Table 1 Cell-internalizing aptamers for targeted delivery.

RNA aptamers against PSMA

1) siRNA (non-covalently conjugate siRNA with aptamer via a streptavidin connector [49]; aptamer-siRNA chimeras [17, 18] and bivalent aptamer-siRNA conjugates [77]).

2) Toxin [73] (chemically covalently conjugate toxin with aptamer via SPDP reagent)

3) Nanoparticles and chemotherapeutic agents [62–70] (cargoes such as dextran, docetaxel, Pt(IV) and doxorubicin were encapsulated into aptamer-coated nanoparticles; aptamer-Dox physical conjugates via intercalation interaction)

RNA aptamers against CD4

siRNA [25] (non-covalently assemble pRNA-siRNA chimera with pRNA-aptamer chimera into dimer or trimer)

RNA aptamers against HIV gp120

siRNA [19, 20] (aptamer-siRNA chimeras; non-covalently conjugate siRNA with aptamer via a 'sticky bridge')

RNA aptamers against TN-C

Radionuclide and fluorescent agents (chemically covalently conjugate ^99mTc or fluorescent agents with aptamers)

DNA aptamers against PTK7

1) Doxorubicin [93] (chemically covalently conjugate Dox with aptamer via an acid-labile linkage)

2) Viral capsid [94] (chemically covalently conjugate MS2 viral capsid with aptamer via an oxidative coupling reaction)

DNA aptamers against TfR

Enzyme [74] (chemically covalently conjugate a-L-iduronidase with aptamer via an oxidative coupling reaction)

DNA aptamers against NCL

Liposomes and chemotherapeutic agents [71] (cisplatin was encapsulated into liposomes that was non-covalently coated with aptamers)

DNA aptamers against MUC1

Photodynamic therapy agents [72] (chemically covalently conjugate chlorine e6 with aptamer via EDC chemistry)