Background: Nanostructured material is a solid substance with at least one face is in the range of 1-100 nm. Manipulations in the characteristics and effects of nanostructures can invent new procedures and technologies, as the physical and chemical properties of nanomaterials are noticeably dissimilar from those of a single atom or its bulk phase. This difference in the properties is due to different spatial arrangements and shapes, changes in phase, energetics, electronic structure, chemical reactivity, and catalytic properties of huge, finite systems, and their assemblages. Theranostic involves the study of compounds which associates the modalities of curative and investigative purposes. Objective: The aim of this review was to highlight the possible uses of nanoparticles as therapeutic and diagnostic agents. As is evident by the latest applications of nanoparticles in the development of sensitive biosensors as well as in MRI and drug delivery systems. The most important theranostic application of nanoparticles involves the treatment of cancer. In most of the cases, the late diagnosis of the disease is responsible for increasing the mortality rate. Moreover, the toxic effect of the chemotherapeutic drugs on the normal cells of the body seems to be another major drawback of the treatment. Therefore, theranostics appears to be very helpful and realistic area in the diagnosis and targeted drug delivery of this particular disease. Methods: We systematically searched for research literature using well-framed review questions and presented data in both the text as well as tabular forms for readers' convenience. The present review collected the data from the published reviews as well as original research papers. The manuscripts considered in this article were taken from the databases and search engines comprising NCBI, PubMed, Google scholar, directory of open access journals, ScienceDirect and local library searches. The properties of the selected articles were analyzed, and a rational quantitative and qualitative content were used for the outcome and inference of the study applying a conceptual foundation. Results: Two hundred seventeen papers were included in the review. Most of the papers were from developed countries (163) and the rest from developing countries (54). Seventy four articles dealt with both the diagnostic as well as therapeutic study of nanomaterials, fifty seven manuscripts included only therapeutic approach and twenty seven papers included only diagnostic approach. The rest of the articles included the data on the synthesis and characterization of surface modified nanomaterials which could be applied in this area. Forty five papers dealt with both in vitro and in vitro studies, sixteen manuscripts involved studies on clinical trials, fifty nine articles gave data on the basis of in vitro experiments and twenty seven articles on the basis of in vivo studies only while 2 papers included in situ data. In the manuscripts considered for the review, the data on both the solid tumors as well as cancers were taken. Almost all types of cancers are being studied using nanomaterials but the most studied cancer for therapeutic and diagnostic approach on the basis of literature is breast cancer. Conclusion: By the help of surface modification of the nanomaterials specific targeting properties towards specific molecules and receptors in various types of cells could be achieved. It has been suggested that the delivered drugs require low amount to achieve the synergy between both the drugs delivered to cancer cells and tissues. Moreover, the toxic effect of the chemotherapeutic drugs on the normal cells of the body is another major drawback of the treatment. Upon further improvement and optimization of these nanoparticle-based strategies, it will ultimately lead to the prediction of patient's response towards a specific molecular therapy and it will be helpful to observe their responses to personalized therapy. Therefore, theranostics appears to be very helpful and realistic area in the diagnosis and targeted drug delivery of this particular disease.
