Engineering Ultrasmall Metal Nanoclusters as Promising Theranostic Agents

Abstract

Metal nanoclusters (NCs) are promising theranostic agents in biomedicine and their physicochemical properties dictate the extent of their theranostic capability. Key factors that determine the metal NC capability in cancer therapies include: (i) their ability to emit electrons and generate reactive oxygen species; (ii) biocompatibility, targeting, and drug loading capability; (iii) tumor targeting and renal clearance; and (iv) strong luminescence (originating from their unique electronic structures) for bioimaging probes in imaging-guided treatment. Recent advances in cluster chemistry has made possible atomic-level control of the size, structure, composition, and surface functionalization of metal nanoclusters, further paving their ways toward promising theranostic agents in biomedicine. Metal nanoclusters (NCs) are ultrasmall nanoparticles with intriguing molecule-like physicochemical properties. In recent years, metal NCs have been used as theranostic agents in biomedicine. In this short review, we correlate the physicochemical properties of metal NCs to their biomedical applications, shedding some light on the design of metal NC-based theranostic agents in cancer therapy, imaging-guided therapy, antimicrobial agents, and bioimaging. Such design principles could be readily realized in atomically precise metal NCs, leveraging recent advances in synthetic chemistry and the structural resolution of metal NCs. Metal nanoclusters (NCs) are ultrasmall nanoparticles with intriguing molecule-like physicochemical properties. In recent years, metal NCs have been used as theranostic agents in biomedicine. In this short review, we correlate the physicochemical properties of metal NCs to their biomedical applications, shedding some light on the design of metal NC-based theranostic agents in cancer therapy, imaging-guided therapy, antimicrobial agents, and bioimaging. Such design principles could be readily realized in atomically precise metal NCs, leveraging recent advances in synthetic chemistry and the structural resolution of metal NCs. photoemission that will be significantly enhanced through aggregation. Controlling the aggregation of the metal(I)-thiolate complexes on the surface of the metal core of nanoclusters could lead to the formation of strong luminescent metal nanoclusters. solid tumors contain blood vessels with defective architecture to exhibit enhanced vascular permeability, which will favor supply of nutrients and oxygen for rapid growth of tumor tissues. Therefore, molecules could easily transport across the tumor blood vessels and accumulate for a prolonged time without elimination. involves photosensitizer and light of a specific wavelength to activate the sensitizer. The photosensitizer can transfer energy from light to molecular oxygen to generate reactive oxygen species, leading to direct tumor cell killing, vascular damage, and immune response to achieve cancer treatment. the photosensitizers (e.g., organic molecules and metal-contained species) that can be activated under a specific wavelength of light to generate reactive oxygen species. treatment of cancer cells using high-energy ionizing radiation, such as X-rays and γ-rays, to deposit energy to damage the genetic materials of cells, diminishing the proliferation of cells. Metals with large atomic numbers, such as gold (Z=79) and platinum (Z=78), can efficiently absorb ionizing radiations to generate secondary radiations, leading to amplified local radiation exposure to effectively kill cancer cells. radiosensitizers that can enhance the radiotherapy effects of the radiation, such as chemical radiosensitizers and metal-contained radiosensitizers (e.g., gold, platinum, gadolinium, and silver). a pharmacokinetics measurement of the excretion of drug into the urine by the kidneys, which is the net result of three interrelated processes: glomerular filtration, tubular secretion, and tubular reabsorption. involves sonosensitizer and low-intensity ultrasound to activate the sensitizer, leading to reactive oxygen species generation to kill tumor cells. theranostics is the combination of diagnosis and therapy in one system, which, with imaging, can achieve cancer therapy. The agents that are used in such imaging-guided therapeutic systems are normally referred as theranostic agents.