Medronic acid

Medronic acid (Methylenediphosphonic acid) is a methylene-substituted bisphosphonate. Medronic acid has an affinity for the surface of hydroxyapatite crystals in the bone matrix and adheres to them. Medronic acid can be used in complex with radioisotopes in bone imaging. Due to its strong metal chelating ability, medronic acid is also used as a water treatment chemical. In addition, medronic acid is used as a solvent additive to improve peak shape and signal of metal-sensitive metabolites in LC/MS analysis^[1][2]. In Vitro:Preparation of standard solutions and spike solutions for the detection of intracellular purine and pyrimidine-related derivatives by liquid chromatography-tandem mass spectrometry^[2]:
1. Prepare stock solutions of target analytes in 50% methanol at a concentration of 1 mg/mL for each stock solution.
2. To obtain a mixed working solution containing 31 analytes at a concentration of 10 μg/mL, dilute the stock solutions with 80% acetonitrile.
3. For internal standard preparation, prepare stock solutions of each standard in 50% methanol at a concentration of 0.5 mg/mL for each standard. An internal standard mixture containing ¹³C₅-inosine, ¹³C₅-cAMP, ¹³C₁₀, ¹⁵N₅-ATP, ¹³C₉, ¹⁵N₃-CTP, ¹³C₁₀, ¹⁵N₅-GTP, and ¹³C₉, ¹⁵N₂-UTP was diluted in 80% acetonitrile to give a final concentration of 50 ng/mL.
4. Prepare two additives, medronic acid and ammonium phosphate, with water, each at a concentration of 100 mM.
5. All solutions were stored at −20°C before use.


Detection of intracellular purine and pyrimidine-related derivatives by liquid chromatography-tandem mass spectrometry^[2]:
1. Add 500 μL of methanol to the collected cell microspheres to be tested, sonicate for 5 min to lyse the cells, and incubate on ice for 5 min.
2. After protein precipitation, add 500 μL of water to the methanol extract, sonicate for 5 min, and incubate on ice for 5 min.
3. After extraction, centrifuge the sample at 15,000 rcf for 5 min at 4°C.
4. Collect all supernatant into another centrifuge tube and evaporate using a centrifugal evaporator.
5. Reconstitute the residue with 500 μL of 80% acetonitrile and filter through a 0.2 μm PP membrane filter.
6. After filtration, add 10 μL of internal standard mix and 10 μL of 5 mM medronic acid to 80 μL of sample solution to reach a final concentration of 0.5 mM medronic acid before analysis. In parallel, prepare a pooled QC sample to monitor system stability during analysis.
7. All samples were stored at −20 °C prior to LC-MS/MS analysis.