What should be paid attention to when designing siRNA?
siRNA design needs to be completed by software, but there are some general rules:

The fragment is ****ween 75-100 nt of the start codon and 100 nt of the stop codon;
The G/C ratio is ****ween 35-50%, it should not exceed 55%;
After sequence design, BLAST homology analysis should be performed.
Note: The choice of RNAi has certain randomness for any target gene.

From https://rna.bocsci.com/support/faqs-of-sirna.html