– Gouri Patil
Researchers from the Departments of Inorganic & Physical Chemistry and Organic Chemistry at IISc have synthesised molecular architectures that can kill pathogenic bacteria in water, including the infamous methicillin-resistant Staphylococcus aureus (MRSA). They fashioned these molecules to mimic enzymes – proteins found in living organisms regulating the rate of chemical reactions – using the principles of supramolecular chemistry, which deals with how molecules assemble spatially, and the intermolecular forces responsible for their organisation.
In one of their studies, the researchers designed a “molecular cage” called PMB1 via self-assembly of abenzothiadiazole-based ligand and platinum-based units. The benzothiadiazole unit is a photosensitiser, which absorbs light efficiently and produces reactive oxygen species that disrupt the bacterial cell membrane. The positively charged PMB1 cage also enhances the adhesion of the bacteria to the cage and damages the bacterial cell membrane.
The authors believe that this is the first time a water-soluble molecular cage antibacterial agent has been designed where a single entity utilises two pathways to degrade bacteria — both in the presence and absence of light.
Though these nano-sized supramolecular assemblies are being used in applications like catalysis, smart materials, drug delivery, light-harvesting and sensors, they have rarely been employed in disinfecting water. Therefore, this work could help develop more such antibacterial agents in the future.
The team, in a related study, proposes a water-soluble nanozyme cage structure consisting of benzothiadiazole-based and palladium-based units. Nanozymes are nanomaterials mimicking the properties of the natural enzymes. The molecular cage here imitates the activity of an enzyme called ‘oxidase’ and generates reactive oxygen species due to the light absorption by benzothiadiazole unit. These free radicals kill the bacteria present in water.
Nanozymes have an advantage over natural enzymes because they are more stable and are easier to synthesise on a largescale. Hence, they have found potential applications in biochemical tests, biosensors and therapeutics.
Soumalya Bhattacharyya, Mangili Venkateswarulu, Jagabandhu Sahoo, Ennio Zangrando, Mrinmoy De, and Partha Sarathi Mukherjee, Self-Assembled PtII8 Metallosupramolecular Tubular Cage as Dual Warhead Antibacterial Agent in Water, Inorganic Chemistry, 2020, 59, 17, 12690–12699.
Soumalya Bhattacharyya, Sk Rajab Ali, Mangili Venkateswarulu, Prodip Howlader, Ennio Zangrando, Mrinmoy De, and Partha Sarathi Mukherjee, Self-Assembled Pd12 Coordination Cage as Photoregulated Oxidase-Like Nanozyme, Journal of the American Chemical Society, 2020, 142, 44, 18981–18989