I wanted to test the effect of enzyme on drug dispersion in tumor tissue, and administrated fluorescent microparticle (1-10uM) under mouse xenograft tumors by intra-tumoral injection.

- tumor size: 100-200mm3, injection volume: 10 to 20 ul, injection site: central or 1/3 depth.

- needle size: 25G nano

But I came across microparticles are leak out of tumor in most cases, assumming needle track, interstital space, injection pressure, and other cryptic factors caused this problem.

Is there any way to improve drug retention during local injection, or anyone knows alternative experimental platform can analyze covering area through tumor tissue than xenograft tumor (organoids, 3D model with ECM component...?) ?