## 1 Introduction  
Personalized medicine is known as tailor-made medical care and healthy life system for each person by providing appropriate treatment and medication. In order to realize these personalized medication systems, the development of sensing technologies, which can detect detailed personal health status and information by monitoring various medical sensors, is essential. Single-molecule electrical measurement using nanostructure integrated devices, called \"nanodevice\", is one of the candidates to addressing the issues in this realization of personalized medicine (Figure 1). Compared to conventional analytical techniques, there are several advantages of single-molecule electrical measurements using nanodevices: high sensitivity, which enables early diagnosis and monitoring, the simplicity and compactness of the measurement system, which enables easy-portability in field works and research; and the possibility of the integration of various functions and multiple sensors such as separation and purification. Nanopore based single molecule measurement is one of the most attractive single molecule measurements using nanodevices [1; 2]. The detection principle of nanopore based single molecule measurement methods is the same as the Coulter counter detection principle. The principles are herein briefly described. The nanopore device has two solution chambers separated by a membrane with a single nanopore, and the chambers are filled with an electrolyte solution. When a single molecule/particle flows into the nanopore, the electrical conductivity of the electrolyte solution in the pore decreases due to the excluded volume of the particle, resulting in a decrease in ionic current. From the magnitude of the electrical signal of the current decrements during the pore translocation, it is possible to analyze physical quantity such as the volume of the sample. Nanopipette based single molecule measurement is also one of the important methods for single molecule electrical measurements. A nanopipette device is defined as a pipette with a very fine tip that has a nanoscale opening. Similar to nanopore, the detection principle of nanopipettes is done by blockage of the ionic current through the pipette by the passage of the target samples. Nanopipettes have been widely applied from cells to ions due to their ease of preparation, which allows the size of the pipette to be controlled according to the target sample [3; 4; 5]. Nanogap based single molecule measurement is also used for nanodevices for single molecule electrical measurement [6]. The measurement principle is to measure the electrical conductivity of individual molecules by using around 1 nm gaps, which are formed by using a mechanically controllable or electrical break junction method. Sample molecules enter and translocate through the nanogap-electrodes, ensuring the facilitation of the tunneling current via the nucleotide molecules. The tunnel-current intensity is related to the molecular energy level so that signal intensity represents the electrical conductivity of individual molecules. This method enables the analysis of chemical bonds, steric structure, molecular interactions between target molecules and gold electrodes, and the polarity of sample molecules. With the recent development of the nanodevice fabrication by semiconductor mass-production technique, the fabrication cost of the devices has rapidly decreased so that the nanodevice sensors are able to be utilized for biological/medical applications. In this review, we introduce the cutting-edge medical applications that have been made possible by using nanodevices. Figure 1: Schematics of single-molecule detection by nanodevices for biological/medical application. In personalized medicine, non-invasive liquid biopsy (urine, blood, etc.) is expected to be used for the application of sampling. The samples include miRNAs and proteins released from the liposomes of cells, as well as the virus itself in case of infection.