Table 4.

Sol-gel silica-based oral delivery NPs (adapted and reproduced with permission from [102]).

Oral Delivery System	Silica Source	Payload	Coating	Encapsulation Method	Release Mechanism	In Vitro/In Vivo/Ex Vivo	Ref.
Non-porous SiO2 NPs
Stober NPs	TEOS	Insulin	PEG 6000PEG 20,000	Physisorption of insulin to as-synthesized SiO2 NPs–subsequent PEG coating	Passive diffusion	Ex vivo permeation studies with everted rat intestine	[103]
Stober NPs	TEOS	Insulin	Chitosan	Physisorption of insulin in chitosan suspension to as-synthesized SiO2 NPs	Passive diffusion	In vitro studies of NPs interactions with porcine mucin	[104]
Mesoporous SiO2 NPs
MCM-48	Luox AS40	Ibuprofen		Physisorption by immersion	Passive diffusion	In vitro drug release in a simulated body fluid (pH 7.4–7.7)	[105]
Ia3d MSM	TEOS/MPTS	Erythromycin
SBA-15 SiO2	nf	Itraconazole		Physisorption by immersion	Passive diffusion	In vitro drug release in a simulated gastric fluid (pH 1.2)	[106]
SBA-15 and MCM-41 functionalized with –NH2 groups	nf		Bisphosphonates	Electrostatic interaction between drug’s phosphate group and silica’s amnine group at pH 4.8	Passive diffusion t pH 7.4	In vitro drug release in phosphate buffer (pH 7.4)	[107]
MCM41 microparticles	TEOS/tri-ethanolamine	Folic acid		Impregnation	pH triggered	Yoghurt in vitro drug release in a simulated GIT fluid (pH 2, 4, 7.5)	[108]
MCM41 NPs	nf	Rhodamine B	a-CD, adamantly ester	Physisorption	Porcine liver esterase triggered	In vitro hydrolysis in HEPES buffer pH 7.5	[109]
MCM48	TEOS/APTES	Silfalazine	Succinylated soy protein isolate	Physisorption and coating	pH/enzyme triggered	In vitro drug release in simulated GIT fluid at pH 1.2, 5, 7.4	[110]
Hybrid silica microparticles
Core-shell (mesostructured SiO2)	TMOS	Curcumin		1. Encapsulation of curcumin in SLN by emulsification/sonication 2. sol-gel	Passive diffusion	In vitro drug release in a simulated GIT fluid (pH 1.2–7.4)	[111]
Core-shell alginate SiO2	TMOS/APTMS	LGG		1. Preparation of LGG/alginate microgels by electrospraying 2. mineralization	Erosion of silica shell	In vitro drug release in a simulated GIT fluid (pH 1.2–7.4)	[111]
Diatoms silica microparticles
Diatom silica	fossile	Indomethacin/gentamicin		Physisorption	Passive diffusion	In vitro drug release in a simulated intestinal fluid (pH 7.2)	[112]
Diatom silica	fossile	Mesalamine/prednisone		Physisorption	Passive diffusion	In vitro drug release in a simulated GIT fluid (pH 1.2–7.4)	[97]