It is a discovery to realize that hydrogen gas is generated when an electric current is passed through water. It becomes a patentable invention when that discovery is harnessed in a method for the production and collection of hydrogen gas from water. It is a discovery to observe and characterize a tissue response to a subcutaneous implant. It is an invention to include in the implant a substance which favorably influences such a tissue response to affect drug release from the implant. Your invention must be different from that which already is publicly known or available.
Inventions often seem obvious in hindsight.
An invention which solves a problem probably is not obvious if others attempted to solve the problem but failed. A good case can be made if your invention yields surprising, unexpected results. Factors happening years after your invention also can influence the determination of nonobviousness, such as the commercial success of the invention or copying of the invention by others. Self-censoring can cause you to lose valuable rights. Seek help from your institution's licensing office to assess nonobviousness.