For paraffin section FISH, please recommend a digoxigenin-labeled hybridization kit with low background.

For miRNA FISH on liver and brain paraffin sections, high background is often not a probe issue, but rather liver tissue autofluorescence and residual endogenous proteins. When choosing a kit, first check whether the hybridization solution contains 50% formamide, Denhardt's solution, tRNA, or salmon sperm DNA. The wash buffer should preferably include a gradient of SSC/formamide, not just PBS. Within a budget of 1500, focus on domestic batches whose formulations have been revised in recent years. Ask sales representatives to provide reference images of mouse liver FFPE, and ideally apply for 1-2 trial samples. In-stock domestic kits typically ship in 3-5 days, while imported cold-chain kits commonly take 2-3 weeks. Don't just take "in stock" at face value—confirm whether low-temperature components are included.

If your budget is capped at 1500 and you still want a full set of blocking solution and wash solution, I suggest not insisting on an imported complete kit. You can buy the domestic hybridization buffer as the main component, then pair it with bulk DIG blocking solution and wash solution from Roche or Thermo. In kits, the biggest concerns are antibody shelf life and buffer pH drift. Upon arrival, measure the pH first and run a small-sample test staining. Local same-city distributors can generally compress delivery to 2-4 days, cross-province in-stock cold-chain is 5-7 days, and some imported aliquoted products take 7-14 days. Before ordering, ask clearly whether they accept returns for high background, so that even if the trial performs poorly, you can switch batches without having to buy a large amount upfront.

It is recommended to first perform three control groups: antibody-only, probe-only, and hybridization after RNase digestion. High background in liver tissue is commonly caused by excessive antibody Fab concentration or insufficient blocking time. You can replace the supplied blocking solution with 1% Blocking Reagent plus 5% sheep serum and extend blocking to 1 hour; for washing, use TBS containing 0.1% Tween-20 and raise the temperature to 42-50°C. Proteinase K digestion of paraffin sections is more critical; for mouse liver and brain, it is recommended to start with 5 μg/ml at 37°C for 10 minutes, and do not exceed 15 minutes. Using the probe concentration according to the instructions is fine, but the hybridization temperature can be tested at 47°C instead of 42°C, which can reduce nonspecific spots.