Why have you closed up "multicell" but not "single-cell"?
AAS journals close up dependent prefixes (non-, ultra-, sub-, super-, multi-, etc.). Multi- is a dependent prefix (you cannot say "the cell is multi"), and so is closed up. But "single" is not a dependent prefix; it is normal adjective (you can say "the cell is single"), and so the proper form is a hyphenated compound adjective, single-cell.