As advantaged nanoscale fluorescent bioprobes, quantum dot (QD) bioconjugates have been widely used in biomedical research. However, the stability of these bioconjugates stored over a period of time has been rarely reported. Here, we synthesised water-soluble QDs by conjugating the human epidermal growth factor (EGF) to these low-cost QDs using 1-ethyl-3(3-dimethylamino propyl)-carbodiimide (EDC) as a cross-linking reagent. These bioconjugates nanomaterials were then used to label cancer cells (MDA-MB-435S and SMMC-7721) and normal cells (HL-7702) whose surfaces expressed high-level (for the cancer cells) and low-level (for the normal cells) EGF receptors (EGFR). We found that although the fluorescence intensity of these bioconjugates decreased with prolonged storage time at 4°C for more than 4 months, their aqueous solution retained a transparent appearance, good particle dispersion and very bright fluorescence. Furthermore, the bioconjugates could still well recognise cancer cells. As a control, the normal cells were labelled with a small amount of the fresh and stored bioconjugates. The results presented in this work indicated that QD bioconjugates prepared with QDs synthesised in aqueous solution may be used as a low-cost biomedical test kit for biomedical imaging and diagnosis, where the QD bioconjugates could be stored for long periods of time.