# Recent Advances in Research from Nanoparticle to Nano-Assembly: A Review
## 3 Stimuli Dependent Techniques
### Chemical Stimuli-Based Self-Assembly of Nanomaterials
#### 3.1.3 Bio-Macromolecule-Induced Self-Assembly  
In geometric terms, a template is a substrate with a pre-defined active surface. Template-directed SA is recognized as an ideal approach for tuning the shape and chirality of NPs in a pre-defined order. Strong interactions between the functionalized NPs and multiple  
Figure 3: (**A**) pH-responsive polymer-driven self-assembly of terpolymer block particles at different pH levels. These images were cited and reproduced from the reference [65]. (**B**) Assembly and disassembly of citrate-capped Au NPs in the presence of APTES with the supplementation of acid and base to the medium. (**i–iv**) TEM images of Au NPs, self-assembled Au NPs in APTES, disassembly of Au NPs when pH changes from 9.8 to 12, and retained assembly when pH decreased from 12 to 9.8 pH. (**v**) Digital image of the visible color change with respect to self-assembly and disassembly. These images were cited and reproduced from the reference [66]. well-defined binding sites of the template direct the assembly of NPs in a pre-specific manner. With this concept, a diversity of classes of templates such as block co-polymers, macromolecules, and single molecules have been used in manipulating the organization of NPs. Due to their spatial distribution of reactive sites and great affinity for specific particle deposition control, the hierarchical structures on soft templates (bio-macromolecules) are advantageous compared to hard templates (carbon tubes). Bio-macromolecule-induced (particularly deoxyribonucleic acid (DNA)-driven) assembly is a promising and attractive approach in the development of novel assembled NMs. Their multi-functional binding sites with a phosphate backbone provide strong interactions with metals for binding [67]. The precise organization of DNA strands offers a pre-eminent technique to generate various complex nanostructures. DNA technology-based SA can be divided in two approaches. In the first case, metal NPs were functionalized with single or several Immobilized DNA strands and allowed to aggregate in a cross-linking manner in the presence of complementary linker [68], schematic of cross-linking manner was shown in Figure 4A (right) and the respective TEM was shown in the Figure 4A (left(i)). This process was deliberately employed to generate various shapes and ordered structures. Apart from this, short DNA strands are artificially modified by changing the bases and the insert/removal of specific sites to obtain the complex SA of NPs. However, immobilized regioselective decoration on DNA strands is one of the advanced processes in DNA-templated SA technology. Long and short facets of variously shaped NPs were intentionally decorated with differently sequenced oligonucleotide DNA strands. Subsequent supplementation of matched and mismatched complementary linkers allowed the NPs to form duplexes and assemble in a side-by-side (as shown in Figure 4B(i)) or end-to-end manner (as shown in Figure 4B(ii)) [69] that was largely dependent on the complementary linker, as shown in Figure 4B (right schematic). Figure 4: **(A)** An illustrative example of the DNA-driven self-assembly where the surface of NPs functionalized with single-strand DNA and induced self-assembly via complementary linker. This image was cited and reproduced from the reference [68], **(i)** shows the respective TEM image of SA NPs. **(B)** DNA-driven regioselective self-assembly in side-by-side and end-to-end manner induced by matched and mismatched oligonucleotides. **(i,ii)** are the respective TEM images. These images were cited and reproduced from the reference [69]. **(C)** DNA origami approach for the synthesis of 2D and 3D Au nanostructures. This image was cited and reproduced from the reference [70]. **(D,E)** are the classical examples for the origami mediated self-assembly. These images were cited and reproduced from the reference [71; 72].