Nanotechnology has played a tremendous role in molecular imaging and cancer therapy. Over the last decade, scientists have worked exceptionally to translate nanomedicine into clinical practice. However, although several nanoparticle-based drugs are now clinically available, there is still a vast difference between preclinical products and clinically approved drugs. An efficient translation of preclinical results to clinical settings requires several critical studies, including a detailed, highly sensitive, pharmacokinetics and biodistribution study, and selective and efficient drug delivery to the target organ or tissue. In this context, technetium-99m (99mTc)-based radiolabeling of nanoparticles allows easy, economical, non-invasive, and whole-body in vivo tracking by the sensitive clinical imaging technique single-photon emission computed tomography (SPECT). Hence, a critical analysis of the radiolabeling strategies of potential drug delivery and therapeutic systems used to monitor results and therapeutic outcomes at the preclinical and clinical levels remains indispensable to provide maximum benefit to the patient. This review discusses up-to-date 99mTc radiolabeling strategies of a variety of important inorganic and organic nanoparticles and their application to preclinical imaging studies.

In this study a comprehensive investigation of doping of sol-gel silica with efficient metal chelating agents is provided at room temperature using infrared spectroscopy, elemental analysis, SEM, EDS and XRD. Sol-gel silica was doped with a series of metal chelating agents to investigate the sorption of Ni (II) ions from aqueous media. It is observed that the chelating agents are encapsulated by the pores of the xerogel from where they interact with the metal ions by ion exchange and chelation mechanism. Nickel complexes of the chelating agents were also synthesized. Sol-gel silica was doped with metal complexes for comparison with sol-gel silica having sorbed metal ions. Same amount of Ni (II) was observed in both samples, showing high efficiency of the method for removal of Ni (II). The batch adsorption experiments were performed at room temperature and neutral pH. The advantage of the method is high sorption capacity at room temperature and neutral pH. The developed method can be applied on large scale removal of toxic heavy metals. The sorption process completed within a minute. 0.1 N HNO3 resulted in complete desorption of metal ions from the gels. The regenerated sorbents were reused several times with negligible loss of sorption capacity.