Recently, these methods have been successfully demonstrated to be useful for the detection of tumors (Prendergast and Patel, 2000, Ebrahimi et al., 2013). An emerging nanomaterial-based fluorescent probe for cancer imaging is quantum dot (QDs) (Ebrahimi et al., 2013, Mairal et al., 2008), which could revolutionize the area of optical contrast agent development and their applications in bio-imaging (Birch and Racher, 2006). The unique optical characteristics of QDs such as large molar extinction coefficients, size dependent tunable emission, high quantum yields and high photo-stability make them appealing as fluorescent probes for biological imaging. These properties that enable QDs to compete with conventional fluorescent dyes for many applications (Ferreira and Missailidis, 2007). However, imaging with unconjugated QDs is challenging owing to the lack of sensitivity and selectivity. QD is covalently linked with bio-recognition molecules such as antibodies, nucleic acids and peptides for use as fluorescent probes (Jayasena, 1999, Ireson and Kelland, 2006). The results show that conjugated QD is similar in size to fluorescent proteins and is also improved in terms of kinetic parameters upon conjugation events (Jayasena, 1999). The surface modification of QDs with aptamers, peptides, antibodies or small molecules that are able to bind to antigens present on the target cells or tissues has resulted in the development of sensitive and specific targeted imaging and diagnostic modalities for in-vitro and in-vivo applications.