Metal nanoparticles (mNPs) also have strong interactions with light to generate localized SPR (LSPR) that leads to unique optical properties suitable for bioanalytical applications in various fields. Ultra small metal nanoclusters (mNCs) (i.e. < 2 nm with several to a few hundreds of metal atoms) have strong quantum confinement in the sub-2 nm size regime, thus exhibit unique molecular-like properties, such as strong fluorescence. I will present our contribution to this field, include (1) synthesis of anisotropic mNPs [1, 2], (2) coupling complementary sensing materials for bioassay development for a wide range of analytes (including protein [3], DNA [4], drug [5], pesticides, bacteria cells [6] etc), (3) mNPs embedded paper sensors for food/environmental monitoring, and (4) drug screening using mNCs [7]. Through these work, we have introduced novel analytical concepts of inverse sensitivity (for circulating DNA [8]) and synthesis-cum-sensing strategies (for drug screening [7] and UV-exposure detection [9]).