Upconverting nanoparticles: assessing the toxicity

Abstract

Lanthanide doped nanoparticles (Ln:NPs) hold promise as novel luminescent probes for numerous applications in nanobiophotonics. Despite excellent photostability, narrowband photoluminescence, efficient anti-Stokes emission and long luminescence lifetimes, which are needed to meet the requirements of multiplexed and background free detection at prolonged observation times, concern about their toxicity is still an issue for both in vivo and in vitro applications. Similar to other chemicals or pharmaceuticals, the very same properties that are desirable and potentially useful from a biomedical perspective can also give rise to unexpected and hazardous toxicities. In engineered bionanomaterials, the potentially harmful effects may originate not only from their chemical composition but also from their small size. The latter property enables the nanoparticles to bypass the biological barriers, thus allowing deep tissue penetration and the accumulation of the nanoparticles in a number of organs. In addition, nanoparticles are known to possess high surface chemical reactivity as well as a large surface-to-volume ratio, which may seriously affect their biocompatibility. Herein we survey the underlying mechanisms of nanotoxicity and provide an overview on the nanotoxicity of lanthanides and of upconverting nanoparticles.

Revisiting the classification of NIR-absorbing/emitting nanomaterials for in vivo bioapplications

“…As proven by the example of gold colloid, which is probably the best-studied nanomaterial to date, these NPs generally are recognized as benign and safe but some forms, that is, specific sizes or with some coating molecules, can be toxic. 227,228 Similarly, lanthanide-doped NPs are basically considered safe, owing to both their chemical composition and size, 180 but their dissolution may potentially become a problem if toxic Gd 3+ ions are part of their composition.…”

Photoluminescent nanoplatforms in biomedical applications

“…Nonetheless, when working with nano-sized materials, it is important to consider several other physicochemical features that might have a toxic effect, including doping, hydrodynamic size, morphology, size heterogeneity, tendency for aggregation, surface functionalization, surface charge, solubility, and biodegradability [179][180][181][182][183]. A significantly lower number of reports are found that study these aspects in detail.…”

“…Review papers summarizing the studies performed on the toxicity of different photoluminescent nanoparticles have been reported, including gold nanoparticles [193][194][195][196], QDs [197][198][199][200][201], lanthanide-based nanoparticles [179,[202][203][204], and C-dots [205]. However, individual toxicity evaluations need to be completed for each developed nanoplatform to completely assure its safety for biomedical applications.…”

Antibacterial photodynamic therapy: overview of a promising approach to fight antibiotic-resistant bacterial infections

“…Inasmuch as there are no endogenous chromophores that significantly absorb near-infrared light of this wavelength, the optical penetration is sufficient to homogenously irradiate larger bulks of tissue. The drawback of this technique is that another exogenous pharmacological entity (i.e., upconverting nanoparticles) must be co-administered with the PS, which may lead to systemic or local toxicity issues [208].…”