please answer 2 and 3 if u can

1. Your company received a batch of polystyrene bead, and your supervisor asks you to coat the beads with anti-CD4 antibody (150 KDa). The microbead has a diameter of 1 m. You will use adsorption method to coat the antibody on the beads. From the literature, you identify that the saturated coverage is 2.5mg antibody /m2 of the beads surface based on the Langmuir monolayer model. (a) Determine the number of antibodies per bead at the maximum coverage. (5pts) (b) To achieve the maximum coverage, you will need to mix the beads with 10 -times excess amount of the antibody during the adsorption process (i.e. 10 of the saturated antibody as note above). Given that the density of polystyrene is 1.05g/cm1, determine the amount of antibody you will need to mix with 1mg of beads. ( 5pts) 2. Commercial iron oxide nanoparticle you bought are nicely dispersed in organic solvents such as toluene, but precipitate on addition of water. (c) Howe would you make you nanoparticles stable in aqueous solution? (10 pts) (d) Which strategy could you use to attach an antibody to surface? (You may search literature to identify a suitable method). (10 pts) 3. DNA aptamers are short DNA strands with usually 20 to 80 nucleotides. They bind to target molecules with high affinity and specificity, which stems from their characteristic structure composed of loops and bulges. DNA aptamers can be considered as DNA-based antibody. (a) Describe two methods by which DNA aptamers can be attached to Au nanoparticles using relevant chemical structure? (10 pts) (b) The SARS-CoV2 spike protein is a trimer protein, i.e. consisting three identical units. Your supervisor asks you to design a colorimetric biosensor using spike protein specific DNA aptamer conjugated gold nanoparticle, explain what the principles behind the sensor (hint: try to explain how you can achieve the colorimetric assay? Why the color changes?) (10 pts)