Sustained release carrier for adenosine triphosphate as signaling molecule

Adenosine triphosphate (ATP) is a molecule with a fascinating variety of intracellular and extracellular biological functions that go far beyond energy metabolism. Due to its limited passive diffusion through biological membranes, controlled release systems may allow to interact with ATP-mediated extracellular processes. In this study, two release systems were explored to evaluate the capacity for either long-term or short-term release: (i) Poly[(rac-lactide)-co-glycolide] (PLGA) implant rods were capable of ATP release over days to weeks, depending on the PLGA molecular weight and end-group capping, but were also associated with partial hydrolytic degradation of ATP to ADP and AMP, but not adenosine. (ii) Thermosensitive methylcellulose hydrogels with a gelation occurring at body temperature allowed combining adjustable loading levels and the capacity for injection, with injection forces less than 50N even for small 27G needles. Finally, a first in vitro study illustrated purinergic-triggered response of primary murine microglia to ATP released from hydrogels, demonstrating the potential relevance for biomedical applications.

Adjuvant Effect of Microencapsulated NOD Ligands Studied in a Human Phagocytic Cell Line

Background

Modern subunit vaccines, which are of high purity compared with traditional vaccines, are often incapable of inducing strong immune responses as necessary to build an immunological memory. The desired level of immune response can be achieved only by codelivering immune-modulating agents along with the antigenic epitopes present in these high-purity formulations. This study aimed to explore the adjuvant effect of nucleotide oligomerization domain (nod) receptor agonists as immunomodulators encapsulated in polymeric microparticles as carriers.

Methods

Microparticles (MP) prepared from poly[(rac-lactide)-co-glycolide] (PLGA) (Mn = 5 kDa, PD = 3.2) by the water-in-oil-in-water (w/o/w) emulsion/solvent evaporation technique were characterized in terms of size, surface morphology, payload and endotoxin content. As NOD agonists, N-acetylmuramyl–L-alanyl–D-isoglutamine (MDP; NOD 2) and γ-d-glutamyl-meso-diaminopimelic acid (iE-DAP; NOD 1) were encapsulated. The immunomodulatory potential of these ligand-loaded MP was evaluated with a human acute monocytic leukemia cell line (THP-1X Blue-CD14 cells).

Results

The MP prepared had a phagocytosable size (<10 μm) with a unimodal size distribution and low endotoxin content (<0.5 EU/mL). A dose-dependent cell activation could be established for MDP-loaded microparticles.

Conclusions

MP with suitable characteristics for phagocytosis can be prepared and loaded with NOD agonists. The capability of these ligand-loaded microparticles to activate monocytes suggests their broader exploration as vaccine carriers.