Synthesis and post-preparative modification of GNB: (a) previous synthetic approach to first generation GNB particles from octanethiol coated AuNP with a final gold loading c.a. 2 w/v%: (i) gold nanoparticles suspended in vegetable oil, (ii) preparation of phospholipids thin film, (iii) microfluidization of gold nanoparticle-vegetable oil with surfactants in water; (b) new strategy to increase final gold loading up to 10 w/v%: oleate coated gold nanoparticles were suspended in sorbitan sesquioleate and microfluidized with phospholipids thin film mixture as a 2-0-20 formulation. reaction condition: (i) gold nanoparticles suspended in polysorbate, (ii) preparation of phospholipids thin film, (iii) microfluidization of gold nanoparticle-polysorbate with surfactants in water; 20,000 psi (141 MPa), 4°C, 4 min; (d) schematic representation of the procedure to concentrate GNB2 prior to spectral CT imaging.