Supramolecular self-assembly approach

In conclusion, size-controlled Au-SNPs have been successfully demonstrated by supramolecular self-assembly approach. The resulting Au-SNPs exhibited significantly enhanced photothermal effects and were used to demonstrate the targeted photothermal treatment of a subpopulation of cancer cells after the incorporation of target-specific ligands. It is anticipated that Au-SNPs could serve as a powerful photothermal agent. 

The supramolecular self-assembly approach in the solid state from solution, leading to well defined nanostructures has been discussed in a comprehensive paper that describes the main features related to this method interactions of macromolecules with the substrate surface, design of well defined molecular structure, and use of block copolymers have been considered in a joint experimental-theoretical approach, in view of understanding the structure-property relationship of conjugated nanostructures [30],... 

Supramolecular self-assembly has been found to be dramatically accelerated in some cases, and this is perhaps the reason why solventless reactions have been rapidly adopted by coordination chemists. For example, the formation of a platinum-containing square is dramatically accelerated compared with the same reaction in water (Figure 2.3). In water, the reaction needed to be heated at 100 °C for 4 weeks. In a solvent free approach, approximately the same yield was achieved in 10 min at room temperature. Water and ethanol were the only solvents used in the work up of the reaction. This approach was then extended to bowl-shaped and helical supramolecular structures. 

As well as the examples given in the previous section, in which complementarity of functional groups is used to form supramolecules, there are others in which selfcomplementarity generates interesting homodimeric complexes. A case in point is aminomethylbenzo[18]crown-6 which forms dimers when the amine sidearm is protonated [1]. The ammonium-[18]crown-6 motif is well known and, in this molecule, both host and guest are joined. More complex examples, such as those in Figure 5.8, include the self-complementary tennis balls [2] and other cavitands [3-5] designed by Rebek who has shown how the relative positions and orientations of solvent encapsulated within dimeric assemblies can be determined, in the absence of X-ray data, by NMR. A concise treatment of the many approaches to supramolecular self-assembly are outlined in a 1995 review [6]. 

When the coordination bonds that hold these assemblies together are both stable and inert, their formation from the components occurs under kinetic rather than thermodynamic control and it is thus disputable if they can be truly defined as supramolecular systems. On the other hand, owing to their kinetic stability, some of these species can be further exploited as building blocks in the construction of higher order architectures through a hierarchical self-assembly approach (see for example the molecular sandwiches 13-15). Through this modular approach, multichromophore systems become easily accessible on demand, with a limited synthetic effort. 

Although many materials types are available, the main focus is on peptide-based supramolecular systems, since these materials are most frequently utilized in tissue engineering applications. Overall, it is evident that supramolecular systems have great potential in tissue engineering due to their bottom-up self-assembly approach, which employs nanostructured formations to enhance molecular levels interactions with living systems. 

Approaching this new strategy, many different supramolecular self-assembling peptides have been developed and investigated by various research groups as potential functionalized scaffolds for stimulating bone tissue regeneration. 

A solution-based self-assembly approach by direct mixing of H2PtCl6 and Ru(bpy)3Cl2 aqueous solutions was employed for the synthesis of Ru(bpy)3 " -containing supramolecular microstructure [65]. These microstructures possess exceptional ECL behaviors and hence hold great promise as new luminescent materials. These structures consist of a large quantity of star-shaped microstructures with six branches developing the idea that electrostatic attractions between... 

Extension of this self-assembly approach to supramolecular engineering has led to an alternate motif for noncovalent cross-linking, a series of bisthymines that are complementary to the diamidopyridine side chains of polymer 6 (33). Upon combination in non-polar media thermally reversible, micrometer scale spherical aggregates were formed (Figs. 13b and 13c). 

Figure 10 Graphical schematic representations of the self-assembly approach for producing a combinatorial library of DNA-encapsulated supramolecular nanoparticles (DNA C SNPs), in which a broad structuraFfunctional diversity can be programmed into individual DNA C SNPs (1) by systematically altering the mixing ratios of the five functional molecular building blocks, that is, CD-PEI (2), Ad-PAMAM (3), Ad-PEG (4), RGD-PEG-Ad (5), and TAT-PEG-Ad (6), as well as DNA plasmid (7a enhanced green fluorescent protein (EGFP) and 7b firefly luciferase (FLuc)).

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