RARA and acute promyelocytic leukemia: A similar approach with an enzyme-free and label-free surface plasmon resonance (SPR) biosensing strategy was designed by Guo et al. The authors engineered a DNA self-assembly aptamer-based hydrogel with streptavidin (SA) encapsulation, followed by ML/RARα (promyelocytic leukemia, retinoic acid receptor alpha) targeting capture probes (Cp) immobilized on the chip-surface-engineered Cp-PML/RARα duplex.