Ultrasensitive biodetection and sonodynamic therapy for pathogenic agents based on lanthanide-doped nanomaterials

Abstract

Outbreaks of pathogenic organisms including viruses and bacteria provide a formidable challenge to public healthcare systems. The early detection of infectious pathogens and the subsequent therapy are essential for preventing propagation. For the biodetection assay, FRET has been commonly used for biosensing as the luminescent intensity of fluorophore varies with the approach or separation of the energy pairs. Therefore, FRET biodetection assay based on upconversion nanoparticles (UCNPs) and gold nanoparticles is developed for the detection of viruses in this thesis. As for the therapy of the pathogens, sonodynamic therapy (SDT) has tremendous potential in preventing multidrug-resistant bacterial infections considering it is non-invasive and requires no antibiotic dependence, which can effectively solve the problem of bacterial resistance. Hence, an antibacterial application is conducted both in vitro and in vivo using Bi2WO6 nanosheets as sonosensitizer for sonodynamic therapy. In the first part of the thesis, an ultrasensitive plasmon-enhanced fluorescence resonance energy transfer (FRET) biosensor based on core-shell upconversion nanoparticle (csUCNP) and gold nanoparticle (AuNP) for accurate detection of SARS-CoV-2 viral RNA is presented. In this biodetection assay, the Tm3+/Er3+ co-doped csUCNP NaGdF4:Yb/Tm@NaYF4:Yb/Er acts as an energy donor and AuNP serves as an energy acceptor. The upconversion emission of Tm3+ and the design of the core-shell structure led to a simultaneous surface plasmon effect of AuNP. The localized surface plasmon resonance (LSPR) arising from collective oscillations of free electrons significantly enhanced FRET efficiency between Er3+ and AuNP. The as-prepared biosensor obtained a limit of detection (LOD) as low as 750 aM, indicating that the integration of FRET and surface plasmon into one biodetection assay significantly boosted the sensitivity of the biosensor. In addition, samples extracted from clinical samples are also utilized to validate the effectiveness of the biosensor. Therefore, this innovative plasmon-enhanced FRET biosensor based on Tm3+/Er3+ co-doped csUCNP may pave the way for rapid and accurate biodetection applications. In the second section, 2-dimensional (2D) Bi2WO6 nanosheets (BWO NSs) were synthesized through the hydrothermal method as the sonosensitizer, and varying concentrations of Ytterbium ions were doped (BWO-x%Yb, x=1,2,5,10,20) to improve the sonodynamic activity. The Yb ions were verified to occupy the position of Bi by both calculation and XRD characterization. The reactive oxygen species (ROS) produced by BWO-x%Yb under ultrasound (US) irradiation were examined. It was shown that at a concentration of 10% Yb, the nanosheets generated the highest amount of ROS. ROS has the ability to cause oxidation of lipids in the bacterial cell membrane, resulting in the deterioration of membrane integrity. This can result in the release of intracellular substances and ultimately lead to cellular demise. In vitro experiments have verified that the BWO-10%Yb NSs are capable of eliminating both Methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli) through ROS generation. The RNA sequencing transcriptome analysis was conducted with MRSA to acquire further understanding of the biological mechanism of the sonodynamic antimicrobial activities of BWO-10%Yb NSs. In the third part of the thesis, the BWO-10%Yb NSs are combined with polyvinyl alcohol (PVA) hydrogel to improve biocapacity for further in vivo antibacterial applications. The resulting BWO-Yb-PVA hydrogel also showed remarkable efficacy in killing bacteria. In the in vivo test, the BWO-Yb-PVA hydrogel expedited the healing process of wounds infected with MRSA. Therefore, our work highlights a novel sonosensitizer for enhanced sonodynamic bacteria elimination and wound healing.