Daphnia magna uptake and excretion of luminescence-labelled polystyrene nanoparticle as visualized by high sensitivity real-time optical imaging.

The environmental and ecological consequences of nanoplastics (NPs) draw increasing research interests and social concerns. However, the in situ and real-time detection of NPs from living organisms and transferring media remains as a major technical obstacle for scientific investigation. Herein we report a novel time-gated imaging (TGI) strategy capable of real-time visualizing the intake of NPs by an individual living organism, which is based on the polystyrene NPs labelled with lanthanide up-conversion luminescence. The limit of detection (LOD) of the TGI apparatus was 600 pg (SNR = 3) in a field of view of 2.4 × 3.8 mm. Taking Daphnia magna as the aquatic model, we investigated the dynamics of uptake and accumulation of NPs (500 µg/L) for 24 h, and the subsequent excretion process (in clean medium) for 48 h, and quantitively analyzed the distribution and the overall mass of NPs deposited in D. magna. The uptake of NPs via filter-feeding occurred in a few minutes, whereas a longer accumulation was found, in a timescale of several hours. And similar behaviors (bi-phase elimination) were also seen in the excretion, indicating the migration of NPs into the circulatory system. The average mass of NPs accumulated in an individual D. magna was ∼12 ng after 24 h exposure, indicating that D. magna as a filter feeder tends to retain NPs. The observed NPs accumulation in D. magna exemplifies the potential risk of aquatic ecosystem on exposure to NP contamination.

Spatial effects of photosensitization on morphology of giant unilamellar vesicles.

Singlet oxygen (1O2) formed through photosensitization may initiate oxidative destruction of biomembranes, however, the influence from the spatial organization of photosensitizers (PS) relative to membranes remains unclear. To clarify this issue, we loaded riboflavin 5'-(dihydrogen phosphate) monosodium (FMN-Na) as a hydrophilic PS into the lumen of halloysite nanotubes (HNTs), and attached the nanoassemblies (FMN-Na@HNTs), via Pickering effects, to the outer surfaces of giant unilamellar vesicles (GUVs) of phospholipids. We also prepared GUVs dopped with lumiflavin (LF) as a lipophilic PS having a 1O2 quantum yield comparable to FMN-Na. FMN-Na capsulated in HNT was characterized by a longer triplet excited state lifetime (12.1 µs) compared to FMN-Na free in solution (7.5 µs), and FMN-Na in both forms efficiently generated 1O2 upon illumination. The spatio-effects of PS on the photosensitized morphological changes of membranes were studied using conventional optical microscopy by monitoring GUV morphological changes. Upon light exposure (400-440 nm), the GUVs attached with FMN-Na@HNT merely experienced membrane deformation starting from the original spherical shape, ascribed to Type II photosensitization with 1O2 as oxidant. In contrast, photooxidation of LF dopped GUVs mainly led to membrane coarsening and budding assigned to Type I photosensitization. The spatial effects of PS on photosensitized morphological changes were related to the different lipid oxidation products generated through Type I and Type II photosensitized lipid oxidation.

Naturally occurring nanotube with surface modification as biocompatible, target-specific nanocarrier for cancer phototherapy.

Phototherapy has drawn increasing attention including the use of nanocarriers with high drug loading capacity and delivery efficacy for target-specific therapy. We have made use of naturally-occurring halloysite nanotubes (HNTs) to build a biomimetic nanocarrier platform for target-specific delivery of phototherapeutic agents. The HNTs were decorated with poly(sodium-p-styrenesulfonate) (PSS) to enhance the biocompatibility, and were further functionalized by lumen loading the type-II photosensitizer indocyanine green (ICG). The HNT-PSS-ICG nanocarrier, without further tethering targeting groups, was shown to associate with the membrane of giant unilamellar vesicles (GUVs) via Pickering effects. Application of HNT-PSS-ICG nanocarrier to human breast cancer cells gave rise to a cell mortality as high as 95%. The HNT-PSS-ICG nanocarrier was further coated with MDA-MB-436 cell membranes to endow it with targeting therapy performance against breast cancer, which was confirmed by in vivo experiments using breast cancer tumors in mice. The membrane-coated and biocompatible nanocarrier preferentially concentrated in the tumor tissue, and efficiently decreased the tumor volume by a combination of photodynamic and photothermal effects upon near-infrared light exposure. Our results demonstrate that the HNT-based nanocarrier by virtue of facial preparation and high loading capacity can be a promising candidate for membrane-targeting nanocarriers.