Provided herein are signal activatable molecular constructs for delivery of molecules and related components, compositions, methods, and systems, having a 17 to 30 bp targeting domain duplex RNA, at least one protection strand having a protection segment and linker segment and a sensor strand having a displacement segment and a toehold segment, in which in an inactive conformation the protection segment and the displacement segment form a sensor domain duplex polynucleotide covalently attached to the targeting domain and presenting the toehold segment for binding to a signal molecule. In an active conformation the sensor strand is bound to the signal molecule and is detached from the at least one protection strand and from the targeting domain; and the targeting domain attaches the at least one protection strand in a configuration allowing processing by Dicer and/or an Argonaute enzyme.