and this biotin-labeled target DNA is hybridized with the probe DNA immobilized on the disk (step 3). Subsequently, gold nanoparticles are bonded with the target via streptavidin conjugate (step 4). Silver is then deposited onto the gold “seed” (step 5) to increase the particle size from a few to several hundred nanometers. The amplification of fluorescence will be detected by the detection system in the CD drive. Signal receiving The detection system should be completed by the signal receiving component. There are roughly three types of systems which can be used for detecting. The first is Hardware and software modification, which means the CD/DVD drive should be modified and the software should also be developed at the same time. This type will cause superfluous labor and expenses, and may not be versatile in developing countries or indigenous areas. The second type is Software modification with standard hardware, which means that the detection can be achieved by developing customer software on platforms such as C++ without making any changes to hardware. The third is Standard hardware and existing software, which means that the detection can be realized simply by using the existing equipment. Manu Pallapa described a new protocol to read and quantify biotin–streptavidin binding assays with a standard optical drive by using a current CD-data analysis software (IsoBuster) successfully. The latter two types are both considerable when coming across different situations. No matter which type of detection system one uses, the reading method is an important factor. There are mainly two reading methods, which are AAS (acquired analog signals) and ERD (error reading detection). In the AAS method, to determine multianalytes on a DVD, the analog signals acquired directly from the photodiode of a CD/DVD drive correlate well with the optical density of the reaction products. The ERD method is based on the analysis of reading errors. It can use the same digital versatile disk and a standard DVD drive without any supplementary hardware. ERD In the ERD method, the position and level of the resulting reading error correspond to the physical location and the intensity of the bioassay signal, respectively. The errors are then compared with a perfectly recorded CD to identify the time when one certain error was read out. There are several free CD-quality diagnostic programs, such as PlexTools Professional, Kprobe, and CD-DVD Speed, which can be used to access the error-statistic information in a CD/DVD drive