Nanoengineered Polyphenol-Quantum Dot Conjugates Inhibit Biofilm Protein-Aβ42 Heterotypic Fibrillogenesis, Restore Synaptic Transmission, and Suppress Apoptosis in Alzheimer’s Disease

The gut microbiota influences neurodegenerative disease progression, including Alzheimer's disease (AD), through microbial metabolites like amyloids in bacterial biofilms, such as the curli protein in Eshcherichia coli biofilm. In this context, the study focuses on two key aspects, namely, (i) how cross-kingdom bacterial biofilm proteins accelerate Aβ42 aggregation and induce neurotoxicity and (ii) whether a nanochaperone with hydrophobic sheets and hydrophilic polyphenolic moieties could inhibit cross-seeded aggregation. Considering this, we chemically synthesized and further characterized gallic acid-conjugated molybdenum disulfide quantum dots (GA@MoS₂ QDs, ∼9.6 ± 4.2 nm) using spectroscopy and microscopy techniques, which showed ∼1.84-fold reduction in E. coli biofilm thickness, indicating interaction with biofilm components. The presence of the curli protein in E. coli was confirmed by dot blot and MALDI-TOF studies. Subsequent biophysical studies showed that isolated E. coli biofilm protein accelerated Aβ42 aggregation (heterotypic) by ∼6.76-fold, while GA@MoS₂ QDs reduced this heterotypic aggregation by ∼9.49-fold reduction in Aβ42+ECBFP fluorescence relative to Aβ42 aggregates. In vitro studies with SH-SY5Y cells showed that heterotypic protein aggregation led to increased ROS production, intracellular calcium influx, and apoptosis induction, which were mitigated by GA@MoS₂ QDs. The neuroprotective effect of GA@MoS₂ QDs was also studied on Caenorhabditis elegans. Overall, the present studies suggested that the bacterial amyloid proteins may play a crucial role in Aβ42 aggregation, suggesting that targeting coaggregation could provide a novel therapeutic approach for the treatment of early onset AD.