Thermoresponsive Gold Polymer Nanohybrids with a Tunable Cross‐Linked MEO₂MA Polymer Shell

Abstract

Gold nanoparticles (AuNPs) are functionalized with a thermoresponsive polymer shell of a cross‐linked poly(2‐(2‐methoxyethoxy)ethyl methacrylate) (P(MEO2MA)). To provide a covalent attachment of the polymer to the NP surface, AuNPs are first modified using butanoic acid to develop the encapsulation with the biocompatible thermoresponsive polymer formed by free‐radical precipitation polymerization. Both the MEO2MA concentration and the shell cross‐linking density can be varied and, in turn, the thickness and the shells' free volume can be fine‐tuned. By downscaling the size of the polymeric shell, the lower critical solution temperature (LCST) is decreased. The LCST in the nanohybrids changes from 19.1 to 25.6 °C when increasing the MEO2MA content; it reaches almost 26 °C for P(MEO2MA) (bulk). The maximum decrease in the volume of the nanohybrids is around 40%, resulting in a modification of the light scattering properties of the system and causing a change in the turbidity of the gel network. The sizes of the nanohybrids are characterized using both transmission electron microscopy and dynamic light scattering measurements. Optical properties of the colloidal systems are determined using the derived count rate measurements as an alternative to absorbance or transmittance measurements, confirming the colloidal stability of the nanohybrid systems.

Synthesis of a thermoresponsive crosslinked MEO2MA polymer coating on microclusters of iron oxide nanoparticles

“…Smart polymers can be chosen to exhibit stimuli-responsive properties whereby their structure is strongly affected by the external conditions ( e.g . light, temperature, pH, concentration of chemicals, pressure or electronic fields) 1 – 5 . Among them, thermoresponsive polymers have gained a great deal of attention since the phase transition between hydrophilic and hydrophobic states involves a considerable change in volume when reaching a lower critical solution temperature (LCST) 6 – 10 .…”

Review on synthesis, properties, characterization, and applications of responsive microgels fabricated with gold nanostructures

“…Contreras-Cáceres et al (2009) have reported that, if Au and BIS content are kept constant, then the VPTT of Au-p(NIPAM) hybrid microgels increases from 36°C to 42°C by decreasing the feed content of NIPAM from 100% to 40%. Lapresta-Fernández et al (2014) have observed that the VPTT of hybrid microgels decreases by increasing the content of cross-linker tetraethylene glycol dimethacrylate. According to the best of our knowledge, the modulation of the VPTT of negative thermoresponsive Au-microgels by varying the content of Au nanostructures has not been reported in the literature yet.…”

Dynamism of Stimuli-Responsive Nanohybrids: Environmental Implications

“…” This principle includes ANHs composed of metallic, carbonaceous or polymeric NMs and NHs functionalized with stimuli-responsive coronas or polymers [ 47 , 48 , 49 , 50 ] ( Figure 1 a) and NMs suspended or loaded with linear and branched stimuli-responsive co-polymers or cross-linked polymer networks [ 35 , 51 , 52 ] ( Figure 1 b). ANHs in which stimuli-responsive coatings are covalently bonded to drug molecules [ 53 ] or to metallic NMs with tunable properties [ 25 ] ( Figure 1 c) and polymer brushes grafted [ 54 ] or strongly bonded via sulfur bonds [ 47 ] can also be included.…”

“…The thermo-responsive coating undergoes a phase transition from a hydrophilic water-swollen state to a hydrophobic globular state, when heated above its LCST. Such changes result in modification of the light scattering properties of the nano-system and cause a change in the turbidity of the gel network of PMEO2MA [ 25 ]. Different degrees of swelling at high and low temperatures influence the range of applications of core-shell ANHs.…”

“…Today’s drugs are not only required to optimize targeted delivery, but are also designed to manifest superior control over their release [ 22 ]. A complex combination of multiple soft organic blocks allows for achieving such molecular-level control in response to an environmental stimulus, e.g., pH [ 12 ], ionic strength [ 23 ], solvent polarity [ 24 ], heat [ 25 ], magnetic [ 26 ] or electric field [ 27 ], light [ 28 ] and sound [ 29 ], and enable their applications in targeted drug delivery, development of artificial muscles and sensing materials, robotics and molecular electronics [ 30 , 31 ]. Next generation molecular electronics and bio-engineered applications are more encouraged to employ such stimuli-responsive ANHs and, thus, necessitate careful assessment of their potential environmental and toxicological consequences.…”