Macromolecular Crowding as an Intracellular Stimulus for Responsive Nanomaterials

Abstract

Stimuli-responsive materials are exploited in biological, materials, and sensing applications. We introduce a new endogenous stimulus, biomacromolecule crowding, which we achieve by leveraging changes in thermoresponsive properties of polymers upon high concentrations of crowding agents. We prepare poly­(2-oxazoline) amphiphiles that exhibit lower critical solution temperatures (LCST) in serum above physiological temperature. These amphiphiles stabilize oil-in-water nanoemulsions at temperatures below the LCST but are ineffective surfactants above the LCST, resulting in emulsion fusion. We find that the transformations observed upon heating nanoemulsions above their surfactant’s LCST can instead be induced at physiological temperatures through the addition of polymers and protein, rendering thermoresponsive materials “crowding responsive.” We demonstrate that the cytosol is a stimulus for nanoemulsions, with droplet fusion occurring upon injection into cells of living zebrafish embryos. This report sets the stage for classes of thermoresponsive materials to respond to macromolecule concentration rather than temperature changes.

Poly(2-oxazoline) with Pendant Hydroxyl Groups via a Silyl Ether-Based Protecting Group

“…The solvent was removed under reduced pressure, and the crude product was purified by column chromatography (EA:hexane 9:1), resulting in a clear, colorless oil (5.09 g, 33%). 1 H NMR (400 MHz, CDCl 3 ) δ 4.14 (t, J = 9.5 Hz, 2H), 3.74 (t, J = 9.4 Hz, 2H), 3.61 (t, J = 6.4 Hz, 2H), 2.21 (t, J = 7.6 Hz, 2H), 1.59 (m, J = 7.6 Hz, 2H), 1.49 (m, J = 7.0 Hz, 2H), 1.36 (m, J = 4.0 Hz, 2H), 0.98 (s, 9H). 13 C NMR (400 MHz, CDCl 3 ) δ = 169.…”

“…The monomer was then purified by distillation in vacuo (3.5 × 10 −3 bar, 20 °C) three times, resulting in the purified PropOx as a clear colorless liquid (22.5 g, 34%). 1 H NMR (400 MHz, CDCl 3 ) δ 4.23 (t, J = 9.5 Hz, 2H), 3.83 (t, J = 9.4 Hz, 2H), 2.26 (t, J = 7.5 Hz, 2H), 1.67 (d, J = 7.5 Hz, 2H), 0.98 (t, J = 7.4 Hz, 3H). 13 Synthesis of 2-n-Pentanol-2-oxazoline (OHOx).…”

“…The same equivalent of ethanolamine (26.8 g, 438 mmol) was then added to the flask and subsequently heated at 120 °C for 2 h. Titanium(IV) butoxide (7.00 mL, 21.9 mmol) was then added to the reaction mixture and heated in vacuo at 230 °C for 2 h. The reaction mixture was then distilled in vacuo (3.5 × 10 −3 bar, 110 °C) four times to obtain the purified 2-n-pentanol-2-oxazoline as a clear pale-yellow oil (42.7 g, 62%). 1 H NMR (400 MHz, CDCl 3 ) δ 4.23 (t, J = 9.5 Hz, 2H), 3.81 (t, J = 9.4 Hz, 2H), 3.65 (q, J = 5.2 Hz, 2H), 2.29 (t, J = 7.3 Hz, 2H), 1.62 (m, J = 6.0 Hz, 6H), 1.45 (q, J = 7.1 Hz, 2H) ppm. 13 Synthesis of TIPSOx.…”

Temperature sensitive copolymers as a model system for understanding the physical basis of nonequilibrium assembly

“…Despite these practical features, there has been limited characterization of the hysteretic behavior. Additionally, synthetic thermosensitive polymers have already found a niche as attractive candidates in tissue engineering and drug delivery applications 17,34,35 further motivating the identification of connections between environmental parameters and nonequilibrium properties. With this synthetic model system, we demonstrate the role of composition and hydrophobicity, path, and environment effects in modulating nonequilibrium dynamics in phase behavior (Figure 1b).…”

Temperature sensitive copolymers as a model system for understanding the physical basis of nonequilibrium assembly

“…And yet, despite these basic design principles, there has been limited characterization of the hysteretic behavior. Additionally, synthetic thermosensitive polymers have already found a niche as attractive candidates in tissue engineering and drug delivery applications 11,28,29 further motivating the identification of connections between environmental parameters and nonequilibrium properties. With this synthetic model system, herein we demonstrate the role of composition and hydrophobicity, path, and environment effects in modulating nonequilibrium dynamics in phase behavior (Figure 1B).…”