The geometry-dependent regulation of hepatic stellate cells by graphene oxide nanomaterials

Nanomaterials are widely used in biomedical applications such as drug delivery, bioimaging, and photothermal therapy. For example, graphene oxide (GO) nanomaterials are among the most popular drug delivery vehicles in treating liver diseases due to their tunable chemical/physical properties, and biocompatibility. However, it has been reported that nanomaterials tend to accumulate in livers. The biophysical impact of the accumulation in liver cells remains unclear, and it may cause the liver fibrosis in the long run. The activation of hepatic stellate cells (HSCs) is one of the key initial steps of liver fibrosis. In this paper, we explored the geometric effect (nanosheets vs. quantum dots) of GO nanomaterials on human HSCs, in terms of cell viability, fibrotic degree, mobility and regulation pathways. Our study showed that GO nanosheets could significantly reduce HSCs cell viability and mobility. The protein expression levels of TGFβRⅡ/Smad2/Smad3 decreased, corresponding to a trend of attenuating fibrotic degree. However, the expression level of α-SMA, a maker protein of fibrosis, increased and contradicted with the projection. Further investigation on mitochondria showed that GO nanosheets disrupted mitochondria membrane and membrane potentials. We found that while modulating fibrotic effect through the TGF-β pathway, GO nanosheets induced oxidative stress and activated HSCs through reactive oxygen species(ROS)pathway. This was confirmed by the decreased expression level of α-SMA after co-incubation of GO nanosheets and n-acetyl cysteine (NAC) with HSCs. GO quantum dots decreased α-SMA expression level at 100 mg/l, along with decrease in GAPDH expression level and constant expression level of β-actin. The correlation between GAPDH and α-SMA remains to be explored. Our study suggested that the biophysical impacts of GO nanomaterials on HSCs are geometry-dependent. Both GO nanosheets and quantum dots can be adapted for attenuating liver fibrosis with further investigation on mechanisms.