## 1 Introduction  
Atherosclerosis (AS) is a common cardiovascular disease that seriously threatens human health [1]. The deposition of oxidised lipoproteins in the arterial wall promotes macrophage aggregation [2] and foam cell formation [3], a process that leads to the accumulation of reactive oxygen species (ROS) [4]. ROS also exacerbate inflammation by inducing oxidative damage, DNA denaturation, and apoptosis [5]. This inflammation promotes the formation of vascular defects that can lead to bleeding, plaque, and thrombosis. When atherosclerotic plaques are present, these areas become slightly acidic [6], leading to macrophage apoptosis and aggregation, resulting in thrombus formation. Cardiovascular diseases caused by atherosclerosis are extremely dangerous to human health, and their incidence is increasing every year, making them the leading cause of death in China and even the world. Atherosclerosis is responsible for more than 75% of the disability and death from cardiovascular diseases in China, indicating that atherosclerosis has become one of the most serious factors endangering the health of Chinese citizens [7]. Therefore, early treatment of atherosclerosis is of great clinical importance. Hirudin (rH), a peptide extracted from the peripheral glands of leeches, is a safe natural anticoagulant with beneficial effects in the treatment of atherosclerosis due to its pharmacological effects, such as anticoagulation, antithrombotic, anti-inflammatory, endothelial cell protection and antifibrotic effects, without causing thrombocytopenia [8]. A promising class of anticoagulants, hirudins can be used to treat various thrombotic diseases [9], especially venous thrombosis and diffuse vascular coagulation. In addition, unlike most peptides, hirudin is highly permeable and stable, is not destroyed by trypsin and chymotrypsin, and does not decompose with slight changes in pH or temperature, so it can be taken orally, and the decomposed fragments also have anticoagulant effects; however, some special conditions, such as the simultaneous presence of strong alkalinity and high temperature, can lead to the irreversible inactivation of hirudin [10]. Traditional extraction methods for hirudin include water extraction and organic solvent extraction. The water extraction method involves crude extraction with 0.9% saline at four times the volume of the original hirudin solution, followed by the removal of large amounts of heteroproteins with 10-15% trichloroacetic acid [11]. The organic solvent extraction method is to use alcohol, acetone, etc., as the extraction solvent [12]. In recent years, leeches and Chinese patent medicines or compounded preparations containing leeches have been widely used in the clinical treatment of cardiovascular and cerebrovascular diseases. Nanotechnology can improve the bioavailability of drugs. By precisely controlling the size, drug loading, and composition of nanomaterial microparticles, it can provide a brand new idea for therapeutic development in AS. Artificially prepared drug-loaded nanoparticles have the advantages of drug solubilization, long half-life, fewer non-specific reactions, an active targeting effect, and multifunctionality as a whole, which suggest great potential in the direction of AS therapy [13; 14; 15; 16; 17; 18]. However, engineered nanoparticles suffer from immune clearance and difficulty in delivering the drug to the lesion. Erythrocytes are the most abundant cells in the blood. As a result of long-term natural selection, their unique biconcave disc-like morphology and cellular composition have enabled them to acquire excellent biological properties. Researchers have produced a variety of nanoparticles that mimic erythrocytes, which have been widely used in biomedical fields such as drug delivery, bioimaging, and tissue engineering [19]. Bowl-shaped particles are a common type of erythrocyte-like particle with a morphology of unidirectional concave structures with distinct directionality.