Probing endogenous molecular profiles is of fundamental importance to understand cellular function and processes. Despite the promise of programmable nucleicâacidâbased aptasensors across the breadth of biomolecular detection, targetâresponsive aptasensors enabling intracellular detection are as of yet infrequently realized. Several challenges remain, including the difficulties in quantification/normalization of quencherâbased intensiometric signals, stability issues of the probe architecture, and complex sensor operations often necessitating extensive structural modeling. Here, the biomimetic crystallizationâempowered selfâassembly of a tumorâtargetable DNAâinorganic hybrid nanocomposite aptasensor is presented, which enables Förster resonance energy transfer (FRET)âbased quantitative interpretation of changes in the cellular target abundance. Leveraging the design programmability and highâthroughput fabrication of rolling circle amplificationâdriven DNA nanoarchitecture, this designer platform offers a method to selfâassemble a robust nanosensor from a multifunctionalityâencoded template that includes a cellâtargeting aptamer, a ratiometric aptasensor, and a cholesterolâdecorating element. Taking prostate cancer cells and intracellular adenosine triphosphate molecules as a model system, a synergistic effect in the targeted delivery by cholesterol and aptamers, and the feasibility of quantitative intracellular aptasensing are demonstrated. It is envisioned that this approach provides a highly generalizable strategy across wideâranging target systems toward a biologically deliverable nanosensor that enables quantitative monitoring of the abundance of endogenous biomolecules.