18 - Stimuli-responsive metal nanoclusters for targeted drug and gene delivery and their biomedical applications

Abstract

The delivery of drugs and nucleic acid molecules to desired target sites using efficient and biocompatible materials has been a challenge to researchers worldwide. Complications of ineffective delivery of such molecules include limitations in the design of the delivery systems, uncontrolled release, poor bioavailability, poor solubility and absorption, in vivo instability side effects due to nonspecific delivery, etc. To address these issues, stimulus-responsive nano-sized carrier molecules have been designed and customized as delivery systems that can overcome the abovementioned drawbacks. Stimulus-responsive nanoparticles can respond to endogenous and exogenous stimuli such as pH, temperature, light, ultrasound, etc. which can effectively stimulate drug or biomolecule release. A major advantage of stimuli-responsive drug-delivery mechanism is the prevention of premature drug release, which has been a challenge for conventional drug delivery systems (DDSs). A major shift in research patterns has been observed toward stimulus-responsive DDSs, which are more effective at targeting and regulating drug release at the site of tumor at the required time and dose. Amongst various types of available nanocarriers (NCs), metal nanoclusters have greatly reduced complications associated with delivery systems owing to their optical, thermal, and magnetic properties. The physical, as well as surface properties of metal nanoclusters, can be easily manipulated for the encapsulation of the drug as well as the gene for efficient delivery. Hence, metal nanoclusters form an ideal delivery system that can also be regulated by an external stimulus, for example, external magnetic field, magnetic hyperthermia, IR (Infrared) heating, etc. For such unique properties, these nanoclusters can carry a broad range of substances to specific target sites and perform a sustained release. The use of these metal nanomaterials in medicine has immensely contributed to the development of various biomedical applications, such as sensing, biomedical imaging, and diagnosis. In this chapter, endostimuli and exostimuli, along with dual and multistimuli responsive metal NCs for drug and gene delivery, bioimaging, and various other biomedical applications are briefly described.