The use of italics or quotation marks for titles in the body of your text depends on the type of work you are referring to and follows the same rule that applies for footnotes/bibliography, i.e. italics for the larger/parent work (e.g. book or journal) and quotation marks for smaller works (e.g. book chapters, journal articles etc).
Section 8.163 of the Chicago Manual of Style Online explains this rule (see link below).
