Provided is a hollow particle aggregate formed by aggregating a plurality of self-organizable particles, wherein a metal core is modified by a surface modifier for a metal core comprising a first segment comprising an optionally branched fluorinated alkylene glycol group, an optionally branched fluorinated alkylene group, or an optionally branched fluorinated azaalkylene group; a second segment comprising at least one hydrophilic group and bonding to one of the ends of a main chain of the first segment; and a functional group that bonds directly or indirectly to the another end of the main chain of the first segment and is able to bond to the metal core.