Store a list of file into an array variable, and loop through the list:

files=($(ls -lah yourFolder/* | cut -d' ' -f X)) # X depend on which column is your file name, usually 14 in a local computer, but might differ.
for item in "${files[@]}"
do
  echo $item
done

Or read the list from file then loop:

while read sample;
do
    sample_list="$sample_list $sample"
done < sampleList.txt

for sample in $tissue_list
do
    echo $sample
done

Source:
https://stackoverflow.com/questions/9954680/how-to-store-directory-files-listing-into-an-array