I used Naphtol,fast fed violet LB salt, N,N dimethylfirmamide, 0.1M sodium actate buffer (pH-5). I mixed these for ~30mins. After that, I filtered the soluion with 40um filter. After adding these filtered solution into the well, I found a lot of junks on the cell surface. I tried to filter with filter paper. But, it didn't work either. Do you have any suggestion for this problem? The junk on the cell durface as shown in the attached photo. Thanks in advance.