A new method was developed in engineering nanoparticles by using building blocks in the form of DNA. A type of nanoparticle coated with nucleic acids is found to be programmable into ordered arrays known as colloidal crystals. This technological stride holds promise in medicine, energy storage, and the environment, according to the International Institute for Nanotechnology.
Exploring DNA Interaction Strength
Researchers have discovered that colloidal crystal engineering can be improved by adjusting DNA interaction strength to enhance its purpose in creating a range of functional nanoparticles. A group investigated scientists headed by Professor Chad Mirkin of Northwestern's Weinberg College of Arts and Sciences.
In this study, two groups of complementary nanoparticles were created. One batch contains complementary base pairs of the DNA or the "seed" PAEs which act as the initial crystals that form a solution. The other batch contains mismatched DNA base pairs or the "growth" PAEs which serve as the weaker crystals that grow together with the already existing ones.
The method used by the researchers allowed them to improve the uniformity of the crystals. They could also independently choose the nanoparticle and the DNA shell sequence to be mixed and matched later. In other words, various kinds of materials are incorporated into the crystals.
Mirkin and his team believe this approach is essential in making core-shell structures in one step. The previous approaches needed multiple steps. The first crystal undergoes post-synthetic stabilization before proceeding to the second growth step.
"With these two different DNA interaction strengths, if we can essentially label where the different types of particles are going in the final structure, it's useful to investigate those fundamental questions," said Kaitlin Landy of the Department of Chemistry at the Weinberg College of Arts and Sciences.
The team plans to use different particle cores to track the crystallization processes in the future.
Challenge in Crystal Engineering
The field of colloidal crystal engineering faces the synthetic challenge regarding the programmed crystallization of particles. According to ACS Nano, next-generation materials' development relies on the ability to arrange colloidal particles into a crystalline structure with controlled symmetry.
Using DNA for colloidal crystal engineering involves the modification of nanoparticles into programmable atom equivalents, also known as PAEs. The PAEs are then used to form colloidal crystals, which is important in designing programmable, synthetic DNA sequences.
The conventional process in crystal engineering focuses on manipulating the size and shape of the crystal. However, this approach faces a challenge due to the difficulty separating crystal formation and growth even if established methods are used.
New crystals can emerge throughout the process while the current ones are growing. As a result, some minute crystals can form late in the process, with the large ones already increasing. This could lead to a population of crystals with non-uniform sizes. It is important, therefore, to separate the two events with a focus on the crystal growth from the initial formation.
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