A new method to escape metastability in a non-equilibrium system of DNA-functionalized colloids

Professor Liang Haojun from the University of Science and Technology of China (USTC), Chinese Academy of Sciences (CAS), proposed a new method to escape metastability for self-assembly in a system far from equilibrium. The study was published PNAS.

Self-assembly refers to the process by which aggregated elementary elements (molecules, nanoparticles, etc.) form self-ordered structures through non-covalent interactions. His excellent ability to create new materials attracted attention. In an ideal assembly process, the system reaches a thermodynamic steady state with minimal free energy and forms a high-quality assembly structure. However, for an assembly system far from equilibrium, it tends to get stuck in a metastable state where the local free energy is very low, which prevents the formation of a high-quality assembly structure.

How to circumvent metastability in a system far from equilibrium is considered a challenging puzzle in the field of self-assembly. For a collection of DNA-functionalized nanoparticles, a conventional far-from-equilibrium system, the entropy-driven thermal annealing strategy constitutes a traditional and widely accepted method to escape metastability. However, aggregation and dispersion of nanoparticles usually occur within a narrow temperature range during annealing. Thermal energy is not selective in correcting misaligned non-covalent bonds. Thermal annealing is not suitable for collecting biologically active particles or under physiological conditions.

Inspired by the catassembler concept proposed by Xiamen University academician TIAN Zhongqun, Prof. LIANG and his team proposed a new method to achieve the catalytic assembly of DNA-functionalized colloidal nanoparticles in a non-equilibrium system. Based on their predictions from theoretical modeling and previous research on a stable enthalpy control strategy for nanoparticle assembly, they used a detachable molecule called a “catassembler” to act as a catalyst, regulate imperfect bonds, and help escape metastability while preserving the system. constructed circle.

In this strategy, a short DNA sequence acting as an accelerator directly competes with the binding end on the surface of the nanoparticle within the assembly structure, and the noncovalent binding of the misjoin can be corrected by the transient DNA sequence. substitution reaction, helps the system escape from metastability. During the process, the accelerator does not disturb the overall framework of the assembly structure and can be removed from the final assembly structure. Moreover, by changing the structural design of the accelerator, it can even reduce the dose of the accelerator and increase its efficiency.

Similarly, based on the same principle, different crystal symmetric superlattice structures can be obtained by changing the core type of nanoparticles in the two-component system and directly adding the appropriate DNA promoter after designing the DNA sequence. This strategy facilitates the implementation of nanoparticle assembly, since the chemical reaction takes place at a constant temperature. Moreover, this DNA accelerator tuning strategy is simple and effective, which makes the “solid-solid” phase transformation between different colloidal crystals easier to achieve after breaking the temperature tuning constraints and the initial phase state free energy constraints. It shows its application potential in structurally reconfigurable “solid-solid” phase transformation bioinorganic composites.

As a general method for regulating non-covalent interactions in assembly structures, the accelerator strategy presented in this study is expected to be extended to control and fabricate assembly processes for other soft material systems (polypeptides, block copolymers, etc.). far from equilibrium.


University of Science and Technology of China

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