The pursuit of precision in macromolecular science: Concepts, trends, and perspectives

Peptide/protein-based macrocycles: from biological synthesis to biomedical applications

Living organisms have evolved cyclic or multicyclic peptides and proteins with enhanced stability and high bioactivity superior to their linear counterparts for diverse purposes. Herein, we review recent progress in applying this concept to artificial peptides and proteins to exploit the functional benefits of these macrocycles. Not only have simple cyclic forms been prepared, numerous macrocycle variants, such as knots and links, have also been developed. The chemical tools and synthetic strategies are summarized for the biological synthesis of these macrocycles, demonstrating it as a powerful alternative to chemical synthesis. Its further application to therapeutic peptides/proteins has led to biomedicines with profoundly improved pharmaceutical performances. Finally, we present our perspectives on the field and its future developments.

Synthesis, self-assembly and anticancer drug encapsulation and delivery properties of cyclodextrin-based giant amphiphiles

Cyclodextrin-calixarene giant amphiphiles that can self-assemble into nanospheres or nanovesicles have the ability to encapsulate the anticancer hydrophobic drugs docetaxel, temozolomide and combretastatin A-4 with encapsulation efficiencies >80% and deliver them to tumoral cells, enhancing their therapeutic efficacy by 1-3 orders of magnitude. These amphiphiles were modified by inserting a disulfide bridge confering them redox responsiveness. Disassembly of the resulting nanocompounds and cargo release was favored by high glutathione levels mimicking those present in the tumor microenvironment. Anticancer drug-loaded nanoformulations inhibited prostate, breast, glioblastoma, colon or cervix cancer cell lines proliferation with IC₅₀ values markedly below those observed for the free drugs. Cell-cycle analysis indicated a similar mechanism of action for drug-loaded nanocompounds and free drugs. The results strongly suggest that the cyclodextrin-calixarene heterodimer prototype is an excellent scaffold for nanoformulations aimed to deliver anticancer drugs with limited bioavailability due to low solubility to tumoral cells, markedly increasing their effectivity.

Macromolecular Isomerism in Giant Molecules

Macromolecular isomerism has been an important yet largely understudied subject. Giant molecules based on molecular nanoparticles exhibit properties highly dependent on the primary structures, providing a platform for such studies. Various isomers have been designed, synthesized and characterized, including sequence-, regio-, and topo-isomers. The self-assembly of these isomers is influenced by the distinct symmetry and collective interaction of each building block in a subtle and delicate way. The results suggest that isomerism may be exploited as a new way for fine-tuning the structures and properties of macromolecules, which should be of great interest in both fundamental research and technical innovation.

Versatile Construction of Single-Tailed Giant Surfactants with Hydrophobic Poly(ε-caprolactone) Tail and Hydrophilic POSS Head

Giant surfactants refer to a new kind of amphiphile by incorporating functional molecular nanoparticles with polymer tails. As a size-amplified counterpart of small-molecule surfactants, they serve to bridge the gap between small-molecule surfactants and amphiphilic block copolymers. This work reports the design and synthesis of single-tailed giant surfactants carrying a hydrophobic poly(ε-caprolactone) (PCL) as the tail and a hydrophilic cage-like polyhedral oligomeric silsesquioxane (POSS) nanoparticle as the head. The modular synthetic strategy features an efficient "growing-from" and "click-modification" approach. Starting from a monohydroxyl and heptavinyl substituted POSS (VPOSS-OH), a PCL chain with controlled molecular weight and narrow polydispersity was first grown by the ring-opening polymerization (ROP) of ε-CL under the catalysis of stannous octoate, leading to a PCL chain end-capped with heptavinyl substituted POSS (VPOSS-PCL). To endow the POSS head with adjustable polarity and functionality, three kinds of hydrophilic groups, including hydroxyl groups, carboxylic acids, and amine groups, were installed to the periphery of POSS molecule by a high-efficiency thiol-ene "click" reaction. The compounds were fully characterized by NMR, gel permeation chromatography (GPC), MALDI-TOF mass spectrometry, and TGA analysis. In addition, the preliminary self-assembly study of these giant surfactants was also investigated by TEM and dynamic laser light scattering (DLS), which indicated that they can form spherical nanoparticles with different diameters in aqueous solution. This work affords a straightforward and versatile way for synthesizing single-tailed giant surfactants with diverse head surface functionalities.