselectivity toward a chiral drug RS-propranolol (RS-PPL), which is based on the molecular recognition ability of beta-cyclodextrin (ß-CD) and the thermosensitivity of poly(N-isopropylacrylamide) (PNIPAM). The synthesized MMoS2/PNG2-CD by using a monomer molar ratio of GMA to NIPAM of 2 : 1 demonstrates a high selectivity toward R-PPL over S-PPL due to the synergistic effect of the PNIPAM moieties and ß-CD hosts. The thermo-induced volume phase transition (VPT) of the introduced PNIPAM moieties significantly affects the inclusion constants of the ß-CD/R-PPL complex, and thus the loading and desorption of R-PPL on the MMoS2/PNG2-CD. The enantioselectivity at temperatures below the lower critical solution temperature (LCST) of the PNG-ß-CD grafting chains is much higher than that at temperatures above the LCST. As a result, the regeneration of the MMoS2/PNG2-CD is easily achieved via simply changing the operating temperature. Moreover, the regenerated MMoS2/PNG2-CD can be readily recovered from the RS-PPL solution under an external magnetic field for reuse. Such a multifunctional molybdenum disulfide nanocomposite with a high enantioselectivity and excellent thermosensitivity and regenerability is promising to serve as a high-performance nanoselector for direct resolution of various ß-blocker drugs.

Solvothermal synthesis of poly(acrylic acid) decorated magnetic molybdenum disulfide nanosheets for highly-efficient adsorption of cationic dyes from aqueous solutions.

Herein we report solvothermal synthesis of poly(acrylic acid) (PAA) decorated magnetic molybdenum disulfide nanosheets (MMoS2/PAA) for highly efficient adsorption of three cationic dyes of basic fuchsin (BF), methylene blue (MB), and crystal violet (CV) from aqueous solutions. The synthesized MMoS2/PAA was characterized by several techniques including transmission electron microscopy (TEM), Fourier transform-infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), vibrating sample magnetometry (VSM), and dynamic light scattering (DLS). Due to the strong electrostatic interaction between cationic dyes and the anionic nanosheet surface, the obtained MMoS2/PAA showed ultrafast adsorption of BF, MB and CV within 2 min with high adsorption capacities of 886.1, 709.0, and 633.6 mg g-1, respectively, much higher than those materials reported recently. PAA molecules bound on the nanosheets played a crucial role in significantly enhancing the dye adsorption. The adsorption kinetics and isotherms of three dyes onto the MMoS2/PAA were well described by the pseudo-second-order kinetic and the Langmuir models. Moreover, the MMoS2/PAA also exhibited high removal efficiencies for various mixed-dye solutions. Besides, such a functional nanomaterial could be effectively recovered from dye solutions under an external magnetic field and reused for dye adsorption without compromising on its performance indicating it can serve as an excellent adsorbent for effective removal of a variety of cationic organic pollutants from industrial effluents.

Novel Smart Polymer-Brush-Modified Magnetic Graphene Oxide for Highly Efficient Chiral Recognition and Enantioseparation of Tryptophan Enantiomers.

Multifunctional graphene oxide nanocomposites simultaneously possessing high enantioselectivity, excellent thermosensitivity, and magnetism demonstrate great application potentials in direct enantioseparation. We herein report one novel smart graphene oxide nanocomposite (MGO@PNG-CD) with high enantioselectivity, excellent thermosensitivity, and magnetism for highly efficient chiral identification and enantioseparation of tryptophan enantiomers. The MGO@PNG-CD is composed of graphene oxide nanosheets with immobilized superparamagnetic Fe3O4 nanoparticles and grafted PNG-CD smart polymer brushes. The PNG-CD is made up of poly(N-isopropylacrylamide-co-glycidyl methacrylate) (PNG) chains with numerous appended ß-cyclodextrin (ß-CD) units, which play a significant role in effective chiral discrimination and resolution of DL-tryptophan (DL-Trp). The ß-CD units serve as chiral selectors capable of selectively recognizing and binding L-tryptophan (L-Trp) into their cavities to form stable host-guest inclusion complexes of ß-CD/L-Trp. The PNIPAM chains in PNG act as a microenvironmental adjustor for the inclusion constants of ß-CD/L-Trp complexes. The resulted MGO@PNG-CD demonstrates high thermosensitive enantioselectivity toward L-Trp over D-Trp based on the chiral discrimination ability of ß-CD toward L-Trp and the thermosensitive volume phase transition of PNIPAM chains. Operating temperature and initial concentrations of DL-Trp are two significant factors affecting the separation efficiency of DL-Trp enantiomers. Moreover, the MGO@PNG-CD also displays satisfactory recycling and convenient magnetic separability from enantiomeric solution. Such a multifunctional graphene oxide nanocomposite developed in this study can serve as a high-performance nanoselector for highly efficient chiral recognition and enantioseparation of various chiral compounds.

