Herein, hyaluronic acid functionalized 3.8 nm NaGdF4 nanodots (named NaGdF4 ND@HAs) have been prepared through conjugation of tryptone capped NaGdF4 nanodots (NaGdF4 ND@tryptone) with hyaluronic acid (HA, a naturally occurring glycosaminoglycan), which can recognize the overexpressed CD44 on cancer cell membranes. The gene discussed is CD44; the disease is cancer.