Table 2. Categories of pH responsive nanoparticles with example materials and applications for oral drug delivery.

	Materials	Delivery site	Model drug and ref.
Polyanions	Eudragits-based	Colon	Budesonide (Makhlof et al., 2009), Sulfasalazine (Kankala et al., 2015), curcumin-celecoxib (Gugulothu et al., 2014)
		Small intestine	CGP 57813 (Leroux et al., 1995), CGP 70726 (De Jaeghere et al., 2000), RR01 (De Jaeghere et al., 2001), cyclosporine A (CyA) (Dai et al., 2004)
	HPMCP	Small intestine	Insulin (Cui et al., 2007)
Polycations	Chitosan-based	Small intestine	Insulin (Rekha & Sharma, 2009, 2015; Cui et al., 2009)
The mixture of polyanions  and polycations	Chitosan + Eudragit	Small intestine, colon	Insulin (Li et al., 2006, 2007; Jelvehgari et al., 2010; Chen et al., 2016), DNA (Momenzadeh et al., 2015), Psoralidin (Yin et al., 2016), Fluconazole (Rencber et al., 2016), CyA (Dai et al., 2015)
	Chitosan + poly(g-glutamic acid)	Small intestine	Insulin (Sonaje et al., 2010c), Amoxicillin (Chang et al., 2010)
	Chitosan + alginate	Small intestine	Bovine serum albumin (Chen et al., 2004b), Insulin (Mukhopadhyay et al., 2015)
	Chitosan + polyaspartic acid	Small intestine	5-fluorouracil (Zheng et al., 2007)
	Chitosan + poly (L-glutamic acid)	Small intestine	Doxorubicin (Deng et al., 2015)
	Chitosan + HPMCP	in vitro	Hepatitis B surface antigen(HBsAg) (Farhadian et al., 2015), Low-molecular weight heparin (Fan et al., 2016)
Inorganic materials	Nano-PSi + chitosan	Small intestine	GLP-1 co-loaded DPP4 inhibitor [No1]
	Nano-PSi + Eudragit	Small intestine	Fenofibrate (Jia et al., 2011), sorafenib (Wang et al., 2011), GLP-1 (Qu et al., 2012), Griseofulvin (Roine et al., 2015)
	Mesoporous silica nanoparticles (MSN)-based	Small intestine	Sulfasalazine (Lee et al., 2008a), Insulin (Guha et al., 2016)
	Calcium phosphate + chitosan + sodium alginate	Small intestine	Insulin (Verma et al., 2016)
Others	Polyacrylamide-grafted-xanthan gum (PAAm-g-XG)	Colon	Curcumin (Mutalik et al., 2016)