Evaluation of the subcutaneous administration route for human serum albumin nanoparticles in mice

Introduction. One of our group's current efforts is to effectively target the DNA methylome of the atherosclerotic lesion. Part of our strategy is to employ macrophage-targeted human serum albumin (HSA) nanoparticles (HSA-NPs)... [ view full abstract ]

Introduction. One of our group's current efforts is to effectively target the DNA methylome of the atherosclerotic lesion. Part of our strategy is to employ macrophage-targeted human serum albumin (HSA) nanoparticles (HSA-NPs) as carriers for epigenetic modifiers. Lateral tail vein injection is traditionally used to deliver drugs to the vascular system, yet it poses practical and ethical challenges when repeated administrations are performed in dark-skinned C57BL/6 mice. Here, we evaluate the subcutaneous (s.c.) route as an alternative. To our knowledge, similar studies have been conducted for HSA-conjugated drugs and oxidation-stressed (aggregated) HSA, but not HSA-NPs per se.

Methods. HSA-NP physico-chemical properties (size, Z-potential) were determined by standard methods. ApoE-null mice (n=3) received one s.c. injection of 150 μg HSA-NP in 150 μl PBS. Peripheral blood was obtained by tail tip bleeding immediately before injection (time 0) and at 4, 8, 24 and 48 h post-injection (h.p.i.). The presence of HSA-NPs in peripheral blood was assessed by dot-blot or Western blotting with a specific anti-HSA monoclonal antibody.

Results and Discussion. HSA-NP size ranged 162-724 nm. Their Z-potential was -35.9 mV at pH 9, and remained negative in the 5-9 pH range. Following s.c. administration, HSA was present in peripheral blood and showed a significant h.p.i.-dependent increase (p=4x10^-5). We speculated that the latter effect might have been due to time-dependent increase of endogenous serum albumin expression, particularly since the extent of antibody cross reactivity was unknown. Yet, no concomitant change in peripheral blood 60-80 kDa protein expression was observed using the same antibody, thus ruling out the occurrence of such an artifact. By comparison with a HSA standard reference, we estimate that ~20% of the injected HSA-NPs is recovered in the bloodstream at 48 h.p.i. The s.c. route is therefore practical and effective to deliver HSA-NPs to the vascular tissue.