DNA-Coated Functional Oil Droplets

Abstract

Many industrial soft materials include oil-in-water (O/W) emulsions at the core of their formulations. By using tuneable interface stabilizing agents, such emulsions can self-assemble into complex structures. DNA has been used for decades as a thermoresponsive, highly specific binding agent between hard and, recently, soft colloids. Up until now, emulsion droplets functionalized with DNA had relatively low coating densities and were expensive to scale up. Here, a general O/W DNA-coating method using functional nonionic amphiphilic block copolymers, both diblock and triblock, is presented. The hydrophilic poly(ethylene glycol) ends of the surfactants are functionalized with azides, allowing for efficient, dense, and controlled coupling of dibenzocyclooctane-functionalized DNA to the polymers through a strain-promoted alkyne-azide click reaction. The protocol is readily scalable due to the triblock's commercial availability. Different production methods (ultrasonication, microfluidics, and membrane emulsification) are used with different oils (hexadecane and silicone oil) to produce functional droplets in various size ranges (submicron, ∼20 and >50 μm), showcasing the generality of the protocol. Thermoreversible submicron emulsion gels, hierarchical "raspberry" droplets, and controlled droplet release from a flat DNA-coated surface are demonstrated. The emulsion stability and polydispersity is evaluated using dynamic light scattering and optical microscopy. The generality and simplicity of the method opens up new applications in soft matter, biotechnological research, and industrial advances.

Printing Life‐Inspired Subcellular Scale Compartments with Autonomous Molecularly Crowded Confinement

“…Once engulfed in the mineral oil, the molecules dissolved in these small fL‐scale droplets would diffuse in the mineral oil drop. In order to avoid molecular leakage into the oil phase, the fL‐droplets are spiked under optimized conditions with a mixture of nonionic surfactants including the di‐block copolymer poly(ethylene glycol)‐block‐poly(propylene glycol)‐block‐poly(ethylene glycol) (PEG‐PPG‐PEG) (F108; 0.03% w/v), an efficient amphiphilic stabilizer of oil/water interfaces in emulsion droplets, and Tween‐20 (0.05% v/v), already reported as inhibitor of colloidal aggregation in solution …”

“…About 5000 aqueous droplets at the fL‐scale were injected in about 10 nL mineral oil drops arrayed with a spacing of 1 mm on a glass chip in a 4 × 2 format (see Figure 2 a). Notably, fL‐droplets are not stable in absence of F108, which has been observed to self‐assemble at the water/oil interface avoiding the above cited molecular diffusion to the oil phase . Once injected in mineral oil drops, given the high surface tension gradient between water and oil, aqueous fL‐droplets are subjected to Marangoni flows toward the border of the oil drop resulting in an almost‐regular droplet pattern (see the Supporting Information for details).…”

Dynamic Light Scattering Based Microrheology of End-Functionalised Triblock Copolymer Solutions

“…We covalently attached N -groups to the PEO chain ends of F108, following a protocol described by Caciagli et al [ 23 ]. This protocal was adapted from a method introduced by Oh et al [ 34 ].…”

“…Their extension to polymeric micelles has, however, not been attempted yet. Recent advances have shown the possibility of attaching DNA to PEG-PPO-PEG triblock copolymers [ 23 , 24 ]. These copolymers, commercially known as Synperonic (manufactured by Croda), Pluronics ® (BASF) or Poloxamers (ICI), have been successfully used in several applied areas such as particle synthesis [ 25 ], emulsion formulation [ 26 ], cosmetics [ 27 ] and coatings [ 28 ].…”

Self-Assembly of DNA-Grafted Colloids: A Review of Challenges

“…The patchiness results from the fact that the linkers can diffuse on the surface of the droplets, and can be recruited into patches, giving rise to defined valency. We cite some relevant literature for the readers interested in DNA coated droplets [ 34 , 35 , 36 , 37 , 38 , 39 , 40 ]. It is also worth mentioning here that, as a strategy, self-assembly is largely confined to nano/micro size components.…”