Table 2. In vitro cytoxicity of Tet-loaded nanoparticles and free Tet.

Cell lines	Formulation	IC50 (µM)
		pH 7.4	pH 6.8
BGC-823	Free Tet	7.84±2.41	13.24±1.70*
	Tet-NPs	7.09±0.43	8.15±0.88#
MKN-28	Free Tet	7.66±2.07	11.71±0.87*
	Tet-NPs	6.57±0.60	3.90±1.42* #
Lovo	Free Tet	4.67±0.76	6.81±0.89*
	Tet-NPs	12.35±2.64#	3.05±0.53* #
HepG2	Free Tet	8.64±1.95	12.51±1.97*
	Tet-NPs	3.76±0.17#	4.12±0.50#
H22	Free Tet	8.82±0.80	14.68±3.39*
	Tet-NPs	15.69±0.43#	7.80±1.41* #

Data represent mean value±SD, n = 3.

*P<0.05, pH 6.8 vs pH 7.4 for the same formulation (Free Tet or Tet-NPs respectively).

^#P<0.05,Tet-NPs vs Free Tet for the same pH value (pH 6.8 or pH 7.4).

It can be noticed from the table that when the extracellular pH decreased from 7.4 to 6.8, the cytotoxicity of free Tet in all the tumor cell lines attenuated (which was evaluated by increase of IC50 values, P<0.05). On contrary, the IC50 of Tet-NPs in none of the cell lines increased significantly.

Furthermore, at pH 6.8, the cytotoxicity of Tet-NPs in all the cell lines was more prominent than free Tet (P<0.05).