Hydrophobic superparamagnetic FePt nanoparticles in hydrophilic poly(N-vinylcaprolactam) microgels: a new multifunctional hybrid system

Abstract

We report the synthesis of a new multifunctional colloidal hybrid system consisting of thermoresponsive amphiphilic biocompatible poly(N-vinylcaprolactam) microgels loaded with hydrophobic superparamagnetic FePt nanoparticles (NPs). In a first step water swellable poly(N-vinylcaprolactam) microgels were mixed with hydrophobicly coated sub-10 nm, superparamagnetic FePt NPs in a tetrahydrofurane (THF) solution. In a second step, changing the surrounding solvent from THF to water forces the FePt NPs to migrate into the amphiphilic microgels. The new hybrid colloids (i) are colloidally stable in water and the thermo-responsive properties in terms of a volume phase transition is retained, (ii) exhibit superparamagnetic characteristics introduced by FePt NPs, (iii) show a drastically reduced cytotoxicity compared to water soluble FePt NP of similar size, as known from literature. This makes the new hybrid microgels suited e.g. as biocompatible containers for drug delivery or for imaging.

Dual Responsive Poly(N-vinylcaprolactam) Based Degradable Microgels for Drug Delivery

“…Hydrodynamic diameter of PVCL‐hdz‐IA‐5 microgels decreases from 310 nm at 20 °C to 140 nm at 54 °C due to the changes in hydrophilic/hydrophobic balance. As reported in the literature, it is to be noted that the phase transition in such particles occur as a result of destruction of hydrogen bonds and increasing hydrophobic aggregation of the polymer . On the other hand, PVCL‐hdz‐IADME‐5 microgels show aggregation which could be due to increased hydrophobic interactions and the reduction in the mobility of available hydrophilic chains responsible for the steric stabilization.…”

“…PVCL‐based microgels are thermosensitive with a reversible transition taking place at 33 °C. This volume‐phase transition temperature (VPTT), above which the microgel particles collapse, depends on the solvent–polymer (hydrophilic) interactions and polymer–polymer (hydrophobic) interactions . Figure b presents the variation of hydrodynamic diameter of various PVCL‐hdz‐IA microgels as a function of temperature at pH 6.5.…”

Nanomechanics and Nanorheology of Microgels at Interfaces

“…The AuNP can act in two directions: (1) Changing the optical properties of the microgels and (2) serving as hotspots which can let shrink locally the PNIPAM matrix. In addition, magnetic nanoparticles (MNP) can be added to microgels [26,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89].…”

Monitoring Microgel Synthesis by Copolymerization of N‐isopropylacrylamide and N‐vinylcaprolactam via In‐Line Raman Spectroscopy and Indirect Hard Modeling

“…Such copolymer microgels can exhibit more than one VPTT and can be functionalized for two‐step responses . Recent applications of such functionalized microgels include actuating applications such as fiber contraction, membrane modification, surface coating, delivery systems, imaging, as well as targeted protein therapy …”