Zinc imidazolate framework-8 as a promising nitric oxide carrier

Uncontrollable release and unexpected release limit the use of nitric oxide (NO). To overcome this problem, we introduce ZIF-8 as a pH-responsive NO carrier. The flexible framework of ZIF-8 under the high-pressure condition causes the physically NO adsorption inside the SOD cage. ZIF-8 maintain the excellent gas storage ability under the physiological environment. The results show good pH-responsive ability. The gas could not be released out until the particle is in an acid condition. At low pH conditions, half of the gas is released in 1% of the total release duration. Interestingly, the half-release (t_1/2) increases to 10% when the phosphate species exist in the acid surrounding. The gradual release can occur under neutral conditions with the existence of phosphate (t_1/2 33%). From these results, we expect this ZIF-8 loading NO nanoparticles is lead to the design of innovative gas therapeutic delivery platforms using the advantage of the flexible framework for loading and releasing the gas molecule.