Investigation of the proinflammatory potential of biodegradable nanoparticle drug delivery systems in the lung

Particulate nanocarriers have been praised for their advantageous drug delivery properties in the lung, such as avoidance of macrophage clearance mechanisms and long residence times. However, instilled non-biodegradable polystyrene nanospheres with small diameters and thus large surface areas have been shown to induce pulmonary inflammation. This study examines the potential of biodegradable polymeric nanoparticles composed of poly(lactic-co-glycolic acid) (PLGA) and the novel PLGA derivative, diethylaminopropylamine polyvinyl alcohol-grafted-poly(lactic-co-glycolic acid) (DEAPA-PVAL-g-PLGA), to provoke inflammatory responses in the murine lung after intratracheal instillation. Lactate dehydrogenase (LDH) release, protein concentration, MIP-2 mRNA induction, and polymorphonucleocyte (PMN) recruitment in the bronchial alveolar lavage fluid (BALF) were used to evaluate an inflammatory response in Balb-C mice. Two sizes of polystyrene (PS) nanospheres (diameters: 75 nm and 220 nm) were included in the study for comparison. All nanoparticle suspensions were instilled at concentrations of 1 microg/microl and 2.5 microg/microl, representative of an estimated "therapeutic dose" and a concentrated "dose" of particles. In all experiments, the 75 nm PS particles exhibited elevated responses for the inflammatory markers investigated. In contrast, biodegradable particles of comparable hydrodynamic diameter showed a significantly lower inflammatory response. The most marked differences were observed in the extent of PMN recruitment. While the 75 nm and 220 nm PS nanospheres exhibited 41 and 74% PMN within the total BALF cell population after 24 h, respectively, PMN recruiting in lungs instilled with both types of biodegradable particles did not exceed values of the negative isotonic glucose control. In conclusion, evidence suggests that biodegradable polymeric nanoparticles designed for pulmonary drug delivery may not induce the same inflammatory response as non-biodegradable polystyrene particles of comparable size.