In this research, we describe novel optical sensors improved by the use of bacterial cellulose (BC) as a nano-based platform. The outstanding features of BC such as optical transparency, nano-fibers structure, porosity and abundant functional groups, make this natural biopolymer a promising substrate to create a unique type of optical biosensors. Importantly, the coupling of BC with advantageous nanomaterials (e.g., plasmonic nanoparticles and biomolecule) allows advancing multifunctional nanocomposites. Here, we prepared the plasmonic nanopaper with embedding plasmonic nanoparticles (e.g. Ag and Au nanoparticles) through an in-situ synthesis technique. It resulted in the formation of a nanocomposite that possessed plasmonic properties of the embedded nanoparticles, proved by its UV-vis absorbance spectra where the BC impregnated with AgNP or AuNP revealed a plasmonic peak at 470 and 530 nm, respectively. Considering the dependency of UV-vis absorbance spectra on the size of the plasmonic nanoparticles, the AgNP-BC was successfully employed to detect ammonia vapor. By being exposed to the ammonia vapor, the AgNP inside BC experienced a size reduction due to etching. Consequently, the nanopaper exhibited a color change from amber to light amber, and also, a reduction in the intensity of the plasmonic peak. The developed plasmonic nanopaper was also utilized to detect the meat and fish spoilage by altering its color. Given the fact that plasmonic nanoparticles have strong quenching properties and also, their application in absorbing energy transfer from a fluorophore, we proved that AuNP-BC showed this behavior. So, it has been used as a solid-based quencher to design a sensitive immunosensor for the direct detection of bacteria. Through this method, it was possible to recognize E. coli bacteria as low as 50 CFU/ml, directly and without further treatment. Hence, we were able to fabricate a solid-state sensor to detect volatiles and bacteria, that are versatile.