In this paper, we present a silver-enhancement technique for self-assembling radio-frequency (RF) antennas and demonstrate its application for remote biosensing. When target analytes or pathogens are present in a sample the silverenhancement process self-assembles a chain of micro-monopole antennas. As the size of the silver-enhanced particles grows, the chain of micro-antenna segments bridge together to complete a macro-antenna structure. The change in the electrical impedance across the bridge modulates the reflection properties of the antenna at a desired frequency. In this paper we have used this principle to model, optimize and design a ratiometric mode 915 MHz radio-frequency identification (RFID) based biosensor which uses relative received signal strength indicator (RSSI) to measure and detect different concentration levels of target analytes. We have validated the proof-of-concept for detecting two types of analytes: (a) IgG in rabbit serum at concentration levels ranging from 20 ng to 60 ng; and (b) moisture in a sample at volumes ranging from 5µl to 40µl. A significant advantage of the proposed biosensor is that the concentration level of target analytes or pathogens can be remotely interrogated in a concealed, packaged or in a bio-hazardous environment, where direct electrical or optical measurement is considered to be impractical.