Smart shape-controlled synthesis of poly(N-isopropylacrylamide)/chitosan/Fe3O4 microgels

Microgels in biomaterials and nanomedicines

Microgels are colloidal particles with crosslinked polymer networks and dimensions ranging from tens of nanometers to micrometers. Specifically, smart microgels are fascinating capable of responding to biological signals in vivo or remote triggers and making the possible for applications in biomaterials and biomedicines. Therefore, how to fundamentally design microgels is an urgent problem to be solved. In this review, we put forward our important fundamental opinions on how to devise the intelligent microgels for cancer therapy, biosensing and biological lubrication. We focus on the design ideas instead of specific implementation process by employing reverse synthesis analysis to programme the microgels at the original stage. Moreover, special insights will be, for the first time, as far as we know, dedicated to the particles completely composed of DNA or proteins into microgel systems. These are discussed in detail in this review. We expect to give readers a broad overview of the design criteria and practical methodologies of microgels according to the application fields, as well as to propel the further developments of highly interesting concepts and materials.

Investigation of magnetic silica with thermoresponsive chitosan coating for drug controlled release and magnetic hyperthermia application

In this study, a drug delivery system for chemo-hyperthermia applications is proposed and fabricated. The delivery system consists of magnetic-silica (MagSi) particles being encapsulated within a pH/thermo-responsive chitosan‑g‑N‑isopropylacrylamide (Chi-g-NIPAAm) polymer matrix. The as-prepared MagSi@Chi-g-NIPAAm particles exhibit superparamagnetic behavior with a saturation magnetization (Ms) of 20.14 emu/g. In addition, the MagSi@Chi-g-NIPAAm particles can act as a heat source when subject to an alternating magnetic field (AMF) and have a specific absorptions rate (SAR) of 8.36 Wg^-1. The release of the drug DOX from the synthesized particles is sensitive to both the pH and temperature of its environment. We have compared the drug release when the solution is externally heated up and when it is heated up by the AMF (internal heating). For external heating (when the pH/temperature is 4.0/45 °C), 83.30 ± 2.92% of the DOX were released within the first 5 h. The release of the DOX by the particles in pH 7.4 (temperature of 37 °C) was much slower (around 25.87 ± 1.30% after 25 h). The release of the DOX was much higher (under an acidic condition pH = 4.0) around 57.13 ± 2.36% within 1 h in the presence of AMF heating. The in vitro cytotoxicity tests of the of DOX-loaded MagSi@Chi-g-NIPAAm particles towards HeLa cancer cells. In general, the toxicities of the drug DOX as part of a MagSi@Chi-g-NIPAAm particles were less than those of the standalone DOX until the concentration of DOX-loaded particles reached 250 μg/mL, after which the toxicity of DOX in both forms were the same.

Temperature-Sensitive Poly(N-isopropylacrylamide)/Konjac Glucomannan/Graphene Oxide Composite Membranes with Improved Mechanical Property, Swelling Capability, and Degradability

Temperature-sensitive poly(N-isopropylacrylamide)/konjac glucomannan/graphene oxide (PNIPAM/KGM/GO) composite membranes were prepared by solution blending using calcium ions as a cross-linker. The composite membranes were characterized by Fourier-transform infrared spectroscopy (FT-IR), field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Raman spectroscopy (Raman), and differential scanning calorimetry (DSC). The swelling, mechanical property, phase transformation behaviors, and enzymatic degradation activities were also determined. Results revealed that the phase transition temperatures of all the composite membranes were approximately 35°C. The PNIPAM/KGM/GO composite membranes showed enhanced mechanical property. The swelling behavior and enzymatic degradation of the PNIPAM/KGM/GO composite membranes improved compared with those of conventional PNIPAM hydrogel and PNIPAM/KGM composite membranes. Thus, the PNIPAM/KGM/GO composite membranes have potential applications in the biomedical field as skin dressings.

