Polyhedral Oligomeric Silsesquioxane (POSS)-Based Cationic Conjugated Oligoelectrolyte/Porphyrin for Efficient Energy Transfer and Multiamplified Antimicrobial Activity

Abstract

Cationic quaternary ammonium (QA) groups and reactive oxygen species as two main approaches for antibacterial study have been intensively studied. Herein, we report a multifunctional antimicrobial agent (porphyrin-POSS-OPVE, PPO), which combines bacterial membrane intercalation, high density of local QA groups, efficient energy transfer, significantly reduced aggregation, and high water solubility into one single molecule. The light-harvesting PPO contains multiple donor-absorbing arms (oligo( p-phenylenevinylene) electrolytes, OPVEs) on its globular periphery and a central porphyrin acceptor in the core by using three-dimensional nanocages (polyhedral oligomeric silsesquioxanes, POSSs) as bridges. The antiaggregation ability of POSS and the highly efficient energy transfer from multiple OPVE arms to porphyrin could greatly amplify singlet oxygen generation in PPO. Particularly, OPVEs with QA terminal chains were able to intercalate into Escherichia coli membranes, which facilitated O diffusion and bacterial cell membrane disintegration by QA groups. The increased local cationic QA charges in OPVE arms can also enhance the biocidal activity of PPO. Benefiting from these satisfactory features, PPO exhibits multiamplified antibacterial efficacy under a very low concentration level and white light dose (400-700 nm, 6 mW·cm, 5 min, 1.8 J·cm) to Escherichia coli (8 μM) and Staphylococcus aureus (500 nM). Therefore, PPO shows great potential for photodynamic antimicrobial chemotherapy at a much lower irradiation light dose and photosensitizer concentration level compared to previous reports.

The Role of Polyhedral Oligomeric Silsesquioxanes in Optical Applications

“…Chen et al reported an energy transfer system based on a cationic conjugated oligoelectrolyte donor and porphyrin acceptor for use in photodynamic antimicrobial chemotherapy ( Figure ). [ 88 ] In this system, each porphyrin unit was functionalized with four POSS cages, which contained seven additional (oligo( p ‐phenylenevinylene) (OPVE) electrolyte donor groups, creating a large macromolecule with a porphyrin acceptor center and a POSS star‐like structure. In this example, the POSS was used to reduce the aggregation of the porphyrin sites but also to act as a highly functionalizable bridging group, which increased the local concentration of oligoelectrolyte groups, thus enhancing the solubility.…”

Precisely Defined Conjugated Oligoelectrolytes for Biosensing and Therapeutics

“…[159,174] Recently, Wang, Bao and co-workers designed a POSS-COE based porphyrin for efficient energy transfer from COE to porphyrin and achieved amplified antimicrobial activity. [175] However, the absorption peaks of those OPEs are around 326 nm to 355 nm. [176] Longer wavelength absorption would be desirable to achieve lower toxicity to mammalian cells and deeper tissue penetration.…”

Progress in the Synthesis of Bifunctionalized Polyhedral Oligomeric Silsesquioxane

“…Among these, the incorporation of polyhedral oligomeric silsesquioxane (POSS) has attracted attention because of its unique frame structure and the resulting chemical and physical properties, including high thermal properties [18][19][20], lower crystallinity [21], mechanical properties [22], oxidation resistance, and very good dielectric properties [23,24]. Hence, it has been widely used in preparing polymer hybrids and polymer composites in many areas, including optics [25], electronics, ionic liquids [26], mechanics [27], energy [28], environment [29], biology [30], smart coatings [31,32], fuel [33], solar cells [34], catalysts [35,36], sensors [37][38][39], light-emitting devices [40], and medicine [41][42][43][44].…”