**1. Introduction**

Liver fibrosis is an important pathological and repair process in chronic liver disease, which is caused by chronic viral hepatitis, alcohol, and non-alcoholic steatohepatitis (NASH), and autoimmune liver disease [1–3]. It has been reported that liver diseases caused 4.6% of all deaths in the Asia-Pacific region, 2.7% in the USA, and 2.1% in Europe in 2015. The Asia-Pacific region holds more than half of the global population and accounted for 62.6% of all deaths due to liver diseases globally in 2015. Chronic hepatitis B virus (HBV) infection caused more than half of the deaths due to cirrhosis and other chronic liver diseases, followed by alcohol consumption, non-alcoholic fatty liver disease, and chronic infection with hepatitis C virus [4]. With persistent damage, live fibrosis develops into cirrhosis and, even to hepatocellular carcinoma, together with a series of complications, including hepatic encephalopathy, hepatic failure, and portal hypertension [5,6].

Liver fibrosis is currently diagnosed based on ultrasound imaging and blood testing, both of which lack precision [7]. Chemical drugs [8], Chinese herbalmedicines [9], andmonoclonal antibodies [10] are also being developed for the treatment of liver fibrosis. These approaches aim to remove injurious stimuli, suppress hepatic inflammation, down regulate hepatic stellate cell (HSC) activation, and promote matrix degradation [11]. However, these approaches exhibit limited therapeutic efficiency and have side effects. Therapeutic methods with enhanced therapeutic efficiency and targeted capabilities need to be developed. Precise diagnostic methods are also needed to monitor the progression of the disease.

Nanomedicine involves the design and application of nanoparticles (NPs) in the diagnosis and treatment of diseases [12–14]. As an important area of nanotechnology research, nanomedicine has greatly contributed to biomedicine in recent decades. Finely designed nanostructures have been fabricated as effective therapeutic agents for liver fibrosis with specific site-targeting abilities [15–17]. Nanostructures have also been developed as nanoagents for contrast enhancement or nanoprobes for the diagnosis of liver fibrosis [18]. Numerous inorganic or organic NPs have thus far been extensively investigated for the diagnosis and treatment of liver fibrosis, including metal oxide NPs [18], metal NPs [19], lipid NPs [20], polymer NPs [21], and protein NPs [22]. The various composition, controllable shape, size, and modifiable surface properties of NPs provide to them superior advantages, including controlled drug release, cell-tissue gap penetration, high contrast, prolonged duration in the bloodstream, improvement of the pharmacokinetics of drugs, and reduction of toxic side effects [23]. A greater significance of such systems is that they allow the integration of diagnosis and therapy in one nanoplatform [24].

The current review summarizes potential targets and the application of emerging nanomedicine systems for liver fibrosis diagnosis and therapy, including liposomes, polymer NPs, protein NPs, inorganic NPs, and hybrid NPs. Major research gaps, challenges, and coping strategies for the treatment of liver fibrosis by using nanomedicine are also discussed.
