Human serum albumin macroaggregates (MAA) (MAA)

Human serum albumin macroaggregates (MAA) are large, insoluble protein particles produced by the controlled heat denaturation and aggregation of human serum albumin (HSA) [8, 16]. These particles typically range in size from 10 to 90 micrometers, a dimension specifically designed to facilitate mechanical entrapment within the pulmonary capillary bed upon intravenous administration [1, 3]. This physical filtration mechanism allows MAA to serve as a primary diagnostic agent for lung perfusion scintigraphy, most notably when radiolabeled with Technetium-99m (Tc-99m) [7, 8]. The surface amino acid residues of the macroaggregates, including lysine, tyrosine, and cysteine, act as the chemical sites for the chelation and binding of various radioisotopes like Tc-99m and Gallium-68 [8, 9, 16]. Clinically, MAA is utilized to diagnose pulmonary embolism, evaluate right-to-left cardiac shunts, and perform pre-therapeutic planning for Selective Internal Radiation Therapy (SIRT) in patients with hepatocellular carcinoma [11, 12]. Although it is a critical tool in nuclear medicine, MAA is not a biological target for therapeutic drugs but rather a diagnostic vehicle that targets the lung vasculature through passive mechanical entrapment [1, 3].

Other names

Macroaggregated albuminAggregated human albuminTechnetium Tc-99m albumin aggregatedHSA-MAA

Passive lung targeting via mechanical entrapment in pulmonary capillaries based on particle size (10–90 μm).