Dynamically Cross-Linked Self-Assembled Thermoresponsive Microgels with Homogeneous Internal Structures

The internal morphology of temperature-responsive degradable poly(N-isopropylacrylamide) (PNIPAM) microgels formed via an aqueous self-assembly process based on hydrazide and aldehyde-functionalized PNIPAM oligomers is investigated. A combination of surface force measurements, small angle neutron scattering (SANS), and ultrasmall angle neutron scattering (USANS) was used to demonstrate that the self-assembled microgels have a homogeneously cross-linked internal structure. This result is surprising given the sequential addition process used to fabricate the microgels, which was expected to result in a densely cross-linked shell-diffuse core structure. The homogeneous internal structure identified is also significantly different than conventional microgels prepared via precipitation polymerization, which typically exhibit a diffuse shell-dense core structure. The homogeneous structure is hypothesized to result from the dynamic nature of the hydrazone cross-linking chemistry used to couple with the assembly conditions chosen that promote polymer interdiffusion. The lack of an internal cross-linking gradient within these degradable and monodisperse microgels is expected to facilitate more consistent drug release over time, improved optical properties, and other potential application benefits.

Thermoresponsive Semi-IPN Hydrogel Microfibers from Continuous Fluidic Processing with High Elasticity and Fast Actuation

Hydrogels with rapid and strong response to external stimuli and possessing high elasticity and strength have been considered as platform materials for numerous applications, e.g., in biomaterials engineering. Thermoresponsive hydrogels based on semi-interpenetrating polymer networks (semi-IPN) featuring N-isopropylacrylamide with copolymers of poly(N-isopropylacrylamide-co-hydroxyethyl methacrylate) p(NIPAM-HEMA) chains are prepared and described. The copolymer was characterized by FTIR, NMR, and GPC. The semi-IPN structured hydrogel and its responsive properties were evaluated by dynamic mechanical measurements, SEM, DSC, equilibrium swelling ratio, and dynamic deswelling tests. The results illustrate that the semi-IPN structured hydrogels possess rapid response and high elasticity compared to conventional pNIPAM hydrogels. By using a microfluidic device with double coaxial laminar flow, we succeeded in fabricating temperature responsive ("smart") hydrogel microfibers with core-shell structures that exhibit typical diameters on the order of 100 μm. The diameter of the fibers can be tuned by changing the flow conditions. Such hydrogel fibers can be used to fabricate "smart" devices, and the core layer can be potentially loaded with cargos to incorporate biological function in the constructs. The platforms obtained by this approach hold promise as artificial "muscles", and also "smart" hydrogel carriers providing a unique biophysical and bioactive environment for regenerative medicine and tissue engineering.

Synthesis, characterization and application of a MnFe2O4@poly(o-toluidine) nanocomposite for magnetic solid-phase extraction of polycyclic aromatic hydrocarbons

A nanocomposite of poly(o-toluidine)-coated MnFe₂O₄ magnetic nanoparticles with a core–shell structure was synthesized by the chemical co-precipitation method and employed as a magnetic adsorbent for solid-phase extraction of ten polycyclic aromatic hydrocarbons (PAHs).

Investigation on a smart nanocarrier with a mesoporous magnetic core and thermo-responsive shell for co-delivery of doxorubicin and curcumin: a new approach towards combination therapy of cancer

A novel and smart MIO-P(NIPAM-MAm) nanocomposite has been prepared for combinational delivery of Dox and Cur for cancer treatment.

Shaped stimuli-responsive hydrogel particles: syntheses, properties and biological responses

This review summarizes a pool of current experimental approaches and discusses perspectives in the development of the synergistic combination of shape and stimuli-response in particulate hydrogels.

Aptamer-functionalized DNA microgels: a strategy towards selective anticancer therapeutic systems

DNA microgels of oligonucleotides and polymers were constructed via a combination of DNA complementarity and photo-initiated free radical polymerization.