Copper Nanodrugs with Controlled Morphologies through Aqueous Atom Transfer Radical Polymerization

Copper (Cu) nanodrugs can be facilely prepared through atom transfer radical polymerization (ATRP) in an aqueous medium. However, it is difficult to control the morphology of Cu nanodrugs and thereby optimize their anticancer activity. In this work, aqueous ATRP was combined with polymerization-induced self-assembly (PISA) to prepare Cu nanodrugs with various morphologies. We mapped the relationship between polymerization condition and product morphology in which each morphology shows a wide preparation window. Decreasing the reaction temperature and feeding more Cu catalysts can improve the mobility of chains, facilitating the morphology evolution from sphere to other high-order morphologies. The resultant Cu nanodrugs with high monomer conversion and high Cu loading efficiency could be easily taken by cancer cells, showing excellent anticancer efficacy in vitro. This work proposed a potential strategy to prepare Cu nanodrugs with a specific morphology in batches, providing the method to optimize the anticancer efficacy through morphology control.

Modern Trends in Polymerization-Induced Self-Assembly

Polymerization-induced self-assembly (PISA) is a powerful and versatile technique for producing colloidal dispersions of block copolymer particles with desired morphologies. Currently, PISA can be carried out in various media, over a wide range of temperatures, and using different mechanisms. This method enables the production of biodegradable objects and particles with various functionalities and stimuli sensitivity. Consequently, PISA offers a broad spectrum of potential commercial applications. The aim of this review is to provide an overview of the current state of rational synthesis of block copolymer particles with diverse morphologies using various PISA techniques and mechanisms. The discussion begins with an examination of the main thermodynamic, kinetic, and structural aspects of block copolymer micellization, followed by an exploration of the key principles of PISA in the formation of gradient and block copolymers. The review also delves into the main mechanisms of PISA implementation and the principles governing particle morphology. Finally, the potential future developments in PISA are considered.

Polymerization-Induced Self-Assembly for Efficient Fabrication of Biomedical Nanoplatforms

Amphiphilic copolymers can self-assemble into nano-objects in aqueous solution. However, the self-assembly process is usually performed in a diluted solution (<1 wt%), which greatly limits scale-up production and further biomedical applications. With recent development of controlled polymerization techniques, polymerization-induced self-assembly (PISA) has emerged as an efficient approach for facile fabrication of nano-sized structures with a high concentration as high as 50 wt%. In this review, after the introduction, various polymerization method-mediated PISAs that include nitroxide-mediated polymerization-mediated PISA (NMP-PISA), reversible addition-fragmentation chain transfer polymerization-mediated PISA (RAFT-PISA), atom transfer radical polymerization-mediated PISA (ATRP-PISA), and ring-opening polymerization-mediated PISA (ROP-PISA) are discussed carefully. Afterward, recent biomedical applications of PISA are illustrated from the following aspects, i.e., bioimaging, disease treatment, biocatalysis, and antimicrobial. In the end, current achievements and future perspectives of PISA are given. It is envisioned that PISA strategy can bring great chance for future design and construction of functional nano-vehicles.

Phase Diagrams of Polymerization-Induced Self-Assembly Are Largely Determined by Polymer Recombination

In the current work, atom transfer radical polymerization-induced self-assembly (ATRP PISA) phase diagrams were obtained by the means of dissipative particle dynamics simulations. A fast algorithm for determining the equilibrium morphology of block copolymer aggregates was developed. Our goal was to assess how the chemical nature of ATRP affects the self-assembly of diblock copolymers in the course of PISA. We discovered that the chain growth termination via recombination played a key role in determining the ATRP PISA phase diagrams. In particular, ATRP with turned off recombination yielded a PISA phase diagram very similar to that obtained for a simple ideal living polymerization process. However, an increase in the recombination probability led to a significant change of the phase diagram: the transition between cylindrical micelles and vesicles was strongly shifted, and a dependence of the aggregate morphology on the concentration was observed. We speculate that this effect occurred due to the simultaneous action of two factors: the triblock copolymer architecture of the terminated chains and the dispersity of the solvophobic blocks. We showed that these two factors affected the phase diagram weakly if they acted separately; however, their combination, which naturally occurs during ATRP, affected the ATRP PISA phase diagram strongly. We suggest that the recombination reaction is a key factor leading to the complexity of experimental PISA phase diagrams.

