Comparison of the accumulation manner of a macromolecular drug between two mouse tumour models: study with magnetic resonance imaging and the model macromolecular drug, gadolinium-conjugated dextran.

A knowledge of the difference of spatio-temporal behaviour of nanomedicine in different type of tumour models is important to develop well-targeted nanomedicine for tumour. In this study, intratumoral accumulation of the model nanomedicine, gadolinium-conjugated dextran (Gd-Dex), was examined with magnetic resonance imaging in two tumour models; mouse sarcoma S180 and radiation-induced mouse fibrosarcoma RIF-1. From time-course of the distribution images, the plasma-to-tumour interstitial tissue transfer constant (K^trans) and fractional plasma volume (V_p) were calculated and mapped. Gd-Dex preferentially distributed to the marginal region of S180 tumours immediately after its injection, and then started to accumulate in some parts of the central region. K^trans and V_p values were large in the marginal region, while only K^trans was large in some parts of the central region. In contrast, the distribution of Gd-Dex in RIF-1 tumours was fairly homogeneous, and may have resulted from the homogeneous distributions of K^trans and V_p. The amounts of Gd-Dex that accumulated in entire tumours in both tumour models correlated with the volume of tumours; however, accumulation in large S180 tumours deviated from the correlation in the early phase. The differences in the manner and pharmacokinetics of nanomedicine among tumour models may affect the accumulation of the medicine.