Photoactivated nanomotors via aggregation induced emission for enhanced phototherapy

Abstract

Aggregation-induced emission (AIE) has, since its discovery, become a valuable tool in the field of nanoscience. AIEgenic molecules, which display highly stable fluorescence in an assembled state, have applications in various biomedical fields—including photodynamic therapy. Engineering structure-inherent, AIEgenic nanomaterials with motile properties is, however, still an unexplored frontier in the evolution of this potent technology. Here, we present phototactic/phototherapeutic nanomotors where biodegradable block copolymers decorated with AIE motifs can transduce radiant energy into motion and enhance thermophoretic motility driven by an asymmetric Au nanoshell. The hybrid nanomotors can harness two photon near-infrared radiation, triggering autonomous propulsion and simultaneous phototherapeutic generation of reactive oxygen species. The potential of these nanomotors to be applied in photodynamic therapy is demonstrated in vitro, where near-infrared light directed motion and reactive oxygen species induction synergistically enhance efficacy with a high level of spatial control.

A Practical Guide to Analyzing and Reporting the Movement of Nanoscale Swimmers

“…These concerns are not hypothetical, but are already widespread in the nanoswimmer literature. By surveying 40+ recent literature reports of nanoswimmers, we see reoccurring inconsistencies that include blurry, drifting trajectories captured by optical microscopes, 58,60,61,65,68,73,79,88,92 inappropriate speed calculations and fitting of mean square displacement, 57,61,68,[71][72][73][74][75]77,79,82,83,89 and lack of proper and complete control experiments. 68,70,72,89 These inconsistencies are often accompanied by other issues: an incomplete reporting of experimental details, a casual discussion of the propulsion mechanism of a nanoswimmer, and sometimes even a lack of supporting videos that confirm self-propulsion.…”

“…In particular, we focus on the calculation of the mean squared displacement (MSD) as a way of quantifying nanoswimmer movement, because it is the most common method in the literature and where most misinterpretations come from. Visualization of nanoswimmers is typically performed in a literature report using an optical microscope (such as ordinary optical microscopy, 60,62-64,66,68,73,74,76,78,80-84,86,87,89,94 confocal microscopy, 58,65,75 or a specialized commercial setup such as a Nanosight 58,61,64,67,70,79,85,88,90,92 ) for nanoswimmers with 100 nm or larger dimensions. In the case of even smaller nanoswimmers, optical microscopy fails to capture their movement.…”

“…Although a parabolic MSD for a large microswimmer makes the extraction of V straightforward, seeing a parabola on the MSD plot of a nanoswimmer is alarming and not expected. The most likely source for such an anomaly is the presence of convective drift, 58,60,61,65,68,73,79,88,92 which could arise from a number of possible sources: an uneven stage, leaks in containment, growth and collapse of bubbles, disturbance to the fluid from adding solutes or solvents, to name a few. Difficult to completely eliminate, drift collectively moves all nanoswimmers in the field of view in the same direction and as a result superimposes a directional force on a diffusive nanoswimmer, rendering its entire MSD plot parabolic, even for ∆t>>τr.…”

Polymeric Micro/Nanomotors and Their Biomedical Applications

“…The modification by AuNSs was essential to the photomechanical poration of cell membrane as it enabled conversion from optical energy into heat under near-infrared light and generated adequate force for the nanomotor to puncture the cell membrane at the attaching point. Similarly, a new class of Au-coated polymersomes with excellent motility and cell penetration competence was fabricated by Cao et al [58] The nanomotors were made up of gold and functionalized-poly(ethylene glycol)poly(trimethylene carbonate) (PEG-PTMC) copolymers. Incorporation of an asymmetric Au layer endowed photoinduced motility, while introduction of tetraphenylethylene and dicyanovinyl moieties (TPEDC) brought the copolymers aggregation-induced emission (AIE) property and reactive oxygen species (ROS) production ability.…”

“…B) Phototaxis of AIE/Au polymer nanomotors via TP-NIR-induced thermophoresis and their enhanced cellular interactions and uptake (via percolation) alongside phototherapeutic ROS generation for highly localized cell toxicity. Reproduced with permission [58]. Copyright 2021, Springer Nature.…”