Reverse Sequence Polymerization-Induced Self-Assembly in Aqueous Media

We report a new aqueous polymerization-induced self-assembly (PISA) formulation that enables the hydrophobic block to be prepared first when targeting diblock copolymer nano-objects. This counter-intuitive reverse sequence approach uses an ionic reversible addition-fragmentation chain transfer (RAFT) agent for the RAFT aqueous dispersion polymerization of 2-hydroxypropyl methacrylate (HPMA) to produce charge-stabilized latex particles. Chain extension using a water-soluble methacrylic, acrylic or acrylamide comonomer then produces sterically stabilized diblock copolymer nanoparticles in an aqueous one-pot formulation. In each case, the monomer diffuses into the PHPMA particles, which act as the locus for the polymerization. A remarkable change in morphology occurs as the ≈600 nm latex is converted into much smaller sterically stabilized diblock copolymer nanoparticles, which exhibit thermoresponsive behavior. Such reverse sequence PISA formulations enable the efficient synthesis of new functional diblock copolymer nanoparticles.

RAFT Copolymerization of Vinyl Acetate and Acrylic Acid in the Selective Solvent

Reversible addition-fragmentation chain transfer polymerization was successfully applied to the synthesis of the gradient copolymer of acrylic acid and vinyl acetate in the selective solvent. The gradient degree of the copolymer was varied by the monomer feed. The monomer conversion was found to affect the ability of the copolymer to self-assemble in aqueous solutions in narrowly dispersed micelles with an average hydrodynamic radius of about 250 nm. Furthermore, the synthesized copolymers also tended to self-assemble throughout copolymerization in the selective solvent.

Tuning the vesicle-to-worm transition for thermoresponsive block copolymer vesicles prepared via polymerisation-induced self-assembly

Does statistical copolymerization of n-butyl methacrylate with benzyl methacrylate lower the critical temperature required for vesicle-to-worm and worm-to-sphere transitions for diblock copolymer nano-objects in mineral oil?

Forced gradient copolymerisation: a simplified approach for polymerisation-induced self-assembly

In this work, a novel and versatile gradient copolymerisation approach to simplify polymeric nanoparticle synthesis through polymerisation-induced self-assembly (PISA) is reported.

Phase Diagram for Ideal Diblock-Copolymer Micelles Compared to Polymerization-Induced Self Assembly

In this work we constructed a detailed phase diagram for the solutions of ideal diblock-copolymers and compared such diagram with that obtained during polymerization-induced self-assembly (PISA); a wide range of polymer concentrations as well as chain compositions was studied. As the length of the solvophobic block nB increases (the length of the solvophilic block nA was fixed), the transition from spherical micelles to cylinders and further to vesicles (lamellae) occurs. We observed a rather wide transition region between the spherical and cylindrical morphology in which the system contains a mixture of spheres and short cylinders, which appear to be in dynamic equilibrium; the transition between the cylinders and vesicles was found to be rather sharp. Next, upon increasing the polymer concentration in the system, the transition region between the spheres and cylinders shifts towards lower nB/nA values; a similar shift but with less magnitude was observed for the transition between the cylinders and vesicles. Such behavior was attributed to the increased number of contacts between the micelles at higher polymer volume concentrations. We also found that the width of the stability region of the cylindrical micelles for small polymer volume concentrations is in good quantitative agreement with the predictions of analytical theory. The obtained phase diagram for PISA was similar to the case of presynthesized diblock copolymer; however, the positions of the transition lines for PISA are slightly shifted towards higher nB/nA values in comparison to the presynthesized diblock copolymers, which is more pronounced for the case of the cylinders-to-vesicles transition. We believe that the reason for such behavior is the polydispersity of the core-forming blocks: The presence of the short and long blocks being located at the micelle interface and in its center, respectively, helps to reduce the entropy losses due to the insoluble block stretching, which leads to the increased stability of more curved micelles.

A polymerization-induced self-assembly process for all-styrenic nano-objects using the living anionic polymerization mechanism

By combination of the living anionic polymerization (LAP) mechanism with the polymerization-induced self-assembly (PISA) technique, the all-styrenic diblock copolymer poly(p-tert-butylstyrene)-b-polystyrene (PtBS-b-PS) based LAP PISA was successfully developed.

