Search

DNA origami nanostructures are promising carries for drug delivery applications. However, their limited stability under relevant conditions often presents a challenge. Herein, the structural stability of DNA origami nanostructures is investigated in a setting compatible with their application in photodynamic therapy (PDT). To this end, DNA origami triangles and six‐helix bundles (6HBs) are loaded with the clinically tested photosensitizer methylene blue, which upon irradiation with red light generates reactive oxygen species (ROS) that attack the DNA origami nanostructures. ROS‐induced structural damage is observed to depend on the ionic composition of the surrounding medium and becomes more severe at low ionic strength. Mg2+ ions can efficiently protect the DNA origami nanostructures from ROS‐induced damage and may even heal some of the damage obtained under Mg2+‐free conditions when added after irradiation. Finally, the employed DNA origami 6HBs are more resistant toward ROS‐induced structural damage than the triangles, which is attributed to their markedly different mechanical properties. These results thus provide some fundamental insights into the stabilizing role of DNA origami superstructure that may guide the selection or design of DNA origami nanocarriers with optimized stability for their application in PDT. [ABSTRACT FROM AUTHOR]

DNA origami nanostructures (DONs) are able to scavenge reactive oxygen species (ROS) and their scavenging efficiency toward ROS radicals was shown to be comparable to that of genomic DNA. Herein, we demonstrate that DONs are highly efficient singlet oxygen quenchers outperforming double‐stranded (ds) DNA by several orders of magnitude. To this end, a ROS mixture rich in singlet oxygen is generated by light irradiation of the photosensitizer methylene blue and its cytotoxic effect on Escherichia coli cells is quantified in the presence and absence of DONs. DONs are found to be vastly superior to dsDNA in protecting the bacteria from ROS‐induced damage and even surpass established ROS scavengers. At a concentration of 15 nM, DONs are about 50 000 times more efficient ROS scavengers than dsDNA at an equivalent concentration. This is attributed to the dominant role of singlet oxygen, which has a long diffusion length and reacts specifically with guanine. The dense packing of the available guanines into the small volume of the DON increases the overall quenching probability compared to a linear dsDNA with the same number of base pairs. DONs thus have great potential to alleviate oxidative stress caused by singlet oxygen in diverse therapeutic settings. [ABSTRACT FROM AUTHOR]

Photodynamic therapy (PDT) using TiO2 nanoparticles has become an important alternative treatment for different types of cancer due to their high photocatalytic activity and high absorption of UV‐A light. To potentiate this treatment, we have coated commercial glass plates with TiO2 nanoparticles prepared by the sol–gel method (TiO2‐m), which exhibit a remarkable selectivity for the irreversible trapping of cancer cells. The physicochemical properties of the deposited TiO2‐m nanoparticle coatings have been characterized by a number of complementary surface‐analytical techniques and their interaction with leukemia and healthy blood cells were investigated. Scanning electron and atomic force microscopy verify the formation of a compact layer of TiO2‐m nanoparticles. The particles are predominantly in the anatase phase and have hydroxyl‐terminated surfaces as revealed by Raman, X‐ray photoelectron, and infrared spectroscopy, as well as X‐ray diffraction. We find that lymphoblastic leukemia cells adhere to the TiO2‐m coating and undergo amoeboid‐like migration, whereas lymphocytic cells show distinctly weaker interactions with the coating. This evidences the potential of this nanomaterial coating to selectively trap cancer cells and renders it a promising candidate for the development of future prototypes of PDT devices for the treatment of leukemia and other types of cancers with non‐adherent cells. [ABSTRACT FROM AUTHOR]

Coatings of modified TiO2 nanoparticles (TiO2-m) have been shown to effectively and selectively trap non-adherent cancer cells, with an enormous potential for applications in photodynamic therapy (PDT). Leukemia cells have a remarkable affinity for TiO2-m coatings, adhering to the surface by membrane structures and exhibiting morphologic characteristics of amoeboid locomotion. However, the details of the cell–substrate interaction induced by the TiO2-m coating remain elusive. With the aim to obtain a better understanding of this phenomenon, leukemia cell adhesion to such coatings was characterized by atomic force microscopy (AFM) for short contact times up to 60 min. The cell and membrane morphological parameters mean cell height, contact area, cell volume, and membrane roughness were determined at different contact times. These results reveal cell expansion and contraction phases occurring during the initial stage of adhesion. Subsequently, the leukemic cells reach what appears to be a new resting state, characterized by pinning of the cell membrane by TiO2-m nanoparticle aggregates protruding from the coating surface. [ABSTRACT FROM AUTHOR]

This article explores the use of DNA origami nanostructures in scavenging singlet oxygen and other reactive oxygen species in antimicrobial photodynamic therapy. The study finds that while double-stranded DNA is not effective at quenching singlet oxygen, folding it into DNA origami nanostructures significantly increases its efficiency. This research suggests that DNA origami nanostructures have the potential to reduce oxidative stress caused by singlet oxygen in various therapeutic applications. The full details of the study can be found in the Research Article by A. Keller and co-workers. [Extracted from the article]

Photodynamic therapy (PDT) has become an important alternative for the treatment of different types of cancer, due to its great advantages over conventional methods. In this field, TiO2 nanoparticles are one of the most widely studied photosensitizers due to their high photocatalytic activity, high absorption of UVA light and high biocompatibility. Although there are several successful studies related to PDT treatment, using TiO2 nanoparticles, for different types of adherent cancer cells, there are few reports of PDT applied to non-adherent cancer cells, due to the challenges related to blood volume and light penetration. To address this challenge, modified TiO2 nanoparticles (TiO2-m) were deposited on glass substrates to study the cytotoxic effect of PDT on Molt4, non-adherent cells, using these coatings. The shaping of uniformed coatings on substrates was proved by standard deviation of transmittance in the UVA range at different points. Different experimental PDT tests of Molt4 cells on TiO2-m coatings were performed and the treatment cytotoxic effect was evaluated by LDH concentration. The results demonstrated the possibility of generating cytotoxic effect on non-adherent cancer cells with only 20 min of contact and 40 min of UVA radiation. This result is the first step for the possible development of new methodologies in the application of PDT on non-adherent cells using TiO2-m coatings. [ABSTRACT FROM AUTHOR]