A microfluidic approach to fabricate monodisperse hollow or porous poly(HEMA-MMA) microspheres using single emulsions as templates.

We have successfully developed a novel and simple method to controllably prepare monodisperse poly(hydroxyethyl methacrylate-methyl methacrylate) (poly(HEMA-MMA)) microspheres with two distinct structures using single emulsions as templates. By employing a microfluidic emulsification approach to fabricate monomer-contained oil-in-water (O/W) emulsions as templates, and introducing proper initiators and different types of porogens, poly(HEMA-MMA) microspheres with hollow or porous structure are prepared in a controllable way. The shell thickness of hollow microspheres or the porosity of porous microspheres is controllably achieved by simply adjusting the porogen concentration. The prepared poly(HEMA-MMA) microspheres with controllable hollow or porous structures are favored for various potential applications. Furthermore, by using the simple preparation methodology proposed in this study, fabrication of monodisperse porous microspheres or hollow microcapsules with other materials can also be easily achieved.

Preparation of monodisperse thermo-sensitive poly(N-isopropylacrylamide) hollow microcapsules.

We successfully developed a novel and simple method for preparation of monodisperse thermo-sensitive poly(N-isopropylacrylamide) (PNIPAM) hollow microcapsules at the interface of water-in-oil (W/O) single emulsions at a temperature below the lower critical solution temperature (LCST) of PNIPAM. The prepared PNIPAM microcapsules are featured with hollow structures and thin membranes, high monodispersity, excellent reversible thermo-sensitivity and fast response to environmental temperature. This approach exhibits great interests in preparing monodisperse thermo-sensitive microcapsules for encapsulating bioactive materials or drugs requiring mild encapsulation conditions, because of the flexibility in choosing substances being dissolved in the aqueous phase. The preparation methodology demonstrated in this study provides a unique approach for preparing monodisperse hollow polymeric microcapsules with W/O single emulsions.

Preparation of highly monodisperse W/O emulsions with hydrophobically modified SPG membranes.

Experimental investigations on the hydrophobic modification of SPG membranes and the preparation of monodisperse W/O (water-in-oil) emulsions using the modified membranes were carried out. Effects of the osmotic pressure of disperse phase, the average pore size of membranes, emulsifier concentrations in continuous phase and the transmembrane pressure on the average size, size distribution and size dispersion coefficient of emulsions were systematically studied. The stability of W/O emulsions was also investigated. The results showed that SPG membranes took on excellent hydrophobicity through the modification by silane coupler reagent (octyltriethoxysilane) or by silicone resin (polymethylsilsesquioxane). Monodisperse W/O emulsions with size dispersion coefficient of about 0.25, which meant high monodispersity, were successfully prepared by using the hydrophobically modified SPG membranes with average pore sizes of 1.8, 2.0, 2.5, 4.8 and 11.1 microm. When the osmotic pressure was lower than 0.855 MPa, the average size of emulsions was gradually increased while the size dispersion coefficient delta gradually decreased with the osmotic pressure; when the osmotic pressure was higher than 0.855 MPa, both the coefficients kept unvarying. When kerosene was saturated with disperse phase in advance, the average size of emulsions became larger and the monodispersity of emulsions was slightly better than that prepared using unsaturated kerosene. The smaller the pore size of SPG membranes was, the better the monodispersity of the W/O emulsions. The average size and size dispersion coefficient delta were nearly independent on the emulsifier concentrations when the PGPR concentration was in the range from 0.5 to 5.0 wt%, whereas both of them slightly increased as the PGPR concentration was below 0.5 wt%. The effect of the transmembrane pressure on size distributions was slight. Both the average size and size dispersion coefficient delta slightly increased to some extent with the increase of the transmembrane pressure in the experimental range. The stability of the W/O emulsions was dependent on the storage time. The mean size of W/O emulsions decreased gradually with the increase of storage time at the first 35 days, and then kept constant; while the size dispersion coefficient of W/O emulsions was nearly not changed.