Designing Functional Supramolecular Assemblies for Enzyme Activity Regulation

Abstract

Enzymes are essential biocatalysts that perform chemical and biochemical reactions in living organisms. Dysregulation in enzyme activity is responsible for several metabolic disorders and lethal diseases such as Alzheimer’s and cancer. The ability to precisely regulate enzyme activity opens new opportunities for disease treatment and management. Given the relevance, there is a need to develop innovative materials for enzyme activity regulation that can overcome challenges like biocompatibility, durability, fabrication and cost efficiency. In the attempt to create functional and adaptive materials to regulate enzyme activity, we have developed novel soft materials utilizing supramolecular chemistry concepts. The thesis focuses on the development of supramolecular architectures that can adapt, respond to stimuli, and exhibit emergent properties essential for biological applications including enzyme catalysis and therapeutics. We first designed a supramolecular vesicular system composed of a cationic surfactant with guanidinium headgroup and ATP as a capping agent. Notably, ATP serves a dual function of the structural component and features a surface-exposed handle to “glue” the Cytochrome c enzyme on the surface of vesicles. The increased local concentrations of the enzyme and proximity with the substrate lead to enhancement in the activity of the enzyme. Further, the efficacy of the system was realized in the activation of biocatalytic cascades with augmented enzymatic reactions. Inspired by the natural processes in life that exist out of equilibrium, we dynamically regulated the formation and the disruption of vesicles using the enzyme potato apyrase, which can hydrolyse ATP. Consequently, temporal regulation of individual enzymes and catalytic cascades is achieved in response to the ATP oscillation. The system provided a new strategy to regulate enzyme activity in a spatiotemporal way. To regulate the activity of biologically relevant enzymes such as chymotrypsin and beta- lactamase, we developed a coordination polymer of Ag(I) with thiol ligands featuring carboxylate functionality. The coordination polymer provides a modular platform to regulate their interaction with proteins. The surface recognition of the active site of the enzymes by the polymer assembly hinders the substrates from binding, thereby modulating the catalytic activity. In the context of combating antibiotic resistance, we utilized this approach to inhibit bacterial beta-lactamase enzymes, thereby restoring the efficacy of beta-lactam antibiotics. In another work, we designed an artificial biomolecular condensate using polystyrene sulfonate polymer and a hetero-divalent cross-linker. The resulting stable complex coacervates showed efficient compartmentalization properties imitating natural cells. The confinement of enzymes such as horseradish peroxidase and glucose oxidase through encapsulation leads to enhanced activity of the biocatalytic reactions. Beyond chemical and spatiotemporal responses, light offers an innovative and non-invasive approach to externally modulate enzyme activity. In this context, we developed a unique oxidase mimicking DNAzyme integrating DNA with a Pt-based metal complex, whose activity is controllable by light stimulus. The straightforward approach of utilizing supramolecular interactions to create oligonucleotide-based artificial enzyme mimics (named “nucleozymes”) offers efficient catalysis, longer stability, robustness and tunable activity through light. These functional oligonucleotide-based higher-order materials, resistant to nuclease and coupled with on-demand photoactivation of exclusive oxidase enzyme-like activity, make the new supramolecular platform a promising candidate for practical biomedical applications. Furthermore, to overcome the limitations of metal-based oxidase-mimic, we utilized self- assembling small organic molecular emitters exhibiting aggregation induced emission properties. The emitters organize into higher-order fibrous structures and exhibit oxidase- like activity upon light irradiation, hence referred to as “photoswitchable suprazyme”. The system operates by generating superoxide radicals through dissolved oxygen due to the efficient separation of holes and electrons, unlocking a novel pathway for enzyme-like catalysis without the need for metal-based systems and toxic H2O2. We envisage our approaches to significantly expand the repertoire of supramolecular materials for enzyme activity regulation.