PMC

Spike recovery controls in water (quality control, blue bar), gold nanoparticles (inhibition enhancement control, green bar), PMLA nanoparticles (red bar), PMLA–PEG nanoparticles (purple bar), and in dendrimers (yellow bar). All tested nanoparticles were within USP mandated acceptance criteria for the turbidity limulus amoebocyte lysate assay (thresholds indicated in red). Shown is mean result (n = 6), % coefficient of variation < 25.
PEG: Poly(ethylene glycol); PMLA: Prepharmaceutical β-polymalic acid; USP: US Pharmacopoeia.

(A) Results of end point chromogenic LAL test. Spike recovery control in water (blue bar), in PMLA–PEG nanoparticles (purple bar) and in dendrimers sample (yellow bar) was within the US FDA/USP mandated criteria for chromogenic LAL assay. PMLA nanoparticles (red bar) enhanced, while gold nanoparticles (green bar) inhibited detection of endotoxin. (B) Results of kinetic chromogenic LAL test. When the same dendrimer formulation tested in end point chromogenic assay was studied in the kinetic chromogenic LAL assay, it resulted in enhancement of endotoxin detection. Endotoxin amount in unspiked nanoparticle formulation could not be accurately evaluated for gold and PMLA nanoparticles in end point assay, and for dendrimers in kinetic assay due to failure of the inhibition/enhancement control. Amounts of endotoxin in PMLA–PEG and dendrimer samples as measured in end point chromogenic assay were 0.53 EU/mg/ml and less than 0.1 EU/mg/ml, respectively. Shown is mean result (n = 6), % coefficient of variation < 25.
LAL: Limulus amoebocyte lysate; OD: Optical density; PEG: Poly(ethylene glycol); PMLA: Prepharmaceutical β-polymalic acid; USP: US Pharmacopoeia.