Polymerization techniques in polymerization-induced self-assembly (PISA)

The development of controlled/“living” polymerization greatly stimulated the prosperity of the fabrication and application of block copolymer nano-objects.

Trending methods employed for polymerization induced self-assembly

Mother Nature produces a perfectly defined architecture that inspires researchers to make polymeric macromolecules for an array of functions. The present article describes recent development in the PISA to synthesize polymeric nano-objects.

Self-assembly of amphiphilic copolymers containing polysaccharide: PISA versus nanoprecipitation, and the temperature effect

The self-assembly methods and the temperature have a considerable impact on the morphology of the resulting nanoobjects in the case of amphiphilic glycopolymers.

Synthesis of lipase–polymer conjugates by Cu(0)-mediated reversible deactivation radical polymerization: polymerization vs. degradation

Cu(0)-RDRP was first used for the polymerization-induced self-assembly of lipase–polymer conjugates, inducing the formation of nanospheres with preserved activity and degradability.

Emerging Trends in Polymerization-Induced Self-Assembly

In this Perspective, we summarize recent progress in polymerization-induced self-assembly (PISA) for the rational synthesis of block copolymer nanoparticles with various morphologies. Much of the PISA literature has been based on thermally initiated reversible addition-fragmentation chain transfer (RAFT) polymerization. Herein, we pay particular attention to alternative PISA protocols, which allow the preparation of nanoparticles with improved control over copolymer morphology and functionality. For example, initiation based on visible light, redox chemistry, or enzymes enables the incorporation of sensitive monomers and fragile biomolecules into block copolymer nanoparticles. Furthermore, PISA syntheses and postfunctionalization of the resulting nanoparticles (e.g., cross-linking) can be conducted sequentially without intermediate purification by using various external stimuli. Finally, PISA formulations have been optimized via high-throughput polymerization and recently evaluated within flow reactors for facile scale-up syntheses.

Synthesis of block copolymer nano-assemblies via ICAR ATRP and RAFT dispersion polymerization: how ATRP and RAFT lead to differences

Block copolymer nano-assemblies were synthesized via ICAR ATRP dispersion polymerization employing the CuBr₂/tris(2-pyridylmethyl)amine catalyst in an alcoholic solvent at a relatively low temperature of 45 °C.

A new visible light and temperature responsive diblock copolymer

A visible light and temperature responsive diblock copolymer of poly[6-(2,6,2′,6′-tetramethoxy-4′-oxyazobenzene) hexyl methacrylate]-block-poly(N-isopropylacrylamide) (PmAzo-b-PNIPAM) was synthesized via RAFT polymerization by carefully tuning the polymerization conditions.

Alcohol-based PISA in batch and flow: exploring the role of photoinitiators

Polymerization-induced self-assembly (PISA) via PhotoRAFT (photoinduced reversible addition–fragmentation radical transfer) was investigated in polar solvents via continuous flow reactors.

Polymerization induced self-assembly: an opportunity toward the self-assembly of polysaccharide-containing copolymers into high-order morphologies

Self-assembly of polysaccharide-containing amphiphilic copolymers: polymerization induced self-assembly versus traditional techniques.

Molecular bionics - engineering biomaterials at the molecular level using biological principles

Life and biological units are the result of the supramolecular arrangement of many different types of molecules, all of them combined with exquisite precision to achieve specific functions. Taking inspiration from the design principles of nature allows engineering more efficient and compatible biomaterials. Indeed, bionic (from bion-, unit of life and -ic, like) materials have gained increasing attention in the last decades due to their ability to mimic some of the characteristics of nature systems, such as dynamism, selectivity, or signalling. However, there are still many challenges when it comes to their interaction with the human body, which hinder their further clinical development. Here we review some of the recent progress in the field of molecular bionics with the final aim of providing with design rules to ensure their stability in biological media as well as to engineer novel functionalities which enable navigating the human body.

Liposomes and polymersomes: a comparative review towards cell mimicking

Minimal cells: we compare and contrast liposomes and polymersomes for a bettera priorichoice and design of vesicles and try to understand the advantages and shortcomings associated with using one or the other in many different aspects (properties, synthesis, self-assembly, applications).