Adhesion and Mechanical Properties of PNIPAM Microgel Films and Their Potential Use as Switchable Cell Culture Substrates

Abstract

Thermoresponsive poly(N‐isopropylacrylamide) (PNIPAM) microgel films are shown to allow controlled detachment of adsorbed cells via temperature stimuli. Cell response occurs on the timescale of several minutes, is reversible, and allows for harvesting of cells in a mild fashion. The fact that microgels are attached non‐covalently allows using them on a broad variety of (charged) surfaces and is a major advantage as compared to approaches relying on covalent attachment of active films. In the following, the microgels’ physico‐chemical parameters in the adsorbed state and their changes upon temperature variation are studied in order to gain a deeper understanding of the involved phenomena. By means of atomic force microscopy (AFM), the water content, mechanical properties, and adhesion forces of the microgel films are studied as a function of temperature. The analysis shows that these properties change drastically when crossing the critical temperature of the polymer film, which is the basis of the fast cell response upon temperature changes. Furthermore, nanoscale mechanical analysis shows that the films posses a nanoscopic gradient in mechanical properties.

Patchiness of Embedded Particles and Film Stiffness Control Through Concentration of Gold Nanoparticles

“…Patchy microparticles with variable coatings and precise control over patch size could be obtained by this approach. Film stiffness-a condition considered to be crucial for cellular responses [40][41][42] -and thereby patch size were controlled by AuNP deposition onto these films. Since films are flipped over during weakening of film-particle interaction, aggregation could be avoided during patchy microparticle liberation.…”

Isostructural solid–solid phase transition in monolayers of soft core–shell particles at fluid interfaces: structure and mechanics

“…They also attract particular interest as stabilizers for inorganic nanoparticles allowing the fabrication of responsive hybrid materials 18 , and have been used as substrates for cell culture 19,20 , for the fabrication of micro-lens arrays 21,22 and interferometers 23 , and for surface patterning [24][25][26][27][28][29] and film formation 30 .…”

Two-Dimensional Arrays of Poly(N-Isopropylacrylamide) Microspheres: Formation, Characterization and Application

“…Here, not only the size, morphology and position of the hydrogel spheres in the collapsed state (dry sample) can be studied, but also the mechanical properties of the microgel at the substrate surface and its swelling behavior in liquid can be investigated [9,[25][26][27][28][29]. For the latter, a strong adhesion of the polyNIPAm microspheres to the substrate surface is crucial in order to guaranty stable imaging conditions.…”