Table 1.

Precise delivery and release of drugs by different multilayer hydrogels.

Drug Carriers	Drug Species	Release Pathways	Advantages	Reference
Poly(methacrylic acid)/poly(N-vinylpyrrolidone) multilayer hydrogel capsules	Nucleic acids	Ultrasound-triggered release	Higher effective loading capacity and controlled delivery of sensitive biomolecules	[53]
Poly(N-vinylcaprolactam) multilayer hydrogels	Sodium diclofenac	Increase in temperature	Multiple drug delivery	[54]
Chitosan multilayer hydrogel capsules	Doxorubicin	Adjustment of pH	Significant inhibition of the burst release and good biocompatibility,	[55]
Polycarboxymethyl-β-cyclodextrin (polyCM-β-CD)/polyetherimide (PEI) multilayer	Ofloxacin	Adjustment of pH	Controllable release in different media	[56]
Poly(methacrylic acid) (PMAA) multilayer hydrogel cubes	7-(benzylamino)-3,4-dihydro-pyrrolo[4,3,2-de]quinolin-8(1H)-one	Redox-triggered release	Long-term storage, combination of well-regulated drug release and shape-modulated drug delivery	[57]