This invention is generally related to a biocompatible sensor for detecting/measuring an analyte of interest in a body fluid and a method for making the biocompatible sensor. A biocompatible sensor of the invention comprises, consists essentially, or consists of a reflection hologram therein or thereon, wherein the reflection hologram is produced in a crosslinkable and/or polymerizable fluid material. The polymer matrix contains a molecular sensing moiety which interacts or reacts with an analyte of interest to provide an optical signal which is indicative of a change in one or more optical properties of the reflection hologram.