Table 3.

Examples of formulations for the controlled release of RA in the context of cancer, brain diseases, skin diseases, immune diseases, stem cell differentiation, among other applications.

Type	Diameter	Loading (μg/mg of carrier)	Delivery	Applications	Ref.
NPs	≃500 nm	≃76	Up to 3 h in the presence of trypsin	Pharmaceutical	94
NPs	<200 nm	154	Release up to 10 days	Cancer	51
NPs	170–230 nm	20	80% cumulative drug release in 4 days	Immune diseases	58
NPs	170–185 nm	275	Sustained drug release observed over 72 h	Cancer	56
NPs	≃200 nm	86	17% cumulative RA release for 21 days	Stem cells and brain diseases	24,44,66
NPs	160 nm	150	50% release after 10 min irradiation	Cancer and brain diseases	25,60
NPs	≃100 nm	68–87	5–100% release of RA in 5 days	Stem cells and brain diseases	45
NPs	≃214 nm	30	38% cumulative release of RA in 48 h	Cancer	120
MPs	≃5.6 μm	80	Pseudo-zero order release for 5 weeks	Pharmaceutical	61
MPs	≃8 μm	3	Release up to 10 days	Stem cells	7
MPs	190 μm	57	Less than 3 h	Cancer	134
Mic	100–500 nm	40–130	NA	Pharmaceutical	48
Mic	100–400 nm	2.6	Parenteral administration; <5% in 3 days	Cancer	63
Mic	50–200 nm	80% (w/w)	1-month delivery	Cancer	47
Lip	NA	NA	4.4 μg/mL blood per day (in humans)	Cancer	49,70,95
EFM	0.95–1.89 μm	5	80% cumulative RA release in 3.5 months	Stem cells	135
EFM	<5 μm	≃10	≃9.0 μM for 1 h	Stem cells	73
Scaffold	NA	≃20	Release over 8–28 h	Regenerative medicine	136
Scaffold	0.1–0.85 μm fibers	≃0.3–7	Sustained release of RA for up to 1 week	Stem cells	137

EFM, electrospun fibrous mesh; h, hour; Lip, liposome; Mic, micelles; MPs, microparticles; NA, not available; NPs, nanoparticles; min, minute.