Periodic Reporting for period 3 - LifeLikeMat (Dissipative self-assembly in synthetic systems: Towards life-like materials)
Période du rapport: 2022-01-01 au 2023-07-31
The goal of the proposed research program is to develop novel principles for designing dissipative self-assembly systems and to fabricate a range of dissipative materials based on these principles. We are inspired by living organisms - sophisticated self-assembled structures that exist and operate far from thermodynamic equilibrium and represent the ultimate example of dissipative self-assembly. They remain stable at highly organized states owing to the continuous consumption of energy stored in "chemical fuels", which they convert into low-energy waste. Work during the first period of the project focused on developing building blocks for novel dissipative self-assembly systems. We have reported on several host–guest inclusion complexes incorporating photoswitchable building blocks, which can exist in a nonequilibrium state under light irradiation. We have also fabricated a nanoparticle dissipative self-assembly system which operates in water and is dependent on the presence of the ATP fuel, which paves the way towards integrating this synthetic system within biological environments. Developing the means to rationally design dissipative self-assembly systems will greatly impact a range of industries, including the pharmaceutical and energy sectors.
In the first part of the project, the work focused on synthesizing the building blocks for more complex molecules and materials, which will be investigated in the context of dissipative self-assembly in due course. First, we studied host–guest inclusion complexes comprising a flexible metal–organic cage host and various light-responsive guests. Upon irradiation with a specific wavelength of light, these light-responsive compounds can be isomerized into their metastable states. If these metastable states can induce a self-assembly process, the resulting assembled structures will only exist under continuous light irradiation (i.e. light-induced dissipative self-assembly).
As the first such complex, we studied a combination of the metal–organic cage and phenylazopyrazole. We showed that each cage molecule can encapsulate two molecules of the phenylazopyrazole guest. Upon exposure to UV light, the trans guest undergoes photoisomerization to the bulkier cis form, which is too bulky to remain in the cage as a dimer. Hence, light-induced expulsion of the guest from the cage has been achieved. When the irradiation is ceased, back-isomerization proceeds and the expelled guest re-enters the cage (Beilstein J. Org. Chem. 2020). As another photoresponsive guest, dihydropyrene (DHP) was used. In this case, exposure to blue light induced an efficient photoswitching process without the guest being expelled from the cage; instead, we demonstrated that the cage can greatly improve the reversibility of the photoswitching process (J. Am. Chem. Soc 2020). More recently, we reported on 2:1 inclusion complexes of the metal–organic cage and fluorescent dyes (J. Am. Chem. Soc. 2020). These inclusion complexes are currently being incorporated as key elements of various dissipative self-assembly systems.
In addition, we studied the behavior of light-switchable compounds within a new type of medium: nanoporous networks of silicone filaments (Nano Letters 2019). More recently, various families of photoswitchable molecules that can be used to control self-assembly of nanoparticles using light, thus inducing dissipative self-assembly processes, have been reviewed (Adv. Mater. 2020). In another review, analogies and differences between light- and chemically fuelled dissipative self-assembly systems have been developed (Chem 2021).
At the same time, we have made significant progress on developing nanoparticle-based dissipative self-assembly. Three conceptually different approaches to dissipative self-assembly have been developed of which two will be communicated soon. The third one has recently been published (Nat. Chem. 2021) and it is based on electrostatic interactions between positively charged nanoparticles and negatively charged, highly energetic small molecules, such as ATP. In the presence of phosphatase enzymes, ATP is hydrolyzed into smaller ions, which do not support the aggregated state of the NPs. However, this hydrolysis reaction is slower than self-assembly; thus, in the presence of an enzyme, the nanoparticles only exist in the assembled state for as long as the ATP “fuel” is continuously supplied.
As the first such complex, we studied a combination of the metal–organic cage and phenylazopyrazole. We showed that each cage molecule can encapsulate two molecules of the phenylazopyrazole guest. Upon exposure to UV light, the trans guest undergoes photoisomerization to the bulkier cis form, which is too bulky to remain in the cage as a dimer. Hence, light-induced expulsion of the guest from the cage has been achieved. When the irradiation is ceased, back-isomerization proceeds and the expelled guest re-enters the cage (Beilstein J. Org. Chem. 2020). As another photoresponsive guest, dihydropyrene (DHP) was used. In this case, exposure to blue light induced an efficient photoswitching process without the guest being expelled from the cage; instead, we demonstrated that the cage can greatly improve the reversibility of the photoswitching process (J. Am. Chem. Soc 2020). More recently, we reported on 2:1 inclusion complexes of the metal–organic cage and fluorescent dyes (J. Am. Chem. Soc. 2020). These inclusion complexes are currently being incorporated as key elements of various dissipative self-assembly systems.
In addition, we studied the behavior of light-switchable compounds within a new type of medium: nanoporous networks of silicone filaments (Nano Letters 2019). More recently, various families of photoswitchable molecules that can be used to control self-assembly of nanoparticles using light, thus inducing dissipative self-assembly processes, have been reviewed (Adv. Mater. 2020). In another review, analogies and differences between light- and chemically fuelled dissipative self-assembly systems have been developed (Chem 2021).
At the same time, we have made significant progress on developing nanoparticle-based dissipative self-assembly. Three conceptually different approaches to dissipative self-assembly have been developed of which two will be communicated soon. The third one has recently been published (Nat. Chem. 2021) and it is based on electrostatic interactions between positively charged nanoparticles and negatively charged, highly energetic small molecules, such as ATP. In the presence of phosphatase enzymes, ATP is hydrolyzed into smaller ions, which do not support the aggregated state of the NPs. However, this hydrolysis reaction is slower than self-assembly; thus, in the presence of an enzyme, the nanoparticles only exist in the assembled state for as long as the ATP “fuel” is continuously supplied.
The results of the project go significantly beyond the state of the art, as evidenced by publications in some of the top journals in the field (e.g. . Am. Chem. Soc. (2), Nano Letters, Nature Chemistry). Three additional papers are currently under review and several others will soon be submitted to recognized chemistry journals. The field of dissipative, light-induced self-assembly of nanoparticles has been reviewed in a recent review paper (Adv. Mater. 2020) and review paper focusing on the comparison of chemically and light-fueled dissipative self-assembly was published earlier this year (Chem 2021). Our goal is to maintain this trajectory until the end of the project and to continue working on the goals as specified in the grant proposal. For example, we are currently integrating our fluorescent host–guest inclusion complexes with ones incorporating photoswitchable components – this integration will enable us to follow dissipative self-assembly processes by monitoring light emission from the system.