Thermodynamic Theory of Multiresponsive Microgel Swelling

Dual-responsive colloidosome-like microgels as the building blocks for phase inversion of Pickering emulsions

The intelligent regulation of microgel-stabilized Pickering emulsions with multi-responsiveness is presently constrained to the processes of emulsification and destabilization. However, the expansion of multi-control over Pickering emulsions to involve phase inversion and the investigation of the accompanying processes and mechanisms present a great challenge. In this study, a microgel with dual responsiveness to both pH and temperature was synthesized using an emulsion template. The resulting microgel exhibited a robust colloidosome-like structure, distinguished by the presence of monolayer-adsorbed silica nanoparticles. The regulation of the packing of surface-covered silica nanoparticles was easily achieved through the swelling of the microgel matrix. Furthermore, the wettability of the microgel can be adjusted between hydrophilic and hydrophobic intervals, allowing for the effective and dual-responsive phase inversion of Pickering emulsions. Moreover, it has been observed that colloidosome-like microgels can lead to unique interfacial structures during the emulsification process, thereby elucidating the fundamental mechanism governing emulsion phase inversion.

A new method for reactive constant pH simulations

We present a simulation method that allows us to calculate the titration curves for systems undergoing protonation/deprotonation reactions-such as charged colloidal suspensions with acidic/basic surface groups, polyelectrolytes, polyampholytes, and proteins. The new approach allows us to simultaneously obtain titration curves both for systems in contact with salt and acid reservoir (semi-grand canonical ensemble) and for isolated suspensions (canonical ensemble). To treat the electrostatic interactions, we present a new method based on Ewald summation-which accounts for the existence of both Bethe and Donnan potentials within the simulation cell. We show that the Donnan potential dramatically affects the pH of a suspension. Counterintuitively, we find that in suspensions with a large volume fraction of nanoparticles and low ionic strength, the number of deprotonated groups can be 100% larger in an isolated system, compared to a system connected to a reservoir by a semi-permeable membrane-both systems being at exactly the same pH.

Recent advances in cellulose microgels: Preparations and functionalized applications

Microgels are soft, deformable, permeable, and stimuli-responsive microscopic polymeric particles that are now emerging as prospective multifunctional soft materials for delivery systems, interface stabilization, cell cultures and tissue engineering. Cellulose microgels are emerging biopolymeric microgels with unique characteristics such as abound hydroxyl structure, admirable designability, multiscale pore network and excellent biocompatibility. This review summarizes the fabrication strategies for microgel, then highlights the fabrication routes for cellulose microgels, and finally elaborates cellulose microgels' bright application prospects with unique characteristics in the fields of controlled release, interface stabilization, coating, purification, nutrition/drug delivery, and bio-fabrication. The challenges to be addressed for further applications and considerable scope for development in future of cellulose microgels are also discussed.

Role of molecularly imprinted hydrogels in drug delivery - A current perspective

Molecular imprinting in hydrogels crafts memory for template molecules in a flexible macromolecular structure. Molecular imprinting can control the pattern of the drug release via different mechanistic pathways which may involve swelling, which releases the drug via diffusion or receptive-swollen networks. Responsive hydrogels or smart hydrogels can be tailored to undergo a change in the network structure in response to a stimulus by inserting specific chemical or biological entities along their backbone polymer chains. The stimuli which can be either physical, chemical or biochemical in nature, may impact at various energy levels thereby initiating the molecular interactions at critical onset points. Conventional hydrogels lack in responding to an external stimuli in a swift manner, hence the molecular imprinting technology can significantly advance the therapeutic efficiency of the drugs with anticipated controlled release and targeting efficiency. Molecular imprinting in hydrogels is thus anticipated as a step towards establishment of drug delivery systems by providing improved delivery profiles or longer release times and deliver the drugs in a feedback regulated way. The review article focuses on the current scenario of molecularly imprinted hydrogels with emphasis on the imprinting strategies within hydrogels and challenges encountered, latent translational applications, and future perspectives.

How molecular interactions tune the characteristic time of nanocomposite colloidal sensors

HYPOTHESIS

Mass transport critically controls the performance of colloidal metal-polymer sensors. We hypothesize that molecular-level pair interactions, such as electric, steric, and specific binding effects, govern the mass transport and, in return, the characteristic time of these sensors.

THEORY

Here we present a simple theory guided by experimental data to examine the sensing performance of two usually encountered archetypal metal-polymer sensors, namely (1) core-shell and (2) yolk-shell architectures. For this purpose, we use the static reactive density functional theory framework, determining how (i) charge, (ii) size, and (iii) non-covalent binding factors modulate the characteristic time.

FINDINGS

We show how an interplay between diffusivity and partitioning governs the sensing time of the sensors, where an anti-correlation cancellation between them renders the time non-trivial. Our study demonstrates that the convoluted substrate-hydrogel shell interaction controls the characteristic time of these colloidal sensors, especially when the sensors are in a collapsed state. Notably, the substrates with a high dipole moment tend to equilibrate greatly, but undesirably, at the shell-solution interface. With this, we encourage the formation of a metastable sorption state.

Triply-responsive OEG-based microgels and hydrogels: regulation of swelling ratio, volume phase transition temperatures and mechanical properties

Facile methods to coordinate swelling ratio, volume-phase transition temperatures and mechanical properties for pH-, thermal-, and cationic-responsive microgels and hydrogels.