The structure and volume phase transition behavior of poly(N-vinylcaprolactam)-based hybrid microgels containing carbon nanodots

Physicochemical aspects of inorganic nanoparticles stabilized in N-vinyl caprolactam based microgels for various applications

The vinyl caprolactam (VCL) based microgel system has become the center of great attention due to its versatile properties. Copolymerization of VCL with an ionic monomer imparts pH responsive properties into the microgel system in addition to thermo-sensitivity. Stimuli responsive behavior of VCL-based microgels makes them prospective and appealing candidates for practical applications covering the fields of drug delivery, catalysis and optical devices. In the last few years, VCL-based microgels have been used as microreactors and stabilizers for the synthesis and stabilization of inorganic nanoparticles to obtain hybrid microgels. The present review article provides a summary of the present-day progress of fabrication, stabilization, categorization and analysis of VCL-based microgels and their hybrids with different morphologies. The stimuli responsive properties and applications of VCL-based hybrid microgels have been reviewed critically. The remaining problems which need to be addressed have been pointed out for further advancement in this field.

MicroGelzymes: pH-Independent Immobilization of Cytochrome P450 BM3 in Microgels

Microgels are an emerging class of "ideal" enzyme carriers because of their chemical and process stability, biocompatibility, and high enzyme loading capability. In this work, we synthesized a new type of permanently positively charged poly(N-vinylcaprolactam) (PVCL) microgel with 1-vinyl-3-methylimidazolium (quaternization of nitrogen by methylation of N-vinylimidazole moieties) as a comonomer (PVCL/VimQ) through precipitation polymerization. The PVCL/VimQ microgels were characterized with respect to their size, charge, swelling degree, and temperature responsiveness in aqueous solutions. P450 monooxygenases are usually challenging to immobilize, and often, high activity losses occur after the immobilization (in the case of P450 BM3 from Bacillus megaterium up to 100% loss of activity). The electrostatic immobilization of P450 BM3 in permanently positively charged PVCL/VimQ microgels was achieved without the loss of catalytic activity at the pH optimum of P450 BM3 (pH 8; ∼9.4 nmol 7-hydroxy-3-carboxy coumarin ethyl ester/min for free and immobilized P450 BM3); the resulting P450-microgel systems were termed P450 MicroGelzymes (P450 μ-Gelzymes). In addition, P450 μ-Gelzymes offer the possibility of reversible ionic strength-triggered release and re-entrapment of the biocatalyst in processes (e.g., for catalyst reuse). Finally, a characterization of the potential of P450 μ-Gelzymes to provide resistance against cosolvents (acetonitrile, dimethyl sulfoxide, and 2-propanol) was performed to evaluate the biocatalytic application potential.

Hydrogen bonding reinforcement as a strategy to improve upper critical solution temperature of poly(N-acryloylglycinamide-co-methacrylic acid)

HB-type copolymers with suitably tunable UCST and corresponding core–shell nanogels showing UCST–LCST type behavior.

A molecular level study of the phase transition process of hydrogen-bonding UCST polymers

A molecular level study of the UCST-type transition process of PNAGA-based polymers in water and a water/methanol mixture.

Exploration of the unusual two-step volume phase transition of the poly(N-vinylcaprolactam-co-hydroxyethyl methacrylate) hydrogel

It is important to investigate the phase transition mechanism of stimuli-sensitive hydrogels due to its great guiding significance for the application of stimuli-sensitive hydrogels in biomedical applications.

Luminescent supramolecular hydrogels from a tripeptide and nitrogen-doped carbon nanodots

The combination of different components such as carbon nanostructures and organic gelators into composite nanostructured hydrogels is attracting wide interest for a variety of applications, including sensing and biomaterials. In particular, both supramolecular hydrogels that are formed from unprotected D,L-tripeptides bearing the Phe-Phe motif and nitrogen-doped carbon nanodots (NCNDs) are promising materials for biological use. In this work, they were combined to obtain luminescent, supramolecular hydrogels at physiological conditions. The self-assembly of a tripeptide upon application of a pH trigger was studied in the presence of NCNDs to evaluate effects at the supramolecular level. Luminescent hydrogels were obtained whereby NCND addition allowed the rheological properties to be fine-tuned and led to an overall more homogeneous system composed of thinner fibrils with narrower diameter distribution.

Revealing the distinct thermal transition behavior between PEGA-based linear polymers and their disulfide cross-linked nanogels

Description of the distinct thermal transition behavior between PEGA-based linear polymers and their disulfide cross-linked nanogels at a molecular level.

Two-step volume phase transition mechanism of poly(N-vinylcaprolactam) hydrogel online-tracked by two-dimensional correlation spectroscopy

The volume phase transition of PVCL hydrogel was online-tracked by 2D correlation FTIR spectroscopy, and a two-step mechanism was proposed.