On Going to a New Era of Microgel Exhibiting Volume Phase Transition

Compartmentalized Polyampholyte Microgels by Depletion Flocculation and Coacervation of Nanogels in Emulsion Droplets

In pH-responsive drug carriers, the distribution of charges has been proven to affect delivery efficiency but is difficult to control and verify. Herein, we fabricate polyampholyte nanogel-in-microgel colloids (NiM-C) and show that the arrangement of the nanogels (NG) can easily be manipulated by adapting synthesis conditions. Positively and negatively charged pH-responsive NG are synthesized by precipitation polymerization and labelled with different fluorescent dyes. The obtained NG are integrated into microgel (MG) networks by subsequent inverse emulsion polymerization in droplet-based microfluidics. By confocal laser scanning microscopy (CLSM), we verify that depending on NG concentration, pH value and ionic strength, NiM-C with different NG arrangements are obtained, including Janus-like phase-separation of NG, statistical distribution of NG, and core-shell arrangements. Our approach is a major step towards uptake and release of oppositely charged (drug) molecules.

Composite Nanoarchitectonics of Photoactivated Titania-Based Materials with Anticancer Properties

The synthesis of titania-based composite materials with anticancer potential under visible-light irradiation is the aim of this study. In specific, titanium dioxide (TiO₂) nanoparticles (NPs) chemically modified with silver were embedded in a stimuli-responsive microgel (a crosslinked interpenetrating network (IP) network that was synthesized by poly (N-Isopropylacrylamide) and linear chains of polyacrylic acid sodium salt, forming composite particles. The ultimate goal of this research, and for our future plans, is to develop a drug-delivery system that uses optical fibers that could efficiently photoactivate NPs, targeting cancer cells. The produced Ag-TiO₂ NPs, the microgel and the composite materials were characterized through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), micro-Raman spectroscopy, ultraviolet-visible spectroscopy (UV-Vis), dynamic light scattering (DLS) and transmission electron microscopy (TEM). Our results indicated that Ag-TiO₂ NPs were successfully embedded within the thermoresponsive microgel. Either Ag-TiO₂ NPs or the composite materials exhibited high photocatalytic degradation efficiency on the pollutant rhodamine B and significant anticancer potential under visible-light irradiation.

Preparation and Characterization of Thermoresponsive Poly(N-vinylisobutyramide) Microgels

Microgels are soft, adaptive materials exhibiting various properties not only like hydrogels and microparticles but also like macromolecules, colloids, and surfactants. To widen the range of their biomedical and environmental applications, the exploration of an alternative for poly(N-alkylacrylamide)s without potential safety risks is of great importance. In this article, thermoresponsive poly(N-vinylisobutyramide) (PNVIBA) microgels of uniform size were synthesized with NVIBA as a monomer and N,N'-5-oxanonamethyene-bis-N-vinylacetamide as a cross-linker in the presence of sodium dodecyl sulfate by aqueous free radical precipitation polymerization. The introduction of cationic groups into PNVIBA microgels was also accomplished using N-vinylformamide (NVF) as a comonomer and the subsequent conversion of NVF into vinylamine by hydrolysis.

Two-dimensional colloidal crystal of soft microgel spheres: Development, preparation and applications

Two-dimensional (2D) colloidal crystals are ordered monolayer arrays of colloidal sphere particles assembled on the substrates or at phase interfaces. Owing to their unique periodic structure and fascinating properties, 2D colloidal crystals have aroused considerable interest because of their potential applications. Among them, 2D colloidal crystals self-assembled from soft microgel spheres stand out particularly. The 2D colloidal crystals of soft microgel spheres combine the advantages of monolayer colloidal crystals and sensitive microgels, which have a good application prospect in biomedical area. In this article, we provide a systematic overview of 2D colloidal crystals of soft microgel spheres related to their development, preparation and applications. First, various preparation methods of 2D colloidal crystal of microgels are introduced, including dip-coating, drop-coating, spin-coating, interface assembly, surface reaction-assisted assembly, and so forth. Second, representative biomedical applications consisting of optical sensor, drug delivery, antibacterial coating, cell culture, and colloidal template are also exemplified to show the high performance of 2D colloidal crystals of soft microgel spheres. In addition, we also present prospects of future developments of 2D microgel colloidal crystals.

Thermoresponsive Chitosan-Grafted-Poly(N-vinylcaprolactam) Microgels via Ionotropic Gelation for Oncological Applications

Microgels can be considered soft, porous and deformable particles with an internal gel structure swollen by a solvent and an average size between 100 and 1000 nm. Due to their biocompatibility, colloidal stability, their unique dynamicity and the permeability of their architecture, they are emerging as important candidates for drug delivery systems, sensing and biocatalysis. In clinical applications, the research on responsive microgels is aimed at the development of "smart" delivery systems that undergo a critical change in conformation and size in reaction to a change in environmental conditions (temperature, magnetic fields, pH, concentration gradient). Recent achievements in biodegradable polymer fabrication have resulted in new appealing strategies, including the combination of synthetic and natural-origin polymers with inorganic nanoparticles, as well as the possibility of controlling drug release remotely. In this review, we provide a literature review on the use of dual and multi-responsive chitosan-grafted-poly-(N-vinylcaprolactam) (CP) microgels in drug delivery and oncological applications.

Understanding Thermal Behavior of Poly(ethylene glycol)-block-poly(N-isopropylacrylamide) Hydrogel Using Two-Dimensional Correlation Infrared Spectroscopy

In this study, one of the thermoresponsive polymers, block copolymer consisting of poly(ethylene glycol) and poly(N-isopropylacylamide), was investigated using Fourier transform infrared (FT-IR) spectroscopy, principal component analysis (PCA), and two-dimensional correlation spectroscopy (2D-COS). The apparent trend of the spectral changes in the temperature-dependent FT-IR spectra of poly(ethylene glycol)-block-poly(N-isopropylacylamide) (PEG-b-PNiPAAm) hydrogel during the heating process looks similar to that during the cooling process. The results of the PCA and 2D-COS, however, clearly indicate an irreversible phase transition mechanism of PEG-b-PNiPAAm hydrogel during the heating and cooling processes. It has been also shown that PEG affects the phase transition mechanism of PEG-b-PNiPAAm hydrogel, especially during the heating process. Consequently, we can successfully determine the phase transition temperature and the mechanism of PEG-b-PNiPAAm hydrogel during the heating and cooling processes using PCA and 2D-COS, respectively.

Nutritional targeting modification of silkworm pupae oil catalyzed by a smart hydrogel immobilized lipase

To prepare a nutritional supplement using silkworm pupae oil (SPO) as a feedstock, a microfluidic reactor with a smart hydrogel immobilized lipase was first constructed to reduce the relative content of palmitic acid at sn-1,3 and improve the nutritional function. The effects of flow rate, reaction temperature, and substrate molar ratio were investigated. In vitro digestion and pH-stat models were employed to analyze the digestion feature after the modification of SPO, while HPLC-ELSD, zeta potential, DSC, and TGA were used to evaluate the nutritional function. The relative content of "OOO" and "OPO" type triglycerides was increased by 49.48% and 107.67%, and that of palmitic acid at sn-1,3 was decreased by 49.61% in 10 s. After the verification of the in vitro digestion model, the fatty acid release rate of the modified SPO was significantly improved by 22.07%, indicating the nutritional function improvement of SPO. Therefore, the nutritional function of SPO has been improved successfully by the application of a microchannel reactor with photo-immobilized lipase, which could set a reference for the utilization of insect oil resources.