Analysis of verteporfin liposomal formulations for phospholipids and phospholipid degradation products by liquid chromatography-mass spectrometry (LC-MS)

Excipient-related impurities in liposome drug products

Liposomes are widely used in the pharmaceutical industry as drug delivery systems to increase the efficacy and reduce the off-target toxicity of active pharmaceutical ingredients (APIs). The liposomes are more complex drug delivery systems than the traditional dosage forms, and phospholipids and cholesterol are the major structural excipients. These two excipients undergo hydrolysis and/or oxidation during liposome preparation and storage, resulting in lipids hydrolyzed products (LHPs) and cholesterol oxidation products (COPs) in the final liposomal formulations. These excipient-related impurities at elevated concentrations may affect liposome stability and exert biological functions. This review focuses on LHPs and COPs, two major categories of excipient-related impurities in the liposomal formulations, and discusses factors affecting their formation, and analytical methods to determine these excipient-related impurities.

Profiling in-vitro release of verteporfin from VISUDYNE® liposomal formulation and investigating verteporfin binding to human serum albumin

VISUDYNE® is a liposomal formulation of verteporfin, used in the photodynamic therapy of age-related macular degeneration via intravenous administration. In this study, we developed a new in vitro method to quantify verteporfin release from VISUDYNE® under conditions that replicate in vivo conditions using human serum albumin (HSA). Verteporfin release from the liposomes was quantified using capillary electrophoresis (CE) with optical detection. Verteporfin binding to HSA was quantified by measuring HSA fluorescence that is quenched by drugs binding to specific HSA binding sites. The binding constant of verteporfin to HSA was calculated using the Stern Volmer plot and found to be 1.966 × 107 M-1 at 37 °C. Verteporfin binding to HSA involves one albumin binding site and the binding molar ratio between verteporfin and HSA is approximately 1:1. A rapid partitioning of verteporfin from VISUDYNE® onto HSA takes place within 10 min and involves the release of more than 90% of the verteporfin at physiological temperatures. This study verifies this approach of using CE to rapidly separate liposome and HSA-bound drug, thus minimizing drug release artifacts created with other methods.

Effect of oxyresveratrol on the quality and membrane lipid metabolism of shiitake mushroom (Lentinus edodes) during storage

The effect of oxyresveratrol on postharvest quality and membrane lipid metabolism of shiitake mushroom was investigated. The result exhibited that oxyresveratrol retarded browning, maintained firmness and alleviated occurrence of decay of shiitake mushroom. The oxidation and hydrolysis of membrane phospholipids were suppressed by oxyresveratrol treatment, which was associated with reduced LOX and PLD activities and increased SOD and CAT activities. The membrane lipidomics of shiitake mushroom was determined by LC-MS. 385 lipid species and 13 fatty acids in membrane lipids were identified by multiple reaction monitoring method. Compared with control group, the phospholipic acid and lysophospholipid reduced by 29.24% and 21.29% in oxyresveratrol-treated group, respectively, which alleviated hydrolysis of phospholipid. Meanwhile, oxyresveratrol maintained the unsaturation of fatty acids and alleviated oxidation of phospholipid. These results demonstrated that oxyresveratrol could play a dual role of inhibiting the oxidation and hydrolysis of phospholipids to mitigate cellular damage of shiitake mushroom.

Effects of perfluoroalkyl substances on the operational efficiency, microbial communities, and key metabolic pathways of constructed rapid infiltration system with coke as filler layer

Influences of perfluoroalkyl substances on the performance and microbial metabolic pathways of constructed rapid infiltration systems are not fully understood. In this study, wastewater containing different concentrations of perfluorooctanoic acid (PFOA)/perfluorobutyric acid (PFBA) was treated in constructed rapid infiltration systems with coke as filler. The addition of 5 and 10 mg/L PFOA inhibited the removal of chemical oxygen demand (COD) (80.42%, 89.27%), ammonia nitrogen (31.32%, 41.14%), and total phosphorus (TP) (43.30%, 39.34%). Meanwhile, 10 mg/L PFBA inhibited TP removal of the systems. Based on X-ray photoelectron spectroscopy, the percentages of F^- within the PFOA and PFBA groups were 12.91% and 48.46%, respectively. PFOA transformed Proteobacteria (71.79%) into the dominant phyla of the systems, whereas PFBA enriched Actinobacteria (72.51%). The PFBA up-regulated the coding gene of 6-phosphofructokinase by 14.44%, whereas PFOA down-regulated it by 4.76%. These findings provide insights into the toxicity of perfluoroalkyl substances on constructed rapid infiltration systems.

Metagenomic and extracellular polymeric substances analysis reveals the mechanism of exogenous N-hexanoyl-L-homoserine lactone in alleviating the inhibition of perfluorooctanoic acid on anammox process

To alleviate the negative effects of perfluorooctanoic acid (PFOA) on nitrogen removal via anaerobic ammonia oxidation (anammox), an exogenous signaling factor (N-hexanoyl-L-homoserine lactone, C₆-HSL) was introduced into an anammox reactor. Results showed that 2 μmol/L C₆-HSL promoted the nitrogen removal efficiency of the anammox reactor under PFOA stress, with the removal efficiencies of ammonia and nitrite increasing from 79.7 ± 4.8 % and 80.8 ± 3.8 %, to 94.4 ± 4.3 % and 97.1 ± 3.8 %. Exogenous C₆-HSL enhanced the compactness of the extracellular proteins, and improved the sludge hydrophobicity. Meanwhile, C₆-HSL resulted in a microbial shift, with the relative abundance of Planctomycetes increasing from 30.2 % to 49.5 %. Candidatus Kuenenia stuttgartiensis replaced Candidatus Brocadia sp. BL1 as the dominant species, while the available space for other nitrogen-removing bacteria was reduced. Exogenous C₆-HSL promoted the expression of anammox-related genes, such as hzsB and hdh, while denitrifying genes were down-regulated. In addition, the relative abundance of HdtS, which synthesizes AHLs, increased by 0.02446%.

Long-term effect of perfluorooctanoic acid on the anammox system based on metagenomics: Performance, sludge characteristic and microbial community dynamic

The effects of PFOA on the nitrogen removal performance, microbial community and functional genes of anaerobic ammonium oxidation (anammox) sludge in an anaerobic baffled reactor (ABR) were investigated. The removal efficiencies of ammonia nitrogen (NH₄⁺-N) and nitrite (NO₂^--N) decreased from 93.90 ± 3.64% and 98.6 ± 1.84% to 77.81 ± 6.86% and 77.96 ± 1.88% when PFOA increased from 5 mg/L to 50 mg/L, respectively. X-ray photoelectron spectra analysis of the anammox sludge showed the presence of both C-F and CaF₂ forms of F. Metagenomics analysis of the anammox sludge in the first compartment illustrated that the relative abundance of Ca.Brocadia and Ca.Kuenenia decreased from 22.21% and 5.61% to 2.11% and 2.84% at 50 mg/L PFOA compared with that without PFOA. In addition, the nitrogen metabolism pathway showed that adding 50 mg/L PFOA decreased the expression of HzsB, HzsC, and Hdh (anammox genes) by 0.096%, 0.05% and 0.062%, respectively.