## 1 Introduction  
Exosomes are extracellular vesicles that are 30-150 nm in size; they are derived from intracellular multivesicular bodies and secreted by all cells and are present in body fluids [1, 2]. They contain various biomolecules including proteins, lipids, and nucleic acids (mRNA and miRNA), and specifically express membrane proteins of the tetraspanin family (CD9, CD63, CD81, etc.) [3, 4]. These biological characteristics of exosomes play important roles not only in normal physiological processes but also in the development and progression of diseases.  
Exosomes are present in various body fluids such as blood, urine, and saliva, and their composition and quantity change in several diseases including cancer, neurodegenerative disorders, and cardiovascular diseases [5,6]. According to the World Health Organization (WHO), cardiovascular diseases are responsible for approximately 17.9 million deaths annually, cancers are responsible for about 10 million deaths, and neurodegenerative diseases such as Alzheimer's disease affect over 55 million people worldwide. Therefore, exosomes hold great potential as non-invasive diagnostic biomarkers for liquid biopsy [7]. Additionally, exosomes are gaining attention as potential drug delivery vehicles due to their excellent biocompatibility and high cell membrane permeability [8]. Recently, research on therapeutic applications of stem cell-derived exosomes has also been actively conducted [9,10].  
However, the development of efficient isolation and concentration techniques must precede the clinical utilization of exosomes. The currently most widely used ultracentrifugation method has limitations such as being time-consuming, requiring expensive equipment, and yielding low recovery rates [11,12]. Size exclusion chromatography and immunoaffinity-based methods also have disadvantages including limited throughput or high costs [13]. Therefore, to use exosomes as markers for early diagnosis, the development of rapid, economical, and efficient exosome concentration techniques from large sample volumes is required.  
Recently, the polyphenic compound EGCG ((\(-\))-epigallocatechin-3-gallate) has gained attention as a new approach for exosome isolation [14]. EGCG, a major component of green tea that contains catechol and gallol functional groups, is known to strongly interact with biomolecules [15]. In particular, it has the characteristic of aggregating exosomes by binding to phospholipids in the exosome membrane. It is being evaluated as a novel approach that can overcome the limitations of conventional ultracentrifugation or immunoaffinity methods [16, 17, 18]. Additionally, the EGCG-based isolation method is simple, economical, and capable of isolating exosomes with high yield, making it promising for clinical diagnostic applications [19].  
In this study, we developed a composite material by combining EGCG with magnetic particles for application in automated systems [20]. Using this approach, we present a novel automated extraction method that can efficiently and rapidly isolate and concentrate exosomes from various biofluids including plasma, serum, urine, and saliva. Furthermore, we established an automated extraction method that integrates the typical two-step process of exosome isolation followed by protein extraction into a single step, enabling the entire process, from exosome isolation to protein extraction, to be performed directly from samples. Finally, along with the characterization of the isolated exosomes, we evaluated their potential as biomarkers for cancer diagnosis [21].