Pepsin and bile salts inhibit gene silencing in a dose-dependent manner. After formulation, LNPs were diluted in pepsin or bile salt solutions and then incubated at 37 °C for 30 minutes. ( a ) LNPs silenced GAPDH less effectively (siRNA dose = 10 nM) with increasing pepsin concentration. Pepsin alone did not affect GAPDH expression (gray bar). A one-way ANOVA indicated significance. ****p