Uniform poly(isopropylacrylamide) gel beads for immobilization of ?-chymotrypsin

Enzyme-Powered Hollow Nanorobots for Active Microsampling Enabled by Thermoresponsive Polymer Gating

Achieving molecular sample capture at micro/nanoscales while integrating functions of controllable loading and real-time monitoring of cargo molecules is of great significance in the development of intelligent micro/nanorobots. Herein, we prepare a temperature-responsive microsampling nanorobot by encapsulating metal (Au) nanodots inside hollow mesoporous silica nanoparticles and grafting a temperature-responsive polymer, poly(N-isopropylacrylamide), on their external surface. The molecular gate of nanochannels accessing the internal hollow reservoir can be switched between "open" and "closed" states by regulating the temperature, allowing on-demand loading and releasing of small molecules. The internally embedded surface-enhanced Raman scattering hotspots of gold nanodots can serve as sensing probes for real-time detection of the molecular cargo load inside the hollow nanorobots. Furthermore, we demonstrate temperature-dependent self-propulsion behavior of the nanorobots driven by enzymatic reactions. The active motion behavior can favorably regulate the loading efficiency of molecular cargos. In addition, by further introducing the magnetic component Ni, the nanorobots can accomplish effective transportation of cargo molecules by magnetic guidance under real-time Raman monitoring. The current strategy is expected to provide a manipulable nanorobot platform for precise biomedical sampling, which holds promising potential for disease diagnosis or controlled drug delivery in precision medicine.

Anionically reinforced hydrogel network entrapped fungal cells for retention of cadmium in the contaminated aquatic media

A novel biomass/polymer composite was fabricated by embedding Thamnidium elegans cells in acrylic network of p(3-Methoxyprophyl)acrylamide p(MPA) enriched with 2-Akrylamido-2-methyl-1-propane sulfonic acid (AMPS). Cd(II) retention potential of hydrogel (p(MPA-co-AMPS)) increased by 20.66% times after this enrichment. The gel matrix could be effectively entrapped the biomass and resulting sorbent applied to remove Cd(II) from water in batch and continuous modes. The main physico-chemical parameters are discussed in addition to characterization, regeneration and application studies of the suggested sorbent. Equilibrium occurred within 30 min and Langmuir model predicted the equilibrium data. Kinetics of Cd(II) removal onto immobilized biomass is modeled using the pseudo-second-order rate equation. Maximum monolayer sorption capacity was estimated to be 123.76 mg g^-1 at 25 °C. Designed composite was successfully applied for the removal of Cd(II) from industrial wastewater. EDTA and HNO₃ can be efficiently used for Cd(II) recovery and composite sorbent recycled for at least 12 cycles with nearly stable sorption performance.

Thermally reversible VPBA-NIPAM copolymer gels for nucleotide adsorption

A thermosensitive gel matrix was prepared by free radical copolymerization of N-isopropylacrylamide (NIPAM) with a boronic acid-carrying monomer (i.e. 4-vinylphenylboronic acid, VPBA). The synthesis of the gel was performed at 70 degrees C in an alcohol-water mixture, using azobisisobutyronitrile and methylenebisacrylamide as the initiator and the crosslinker, respectively. To produce thermosensitive gels with a higher diol-binding affinity, an amino-containing comonomer, N-[3-(dimethylamino)propyl]methacrylamide (DMAPM) was included in the gel formation recipe. Thermally reversible VPBA-NIPAM and VPBA-DMAPM-NIPAM gels with different swelling properties were obtained by changing the feed concentrations of VPBA and DMAPM. To test the usability of the produced gels as sorbents in nucleotide adsorption, beta-nicotinamide adenine dinucleotide (beta-NAD) was selected as a model biomolecule. Then the adsorption isotherm for beta-NAD was obtained at +4 degrees C in HEPES buffer medium with a pH of 8.5. The support material was in a highly swollen form under these conditions, due to its thermosensitive character. This property was then used to enhance beta-NAD adsorption onto the gel matrix. Equilibrium adsorption capacities up to 70 mg beta-NAD/g dry gel could be achieved with the thermosensitive support prepared with the 12.9 mol% VPBA feed. The gels produced with higher VPBA and DMAPM feed concentrations exhibited higher equilibrium adsorption capacities for beta-NAD.

Latex particles with thermo-flocculation and magnetic properties for immobilization of alpha-chymotrypsin

