Embodiments herein relate to compositions and methods for making and using aptamers, for example, DNA aptamers (DCEs) and/or RNA aptamers. In some embodiments, methods relate to making and amplifying target DCEs. In certain embodiments, methods for making capture elements or aptamers concern using a reporter moiety and signal reducing moiety prior to amplifying a target-specific capture element. In some embodiments, methods disclosed herein may be used to rapidly generate large quantities of aptamers such as DCEs directed to a particular target agent. Some embodiments relate to systems for performing automated generation of aptamers.