Biodistribution and lymph node retention of polysaccharide-based immunostimulating nanocapsules

Area of Science:

• Nanotechnology
• Immunology
• Pharmacokinetics

Background:

• Polysaccharide-based nanocapsules (PG-nanocapsules) show promise as adjuvants.
• Previous studies reported adjuvant properties of PG-nanocapsules with subunit antigens.

Purpose of the Study:

• To investigate the biodistribution and lymph node targeting of PG-nanocapsules after subcutaneous injection.
• To understand the in vivo behavior of PG-nanocapsules for their adjuvant mechanism.

Main Methods:

• Radiolabeling of PG-nanocapsules with indium-111 ((111)In) with high efficiency (98%).
• Assessment of nanocapsule stability in serum post-radiolabeling.
• Subcutaneous injection of radiolabeled nanocapsules and control (111)InCl3 in rabbits.
• Biodistribution analysis using γ-scintigraphy imaging.

Main Results:

• PG-nanocapsules exhibited slow clearance from the injection site, forming a depot.
• Significant accumulation of nanocapsules in the popliteal lymph node over 48 hours (3.8%±1.2 injected dose).
• Nanocapsule clearance was slower than free (111)InCl3, which showed rapid systemic distribution and excretion.

Conclusions:

• PG-nanocapsules preferentially localize within the lymphatic system after subcutaneous administration.
• The formation of an injection site depot and sustained lymph node retention contribute to the observed immune-potentiating effects.
• These findings support the use of PG-nanocapsules as effective vaccine adjuvants due to their lymphatic targeting and prolonged antigen presentation.