Overview of activatable cell-penetrating peptides (ACPPs) triggered through conjugation. Amino acids are indicated via the single letter code, in which d-amino acids are noted in lower case. FITC = fluorescein; GFP = green fluorescent protein; HSA = human serum albumin; QD = quantum dots; BRD-4 = bromodomain-containing protein 4; CASP-3 = caspase 3; BSA = bovine serum albumin; Ab = Alexa Fluor 488 goat anti-rabbit IgG; MSN = mesoporous silica nanoparticle; DP = degree of polymerization.

	Premise	CPP	Cargo	Ref.
Fusion of two subunits
1		R8	FITC	71
2		R8	FITC GFP	72
3		R8	FITC HSA	75
Polymerization
4		Poly Arg side chains	FITC or Tamra	76
			FITC	83
			DOX, avidin, BRD-4, CASP-3, BSA, Ab	78
			BSA, IgG	79
			QD	80
			MSNs	81
5		GSGSG	KLAK	82
		KLAK
		DP > 5