Core-shell-type latex particles composed of styrene, N-isopropylacrylamide (NIPAAm), and N-acryloxysuccinimide (NAS) were synthesized by surfactant-free emulsion polymerization. The latex particles show thermo-flocculation behavior due to the presence of temperature-sensitive monomer NIPAAm and could be used for immobilization of alpha-chymotrypsin through covalent bonding with the reactive ester groups of NAS. Enzyme recycle could be accomplished in this immobilized enzyme system by sedimentation of the thermo-flocculated latex particles in 20 min at 30 degrees C by raising the salt (NaCl) concentration to 0.5 M. To further enhance the sedimentation rate, ultrafine magnetite particles were prepared and included during polymerization to produce magnetic temperature-sensitive latex particles (MTLP), which could be recovered 6 times faster after thermo-flocculation by applying a low magnetic field. However, a higher salt concentration was necessary to flocculate the MTLP under the same condition as a result of its increased surface hydrophilicity, which originates from different polymerization conditions and the incorporation of magnetite. The immobilized enzyme shows high activity even against macromolecular substrates (hemoglobin and casein) owing to limited diffusion resistance, with full activity retention for nonmagnetic latex but one-half reduction in activity if the magnetic property was introduced. Optimal enzyme immobilization pH and enzyme loading were determined, and properties of the immobilized enzyme were characterized. The immobilized enzyme was used in 10 repeated batch hydrolyses of casein with successive flocculation/dispersion cycles and showed less than 15% activity decrease at the end. Overall, introducing the magnetic property to the latex could effectively enhance the solid-liquid separation rate after thermo-flocculation and maintain enzyme activity after repeated use but adversely influence the activity of the immobilized enzyme.

DNA adsorption onto polyethylenimine-attached poly(p-chloromethylstyrene) beads

In this study, DNA adsorption properties of polyethylenimine (PEI)-attached poly(p-chloromethylstyrene) (PCMS) beads were investigated. Spherical beads with an average size of 186 microm were obtained by the suspension polymerization of p-chloromethylstyrene conducted in an aqueous dispersion medium. Owing to the reasonably rough character of the bead surface, PCMS beads had a specific surface area of 14.1 m2/g. PEI chains could be covalently attached onto the PCMS beads with equilibrium binding capacities up to 208 mg PEI/g beads, via a direct chemical reaction between the amine and chloromethyl groups. After PEI adsorption with 10% (w/w) initial PEI concentration, free amino content of PEI-attached PCMS beads was determined as 0.91 mequiv./g. PEI-attached PCMS beads were utilized as sorbents in DNA adsorption experiments conducted at +4 degrees C in a phosphate buffer medium of pH 7.4. DNA immobilization capacities up to 290 mg DNA/g beads could be achieved with the tried sorbents. This value was approximately 50-times higher relative to the adsorption capacities of previously examined sorbents.

alpha-Amylase immobilized on bulk acoustic-wave sensor by UV-curing coating

A new method for immobilization of alpha-amylase by UV-curing coating is proposed in this paper. The immobilization procedure of UV-curing coating on piezoelectric quartz crystal is simple and convenient, and causes less loss of enzymatic activity. The activity of the immobilized alpha-amylase is monitored by a technique based on bulk acoustic-wave (BAW) sensor. The frequency shift of BAW sensor can reflect the degree of hydrolysis of starch by the immobilized alpha-amylase. It is appropriate for the immobilized alpha-amylase to hydrolyze the soluble starch under pH 7.0 condition, which is similar to that of the free alpha-amylase. Kinetic parameters (the Michaelis constant, K(m), and the maximum initial rate V(max)) of the enzymatic hydrolysis of starch by the immobilized alpha-amylase are estimated by using a linear method of Lineweaver-Burk plot. K(m)=12.7mgml(-1) and V(max)=15.9Hzmin(-1). And the experimental results show that the immobilized alpha-amylase entrapped by the UV-curing coating retains adequate enzymatic activity and can be reused more than 50 times under certain experimental conditions.

A poly(N-isopropylacrylamide-co-N-acryloxysuccinimide-co-2-hydroxyethyl methacrylate) composite hydrogel membrane for urease immobilization to enhance urea hydrolysis rate by temperature swing*

A composite membrane made of cross-linked poly(N-isopropylacrylamide-co-N-acryloxysuccinimide-co-2-hydroxyethyl methacrylate) (p(NIPAAm-NAS-HEMA)) hydrogel on polyester nonwoven support has been synthesized. The composite membrane shows temperature-responsive properties similar to conventional PNIPAAm hydrogels beads, which reversibly swells below and de-swells above the lower critical solution temperature of PNIPAAm (around 32 to 33 degrees C). Diffusion of urea through the membrane was temperature-dependent with the effective diffusion coefficient at 20 degrees C being 18 times that at 60 degrees C. Urease was immobilized directly to the membrane by forming covalent bonds between its amino groups and the succinimide ester groups of the membrane. Membrane prepared with NIPAAm to NAS molar ratio of 9, and then reacted in pH 7 buffer with 6 mg of urease gave the best immobilized enzyme, where 0.102 mg protein and 5.71 U activity per cm(2) membrane, and 55% relative specific activity could be obtained. There was negligible internal mass transfer resistance for this preparation judging from the calculated effectiveness factor. Urease shows enhanced thermal stability after immobilization with the first-order inactivation rate constant at 70 degrees C decreased to 1/8 of that of free urease. Membrane-immobilized urease could be utilized in a two-compartment membrane reactor with temperature swing to substantially enhance urea hydrolysis rate. The best operating condition of the membrane reactor was with temperature cycling between 60 to 20 degrees C and with temperature change every 10 min, where concentration of product ammonia after 3 h reaction increased 3.8-folds when compared with isothermal operation at 60 degrees C.