Gold nanoparticles (AuNPs) have found a wide range of biomedical and environmental monitoring applications (viz. drug delivery, diagnostics, biosensing, bio-imaging, theranostics, and hazardous chemical sensing) due to their excellent optoelectronic and enhanced physico-chemical properties. The modulation of these properties is done by functionalizing them with the synthesized AuNPs with polymers, surfactants, ligands, drugs, proteins, peptides, or oligonucleotides for attaining the target specificity, selectivity and sensitivity for their various applications in diagnostics, prognostics, and therapeutics. This review intends to highlight the contribution of such AuNPs in state-of-the-art ventures of diverse biomedical applications. Therefore, a brief discussion on the synthesis of AuNPs has been summarized prior to comprehensive detailing of their surface modification strategies and the applications. Here in, we have discussed various ways of AuNPs functionalization including thiol, phosphene, amine, polymer and silica mediated passivation strategies. Thereafter, the implications of these passivated AuNPs in sensing, surface-enhanced Raman spectroscopy (SERS), bioimaging, drug delivery, and theranostics have been extensively discussed with the a number of illustrations.

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Each cargo in a cell employs a unique set of motor proteins for its transport. Often multiple types of kinesins are bound to the same cargo. It is puzzling why several types of motors are required for robust transport. To dissect the roles of each type of motor, we developed optogenetic inhibitors of kinesin-1, -2, -3 and dynein. This system allows us to control the activity of the endogenous set of motor proteins that are bound to intracellular cargoes. We examined the effect of optogenetic inhibition of kinesins-1, -2, and -3 and dynein on the transport of early endosomes, late endosomes, and lysosomes. While kinesin-1, kinesin-3, and dynein transport vesicles at all stages of endocytosis, kinesin-2 primarily drives late endosomes and lysosomes. In agreement with previous studies, sustained inhibition of either kinesins or dynein results in reduced motility in both di- rections. However, transient, optogenetic inhibition of kinesin-1 or dynein causes both early and late endosomes to move more processively by relieving competition with opposing motors. In contrast, optogenetic inhibition of kinesin-2 reduces the motility of late endosomes and lysosomes, and inhibition of kinesin-3 reduces the motility of endosomes and lysosomes. These results suggest that the directionality of transport is likely controlled through regulating kinesin-1 and dynein activity. On vesicles transported by several kinesin and dynein motors, motility can be directed by modulating the activity of a single type of motor on the cargo.