Development and validation of a LC-MS/MS method for quantitation of recombinant human growth hormone in rat plasma and application to a pharmacokinetic study

A UOx@HMnO2 biozyme-nanozyme driven electrochemical platform for specific uric acid bioassays

Uric acid (UA) is a key end product of purine metabolism in the human body, and its abnormal levels are associated with many diseases, so accurate monitoring is essential. Existing detection methods have many limitations. For example, chromatography is cumbersome, time-consuming, and not cost-effective, while serum uric acid analysis requires specialized equipment and venous blood collection. In the field of uric acid sensors, electrochemical detection is commonly used but prone to interference, and nanomaterials offer improvements but are complicated to modify. To better block interference via an easily-made nanocomposite-based system, in this study, MnO2 with peroxidase-mimicking activity was used as a protective shell to encapsulate natural uric acid oxidase (UOx), realizing a good combination of nanozymes and biocatalysts. UOx can selectively catalyze UA and generate H2O2, and the MnO2 nanozymes can make up for the insufficiency of UOx, and the two main components synergistically enhance the activity of UOx@HMnO2, resulting in ultra-high performance. This provides a simple and general method for the preparation of efficient hybridized biocatalysts in the fields of biosensors and biocatalysis. The detection limit of the fabricated uric acid sensor is as low as 0.74 μM, and the concentration of the actual sample is consistent with that of mass spectrometry, which provides a means of non-invasive detection of uric acid with high sensitivity, high specificity and good accuracy.

Quantification of serum daratumumab in multiple myeloma patients by LC-MS/MS, comparison with ELISA

Daratumumab is a fully human immunoglobulin G1 monoclonal antibody employed for treating relapsed/refractory multiple myeloma and light-chain amyloidosis. Quantifying monoclonal antibodies in serum presents challenges due to interference from biological matrices. This research aimed to develop and verify an liquid chromatography tandem-mass spectrometry (LC-MS/MS) approach for quantifying serum daratumumab, employing immunoglobulin G purification without alkylation, and to assess its applicability in patients with multiple myeloma receiving intravenous daratumumab. The chromatographic peaks of the daratumumab-derived peptides and internal standard were well-delineated from the serum digests, with an overall run time of 14 min. The calibration curves for serum daratumumab were linear across over 1-1000 μg/mL. The inter- and intra-day accuracy varied between 92.4 % and 108.4 %, with a coefficient-of-variation below 10 %. In patients receiving intravenous daratumumab, serum concentrations ranged from 181.8 to 975.3 µg/mL. Bland-Altman analysis revealed no significant bias, and Passing-Bablok regression demonstrated a good agreement between the LC-MS/MS method and enzyme-linked immunosorbent assay.

A validated LC-MS/MS method for the quantitation of daratumumab in rat serum using rapid tryptic digestion without IgG purification and reduction

Daratumumab, a humanized monoclonal antibody utilized in treating immunoglobulin light-chain amyloidosis and relapsed/refractory multiple myeloma, was quantified in rat serum through a simple, economical and effective liquid chromatography tandem-mass spectrometry (LC-MS/MS) method. A surrogate peptide, LLIYDASNR, derived from trypsin hydrolysis, was quantitatively analyzed with LLIYDASN [13C6, 15N4] RAT as an internal standard. This corrected variations from sample pretreatment and mass spectrometry response, involving denaturation and trypsin hydrolysis in a two-step process lasting approximately 1 hour. Methodological validation demonstrated a linear range of 1 µg/mL to 1000 µg/mL in rat serum. Precision, accuracy, matrix effect, sensitivity, stability, selectivity, carryover, and interference met acceptance criteria. The validated LC-MS/MS approach was successfully applied to a pharmacokinetic study of daratumumab in rats at an intravenous dose of 15 mg/kg.