Nanotechnology has revealed possibilities for breakthrough developments in the area of therapeutics. With their wide range of functions and traits, multifunctional nanomaterials offer a potential intriguing direction in the quest for more efficacious and reliable medical interventions. The exquisite engineering of these nanomaterials enables them to function simultaneously in the delivery of drugs, imaging, and diagnostics. Owing to their compact size and high surface-area-to-volume ratio, they can encapsulate and release drugs effectively, boosting therapeutic results while lowering side effects. Additionally, due to their specific physicochemical characteristics, which allow for precise localization across one’s body, they are perfect choices for targeted drug administration. Nanoparticles can be modified with contrast materials for a range of imaging techniques, allowing for real-time evaluation of disease growth and treatment outcomes. These nanomaterials can act as frameworks for incorporating theranostic characteristics, enabling both therapy and diagnosis via a single system. These are also at the cutting edge of customized medicine, delivering specific treatments that take into account a person’s genetic makeup and disease background. Their adaptability enables the creation of patient-specific medicines, enhancing therapeutic results while minimizing negative effects. This study discusses the therapeutic applications of multifunctional nanomaterials while emphasizing their potential to change the paradigm of healthcare by providing more specialized, efficient, and individualized treatment options. <!----> <!----> <!----> <!---->

Drug resistance arises in cancer due to tolerance of tumor cells against drug treatment, genetic mutations, upregulation of drug efflux, and a number of cellular and molecular mechanisms. The available strategies to deal with cancer to date include surgery, chemotherapy, radiotherapy, and combination drug therapy. A number of cancer patients have been cured through these strategies, but complete eradication of this deadly disease is still a dream due to a lack of specificity and higher toxicity. The development of drug resistance poses a formidable challenge in cancer treatment, limiting the efficacy of therapeutic interventions. Nanoparticles-based combination therapy, including various strategies, such as temporal sequencing on drug release, co-encapsulation of drugs having different physicochemical properties, and control over drug loading, can promise a better cancer treatment. Combinatorial nanoparticles-based strategies have opened new insights toward dealing with cancer resistance. A number of such formulations proved successful in reversing drug resistance in numerous in vitro and in vivo cancer models. This chapter is focused on mentioning such strategies to deal with drug resistance in cancer. <!----> <!----> <!----> <!---->