Switching enzyme activity by a temperature responsive inhibitor modified polymer

A thermoresponsive NIPAAm-based polymer is combined with the selective acetylcholinesterase inhibitor tacrine in order to create a strict in sense on/off switch for enzyme activity.

General method for the production of hydrogel droplets from uniformly sized smart shell membranes

A smart solid-state liquid crystal shell membrane template prepared by a microfluidic method with a reactive mesogen mixture doped with a nematic liquid crystal of 5CB as a porogen was used for a facile and general method to produce uniformly sized hydrogel droplets.

Applications of Highly Stretchable and Tough Hydrogels

Stretchable and tough hydrogels have drawn a lot of attention recently. Due to their unique properties, they have great potential in the application in areas such as mechanical sensing, wound healing, and drug delivery. In this review, we will summarize recent developments of stretchable and tough hydrogels in these areas.

Mechanoresponsive and recyclable biocatalytic sponges from enzyme-polymer surfactant conjugates and nanoparticles

The fabrication of biocatalytic, porous, recyclable, and mechanoresponsive elastic sponge like material is shown from a mixture of core–shell alkaline phosphatase-polymer surfactant bioconjugates and nanoparticles.

Acetyl-CoA production by encapsulated pyruvate ferredoxin oxidoreductase in alginate hydrogels

Pyruvate ferredoxin oxidoreductase from Citrobacter sp. S-77 (PFOR_S77) was purified in order to develop a method for acetyl-CoA production. Although the purified PFOR_S77 showed high O₂-sensitivity, the activity could be remarkably stabilized in anaerobic conditions. PFOR_S77 was effectively immobilized on ceramic hydroxyapatite (PFOR_S77-HA) with an efficiency of more than 96%, however, after encapsulation of PFOR_S77-HA in alginate, the rate of catalytic acetyl-CoA production was highly reduced to 36% when compared to that of the free enzyme. However, the operational stability of the PFOR_S77-HA in alginate hydrogels was remarkable, retaining over 68% initial activity even after ten repeated cycles. The results suggested that the PFOR_S77-HA hydrogels have a high potential for biotechnological application.

Mechanoresponsive materials for drug delivery: Harnessing forces for controlled release

Mechanically-activated delivery systems harness existing physiological and/or externally-applied forces to provide spatiotemporal control over the release of active agents. Current strategies to deliver therapeutic proteins and drugs use three types of mechanical stimuli: compression, tension, and shear. Based on the intended application, each stimulus requires specific material selection, in terms of substrate composition and size (e.g., macrostructured materials and nanomaterials), for optimal in vitro and in vivo performance. For example, compressive systems typically utilize hydrogels or elastomeric substrates that respond to and withstand cyclic compressive loading, whereas, tension-responsive systems use composites to compartmentalize payloads. Finally, shear-activated systems are based on nanoassemblies or microaggregates that respond to physiological or externally-applied shear stresses. In order to provide a comprehensive assessment of current research on mechanoresponsive drug delivery, the mechanical stimuli intrinsically present in the human body are first discussed, along with the mechanical forces typically applied during medical device interventions, followed by in-depth descriptions of compression, tension, and shear-mediated drug delivery devices. We conclude by summarizing the progress of current research aimed at integrating mechanoresponsive elements within these devices, identifying additional clinical opportunities for mechanically-activated systems, and discussing future prospects.

A bulk sub-femtoliter in vitro compartmentalization system using super-fine electrosprays

The extreme miniaturization of biological and chemical assays in aqueous-droplet compartments enables spatiotemporal control for large-scale parallel experimentation and can thus permit new capabilities for "digitizing" directed molecular evolution methodologies. We report a remarkably facile bulk method to generate mega-scale monodisperse sub-femtoliter aqueous droplets by electrospray, using a prototype head with super-fine inkjet technology. Moreover, the electrostatic inkjet nozzle that injects the aqueous phase when immersed within an immiscible phase (an optimized oil/surfactant mixture) has the advantage of generating cell-like sub-femtoliter compartments for biomolecule encapsulation and successive biological and chemical reactions. Sub-femtoliter droplets of both liquid (water-in-oil, volumes ranging from 0.2 to 6.4 fL) and gel bead (agarose-in-oil, volume ranging from 0.3 to 15.6 fL) compartments with average sizes of 1.3 μm and 1.5 μm, respectively, were successfully generated using an inkjet nozzle at a speed of more than 10(5) droplets per second. We demonstrated the applicability of this system by synthesizing fluorescent proteins using a cell-free expression system inside electrosprayed sub-femtoliter droplets at an accelerated rate, thereby extending the utility of in vitro compartmentalization with improved analytical performance for a top-down artificial cellular system.

Stretch-Induced Drug Delivery from Superhydrophobic Polymer Composites: Use of Crack Propagation Failure Modes for Controlling Release Rates

The concept of using crack propagation in polymeric materials to control drug release and its first demonstration are reported. The composite drug delivery system consists of highly-textured superhydrophobic electrosprayed microparticle coatings, composed of biodegradable and biocompatible polymers poly(caprolactone) and poly(glycerol monostearate carbonate-co-caprolactone), and a cellulose/polyester core. The release of entrapped agents is controlled by the magnitude of applied strain, resulting in a graded response from water infiltration through the propagating patterned cracks in the coating. Strain-dependent delivery of the anticancer agents cisplatin and 7-ethyl-10-hydroxycamptothecin to esophageal cancer cells (OE33) in vitro is observed. Finally the device is integrated with an esophageal stent to demonstrate delivery of fluorescein diacetate, using applied tension, to an ex vivo esophagus.

Synthesis of a glucose oxidase-conjugated, polyacrylamide-based, fluorescent hydrogel for a reusable, ratiometric glucose sensor

New emission color-changeable hydrogels containing glucose oxidase were synthesized to be used in glucose sensing.

Reversible pH-controlled switching of an artificial antioxidant selenoenzyme based on pseudorotaxane formation and dissociation

A conceptual smart GPx model that showed a response to pH stimuli was developed by using a simple selenium-containing compound and a cucurbit[6]uril-pseudorotaxane-based molecular switch.

Fundamentals of double network hydrogels

Double network (DN) hydrogels as promising soft-and-tough materials intrinsically possess extraordinary mechanical strength and toughness due to their unique contrasting network structures, strong interpenetrating network entanglement, and efficient energy dissipation.